Synthesis and characterization of star-shaped poly(l-lactide)s with an erythritol core and evaluation of their rifampicin-loaded microspheres for controlled drug delivery

In this paper, a series of star-shaped poly(l-lactide)s (s-PLLA) were synthesized via ring-opening polymerization of l-lactide (LLA) using erythritol as initiator. The structure and properties of s-PLLA were characterized by ¹H NMR, GPC and DSC. Then taking rifampicin (RIF) as the model drug, RIF-loaded s-PLLA microspheres were prepared using an oil-in-water emulsion solvent evaporation method. SEM and size analysis indicated that s-PLLA with high monomer/initiator molar ratios (s-PLLA98 and s-PLLA99) could form regular microspheres with smooth surface and have narrow size distributions, which hold the drugs well. The XRD spectra of the RIF-loaded microspheres demonstrated that s-PLLA and RIF were both in their amorphous state after the encapsulation process, which might be caused by the impediment effect of each other. The in vitro release profiles of the RIF-loaded microspheres showed that the s-PLLA99 microspheres were able to sustain the release of RIF for a considerable period of time (70–80 % within 180 h) and the release profiles of RIF from s-PLLA microspheres followed the Baker–Lonsdale model equation. Therefore, these biodegradable and biocompatible s-PLLA microspheres may find practical applications as drug delivery carriers.