Lactitol-based poly(ether polyol) hydrogels for controlled release chemical and drug delivery systems

The hydroxyl groups of lactitol were propoxylated to produce poly(ether polyol) (LPEP). The average pK(a) value of hydroxyl groups of the polyol was 1.63. Cross-linked hydrogels were synthesized by esterification with chlorinated poly(ethylene glycol) bis(carboxymethyl) ether (PEGBCOCl). The swelling ratio decreased with increasing cross-linking ratio (PEGBCOCl:LPEP) from 2:1 to 4:1 in the hydrogels and was sensitive to temperature change between 25 and 55 degreesC and concentrations of salt and glucose. The swelling ratio did not change significantly with pH in the range of 4-9. The release profiles of a model active agent, acetylsalicylic acid, from the hydrogels showed that the diffusional release rate had a half-order dependence on time, and the diffusivity decreased with increasing cross-linking ratio. This work demonstrated that LPEP-based hydrogels can be used for controlled delivery of drugs and agrochemicals and the release rates can be controlled with the cross-linking ratio of the hydrogel.