TiO 2 /PCL hybrid materials synthesized via sol–gel technique for biomedical applications M. Catauro a, ⁎, F. Bollino a , F. Papale a , S. Marciano b , S. Pacifico b a Department of Industrial and Information Engineering, Second University of Naples, Via Roma 29, 81031 Aversa, Italy b Department Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, Via Vivaldi 43, 81100 Caserta, Italy abstract article info Article history: Received 1 August 2014 Received in revised form 24 October 2014 Accepted 8 November 2014 Available online 12 November 2014 Keywords: Sol–gel Organic/inorganic hybrid Bioactivity Biocompatibility The aim of the present work has been the synthesis of organic/inorganic hybrid materials based on titanium di- oxide and poly(ε-caprolactone) (PCL) to be used in the biomedical field. Several materials have been synthesized using sol–gel methods by adding different amounts of polymer to the inorganic sol. The obtained gels have been characterized using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The FT-IR data allowed us to hypothesize that the structure formed was that of an interpenetrating network, realized by hydrogen bonds between Ti\OH groups in the sol–gel intermediate species and carbonyl groups in the polymer repeating units. SEM and AFM analyses highlighted that the obtained materials were nanostructurated hybrids. To evaluate the biological properties of the hybrids, their bioactivity and cytotoxicity were investigated as a function of the PCL amount. The bioactivity of the synthesized systems was proven by the formation of a hydroxyapatite layer on the surface of samples soaked in a fluid simulating human blood plasma (SBF). MTT cytotoxicity tests and Trypan Blue dye exclusion tests were carried out exposing NIH-3T3 mouse embryonic fibroblasts for 24 and 48 h to extracts from the investigated hybrid materials. The results showed that all the hybrids had a non-cytotoxic effect on target cells. © 2014 Published by Elsevier B.V. 1. Introduction There is increasing interest in titanium and its alloys to develop biomedical materials and devices, designed as a hard tissue substitute with enhanced interfacial properties [1–4]. These materials find many applications in orthopedic and dental fields because of their favorable combination of mechanical properties (tensile strength and fatigue resistance), corrosion resistance, biocompatibility and lack of inflamma- tory response. The high compatibility is due to their ability to quickly develop, when exposed to fluid media or air, a layer of titanium dioxide (TiO 2 ) which produces passivation of the metal determining the biological response of the implant [5]. On the other hand, studies on TiO 2 -based bioactive ceramics proved that bone grafting is achieved by encouraging the nucleation of hydroxyapatite (the mineral phase of bone) by means of the precipitation of calcium and phosphorus [1–3]. An attractive technique to synthesize highly bioactive and biocompat- ible glasses and ceramics [6–13] is the sol–gel method. The chemistry of the process is based on the hydrolysis and condensation of metal alkox- ides which occur at low temperature [14]. The last feature allows the en- trapment in the inorganic matrix of notorious thermolabile substances, such as polymers or drugs, in order to produce organic–inorganic nano- composite materials. These are considered as biphasic materials, where the organic and inorganic phases are mixed at nanometer to micrometer scales, and their properties are derived from a synergy between the individual contributions of both phases [15,16]. Depending on the nature of the interaction between the components, these materials are divided into two distinct classes [15,16]. In class I, organic and inorganic compounds are embedded by means of weak bonds (hydrogen, van der Waals or ionic bonds); in class II hybrid, the phases are linked together through strong chemical bonds (covalent or ionic-covalent bonds). The presence of organic components modifies the morphology and physical properties of the sol–gel products [17,18]. Previously, several hybrids for drug delivery or biomedical applica- tions have been prepared, by means of sol–gel methods, in our laborato- ry using different polymers (e.g. poly(ε-caprolactone) [6,7,9,10,19,20] and poly(ether-imide) [21]) which allowed modifications to some properties of the glassy materials, such as mechanical properties or the release kinetic of entrapped drugs. The aim of the present study is the sol–gel synthesis and character- ization of hybrid materials for biomedical applications, consisting of an inorganic titania matrix and poly(ε-caprolactone). The obtained mate- rials were characterized by means of several techniques. Fourier trans- form infrared spectroscopy (FT-IR) was used to identify the nature of the interface between the polymer and the inorganic phase. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were carried out to ascertain that the synthesized materials are hybrid nano- composites. Moreover, in order to evaluate the possibility of using these Materials Science and Engineering C 47 (2015) 135–141 ⁎ Corresponding author. E-mail address: michelina.catauro@unina2.it (M. Catauro). http://dx.doi.org/10.1016/j.msec.2014.11.040 0928-4931/© 2014 Published by Elsevier B.V. Contents lists available at ScienceDirect Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec