Casein nanoparticles as carriers for the oral delivery of folic acid Rebeca Penalva a , Irene Esparza a , Maite Agüeros a , Carlos J. Gonzalez-Navarro b , Carolina Gonzalez-Ferrero c , Juan M. Irache a, * a Department of Pharmacy and Pharmaceutical Technology, University of Navarra, 31008, Pamplona, Spain b Centre for Nutrition Research, University of Navarra, 31080, Pamplona, Spain c Centro Nacional de Tecnología y Seguridad Alimentaria e CNTA, San Adri an, Spain article info Article history: Received 23 June 2014 Accepted 9 October 2014 Available online 25 October 2014 Keywords: Casein Nanoparticles Folic acid Lysine Bioavailability Oral delivery abstract Food grade proteins can be viewed as an adequate material for the preparation of nanoparticles and microparticles. They offer several advantages such as their digestibility, price and a good capability to interact with a wide variety of compounds and nutrients. The aim of this work was to prepare and characterize casein nanoparticles for the oral delivery of folic acid. These nanoparticles were prepared by a coacervation process, stabilized with either lysine or arginine and, finally, dried by spray-drying. For some batches, the effect of a supplementary treatment of nanoparticles (before drying) with high hy- drostatic pressure on the properties of the resulting carriers was also evaluated. The resulting nano- particles displayed a mean size close to 150 nm and a folic acid content of around 25 mg per mg nanoparticle. From the in vitro release studies, it was observed that casein nanoparticles acted as gastro- resistant devices and, thus, folic acid was only released under simulated intestinal conditions. For the pharmacokinetic study, folic acid was orally administered to laboratory animals as a single dose of 1 mg/ kg. Animals treated with folic acid-loaded casein nanoparticles displayed significantly higher serum levels than those observed in animals receiving an aqueous solution of the vitamin. As a consequence the oral bioavailability of folic acid when administered as casein nanoparticles was calculated to be around 52%, a 50% higher than the traditional aqueous solution. Unfortunately, the treatment of casein nano- particles by high hydrostatic pressure modified neither the release profile of the vitamin nor its oral bioavailability. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction In recent years, nano- and microencapsulation has been a growing interest for pharmaceutical, nutraceutical and food ap- plications. For food applications, these nano- and microencapsu- lation approaches may be of interest for any of the following reasons: i) protect the compound of interest from its premature degradation (during processing or storage) or undesirable in- teractions with the environment; ii) mask astringency tastes; iii) facilitate its processability (improving solubility and dispers- ability); iv) control and/or prolong its release; and/or v) improve its oral bioavailability (Desai & Jin Park, 2005; Quintanilla-Carvajal et al., 2010). Alimentary proteins, naturally present in food, offer a great potential as a material for the preparation of nanoparticles and microparticles. Overall they are biodegradable, digestible, cheap, offer a nutritional value, and, due to the presence of a number of functional groups, they can interact with a wide variety of com- pounds in a relatively non-specific way. Another important point is that they are usually considered as GRAS (generally recognized as safe) compounds. In addition, the procedures to transform these proteins into nanoparticles or microparticles are simple and can be performed in an aqueous medium or in environmentally and food grade accepted solvents. Examples of these proteins include legu- min and vicilin from peas (Pisum sativum L.) (Ezpeleta, Irache, Stainmesse, Gueguen, & Orecchioni, 1996; Irache, Bergougnoux, Ezpeleta, Gueguen, & Orecchioni, 1995), gliadin from wheat (Arangoa, Campanero, Renedo, Ponchel, & Irache, 2001; Ezpeleta et al., 1996), zein from corn (Zhong, Tian, & Zivanovic, 2009) or proteins from soy (Glycine max L.) (Teng, Luo, & Wang, 2012). Another interesting protein for micro- and nanoparticle design is casein. Casein is the major milk protein and possesses many structural and physicochemical properties that facilitate its func- tionality in drug delivery systems (Semo, Kesselman, Danino, & Livney, 2007). Thus, casein-based devices have been proposed for * Corresponding author. Dep. Pharmacy and Pharmaceutical Technology, Uni- versity of Navarra, C/ Irunlarrea,1, 31080, Pamplona, Spain. Tel.: þ34 948425600; fax: þ34 948425619. E-mail address: jmirache@unav.es (J.M. Irache). Contents lists available at ScienceDirect Food Hydrocolloids journal homepage: www.elsevier.com/locate/foodhyd http://dx.doi.org/10.1016/j.foodhyd.2014.10.004 0268-005X/© 2014 Elsevier Ltd. All rights reserved. Food Hydrocolloids 44 (2015) 399e406