International Journal of Pharmaceutics 446 (2013) 63–69 Contents lists available at SciVerse ScienceDirect International Journal of Pharmaceutics jo ur nal homep a ge: www.elsevier.com/locate/ijpharm Caprolactam-silica network, a strong potentiator of the antimicrobial activity of kanamycin against Gram-positive and Gram-negative bacterial strains Georgeta Voicu a , Valentina Grumezescu a,b , Ecaterina Andronescu a , Alexandru Mihai Grumezescu a,∗ , Anton Ficai a , Denisa Ficai c , Cristina Daniela Ghitulica a , Irina Gheorghe d , Mariana Carmen Chifiriuc d a Department of Science and Engineering of Oxidic Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest 011061, Romania b National Institute for Lasers, Plasma & Radiation Physics, Lasers Department, P.O. Box MG-36, Bucharest-Magurele, Romania c Department of Inorganic Chemistry, Faculty of Applied Chemistry and Materials Science, Politehnica University of Bucharest, 011061, Romania d Department of Microbiology and Immunology, Faculty of Biology, University of Bucharest 060101, Romania a r t i c l e i n f o Article history: Received 30 November 2012 Received in revised form 31 January 2013 Accepted 1 February 2013 Available online 10 February 2013 Keywords: MIC Kanamycin sulfate Silica Antimicrobial therapy Caprolactam a b s t r a c t Here, we report the fabrication of a novel -caprolactam-silica (-SiO 2 ) network and assessed its biocompatibility and ability to improve the antimicrobial activity of kanamycin. The results of the quan- titative antimicrobial assay demonstrate that the obtained -SiO 2 network has efficiently improved the kanamycin activity on Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922 strains, with a significant decrease of the minimum inhibitory concentration. The -SiO 2 network could be feasibly obtained and represents an alternative for the design of new antibiotic drug carriers or delivery systems to control bacterial infections. © 2013 Elsevier B.V. All rights reserved. 1. Introduction During the last decades a diversity of polymer based pharma- ceutical carrier systems have been developed as new means of controlling temporal or distributional (site-specific) drug delivery, offering numerous advantages compared to conventionally admin- istrated drugs in dosage forms, such as improved efficiency and reduced toxicity (Rosler et al., 2008; Ye et al., 2008; Dhanasingh et al., 2011; Asgary et al., 2011; Grumezescu et al., 2011a). The ideal drug delivery system should be inert or biodegradable, biocompat- ible, mechanically strong, comfortable for the patient, capable of achieving high drug loading, safe from accidental release, simple to administer and remove, and easy to fabricate and sterilize (Ye et al., 2008). Materials based on silica matrices have been extensively high- lighted for many biomedical applications, as delivery carriers for therapeutic agents (Wang et al., 2011). The main advantage of sil- ica is that it provides a biocompatible, nontoxic surface, with a high hydrophilicity. It is also quite stable in blood. These particles will therefore have a prolonged half-life in the blood stream (Yu et al., 2011; Lin and Haynes, 2010). Silanol groups, Si-OH, and the porosity ∗ Corresponding author. Tel.: +40 765349326. E-mail address: grumezescu@yahoo.com (A.M. Grumezescu). of silica network play an important role in controlling the release of the therapeutic agents (Pon-On et al., 2011). Many studies have been reported with drug delivery from silica materials and it has been shown that silica is able to store and gradually release ther- apeutic agents (Meseguer-Olmo et al., 2006; Florea et al., 2012). In many diseases the administration of a drug is only required at specific time intervals in which constant drug levels could lead to adverse effects (Bikram et al., 2007). Aminoglycosides are clinically important antibiotics to treat infectious diseases caused by Gram-positive and Gram-negative bacteria. These drugs bind to the decoding region of ribosome, inducing codon misreading, inhibiting translocation, and eventu- ally leading to cell death (Chen et al., 2009; Hermann, 2000). Kanamycin (sulfate), (2-(aminomethyl)-6-[4,6-diamino-3- [4-amino-3,5-dihydroxy-6-(hydroxymethyl)tetrahydropyran-2- yl]oxy-2-hydroxy-cyclohexoxy], tetrahydropyran-3,4,5-triol) is an aminoglycoside antibiotic solely produced by fermentation using certain strains of Streptomyces kanamyceticus (Megoulas and Koupparis, 2005). It is widely administrated as a second line antibiotic in the form of injection and capsules. Like most of aminoglycosides, dose dependent side effects of ototoxicity and nephrotoxicity have been observed (Gennaro, 1985). Previous studies have shown that biodegradable silica xerogel could be an efficient carrier of gentamycin antibiotic, the amino- glycoside molecules entrapped in the sol-gel matrix remaining in 0378-5173/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ijpharm.2013.02.011