Nanoscale Structural Switching of Plasmonic Nanograin Layers on Hydrogel Colloidal Monolayers for Highly Sensitive and Dynamic SERS in Water with Areal Signal Reproducibility

DNA-Guided One-Dimensional Plasmonic Nanostructures for the SERS Bioassay

Plasmonic nanostructures have a desirable surface-enhanced Raman scattering (SERS) response related to particle spacing. However, precisely controlling the distance of plasmonic nanostructures is still a challenge. DNA has the merit of specific recognition, and flexible modification of functional groups, which can be used to flexibly adjust the gaps between plasmonic nanostructures for improving the stability of SERS. In this paper, DNA-guided gold nanoparticles formed one-dimensional ordered structures and they were self-assembled at the water-oil interface by a bottom-up approach. Notably, an output switching strategy successfully transfers a small amount of target into a large amount of reporter DNA; thereby, Raman probes are captured on the sensing interface and achieve the SERS assay of microRNA 155 (miRNA-155). This study is an exciting strategy for obtaining ordered plasmonic structures and providing surveillance, which is important for the clinical diagnosis of early-stage cancer.

Multifunctional biosensor constructed by Ag-coating magnetic-assisted unique urchin core porous shell structure for dual SERS enhancement, enrichment, and quantitative detection of multi-components inflammatory markers

The simultaneous, precise, and quantitative detection of multi-components inflammatory markers (IMs) in sepsis serum by surface-enhanced Raman scattering (SERS) remains a challenging problem. A novel, multifunctional biosensor with dual enrichment and enhancement was designed for the ultrasensitive and quantitative analysis of multi-components IMs. The biosensor contains SERS tags-unique urchin core/porous shell (CPS) structure modified with Raman reporters (RaRs), magnetic assist-Ag coated Fe₃O₄ magnetic nanoparticles (Ag MNPs) modified with internal standard (IS), and then aptamer (Apt) modification to form the sandwich structure (Ag MNPs/IMs/CPS). This multifunctional sensor used for IM_S detection has the following innovations: The intensity ratio I_RaRs/I_IS with Lg C_IMs present a good and wide linear relationship to achieve the simultaneous, precise, and quantitative detection of IM_S in serum; The detection results display ultrasensitivity, and the limit of detection (LOD) for CRP, IL-6, and PCT is 100 fg/mL, 0.1 fg/mL, and 1.0 fg/mL, which is lower than other detection techniques; The calculated data of clinical blood samples of sepsis by this SERS method is consistent with the hospital results, and can provide more compositional data of IMs. Thus, this combined approach developed a sensing platform for rapid screening, accurate evaluation, early warning, and diagnosis of sepsis.

Surface-enhanced Raman scattering-active AuNR array cellulose films for multi-hazard detection

In this study, we report a surface-enhanced Raman scattering (SERS)-active array film, which is based on regenerated cellulose hydrogels and gold nanorods (AuNRs), by combining a silicon rubber mask with a vacuum filtration method. This strategy enables the direct AuNR array formation on hydrogel surface with a precisely controlled number density. Moreover, the control of interparticle nanogap has been realized by the spatial deformation of hydrogels. A decrease in gaps between AuNRs deposited on hydrogels can result in SERS enhancement because 3D porous hydrogel structures turned into 2D closely packed hydrogel films during drying. In our experiments, SERS sensor arrays show excellent SERS activity to detect rhodamine 6 G and thiram down to 10 pM and 100 fM with competitive enhancement factors of 3.9 × 10⁸ and 9.5 × 10⁹, respectively. Importantly, the resultant SERS-active arrays with nine sensor units can efficiently detect nine different analytes on a single substrates at a time. Moreover, we demonstrate that physical bending has little effect on the SERS activity of flexible AuNR array hydrogel films, which indicates the high reproducibility of SERS measurement. This SERS array film has great potential to simultaneously detect multiple hazards for the practical application of SERS analysis.

Single-Step Fabrication of High-Throughput Surface-Enhanced Raman Scattering Substrates

The combination of surface-enhanced Raman scattering (SERS) with high-throughput screening (HTS) has significant importance for highly sensitive and massive workload assays. Although fabrication of HTS-SERS substrates can be achieved by several methods, the high cost as well as large-equipment dependence limit their applications. Here, we report a simple method to fabricate HTS-SERS substrates within one-step process. The HTS-SERS substrate is fabricated by simply UV-irradiating a fluoroalkylsilane (FAS)-modified liquid-repellent TiO₂ surface in AgNO₃ solution through a photomask. Owing to the photocatalytic nature of TiO₂, the UV irradiation simultaneously triggers the degradation of the attached FAS and the generation of liquid-adhesive Ag nanoparticles (NPs) on exposed area. A HTS-SERS substrate could be directly obtained after UV irradiation. The deposited Ag NPs evidently enhance Raman signals, and the significant difference between the wettability of exposed area and masked area enables fast formation of high-throughput liquid droplet arrays through a simple dragging solution process. The fabrication method is applicable to various substrate materials, to introduce additional functionalities. The photocatalytic activity of TiO₂ also allows us to photobleach the residual analyte and Ag NPs after detection to recycle substrate. This single-step method is a highly promising candidate for the fabrication of HTS-SERS substrates.