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

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 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.

Mutated Human P-Selectin Glycoprotein Ligand-1 and Viral Protein-1 of Enterovirus 71 Interactions on Au Nanoplasmonic Substrate for Specific Recognition by Surface-Enhanced Raman Spectroscopy

“…The Ag/Au alloy film SPR peak at 485 nm significantly shifted after the Ag/Au alloy film was dealloyed. Two strong SPR shifts appeared at 681 nm for Aup_150s (1 Å/s) and 735 nm for Aup_120s (1 Å/s) compared to those for a deposition rate of 0.3 Å/s (649 nm for Aup_150s and 688 nm for Aup_120s); these peaks are attributed to the strong multi-polarization electric field coupling in small porous cavities [24][25][26][27]33]. COMSOL was used to calculate the optical properties of the optimized Au nanoporous substrate as detailed in SI.…”

“…The SERS effect was averaged from twenty consecutive measurements. The commercial software COMSOL (version Multiphysics ® 2019) was applied to calculate the EM field distribution on the Au nanoporous substrates [25,27].…”

“…Raman spectroscopy can be used to analyze bio-species with or without a solution state; however, weak Raman signals and limited information are obtained [22,23]. Surface-enhanced Raman spectroscopy (SERS) can be used to investigate bio-species via Raman-active modes [24][25][26][27][28][29]. Detection mainly involves a chemical effect and an electromagnetic (EM) effect [24,[30][31][32].…”

“…Chemical specificity and high sensitivity can be obtained via the SERS effect [24]. Generally, substrates roughened using metal (Au, Ag) nanoparticles or patterned nanostructures are used to investigate bio-species, with a high SERS effect and a high enhancement factor [25][26][27]. The SERS effect strongly depends on the geometry of NSs in the micro-environment.…”

Bioinspired Surfaces with Superamphiphobic Properties: Concepts, Synthesis, and Applications

“…Considering many practical applications, such as clothing, kitchenware, oil pipeline, and so on, antifouling property is of great significance in a wide range of areas . Yuan et al have prepared the superamphiphobic coating with composite ethylene tetrafluoroethylene‐polyaniline functionalized carbon nanotubes.…”