Photo-cross-linked biodegradable hydrogels based on n-arm-poly(ethylene glycol), poly(ε-caprolactone) and/or methacrylic acid for controlled drug release.

In this paper, a novel kind of photo-cross-linked biodegradable hydrogels based on n-arm-poly(ethylene glycol) ( n = 2, 3, and 4) and poly(ɛ-caprolactone) was prepared by ultraviolet-initiated free radical polymerization. The resulting n-arm-poly(ethylene glycol)-poly(ɛ-caprolactone) and n-arm-poly(ethylene glycol)-poly(ɛ-caprolactone) acrylate (n-arm-PEG-PCL-AC, macromer) were characterized by proton nuclear magnetic resonance and fourier transform infrared spectra. The influences of arm numbers and concentration of macromer on the properties of hydrogel were researched systematically, and the results showed that the gelation time, equilibrium swelling ratio, in vitro degradation, and drug release rate decreased with the increase of arm numbers and concentration of macromer. The degradation and drug release rate could be controlled by varying the cross-linking density of hydrogel, indicating a potential application as controlled drug delivery system. Cytotoxicity test of hydrogel extracts was conducted using L929 mouse fibroblasts, and the relative growth rate exceeded 75% (cytotoxicity type: class 1) after incubation for 24 h, showing excellent cytocompatibility. In addition, the paper presented a pH-sensitive hydrogel (G4) based on 4-arm-PEG-PCL-AC and acrylic acid, and the influences of pH value on swelling behaviors and in vitro drug release of the pH-sensitive hydrogel were examined. The hydrogels shrank under acidic condition and would swell in neutral or basic medium. The pH-dependent drug release behaviors indicated a promising application of the materials as oral drug delivery vehicles.