Abstract
We present a label-free, optical nano-biosensor based on the Localized Surface Plasmon Resonance (LSPR) that is observed at the metal-dielectric interface of silver nano-disk arrays located periodically on a sapphire substrate by Electron-Beam Lithography (EBL). The nano-disk array was designed by finite-difference and time-domain (FDTD) algorithm-based simulations. Refractive index sensitivity was calculated experimentally as 221-354 nm/RIU for different sized arrays. The sensing mechanism was first tested with a biotin-avidin pair, and then a preliminary trial for sensing heat-killed Escherichia coli (E. coli) O157:H7 bacteria was done. Although the study is at an early stage, the results indicate that such a plasmonic structure can be applied to bio-sensing applications and then extended to the detection of specific bacteria species as a fast and low cost alternative.
Highlights
The need for rapid, specific, sensitive, inexpensive, in-field and real-time detection of target analytes in solutions with an unknown content has made “biosensors” gain importance especially in fields such as environmental monitoring, pollutant detection, medical diagnostics, and biological warfare defense
EZ_Link Sulfo-NHS-SS-Biotin (21331) and Avidin (21121) were purchased from Pierce. 11-Amino-1-undecanetiol, hydrochloride [A423-10], and 6-Hydroxy-1Hexanethiol were purchased from Probior
The dimensions are selected to keep the operation at around 400-500 nm. By this way it is guaranteed to stay at optical frequencies after surface modification steps that cause red shift. This will gain more importance in future studies that involve the detection of real pathogenic bacteria where more complicated surface functionalization may be necessary since working at this portion of the spectrum provides a means for gentle detection that does not destroy the structure of matter [39]
Summary
The need for rapid, specific, sensitive, inexpensive, in-field and real-time detection of target analytes in solutions with an unknown content has made “biosensors” gain importance especially in fields such as environmental monitoring, pollutant detection, medical diagnostics, and biological warfare defense. A subcategory that biosensors are used is the detection of food-borne pathogens. Food borne pathogens cause infectious or toxic diseases upon the consumption of contaminated water and/or food. There are newer, more rapid methods such as polymerase chain reaction (PCR) and Enzyme linked immunosorbent assay (ELISA) [2,3,4]. These methods require extensive pretreatment prior to analysis, such as an enrichment step that involves growing bacteria on a nutrient agar to detectable levels; equipped laboratory and highly trained personnel who can operate the instruments and interpret the results
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