Research Article Open Access Nanomedicine & Nanotechnology Rastogi et al. J Nanomedic Nanotechnol 2011, 2:7 http://dx.doi.org/10.4172/2157-7439.1000121 Volume 2 • Issue 7 • 1000121 J Nanomedic Nanotechnol ISSN:2157-7439 JNMNT an open access journal Keywords: Silica; Iron oxide; Antibody; Escherichia coli; Electron microscopy; Raman spectroscopy Introduction he quick and reliable identiication of microorganisms is critical for the proper cure of infected individuals [1]. here are adequate conventional methods are available for microbial identiication [2]. However, most of them are laborious and expensive. To overcome from time - consuming methods, spectroscopic methods like luorescence [3,4], mass spectroscopy [5], Infrared (IR) spectroscopy [6] and surface- enhanced Raman spectroscopy (SERS) [7,8] have been developed. hese techniques are capable of identifying a whole microorganism from a limited number of microbial cells in a non-destructive manner. Among the spectroscopic methods, SERS has drawn attention because it is compatible with biological samples, requires lesser sample preparation and provide signals with detailed information concerning microorganism [9]. herefore, SERS, as an analytical tool, has been used in biological applications such as immunoassay [10], cellular studies [11], cancer diagnostic [12], bacterial detection [13], and food-safety projects [14] etc. For achieving signiicant information from bacterial cell using SERS, colloidal gold (Au) or silver (Ag) is required [15]. here, are several reports published concerning that the detection of a biomarker belongs to photogenic bacterial species on a noble surface. A report has been published by Efrima et al. [16] on SERS study of the cell wall with Ag nanoparticles (NPs) by reducing silver ions in the presence of bacteria. hey also demonstrated that the SERS spectra obtained from the bacterium cell walls and inside the bacterium were diferent when Ag NPs enter inside the bacterium cell [16]. Commonly, to capture, separate and identify a bacterium from a contaminated sample immunosensor is one of the choices. A typical immunosensor is usually fabricated by immobilizing the speciic antibody on the surface of an inert solid support via chemical or physical mechanisms [17]. In general, chemical immobilization can provides strong and stable protein attachment but physical adsorption provides only short time activity retention. hough, non-porous iron oxides (Fe 3 O 4 and γ-Fe 2 O 3 ) nanoparticles (IO-NPs), as a solid support, sufer from the drawback that some inactivation process for protein may be possible [18], the IO NPs possess their unique magnetic property – super paramagnetism, which enables their stability and dispersion ater removing the magnetic. Hence, silica coated IO NPs (SIO NPs) not only ofer improved stability but also help to bind the various chemical and biological ligands covalently at the surface of NPs [19]. Several interesting and important articles have been reported for SERS based identiication and rapid detection of E. coli using immune-magnetic IM NPs and others methods. Guven et al. [8] has reported the use of IM separation and SERS for rapidly (less than 70 min) and sensitively detect E. coli in real water sample using rod shaped Au NPs [8]. Liu et al. [14] have reported the feasibility of citerate reduced colloidal Ag SERS for diferentiating three important food borne pathogens (E. coli, Listeria monocytogenes, and Salmonella typhimurium) [20]. In another article, a convective assembly method has been reported by Kahraman et al. [21] for uniform bacterial (Gram-negative and Gram-positive bacterium) sample preparation. his method deposited bacteria and Ag NPs on a glass slide as a thin ilm in an ordered structure and detect using SERS, avoiding spot-to- spot variations [21]. hese reports clearly demonstrated that the IM NPs can be efectively used to capture bacteria, and citerate reduced Ag NPs are suicient for SERS identiication on glass slide. But, no report *Corresponding author: Shiva K. Rastogi, Department of Chemistry, University of Idaho, Moscow, ID - 83844-2343, Tel: 1-208-758-0416; Fax: 1-208-885-6173; E-mail: srastogi@uidaho.edu Received November 06, 2011; Accepted November 26, 2011; Published November 29, 2011 Citation: Rastogi SK, Jabal JMF, Zhang H, Gibson CM, Haler KJ, et al. (2011) Antibody@Silica Coated Iron Oxide Nanoparticles: Synthesis, Capture of E. coli and SERS Titration of Biomolecules with Antibacterial Silver Colloid. J Nanomedic Nanotechnol 2:121. doi:10.4172/2157-7439.1000121 Copyright: © 2011 Rastogi SK, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Antibody@Silica Coated Iron Oxide Nanoparticles: Synthesis, Capture of E. coli and SERS Titration of Biomolecules with Antibacterial Silver Colloid Shiva K. Rastogi 1 *, Jamie M. F. Jabal 2 , Huijin Zhang 3 , Charlene M. Gibson 1 , Kevin J. Haler 4 , You Qiang 3 , D. Eric Aston 2 and A. Larry Branen 4 1 Department of Chemistry, University of Idaho, Moscow, ID - 83844-2343 2 Department of Chemical and Materials Engineering, University of Idaho, Moscow, ID - 83844, USA 3 Departmental of Physics and Environmental Science Program, University of Idaho, Moscow, ID - 83844, USA 4 Biosensors and Nanotechnology Applications Laboratory, University of Idaho, 1031 N Academic Way, Coeur d’ Alene, ID - 83814, USA Abstract Silica coated iron oxide (SiO 2 /Fe 3 O 4 + γ-Fe 2 O 3 ) nanoparticles (SIO-NPs; 75±10 nm in diameter) were prepared by encapsulation of iron oxide NPs with silica using sol-gel method and characterized through spectroscopy methods. The SIO NPs were chemically activated by cyanogens bromide and then functionalized with Escherichia coli (E. coli) antibodies. These immuno-magnetic (IM NPs) were used to capture and concentrate E. coli from ~ 180 cfu/ mL suspension. The identiication of bacteria was performed by plating on nutrient agar, luorescent microscopy and scanning electron microscopy. Surface enhanced Raman spectroscopy (SERS) was used to identify different biomolecules of bacterial cell upon the interaction of colloidal silver nanoparticle (Ag NPs 6±4 nm) at different period of time. In our previous report we demonstrated the antibacterial property of colloidal Ag NPs. Therefore, current approach, using IM, and Ag NPs and SERS, provide detailed molecular identiication of E. coli as Ag NPs interact over the time. This method would be applicable for food safety, environment protection, biological threat material, antibacterial and other routine E. coli identiication projects.