A mild route to entrap papain into cross-linked PEG microparticles via visible light-induced inverse emulsion polymerization

Abstract

Entrapment of enzymes into a cross-linked network is an effective way to enable their recycling. In order to obtain a satisfied recovery of enzyme activity, a mild encapsulating condition is highly required due to the delicate nature of enzymes. Herein, a facile and mild visible light-induced inverse emulsion polymerization technique was developed for in situ entrapment of enzyme. In this method, poly (ethylene glycol) diacrylate (PEGDA) was dissolved in phosphate buffer saline and used as disperse phase, while continuous phase was composed of liquid paraffin, photoinitiators (isopropylthioxanthone and ethyl 4-dimethylaminobenzoate) and emulsifier (Span 80 and Tween 80). Under the irradiation of visible light, PEGDA could be cross-linkedly polymerized and formed microparticles with diameter ranged from 0.75 to 6.5 μm. When the glutaraldehyde cross-linked papain was added into disperse phase, it could be in situ entrapped into the microparticles after the visible light-induced inverse emulsion polymerization. The immobilized papain exhibited higher activity in a wide range of temperature and pH than free papain. Moreover, the immobilized papain could maintain 60% of its initial activity even after ten cycles of usage. This simple and mild strategy to in situ entrapment of enzymes has potential application in fields such as biocatalyst, biosensor and drug delivery.