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 pol yol) (LPEP). The average pK(a) value of hydroxyl groups of the polyol was 1 .63. Cross-linked hydrogels were synthesized by esterification with chlorin ated poly(ethylene glycol) bis(carboxymethyl) ether (PEGBCOCl). The swellin g 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 ra tio did not change significantly with pH in the range of 4-9. The release p rofiles of a model active agent, acetylsalicylic acid, from the hydrogels s howed that the diffusional release rate had a half-order dependence on time , and the diffusivity decreased with increasing cross-linking ratio. This w ork demonstrated that LPEP-based hydrogels can be used for controlled deliv ery of drugs and agrochemicals and the release rates can be controlled with the cross-linking ratio of the hydrogel.