the invention provides a carrier for carrying radioactive substances , wherein phycoerythrin is served as a carrier for carrying radioactive substances and enables radioactive substances to accumulate specifically in the tumor cells . according to the results of this invention , phycoerythrin , which exists exclusively in microalgae , has high affinity to tumor cells and selectively accumulates therein while does not stay in normal cells . therefore , the present invention applies the special feature of phycoerythrin to cancer treatment by using phycoerythrin as a carrier for carrying radioactive substances . another objective of the invention is to provide a method for introducing radioactive substances into and killing of tumor cells by using phycoerythrin as a carrier , comprising the steps of providing phycoerythrin ; conjugating phycoerythrin with the radioactive substances to be carried ; introducing the radioactive substances - carried phycoerythrin into tumor cells ; accumulating the radioactive substances in forgoing tumor cells ; and killing tumor cells by the radiation emitted from radioactive substances carried by phycoerythrin . iodine , an example of general radioactive substances , possesses the ability to react with proteins and can bind to tyrosine efficiently , and is also one of the common radioactive elements for medical use . accordingly , one example of the present invention chooses radioactive iodine to be carried by phycoerythrin and be introduced to the tumor cells . by using the ability of beta radiation emission of radioactive iodine , the tumor cells are killed efficiently and specifically without damaging normal cells . furthermore , the foregoing phycoerythrin can be introduced into tumor cells in an effective amount . and by irradiating with specific light source , phycoerythrin is induced to emit fluorescence at a specific wavelength so that the localization and range of tumor can be determined . the foregoing phycoerythrin can be r - phycoerythrin ( r - pe ) or b - phycoerythrin ( b - pe ), wherein the r - phycoerythrin is more preferable . r - phycoerythrin is a water - soluble , fluorescent pigment protein existed exclusively in algae . the major physical and chemical properties of r - phycoerythrin are as follows : its structure consists of three types of subunits , α - β and γ , which usually appear in hexamer form of ( αβ ) 6γ . the molecular weight of r - phycoerythrin is 260 , 000 daltons . the absorption spectrum , as in fig1 a , shows the primary absorbance peak at 566 nm with a secondary peak at 498 nm . the fluorescence emission spectrum , as in fig1 b , shows the peak of the fluorescence wavelength is at 575 nm with the maximum excitation wavelength being 488 nm , at which the fluorescence quantum yield is 0 . 84 . the major physical and chemical properties of b - phycoerythrin are as follows : its structure consists of three types of subunits , α - β and γ , which usually appear in hexamer form of ( αβ ) 6γ . the molecular weight of r - phycoerythrin is 240 , 000 daltons . the range of absorption wavelength lies within the visible light . the absorption spectrum , as in fig2 ( solid line ), shows the primary absorbance peak at 545 nm with a secondary peak at 498 nm . the range of fluorescence emission wavelength lies within the visible light . the fluorescence emission spectrum , as in fig2 ( dashed line ), shows the peak fluorescence wavelength is at 575 nm . the fluorescence is strong and stable with little influenced by environmental ph value , temperature and existence of other biomoleculars . the maximum excitation wavelength is 543 nm , at which the fluorescence quantum yield is 0 . 98 . the term ‘ tumor cells ’ used herein refers to all types of tumor cells without specific limitation , and the doses of phycoerythrin to be treated can vary depending on the type of tumor cells . the following is a detailed description of the best presently known modes of carrying out the inventions . this description is not to be taken in a limiting sense , but is made merely for the purpose of further illustrating the present inventions . the specification information of r - phycoerythrin is as follows : 1 . the absorbance ratio : a 566 / a 280 ≧ 5 . 3 ; a 566 / a 498 ≦ 1 . 5 ; a 620 / a 566 ≦ 0 . 005 . 2 . the purity of the protein is greater than 98 %. 3 . it is stored in 150 mm sodium phosphate buffer ( ph 7 . 0 ) containing 60 % saturated ammonium sulfate , 1 mm edta ( sodium ethylene - diaminetetraacetate ), and 1 mm sodium azide , and needs to be stored at 4 ° c . r - phycoerythrin is complete dialyzed with 150 mm sodium phosphate buffer , and then serial dilution is carried out by using mem medium as diluent to obtain the r - phycoerythrin dilutions of concentrations between 1 - 100 μg / ml . the tumor cells are human neuroblastoma cells , and normal cells for comparison are human fibroblast cells . first , cells are maintained in mem medium ( ph 7 . 4 ) supplemented with 10 % fetal bovine serum , and incubate at 37 ° c . and 95 % humidity . replace the mem medium every two days . when carrying out cell subculture , first remove the medium , and rinse the cells once with sodium phosphate buffer . then add 0 . 25 % trypsin - edta to detach the cells from the surface of petri dish , and stop the reaction of trypsin - edta by giving proper amount of foregoing mem medium , and thus the cell suspension is obtained . secondly , seed 100 , 000 to 400 , 000 cells onto cover slips placed in a 12 - well culture plate and incubate at 37 ° c . and 95 % humidity for 16 hours . following is the affinity test on r - phycoerythrin for human fibroblast cells ( normal cells ) and human neuroblastoma cells ( tumor cells ). take the 12 - well culture plate with cells growing on cover slips mentioned in step 2 . remove the medium and rinse the cells once with sodium phosphate buffer . add 1 ml of r - phycoerythrin dilutions mentioned in step 1 to the cells and follow with incubation at 37 ° c . and 95 % humidity . after 24 - hour incubation , remove the medium and rinse the cells three times with sodium phosphate buffer . then add 4 % of paraformaldehyde to each well of the culture plate and incubate at room temperature until the cells are completely fixed on cover slips . after washing once with sodium phosphate buffer , pick the cover slip up from the culture plate and embed the cells with 80 % glycerol . observe the staining by fluorescent microscopy . the results are shown in fig3 and fig4 . fig3 a shows fluorescence image of normal human fibroblast cells without adding r - phycoerythrin , while fig3 b , 3c , and 3 d show that of normal human fibroblast cells added with 10 μg / ml , 20 μg / ml , 40 μg / ml of r - phycoerythrin , respectively . the results show that no fluorescent signal is observed in human fibroblast cells , indicating that r - phycoerythrin does not accumulate in normal cells . [ 0039 ] fig4 a shows the fluorescence image of human neuroblastoma cells without adding r - phycoerythrin , while fig4 b , 4c , and 4 d show that of human neuroblastoma cells added with 10 μg / ml , 20 μg / ml , 40 μg / ml of r - phycoerythrin , respectively . the results show that the strength of fluorescence signal in human neuroblastoma cells is in accordance with the increasing amount of r - phycoerythrin ( see the bright area 1 as indicated in fig4 ), suggesting that r - phycoerythrin selectively retains in tumor cells . in conclusions , the present invention utilizes r - phycoerythrin in cancer radiation therapy as a carrier that effectively carries radioactive substances . by introducing effective amount of r - phycoerythrin into tumor cells as described in the best mode , the result demonstrates that : 1 . r - phycoerythrin can selectively accumulated within tumor tissues . 2 . when being exposed to specific light source ( at the wavelength ranging from 488 nm to 633 nm , wherein the ideal is at 488 nm ), r - phycoerythrin emits red fluorescence ( at the wavelength of 575 nm ), which facilitates determination the localization and range of tumor . 3 . by introducing r - phycoerythrin conjugated in advance with radioactive iodine enables killing of tumor cells via the beta radiation emitted from radioactive iodine .
the invention provides a carrier for carrying radioactive substances and methods for using the same , wherein phycoerythrin is served as a carrier for carrying radioactive substances so as to enable accumulation of radioactive substances specifically in the tumor cells and the radiation emitted therefrom kills the tumor cells effectively . therefore , the invention can be applied in the treatments for various types of cancers .