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 μm, 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 °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.