A wearable surface-enhanced Raman scattering (SERS) sensor has been developed as a patch type to utilize as a molecular sweat sensor. Here, the SERS patch sensor is designed to comprise a sweat-absorbing layer, which is an interface to the human skin, an SERS active layer, and a dermal protecting layer that prevents damage and contaminations. A silk fibroin protein film (SFF) is a basement layer that absorbs aqueous solutions and filtrates molecules larger than the nanopores created in the β-sheet matrix of the SFF. On the SFF layer, a plasmonic silver nanowire (AgNW) layer is formed to enhance the Raman signal of the molecules that penetrated through the SERS patch in a label-free method. A transparent dermal protecting layer (DP) allows laser penetration to the AgNW layer enabling Raman measurement through the SERS patch without its detachment from the surface. The molecular detection capability and time-dependent absorption properties of the SERS patch are investigated, and then, the feasibility of its use as a wearable drug detection sweat sensor is demonstrated using 2-fluoro-methamphetamine (2-FMA) on the human cadaver skin. It is believed that the developed SERS patch can be utilized as various flexible and wearable biosensors for healthcare monitoring.

A surface-enhanced Raman scattering (SERS) sensor comprising silver nanowires (AgNWs) and genetically engineered M13 bacteriophages expressing a tryptophan-histidine-tryptophan (WHW) peptide sequence (BPWHW) was fabricated by simple mixing of BPWHW and AgNW solutions, followed by vacuum filtration onto a glass-fiber filter paper (GFFP) membrane. The AgNWs stacked on the GFFP formed a high density of SERS-active hot spots at the points of nanowire intersections, and the surface-coated BPWHW functioned as a bioreceptor for selective pesticide detection. The BPWHW-functionalized AgNW (BPWHW/AgNW) sensor was characterized by scanning electron microscopy, confocal scanning fluorescence microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy. The Raman signal enhancement and the selective pesticide SERS detection properties of the BPWHW/AgNW sensor were investigated in the presence of control substrates such as wild-type M13 bacteriophage-decorated AgNWs (BPWT/AgNW) and undecorated AgNWs (AgNW). The BPWHW/AgNW sensor exhibited a significantly higher capture capability for pesticides, especially paraquat (PQ), than the control SERS substrates, and it also showed a relatively higher selectivity for PQ than for other bipyridylium pesticides such as diquat and difenzoquat. Furthermore, as a field application test, PQ was detected on the surface of PQ-pretreated apple peels, and the results demonstrated the feasibility of using a paper-based SERS substrate for on-site residual pesticide detection. The developed M13 bacteriophage-functionalized AgNW SERS sensor might be applicable for the detection of various pesticides and chemicals through modification of the M13 bacteriophage surface peptide sequence.

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A sponge-based surface-enhanced Raman scattering (SERS) sensor composed of silver nanowires (AgNWs) coated with hydrophobic hexagonal boron nitride (hBN) was prepared for the simultaneous separation and detection of organic pollutants.

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A cyclodextrin-decorated gold nanosatellite (AuNSL) substrate was developed as a surface-enhanced Raman scattering sensor for the selective sensing of bipyridylium pesticides such as paraquat (PQ), diquat (DQ), and difenzoquat (DIF)....

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A three-dimensional hot-volume plasmonic gold nanoreactor array (3D HPNRA) composed of gold nanodimples decorated with high-density gold nanoparticles on a 3D curved surface is developed for ultrasensitive immunoassays. The 3D HPNRA generates volumetric hotspots inside the 3D space, and a significant plasmonic coupling effect is created, forming an inclusion complex with probe gold nanoparticles (AuNP probes) coated with a detection antibody (Ab). Due to multiple plasmonic coupling effects inside 3D spaces, the 3D HPNRA is utilized as an ultrasensitive SERS-based detection platform after functionalization of the 1st Ab for cardiac troponin I (cTnI), which is selected as a model antigen for immunoassay demonstration. After integration of the 3D HPNRA with a 3D-printed well plate, ELISA is performed using the AuNP probes, and a portable Raman instrument is subsequently used for quantitative immunoassays. As a result, the 3D HPNRA coupled with the AuNP probes showed ∼400-fold enhanced sensitivities of 22.9 and 27.8 fg/mL for cTnI spiked in PBS and FBS, respectively, compared to conventional ELISA. The developed 3D HPNRA with the coupling of AuNP probes is expected to be applied for ultrasensitive immunoassays, especially for early disease diagnosis and the discovery of biomarkers that exist in an ultralow concentration range.