Lipoprotein lipase immobilization onto polyacrolein microspheres

Glucose oxidase immobilization on a novel cellulose acetate–polymethylmethacrylate membrane

Glucose oxidase (GOD) was immobilized on cellulose acetate-polymethylmethacrylate (CA-PMMA) membrane. The immobilized GOD showed better performance as compared to the free enzyme in terms of thermal stability retaining 46% of the original activity at 70 degrees C where the original activity corresponded to that obtained at 20 degrees C. FT-IR and SEM were employed to study the membrane morphology and structure after treatment at 70 degrees C. The pH profile of the immobilized and the free enzyme was found to be similar. A 2.4-fold increase in Km value was observed after immobilization whereas Vmax value was lower for the immobilized GOD. Immobilized glucose oxidase showed improved operational stability by maintaining 33% of the initial activity after 35 cycles of repeated use and was found to retain 94% of activity after 1 month storage period. Improved resistance against urea denaturation was achieved and the immobilized glucose oxidase retained 50% of the activity without urea in the presence of 5M urea whereas free enzyme retained only 8% activity.

Electrostatic immobilization of glucose oxidase in a weak acid, polyelectrolyte hyperbranched ultrathin film on gold: fabrication, characterization, and enzymatic activity

In this paper we show that hyperbranched polymers can be used as a host matrix for electrostatic entrapment of enzymes. Specifically, amine-functionalized glucose oxidase (GOx+) and horseradish peroxidase, as well as poly(amidoamine) dendrimer-modified horseradish peroxidase, reversibly sorb into polyanionic, hyperbranched poly(sodium acrylate) (PAA-) films that are on the order of a few hundred angstroms thick. The quantity of GOx+ entrapped within the PAA- films depends on the nature of film preparation but is typically on the order of 0.06 unit/cm2. The extent to which entrapped GOx+ retains its activity depends on the film history, but for PAA-/GOx+ composites not exposed to glucose and stored at 4 degrees C, the original activity is retained for up to 68 days and perhaps longer.

Immobilization of enzymes/coenzymes for molecular electronics applications

A brief survey of immobilization strategies and methods has been presented. Relative merits and demerits are discussed with reference to their end use.

Activation of human neutrophils by Arg-Gly-Asp-Ser immobilized on microspheres

The adhesive interaction of cells with extracellular matrix components is essential for a variety of cellular functions, and is frequently mediated by a tetra peptide, Arg-Gly-Asp-Ser (RGDS), located within fibronectin and other proteins. In this study, the RGDS-mediated activation of polymorphonuclear leukocytes accompanied by phagocytosis was investigated using monodisperse polymeric microspheres carrying RGDS. The parent and Arg-Gly-Glu-Ser (RGES)-carrying microspheres, which have no adhesion activity, were employed as controls. The ingestion of microspheres into PMN was not enhanced by immobilizing RGDS. However, PMNs exhibited unique oxygen consumption and enhanced liberation of reactive oxygen when RGDS-carrying microspheres were phagocytosed. These PMN responses disappeared with the addition of soluble RGDS. Furthermore, cytochalasin D, which inhibits actin polymerization, showed a marked inhibitory effect on oxygen consumption in the RGDS-carrying microsphere system, as compared with those in other systems. These findings show that RGDS-carrying microspheres induced the biospecific activation of PMNs by the signal transduction via RGDS-integrin binding without alteration in the degree of phagocytosis.

Spacer effects on enzymatic activity of papain immobilized onto porous chitosan beads

Papain was covalently immobilized onto the surface of porous chitosan beads without or with spacers of different lengths. The relative activity of the immobilized papain was found to be high toward a small ester substrate, N-benzyl-L-arginine ethyl ester (BAEE), but rather low toward casein, a high molecular weight substrate. Papain immobilized with spacer gave an almost constant activity, in marked contrast with the immobilized papain without spacer, whose activity monotonously decreased with decreasing surface concentration. The relative activity of the immobilized papain for hydrolysis of a high molecular weight substrate greatly depended on the length of the spacer. The pH, thermal and storage stabilities of the immobilized papain were higher than those of the free one, and ths papain immobilized directly to the chitosan beads' surface without any spacer gave a higher stability than those immobilized with spacer. The spacer's effect on the activity could be explained in terms of mobility of the immobilized papain molecule.

Synthesis of carboxylated poly(NIPAAm) oligomers and their application to form thermo-reversible polymer-enzyme conjugates

A thermo-reversible poly(N-isopropylacrylamide) poly(NIPAAm) oligomer with a carboxyl functional end group has been synthesized by radical polymerization using beta-mercaptopropionic acid as a chain transfer reagent. This polymer has been conjugated to an enzyme, beta-D-glucosidase, to form a thermo-reversible water soluble-insoluble polymer-enzyme conjugate. This conjugate can be used for separation, recovery and recycle of an enzyme simply by applying small temperature changes to the reaction medium. In contrast to the random polymer-enzyme conjugates reported in the literature, in this study the enzyme is coupled to each polymer chain by a single end attachment. These preliminary studies show that the conjugated enzyme exhibits very high retention of activity (> 90%) compared to the native enzyme and shows improved thermal stability.

Trypsin immobilization on to polymer surface through grafted layer and its reaction with inhibitors

Trypsin was covalently immobilized and physically adsorbed on to the surface of poly(ethylene terephthalate) fibres using poly(acrylic acid) (PAAc) chains grafted on to the ozonized fibres. The covalent immobilization was accomplished through amide formation between amino groups of trypsin and carboxyl groups of grafted PAAc chains, with the use of water-soluble carbodiimide. A set of samples with surface concentrations of grafted polymer ranging from 0.03 to 2.5 micrograms/cm2 was used to study the effects of grafted layer on the enzymatic activity of immobilized trypsin and its inhibition by trypsin inhibitors of different molecular sizes. The amount of immobilized trypsin increased linearly with an increase in graft yield of fibres, but the activity of immobilized enzyme reached saturation at a certain graft yield, probably because of diffusion limitation for the transport of enzyme substrate molecules into the grafted PAAc layer. The reduction of inhibition with an increase in graft yield and in molecular weight of inhibitors was attributed to enhancement of steric hindrance and enzyme inactivation in the dense grafted layer. We also found that the adsorbed trypsin was inhibited more easily than the covalently immobilized at any concentration of the grafted PAAc and for any type of inhibitor used.