Research Article Controlled Synthesis of Gold Nanoparticles Using Aspergillus terreus IF0 and Its Antibacterial Potential against Gram Negative Pathogenic Bacteria Eepsita Priyadarshini, 1 Nilotpala Pradhan, 1,2 Lala B. Sukla, 2 and Prasanna K. Panda 2 1 Academy of Scientiic and Innovative Research, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751013, India 2 Bioresources Engineering Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751013, India Correspondence should be addressed to Nilotpala Pradhan; nilotpala pradhan@yahoo.co.in Received 18 February 2014; Revised 30 April 2014; Accepted 30 April 2014; Published 29 May 2014 Academic Editor: Paresh Chandra Ray Copyright © 2014 Eepsita Priyadarshini et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Biosynthesis of monodispersed nanoparticles, along with determination of potential responsible biomolecules, is the major bottleneck in the area of bionanotechnology research. he present study focuses on an ecofriendly, ambient temperature protocol for size controlled synthesis of gold nanoparticles, using the fungus Aspergillus terreus IF0. Gold nanoparticles were formed immediately, with the addition of chloroauric acid to the aqueous fungal extract. Synthesized nanoparticles were characterized by UV-Vis spectroscopy, TEM-EDX, and XRD analysis. Particle diameter and dispersity of nanoparticles were controlled by varying the pH of the fungal extract. At pH 10, the average size of the synthesized particles was in the range of 10–19 nm. Dialysis to obtain high and low molecular weight fraction followed by FTIR analysis revealed that biomolecules larger than 12 kDa and having –CH, – NH, and –SH functional groups were responsible for bioreduction and stabilization. In addition, the synthesized gold nanoparticles were found to be selectively bactericidal against the pathogenic gram negative bacteria, Escherichia coli. 1. Introduction Metal nanoparticles have been gaining importance in the past years because of their unique properties. Substantial research has been directed towards their reliable synthesis to explore their potential applications [1, 2]. Amongst the noble metals (silver, gold, and platinum), gold nanoparticles (GNPs) are of increasing interest due to their use in divergent ields of science [3–5]. he distinct optical property of GNPs makes them quite useful in the ield of biomedicine. GNPs are being extensively used for colorimetric detection of DNA and proteins, in form of biosensors, bioimaging, diagnostics, and therapeutic agents [6–9]. Over the years, several physicochemical methods have been used for GNP synthesis [10–13]. However, these synthetic protocols not only are hazardous and energy con- suming, but also pose a major disadvantage of adsorption of toxic chemical species onto the surface of nanoparticles mak- ing them unsuitable for biomedical applications [14]. Hence, researchers are focused towards synthesis of biocompatible nanoparticles leading to the development of a biological route for nanoparticle synthesis. Biological approach towards nanoparticle synthesis involves the use of an environmentally acceptable solvent system along with nontoxic reducing and capping agents [15]. A number of biological agents like bac- teria, algae, fungus, and plant extracts have been employed for biogenic nanoparticle synthesis [16–19]. Among the reported microorganisms, fungus ofers the advantage of easy handling and fast downstream processing and allows feasible large scale synthesis of nanoparticles due to the high secretion of enzymes and proteins [20]. Cytosolic extracts of the fungi Candida albicans, Aspergillus niger, Penicillium sp., and Aspergillus clavatus have been successfully used for GNP synthesis [21–24]. However, with reference to the ongoing researches in fungal nanobiotechnology, most of the work converges at the preliminary steps of synthesis. Identiication of the variables involved, along with elucidation of the responsible biomolecules, can greatly assist in achieving Hindawi Publishing Corporation Journal of Nanotechnology Volume 2014, Article ID 653198, 9 pages http://dx.doi.org/10.1155/2014/653198