Suspension polymerization of poly(ethylene glycol) methacrylate: a route for swellable spherical gel beads with controlled hydrophilicity and functionality

Spherical and swellable gel beads were obtained by the suspension polymeriz ation of poly(ethylene glycol) methacrylate macromonomer (PEG-MA). The aver age size and size distribution properties, the equilibrium swelling behavio ur and the protein adsorption characteristics of PEG-MA-based gel beads wer e determined. In the suspension polymerization system, the organic phase in cluding monomer, crosslinker and diluent solution was dispersed in an aqueo us medium by using poly(vinylpyrrolidone) as the stabilizer. The diluent so lution was prepared by mixing cyclohexanol and octanol at different volume ratios. The suspension polymerization experiments were designed in two sepa rate parts. In the first part, ethylene glycol dimethacrylate was selected as the cross-linker and swellable PEG-MA-based gel beads were obtained by c hanging the cross-linker concentration, the monomer/diluent ratio and the s tirring rate. In the second part, a more hydrophobic structure, divinylbenz ene (DVB) was tried as a cross-linker. In this part, PEG-MA-DVB copolymer b eads were obtained by changing the DVB,PEG-MA feed ratio. Then, the hydroph icility of the resulting gel beads could be controlled by changing the feed ratio of hydrophilic macromonomer to hydrophobic cross-linker. This proper ty was also used to control the extent of nonspecific protein adsorption on to the surface of the gel beads. The non specific albumin adsorption onto t he gel beads decreased with increasing PEG-MA content. No significant nonsp ecific adsorption at the isoelectric point of albumin was detected onto the gel beads produced with the higher PEG-MA/DVB feed ratios. For specific al bumin adsorption, a triazinyl dye (i.e., cibacron blue, CB F3G-A) was coval ently attached onto the surface of the copolymer beads via terminal hydroxy l groups of PEG-MA. The results of albumin adsorption experiments with the CB F3G-A carrying beads indicated that an appreciable specific albumin adso rption capacity could be obtained with the gel beads produced with a PEG-MA /DVB feed ratio of 1.5/4.0.