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.

Star-shaped polylactide (PLLA) is a potential candidate in many biomedical applications owing to its short degradation time; however, non-bioresorbable polyols have been used in most syntheses of star-shaped polylactide and these are a potential hazard. In this work, reaction of natural xylitol with l-lactide (LLA) was used to synthesize a star-shaped polyester via ring-opening polymerization. The chemical structures of the prepared star-shaped PLLA were characterized by means of 1H NMR and gel permeation chromatography (GPC). The crystallization behaviors of the polymers were examined by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The XRD curves of all the star-shaped PLLA based on various xylitol molar fractions were similar, but the crystallinity decreased with the increase of the xylitol molar fraction. These polymers were amorphous when the molar fraction of xylitol was higher than 6 %, whereas they were semicrystalline when the molar ratio of xylitol fell below 6 %. Finally, the degradation of the star-shaped PLLA was studied in phosphate buffer solution (pH 7.4) at 37 °C, which indicated that the degradation rate of polymers increased with the increase of xylitol molar fraction.

•Multi-porous SPS/CS spheres were prepared via nonsolvent/solvent-induced phase separation process in half an hour.•The porous structure has high specific surface area and good mechanical stability.•Porous SPS/CS could remove chromium ions(III) efficiently and its saturated adsorption capacity was up to 270 mg/g.•Porous SPS/CS/Ag particles can completely reduce the methlyene blue within 10 min.A new strategy was developed to prepare multi-porous composite particles by introducing porous-structured sulfonated polystyrene/chitosan (SPS/CS) microspheres into the reduction reaction of silver nitrate. The multi-porous SPS/CS microspheres were prepared by nonsolvent/solvent-induced phase separation method within 30 min, which was a simple and efficient operation. The BET specific surface area of the multi-porous SPS/CS microspheres is 47.3 m2/g, which is significantly higher than that of the solid SPS/CS (3.8 m2/g). The porous-structured SPS/CS could efficiently adsorb chromium ions(III) in aqueous solution and the saturated adsorption capacity obtained from the experimental was 270 mg/g. Meanwhile, the porous SPS/CS microspheres was used to carry silver nanoparticles, and the obtained SPS/CS/Ag composite particles were used as catalyst to reduce the methlyene blue (MB). The results indicated that nearly 100% of the MB has been reduced within 10 min, which was significantly faster than that of solid-structured composite particles. The higher content and smaller diameter of silver nanoparticles on the multi-porous SPS/CS/Ag was the main reason for the highly efficient activity to catalyze the reduction of MB.