In this present study the bioconjugated fluorescent silica nanoparticles give an efficient fluorescent-based immunoassay for the detection of pathogen. The synthesized silica nanoparticles were polydispersed and the size of the silica nanoparticles was in the range of 114–164？nm. The energy dispersive X-ray spectrophotometer showed the presence of silica at 1.8？kev and the selected area diffractometer showed amorphous nature of silica nanoparticles. The FTIR spectrum confirmed the attachment of dye and carboxyl group onto the silica nanoparticles surface. The fluorescent silica nanoparticles showed highly efficient fluorescence and the fluorescent emission of silica nanoparticles occurred at 536？nm. The SEM image showed the aggregation of nanoparticles and bacteria. The growth of the pathogenic E. coli was controlled using silica nanoparticles; therefore silica nanoparticles could be used in food packaging material, biomedical material, and so forth. This work provides a rapid, simple, and accurate method for the detection of pathogen using fluorescent-based immunoassay. 1. Introduction The fundamental building blocks of nanotechnology are nanoparticles [1]. The particulate dispersions or solid particles with a size in the range of 10–1000？nm are called nanoparticles [2]. Silica is encompassed of a honeycomb-like porous structure with hundreds of empty channels. Due to their unique properties such as high surface areas, large pore volumes, tuneable pore sizes with a narrow distribution, and tuneable particle diameters, currently silica nanoparticles have been intensively investigated in materials research [3]. Because of their simple preparation and possible applications in several fields, dispersed, uniform, and amorphous silica nanoparticles have produced specific interest [4]. Generally two methods are being used for the preparation of silica nanoparticles, such as microemulsion which is used to prepare the dye-doped and magnetic nanoparticles and stober method which is used to prepare pure silica and organic dye doped silica nanoparticles. The morphology of the nanoparticles can be controlled through the parameters involved in the process [5]. In stober process, due to the hydrolysis process, the ethoxy groups are replaced by TEOS; the hydrolysis reaction initiates by the attachment of hydroxyl anions on TEOS molecules [6, 7]. The condensation reaction occurs immediately after hydrolysis reaction. The Si–O–Si bridges are formed by the alcohol condensation of hydroxyl group of intermediate reaction with ethoxy group of other TEOS, or the water
References
[1]
A. Leela and M. Vivekanandan, “Tapping the unexploited plant resources for the synthesis of silver nanoparticles,” African Journal of Biotechnology, vol. 7, no. 17, pp. 3162–3165, 2008.
[2]
V. J. Mohanraj and Y. Chen, “Nanoparticles—a review,” Tropic Journal of Pharmaceutical Research, vol. 5, no. 1, pp. 561–573, 2006.
[3]
H. Wanyika, E. Gatebe, P. Kioni, Z. Tang, and Y. Gao, “Synthesis and characterization of ordered mesoporous silica nanoparticles with tunable physical properties by varying molar composition of reagents,” African Journal of Pharmacy and Pharmacology, vol. 5, no. 21, pp. 2402–2410, 2011.
[4]
L. P. Singh, S. K. Bhattacharyya, G. Mishra, and S. Ahalawat, “Functional role of cationic surfactant to control the nano size of silica powder,” Applied Nanoscience, vol. 1, no. 3, pp. 117–122, 2011.
[5]
W. Tan, K. Wang, X. He et al., “Bionanotechnology based on silica nanoparticles,” Medicinal Research Reviews, vol. 24, no. 5, pp. 621–638, 2004.
[6]
C. J. Brinker and G. W. Scherer, Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing, Academic Press, San Diego, Calif, USA, 1990.
[7]
I. A. M. Ibrahim, A. A. F. Zikry, and M. A. Sharaf, “Preparation of spherical silica nanoparticles: stober silica,” The Journal of American Science, vol. 11, pp. 985–989, 2010.
[8]
K.-S. Kim, J.-K. Kim, and W.-S. Kim, “Influence of reaction conditions on sol-precipitation process producing silicon oxide particles,” Ceramics International, vol. 28, no. 2, pp. 187–194, 2002.
[9]
L. Wang, K. Wang, S. Santra et al., “Watching silica nanoparticles glow in the biological world,” Analytical Chemistry, vol. 78, no. 3, pp. 646–654, 2006.
[10]
H. Ow, D. R. Larson, M. Srivastava, B. A. Baird, W. W. Webb, and U. Wiesnert, “Bright and stable core-shell fluorescent silica nanoparticles,” Nano Letters, vol. 5, no. 1, pp. 113–117, 2005.
[11]
L. Wang, W. Zhao, and W. Tan, “Bioconjugated silica nanoparticles: development and applications,” Nano Research, vol. 1, no. 2, pp. 99–115, 2008.
[12]
J. E. Smith, L. Wang, and W. Tan, “Bioconjugated silica-coated nanoparticles for bioseparation and bioanalysis,” Trends in Analytical Chemistry, vol. 25, no. 9, pp. 848–855, 2006.
[13]
A. P. R. Johnston, E. S. Read, and F. Caruso, “Ultrathin, responsive polymer click capsules,” Nano Letters, vol. 5, no. 5, pp. 953–956, 2005.
[14]
S. P. Chandran, S. Hotha, and B. L. V. Prasad, “Tunable surface modification of silica nanoparticles through “click” chemistry,” Current Science, vol. 95, no. 9, pp. 1327–1333, 2008.
[15]
M. A. Markowitz, P. E. Schoen, P. Kust, and B. P. Gaber, “Surface acidity and basicity of functionalized silica particles,” Colloids and Surfaces A, vol. 150, no. 1–3, pp. 85–94, 1999.
[16]
P. Espiard, J. E. Mark, and A. Guyot, “A novel technique for preparing organophilic silica by water-in-oil microemulsions,” Polymer Bulletin, vol. 24, no. 2, pp. 173–179, 1990.
[17]
X. Wang, L.-H. Liu, O. Ramstr？m, and M. Yan, “Engineering nanomaterial surfaces for biomedical applications,” Experimental Biology and Medicine, vol. 234, no. 10, pp. 1128–1139, 2009.
[18]
N. D. Singho and M. R. Johan, “Complex impedance spectroscopy study of silica nanoparticles via sol-gel method,” International Journal of Electrochemical Science, vol. 7, no. 6, pp. 5604–5615, 2012.
[19]
N. Venkatathri, “Preparation of silica nanoparticle through coating with octyldecyltrimethoxy silane,” Indian Journal of Chemistry A, vol. 46, no. 12, pp. 1955–1958, 2007.
[20]
P. A. R. Sajid and T. Devasena, “Synthesis and characterization of silica nanocomposites for bone applications,” International Research Journal of Pharmaceutical, vol. 3, no. 5, pp. 173–177, 2012.
[21]
T. I. Yang, R. N. C. Brown, L. C. Kempel, and P. Kofinas, “Controlled synthesis of core-shell iron-silica nanoparticles and their magneto-dielectric properties in polymer composites,” Nanotechnology, vol. 22, no. 10, Article ID 105601, pp. 1–8, 2011.
[22]
S.-R. Ryu and M. Tomozawa, “Fictive temperature measurement of amorphous SiO2 films by IR method,” Journal of Non-Crystalline Solids, vol. 352, no. 36-37, pp. 3929–3935, 2006.
[23]
H. El Rassy and A. C. Pierre, “NMR and IR spectroscopy of silica aerogels with different hydrophobic characteristics,” Journal of Non-Crystalline Solids, vol. 351, no. 19-20, pp. 1603–1610, 2005.
[24]
L. T. Zhuravlev, “The surface chemistry of amorphous silica. Zhuravlev model,” Colloids and Surfaces A, vol. 173, no. 1–3, pp. 1–38, 2000.
[25]
A. Beganskiene, V. Sirutkattis, M. Kurtinattiene, R. Juskenas, and A. Kareiva, “FTIR, TEM, NMR investigation of stober silica nanoparticles,” Material Science, vol. 10, no. 4, pp. 287–290, 2004.
[26]
E. Albiter, S. Alfaro, and M. A. Valenzuela, “Photosensitized oxidation of 9,10-dimethylanthracene on dye-doped silica composites,” International Journal of Photoenergy, vol. 2012, Article ID 987606, 8 pages, 2012.
[27]
S. Santra, P. Zhang, K. Wang, R. Tapec, and W. Tan, “Conjugation of biomolecules with luminophore-doped silica nanoparticles for photostable biomarkers,” Analytical Chemistry, vol. 73, no. 20, pp. 4988–4993, 2001.
[28]
G. Canton, R. Ricco, F. Marinello, S. Carmignato, and F. Enrichi, “Modified St？ber synthesis of highly luminescent dye-doped silica nanoparticles,” Journal of Nanoparticle Research, vol. 13, no. 9, pp. 4349–4356, 2011.
[29]
J. Song, H. Kong, and J. Jang, “Bacterial adhesion inhibition of the quaternary ammonium functionalized silica nanoparticles,” Colloids and Surfaces B, vol. 82, no. 2, pp. 651–656, 2011.
[30]
L. Wang, C. Yang, and W. Tan, “Dual-luminophore-doped silica nanoparticles for multiplexed signaling,” Nano Letters, vol. 5, no. 1, pp. 37–43, 2005.
[31]
S. Mascharak, “Synthesis of fluorescent silica nanoparticles conjugated with RGO peptide for detection of invasive human breast cancer cells,” Nanotechnology, vol. 3, no. 8, pp. 37–41, 2010.
[32]
S. Santra, K. Wang, R. Tapec, and W. Tan, “Development of novel dye-doped silica nanoparticles for biomarker application,” Journal of Biomedical Optics, vol. 6, no. 2, pp. 160–166, 2001.
[33]
X. Zhao, L. R. Hilliard, S. J. Mechery et al., “A rapid bioassay for single bacterial cell quantitation using bioconjugated nanoparticles,” Proceedings of the National Academy of Sciences of the United States of America, vol. 101, no. 42, pp. 15027–15032, 2004.
