Microparticle sensor from microparticles

Figure 5. Microparticle Sensor Design. In this design, microparticles release reagent into a polyacrylamide layer, reacting with analyte that has diffused in from the bulk solution.

Figure 6. Cumulative Release of HPTS from EVA Microparticles. Sensors were fabricated and soaked in pH 7.8 phosphate buffer. The release of HPTS from microparticles entrapped in polyacrylamide on sensor tips was monitored by measuring the increase in fluorescence intensity over 300 hours.

Figure 10. Proposed Adaptation of a Fluorescence Energy Transfer Immunoassay to the Microparticle Sensor Design. A mixture of two different microparticles, each containing different reagents, are entrapped physically in the polyacrylamide layer. The reagents released from the microparticles set up a competition reaction between the free and labeled antigens for the available binding sites of labeled-antibody. The immunocomplexes formed have different emission spectra, allowing quantitation of free antigen concentration.

Time-of-flight (TOF) measurement is popular in microflow measurements. The time of flow of a pulse of temperature or of molecular tracers from one point in a microchannel to another point is characterized to measure the flow rate. An emitter and a collector are integrated into TOF sensors. Various optimizations of these sensors have been carried out, using temperature pulses or electrochemical production of molecular tracers. These sensors calculate the flow rate at one point in the cross section of the channel and are calibrated with a known flow rate. Flow measurementusing microparticles captures the velocity profile at many such locations in the channel cross section and allows one to calculate the flow rate. Figure 4 shows the principle of a flow sensor using a CFD simulation of convective diffusion... 

MWCNT electrodes have been developed to monitor the electrochemical oxidation of insulin, a pancreas-produced hormone that plays a key role in the regulation of carbohydrates and fat metabolism in the body. This provides a possible method to evaluate the quality of pancreatic islets before their transplantation. By coating similar MWCNT electrodes with platinum microparticles, thiols containing amino acids can be detected in rat striatal that is the subcortical part of the fore-brain. CNT-based sensors can be incorporated into flexible biocompatible substrates to facilitate in vivo sensing. For instance, free cholesterol in blood can be measured using MWCNT electrodes placed on a biocompatible substrate whereas flexible pH sensors can be formed from polyaniline (a conductive polymer) and nanotube composites. ... 

A variety of different formulations for controlled release polymers exist including microparticles, microcapsules and microspheres. Microparticles range in size from 1-200 pm, while particles with a diameter smaller than 1 pm are called nanoparticles. Microcapsules are microparticles which have the substance of interest enclosed in a shell of degradable polymer. Microcapsules however are characterized by a relatively fast release of large amounts of the enclosed substance. Microspheres (Figi 1), on the other hand, are monolithic in structure, Le. have the substance unifomdy distributed within the polymer layer. This distribution results in a more uniform release over longer periods of time. We selected such microspheies prepared from poly(lactide-glycolide) copolymers to develop our sensors. 

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