Development of Dispersible Vaginal Tablets of Tenofovir Loaded Mucoadhesive Chitosan Microparticles for Anti-HIV Pre-Exposure Prophylaxis

Abstract

Tenofovir disoproxil fumarate (TDF)-loaded bioadhesive chitosan microparticles (CM) were developed by an emulsification internal gelation technique. Among different batches produced, ECH-4 was found to display a high % entrapment efficiency (68.93 ± 1.76%) and sustained drug release of 88.05 ± 0.38% at 24 h. Solid state characterization of ECH-4 employing DSC and PXRD indicated that the TDF existed in an amorphous state as a solid-solid solution in chitosan. Scanning electron microscopy revealed CM of ECH-4 was spherical in shape with a rough surface topography. Laser scattering analysis using Malvern Master sizer indicated that particle size of ECH-4 was in the range of 0.52 ± 0.10 μm to 284.79 ± 21.42 μm with a surface-mean diameter of 12.41 ± 0.06 μm. Ex vivo mucoadhesion studies using rabbit mucosa as a substrate indicated that 10.34 ± 2.08% of CM of ECH-4 was retained at the end of 24 h. The microparticles of ECH-4 were incorporated into dispersible tablets (DT-TCM) intended for intravaginal administration, in view to arrest the pre-exposure transmission of HIV during sexual intercourse. In vitro release from the dispersible tablet (F3) into simulated vaginal fluid (pH 4.5) displayed a sustained release profile of TDF as 89.98 ± 1.61% of TDF was released at 24 h. The in vitro dissolution profile of the DT-TCM was found to be similar to that of TDF loaded CM with the values of f₁ (difference factor) and f₂ (similarity factor) being 1.52 and 78.02, respectively. Therefore, DT-TCM would be a promising novel drug delivery platform for pre-exposure prophylaxis against HIV.

Keywords: chitosan; intravaginal; mucoadhesion; sustained release; tenofovir; vaginal tablet.