Enhancing Betulinic Acid Dissolution Rate and Improving Antitumor Activity via Nanosuspension Constructed by Anti-Solvent Technique

Purpose: The aim of this study was to prepare and evaluate betulinic acid nanosuspension (BA-NS) for new drug delivery to enhance its solubility and in vitro anti-tumor activity. Methods: BA-NS was formulated by an anti-solvent precipitation method using the Box-Behnken design (BBD). Particle size (PS) and Zeta potential were measured by laser particle size analysis. The drug solid state after freeze drying was characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD) and Fourier transform infrared spectroscopy (FTIR) after freeze drying. The saturation solubility and dissolution rate were determined by solubility assay and in vitro dissolution studies, respectively. The in vitro cytotoxicity assay was performed using 3-(4,5-dimethylthiazole)-2,5-diphenltetraazolium bromide (MTT) method. Results: The PS was 129.7+/-12.2 nm having a Zeta potential of -28.1+/-4.5 mV and the polydispersity index (PDI) was 0.231+/-0.013, which confirmed that the nanosuspension was in the stable amorphous state. A series of characterization experiments demonstrated that nanoparticles retained original effective structure and existed as spherical or near-spherical nanoparticles in the nanosuspension, but the drug transferred from the crystal state to the amorphous state. The form of lyophilized BA-NS was very successful in enhancing the dissolution rate in PH-dependent way. The cytotoxicity assay revealed that BA-NS could significantly enhance the in vitro anti-proliferation against tumor cells compared to the BA suspension (BA-S). Conclusion: The BA-NS can remarkably improve solubility and in vitro antitumor activity, which seems very promising for the treatment of cancers in practical application.