Hydrophilic drug release from electrospun membranes made out of thermo and pH-sensitive polymers

Electrospun fibers of the thermo-and pH sensitive poly(N-vinylcaprolactam-co-acrylic acid) (Poly(NVCL-co-AA) loaded with 10% and 30 wt% caffeine (Caf) were obtained by electrospinning and evaluated as potential drug delivery systems. Caffeine was used as a hydrophilic drug model, and poly(NVCL-co-AA) containing either 20 or 30 mol% AA was used as a carrier. The fibers morphology, as well as, their interaction with caffeine, were studied using different analytical techniques. The cytotoxicity of the different obtained fibers was evaluated by cell viability assays using 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) and mouse embryonic fibroblasts cell line (MEF cells). Caffeine release was studied at temperatures of 25 °C and 42 °C and pH of 1.2 and 7.4. Beadless copolymer fibers with diameters ranging from 1 μm to 2 μm were obtained. The addition of caffeine, which was in crystalline form after being encapsulated in the fibers, resulted in an increase of fiber diameter. The obtained membranes were found to be not cytotoxic. The entrapment of caffeine was greater for the copolymer containing 30 mol% AA due to a greater affinity of AA to caffeine. At a pH of 1.2 and at both temperatures of 25 °C and 42 °C, as well as, at a pH of 7.4 and a temperature of 42 °C, a Fickian diffusion mechanism for all copolymer fiber mats was observed. At a pH of 7.4 and 25 °C the release profile showed a high rate and followed a zero-order model, due to the fast dissolution of caffeine in water. These results indicated that thermo-and pH-sensitive poly(NVCL-co-AA) are promising candidates for controlled release of hydrophilic drugs.