International Journal of Pharmaceutics 459 (2014) 1–9 Contents lists available at ScienceDirect International Journal of Pharmaceutics j o ur nal ho me page: www.elsevier.com/locate/ijpharm Thermosensitive hydrogels of poly(methyl vinyl ether-co-maleic anhydride) – Pluronic ® F127 copolymers for controlled protein release Esther Moreno a , Juana Schwartz a,b , Eneko Larra ˜ neta b , Paul A. Nguewa a , Carmen Sanmartín a,c , Maite Agüeros b , Juan M. Irache b , Socorro Espuelas a,b,∗ a Tropical Health Institute, University of Navarra, Irunlarrea 1, E-31008 Pamplona, Spain b Pharmacy and Pharmaceutical Technology Department, University of Navarra, Irunlarrea 1, E-31008 Pamplona, Spain c Organic and Pharmaceutical Chemistry Department, University of Navarra, Irunlarrea 1, E-31008 Pamplona, Spain a r t i c l e i n f o Article history: Received 2 August 2013 Received in revised form 11 November 2013 Accepted 18 November 2013 Available online 4 December 2013 Keywords: Thermosensitive hydrogels Pluronics Polyanhydride Protein Controlled release a b s t r a c t Thermosensitive hydrogels are of a great interest due to their many biomedical and pharmaceutical applications. In this study, we synthesized a new series of random poly (methyl vinyl ether-co-maleic anhydride) (Gantrez ® AN, GZ) and Pluronic ® F127 (PF127) copolymers (GZ–PF127), that formed ther- mosensitive hydrogels whose gelation temperature and mechanical properties could be controlled by the molar ratio of GZ and PF127 polymers and the copolymer concentration in water. Gelation tempera- tures tended to decrease when the GZm/PF127 ratio increased. Thus, at a fixed GZm/PF127 value, sol–gel temperatures decreased at higher copolymer concentrations. Moreover, these hydrogels controlled the release of proteins such as bovine serum albumin (BSA) and recombinant recombinant kinetoplastid membrane protein of Leishmania (rKMP-11) more than the PF127 system. Toxicity studies carried out in J774.2 macrophages showed that cell viability was higher than 80%. Finally, histopathological anal- ysis revealed that subcutaneous administration of low volumes of these hydrogels elicited a tolerable inflammatory response that could be useful to induce immune responses against the protein cargo in the development of vaccine adjuvants. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Hydrogels are polymer-based systems that have received much more attention because of their numerous biomedical and pharma- ceutical applications, including drug delivery, cell encapsulation and tissue repair (Appel et al., 2012; Jeong et al., 2000; Ruel Gariépy and Leroux, 2004; Wang et al., 2010; Yu et al., 2010). Hydrogels that exhibit the specific property of increased viscosity with increased temperature are known as thermosensitive hydro- gels. These hydrogels have shown easier application and longer survival periods at the site of application as compared to non- thermosensitive hydrogels (Cheaburu et al., 2013; Douglas et al., 2013). However, there is an important need in the development of new systems with shorter gelation times, higher biodegradability, stronger mechanical strength, better bioadhesive properties and extended sustained compounds release (Liu et al., 2007; Park et al., 2009; Sosnik and Cohn, 2004). ∗ Corresponding author at: Pharmacy and Pharmaceutical Technology Depart- ment, University of Navarra, Irunlarrea 1, E-31008 Pamplona, Spain. Tel.: +34 948425600; fax: +34 948425619. E-mail address: sespuelas@unav.es (S. Espuelas). Pluronic ® F127 (PF127), also named poloxamer, is a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymer that has interest because it can form a gel in situ depending on its concentration and temperature (Alexandridis et al., 1995). Due to the presence of hydrophobic propylene oxide blocks, concentrated solutions of PF127 (20–30% w/v) can pass from low viscosity solutions (sol) to solid gels (gel) upon heating to body temperature, resulting in a reverse thermal gelation (Moore et al., 2000; You and Van Winkle, 2010). Thus, it has been reported to be one of the less toxic of commercially available copolymers and its biocompatibility makes PF127 an attractive candidate as a pharmaceutical vehicle for drugs through different ways of administration (Escobar Chávez et al., 2006; Lee and Tae, 2007). Despite its multiple benefits, PF127 has yet weak mechanical properties and this limits its application because it is not stable and easily destroyed when diluted after its adminis- tration into the human body (Chun et al., 2005; Sosnik and Cohn, 2004). To circumvent these problems, physical or chemical modifica- tions of PF127 have been previously reported. Hydrogels composed of linoleic acid (Guo et al., 2009), hyaluronic acid (Hsu et al., 2009) or alginate (Fang et al., 2009) linked to Pluronic F127 sustained the release of paclitaxel, cisplatin and carboplatin, respectively, for 0378-5173/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ijpharm.2013.11.030