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Issue 8, 2017
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An anti-fouling nanoplasmonic SERS substrate for trapping and releasing a cationic fluorescent tag from human blood solution

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Abstract

In bioenvironmental detection, surface-enhanced Raman scattering (SERS) signals are greatly affected by anti-specific biomolecule adsorption, which generates strong background noise, reducing detection sensitivity and selectivity. It is thus necessary to modify the SERS substrate surface to make it anti-fouling to maintain excellent SERS signals. Herein, we propose a zwitterionic copolymer, namely poly(glycidyl methacrylate-co-sulfobetaine methacrylate) (poly(GMA-co-SBMA)), for the surface modification of SERS substrates, which were fabricated and characterized spectroscopically. The copolymer was grafted onto Ag nanocubes (NCs) on an Ag surface with massive nanogaps via 1,2-ethanedithiol, which acted as a metal–insulator–metal (MIM) substrate. The high density of poly(GMA-co-SBMA) grafted near NCs favored the formation of connections between adjacent NCs, causing strong surface plasmon resonance at these junctions. With the zwitterionic-copolymer-modified surface, the adhesion of large biomolecules in platelet-rich plasma (PRP) solution can be effectively resisted, as determined from immunoassay and fibrinogen adsorption results. The SERS signals for malachite green (MG) in PRP solution (10−6 M) were effectively distinguished using the copolymer-grafted MIM substrate. MG was deposited on adjacent copolymer-grafted NCs, which amplified the SERS signals. Moreover, the copolymer connected adjacent NCs, inducing the electromagnetic effect at copolymer-grafted surfaces, which improved the SERS mechanism. The hydration process restructured the MG-trapped copolymer-grafted surface, decreasing the number of MG characteristic peak regions and increasing that of the copolymer regions. These results reveal that grafting a copolymer onto an MIM substrate allows MG to be easily trapped and released in complex biomatrices and increases surface reproducibility due to anti-fouling, leading to high SERS enhancement.

Graphical abstract: An anti-fouling nanoplasmonic SERS substrate for trapping and releasing a cationic fluorescent tag from human blood solution

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Supplementary files

Article information


Submitted
14 Oct 2016
Accepted
09 Jan 2017
First published
12 Jan 2017

Nanoscale, 2017,9, 2865-2874
Article type
Paper

An anti-fouling nanoplasmonic SERS substrate for trapping and releasing a cationic fluorescent tag from human blood solution

K. Sivashanmugan, P. Liu, K. Tsai, Y. Chou, C. Lin, Y. Chang and T. Wen, Nanoscale, 2017, 9, 2865
DOI: 10.1039/C6NR08077D

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