Highly sensitive biosensing using arrays of plasmonic Au nanodisks realized by nanoimprint lithography

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Highly sensitive biosensing using arrays of plasmonic Au nanodisks realized by nanoimprint lithography
Seung-Woo Lee; K S Lee; Jun Hyoung Ahn; J J Lee; Min-Gon Kim; Yong Beom Shin
Bibliographic Citation
ACS Nano, vol. 5, no. 2, pp. 897-904
Publication Year
We describe the fabrication of elliptical Au nanodisk arrays as a localized surface plasmon resonance (LSPR) sensing substrate for clinical immunoassay via thermal nanoimprint lithography (NIL) and enhancement in the sensitivity of the detection of the prostate-specific antigen (PSA) using the precipitation of 5-bromo-4-chloro-3-indolyl phosphate p-toluidine/nitro blue tetrazolium (BCIP/NBT), catalyzed by alkaline phosphatase. Au nanodisks were fabricated on glass through an unconventional tilted evaporation, which could preserve the thickness of imprinted resists and create an undercut beneficial to the subsequent lift-off process without any damage to pattern dimension and the glass while removing the residual polymers. To investigate the optically anisotropic property of the LSPR sensors, a probe light with linear polarization parallel to and perpendicular to the long axis of the elliptical nanodisk array was utilized, and their sensitivity to the bulk refractive index (RI) was measured as 327 and 167 nm/RIU, respectively. To our knowledge, this is the first application of enzyme-substrate reaction to sandwich immunoassay-based LSPR biosensors that previously suffered from a low sensitivity due to the short penetration depth of the plasmon field, especially when large-sized antibodies were used as bioreceptors. As a result, a large change in local refractive index because of the precipitation on the Au nanodisks amplified the wavelength shift of the LSPR peak in the vis-NIR spectrum, resulting in femtomolar detection limits, which was ∼105-fold lower than the label-free detection without the enzyme precipitation. This method can be extended easily to the other clinical diagnostics with a high sensitivity.
enzymatic precipitationlocalized surface plasmon resonancenanodisk arraysnanoimprint lithographyprostate-specific antigen
Amer Chem Soc
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Division of Research on National Challenges > Bionanotechnology Research Center > 1. Journal Articles
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