In vitro degradation behavior of electrospun polyglycolide, polylactide, and poly(lactide-co-glycolide)

The electrospinning of polyglycolide (PGA), poly(L-lactide) (PLA), and poly(lactide-co-glycolide) (PLGA; L-lactide/glycolide = 50/50) was performed with chloroform or 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as a spinning solvent to fabricate their nanofiber matrices. The morphology of the electrospun PGA, PLA, and PLGA nanofibers was investigated with scanning electron microscopy (SEM). The PLGA nanofibers, electrospun with a nonpolar chloroform solvent, had a relatively large average diameter (760 nm), and it had a relatively broad distribution in the range of 200-1800 nm. On the other hand, the PGA and PLA fibers, electrospun with a polar HFIP solvent, had a small average diameter (∼300 nm) with a narrow distribution. This difference in the fiber diameters may be associated with the polarity of the solvent. Also, the in vitro degradation of PGA, PLA, and PLGA nanofiber matrices was examined in phosphate buffer solutions (pH 7.4) at 37°C. The degradation rates of the nanofiber matrices were fast, in the order of PGA > PLGA ≫ PLA. Structural and morphological changes during in vitro degradation were investigated with differential scanning calorimetry and wide-angle X-ray diffraction. For the PGA matrix, a significant increase in the crystallinity during the early stage was detected, as well as a gradual decrease during the later period, and this indicated that preferential hydrolytic degradation in the amorphous regions occurred with cleavage-induced crystallization, followed by further degradation in the crystalline region.