Adsorption behavior and activity of horseradish peroxidase onto polysaccharide-decorated particles

The adsorption behavior of horseradish peroxidase (HRP) onto hybrid particles of poly(methylmethacrylate) (PMMA) and carboxymethylcellulose (CMC) was investigated by means of spectrophotometry. Dispersions of PMMA/CMC particles were characterized by light scattering, zeta potential measurements and scanning electron microscopy before and after HRP adsorption. HRP adsorbed irreversibly onto PMMA/CMC particles; the adsorption isotherm showed an initial step and an adsorption plateau. The enzymatic activity of free HRP and immobilized HRP (plateau region) was monitored by means of spectrophotometry as a function of storing time. Upon adsorbing HRP there is little (up to 20%) or no reduction of enzymatic activity in comparison to that observed for free HRP in solution. After storing free HRP and HRP-covered PMMA/CMC particles for 18 days the level of enzymatic activity is kept. HRP-covered PMMA/CMC particles dispersions, which were dried and re-dispersed, retained 50% of their catalytic properties. These interesting findings were discussed in the light of a beneficial effect of a hydrated microenvironment for maintenance of enzyme conformation and activity.