Research paper Smectite as ciprofloxacin delivery system: Intercalation and temperature-controlled release properties A. Rivera a, ⁎, L. Valdés b , J. Jiménez c , I. Pérez d , A. Lam a , E. Altshuler e , L.C. de Ménorval f , J.O. Fossum g, ⁎, E.L. Hansen g,1 , Z. Rozynek g,2 a Zeolites Engineering Laboratory, Institute of Materials Science and Technology (IMRE), University of Havana, Cuba b Department of Basic Chemistry, Institute of Pharmacy and Food (IFAL), University of Havana, Cuba c University Laboratory of Characterization of the Structure of the Substance, (LUCES), Institute of Materials Science and Technology (IMRE), University of Havana, Cuba d Department of Drugs Technology and Control, Institute of Pharmacy and Food (IFAL), University of Havana, Cuba e Group of Complex Systems and Statistical Physics, Physics Faculty, University of Havana, Cuba f Institut Charles Gerhardt Montpellier, Equipe Agregats, Interface, et Materiaux pour l'Energie (AIME), Universite Montpellier 2, France g Department of Physics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway abstract article info Article history: Received 15 December 2015 Received in revised form 4 February 2016 Accepted 8 February 2016 Available online xxxx Clays have shown to be good candidates as drug delivery carriers. In the present paper, the temperature- dependent swelling of smectites was exploited to obtain composites able to release a drug in a controlled way. More specifically, synthetic fluorohectorite-ciprofloxacin composites were prepared, in which the drug mole- cules were intercalated between the clay layers. The drug-release systems were characterized by X-ray diffrac- tion (XRD), infrared spectroscopy (IR), thermal gravimetric analysis (TGA), ultraviolet spectroscopy (UV) and atomic absorption spectrometry (AAS). The results from the X-ray diffraction allowed confirming the ciproflox- acin incorporation into the interlayer space, and the results from UV spectroscopy indicated that more than 90% of the initial drug was uptaken by the clay. The thermally activated drug release from a colloidal dispersion of nanosized composite particles in both pure water and synthetic gastric juice was evaluated at temperatures from 37 °C (body temperature) to 85 °C. The studies indicated that the clay promotes the slow release of cipro- floxacin, and that the release of drug increases with both time and temperature. The profiles of drug-release from the clay fulfilled the pharmaceutical standards for these systems. As a result, a clay-based Temperature- Controlled Release System (TCRS) with potential biomedical applications has been obtained. © 2016 Elsevier B.V. All rights reserved. Keywords: Drug Antibiotic Smectite Fluorohectorite Clay 1. Introduction Clays and clay minerals have been widely used for medical pur- poses. For example, they can be found in pharmaceutical formula- tions, both as inactive (excipients) and active agents (drugs) (Carretero, 2002; López-Galindo and Viseras, 2004; López-Galindo et al., 2007; USP30-NF25, 2007; Viseras et al., 2007). The therapeutic uses of these materials (López-Galindo and Viseras, 2004) are associ- ated to their chemical and physical properties, which depend ulti- mately on their structure. Temperature–controlled drug release is desirable in many scenarios: for example, when the local body temperature varies during different stages of a disease, or in response to external stimuli. To date, just a few materials able to release an active principle as a function of temper- ature have been investigated. Recently, hydrogel-based composites have been created to release proteins (Wu et al., 2005; Kang and Song, 2008), as well as microscale polymers able to release small molecules and nanoparticles within a certain temperature range (Hyun et al., 2013). In recent years, different porous materials have been used as drug hosts (Rivera and Farías, 2005; Joshi et al., 2011). In particular, clay min- erals and their modified forms have been employed in the development of new drug delivery systems (Viseras et al., 2010). Among them, mont- morillonite has been the most commonly used for drug delivery appli- cations (Park et al., 2008; Joshi et al., 2009), although kaolinite and laponite have also been investigated (Hamilton et al., 2014). Most of them have been typically used as hosts for pH-controlled release. Synthetic hectorites show a number of advantages as drug hosts, like controllable pore-size distribution, as well as purity and composition, which result in higher reproducibility. In addition, these materials have shown to be non-toxic for trans-dermal application and oral ad- ministration (Takahashi et al., 2005; Joshi et al., 2011). Their swelling transition (Hansen et al., 2012), on the other hand, suggests their Applied Clay Science 124–125 (2016) 150–156 ⁎ Corresponding authors. E-mail addresses: aramis@imre.oc.uh.cu (A. Rivera), jon.fossum@ntnu.no (J.O. Fossum). 1 Present address: Department of Monitoring and Research, Norwegian Radiation Protection Authority, Oslo, Norway. 2 Present address: Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61- 614 Poznań, Poland. http://dx.doi.org/10.1016/j.clay.2016.02.006 0169-1317/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay