Encapsulation and/or Release Behavior of Bovine Serum Albumin within and from Polylactide-Grafted Dextran Microspheres

Polylactide (PLA)‐grafted dextran (Dex‐graft‐PLA) of various contents of sugar units was synthesized by anionic polymerization of L‐lactide (L‐LA) using the alkoxide of partially trimethylsilylated dextran (TMSDex) and subsequently removing the trimethylsilyl (TMS) groups. The copolymer showed different solubility from L‐LA homopolymer with increasing the content of sugar units. We prepared bovine serum albumin (BSA)‐loaded microspheres (MS)s according to a water‐in‐oil‐in‐water emulsion‐solvent evaporation/extraction method using methylene chloride/DMSO as an organic cosolvent. MSs prepared from Dex‐graft‐PLA [MS(Dex‐graft‐PLA)s] exhibited higher loading efficiency of BSA than MSs prepared from PLLA [MS(PLLA)s]. The in vitro release rate of BSA from MS(Dex‐graft‐PLA) was faster than that from MS(PLLA). BSA released from MS(Dex‐graft‐PLA) maintained the secondary structure of native BSA to a great extent, compared with BSA released from MS(PLLA). Confocal fluorescence images of the differential interference micrographs over the fluorescence images of MS(PLLA) and MS(Dex‐graft‐PLA).