Research Article Formulation and Optimization of Eudragit RS PO-Tenofovir Nanocarriers Using Box-Behnken Experimental Design Kefilwe Matlhola, 1 Lebogang Katata-Seru, 1 Lesego Tshweu, 2 Indra Bahadur, 1 Gertrude Makgatho, 3 and Mohammed Balogun 2 1 Chemistry Department, Faculty of Agriculture, Science and Technology, North West University, Mafkeng Campus, Private Bag X2046, Mmabatho 2735, South Africa 2 Council for Scientifc and Industrial Research, Materials Science and Manufacturing, Polymers and Composites, P.O. Box 395, Meiring Naude Road, Brummeria, Pretoria 0001, South Africa 3 Council for Scientifc and Industrial Research, Materials Science and Manufacturing, DST/CSIR National Centre for Nanostructured Materials, P.O. Box 395, Meiring Naude Road, Brummeria, Pretoria 0001, South Africa Correspondence should be addressed to Lebogang Katata-Seru; lebzakate@yahoo.com Received 22 May 2015; Revised 11 September 2015; Accepted 14 September 2015 Academic Editor: Tapan Desai Copyright © 2015 Keflwe Matlhola et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te objective of present study was to develop an optimized polymeric nanoparticle system for the antiretroviral drug tenofovir. A modifed nanoprecipitation method was used to prepare Eudragit RS PO nanoparticles of the drug. Te efect of amount of polymer, surfactant concentration, and sonication time on particle size, particle distribution, encapsulation efciency (EE), and zeta potential were assessed and optimized utilizing a three-factor, three-level Box-Behnken Design (BBD) of experiment. Fifeen formulations of nanoparticles were prepared as per BBD and evaluated for particle size, polydispersity index (PDI), EE, and zeta potential. Te results showed that the measured mean particle sizes were in the range of 233 to 499 nm, PDI ranged from 0.094 to 0.153, average zeta potential ranged from −19.9 to −45.8mV, and EE ranged between 98 and 99%. Te optimized formulation was characterized for in vitro drug release and structural characterization. Te mean particle size of this formulation was 233 nm with a PDI of 0.0107. It had a high EE of 98% and average zeta potential of −35mV, an indication of particle stability. Te FTIR showed some noncovalent interactions between the drug and polymer but a sustained release was observed in vitro for up to 80 hours. 1. Introduction Tenofovir is one of the frst-line drugs used in the treatment of the human immunodefciency virus (HIV) infected adults. It is a potent inhibitor of the virus nucleotide reverse transcriptase and was approved for clinical use in 2001 [1]. Its relatively low toxicity, long plasma half-life of 17 hours, and convenient dosing of 300 mg per day has made it favoured in HIV/AIDS-burdened countries like South Africa [2]. It is also an important component of the fxed dose antiretroviral combinations Truvada, Atripla, and Complera [3]. However, tenofovir sufers from nephrotoxicity, high aqueous solubility and is characterized by low gastrointestinal membrane pene- tration, which lowers its bioavailability to 25% [4]. Terefore, to maintain the oral delivery route, formulating the drug into polymeric nanoparticles is essential for improving the bioavailability. Nanoparticles present signifcant advantages over con- ventional free drug dosing [5, 6]. Tere is minimal drug loss during transit through the gastrointestinal tract while the particles evade degradation in the acidic environment of the stomach. Teir size and surface properties allow for uptake, without disrupting the particles’ integrity, by M cells in the Peyer’s patches of the small intestine [7]. Te lymphoid tissue associated with these patches facilitates distribution of the nanoparticles through the systemic circulations. While in the systemic circulation the nanoparticles extend the half- life of the drug and release it in a sustained manner. Te resultant beneft is a reduction of therapeutic dose, increased bioavailability, and limitation of toxic side-efects. Hindawi Publishing Corporation Journal of Nanomaterials Volume 2015, Article ID 630690, 11 pages http://dx.doi.org/10.1155/2015/630690