Tenofovir Containing Thiolated Chitosan Core/Shell Nanofibers: <i>In Vitro</i> and <i>in Vivo</i> Evaluations

It is hypothesized that thiolated chitosan (TCS) core/shell nanofibers (NFs) can enhance the drug loading of tenofovir, a model low molecular weight and highly water-soluble drug molecule, and improve its mucoadhesivity and <i>in vivo</i> safety. To test this hypothesis, poly­(ethylene oxide) (PEO) core with TCS and polylactic acid (PLA) shell NFs are fabricated by a coaxial electrospinning technique. The morphology, drug loading, drug release profiles, cytotoxicity and mucoadhesion of the NFs are analyzed using scanning and transmission electron microscopies, liquid chromatography, cytotoxicity assays on VK2/E6E7 and End1/E6E7 cell lines and <i>Lactobacilli crispatus</i>, fluorescence imaging and periodic acid colorimetric method, respectively. <i>In vivo</i> safety studies are performed in C57BL/6 mice followed by H&E and immunohistochemical (CD45) staining analysis of genital tract. The mean diameters of PEO, PEO/TCS, and PEO/TCS-PLA NFs are 118.56, 9.95, and 99.53 nm, respectively. The NFs exhibit smooth surface. The drug loading (13%–25%, w/w) increased by 10-fold compared to a nanoparticle formulation due to the application of the electrospinning technique. The NFs are noncytotoxic at the concentration of 1 mg/mL. The PEO/TCS-PLA core/shell NFs mostly exhibit a release kinetic following Weibull model (<i>r</i>² = 0.9914), indicating the drug release from a matrix system. The core/shell NFs are 40–60-fold more bioadhesive than the pure PEO based NFs. The NFs are nontoxic and noninflammatory <i>in vivo</i> after daily treatment for up to 7 days. Owing to their enhanced drug loading and preliminary safety profile, the TCS core/shell NFs are promising candidates for the topical delivery of HIV/AIDS microbicides such as tenofovir