Polycarbonate, immobilization enzymes

Acetylcholineesterase Biosensors were fabricated from filter-supported solventless bilayer lipid membrane (BLM) and used for the analysis of the substrates of hydrolytic enzymes in a flowthrough system. The codeposition of lipid (dipalmitoyl-phosphatidic acid) and protein solutions to form a BLM on a microporous glass fiber or polycarbonate ultra-filtration membrane disc was described. Enzyme was immobilized on the membrane by incorporation of protein solution into the lipid matrix at the air-electrolyte interface before BLM formation. 

Mullen et al. (1986) decreased the permeability of LOD membranes in order to extend the linear range to higher lactate concentration. A polycarbonate membrane was treated with methyltrichlorosilane prior to enzyme immobilization by crosslinking with glutaraldehyde and BSA. In this way the upper limit of linearity was shifted from 0.2 to 18 mmolA. The permeation of electrochemical interferents was diminished concomitantly. On the other hand, the silanization increased the response time from 0.5-1 min to 1-3 min and reduced the sensitivity by 98-99%. 

Other lactate analyzers use lactate oxidase (LOD). Clark et al. (1984b) use the enzyme in the YSI23L instrument (USA) as immobilized between a cellulose acetate membrane and a polycarbonate membrane, the latter serving to exclude high-molecular weight interferents. Lactate measurement in whole blood pipetted immediately after withdrawal into the phosphate buffer stream of the analyzer yielded the following correlation with values obtained with deproteinized blood (Weil et al., 1986) ... 

An example of a sensor utilizing these three components is illustrated in figure 1.2, which shows a schematic of a typical enzyme electrode for the detection of glucose (also see chapter 17 of this text). The bioactive surface consists of immobilized glucose oxidase (GOD) sandwiched between a polycarbonate and cellulose acetate membrane. The transducer is a platinum electrode and the electronics are those typically found in any polarograph, i.e. an electronic system to measure low currents (on the order of microamperes) at a fixed voltage bias on the platinum electrode. The action of glucose... 

However, to our knowledge, most previous studies of enzyme-catalyzed polymerizations have avoided temperatures > 90 oC, which is likely due to thermal deactivation of enzyme catalyst (13-15). It has been found that enzyme immobilization can improve the stability and recyclablity of native enzyme (16). Silica particles, activated by methanesulfonic acid, are effective and economic inorganic carriers for enzyme immobilization (17). Herein, we present a minireview of our works about immobilized porcine pancareas lipase on silica particles (IPPL) for polymer synthesis, such as polycarbonates, polyesters, polyphosphates and their copoljmiers. 

One of the simplest possible applications of the LAPS/microflow chamber combination is the measurement of enzyme activity. One way to demonstrate this is to immobilize an enzyme in a chamber, and provide it with its substrate in the flow medium. As an example, let s consider acetyl cholinesterase, which catalyzes the hydrolysis of acetylcholine to acetate and choline, liberating protons in the process. Acetyl cholinesterase-coated agarose beads (Sigma) were immobilized between two thin polycarbonate membranes in a Cytosensor [4] chamber, and the pH response measured when an acetylcholine-containing medium is flowed through. Figure 5 shows the data from this experiment. Rates of about 120 pV/s are obtained. Note that the presence of the membranes slows down the time constant of the return to baseline of the pH during the flow-on periods. This demonstrates the measurement of enzyme activity, with possible applications to immunoassays. 

Enzymatic polymerization has emerged in the last few decades as a field of considerable interest and commercial promises. It proceeds with high regio-, enantio-, and chemos-electivity under relatively mild conditions. So far, enzymes have been used to synthesize polyesters, polysaccharides, polycarbonates, polyphenols, polyanilines, vinyl polymers, and poly(amino acid)s. Namely, the lipase B of Candida antarctica (Cal-B, a serine hydrolase) immobilized on polyacrylic resin (Novozyme 435) has proven to be a very versatile catalyst in terms of reaction conditions and acceptance of various substrates. For example, this enzyme has been successfully used to synthesize polyesters. ° However, little has been reported so far on the synthesis of polyamides catalyzed by enzymes. " ... 

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