Study on biological activity of nanoparticles and immunosensor design towards pathogen detection

Biological activities of iron-gold structures having magnetic properties and different shapes (sphere, rod, cube) have been studied. Sphere shaped particles have been observed to have the highest bio-compatibility, and a sample immunosensor model has been designed to use avidin attached sphere particles for pathogen detection. Biologic activity studies have been done to identify bio-compatibility and bio-characterization of the particles, reporting: antimicrobial and anti-oxidant activities, cytotoxicity on healthy cell lines and anti-carcinogen effects on some cancer cell lines, genotoxic effects, attachment capacity to bacterial surfaces have been investigated. Antioxidant effects of the particles have been measured in terms of percent DPPH (2,2-diphenyl-1-picrylhydrazyl) elimination and inhibition of lipid peroxidation. The highest DPPH elimination (69.1 %) has been found with avidin attached sphere particles at 5mg/mL concentration. Similarly, avidin attached sphere particles have shown the highest activity (44.8 %) of lipid peroxidation elimination at the same concentration. Thus, sphere particles has been found to be advantageous and sphere shaped avidin attached nanoparticles have been used in the rest of our studies. With the purpose of determining anti-carcinogen effects of nanoparticles, cell lines of colorectal cancer (CCL-221), cervix cancer (HeLa) and breast cancer (Mcf-7) have been studied. A healthy cell line (gingival fibroblast) has been studied for determining cytotoxic effects of the particles. The highest anti-carcinogen effect (34%) has been exhibited by sphere nanoparticles at 0.1mg/mL concentration. The cytotoxic effect of the particle at the same dosage on gingival fibroblast cell has been found out to be 19 percent. A genotoxicity test has been applied for measuring the DNA damage percentage that can be caused by the nanoparticles. Comet test with sphere and avidin attached sphere shaped nanoparticles has been applied on lymphocytes isolated from human blood at varying concentrations (0.005 ? 0.1 mg/mL) and no genotoxic effect has been observed (0.66%). In all studies, whether a correlation exists between the measured results and the increasing nanoparticle concentrations, and the confidence level of results have been found to be significant (p < 0.01). In the conducted attachment studies, it has been observed that sphere shaped nanoparticles have been attached successfully on the L. monocytogenes target bactery (5.7 x 106 cfu/mL bacteria out of 2.8 x 107 cfu/mL live bacteria). In the immunosensor model designed with biologically characterized nanoparticles high and selective attachment to L. monocytogenes has been observed (4.6 x 107 cfu/mL out of 2.1 x 106 cfu/mL bacteria).In order to determine immunosensor success in a natural environment milk medium has been chosen and studies have been made with Raman device to determine detection success on target bactery in milk. Using the Raman device intensified Raman scattering (SERS) stronger signals have been obtained with increasing concentrations and these measurements have been found out to be in accordance with the attachment results.