The aim of the study was to present the possibility of the sensitivity improvement of the electronic nose (e-nose) and to summarize the detection mechanisms of trace gas concentrations. Our main area of interest is graphene, however, for the better understanding of the sensing mechanisms, it is crucial to review other sensors of similar functions. On the basis of our previous research, we explained the detection mechanism which may stay behind the graphene sensor’s sensitivity improvement. We proposed a qualitative interpretation of detection mechanisms in graphene based on the theory regarding the influence of metals and substituents on the electronic systems of carbon rings and heterocyclic aromatic ligands. The analysis of detection mechanisms suggests that an increase of the electronic density in graphene by attaching a substituent and stabilization of electronic charge distribution leads to the increase of graphene sensor conductivity. The complexation of porphyrins with selected metals stabilizes the electronic system and increases the sensitivity and selectivity of porphyrin-based sensors. Our research summary and proposed conclusions allow us to better understand the mechanisms of a radical change of graphene conductivity in the presence of trace amounts of various gases. Molecular mechanisms of detection of trace amounts of gases have been studied for many years. Moreover, different analyses and data interpretation methods have been developed over the past decades. These achievements allowed us to get more detailed insights into the concept of electronic nose (e-nose) which represents a method that is complementary to the commonly used GC-MS technique (gas chromatography combined with mass spectrometry). In contrast to GC-MS, the use of the e-nose does not allow for direct chemical identification of the particular substance, but it can show the final specific response of the sensors to the analyzed substance present in the sample and assign it to a specific group of compounds. Moreover, the e-nose method may allow for the production of small, inexpensive and user-friendly devices that can be used in different areas where gas identification mechanisms play a significant role . An electronic nose is a model of the mammalian olfactory system. According to the Axel and Buck theory , the perception process begins in the olfactory epithelium, where approximately fifty million receptor neurons initially identify and classify volatile molecules . Each ofCurrently, research is focused on applying the e-nose in medical fields, especially in the early diagnosis and prevention of respiratory diseases  using, among others, quartz microbubbles as well as detecting the presence of bacteria in the urine and the eyeball using polymer sensors . The e-nThe development of artificial olfaction methods would not be so dynamic without the implementation of different methods that allow for a detailed analysis of data sets of sensors arrays. Here, we would like to highlight the two most popular and useful methods—principal component analysis (PCA) and cluster analysis (CA). PCA is a dimensionality-reduction method that is often used to reduce the dimensionality of large data sets, by transforming a large set of variables into a smaller one that still contains most of the information from the large set. By applying dimensionality reduction, we trade a little accuracy for simplicity. The reason for this is that smaller data sets are easier to explore and visualize which makes analyzing data much easier and faster for machine learning algorithms without extraneous variables to process. Thanks to PCA analysis, sensors are assayed for their responsibility for the vapors classification. Sensors with loadings ~ 0, for a particular principal component, have a minor contribution to the total response of the array, whereas, high values show discriminating sensors. According to this theory, sensors that have an inconsiderable responsibility for the distribution pattern in the PCA plot are usually removed from the sensor array, because of a negative effect on the pattern resolution. Moreover, sensors with equal loading parameters can be presented by just one sensor . In the The cluster analysis (CA) is a class of methods that are applied to classify objects or cases into relative groups named clusters. CA may be used to the obtained data set. The reaction between different vapors and various reduced graphene oxide (RGO) sensors results in data points that are localized close to each other for similar sensors. Therefore, chemically similar sensors should be classified into one cluster . Figure Development of new analysis methods, improvement of sensitivity and selectivity of detectors as well as the better understanding of sensing mechanisms allow to popularize the use of the e-nose in the industry and medicine.2) significantly improves the sensitivity of the detector and secures an excellent response to NO2 [3 [2 [Carbon nanotubes (CNT) found widespread use as gas sensors due to their electronic properties and large surface area. A significant improvement in the sensitivity and selectivity of CNT-based sensors has been achieved by the formation of various types of hybrids. It was shown that the formation of a CNT hybrid with a metal oxide  signifo NO2 [3 , and H2 O2 [3 [2 . SensorsO2 [3 [2 . An impoO2 [3 [2 .Carboxylated single-wall carbon nanotubes (SWNT-COOH) found application in the detection of amines, ammonia, trimethylamine, and dimethylamine. An increase of the sensor sensitivity based on SWNT-COOH was achieved by forming an SWNT-COOH composite with polymers, such as polyvinyl chloride, polyvinylpyrrolidone, and cumene ending with polystyrene-co-maleic anhydrite ,19. The 0 was defined as ΔR/Ro% = (R − Ro)/Ro * 100, where R stands for the resistance of the device exposed to the analyte and Ro stands for the initial resistance before analyte exposure. It can be noticed that the conductance of bare CNTs decreased significantly upon functionalization with ruthenium complexes with porphyrin. Moreover, the ruthenium complexes with porphyrin-coated CNTs had a more negative threshold gate voltage and lower transconductance when compared to the bare CNTs. These changes are attributed to the n-doping by the electron donor porphyrin of the p-type semiconductor CNT which results in lower carrier (hole) concentration and carrier mobility [Despite the particular physicochemical properties of carbon nanotubes, the low sensitivity to volatile organic compounds is a serious limitation. The increase in the sensitivity of sensors based on carbon nanotubes was achieved by creating a CNT hybrid with porphyrins and metalloporphyrins. The formation of the hybrid is based on the reaction of the porphyrin core with the sidewall of the nanotube ,22,23. Tmobility .A comparison of the sensitivity of CNT-porphyrins hybrids towards acetone, methanol, ethyl acetate, and tetrahydrofurane is presented in A chemiresistor built from a CNT network spanning two metallic electrodes has a current flowing through it when a voltage is applied. In the presence of an analyte, the current flow can be inhibited according to the following effects : modulatThe analysis carried out by Calbi  proved tMechanism of gas detection can rely on changing the material conductivity which is a result of the reaction of the gas molecule with the CNT surface. During the detection analysis of volatile compounds by e-noses, a conductivity measurement between two electrodes is performed. Due to the fact that CNTs are formed almost entirely from surface atoms, a small change in the chemical environment of CNT leads to a measurable change in conductivity. One of the reasons for the change in the sensor’s material conductivity is the change of Schottky’s potential barrier which occurs at the interface of metal and semiconductor at room temperature, i.e., on the electrode connector with CNT. At a higher temperature, e.g., 150 °C, gas molecules are adsorbed on the CNT wall and the charge transfer from the adsorbed gas to the CNTs contributes to the rise in the signal due to a change in conductivity. As a result of gas adsorption, electrons are transferred to the CNT conduction band that leads to a reduction in hole concentration and an increase in conductivity.2 and NH3 was observed [3N4 film. After isolating the CNT-Au connector and sensor exposure to NH3 no response from the CNT channels, even at high gas concentrations (above 500 ppm), was noted. However, after isolation of the CNT channels, the CNT-Au exposed to NH3 was highly sensitive at room temperature. The presented experiment suggests that NH3 induces Schottky barrier modulation which may be the predominant mechanism of NH3 detection by carbon nanotubes at room temperature. At temperatures above 150 °C, NH3 may adsorb to the CNT wall and play a role of an electron donor, whereas the Fermi CNT level moves towards the conduction band and the voltage threshold reaches a lower value. It should be also emphasized that NH3 reluctantly reacts with CNT in the pure form due to the significant activation barrier and preferential adsorption in structural defects. Furthermore, the activation barrier of NH3 adsorbed in CNT defects can be lowered by the presence of previously dispersed oxygen atoms. In a paper published by Peng, a change of the charge transfer in CNT exposed to NOobserved . It was 3 on the CNT wall does not induce any effect and the sensing signal arises from the CNT/metal contact. When NH3 is absorbed on the CNT/metal interface then the electrostatic charge balance between CNT and metal is disturbed by NH3 dipoles, which results in an increase of the Schottky barrier for hole injection. The sensitivity is gate voltage-dependent. In GS) bending the energy band of the CNT upward leads to narrowing of the Schottky barrier width, holes can tunnel through the barrier. At a positive gate voltage, the Schottky barrier width is too small for tunneling. Using CNT channels as a sensing element, the charge transfer leads to moving the Fermi level of the exposed CNT channel upwards and the energy band shifts downwards. Thus, a potential barrier is created impeding the current flow (A comparison of the two detection mechanisms related to the modulation of the Schottky barrier (SB) and the charge transfer (CT) shows some differences. For example, at room temperature, the absorption of NHent flow d. Here, 2, an observed signal amplification effect can result from the formation of CNTs embedded in SnO2. The formation of channels on the metal oxide surface may lead to an increase in gas molecules diffusion to the MOX surface, as well as to locally increase the electric field at the CNT-SnO2 interface [The SB detection is characterized by a very high sensitivity at room temperature but low reversibility, whereas the CT mechanism shows a low level of sensitivity at >150 °C and a high degree of recovery. The change of nanomaterials conductivity can be also connected to the reduction of the charge mobility in the CNT by forming areas disturbing the flow of charge. As we have already mentioned a single CNT does not have sufficient length to form conductive channels which are basically formed by combining multiple CNTs. Thus, if the analyzed substance is adsorbed in the connections between the nanotubes, the conductive channels are defective and the CNT conductivity will be modified . In the nterface .2) were proposed. Wei et al. explain the gas-sensing by amplification effect of the PN junction structure between n-SnO2 and p-SWCNT [The various sensing mechanisms of CNT-MOX , X-ray diffraction, computational methods , and aromaticity indices analysis. −1) marked by Versanyi [To assess an influence of metals on the electronic system of different (aromatic) ligands with potential biological activity, we applied different methods such as the Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy (UV/VIS), nuclear magnetic resonance spectroscopy , Hg(II), Ag(I), Pb(II), and alkali metals. In this case, both, ligand’s electronic system and aromatic system are being disturbed. Moreover, bond polarization increases. Absorption bands related to π→π* transitions move to the shorter wavelength (hypochromic shifts). FTIR and FT-Raman bands characteristic for an aromatic moiety shift towards smaller wave numbers and their intensity decreases or vanishes. Here, X-ray data and aromaticity indices indicate differentiation of both, the length of bonds and angles between bonds in aromatic rings. Moreover, the delocalization of the electronic charge is decreased. We observed similar effects while analyzing oxygen adducts of Fe, Ru, and Os complexes with porphyrins by means of Raman spectroscopy and matrix isolation spectroscopy .2 and H2O results in a decrease in resistivity which claims their electron acceptor nature, while absorption of NH3 and CO leads to an increase in resistivity which indicated their electron donor character [Distribution of the electronic charge, as well as HOMO/LUMO , level occupancy determines not only reactivity and stability of molecules but also aromatic ring susceptibility to electrophilic substitution. An increase or decrease of an electronic density in the aromatic ring (including graphene and porphyrins rings) triggered by the influence of different metals, substituents, or even trace amounts of gases may result in changes in conductivity (resistivity) of electronic nose sensors. haracter ,41.Corroles), this effect was observed for magnesium whereas for iron it is not evident [The probable cause of an increased sensitivity of metal complexed porphyrins is the stabilization of its electronic system. It has been shown that there is a relationship between an increase of sensitivity and selectivity and the polar nature of volatile compounds. It suggests that the polar groups bind through hydrogen bonds in porphyrin analogs rings in which three hydrogen atoms are present instead of one. In the presence of polar compounds, an introduction of metal ions in the porphyrin analogs is not a sufficient method to improve the detection properties compared to the porphyrins in the basic form. Complexation with iron and magnesium always increases the sensitivity of porphyrins however, in the case of porphyrin analogs , graphene oxides (GO), and reduced graphene oxides (RGO) are excellent materials for the construction of gas sensors due to their electronic, chemical, mechanical, and thermal properties, as well as high sensitivity to surface adsorption of gas molecules. The morphological characterization of the graphene structure was presented in , and CO . The dis, and CO ,42. Diff2 and O2 adsorption convert the system to p-type semiconductor, while the NH3 adsorption leads to n-type behavior. The p- and n-type semiconducting behavior can be detected by applying and modulating gate voltage. Among all gas molecules considered, the absorption of the NH3 molecule can enhance conductance [2 can be an electron acceptor from the material where NO2 has been adsorbed, therefore, a decrease in electron density and an increase in graphene’s resistance is expected. According to Latif, similar conclusions were presented where the increase of graphene sensor resistance in contact with NO2 was shown [2 adsorption can take place in low energy centers of graphene via sp2 carbon atom or in high energy centers  [2 is adsorbed mainly via oxygen functional groups [2 molecule, the positively charged hole is formed in the graphene’s structure [2. The results of the experiment carried out by Nomani showed that the exposure of graphene to NO2 at a concentration of 500 ppb and 18 ppm caused a decrease in conductivity of 2.25% and 10%, respectively [The electronic structure of graphene can be modified by gas molecules in diverse ways. COductance . In the ductance . NO2 canas shown . The NO2defects) . NO2 is l groups . As a retructure . Thus, tectively . It was 2, NH3, H2O, H2, and CO can act as electron donors or acceptors which may cause a change in the sensitivity and conductivity of graphene. Graphene, being a perfect crystalline material with a high surface to volume ratio, can undergo fluctuations in the charge carrier’s concentration by adding even several additional electrons. It is possible to distinguish two basic charge transfer mechanisms which lead to a change in graphene conductivity. Firstly, the charge transfer can depend on the relative position of the HOMO and LUMO orbitals. If the HOMO orbital is above the Fermi level of pure graphene (Dirac point) then the charge transfer takes place towards graphene. However, if the LUMO orbital is located below the Dirac point, then the charge transfer takes place towards the adsorbent particle. Secondly, the charge transfer between the absorbed molecule and graphene can be partially affected by the mixing of HOMO and LUMO orbitals with graphene orbitals (hybridization) [The adsorbed gases such as NO, NOization) .3 group which is an electron donor to the graphene aromatic ring leads to an increase in the electronic density in the ring and activates it by directing the substituent to the ortho- or para-position. Thus, electron donor groups improve the conductivity of graphene. NO2 as an electron acceptor that directs the substituent to the meta-position withdraws electrons from the graphene aromatic ring and thereby, inhibits electrophilic substitutions [2, −CH3, −C2H5, activating the benzene ring) and type II  can be used in the classification of trace amounts of gases. The type I substituents push the electrons into the ring and activate it, while the type II substituents pull out the electrons from the ring and deactivate it.According to the, well known, mechanisms the NHitutions . Electro2 and Cl2. For comparison, RGO-IL shows a strong response to all four gases and a negative type of conductivity (type n). In addition, it has been proven that IL content has a significant effect on the conductivity of the gas-sensitive material, and the sensitivity of RGO increases with the increase in IL concentration. The mechanism of changing the RGO conductivity can be based on the presence of oxygen groups that lead to disturbance of the electronic structure. An improvement of the sensitivity of the sensor by surface modification of reduced graphene oxides using various types of ionic liquids (IL) with a tailored structure was proposed by Zhu et al. . It was Alizadeh et al. suggest the significant differences in the selectivity of the sensor formed from RGO which depends on the conditions of oxide synthesis . The forSome molecules with reducing properties can change the electronic and adsorptive properties of RGO by transferring oxygen, nitrogen or the entire functional group to the graphene structure. In the case of GO exposure to hydrazine, the oxygen functional groups are removed from the oxide, while the hydrazine nitrogen atoms are covalently attached to the GO surface. The nitrogen atom can play a function of the n-type dopant and modify properties of the final graphene product . 4 effectively reduces carbonyl groups, however, it has low efficiency in reducing epoxides and carboxylic acids. Ascorbic acid is a moderate reducing agent compared to the previous two. The advantage of using vitamin C as a reducer is to minimize the risk of introducing heteroatoms into the RGO structure [Sodium borohydride is a better reducing agent than hydrazine but introduces several heteroatoms to RGO. It has been demonstrated that NaBHtructure .0 parameter, where ΔR is the resistance difference between the sensor response after and before the odor exposure, and R0 is the resistance due to the response on the odor exposure. Depending on the reductor used, the difference in the ΔR/R0 parameter was 3% for ethanol and 5% for acetone [Results presented by Alizadeh indicate a significant effect of graphene oxidation and reduction of graphene oxides on the final porosity and surface of the obtained materials . In the  acetone .2 [2S, CO, and NO2 [2 adsorption, while doping graphene with Si significantly improves the sensitivity to NO and NO2. The sensor built of N-Si-G shows sensitivity towards 21 ppm NO2 and the sensor response declines along with the gas concentration to ~1 ppm [Experimental and theoretical studies proved that the sensitivity of graphene-based sensors can be significantly improved by doping with Br, N, P, Ga, Cr, Mg, S, and Si. Doping leads to the formation of new active sites on the graphene’s surface which have an ability to strongly adsorb gas molecules. For example, doping graphene with Mg and Cr results in an increase in sensitivity towards SO2 ,59, whil and NO2 ,61, respo ~1 ppm . In addio ~1 ppm . The sum3 (including the type I substituents) increase the electronic density in the aromatic ring and stabilize electronic systems. Substituents with low ionic potential  destabilize the electronic systems of aromatic ligands [2, CO, SO2, CO2, N2O3, and NO radically reduce the conductivity of graphene, while NH3 increases its conductivity. In addition, metal-complexed porphyrins  shows greater sensitivity and selectivity to trace amounts of NH3 than porphyrins in the basic form.To enhance the interpretation of the sensor detection molecular mechanisms in the e-nose, we used our previous analysis of the influence of metals and substituents on the electronic systems of carbon and heterocyclic rings of selected aromatic ligands . We show ligands ,39,85,863) and delocalization of the electronic charge distribution results in an increase of the graphene sensor conductivity. Both phenomena show a certain analogy to the metal’s electrical conductivity. High electronic density and delocalized charge surrounding the atomic strands of metals are the cause of the excellent conductivity of these substances. The presented idea of the radical change of the graphene conductivity under the influence of type I and II substituents and the change of sensitivity and selectivity of porphyrins complexed with metals is at this stage purely qualitative. The quantitative confirmation of the described relationships requires further research.The comparison of our previous research with the analysis in the literature suggests that the increase of graphene electronic density  and the phenomena of electron transfer can significantly affect the change in graphene conductivity under the influence of trace amounts of various gases.The proposed approach to the gas detection mechanism can open or facilitate the search for further practical applications of graphene, nanotubes, and porphyrin derivatives in various fields of science and industry. For the quantitative confirmation of the presented thesis, further experimental and theoretical studies are necessary.


Background: Programmed death-ligand 1 (PD-L1) expression in non-small cell lung cancer (NSCLC) is considered as a predictive biomarker of anti-PD-1/PD-L1 cancer therapies. However, the correlation of PD-L1 expression status between the primary and paired metastatic NSCLC is still not clear. The current study aims to address this specific issue.Materials and Methods: The PD-L1 expression of the primary and paired metastatic lesions from 110 patients with NSCLC was retrospectively evaluated by immunohistochemical assay using Anti-PD-L1 antibody, Clone 22C3. The results were assessed by the Tumor Proportion Score (TPS) using cutoff values of <1%, 1%-49% and ≥50%. Meanwhile, the Cohen's kappa coefficient (k) of agreement was calculated.Results: An overall concordance rate of the PD-L1 expression between the primary and metastatic lesions was 61% (63/103) . If using TPS considering 1% and 50% as a threshold, the inconsistent rate was 28/103 (27.2%) paired specimens  and 14/103 (13.6%) paired specimens , respectively. Moreover, the concordance of the PD-L1 expression between primary and metastatic tumor was also analyzed according to the clinical stages within the untreated group of patients. We observed that for patients with stage I-III NSCLC, the concordance rate of the PD-L1 expression between primary and metastatic lesions was 81.3% and 100% when using 1% and 50% as threshold, respectively. While in stage IV patients, the concordance rate of the PD-L1 expression between the primary and metastatic lesions drops to 71.4% and 85.7%, respectively.Conclusion: The PD-L1 expression was dynamic as tumor developed, which was valuable in selecting the proper type of sample for accurately evaluating the prognosis of using pembrolizumab as first or second line treatment. Cancer is not just a gathering of a larger number of malignant cells but also a complex “barbarous” organs, to which many other cells are recruited and can be corrupted by the transformed cells. Interactions between malignant and non-transformed cells create the tumor microenvironment (TME). The non-malignant cells of the TME have a dynamic and often tumor-promoting function at all stages of carcinogenesis Studies to date suggest the expression of PD-L1 in tumor cells is induced by various mechanisms, not limited, but at least including oncogenic signaling and cytokines secreted from tumor-infiltrating immune cells and is closely related to the effectiveness of current PD-1/PD-L1 immunotherapy developed to date. As PD-L1 expression is largely modulated by local TME factors, it is important to have a better understanding on its expression correlation between the primary and paired metastatic NSCLCs. Earlier studies in a relatively smaller size clinical sample have already indicated a discrepancy in PD-L1 expression between primary and metastatic tumor lesions Table 1.110 patients who underwent surgical resection or aspiration biopsy of primary and metastatic tumors at the departments of pulmonary medicine and pulmonary surgery between May 2010 and November 2018 were enrolled in this study. All of the included patients met the following inclusion criteria: (1) the primary tumor histologically confirmed as non-small cell lung cancer; (2) pathologically confirmed with distant metastasis or local recurrence; (3) with or without anti-cancer therapy when first diagnosed as NSCLC. The patient demographics, tumor characteristics, adjuvant chemotherapy and follow-up data were collected from the electronic medical record system. The study was approved by the Institutional Research Ethics Committee of Guangdong Provincial People's Hospital. The clinical and pathological features of the cohort of patients are illustrated in th American Joint Committee on Cancer (AJCC) Among the 110 patients, 103 of them had metastases  and 7 of them had local recurrences. The sites of distant metastases included: homolateral/contralateral supraclavicular lymph node (30), pleura (22), brain (21), renicapsule (7), bone (including centum) (11), liver (1), diaphragm (1), pericardium (1), omentum majus (1) and perivascular phrenic nerve (1). Morphologic classification and tumor-node-metastasis (TNM) staging were assigned according to the current World Health Organization (WHO) and the 7All tumor samples were fixed in 10% neutral buffered formalin for 8-24 hours . And then, specimens were blocked into a thickness of 3 or 4 mm, fixed in formalin and dehydrated and cleared in a series of alcohols and xylene, followed by infiltration with melted paraffin. Paraffin embedment was performed. Paraffin sections were cut at 4 µm and heat attached to Superfrost Plus slides in 65˚C oven for 1 hour.TM FLEX visualization system (ASL 48) was performed as it is currently the recommended assay for the detection of PD-L1 expression TMFLEX Target Retrieval Solution Low pH (pH 6.1)  for 40 minutes at 97˚C. The rest of IHC assay steps were performed on ASL 48 according to the manufacturer's instructions.PD-L1 immunohistochemistry (IHC) using mouse monoclonal Anti-PD-L1, Clone 22C3 based on EnVisionThe PD-L1 expression of the specimen was assessed by the Tumor Proportion Score (TPS). The TPS is the percentage of viable tumor cells showing partial or complete membrane staining relative to all viable tumor cells present in the sample (positive and negative), which requests at least 100 viable tumor cells in the specimen Especially, score only viable tumor cells. The following cells were excluded from scoring: infiltrating immune cell, normal cells, necrotic cells, and debris. The results were scored on a three points scale  and thus interpreted as: no PD-L1 expression (TPS < 1%) was scored a 1, low PD-L1 expression (TPS 1%-49%) was scored a 2 or high PD-L1 expression (TPS ≥ 50%) was scored a 3 according to the previous study.H scores, which show the change value of PD-L1 expression between primary and metastatic tumors, were calculated. H scores have a value ranging from -2 to 2  and are defined as:P values < 0.05 were considered statistically significant.The concordance rate of PD-L1 expression between primary and metastatic tumors as well as different stages NSCLCs was compared and analyzed. At the same time, the Cohen's kappa coefficient of agreement was calculated, which was used to classify the level of concordance as: poor (<0.00), slight (0.00-0.20), fair (0.21-0.40), moderate (0.41-0.60), substantial (0.61-0.80), almost perfect (0.81-1.00) Table The patients in the untreated group originally underwent surgical resection or aspiration biopsy without prior chemotherapy or radiotherapy. The PD-L1 expression status and scores of their primary and metastatic lesions is shown in  P < 0.001. If 1% TPS was used as a threshold, 8/30 (26.7%) of the metastatic lesions had inconsistent PD-L1 expression compared to the primary tumor tissue , among which, 7 (23.4%) cases had reduced PD-L1 expression and 1 (3.3%) case had increased PD-L1 expression in the metastasis lesions.The overall concordance rate between the primary and metastatic lesions was 70% (21/30) with a Cohen's kappa coefficient of 0.46 andk = 0.78, and P < 0.001), among which, 1 (3.3%)cases had reduced PD-L1 expression and 1 (3.3%) case had increased PD-L1 expression in the metastasis lesions.If 50% TPS was used as a threshold, 2/30 (6.6%)of the metastatic lesions had inconsistent PD-L1 expression compared to the primary tumor tissue (Z) = -0.333, P-value (P) = 0.739.A Wilcoxon-signed ranks test was conducted to determine if there were differences in PD-L1 expression scores between primary and metastatic tumor in untreated NSCLC patients. The results showed that Z-value (Table 2b). The concordance rate of PD-L1 expression between the primary and metastatic samples for patients staging I-III was 81.3% when 1% was considered as the threshold, while it reached 100% when 50% was as the cut-off value . For stage IV patients, this number dropped to 71.4% and 85.7% , respectively.The concordance of PD-L1 expression between the primary and metastatic tumor tissue for the untreated patients was analyzed based according to the clinical staging (U) = 106.5, Z = -0.283, P = 0.777.A Mann-Whitney U test was used to determine if there were differences in H scores between stage I-III and stage IV in untreated NSCLC patients. The results showed the stage I-III (mean rank = 15.11) and the stage IV (mean rank = 15.84), U-value , brain (1), renicapsule (2), homolateral/contralateral supraclavicular lymph node (3).Table 4.The patients in the treated group were diagnosed as NSCLC after surgical resection or aspiration biopsy, followed by either targeted drugs treatment, chemotherapy or radiation therapy. PD-L1 expression status and scores in primary and metastatic lesions of this group of patients is shown in k = 0.45, and P < 0.001), among which, 18 (22.5%) cases had reduced PD-L1 expression and 3 (3.8%) case had increased PD-L1 expression in the metastasis lesions.The overall concordance rate was 60% (48/80) with a Cohen's kappa coefficient of 0.37. If 1% TPS was used as a threshold, 21/80 (26.3%) of the metastatic lesions had inconsistent PD-L1 expression compared to the primary tumor tissue  and conventional treatment in NSCLC patients (mean rank = 55.43), Table 4.The PD-L1 expression status in primary and distant metastatic NSCLCs with or without prior clinical treatment is shown in  P < 0.001. If 1% TPS was used as a threshold, 28/103 (27.2%) of the metastatic lesions had inconsistent PD-L1 expression compared to the primary tumor tissue , among which, 24 (23.3%) cases had reduced PD-L1 expression and 4 (3.9%) case had increased PD-L1 expression in the metastasis lesions.The overall concordance rate was 61% (63/103) with a Cohen's kappa coefficient of 0.39, andk = 0.53, and P < 0.001), among which, 10 (9.7%) cases had reduced PD-L1 expression and 4 (3.9%) case had increased PD-L1 expression in the metastasis lesions.If 50% TPS is used as a threshold, 14/103 (13.6%) of the metastatic lesions had inconsistent PD-L1 expression compared to the primary tumor tissue  paired metastatic sample, in which increased PD-L1 expression was observed in local recurring lesions. Due to the limited size of the current study sample, the concordance rate cannot be evaluated using 50% TPS as threshold.Z = -0.1, P = 0.317.The results of the Wilcoxon-signed ranks test showed U = 326.5, Z = -0.483, P = 0.629.A Mann-Whitney U test was run to determine if there were differences in H scores between distant metastatic lesions and local recurrences in NSCLC patients. The results showed distant metastatic lesions in patients (mean rank = 55.17) and local recurrences in NSCLC patients (mean rank = 60.36), PD-L1 protein expression status evaluated by IHC assay is currently the mainstream predictive biomarker for the prognosis PD-1/PD-L1 immunotherapy. The PD-L1 IHC 22C3 pharmDx kit is an FDA approved platform to evaluate patients with metastatic NSCLC for possible pembrolizumab intervention. For NSCLC patients with a ≥ 50% TPS of PD-L1 expression, pembrolizumab can be effectively used as first-line treatment and as a second line therapy for patients with 1% TPS of PD-L1 expression In fact, a majority of patients with advanced NSCLC are usually evaluated for PD-L1 expression through aspiration biopsy tissues rather than surgical resection specimens, and most of the biopsy tissues are obtained from metastatic sites. Thus, a better understanding the correlation of PD-L1expression in metastatic lesions and the related primary tumors is particularly important for accurate therapeutic treatment selection.k= 0.46, and P < 0.001) and 60% , respectively. This result is consistent with results from a previous study, in which the concordance of PD-L1 expression between primary tumor and metastatic lesions from the lymph nodes based on a cohort of 66 patients was 62%; If the 1% and 50% TPS were used as a threshold, PD-L1 expression concordance were 74% and 88% respectively In this study, we not only compared the PD-L1 expression status between the primary and metastatic NSCLCs, but also that between the untreated patients and treated patients. The overall concordance rate of PD-L1 expression status between primary tumors and metastatic lesions in treated and untreated patient groups is 70%  paired metastatic sample at 1% cutoff. Despite of the limited sample size, the data showed that locally recurrent tumors may display a different PD-L1 expression statue compared with the primary tumors. In addition, our study demonstrated for the first time that, for NSCLC patients at relatively early stage (I-III) without prior therapy, the concordance rate for PD-L1 expression in primary and metastatic NSCLC is higher compared with those for the stage IV patients .Fig.1). It was consistent with a recent study that significant changes of PD-L1 expression in tumor cells were observed in a part of NSCLC patients who underwent anticancer treatments. 21Moreover, we observed that the PD-L1 expression presented a dynamic variation as tumor advanced, especially in late stage IV state  or anticancer treatment in the process of tumor development, which is consistent with earlier reports. Tumor cells could continually create a TME that was suitable for their growth and survival as the tumor increases in size In our study, the concordance rate of PD-L1 expression between primary tumors and distantly metastatic lesions were 72.8% and 86.4% at 1% and 50% threshold respectively. While the concordance rate of PD-L1 expression between primary tumors and local recurrences was 85.7% using 1% cutoff value. Most importantly, for the first time, we observed that patients with staging I-III without previous treatment has a much better concordance rate for PD-L1 expression in primary and metastatic NSCLC than that from the staging IV group. Due to the limited sample size, the results of the Wilcoxon-signed ranks test and the Mann-Whitney U test in H scores were not statistically different. If this finding can be further verified by studies involving much larger sample size, it is acceptable to use the biopsy from metastatic site or aspiration biopsy tissues for PD-L1 expression evaluation for stage I-III NSCLC patients, but not for late stage (IV) patients. This finding might provide the guideline in selecting the proper type of sample for accurately evaluating the prognosis of using pembrolizumab as first or second line treatment at 50% and 1% threshold, respectively. Consistent with earlier studies, we also found that a lower concordance rate (60%) was detected in NSCLC patients undergoing anticancer treatments during the clinical course.In short, the PD-L1 expression was dynamic as tumor developed, which was valuable in selecting the proper type of sample for accurately evaluating the prognosis of using pembrolizumab as first or second line treatment. Future studies are required to further verify PD-L1 expression in different stages of cancer development and its relevance with therapeutic efficacy of PD-1/PD-L1 treatment. A better understanding of PD-L1 expression during tumor progression and clinical progresses will definitely advance current PD-1/PD-L1 therapies and allow the achievement of precise cancer treatment.


This meta-analysis systematically evaluated the efficacy and safety of anti-PD-1/PD-L1 antibodies for pretreated advanced or metastatic nonsmall cell lung cancer (NSCLC) and investigated the correlation between PD-L1 expression levels and effectiveness of anti-PD-1/PD-L1 antibody. The methodology was based on the Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) and the Cochrane Collaboration guidelines. Our research included five randomized-controlled trials involving 3,025 patients. We compared anti-PD-1/PD-L1 antibodies  with docetaxel in pretreated patients with advanced or metastatic NSCLC. The pooled hazard ratio (HR) for overall survival (OS) and progression-free survival (PFS) was 0.69  and 0.87 , respectively. Meanwhile, the pooled risk ratio (RR) for objective response rate (ORR) was 1.53  in all patients. Subgroup analyses showed that anti-PD-1/PD-L1 treatment significantly improved OS in patients with PD-L1 expression at any level, even in patients with PD-L1<1%. The RR for occurrence of grades 3 to 5 treatment-related adverse effects was 0.23 . OS, PFS, and ORR were significantly more improved for patients treated with anti-PD-1/PD-L1 antibodies than for those treated with docetaxel. Anti-PD-1/PD-L1 therapy resulted in longer OS than docetaxel, regardless of PD-L1 expression; however, higher PD-L1 levels were likely to correlate with better outcome. Anti-PD-1/PD-L1 antibodies also had a better safety profile than docetaxel. Lung cancer represents the main cause of cancer-related mortality worldwide, , 2 with Patients with previously treated, advanced, or metastatic NSCLC are difficult to treat, with systemic cytotoxic chemotherapy  having only modest benefits. In recent years, epidermal growth factor receptor (EGFR) inhibitor development and application has shown significant benefits for advanced or metastatic EGFR-positive NSCLC patients, –8 thoughImmunotherapy is a relatively new paradigm for the treatment of NSCLC. The programmed death-1 (PD-1) receptor, expressed by activated T-cells, is engaged by the tumor-expressed ligands PD-L1 and PD-L2 to reduce T-cell activation and facilitate tumor immune escape. –12 PD-1/Several inhibitors  targeting the PD-1 immune checkpoint pathway have been developed and approved by the United States Food and Drug Administration (USFDA) for the treatment of NSCLC. Compared with docetaxel, Nivolumab, a fully humanized IgG4 PD-1 inhibitor, showed significantly better overall survival (OS) and response rates (RR) in advanced squamous NSCLC, regardless of PD-L1 expression level . In anotIn the 2017 updates (Version 4), the NCCN Panel recommended that PD-L1 levels did not instruct the guidelines for treatment with some PD-1/PD-L1 agents, while other PD-1/PD-L1 agents were approved restrictively for patients with PD-L1 expression level ≥1%. Thus, the question remains whether PD-L1 expression should serve as predictor and guide for patient selection.The aim of this meta-analysis is to further evaluate the efficacy and safety of anti-PD-1/PD-L1 agents in advanced NSCLC patients. A subgroup analysis was performed to determine the correlation between PD-L1 expression level and clinical outcome and to establish guidelines for PD-L1 antibody treatment in patients with low or negative PD-L1 levels.This meta-analysis was performed in conformity with the PRISMA   and CochWe performed a literature search of PubMed, Embase, and Cochrane Library electronic databases, using a combination of the terms “Carcinoma, Nonsmall-Cell Lung” [MeSH] or “NSCLC” and “PD-1” or “PD-L1” and “nivolumab” or “pembrolizumab,” or “atezolizumab.” The last search was performed on March 20th, 2017. No restrictions for language or publication year were set in the search.The criteria for study inclusion were as follows:(1) Prospective randomized-controlled trials (RCTs) designed for PD-1/PD-L1 inhibitor therapy for patients with advanced or metastatic NSCLC that had been previously treated.(2) Published efficacy and safety measures reported and correlated to PD-L1 expression levels.Two reviewers (Q.L.Z. and X.H.W.) independently reviewed all abstracts, obtained full-text reports, and extracted data into separate databases. Disagreements were resolved through team discussion. For each study, the following information was extracted: first author's name, year of publication, trial phase, number of randomized patients, treatment strategies, clinical outcomes, PD-L1 status, hazard ratio (HR) for overall survival (OS) and progression-free survival (PFS) and their 95% confidence intervals (CIs), objective response rate (ORR), PD-L1 expression level, and overall grades 3-5 adverse events (AEs) and per grades 3-5 AEs.The primary endpoint was overall survival rate. Secondary endpoints included PFS, proportion of patients with an objective response rate (ORR), and safety. The analyzed safety outcomes were grade 3-5 adverse events (AEs), including fatigue, decreased appetite, nausea, vomiting, diarrhea, constipation, anemia, neutropenia, and febrile neutropenia.The 5-item Jadad scale was used to assess the quality of clinical trials and the calculated score was based on randomization, double-blinding, and reported withdrawals  20]..20]. P<0.05 was considered statistically significant. We assessed heterogeneity using a χ2 test with P<0.10 considered to be statistically significant. A fixed effect model was used when heterogeneity between studies was absent and a random effect model was used when heterogeneity was present. Subgroup analysis was calculated based on PD-L1 expression levels. Sensitivity analyses were used to estimate the effect of each individual study by removing one by one from analysis. Publication bias was assessed using funnel plots.All outcomes were pooled using RevMan 5.3 (Nordic Cochrane centre). Our analyses pooled HR with 95% CIs for OS and PFS and risk ratios (RR) with 95% CIs for ORR and grade 3-5AEs. HR<1 favored the experimental group (anti-PD-L/PD-L1 antibodies) whereas HR>1 favored the control (docetaxel). For each objective response rate and grade 3-5 AEs, a risk ratio (RR) was calculated based on the absolute numbers of patients presenting the objective response and grade 3-5 AEs, respectively. RR for ORR and AEs<1 indicated a higher overall response rate and toxicity in the control (docetaxel).A total of 101 relevant studies were electronically retrieved and 96 were excluded for the reasons shown in Five published RCTs involving 3,025 patients with subgroup analysis assessing the efficacy and safety of PD-1/PD-L1 inhibitors in NSCLC were included in this meta-analysis –17, 21. All included trials were considered high-quality data, as they were randomized when comparing anti-PD-1/PD-L1 agents  with docetaxel in the second or third line setting. Subgroup analyses, performed in all trials, explored the relationship between PD-L1 expression level and anti-PD-1/PD-L1 antibody efficacy. P<0.0001, and Ph=0.67)   (I2=59%), and the pooled RR for ORR was determined using a random effect model.Pooled results showed that anti-PD-1/PD-L1 antibodies significantly improved the OS   and PFS Ph=0.11)  in all pPh=0.03) . Moderat P=0.005, and Ph=0.29)  and ORR Subgroup analyses showed that anti-PD-1/PD-L1 antibodies could result in longer OS   than doc P<0.00001) ( P<0.00001), and ORR  when compared with docetaxel.However, in the PD-L1≥1% subgroup, PD-1/PD-L1 inhibitors significantly improved OS  , PFS   and for Therefore, this meta-analysis indicates that anti-PD-1/PD-L1 agents exhibited high efficacy in the treatment of advanced NSCLC. Anti-PD-1/PD-L1 therapy also had considerable activity for NSCLC and was superior to docetaxel in the PD-L1<1% population. PD-1/PD-L1 inhibitors tended to be associated with PD-L1 expression level. Higher PD-L1 expression was likely to be associated with increased benefit from anti-PD-1/PD-L1 agents.The meta-analysis showed that the rates of overall grade 3-5 adverse events (AEs) for the anti-PD-1/PD-L1 therapy were significantly lower than those of docetaxel . For anyThe direction and magnitude of the statistical significance of the overall results were confirmed by this analysis. The benefit of anti-PD-1/PD-L1 antibodies on overall survival was maintained (HR 0.69–0.69) even when we changed the fixed-effect model to a random-effect model. Subsequently, an influence analysis was performed by excluding individual studies. The benefit of anti-PD-1/PD-L1 antibodies on OS  did not vary regardless of study removal. The sensitivity analysis indicated the stability of all trials in the anti-PD-1/PD-L1 agents group.A funnel plot indicated no evidence of substantial publication bias .Blocking inhibitory immune checkpoints has recently gained interest as an immunological therapy for different kinds of cancer, especially advanced NSCLC. Binding of PD-1 to its ligands (PD-L1 and PD-L2), which are present on tumor cells, suppresses T-cell activation and results in immune response evasion , 22–24. In this study, a systematic meta-analysis of randomized clinical trials demonstrated the high efficacy and safety of anti-PD-1/PD-L1 antibodies for previously treated patients with advanced or metastatic NSCLC. Pooled results confirmed that anti-PD-1/PD-L1 agents significantly improved OS, PFS, and ORR in advanced or metastatic patients, both in the intention-to-treat population and in subgroups with PD-L1 expression level at 1% or more, 5% or more, and 10% or more. A high PD-L1 expression was likely to be associated with increased benefits. Furthermore PD-1/PD-L1 inhibitors also improved OS in the population with PD-L1<1%, which contradicts the guidelines for pembrolizumab administration only in PD-L1 positive patients (PD-L1≥1%). This discrepancy, may be attributable to the fact that the pembrolizumab trials excluded patients with PD-L1<1% patients or that the PD-L1 test might not accurately determine tumor PD-L1 levels. Other possible reasons may include heterogeneity of expression and sampling error, or that test samples predate earlier lines of therapy. Therefore, patients with PD-L1 expression levels just below and just above 1% will likely exhibit similar responses. Our results provide useful information for clinicians to inform their patients about treatment options for advanced NSCLC in the PD-L1<1% population. However, further research is needed to confirm these findings.Subgroup analyses showed a trend toward a greater efficacy as PD-L1 expression level increased. In other words, patients that expressed the highest levels of PD-L1 derived the greatest benefit from anti-PD-1/PD-L1 therapy . Importantly, patients with PD-L1<1% (HR=0.79) also experienced OS longer than those treated with docetaxel without any evidence of statistical heterogeneity; however, PFS and ORR showed no difference. These results may imply that the benefit from PD-1/PD-L1 inhibitor versus docetaxel in pretreated advanced NSCLC is not limited to the PD-L1>1% population. More importantly, our findings could indicate a dose-effect relationship between the levels of PD-L1 expression and the potential benefit from PD-1/PD-L1 inhibitors. However, our meta-analyses included only five RTCs, and to further confirm these hypotheses, larger sample size studies are necessary.I2=78%, Ph=0.0003). The reason for heterogeneity could be because different PD-1/PD-L1 inhibitors  have potentially specific pharmaceutical characteristics. Treatment-related AEs of grade 3-5 were similar with those observed after docetaxel treatment and included decreased appetite, nausea, vomiting, and constipation. However, hematological AEs (anemia and neutropenia), febrile neutropenia, fatigue, and diarrhea were all significantly less common for anti-PD-1/PD-L1 agents. Only a small percentage of patients treated with anti-PD-1/PD-L1 agents reported immune-related adverse events, including hypothyroidism and pneumonitis, and with the use of appropriate protocol guidelines, these events were relieved. Our study showed that anti-PD-1/PD-L1 therapy is superior to docetaxel in clinic application and presents a lower risk for treatment-related adverse events.Treatment-related adverse effects are an important evaluation index for any antitumor therapies. Our meta-analysis showed that anti-PD-1/PD-L1 antibodies had lower risk of total grade 3-5 adverse events than docetaxel. Pooled RR for total grade 3-5 adverse events was 0.29  compared with docetaxel, with statistical heterogeneity (In an era of personalized medicine using PD-1/PD-L1 inhibitors, predictors of response to therapy are important for making informed treatment decisions. PD-L1 expression may be an encouraging predictor for anti-PD-L1/PD-1 therapy in NSCLC, but standardizing PD-L1 testing has presented several problems. Different studies showed contradictory results regarding the relationship between drug efficacy and PD-L1 expression levels. Brahmer et al.  showed tOur analysis has some limitations. Due to the recent introduction of PD-L1 inhibitor therapy for pretreated advanced NSCLC, there were only five randomized clinical trials that investigated the efficacy and safety of anti-PD-1/PD-L1 antibodies, which limited the number of studies available for our meta-analyses. More randomized controlled trials with a larger sample size are needed to establish and replicate these clinical outcomes. Second, all five trials were liable to probable bias due to an open-label study design. Third, statistical heterogeneity was found when we pooled the objective response rate and the grade 3-5 adverse effect rates, respectively. Because of this, we used a random-effect model to pool outcomes. Since no evidence of substantial publication bias was found, these results indicated reliability to evaluate clinical outcomes.In conclusion, we analyzed five RCTs and systemically verified favorable OS, PFS, and ORR of anti-PD-1/PD-L1 therapy for pretreated advanced or metastatic NSCLC and demonstrated higher efficacy and safety for these agents than for docetaxel. More importantly, the results of this meta-analysis suggested that anti-PD-1/PD-L1 antibodies could also improve overall survival even when PD-L1<1%, which has not been recommended by previous studies. Our results could be of great value in guiding selection of clinical therapeutic regimens. More prospective studies are necessary to confirm these results and to improve the optimal dosage for PD-1/PD-L1 inhibitors in NSCLC.


In this research, we established a facile and low-cost strategy to construct graphene thin film enabled yarn sensors (GYS) by combining the process of graphene oxide (GO) coating and reducing on polyester (PE) wound spandex yarns. According to systematic processing-property relationship study, a key finding of this work discovers that the degree of resistance recovery as well as gauge sensitivity of GYS can be well controlled and modulated by a pre-stretch treatment. Specifically, as the level of pre-stretch increases from 0 to 60%, the deformable range of sensor that guarantees full resistance recovery prolongs evidently from 0% to ~50%. Meanwhile, the gauge factor of GYS is tunable in the range from 6.40 to 12.06. To understand the pre-stretch process dependent sensing performance, SEM analysis was assisted to evidence the growing size of micro-cracks determining dominantly the behavior of electron transport. Lastly, to take better advantage of GYS, a new wearing mode was demonstrated by direct winding the yarn sensor on varied portions of human body for monitoring different body movements and muscle contracting & relaxing. With continuous development, metallic strain gauges as well as other traditional sensing elements/interfaces/devices with mechanical rigidity and/or limited sensitivity are no longer the best candidate to be applied in smart devices11. In a sharp contrast, the next-generation sensors enabled by new materials and new nanotechnology are highly demanded to meet the rising standards of high sensitivity, mechanical flexibility, and wearable stretchability13. Toward this goal, carbon nanomaterials have been widely explored by virtue of their robustness, structural noninvasiveness, and multifunctional properties. Compared with other carbon family members, e.g. fullerene14, carbon blacks16, and carbon nanotubes18, graphene show multiple unique advantages, including the ease of aqueous colloids preparation, great conformability to substrates and interfaces, and advanced contact-breakage mechanism with excellent piezo-sensitivity, etc.21. The above-mentioned characteristics have guaranteed a variety of novel strategies for assembling varied types of graphene sensors, e.g., 1D CVD-grown nanofibers22, surface-coated fibers24, hybrid composite fibers25, 2D thin films and free-standing papers27, as well as 3D foams, sponges and aerogels28.Since the last decade, flexible and wearable electronics have been attracting considerable attentions with upgrading concepts and strategies in varied fields of applications, e.g. smart fabrics19. Following this line of thought, in combination with extraordinary properties of graphene, different 1D graphene fiber sensors have been proposed for wearable applications. For examples, Wang et al. applied CVD method to fabricate graphene/PVA core-sheath nanofibers with the gauge factor of 5.02 and stretchability up to 16.1%22. Using one-step wet spinning processes, Jalili et al. fabricated reduced graphene oxide fibers with ultimate elongation of ~3% for multifunctional textiles29. To meet larger stretching requirements for monitoring human-body movements such as elbow and knee joint actions30, graphene enabled composite fibers are demonstrating great advantages when using commercial elastic yarn as the core substrate. By coating thin graphene layers onto elastic fiber yarns through dip-coating and layer-by-layer processes, for instance, Cheng et al.31, and Park et al.32 respectively developed graphene covered PE/PU yarns and graphene/PVA coated yarns for monitoring a variety of human motions from head to foot. Montazerian et al.33 also applied a layer-by-layer process to coat graphene nanoplatelets on silicone sheathed spandex yarns with tunable sensing range >40%. Compared with CVD and wet spinning processed sensors, the composite fibers show better mechanical affinity to woven fabrics, superior tensile performance, and wider applications.When considering embeddable and wearable characteristics for flexible electronics, the sensor with unique one-dimensional format is expected to be more flexible, lightweight, robust, and straightforward to be assembled through winding, weaving, and/or printing processes34 to 56.335 with different assembling methods and deformation conditions. For another, it is lacking of a systematic work investigating the structure dependent sensitivity, deformability, and reliability, which is crucial for unveiling the sensing mechanism. With effective capability to alter and control different microscopic features such as micro-cracks36, wrinkles37, and packing densities35, the pre-stretch process has already become a commonly-applied strategy to tune the performance of varied nanocarbon sensors, including processing efficiency38, mechanical/electrical stability39, as well as sensing sensitivity37. Following this line of thought, the application of pre-stretch toward the understanding of process dependent sensing property and mechanism for the unique graphene enabled smart yarn is highly significant. However, the relevant study is still not appeared.As a new-emergent strategy for assembly of graphene 1D fibers, nevertheless, the sensing performance as well as the mechanism is far from being fully exploited, especially when the commercial yarn core is always specifically-strengthened by multiple sheathed fiber layers twisted/coiled through certain angles. With the overview of relevant works, for one thing, it is still not understandable about the variation of the reported gauge sensitivity varied noticeably from 1.5Motivated by the argument mentioned above and to further advance this emerging field, in this research, we systematically explored the unique pre-stretching treatment on regulating both electrical stability and gauge sensitivity toward understanding the sensing behaviors of graphene thin film enabled yarn sensors (GYS). Firstly, a facile and low-cost strategy was established to construct the graphene coating layer on polyester (PE) wound spandex yarns by combining the process of graphene oxide (GO) coating and reducing. Ascribed to the helically covered structure, it is rather interesting that the level of pre-stretch plays an important role on controlling the degree of resistance recovery. As the pre-stretch is increased from 0% to 60%, the ideal deformable range of the sensor that guarantees full resistance recovery prolongs evidently from 0% to ~50%. In addition to the enhanced working range, the pre-stretch dependent sensing performance is highly advisable to optimize the gauge sensitivity of GYS from 6.40 to 12.06. Based on microscopic explorations, the apparent processing-property relationship of GYS is further explained by the variable size of micro-cracks on graphene thin films bridging originally over PE loops, influencing dominantly on both axial and helical directions of electron transport. To take better advantage of lightweight, conformability, tunable sensitivity, and free from packaging medium, a new wearing mode has been demonstrated by direct winding GYS on varied portions of human body for monitoring different motions, such as finger bending and muscle contracting & relaxing.40, the Na2S2O4 solution is applicable by oxidizing S2O42− to SO32− through reacting with hydroxyl and epoxide groups in GO41. Once again, the effective reducing process was convincingly proved by the pitch-black appearance of GYS as shown in Fig. 3) as well as copper electrode connection, the as-produced GYS sensors were ready for the following structural analysis and performance evaluation.Figure 31. Under higher magnification, Fig. −1 and 1582 cm−1 for both GO and GYS, confirming the existence of graphitic structures. After the process of GO reduction, the increased intensity ratio of D and G peak (ID/IG) from 0.968 to 1.072 suggests both the decrease in average size of the sp2 domain as well as the increased quantity of structural defects42. In addition to Raman, XRD spectra show clearly the shift of the characteristic 2θ peak from 11.38° to 24.27° after the reduction process, reflecting the removal of oxygen-containing groups and the decrease of interlayer spacing from 0.778 nm to 0.360 nm which is fairly close to the one acquired from TEM (0.350 nm)43.In addition to visual inspection, structural and chemical details of GYS were further evaluated by varied microscopic and spectroscopic methods. Low-magnified scanning electron microscope (SEM) image Fig.  first un45. Through the measurement, sensitivity of the smart yarn can be quantified by determining the gauge factor (GF), which is defined as d(ΔR/R0)/dε where ε is the mechanical strain applied to the yarn, R0 and R are respectively the resistance of GYS before and after deformation. Since the length of the yarn cannot be completely restored when mechanical strain exceeds 60% ascribed to its viscoelastic behavior46, the upper limit of its working range is bound to this critical value for the ease of cyclic testing. Figure 0) accordingly varies as the enhancement of mechanical deformation from 0 to 5/20/40/60%, intriguing the piezoresistive behavior of the conducting layer. During the stage of releasing (dashed lines), nevertheless, the decreasing trend of ΔR/R0 is not able to follow its rising trace. More seriously, the resistance fails to recover back to its initial value regardless of the level of the subjected deformation. The inset picture also clears that the higher the degree of stretching, the greater is the resistance when totally relaxed with the zero-strain ΔR/R0 ranging from 2.6% (5% strain treated) to 11.5% (60% strain treated). To better quantify this behavior, a representative GYS specimen as produced by the spraying & reducing assembly was successively treated by different pre-stretching processes from low to high levels. As the pre-stretch level is steadily increased from 0 to 60%, Fig. In order to systematically evaluate the sensing property, coupled electrical - cyclic tensile tests were applied to acquire piezoresistive responses of GYS sensors0) after experiencing the corresponding treatment of pre-stretch. As shown in Fig. max − Rf)/(Rmax − R0) where Rmax, Rf, and R0 are respectively maximum, final, and initial resistance, Fig. Benefit from the cyclic test, it is worth noting that the pre-stretching process plays a dominant effect on recovery of initial resistance. It means that if a GYS sensor has experienced certain treatment of mechanical stretching, the irreversible issue of resistance could be weakened in next stretching cycles. To prove the idea, a comparison study was examined for investigating the behavior of strain dependent resistance change  by combining the process of graphene oxide (GO) coating and reducing on polyester (PE) wound spandex yarns. The effect of pre-stretch processes on sensing sensitivity and degree of resistance recovery of GYS was studied systematically. The research results show that proper pre-stretch can optimize the performance of GYS. The ideal deformable range of the sensor that guarantees full resistance recovery increases from 0% to 50% after applying a 60% pre-stretch. As for the sensing performance, the gauge sensitivity increases from 6.40 to 12.06 when applied by a 30% pre-stretch. The sensing mechanism was further explained by exploring the micromorphology. With the augmentation of pre-stretch levels, the size of micro-cracks on graphene thin film grows accordingly, introducing the change of electron transport behavior on graphene thin films. As contact resistance increases, GYS becomes more sensitive but shows negative effect when beyond a critical value, ascribing to the cut off of the axial transmission path of electrons. Based on fundamental study, a new wearing mode of the yarn sensor by direct winding GYS on varied portions of human body has been demonstrated for monitoring different motions, e.g. finger bending and muscle contracting. The unique characteristics of GYS sensors with lightweight, robust, tunable sensitivity, and free from packaging medium demonstrated in this work can be highly valuable for developing next-generation wearable electronics.The graphene oxide (GO) dispersion was prepared by sonicating a mixture of 600 mg of graphene oxide nanosheets which was synthesized via the Hummers method in 200 mL of deionized water in an ice bath using an ultrasonic processor (Ultrasonics FS-600 N). The ultrasonic processor was operated in a pulse operation mode  with the power set at 510 W for 3 h to obtain the 3 mg/mL GO dispersion.The spandex yarns wound around polyester (PE) are commercially available. The yarn with the cut length of 5.5 cm was cleaned repeatedly using deionized water and dried with a heat gun for 5 min. A pair of clamps was used to fix the yarn sitting on the platform of the spray-coating system, consisting of a heat gun, an air compressor (Iwata IS-50), and an air brush (Iwata HP-CS) equipped on a computer controlled moving stage (Nordson E3). The heat gun was used to accelerate solvent evaporation and the air compressor was used to provide the pressure needed for spraying. In view of the requirement to avoid the heat gun wind for disrupting the spraying process, the heating machine was placed perpendicular to the air brush. To control the heating temperature of the sample around 100 °C, the distance from the heat gun to the yarn is set at 18.5 cm. Additionally, the distance from the nozzle to the elastic substrate is about 6 cm for best spraying effect. Before spraying, the yarn was slightly stretched to prevent it from shaking violently during the coating process.With the back-and-forth nozzle moving speed of 2 cm/s and spraying rate of 2.5 mL/min, 5 mL as-prepared GO dispersion was sprayed on the yarn surface with the accompanied color change from white to brown. After the top-direction spraying was completed, the yarn was axially rotated by 180° and received another 5 mL spraying treatment to ensure the uniform coating of graphene oxide. Finally, the GO coated yarn was soaked in 90 °C pre-heated 0.06 mmol/L sodium hydrosulfite solution for 2 h and 30 min. The reduced GO (rGO) yarn was washed with deionized water for several times and dried before use.The SEM characterization was accomplished using a JEOL JSM-7001F FE-SEM. Raman spectra were recorded on a HORIBA LabRAM HR Evolution spectrometer. XRD characterization was performed on Rigaku D/max 2550 with Cu Kα radiation (λ = 1.54°). In addition, the yarn was sputter coated with platinum before being examined by FE-FEM.To facilitate measurement and reduce contact resistance, two copper pieces were pasted onto each end of the yarn using conductive silver paste before strain sensing tests. The electric properties of the smart yarns were measured by a Keithley 2510 source meter. The sensing performances were evaluated by a mechanical-electric coupling test including a universal testing machine (MTS E44.104 with 500 N load cell) and the source meter. The tension was controlled by the universal testing machine with the fixed deformation rate of 20 mm/min and real-time changes of the sensor resistance were recorded by the source meter programmed by LabVIEW. The sensing performance under other deformation rates was summarized in Supplementary Fig. Video S1Supplementary Document


Nanoscrolls (NSs) assembled from two-dimensional nanosheets have emerged as a novel type of one-dimensional nanomaterials because of their unique topological features and properties. The scale-up preparation of the NSs is crucial for their foundational and applied research. Herein, we report a general and straightforward approach for efficiently converting two-dimensional nanosheets into the NSs with high yield. We demonstrated the converting process by illustrating the formation of the graphene nanoscrolls through characterizing their morphology and structure using a scanning electron microscope, transmission electron microscope, Raman spectra, and X-ray diffraction spectra. The graphene sheets with a few-lay number were converted immediately and entirely into the graphene nanoscrolls when they mixed with an ethanol solution of silver nitrate at room temperature. The as-prepared graphene nanoscrolls were confirmed to be formed via the layer-by-layer assembly of graphene triggered by silver cyanide formed in site. Also, we extended this approach to construct the nanoscrolls of the hexagonal boron nitride, molybdenum disulfide, and tungsten disulfide, respectively, from their corresponding two-dimensional nanomaterials. In a broader context, this approach paves a significant new way for the large production of the NSs with cost-efficiency. Since the discovery of graphene, the carbon nanoscrolls was convinced of deriving from scrolling of graphene, named as graphene nanoscrolls (denoted GNSs)4. GNSs inherit not only excellent properties of graphene, such as high mechanical strength, outstanding electrical conductivity, and superior carrier mobility but also possess open topological structure at both ends and interlayer galleries5. It endows the GNSs with wonderful features, such as excellent electronic and electromechanical properties7. Thus, the GNSs have significant potential applications in energy storages, photovoltaic cells and sensors10. Besides graphene, recently it was reported that the other layered two-dimensional nanomaterials (denoted 2DNMs) could be rolled into the nanoscrolls (denoted NSs) too, such as h-boron nitride (h-BN), tungsten disulfide (WS2), and molybdenum disulfide (MoS2)11. The NSs have become a new type of one-dimension nanomaterials with novel properties. Therefore, the preparation of the NSs has attracted increasing attention of scientific researchers. However, most of the research work is limited to theoretical prediction and calculation15. Only a few previously published articles involved fabricating the NSs. Moreover, the reported processes are complicated, and the conversion yield is tiny limiting their application23. Up to date, there is no general and efficient method to enable assembling the NSs with high-yield.Carbon nanoscrolls were discovered when making multiwalled carbon nanotubes2, and WS2 by verifying the morphology and structure of the formed NSs using scanning electron microscope, transmission electron microscope, Raman spectra, and X-ray diffraction spectra. Also, the mechanism of the self-assembly scrolling processes is elucidated.Herein, we report a facile and general approach for production of high-quality NSs with high-yield from two-dimensional nanosheets. The NSs are fabricated via self-scrolling of the 2DNMs in the solution of silver nitrate and ethanol. We have demonstrated the formation of the nanoscrolls of graphene, h-BN, MoS3 ethanol solution when they were mixed and magnetically stirred. After stirring the solution for some time, the grey dispersion gradually changed into a clear solution  and a transmission electron microscope (TEM) were applied to characterize the microstructure and morphology of the GNSs. The SEM image Fig.  indicate−1) and the shift of the 2D peak are often used to judge the layer number22. Accordingly, the graphene sheets which scrolled to the GNSs are a few layer numbers which are agreement with the results characterized by TEM and AFM shown in Fig. 25.Raman spectrum is an excellent way to characterize the structure of the nanostructured materials. Comparing the Raman spectrum of the graphite, the graphene, and the GNSs shown in Fig. In order to explore the conversion process of the graphene to the GNSs, we have examined the change of the morphology and structure of the graphene with the reaction period via the SEM characterization. Figure 2, and WS2 to explore its generality. The SEM images , AgNO3 were purchased from Sinopharm Chemical Reagent Co., Ltd (China). Carbon dioxide (99.9%) was obtained from Shanghai high-tech Co., Ltd (China).Graphite powder was purchased from Sinopharm Chemical Reagent Co., Ltd (China). H-BN bulk powder was obtained from Strem Chemicals. The MoS2, and WS2 were exfoliated using a shear mixer in a supercritical CO2 approach similar to the previously reported paper26. The 1 g raw material was put into the reactor, and carbon dioxide was pumped into the reactor by the manual pump. When the pressure and the temperature reached a preset value of 12 MPa and 45 °C, the shear mixer was started and remained at a speed of 3000 r/min for 1 hour. The resultant sample was dispersed by an ultrasonic water bath and centrifuged. More than 80% of the exfoliated 2DNMs were confirmed to be 1 to 5 layers by AFM, TEM and Raman spectra.Graphene, h-BN, MoS3 was dispersed in ethanol solvent in a predefined mass ratio. When the dispersion was magnetically stirred for 30 min at room temperature, the 2DNMs rolled up and deposited as shown in Figs A certain amount of the exfoliated 2DNMs and AgNOScanning electrode microscope imaging was performed using an FEI Nova NanoSEM 450 (USA). Transmission electron microscope images were obtained using JEOL JEM-2100 TEM (Japan) at an acceleration voltage of 120 kV. The X-ray diffraction (XRD) recorded on a BRUKER D8 Advance X-Ray Diffractometer (Germany) using a Cu Kα radiation source (λ = 1.5418 Å). The Raman spectroscopy was recorded on a Raman Microscope excitation (USA) with a wavelength of 532 nm. Zeta Potential was performed with a Malvern Instruments ZS90 Particle Size and Zeta Potential Analyzer (UK).Supplementary Information