Swelling and protein absorption/desorption of thermo-sensitive lactitol-based polyether polyol hydrogels

A series of thermo-sensitive hydrogels has been prepared from reactions of acylated poly(ethylene glycol) bis(carboxymethyl) ether (PEGBCOCl) (M-n = 6 00 dalton) with lactitol-based polyether polyols (LPEPs). These LPEP hydrog els swelled extensively in water at neutral pH and their swelling behaviors depended strongly on the PEGBCOCl:LPEP molar ratios or extent of PEGBCOCl crosslinking. A maximum swelling of 81 fold was observed on hydrogels forme d with LPEP (M-n = 4055 dalton) at a PEGBCOCl:LPEP molar ratio of 4.25. At temperatures above 25 degrees C, the hydrogels exhibited a phase transition and collapsed, expelling water. These super-absorbent hydrogels were stabl e under acidic conditions, but were sensitive to base hydrolysis. Enzyme pr oteins, i.e. lipase, were incorporated in the hydrogels (0.4-1.2 mg/g) by i mmersing the collapsed hydrogels in the protein solutions at 25 degrees C. Protein desorption at 40 degrees C occurred rapidly with over 90% of protei n released during the first hour. The extent of protein desorption was simi lar among hydrogels with varying levels of absorbed proteins. The release o f the lipase protein molecules is due to the structural collapse of the hyd rogels and is not diffusion controlled. (C) 2000 Elsevier Science Ltd. All rights reserved.