Amino Acid based Silver Nanocomposite Hydrogels Bull. Korean Chem. Soc. 2012, Vol. 33, No. 10 3191 http://dx.doi.org/10.5012/bkcs.2012.33.10.3191 Fabrication of Amino Acid Based Silver Nanocomposite Hydrogels from PVA- Poly(Acrylamide-co-Acryloyl phenylalanine) and Their Antimicrobial Studies Hyeong-Rae Cha, † V. Ramesh Babu, † K. S. V. Krishna Rao, †,‡ Yong-Hyun Kim, † Surong Mei, †,§ Woo Hong Joo, # and Yong-Ill Lee †,* † Anastro Laboratory, Department of Chemistry, Changwon National University, Changwon 641-773, Korea * E-mail: yilee@changwon.ac.kr ‡ Department of Chemistry, Yogi Vemana University, Kadapa-516003, India § MOE Key Laboratory of Environment and Health, Institute of Environmental Medicine, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Hubei 430030, China # Department of Biology, Changwon National University, Changwon 641-773, Korea Received May 7, 2012, Accepted July 2, 2012 New silver nanoparticle (AgNP)-loaded amino acid based hydrogels were synthesized successfully from poly (vinyl alcohol) (PVA) and poly(acryl amide-co-acryloyl phenyl alanine) (PAA) by redox polymerization. The formation of AgNP in hydrogels was confirmed by using a UV-Vis spectrophotometer and XRD. The structure and morphology of silver nanocomposite hydrogels were studied by using a scanning electron microscopy (SEM), which demonstrated scattered nanoparticles, ca. 10-20 nm. Thermogravimetric analysis revealed large differences of weight loss (i.e., 48%) between the prestine hydrogel and silver nanocomposite. The antibacterial studies of AgNP-loaded PAA (Ag-PAA) hydrogels was evaluated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria. These Ag-PAA hydrogels showed significant activities against all the test bacteria. Newly developed hydrogels could be used for medical applications, such as artificial burn dressings. Key Words : Nanocomposite hydrogels, Poly(acryl amide-co-acryloyl phenyl alanine), Silver nanoparticles, Anti-bacterial study Introduction Since hydrogels possess hydrophilic character and have potential for biocompatibility, they have been of great interest to biomaterial scientists for many years. 1-4 Hydro- gels have been used in numerous applications, including biosensors, bioreactors, bioseparators, tissue engineering, and drug delivery, due to their excellent biocompatibility. 5-8 Hydrophilic polymer networks are physically crosslinked or formed by crosslinking agents. 9,10 Early work in the 1980’s by Yannas and coworkers 11 demonstrated the successful application of natural polymer hydrogels as artificial burn dressings. More recently, hydrogels have become attractive to tissue engineers as matrices for regenerating a wide variety of tissues and organs. 12,13 Hydrogels are hydrophilic polymer networks that may absorb water from 10-20 times (an arbitrary lower limit) up to thousands times than their dry weight. Poly(vinyl alcohol) (PVA) is a well-known hydrophilic, biocompatible, and commercially available polymer. It has good mechanical strength, low fouling potential, and long- term temperature and pH stability. These properties of PVA lend well to its use in bioseparation, medical, and pharma- ceutical applications. 14,15 Metal nanoparticles show peculiar optical, magnetic, and electronic properties that bulk solid or isolated molecules do not usually exhibit. 16-18 Recently, there has been immense interest in the fabrication of composite materials consisting of polymer-encapsulated particles. It is now well-established that polymers are excellent host materials for nanoparticles made of metals and semiconductors. 19-21 When the nano- particles are embedded or encapsulated in polymer, the polymer acts as a surface capping agent. The particle size is well controlled within the desired regime and make the casting of films easier. 22,23 Most popular methods employed for encapsulation include emulsion polymerization, sur- factant-free emulsion polymerization, emulsion-like poly- merization, suspension polymerization, and dispersion poly- merization. Among metal/polymer composites, silver com- posites have found important applications in material techno- logies like optical materials, 24 catalytic systems, antibacterial materials, 25,26 chemical nanosensors, and surface-enhanced Raman scattering (SERS). 27 However, the most significant challenge encountered in preparing silver/polymer nano- particle encapsulation is that the nanoparticles cannot be dispersed in polymer matrix at the nano level by conven- tional techniques because the surface energies of tiny silver particles are very high, and these particles tend to agglome- rate during mixing. For application in optoelectronics and electronics, the precise control of particle size and their uniform distribution within the polymer are key techno- logies based on nanoparticles in polymers. Improved stability of silver nanoparticles (AgNPs) has been understood in polystyrene (PS), 28,29 possibly because of the presence of