European Journal of Biophysics 2020; 8(2): 52-59 http://www.sciencepublishinggroup.com/j/ejb doi: 10.11648/j.ejb.20200802.16 ISSN: 2329-1745 (Print); ISSN: 2329-1737 (Online) pH-sensitive Pickering Emulsion Stabilized by Hydroxyapatite Nanoparticles: Stability and Controlled Release Study Papa Mady Sy 1, * , Louis Augustin Diaga Diouf 1 , Alphonse Rodrigue Djiboune 1 , Sidy Mouhamed Dieng 4 , Mamadou Soumboundou 3 , Cecile Diop 1 , Toro Diop 1 , Gora Mbaye 1 , Mamadou Mbodj 2 , Mounibe Diarra 1, * 1 Department of Pharmacy, Laboratory of Pharmaceutical Physics, Faculty of Medicine, Pharmacy and Odontology, Cheikh Anta Diop University, Dakar, Senegal 2 Department of Medicine, Laboratory of Medical Biophysics and Nuclear Medicine, Faculty of Medicine, Pharmacy and Odontology, Cheikh Anta Diop University, Dakar, Senegal 3 Department of Pharmacy, Service of Medical Biophysics, Health Training and Research Unit, Thies University, Thies, Senegal 4 Department of Pharmacy, Laboratory of biopharmacy, Health Training and Research Unit, Thies University, Thies, Senegal Email address: * Corresponding author To cite this article: Papa Mady Sy, Louis Augustin Diaga Diouf, Alphonse Rodrigue Djiboune, Sidy Mouhamed Dieng, Mamadou Soumboundou, Cecile Diop, Toro Diop, Gora Mbaye, Mamadou Mbodj, Mounibe Diarra. pH-sensitive Pickering Emulsion Stabilized by Hydroxyapatite Nanoparticles: Stability and Controlled Release Study. European Journal of Biophysics. Vol. 8, No. 2, 2020, pp. 52-59. doi: 10.11648/j.ejb.20200802.16 Received: October 21, 2020; Accepted: November 7, 2020; Published: November 19, 2020 Abstract: This study investigates the formulation of surfactant-free Pickering emulsions that release a drug at a specific pH to improve its oral bioavailability. The stabilizing nanoparticles composed of hydroxyapatite were obtained by a process of nanoprecipitation. Pickering oil-in-water emulsions stabilized with hydroxyapatite nanoparticles and encapsulating a hydrophobic drug model (ibuprofen) were formulated using a high-energy process with rotor-stator turbo mixer (IKA® T25 digital ultra-Turrax). The experimental approach explored the impact of all formulation parameters, dispersed phase and amount of hydroxyapatite nanoparticles on the physicochemical properties of Pickering emulsions. The system was characterized by a methylene blue test, pH and conductivity measurements, and droplet size determination. In addition, Pickering emulsions stabilized by hydroxyapatite nanoparticles have the advantage of being destabilized in acidic medium leading to the release of the active principle via the droplets. The acidic medium release study (pH equal to 1.2) showed ibuprofen release as a function of initial droplet loading and saturation concentration. In the simulated intestinal medium at pH equal to 6.8, we found a better release of ibuprofen from emulsions that already had saturation in an acid medium. Thus, the interest of these Pickering emulsions lies on the fact that their non-toxicity and hydroxyapatite nanoparticles have advantage of being biocompatible because having the same mineral composition as bones and teeth. In addition, they allow destabilization of the emulsions and release of the drug. These emulsions not only protect patients from the side effects of acid-based drugs, but also contribute to increase the bioavailability of these acidic drugs. Keywords: Emulsion, Pickering, Nanoparticles, Hydroxyapatite, Oral Bioavailability 1. Introduction In many industrial sectors such as pharmacy [1], cosmetics [2], agri-food [3] and chemistry [4], emulsions are formulations used to obtain useful properties or suitable compositions. These emulsions are metastable dispersed systems consisting of least two immiscible liquids and an amphiphilic agent. One of the liquids is dispersed in the other