Shaofeng Lou

Galactose functionalized injectable thermoresponsive microgels for sustained protein release

Novel galactose functionalized thermoresponsive injectable microgels, poly(N-isopropylacrylamide-co-6-O-vinyladipoyl-D-galactose) P(NIPAAm-co-VAGA), have been fabricated using a combination of enzymatic transesterification and emulsion copolymerization. The microgels exhibit reversible temperature-responsive behavior, which can be tuned by varying the monomer feed ratio. The lower critical solution temperatures (LCSTs) of the materials are close to body temperature and can result in a rapid thermal gelation at 37 °C. Field emission scanning electron microscopy showed the resultant microgels to have porous structures, and dynamic light scattering experiments indicated a dramatic reduction in particle size as solutions of the polymers are heated through the LCST. The polymers can be loaded with protein (bovine serum albumin; BSA), and in vitro studies showed that the BSA release kinetics depend upon the temperature and copolymer composition. Microgels based on P(NIPAAm-co-VAGA) could hence serve as candidates for site-specific sustained release drug delivery systems.

Fabrication and aggregation of thermoresponsive glucose-functionalized double hydrophilic copolymers

Novel double-hydrophilic thermosensitive statistical glycopolymers, poly(N-isopropylacrylamide-co-6-O-vinyladipoyl-D-glucose), were fabricated using a chemoenzymatic process and free radical copolymerization. The structures of the glycopolymers were confirmed by (1)H and (13)C NMR, and their molar mass distributions determined by gel permeation chromatography. UV-vis spectroscopy data showed that the polymers exhibited reproducible temperature-responsive behavior. The self-assembly and critical aggregation concentration was verified by fluorescence spectroscopy with pyrene acting as a hydrophobic probe. Measurements by laser light scattering and transmission electron microscopy revealed that the glycopolymers were able to self-assemble into aggregates with varying particle sizes and morphologies in aqueous solutions.

A systematic study of captopril-loaded polyester fiber mats prepared by electrospinning.

In this study, drug-loaded nanofibers were prepared by electrospinning captopril (CPL) with aliphatic biodegradable polyesters. Poly(L-lactic acid) (PLLA), poly(lactic-co-glycolic acid) (PLGA), and poly(lactic-co-ε-caprolactone) (PLCL) were used as filament-forming matrix polymers, and the concentration of CPL in each fiber type was varied. Scanning electron microscopy indicated that the morphology and diameters of the fibers were influenced by the concentration of polymer in the spinning solution and the drug loading. CPL was found to be distributed in the polymer fibers in an amorphous manner using differential scanning calorimetry and X-ray diffraction. FTIR indicated that hydrogen bonding existed between the drug molecules and the carrier polymers. In vitro dissolution tests showed that drug release from the fibers was highly dependent on the release medium, temperature, and on the polymer used. A range of kinetic models were fitted to the drug-release data obtained, and indicated that release was diffusion controlled in all cases. The different polymer fibers have application in diverse areas of drug delivery, for instance as sub-lingual or sustained release systems. Furthermore, by combining different CPL-loaded fibers, it would be possible to produce a bespoke formulation with tailored drug-release properties.