Optimization and modeling of PEGylated, hydrocortisone‐17‐butryate‐loaded poly(lactic‐co‐glycolic acid) microspheres

Abstract

We propose by surface functionalizing poly(lactic‐co‐glycolic acid) (PLGA) microspheres we can increase bioavailability and therapeutic duration of hydrocortisone‐17‐butyrate delivery for an intra‐articular injection. In this paper, we look at the proof of concept of the design of the microspheres by optimizing a single‐stage oil/water emulsion. Surface‐modified corticosteroid‐loaded PLGA microspheres (MSs) were synthesized via an avidin/biotin system and were characterized via microscopy, and dynamic light scattering. The optimized PLGA MSs were an average of 1.22 µm ± 0.0132 µm with a zeta potential of −23.17 ± 0.97 mV. Hydrocortisone 17‐butyrate was loaded as a model corticosteroid (entrapment efficiency of 71.98%), and release was evaluated for 3 weeks and compared to a bi‐phasic diffusional model. PEGylation was found to significantly alter the biphasic release by reducing the fractional surface desorption (burst release) and maximizing Fickian diffusion controlled extended release. Unmodified homologs showed 2.34 times more surface desorbed drug as compared to their PEGylated form. These studies show that we can develop a corticosteroid loaded MS that is closer to a large nano‐size, with extended release for 3 weeks. The addition of the PEGlyation to the surface also further increases controlled release, therefore, mitigating harmful concentration spikes post‐administration.