Chitosan nanoparticles for the oral delivery of tenofovir disoproxil fumarate: formulation optimization, characterization and <i>ex vivo</i> and <i>in vivo</i> evaluation for uptake mechanism in rats
<p><b>Objective:</b> Design chitosan based nanoparticles for tenofovir disoproxil fumarate (TDF) with the purpose of enhancing its oral absorption.</p> <p><b>Significance:</b> TDF is a prodrug that has limited intestinal absorption because of its susceptibility to gut wall esterases. Hence, design of chitosan based polymeric novel nanocarrier systems can protect TDF from getting metabolized and also enhance the oral absorption.</p> <p><b>Methods:</b> The nanoparticles were prepared using the ionic gelation technique. The factors impacting the particle size and entrapment efficiency of the nanoparticles were evaluated using design of experiments approach. The optimized nanoparticles were characterized and evaluated for their ability to protect TDF from esterase metabolism. The nanoparticles were then studied for the involvement of active transport in their uptake during the oral absorption process. Further, <i>in vivo</i> pharmacokinetic studies were carried out for the designed nanoparticles.</p> <p><b>Results:</b> The application of design of experiments in the optimization process was useful to determine the critical parameters and evaluate their interaction effects. The optimized nanoparticles had a particle size of 156 ± 5 nm with an entrapment efficiency of 48.2 ± 1%. The nanoparticles were well characterized and provided metabolic protection for TDF in the presence of intestinal esterases. The nanoparticles were able to increase the AUC of tenofovir by 380%. The active uptake mechanisms mainly involving clathrin-mediated uptake played a key role in increasing the oral absorption of tenofovir.</p> <p><b>Conclusions:</b> These results show the ability of the designed chitosan based nanoparticles in enhancing the oral absorption of TDF along the oral route by utilizing the active endocytic uptake pathways.</p
