Synthesis and characterization of bovine serum albumin-loaded microspheres based on star-shaped PLLA with a xylitol core and their drug release behaviors

The star-shaped poly(l-lactide) (s-PLLA) was synthesized via ring-opening polymerization of l-lactide, with xylitol as a multifunctional initiator and stannous octoate as a catalyst. The structures of s-PLLA were characterized by ¹H NMR spectroscopy, while the molecular weight (M _w) and polydispersity index were determined by gel permeation chromatography. Bovine serum albumin (BSA) loaded s-PLLA microspheres were fabricated by a water–oil–water (W ₁/O/W ₂) double-emulsion solvent evaporation method. The morphology, drug encapsulation efficiency (EE), and in vitro release behavior of the prepared microspheres were studied in detail. Results indicated that the average diameters of s-PLLA microspheres could be controlled between 7 and 15 µm by varying the s-PLLA’s concentration or M _w, and the drug encapsulation efficiency of BSA-loaded microspheres were 10–42%. The in vitro study shows that the BSA-loaded microspheres prepared by high molecular weight s-PLLA had a slow cumulative release behavior in phosphate buffer saline (PBS, pH 7.4) and the release process followed the Baker–Lonsdale equation. Present work supposes that the synthesized s-PLLA is a good candidate for drug delivery.