Stabilization of Gas Bubbles Released from Water-Soluble Carbohydrates Using Amphiphilic Compounds: Preparation of Formulations and Acoustic Monitoring of Bubble Lifetime
The ultrasound contrast agents Echovist® and Levovist® (Bayer AG, Schering AG, Germany) are based on the release of gas bubbles from milled α-d-galactose. In diagnostic ultrasound, for this class of contrast agents, there is a need for prolonged contrast duration. To investigate if new carbohydrate compositions could prolong the lifetime of the gas bubbles, α-d-galactose was mixed with other carbohydrates or amphiphiles with varying log P. Acoustic attenuation vs. time (390 s) area under the curve (A390) and bubble half-time (t½) were used as measures of prolonged lifetime of gas bubbles. The products, to which 0.1% of a lipophilic carboxylic acid (5β-cholanic acid, behenic acid, and melissic acid) has been added, showed more than 5, 7 and 11 times enhancement of A390, respectively, compared with the reference compound 2 (RC2) corresponding to the commercial product Levovist®. The half-time t ½ of the same compounds was prolonged more than 6 times compared with RC2. A partial least square (PLS) statistical analysis confirmed that, for additives, high log P carboxylic acids lead to the highest A390. The present results bear a promise of products with a more persistent in vivo ultrasound contrast effect than the commercially available agents.
Design and Analysis of Hydrogel Sensors for the Quantification of Vitamin D Using Ultrasound Spectroscopy
The role of vitamin D in patient health and well-being has become an area of great interest and concern as studies uncover conditions and issues related to deficiency. It is well established that vitamin D plays a major role in the formation and maintenance of bone structure through the regulation of calcium and phosphate levels in the blood. Recently, studies have shown that vitamin D plays a much larger role in patient health. Recognition sites for vitamin D have been found in soft tissue regions throughout the body, indicating that tissues other than bone are affected by vitamin D status. Recent studies also suggest that long-term deficiency of vitamin D is linked to several autoimmune diseases including type 1 diabetes and multiple sclerosis. Currently, one of the major issues hindering productive research in vitamin D deficiency studies is the lack of a reliable, routine measurement method. International vitamin D measurement comparison studies (such as DEQAS) indicate that measurement variations exists among modern methods for quantifying vitamin D. For these reasons, it is critical to establish a practical method for obtaining reliable vitamin D measurements. The development of rapid clinical and inline measurement techniques for the analysis of complex chemical systems has become an area of great interest in analytical research. Ideal protocols make quick and accurate measurements while using inexpensive reagents and low-cost instrumentation. There are several measurement challenges that can inhibit many of the current spectroscopic techniques from effectively quantifying certain sample matrices. Highly scattering media such as suspensions, tissue, blood, serum, and other biological fluids are difficult to analyze using conventional optical strategies. Extensive
PH-dependent appearance of chiral structure in a langmuir monolayer
) acid monolayer with cadmium ions inthe subphase, at near-zero surface pressure and˘9 °C, show that there exists a pH “window” within whichthe monolayer takes on a chiral structure and an ordered superlattice is also observed. Below this pH window,the monolayer has a tilted structure like that of a pure fatty acid monolayer at low pressures, indicatingnegligible headgroup-ion interaction. Above the window, the monolayer goes to a structure very similar tothe high-pressure untilted S phase seen in pure fatty acid monolayers. The chiral structure is never seen whencadmium is replaced by zinc, another divalent metal with only slightly lower electronegativity, or (as reportedearlier) with calcium. Raising temperature within the cadmium pH window destroys the superlattice andtakes the monolayer to the backbone-disordered Rotator-I structure.