Au/SiNCA-based SERS analysis coupled with machine learning for the early-stage diagnosis of cisplatin-induced liver injury

Cisplatin has been widely applied in the clinical treatment of various cancers, whereas liver injury induced by its hepatotoxicity is still a severe issue. Reliable identification of early-stage cisplatin-induced liver injury (CILI) can improve clinical care and help to streamline drug development. Traditional methods, however, cannot achieve enough information at the subcellular level due to the requirement of the labeling process and low sensitivity. To overcome these, we designed an Au-coated Si nanocone array (Au/SiNCA) to fabricate the microporous chip as the surface-enhanced Raman scattering (SERS) analysis platform for the early diagnosis of CILI. A CILI rat model was established, and the exosome spectra were obtained. The principal component analysis (PCA)-representation coefficient-based k-nearest centroid neighbor (RCKNCN) classification algorithm was proposed as the multivariate analysis method to build the diagnosis and staging model. The PCA-RCKNCN model has been validated to achieve a satisfactory result, with accuracy and AUC of over 97.5%, and sensitivity and specificity of over 95%, indicating that SERS combined with the PCA-RCKNCN analysis platform can be a promising tool for clinical applications.

Flexible Surface-Enhanced Raman Scattering Chip: A Universal Platform for Real-Time Interfacial Molecular Analysis with Femtomolar Sensitivity

We propose and demonstrate a flexible surface-enhanced Raman scattering (SERS) chip as a versatile platform for femtomolar detection and real-time interfacial molecule analysis. The flexible SERS chip is composed of a flexible and transparent membrane and embedded plasmonic dimers with ultrahigh particle density and ultrasmall dimer gap. The chip enables rapid identification for residuals on solid substrates with irregular surfaces or dissolved analytes in aqueous solution. The sensitivity for liquid-state measurement is down to 0.06 molecule per dimers for 10^-14 mol·L^-1 Rhodamine 6G molecule without molecule enrichment. Strong signal fluctuation and blinking are observed at this concentration, indicating that the detection limit is close to the single-molecule level. Meanwhile, the homogeneous liquid environment facilities accurate SERS quantification of analytes with a wide dynamic range. The synergy of flexibility and liquid-state measurement opens up avenues for the real-time study of chemical reactions. The reduction from p-nitrothiophenol (PNTP) to p-aminothiophenol (PATP) in the absence of the chemical reducing agents is observed at liquid interfaces by in situ SERS measurements, and the plasmon-induced hot electron is demonstrated to drive the catalytic reaction. We believe this robust and feasible approach is promising in extending the SERS technique as a general method for identifying interfacial molecular traces, tracking the evolution of heterogeneous reactions, elucidating the reaction mechanisms, and evaluating the environmental effects such as pH value and salty ions in SERS.

Sensing refractive index gradients along dielectric nanopillar metasurfaces

Metasurfaces exhibit unique optical properties that depend on the ratio of their refractive index and that of their surroundings. As such, they are effective for sensing global changes in refractive index based on the shifts of resonances in their reflectivity spectra. However, when used as a biosensor, the metasurface can be exposed to a spatial distribution of biomolecules that brings about gradients in refractive index along the plane of the metasurface. Such gradients produce complex global reflectivity spectrum but with distinct optical enhancements in localized areas along the metasurface. Here, we propose a unique sensing paradigm that images and maps out the optical enhancements that are correlated with the spatial distribution of the refractive index. Moreover, we designed a metasurface whose resonances can be tuned to detect a range of refractive indices. Our metasurface consists of silicon nanopillars with a cylindrical nanotrench at their centers and a metal plane at the base. To assess its feasibility, we performed numerical simulations to show that the design effectively produces the desired reflectivity spectrum with resonances in the near-infrared. Using an incident light tuned to one of its resonances, our simulations further show that the field enhancements are correlated with the spatial mapping of the gradients of refractive indices along the metasurface.

Surface-enhanced Raman scattering on organic–inorganic hybrid perovskites

For the first time SERS on organic–inorganic hybrid perovskites is explored. The enhancement mechanism is discussed according to charge transfer.