A novel and green biomaterial based silver nanocomposite hydrogel: Synthesis, characterization and antibacterial effect Ghasem R. Bardajee ⁎, Zari Hooshyar, Habib Rezanezhad Department of Chemistry, Payame Noor University, PO BOX 19395–3697, Tehran, Iran abstract article info Article history: Received 24 February 2012 Received in revised form 23 June 2012 Accepted 25 June 2012 Available online 1 July 2012 Keywords: Silver nanoparticles Drug delivery Tetracycline hydrochloride Hydrogel Antibacterial effect In the present study, we report a facile and eco-friendly method for the preparation of a novel silver nanocomposite hydrogel (SNH) based on poly(acrylic acid) (PAA) grafted onto salep as a water soluble polysaccharide backbone. The presence of inorganic silver nanoparticles (nano-Ag) in the hydrogel was confirmed by thermo-gravimetric (TG) analysis. The TEM images illustrated the presence of embedded nano-Ag throughout the hydrogel matrix. In addition, the transmission electron microscopy (TEM) images showed that the formed nano-Ag had an average par- ticle size of 5–10 nm. The potential of obtained SNH was examined for Tetracycline hydrochloride (TH) release in simulated colon conditions. Lastly, the in vitro antibacterial properties of the obtained optimum sample were suc- cessfully evaluated against gram-negative and gram-positive bacteria. © 2012 Elsevier Inc. All rights reserved. 1. Introduction In recent years, the study and preparation of metal particles on the nanometer scales have attracted considerable interest from both funda- mental and applied researches [1–3]. It is due to different physical and mechanical properties of metal nano-sized particles from those of mac- roscopic materials. They are mainly utilized in solving the problems of water purification, catalysis, electronics, sensors, hydrogen storage [4–9], luminescence devices [10], photonics [11], pharmaceuticals [12], biotechnology, and medicine [13]. The silver nanoparticles (nano-Ag) have proved to be most effective as they exhibit potent antimicrobial ef- ficacy against bacteria, viruses and eukaryotic micro-organisms [14,15]. It has been demonstrated that nano-Ag can inhibit viral replication of vi- ruses, such as human immunodeficiency virus type 1, hepatitis B virus, respiratory syncytial virus, herpes simplex virus type 1, and monkey pox virus [16]. Nano-Ag have been studied as a medium for antibiotic de- livery [17], and to synthesize composites for use as disinfecting filters [18] and coating materials [19]. To receive a better stabilization or dispersion of nano-Ag in aqueous media, various protective agents have been used for the synthesis and controlling the size of nano-Ag [14,17,18]. For this purpose, different polymeric stabilizing agents, dendrimers, latex particles and microgels have exclusively been studied. In addition, many researches are heading for exploiting the in situ synthesis of nano-Ag within the polymeric net- work architectures which leading to new hybrids or composite systems in chemistry and engineering sciences [19–21]. In this way the carrier systems, for example dendrimers or microgels, act as ‘nanoreactors’ that immobilize the particles and provide an easy handling. Hydrogels offer large free spaces between the crosslinked networks in the swollen stage that can act as a nanoreactor for the nucleation and growth of the nano-Ag [22–28]. This approach due to the long reac- tion times, the use of chemical and usually toxic reagents, low efficiency in converting the silver cations (Ag + ) to nano-Ag, and lack of control over the size of nano-Ag has not been welcomed. The biopolymers applied for the synthesis of silver nanocomposites due to their almost limitless availability, low price, and biocompatibility. As the purpose of silver nanocomposites is mostly toward biomedical treatment, different hydrogels have been applied in this field. For exam- ple, Vimala et al. [29] report the preparation of semi-interpenetrating hydrogel networks based on cross-linked poly(acrylamide). The polymer was prepared through a redox polymerization of N,N- methylenebisacrylamide in the presence of different carbohydrate polymers such as gum acacia and carboxymethylcellulose. They re- duced silver cations inside the network using sodium borohydride. The amide and hydroxyl functional groups of the network were projec- ted to enhance the stability of the silver nanoparticles inside the matrix; however their size distribution was broad. Their antimicrobial effective- ness was tested against E. coli. In addition, silver nanoparticles have been obtained with hydrogel networks as nanoreactors via in situ re- duction of silver nitrate using sodium borohydride as a reducing agent. However, the antimicrobial activity was not high, obviously due to the limited ion release from the capped and protected silver nanoparticles. In addition, other hydrogel–silver nanocomposites have been synthesized by a synthetic route involving the formation of silver nanoparticles within swollen poly(acrylamide-co-acrylic acid) hydro- gels by using citrate ions. The formation of silver nanoparticles was Journal of Inorganic Biochemistry 117 (2012) 367–373 ⁎ Corresponding author. Tel.: +98 281 3336366; fax: +98 281 3344081. E-mail address: rezanejad@pnu.ac.ir (G.R. Bardajee). 0162-0134/$ – see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.jinorgbio.2012.06.012 Contents lists available at SciVerse ScienceDirect Journal of Inorganic Biochemistry journal homepage: www.elsevier.com/locate/jinorgbio