New Bioartificial Polymeric Material: Poly(ethylene glycol) Cross-Linked with Albumin. I. Synthesis and Swelling Properties

A new family of translucide hydrogels obtained by cross-linking of bifunctionalized poly(ethylene glycol) (PEG) of various molecular masses (M, 2,000 to 35,000) with an albumin protein, namely bovine serum albumin (BSA), is described. The composition and the structure of these hydrogels have been investigated on the basis of the molar ratio of reagents, and through measurements of PEG and BSA released during washing and swelling steps. It appears that an excess of activated PEG is required in the reaction mixture to allow the gel formation with PEG of molecular mass ranging from 3,350 to 10,000. Above these M r of PEG, smaller amounts of PEG are needed to carry out the gel formation. Experimental results suggest that the cross-link density decreases when the molecular mass of PEG increases. These hydrogels are characterized by a very high swelling ability with equilibrium water contents (EWC) ranging from 96.6 to 97.5% in distilled water containing NaN 3 at 0.02% (w/v). The swelling factors (SF) ranged from 14 to 40 according to the incuba tion medium and to the PEG molecular mass involved. The swelling rates increased with increasing PEG molecular mass used to synthesize the hy drogel. This family of hydrogels possesses a good porosity since diffusion of bovine serum albumin out of the hydrogel network was observed in a long-term period.