Synthesis and characterization of Cu/Ag nanoparticle loaded mullite nanocomposite system: A potential candidate for antimicrobial and therapeutic applications S. Kar a , B. Bagchi b , B. Kundu c , S. Bhandary d , R. Basu e , P. Nandy f , S. Das a, ⁎ a Physics Department, Jadavpur University, Kolkata 700 032, India b Fuel Cell and Battery Division, Central Glass and Ceramic Research Institute, Kolkata 700 032, India c Biotechnology Department, IIT Kharagpur, Kharagpur 721302, India d Bose Institute, Department of Molecular Medicine, Kolkata 700 054, India e Physics Department, Jogamaya Devi College, Kolkata 700 026, India f Centre for Interdisciplinary Research and Education, Kolkata 700 068, India abstract article info Article history: Received 21 December 2013 Received in revised form 6 May 2014 Accepted 15 May 2014 Available online 1 August 2014 Keywords: Mullite Metal nanoparticle Antibacterial activity Cyto-compatibility Background: Microbial resistance to antibiotics has triggered the development of nanoscale materials as an alter- native strategy. To stabilize these particles an inert support is needed. Method: Porous nanomullite developed by sol–gel route is loaded with copper and silver nanoparticle by simple adsorption method. These nanocomposites are characterized using XRD, FTIR, TEM, SEM, EDAX and UV–visible spectrophotometer. Antibacterial activity of these nanocomposites against Gram positive and Gram negative bacteria are performed by bactericidal kinetics, flow cytometry and MTT assay. The underlying mechanisms be- hind the antimicrobial property and cell death are also investigated by EPR spectroscopy, intracellular ROS mea- surement and β-galactosidase assay. The cytocompatibility of the nanocomposites is investigated by cell viability (MTT), proliferation (Alamar blue) and wound healing assay of mammalian fibroblast cell line. Results: Nanocomposites show a fairly uniform distribution of metal nanoparticle within mullite matrix. They show excellent antibacterial activity. Metal ions/nanoparticle is found to be released from the materials (CM and SM). Treated cells manifested high intracellular oxidative stress and β-galactosidase activity in the growth medium. The effect of nanocomposites on mammalian cell line depends on exposure time and concentration. The scratch assay shows normal cell migration with respect to control. Conclusion: The fabricated nanoparticles possess diverse antimicrobial mechanism and exhibit good cytocompatibility along with wound healing characteristics in mouse fibroblast cell line (L929). General significance: The newly synthesized materials are promising candidates for the development of antimi- crobial ceramic coatings for biomedical devices and therapeutic applications. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Excessive use of antibacterial agents like chemically modified natu- ral compounds (penicillins, cephalosporins or carbapenems), pure nat- ural products (aminoglycosides) and purely synthetic antibiotics lead to the development of drug resistant microbes. These resistant pathogens cause the emergence of diseases, which are difficult to diagnose and control. This has prompted the development of alternative antimicrobi- al agents such as nanoscale materials. Because of their extremely small size and high surface to volume ratio, nanoparticles have increased activity and interaction with microbial components. Additionally, the antimicrobial mechanism of metal nanoparticles is diverse, restricting the easy development of microbial resistance [1]. Silver and its compounds are popular antimicrobial agents. Silver nanoparticles are now used in a wide spectrum of consumer products right from clothing, respirators, antibacterial sprays, detergent, socks, shoes, etc. Silver based nanoparticles are being used in various forms such as metallic silver nanoparticles, silver chloride particles, silver im- pregnated zeolite, powders or polymer silver nanoparticle composites [2]. Copper nanoparticles enjoy much attention because of their catalyt- ic, optical, electrical and antifungal/antibacterial applications [3]. How- ever, optimal use of metal nanoparticles as antibacterial agents is limited due to their low stability like, light induced deactivation of silver nanoparticles and aerial oxidation of copper nanoparticles. In addition, nanoparticles tend to aggregate to larger particles reducing their perfor- mance. Therefore, to increase the stability of these particles and reduce Biochimica et Biophysica Acta 1840 (2014) 3264–3276 ⁎ Corresponding author. Tel.: +91 9433091337. E-mail address: sukhendasju@gmail.com (S. Das). http://dx.doi.org/10.1016/j.bbagen.2014.05.012 0304-4165/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Biochimica et Biophysica Acta journal homepage: www.elsevier.com/locate/bbagen