ABSTRACT
The medical diagnostic, the industry, and the biotechnology require rapid, sensitive, and easy to use methods for trypsin activity determination. A simple approach, which meets all these requirements, based on Quartz Crystal Microbalance (QCM) was developed, analytically characterized and described in the present work. QCM application allows rapid trypsin activity evaluation by real time monitoring of the enzymatic degradation of the substrate. The new approach suggested in this work takes advantage of nanoparticles loaded gelatin employment as a trypsin substrate, deposited on the QCM crystal. The heavy nanoparticles leave the substrate layer together with the products of its enzymatic degradation provoking thus a greater decrease of the total QCM crystal mass compared with the non charged substrate. As a result, a higher sensor frequency response occurs. A 10 fold improvement of the LOD was achieved for trypsin activity evaluation applying the proposed method with Ag nanoparticles loaded gelatin (7.5×10(-4) U mL(-1) vs. 7.5×10(-3) U mL(-1) obtained by the "classic" QCM method). The approach subject of this work can be applied with any substrate degrading enzyme.
Subject(s)
Biosensing Techniques/instrumentation , Micro-Electrical-Mechanical Systems/instrumentation , Nanoparticles/chemistry , Nanotechnology/instrumentation , Silver/chemistry , Trypsin/analysis , Trypsin/chemistry , Enzyme Activation , Equipment Design , Equipment Failure Analysis , Nanoparticles/ultrastructure , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
The purpose of this study was to assess the G-tolerance and G-induced changes in plasma renin activity (PRA), serum cortisol, testosterone, thyroid hormones and blood concentrations of serotonin and histamine. Experiments were performed on 26 student pilots aged 22.7 +/- 0.7 years using simulated aerial combat manoeuvres (SACM) in a centrifuge with radius 7.5 m. G-tolerance was assessed by loss of vision criteria, G-induced loss of consciousness and significant disturbances in heart rhythm. PRA, cortisol, testosterone and thyroid hormones were measured by radioimmunoassay, serotonin and histamine by spectrofluorimetric methods 24 hours before and 5 min after SACM. The statistical significance of hypergravitation and G-tolerance were determined by ANOVA. We found a significant increase in PRA (p = 0.001) and thyroxine concentration (p = 0.005) after hypergravitation loads. It is known that these changes are indicative for cardiovascular adaptation and enhancement of energy mobilization. Histamine levels differed significantly by G-tolerance (p = 0.031), while serotonin concentrations changed by hypergravitation (p = 0.004). Significant dependence on hypergravitation x G-tolerance was found for serotonin values (p = 0.024). Studying G-induced hormonal changes can reveal individual peculiarities in G-tolerance, a limiting factor for the exploitation of high performance aircraft.
