TANG Wen-Xing, FU Sheng-Nan, XING Qiao, WU Chuan-Bin, HU Hai-Yan*
2012, 43(10): 837-841.
Hydrophobic triacetyl-b-cyclodextrin (TA-b-CD) and hydrophilic hydroxypropyl-b-cyclodextrin (HP-b-CD) were respectively co-lyophilized with thymopentin (1). Then the sustained-release microspheres were prepared by s/o/w emulsion-solvent evaporation method with polylactic-co-glycolic acid (PLGA) as carrier material and 1 or its co-lyophilized complex as model drug. The effects of cyclodextrins on drug loading, encapsulation efficiency and burst effect of the above three kinds of 1-PLGA microspheres were compared and the mechanism of cyclodextrins to reduce the burst effect was preliminarily discussed. The results showed that the diameter, drug loading, encapsulation efficiency and burst effect (cumulative amount at 24 h) of 1-PLGA microspheres and 1-TA-b-CD-PLGA microspheres were (62.6±1.2) and (33.9±1.1) mm, (6.37±0.22)% and (8.59±0.19)%, (57.4±0.8)% and (80.4±0.6)%, 32.7% and 15.2%, respectively. However, compared with 1-PLGA microspheres, the drug loading and encapsulation efficiency of 1-HP-b-CD-PLGA microspheres were decreased and the burst effect were not significantly improved. The results of cold field scanning electron microscope, differential scanning calorimetry and powder X-ray diffraction showed that the crystal composition was changed during the co-lyophilizing process, which suggested that there had been an interaction between 1 and TA-b-CD. It might hinder the diffusion of 1 from the microspheres.