An anti-fouling nanoplasmonic SERS substrate for trapping and releasing a cationic fluorescent tag from human blood solution.
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 (10-6M) 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.
Department of Chemical Engineering, National Cheng Kung University, Tainan 70101, Taiwan. tcwen@mail.ncku.edu.tw.
Kundan
K
Sivashanmugan
Department of Chemical Engineering, National Cheng Kung University, Tainan 70101, Taiwan. tcwen@mail.ncku.edu.tw.
Po-Chun
PC
Liu
Department of Chemical Engineering, National Cheng Kung University, Tainan 70101, Taiwan. tcwen@mail.ncku.edu.tw.
Kai-Wei
KW
Tsai
Department of Chemical Engineering, National Cheng Kung University, Tainan 70101, Taiwan. tcwen@mail.ncku.edu.tw.
Ying-Nien
YN
Chou
Department of Chemical Engineering, National Cheng Kung University, Tainan 70101, Taiwan. tcwen@mail.ncku.edu.tw.
Chen-Hsueh
CH
Lin
R&D Center for Membrane Technology and Department of Chemical Engineering, Chung Yuan Christian University, Chung-Li, Taoyuan 320, Taiwan.
Yung
Y
Chang
Department of Chemical Engineering, National Cheng Kung University, Tainan 70101, Taiwan. tcwen@mail.ncku.edu.tw.
Ten-Chin
http://orcid.org/0000-0001-6094-0481
TC
Wen
D000327:Adsorption; D002412:Cations; D006801:Humans; D008689:Methacrylates / Q000737:chemistry; D053657:Platelet-Rich Plasma / Q000737:chemistry*; D015203:Reproducibility of Results; D012394:Rosaniline Dyes / Q000032:analysis*; D013059:Spectrum Analysis, Raman; D013499:Surface Properties
D002412:Cations; D008689:Methacrylates; D012394:Rosaniline Dyes; C521589:sulfobetaine methacrylate polymer; C005095:malachite green