Spherical hydrophilic microparticles obtained by the radical copolymerisation of functionalised bovine serum albumin

Unsaturated groups wereintroduced onto proteins in order to produce macromers that are able to undergo radical polymerisation.The initial protein used was bovine serum albumin (BSA) because it is biodegradable, biocompatible and easily available. Methacrylic groupswere introduced onto BSA byreaction with methacrylic anhydride at controlled pH and temperature. The experimental conditions allowed the protein to be kept water-soluble. This water-solubility of the derivatised protein wasessential when realising spherical polymeric microparticles via reversephase suspension copolymerisationwith N,N-dimethyacrylamide(DMAA). During the derivatisation, the insertion of the polymerisable groups affects only the sterically-available chemicalfunctions of the native protein. Therefore, chain growth during thecopolymerisation process involves only these groups, achieving a polymeric network around a structurally unmodified protein.The polymeric systems show high water affinity, ascribable to the hydrophilic properties of BSA. We have demonstrated that the achievement of the spherical form during the polymerisation dependson two factors: the degree ofderivatisation of BSA, and theweight/weight (w/w) ratio of the protein to the comonomer. The beads obtained were characterised by Fourier transform IR spectrophotometry, particle size distribution analysis, and scanning electronmicroscopy (SEM). The samplesinvestigated showed a remarkable affinity for water and a high swelling capacity. These properties depend upon the degree of derivatisation of BSA and on the percentage of DMAA in the copolymerisation mixture. In this paper we describe the starting materials and the experimental conditions used to prepare protein hydrogels by radical copolymerisation, which are intended for use inpharmaceutical and biomedicalapplications.