Development and characterization of cores–shell poly(lactide-co-glycolide)-chitosan microparticles for sustained release of GDNF

[Display omitted] •The cores–shell microparticles were fabricated with a single shell of chitosan and multi cores of PLGA.•The cores–shell microparticles were able to reduce the initial burst release of GDNF.•The cores–shell microparticles neutralized the acidic products from PLGA and avoided pH decrease.•The chitosan shell played a role in maintaining the bioactivity of released GDNF. The microencapsulation of bioactive neurotrophic factors in biodegradable poly(lactide-co-glycolide) (PLGA) microspheres has been a promising tool in the treatment of various nervous system disorders. However, challenges still exist; the PLGA burst drug release and acidic degradation products often limit clinical application. In this study, cores–shell PLGA-chitosan microparticles (MPs) were fabricated with a single shell of chitosan and multi-cores of PLGA using a re-emulsification method. The glial cell line-derived neurotrophic factor (GDNF) was encapsulated at the PLGA cores of the cores–shell MPs. The cores–shell MPs prepared by different chitosan concentrations showed a rough surface, and the particle mean size varied between 32.3 and 45.2μm. The fluorescence images indicated that Nile red-stained PLGA microspheres were uniformly distributed in the cores–shell MPs. Compared with PLGA microspheres, the cores–shell MPs were able to reduce the initial burst release of GDNF and neutralize the acidity of PLGA degradation products, which could be modulated by changing the chitosan concentrations. Further differentiation of PC12 cells toward a neuronal phenotype in vitro indicated that the cores–shell MPs were capable of maintaining the bioactivity of GDNF during preparation. Taken together, these findings highlight the possibility of using cores–shell PLGA-chitosan MPs for the sustained release of GDNF, which offers potential applications in nerve injury repair.