The incorporation of nanotechnology into molecular biology and medicine has resulted in active developments of a new emerging research area, nanomedicine which offers exciting opportunities for discovering new materials, processes, and phenomena (Whitesides, G. M, 2003). Nanoparticles play vital role as imaging contrast agents in various bio-imaging and pathogenic detection modalities including fluorescence microscopy, Confocal laser scanning microscopy, positron emission tomography, single photon emission computed tomography ultrasound imaging, magnetic resonance imaging, plasmon resonance scattering, optical coherence tomography and magneto motive (Robabeh Rezaeipoor et al., 2009). Bacteria can lead to serious diseases and environmental contamination, and bring a huge public health burden (Woodford N, Livermore DM, 2009). Staphylococcus aureus is a spherical gram-positive bacterium; infections by this pathogen are often found in the skin, soft-tissue, bone, joint, and endovascular disorders (Lowy FD, 1998).
Biological molecules, viz. antibody, antibiotics, carbohydrates, and other small organic molecules, bound with nanoparticles for bacterial labeling and detection. Currently, the conjugated antibiotic on the magnetite nanoparticles are able to bind on the natural receptor located on bacterial cell-wall and therefore, capture and separate the bacteria effectively under external magnetic fields (Longyan chen et al., 2012).
The property of super paramagnetism and low down toxicity along with greater surface/area ratio makes multifunctional magnetic nanoparticles like magnetite (Fe3O4) most impressive for a number of real and challenging applications (Jana Drbohlavova et al., 2009). For applications in food bacterial detection, magnetic nanoparticles are usually coated with polymers, bounded to the particle through organic linkers. This type of coating is capable to identify specific molecules and ions for their binding onto the surface of cell wall of bacterium with improved stability [Raul G.Lopez et al., 2012].
Further surface modification can facilitate the addition of functional groups, such as amino and carboxylic acids, making subsequent conjugations easy. Hence, iron oxide nanoparticles can carry diverse ligands, such as peptides, small molecules, proteins, antibodies and nucleic acids. Therefore, iron oxide nanoparticles have been used for the identification and quantification of several targets, including mRNA, DNA, viruses, bacteria and cells [Manuel Perez et al., 2011]. MNPs conjugated with fluorescent dye such as rhodamine B used as biosensor for the detection of bacteria in food.