pH-sensitive hydrogel based on a polyaspartamide derivative

A pH-sensitive hydrogel was prepared by UV irradiation technique. Starting polymer was obtained from alpha,beta-poly (N-2-hydroxyethyl)-DL-aspartamide (PHEA) partially derivatized with glycidyl methacrylate (PHG). The PHG copolymer was cross-linked by UV irradiation in the presence of methacrylic acid (MA) to form a pH sensitive hydrogel. The cross-linked matrix shaped as microparticles was characterized by FT-IR spectrophotometry, XPS, X-ray diffraction, SEM and particle size distribution analyses. Moreover, to have information about water affinity of the prepared sample, swelling measurements were carried out in aqueous media mimicking some biological fluids. In order to employ the prepared network as a pH-sensitive drug delivery system, propionyl-L-carnitine, chosen as a model drug, was entrapped into this hydrogel both during the irradiation process and after cross-linking reaction by a soaking technique. In vitro release studies showed that the drug release rate depends on the different swelling of the network as a function of the environmental pH as well as on the different drug loading method