Elaboration of Charged Poly(Lactic-co-Glycolic Acid) Microparticles for Effective Release of Tranexamic Acid

In this study, tranexamic acid (TA) was used as a model compound to study the charge effect on the physicochemical properties of poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs). Charged PLGA MPs were elaborated by the incorporation of a quaternary ammonium, cetyltrimethylammonium bromide (CTAB), during the double emulsion solvent evaporation process. Three TA-CTAB-carrying modes of PLGA MPs were designed in the CTAB-free (TA-MP), adsorption (TA-CTAB(AD)), or encapsulation (TA-CTAB(EN)) form. The obtained MPs were characterized by morphology and TA-MP affinity. The experiment revealed that the three prepared MPs were spherical and smooth, with pores on their surfaces. TA-CTAB(AD) had a relatively narrow size distribution, compared with that of TA-MP and TA-CTAB(EN). The particle sizes of TA-MP, TA-CTAB(EN), TA-CTAB(AD) were measured as 59 +/- 17, 54 +/- 20, and 19 +/- 8 mu m, respectively. The zeta potential of the three MPs was found to be in the order: TA-CTAB(AD) > TA-CTAB(EN) > TA-MP. Differential scanning calorimetry (DSC) indicated that the manufacturing process had no influence on the glass transition temperature of the MPs, which was close to 48 degrees C. Thermogravimetric analysis illustrated that the presence of CTAB slightly changed the thermal stability of PLGA MPs. In vitro release showed that TA-CTAB(AD) exhibited faster TA release than TA-MP and TA-CTAB(EN) in a basic environment (pH of 13), probably because of electrostatic attraction. At pH = 1, the release of TA from TA-CTAB(EN) was faster than those from TA-MP and TA-CTAB(AD), probably because of electrostatic repulsion. However, the effect of electrostatic interaction was not significant at pH = 7.4.