Research paper Quality by design approach for developing chitosan-Ca-alginate microspheres for colon delivery of celecoxib-hydroxypropyl-b-cyclodextrin-PVP complex N. Mennini, S. Furlanetto, M. Cirri, P. Mura ⇑ Department of Pharmaceutical Sciences, University of Florence, Sesto Fiorentino, Firenze, Italy article info Article history: Received 17 April 2011 Accepted in revised form 1 August 2011 Available online 16 August 2011 Keywords: Celecoxib Cyclodextrin complex Microspheres Colon delivery Chitosan Ca-alginate abstract The aim of the present work was to develop a new multiparticulate system, designed for colon-specific delivery of celecoxib for both systemic (in chronotherapic treatment of arthritis) and local (in prophylaxis of colon carcinogenesis) therapy. The system simultaneously benefits from ternary complexation with hydroxypropyl-b-cyclodextrin and PVP (polyvinylpyrrolidone), to increase drug solubility, and vectoriza- tion in chitosan-Ca-alginate microspheres, to exploit the colon-specific carrier properties of these poly- mers. Statistical experimental design was employed to investigate the combined effect of four formulation variables, i.e., % of alginate, CaCl 2 , and chitosan and time of cross-linking on microsphere entrapment efficiency (EE%) and drug amount released after 4 h in colonic medium, considered as the responses to be optimized. Design of experiment was used in the context of Quality by Design, which requires a multivariate approach for understanding the multifactorial relationships among formulation parameters. Doehlert design allowed for defining a design space, which revealed that variations of the considered factors had in most cases an opposite influence on the responses. Desirability function was used to attain simultaneous optimization of both responses. The desired goals were achieved for both systemic and local use of celecoxib. Experimental values obtained from the optimized formulations were in both cases very close to the predicted values, thus confirming the validity of the generated mathemat- ical model. These results demonstrated the effectiveness of the proposed jointed use of drug cyclodextrin complexation and chitosan-Ca-alginate microsphere vectorization, as well as the usefulness of the mul- tivariate approach for the preparation of colon-targeted celecoxib microspheres with optimized properties. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction Celecoxib (CXB), 4-[5-(4-methylphenyl)-3-trifluoromethyl- 1H-pyrazol-1-yl] benzenesulfonamide, is a specific inhibitor of cycloxygenase-2 (COX-2) widely used as analgesic and in the treat- ment of osteoarthritis and rheumatoid arthritis, familial adenoma- tous polyposis, and primary dysmenorrhea [1,2]. It also showed a chemopreventive activity against colon carcinogenesis [3]. . More- over, it exhibits a similar therapeutic efficacy and a lower incidence of gastrointestinal complications in comparison with conventional NSAIDs [1,4]. However, CXB is a class II drug according to the biopharmaceutical classification system, and its very poor water solubility gives rise not only to formulation problems but also to low and highly variable bioavailability [5]. It has been shown that CXB solubility can be significantly improved by complexation with native b-cyclodextrin [6], and even more with its hydroxypropyl- derivative [7], particularly in the presence of hydrophilic polymers [8]. Other attempts of improving the CXB therapeutic effectiveness include incorporation in chitosan microspheres aimed for intra- articular administration [9], encapsulation in alginate micro- spheres as dispersion in a self-microemulsifying system [10], solid dispersion in a polymethacrylate carrier prepared by hot-melt extrusion [11], or formation of spherical agglomerates with hydro- philic polymers [12]. In recent years, colon-specific drug delivery systems gained increasing importance, not only for a more effective treatment of local pathologies, such as Chron’s diseases, ulcerative colitis, and colorectal cancer, but also for the systemic therapy of both conven- tional and labile molecules [13,14]. In fact, the colonic region exhib- its some peculiar advantages in comparison with stomach and small intestine, such as a less hostile environment, a longer residence time, and a better responsiveness to drug absorption enhancers [14]. Thus, colon-specific delivery could allow improvement in drug oral bio- availability, reduction in the total administered dose, and a decrease in side effects [15]. Moreover, it has been shown that colon-targeted drug delivery can be also exploited as a means of achieving chrono- therapy for diseases sensitive to circadian rhythms, such as asthma, 0939-6411/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ejpb.2011.08.002 ⇑ Corresponding author. Department of Pharmaceutical Sciences, University of Florence, Via Ugo Schiff 6, 50019 Sesto Fiorentino, Firenze, Italy. Tel.: +39 0554573672; fax: +39 0554573673. E-mail address: paola.mura@unifi.it (P. Mura). European Journal of Pharmaceutics and Biopharmaceutics 80 (2012) 67–75 Contents lists available at SciVerse ScienceDirect European Journal of Pharmaceutics and Biopharmaceutics journal homepage: www.elsevier.com/locate/ejpb