Polymer gel matrix

Distinction is also made among electrophoretic techniques in terms of the type of matrix employed for analysis. Matrices include polymer gels such as agarose and polyacrjiamide, paper, capillaries, and flowing buffers. Each matrix is used for different types of mixtures, and each has unique advantages. 

Concerning drug delivery, electrically erodible polymer gels for controlled release of drugs have been prepared, and a measured release rate of insulin has been observed under electrical stimulus [69]. A suspension of zinc insulin in a mixed solution of poly(ethyloxazoline) and PMAA was formed into a gel by decreasing the pH of the suspension. The obtained complex gel with 0.5 wt% of insulin was attached to a woven platinum wire cathode which was 1 cm away from the anode and immersed in 0.9% saline solution. When a stepped function of electrical current of 5 mA was applied to the insulin-loaded gel matrix, insulin was released in a stepwise manner up to a release of 70%. The insulin rate measured was 0.10 mg/h. 

This process involves the suspension of the biocatalyst in a monomer solution which is polymerized, and the enzymes are entrapped within the polymer lattice during the crosslinking process. This method differs from the covalent binding that the enzyme itself does not bind to the gel matrix. Due to the size of the biomolecule it will not diffuse out of the polymer network but small substrate or product molecules can transfer across or within it to ensure the continuous transformation. For sensing purposes, the polymer matrix can be formed directly on the surface of the fiber, or polymerized onto a transparent support (for instance, glass) that is then coupled to the fiber. The most popular matrices include polyacrylamide (Figure 5), silicone rubber, poly(vinyl alcohol), starch and polyurethane. 

In order to act as a transducer optode must be attached to the optical fiber. Bulks (>1 mm) of sol-gel matrix can be easily glued to the fiber tip, especially, if the polymer fiber is used39. The smaller optodes can be attached to fiber end by dip-coating method or simply by direct painting of the fiber-tip with a liquid gel. 

Dynamic probe methods Another indirect strategy for emalysis of gel structure is the measurement of the mobility of dynsumic probes whose sizes are well characterized. For example, dynsumic light scattering or any other method for diffusivity determination (for examples, see 37) can be used to measure the motions, through a gel matrix, of a series of spherically shaped particles with varying sizes. To oversimplify greatly, if, as probe size is raised, a dramatic decrease in diffusivity is found, then the "mesh" size of the polymer gel may be estimated. 

In this paper we have immobilized an enzyme within a thermally reversible hydrogel. Immobilized enzymes have been used in a variety of applications, ranging from treatment of diseases to sensors, assays, and industrial processes (15-20). When an enzyme is immobilized within a gel which exhibits reversible shrinking and swelling as the ten rature is raised and lowered through the LCST of the gel matrix polymer, the enzyme may be switched off and on as the substrate diffusion rate is regulated by the gel pore size (5). In adcfition to enzymes, a variety... 

An early example of an MIP-QCM sensor was a glucose monitoring system by Malitesta et al. (1999). A glucose imprinted poly(o-phenylenediamine) polymer was electrosynthesized on the sensor surface. This QCM sensor showed selectivity for glucose over other compounds such as ascorbic acid, paracetamol, cysteine, and fructose at physiologically relevant millimolar concentrations. A unique QCM sensor for detection of yeast was reported by Dickert and coworkers (Dickert et al. 2001 Dickert and Hayden 2002). Yeast cells were imprinted in a sol-gel matrix on the surface of the transducer. The MIP-coated sensor was able to measure yeast cell concentrations in situ and in complex media. A QCM sensor coated with a thin permeable MIP film was developed for the determination of L-menthol in the liquid phase (Percival et al. 2001). The MIP-QCM sensor displayed good selectivity and good sensitivity with a detection limit of 200 ppb (Fig. 15.7). The sensor also displayed excellent enantioselectivity and was able to easily differentiate the l- and D-enantiomers of menthol. 

Chakraborty I, Moulik SP (2004) Preparation and characterization of nanoscale semiconductor particles of ZnS, CdS, and PbCr04 in polymer-surfactant gel matrix. J Dispers Sci Technol 25 849-859... 

Four methods have been developed for enzyme immobilization (1) physical adsorption onto an inert, insoluble, solid support such as a polymer (2) chemical covalent attachment to an insoluble polymeric support (3) encapsulation within a membranous microsphere such as a liposome and (4) entrapment within a gel matrix. The choice of immobilization method is dependent on several factors, including the enzyme used, the process to be carried out, and the reaction conditions. In this experiment, an enzyme, horseradish peroxidase (donor H202 oxidoreductase EC 1.11.1.7), will be imprisoned within a polyacrylamide gel matrix. This method of entrapment has been chosen because it is rapid, inexpensive, and allows kinetic characterization of the immobilized enzyme. Immobilized peroxidase catalyzes a reaction that has commercial potential and interest, the reductive cleavage of hydrogen peroxide, H202, by an electron donor, AH2 ... 

Together with the primary secretory products (enzymes, hormones, neurotransmitters, etc.) secretory granules contain a pair of countercharged chemical moieties a polyanionic polymer matrix, and a cation or polycation. These countercharged pairs, which are found ubiquitously inside different types of secretory granules, gave us the first clue that a polymer gel phase transition -... 

Fig. 3. Polymer gel phase transition of the mucin polymer matrix of a giant secretory granule of the terrestrial slug Ariolimax columbianus. Effect of pH...

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