Immobilization Of Alcohol Dehydrogenase In Alginate Gel Doped With Nanotubes And Nanoparticles

Calcium alginate (ALG) gel is one of the most commonly used carriers in the entrapment immobilization of enzyme owing to their significant advantages such as good biocompatibility, low cost, easy availability, and simplicity of preparation. However, some disadvantages are often associated with this carrier, including high enzyme leakage, low mechanical strength, and serious swelling due to their open structure, large pore size. These disadvantages significantly restrict the lifetime of these enzymes immobilized in alginate gels and limit its further application.To overcome these disadvantages, in this paper, novel and efficient Organic-inorganic hybrid gels consisting of alginate gels doped with nanotubes or nanoparticles were prepared by incorporating nanotubes (carbon nanotubes, CNTs; silica nanotubes, SiNTs) and nanoparticles (silica gel, SG; graphite) into alginate gels. The hybrid alginate gel prepared in the present study included ALG-CNTs gel, ALG-SiNTs gel, ALG-SG gel and ALG-graphite gel. The structures and morphologies, chemical and physical properties of pure and hybrid alginate gels were evaluated by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDX), Fourier Transform IR spectrophotometer (FTIR), dynamic mechanical analysis (DMA) and BET nitrogen adsorption-desorption method. In addition, the diffusion characterisitics of NADH in pure and hybrid alginate gels were determined according an unsteady-state model. And characterization results showed that the mechanical properties of these hybrid gels were remarkably reinforced and effective diffusion coefficient for substrates were significantly increased.To deeply understand the effect of doping on the enzyme leakage, pure and hybrid alginate gels were firstly employed to encapsulate bovine serum albumin (BSA). During the encapsulation, first BSA was adsorbed on the dopants and then BSA and dopants were suspended in ALG solution, followed by Ca2+ cross-linking to form biocomposites. It was found that BSA leakage decreased significantly after immobilized in these hybrid alginate gels compared to that from ALG gel, which was mainly due to, firstly, the protein molecule was adsorbed on the dopants which could not be washed out easily, secondly, during the gel formation, water loss in hybrid alginate gels became less than that in pure alginate gel. And the BSA leakages in these gels occurred in the following order: ALG > ALG-graphite > ALG-SG >...