Enhanced catalytic activity of new acryloyl crosslinked cellulose dialdehyde-nitrilase Schiff base and its reduced form for nitrile hydrolysis.

Immobilization of enzymes to improve their catalytic properties is an attractive protocol which makes them suitable candidates to meet various industrial demands. Present study describes the synthesis of new acryloyl crosslinked cellulose dialdehyde (ACCD) for nitrilase immobilization. Nitrilase was immobilized onto ACCD via Schiff base formation i.e. imine linkages (-CH=N-). Effect of different operational parameters viz. temperature, pH and substrate concentration on the free and the immobilized nitrilases were evaluated by hydrolysis of mandelonitrile. Immobilization resulted into enhanced catalytic activity of nitrilase under different operating conditions of temperature and pH. The optimum temperature and pH for immobilized forms of nitrilase was obtained to be 55 °C and 8.0 which was higher than its free form (40 °C, 6.0). Immobilized nitrilase also exhibited good thermal and storage stability over the free form and is reusable up to sixteen repeat cycles with an appreciable retention activity.

New glucose oxidase-immobilized stimuli-responsive dextran nanoparticles for insulin delivery.

Designing strategies for the use of biopolymer-based nanoparticles as drug delivery carriers is a considerable challenge in pharmaceutical science. Present study reports synthesis of a novel glucose responsive and in-vitro pH triggered insulin delivery system comprised of glucose oxidase immobilized on acryloyl crosslinked dextran dialdehyde (ACDD) nanoparticles. Scanning electron microscopy, transmission electron microscopy and particle size analysis data revealed that these carriers possess nanosize which is an important parameter for drug delivery applications. In-vitro insulin release studies were performed under artificial gastric fluid (AGF, pH 1.2) and artificial intestinal fluid conditions (AIF, pH 7.4) at physiological temperature (37 °C). Insulin release profile showed controlled release of about 70% under AIF conditions for 24 h. Insulin release mechanism studied using different kinetic models revealed that Korsmeyer-Peppas model appropriately explained the mechanism as 'non-Fickian' diffusion release of insulin. These glucose responsive stimuli sensitive nanocarriers exhibited controlled release of about 90% under AIF conditions in the presence of glucose. These findings revealed that these nanoparticles are promising and reliable delivery systems to overcome problems related with subcutaneous insulin therapy.

Functionalized Polyacrylonitrile Nanofibrous Membranes for Covalent Immobilization of Glucose Oxidase.

Nanofibrous membrane (NFM) with uniform morphology and large surface area was prepared from 10% solution of polyacrylonitrile (PAN) in N,N-dimethylformamide by electrospinning technique. NFM was chemically modified for use as a support for the immobilization of glucose oxidase. Chemical modification of NFM was carried out by two different methods. In the first method, the cyano groups of PAN were modified to amino groups by a two-step process, while in the second method the carboxylic groups were generated first and then further reacted with hexamethylene diamine to create a reactive spacer arm for the immobilization of enzyme. Scanning electron microscopy studies showed that the surface morphology of NFM was not changed by chemical modification and its mechanical strength was improved. The immobilized glucose oxidase (GOx) retained 54 and 60% of its original activity up to 25 cycles with the PAN NFMs modified by the first and the second method, respectively. The GOx-immobilized NFM from the second method showed promising performance with higher enzyme immobilization, activity retention, and favorable kinetic parameters.