Oxaprozin/poly(2-hydroxyethyl acrylate/itaconic acid) hydrogels: morphological, thermal, swelling, drug release and antibacterial properties Marija M. Babic ´ • Katarina M. Antic ´ • Jovana S. Jovas ˇevic ´ Vukovic ´ • Bojan Ð. Boz ˇic ´ • Sladjana Z. Davidovic ´ • Jovanka M. Filipovic ´ • Simonida Lj. Tomic ´ Received: 31 July 2014 / Accepted: 4 October 2014 / Published online: 18 October 2014 Ó Springer Science+Business Media New York 2014 Abstract In this study, a series of novel stimuli-sensitive hydrogels based on 2-hydroxyethyl acrylate and itaconic acid monomers were designed for the controlled release of hydrophobic drug, Oxaprozin. All samples were synthe- sized by the free-radical crosslinking copolymerization and characterized for structural, morphological, thermal, sur- face charge, swelling and antibacterial properties. In order to investigate the influence of the drug on hydrogel prop- erties the same characterization was conducted for all Oxaprozin-loaded samples. The chemical composition of hydrogels was studied using Fourier transform infrared spectroscopy, while their morphology and thermal prop- erties were examined by scanning electron microscopy and differential scanning calorimetry. Swelling studies, con- ducted in the physiological pH range from 2.20 to 8.00 and in the temperature range from 25 to 50 °C, showed that the loaded drug does not modify the pH and temperature sensitivity of the hydrogels, but reduces their swelling capacity. The in vitro drug release study conducted at pH 2.20 and 7.40 showed that all hydrogels can be tailored as colon specific drug delivery systems, and the drug release rate can be effectively controlled by IA content. In addi- tion, the antibacterial activity of the hydrogels was deter- mined against Escherichia coli and Staphylococcus aureus, by the zone of inhibition test. Results of our study indicate that these ‘‘smart’’ hydrogels, with specific morphology, surface charge, swelling capacity, drug loading efficiency and release behavior, could be designed to obtain an enhanced and site-specific controlled drug release system by simply adjusting their composition. Introduction Hydrogels are three-dimensional (3D) cross-linked poly- meric structures that possess excellent water retention capacity, and have soft tissue-like consistency [1]. Because of their non-toxicity, biocompatibility and biodegradabil- ity, hydrogels have attracted much attention as new bio- materials [2]. Their specific water-absorbing property makes them suitable for controlled drug delivery applica- tions, wound-healing patches or films, cell encapsulation, tissue regeneration (bone, cartilage, skin, blood vessel, etc.), and for various biomedical and pharmaceutical applications [3–9]. Controlled drug release at the desired site of application is a critical and desirable behavior of a drug carrier which offers many advantages, including higher therapeutic effi- cacy with minimum side effects induced using a drug, patient compliance, as well as cost effectiveness of the drug regime over the conventional drug delivery systems M. M. Babic ´  K. M. Antic ´  J. S. J. Vukovic ´  B. Ð. Boz ˇic ´  S. Z. Davidovic ´  J. M. Filipovic ´  S. Lj. Tomic ´(&) Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, Belgrade, Serbia e-mail: simonida@tmf.bg.ac.rs M. M. Babic ´ e-mail: mbabic@tmf.bg.ac.rs K. M. Antic ´ e-mail: katarina.antic@tmf.bg.ac.rs J. S. J. Vukovic ´ e-mail: jjovasevic@tmf.bg.ac.rs B. Ð. Boz ˇic ´ e-mail: bbozic@tmf.bg.ac.rs S. Z. Davidovic ´ e-mail: sdavidovic@tmf.bg.ac.rs J. M. Filipovic ´ e-mail: jfil@tmf.bg.ac.rs 123 J Mater Sci (2015) 50:906–922 DOI 10.1007/s10853-014-8651-z