Thermoresponsive Hydrogels from BSA Esterified with Low Molecular Weight PEG

Bovine serum albumin (BSA) and low molecular weight polyethylene glycol (PEG) were reacted in a single-step reaction to synthesize translucent hydrogels with a sol-gel transition at temperatures between 37 and 40 degrees C. Gelation occurred by aggregation of smaller assemblies of BSA-PEG precursors within minutes. The sol-gel transition concentration depended on the molecular weight of PEG only at temperatures below 35 degrees C; above 45 degrees C phase separation occurred and a precipitate formed. Microscopic examination showed the porous structure of the gels. At a fairly low grafting ratio, BSA preserved its native secondary and tertiary structure and maintained its capability for binding and enclosing small molecules. Drug delivery was assessed by a discontinuous method in vitro using 5-fluorouracil. Degradation tests with trypsin confirmed that the hydrogels were biodegradable. This novel material holds promise for biomedical applications as potentially injectable drug delivery vehicle. (C) 2014 Wiley Periodicals, Inc.