Uptake studies in rat Peyer's patches, cytotoxicity and release studies of alginate coated chitosan nanoparticles for mucosal vaccination Olga Borges a, ⁎ , Anabela Cordeiro-da-Silva b , Stefan G. Romeijn c , Maryam Amidi c , Adriano de Sousa a , Gerrit Borchard c,d , Hans E. Junginger c,e a Center for Pharmaceutical Studies, Laboratory of Pharmaceutical Technology, Faculty of Pharmacy, University of Coimbra, Rua do Norte, 3000-295 Coimbra, Portugal b IBMC and Laboratory of Biochemical, Faculty of Pharmacy, University of Porto, 4050-047 Porto, Portugal c Leiden/Amsterdam Center for Drug Research, Division of Pharmaceutical Technology, P.O. Box 9502, 2300 RA Leiden, The Netherlands d School of Pharmacy Geneva/Lausanne, University of Geneva, 1211 Geneva 4, Switzerland e Faculty of Pharmaceutical Sciences, Naresuan University, Phitsanulok 65 000, Thailand Received 3 March 2006; accepted 12 June 2006 Available online 16 June 2006 Abstract The design of particulate vaccine delivery systems, particularly for mucosal surfaces, has been a focus of interest in recent years. In this context, we have previously described the development and the characterization of a new nanosized delivery system, consisting of a model antigen adsorbed to chitosan particles and coated with sodium alginate. In the present work the ovalbumin release profiles from these coated nanoparticles in different pH buffers were investigated and compared to those of the uncoated particles. Cytotoxicity of the polymers and nanoparticles was assessed using the MTT assay. Finally, particle uptake studies in rat Peyer's patches were performed. It was demonstrated that the coating of the nanoparticles with sodium alginate not only avoided a burst release observed with uncoated particles but also increased the stability of the particles at pH 6.8 and 7.4 at 37 °C. At neutral pH, the release was lower than 5% after 3.5 h incubation in a low ionic strength buffer. For both, chitosan and alginate polymers, and for the nanoparticles, comparable cell viability data close to 100%, were obtained. Additionally, based on confocal laser scanning microscopy observations, it was shown that alginate coated nanoparticles were able to be taken up by rat Peyer's patches, rendering them suitable carriers for intestinal mucosal vaccination. © 2006 Elsevier B.V. All rights reserved. Keywords: Coated nanoparticles; Chitosan; Sodium alginate; Peyer's patches; Cytotoxicity 1. Introduction The primary reason for using the mucosal route of vaccination is that it is the most effective route to induce a local protective immune response, resulting in the release of sIgA, against infec- tions originating at a mucosal surfaces [1,2]. However, only few vaccines currently approved for human use are administered mucosally, most of which are live-attenuated ones. Mucosal vac- cines, comprising soluble protein antigens, in general yielded rather disappointing results. Many factors have been described causing this problem [2] and different strategies have been applied to meet this challenge [2,3]. One such strategy is the development of polymeric nanoparticulate delivery systems. In general, these systems are thought to promote entrapment and retention of antigens in local lymph nodes [4]. On the other hand, they might protect the antigens from the adverse environment in the presence of hydrolytic enzymes or low pH at the gastrointestinal mucosal surface. In a recent publication we have described the development and the characterization of a new nanosized delivery system, consis- ting of chitosan nanoparticles with ovalbumin adsorbed at the surface and coated with sodium alginate [5]. These particles were designed for crossing mucosal barriers and releasing the antigen Journal of Controlled Release 114 (2006) 348 – 358 www.elsevier.com/locate/jconrel ⁎ Corresponding author. Tel.: +351 239859927; fax: +351 239827126. E-mail address: olga@ci.uc.pt (O. Borges). 0168-3659/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jconrel.2006.06.011