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We explored a versatile enzyme nanoencapsulation process based on the synthesis of silica gel nanoparticles, decorated with a dense hydrophilic poly(glycerol monomethacrylate) (PGMMA) shell for biological and therapeutic applications. These hybrid enzyme-SiO2-polymer nanoparticles were obtained through an aqueous sol-gel process, followed by the adsorption of cationic macroinitiators by electrostatic complexation. Surface-initiated Atom Transfer Radical Polymerisation (ATRP) was applied to obtain a dense hydrophilic (protein repellent) PGMMA layer of tunable size, under conditions which are compatible with the nanoencapsulation of horseradish peroxidase. The sol-gel synthetic procedure, the composition and molecular weight of the macroinitiators, the polymer adsorption and purification methods, and the final ATRP conditions, were optimised to control the properties of these nanoparticles, in terms of particle size, Z-potential, PGMMA decoration, while preserving enzymatic activity.

The classical sol–gel synthesis of silica gels has been adapted to a W/O (micro)emulsion process under conditions that minimize denaturing effects on encapsulated enzymes. We have in particular focused on optimizing the purification procedures with the aim to produce water nanoparticles dispersions from W/O emulsions without the use of precipitation/sedimentation steps. A proof of principle of encapsulation has been conducted using horseradish peroxidase (HRP).