Thermally-triggered gelation of PLGA dispersions: Towards an injectable colloidal cell delivery system

In this study the properties of poly(d,l-lactide-co-glycolide) (PLGA) dispersions containing a thermoresponsive cationic copolymer were investigated. The PLGA dispersions were prepared by interfacial deposition in aqueous solution and were rendered thermoresponsive by addition of a cationic poly(N  -isopropyl acrylamide) (PNIPAm) graft copolymer. The copolymers used had the general composition PDMAx+-g-(PNIPAmn)y. DMA+ is quarternarized N,N  -dimethylaminoethyl methacrylate. The PDMAx+-g-(PNIPAmn)y copolymers have x and y values that originate from the macroinitiator used for their preparation; values for n correspond to the PNIPAm arm length. The thermoresponsive dispersions were characterised using photon correlation spectroscopy, turbidity measurements and electrophoretic mobility measurements. A strong electrostatic attraction between the anionic PLGA particles and cationic copolymer was present and the dispersions showed thermally-triggered gelation at total polymer volume fractions as low as 0.015. These new PLGA gels, which formed at about 32 °C, had elastic modulus values that could be controlled using dispersion composition. Scanning electron micrographs of the gels showed high porosity and interconnectivity of elongated pores. Remarkably, the gels were flexible and had critical yield strains as high as 160%. The ability of the gels to support growth of bovine nucleus pulposus cells was investigated using two-dimensional cell culture. The cells proliferated and remained viable on the gels after 3 days. The results suggest that this general family of biodegradable thermogelling PLGA dispersions, introduced here for the first time, may have longer-term application as an injectable colloidal cell delivery system.

Graphical abstractWe investigate thermally-triggered gelation of PLGA dispersions and show that this new family of responsive fluid has long term application as a colloidal cell delivery system.Figure optionsDownload full-size imageDownload high-quality image (151 K)Download as PowerPoint slide