Biodegradable sodium alginate-based semi-interpenetrating polymer network hydrogels for antibacterial application K. Madhusudana Rao, 1,2 K. S. V. Krishna Rao, 3 G. Ramanjaneyulu, 4 K. Chowdoji Rao, 5 M. C. S. Subha, 1 Chang-Sik Ha 2 1 Department of Chemistry, Sri Krishnadevaraya University, Anantapur 515 003, India 2 Department of Polymer Science and Engineering, Pusan National University, Busan 609-735, Korea 3 Department of Chemistry, Yogi Vemana University, Kadapa 516 003, India 4 Department of Microbiology, Sri Krishnadevaraya University, Anantapur 515 003, India 5 Department of Polymer Science and Technology, Sri Krishnadevaraya University, Anantapur 515 003, India Received 23 August 2013; revised 2 October 2013; accepted 8 October 2013 Published online 22 October 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jbm.a.34991 Abstract: A series of biodegradable, semi-interpenetrating polymer network (semi-IPN) hydrogels were synthesized from a combination of carbohydrate polymer and sodium alginate (NaAlg) with acrylamide and dimethyl aminoethyl methacrylate, and crosslinked with N,N-methylenebisacryla- mide via radical redox polymerization. The cytocompatibility of the hydrogels with respect to their monomers and semi- IPN hydrogels was evaluated in vitro using cultures of mouse fibroblast cell lines. This study allowed the entrapment of sil- ver nanoparticles (NPs) into semi-IPN hydrogel networks by the in situ reduction of Ag 1 ions using NaBH 4 as a reducing agent. UV–visible spectroscopy confirmed the formation of silver NPs in the semi-IPN hydrogel matrix. The formation of silver NPs was also confirmed from a themogravimetric anal- ysis weight loss difference between hydrogel and silver nanocomposite as 32%. The morphology and structure of the AgNPs present in the hydrogel networks were examined by scanning electron microscopy. Transmission electron micros- copy revealed silver NPs with a size of 5 nm. The silver nanocomposite hydrogel exhibited good antibacterial activity against both gram positive (Staphylococcus aureus) and gram negative (Escherichia coli) bacteria. These results sug- gest that the hydrogel can be applied as wound dressings and for water purification purposes. VC 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3196–3206, 2014. Key Words: semi-IPNs, hydrogel, cytocompatibility, biode- gradability, silver nanocomposite, medical applications How to cite this article: Madhusudana Rao K, Krishna Rao KSV, Ramanjaneyulu G, Chowdoji Rao K, Subha MCS, Ha C-S. 2014. Biodegradable sodium alginate-based semi-interpenetrating polymer network hydrogels for antibacterial application. J Biomed Mater Res Part A 2014:102A:3196–3206. INTRODUCTION Metal nanoparticles (NPs) embedded in host polymers have attracted considerable interest in recent years. 1,2 These materials exhibit unique electrical, optical, or mechanical properties, 3,4 making them valuable for applica- tions in areas, such as optics, 5 photo imaging and pattern- ing, 6 electronic devices, 7 sensors and biosensors, 8–10 catalysis, 11,12 and antimicrobial coatings. 13 In addition, the embedding of nanoscopic metals in polymer matrices is one of the easiest and most convenient ways for nanostruc- tured metal stabilization and handling process. 14 Recently, there has been increasing interest in “green” chemical processes, which are characterized by the use of nontoxic materials and the total elimination or minimization of gen- erated waste. Some of the key issues that merit important consideration in green synthetic strategies include the utili- zation of bio- and biocompatible materials, nontoxic chemi- cals, environmentally benign solvents, hydrogels, and renewable materials. 15 Therefore, the use of biopolymer based biodegradable and biocompatible crosslinked hydro- gel templates are believed to be even more suitable for the development of metal NPs than conventional nonaqueous systems of non-biocompatible polymeric systems for bio- medical applications. Interpenetrating polymer network (IPN)-based hydrogels are attractive for the production of stable silver NPs using a chemical reduction method. The unique and novel proper- ties of environmentally sensitive IPNs have been studied extensively and used as smart materials for a range of bio- medical applications. 16 Semi-IPNs have been developed as a Correspondence to: C.-S. Ha; e-mail: csha@pnu.edu Contract grant sponsor: Ministry of Science, ICT & Future Planning, Korea; Acceleration Research program; contract grant number: 2013041172 Contract grant sponsor: Pioneer Research Center Program; contract grant number: 2013041888/201304889 Contract grant sponsor: Brain Korea 21 Plus program 3196 VC 2013 WILEY PERIODICALS, INC.