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Results of a comprehensive analytical study of Belarusian icons of the XVIII–XIX centuries are summarized. The mineral pigments used for their creation have been identified. Some patterns of their use were revealed. [ABSTRACT FROM AUTHOR]

Surface enhanced Raman scattering (SERS) is difficult to detect molecules with weak adsorption, like aldehydes. Herein, we fabricated core‐shell Au@Ag‐MOFs nanoparticles as SERS substrate. The shell can be controllably synthesized, with the thickness about 3 nm. After the morphology and SERS activity characterization, Au@Ag‐MOFs were employed to sensitive and label‐free detect p‐chlorobenzaldehyde (PCB) in water samples. The pore structure and large surface area of Ag‐MOFs shell results more adsorption of PCB, dragging more molecules to "hot spots" area. The abundant amino group in Ag‐MOFs allows the occurrence of Schiff base reaction with aldehyde group in PCB. Taking the synergistic effect of both physical and chemical enhancement, SERS signals of PCB were greatly boosted. The method showed good linearity between 5.0×10−12 M to 1.0×10−8 M for PCB with the limit of detection (LOD) down to 3.3×10−12 M. The proposed method has great potential to be a reliable analytical strategy for aldehydes in real samples. [ABSTRACT FROM AUTHOR]

Corrosion inhibitors are widely employed to retard metal corrosion. Highly sensitive detection and adsorption mechanism analysis are the two important aspects for the systematic research of corrosion inhibitors. Surface-enhanced Raman scattering (SERS) spectroscopy has emerged as a promising tool for the high-resolution detection and inhibition mechanism analysis of corrosion inhibitors in recent decades, and is of considerable importance for their selection and optimization. This paper provides an overview of the SERS technique in the study of corrosion inhibitors adsorbed on noble metals (SERS active substrates) and transition metals (non-SERS active substrates). After surface roughening, the SERS enhancement of metal electrodes can be significantly improved, which intensifies the Raman signals of adsorbed inhibitors to provide sufficient information regarding the binding state and adsorption orientation. In addition to roughening the metal surface to obtain strong SERS signals, novel SERS sensors that can amplify the Raman signals of inhibitors regardless of the type or surface state of the metal substrates are introduced, which is conductive to facilitating the real-time detection of inhibitors. The challenges and future prospects of SERS technique in corrosion inhibitor research are discussed. In summary, SERS technique is expected to promote the research development and engineering applications of corrosion inhibitors. [ABSTRACT FROM AUTHOR]

This study reveals a significant improvement in surface-enhanced Raman scattering (SERS) activity of Ag/ZrO2 substrates covered with a few-layer graphene preliminary exposed to ultraviolet (UV) light. The SERS-active substrates are formed by the "silver mirror" deposition of Ag nanoparticles on annealed zirconia blocks. The film composed of ~3 graphene layers is grown on copper foil by a chemical vapor deposition and then wet-transferred to the SERS-active substrates. The graphene-free Ag/ZrO2 samples are found to provide an enhancement of the Raman scattering from rhodamine 6G (R6G) at a micromolar concentration, which is associated with combined effects from the surface plasmon resonance in the Ag nanoparticles and a charge transfer facilitated by zirconium dioxide. It is revealed that the SERS signal from the analyte molecules can be suppressed by a UV exposure of the Ag/ZrO2 samples due to photocatalytic activity of the wide band gap semiconductor. However, if the samples are covered with a few-layer graphene (Gr/Ag/ZrO2) it prevents the dye molecule decomposition upon the UV treatment and improves SERS activity of the substrates. The 365 nm treatment leads to a 40% increase in the 10–6 M R6G SERS spectrum intensity, while the 254 nm irradiation causes it to rise by 47%, which is explained by different responses from the surface and bulk zirconia crystals to the short and long UV wavelengths. This enhancement is attributed to the distinct responses of surface and in-depth zirconia crystals to varied UV wavelengths and underscores the pivotal role of graphene as a protective and enhancing layer. [ABSTRACT FROM AUTHOR]

Ting Lan,1,* Yang Zhao,1,2,* Yu Du,1,3,* Chunyi Ma,1 Rui Wang,1 Qianlei Zhang,1 Shanshan Wang,1 Wenxian Wei,4 Honghua Yuan,2 Qingli Huang1,2 1Medical Technology School of Xuzhou Medical University, Xuzhou City, Jiangsu, 221000, People’s Republic of China; 2Public Experimental Research Center of Xuzhou Medical University, Xuzhou City, Jiangsu, 221004, People’s Republic of China; 3Xuzhou Center for Disease Control and Prevention, Xuzhou City, Jiangsu, 221006, People’s Republic of China; 4Testing Center, Yangzhou University, Yangzhou City, Jiangsu, 225009, People’s Republic of China*These authors contributed equally to this workCorrespondence: Honghua Yuan, Public Experimental Research Center of Xuzhou Medical University, Tong Shan No. 209, Xuzhou, 221004, People’s Republic of China, Tel/Fax +86-516-83262091, Email XUYIyhh@xzhmu.edu.cn Qingli Huang, Medical Technology School, Public Experimental Research Center of Xuzhou Medical University, Tong Shan No. 209, Xuzhou, 221004, People’s Republic of China, Tel/Fax +86-516-83262091, Email qlhuang@xzhmu.edu.cnPurpose: A novel CYPA-targeted, SiO2 encapsulated Au star@AgAu yolk-shell nanostructure (YSNS) was synthesized and used for ovarian cancer early diagnosis and therapy.Methods: Diverse spectroscopic and microscopic methods were utilized to investigate the pattern of the yolk-shell nanostructure. In addition, in vitro and in vivo experiments were carried out.Results: It can be found that the ratio of HAuCl4 and AgNO3 played a critical role in the constitution of the yolk-shell nanostructure. The as-prepared yolk-shell nanostructure showed excellent SERS performance, which could be utilized as SERS substrate for specific sensitivity analysis of ovarian cancer markers cyclophilin A (CYPA) with detectable limit of 7.76*10− 10 μg/mL. In addition, the as-prepared yolk-shell nanostructure possessed outstanding photothermal performance, which could be used as photothermal agent for ovarian cancer therapy. Experiments in vitro and in vivo proved that the as-prepared yolk-shell nanostructures are ideal candidate for early diagnosis and therapy for ovarian cancer in one platform.Conclusion: This work holds promise to offer a new method for the detection and therapy of ovarian cancer in the early stage.Graphical Abstract: Keywords: yolk-shell nanostructure, surface-enhanced Raman scattering, early diagnosis, cancer targeted therapy

A core-shell-satellite nanostructure surface-enhanced Raman scattering (SERS) substrate based on magnetic nanoparticles, metal-organic frameworks (MOFs) and gold nanoparticles (Ag NPs) was established and applied in the simple, rapid and sensitive detection of the organophosphorus pesticide triazophos in agricultural products. MIL-100(Fe)-coated Fe3O4 was prepared by low-temperature cyclic self-assembly method, and Ag NPs were in-situ grown on the surface of MIL-100(Fe)-coated Fe3O4 by silver mirror cycling. The SERS sensing of triazophos residues in apples was carried out. The logarithmic value (Y) of the characteristic peak intensity of triazophos was linearly related to the logarithmic value (X) of its concentration in the range of 0.05–10 mg/L, which was described by the following equation: Y = 0.573 8X + 2.804 (R2 = 0.980). The limit of detection (LOD) was as low as 11.9 mg/L. The recoveries of the developed method ranged from 90.07% to 103.27% at spiked concentrations of 2, 5, and 10 mg/L. Therefore, the prepared SERS substrate has great potential for application in the detection of pesticide residues in foods.

Yayun Qian,1 Yuexing Gu,2 Jialin Deng,3 Zhaoying Cai,3 Yang Wang,3 Ruoyu Zhou,3 Dongxu Zhu,3 Hongmei Lu,4 Zheng Wang1 1Department of Pathology, The Affiliated Hospital of Yangzhou University, Yangzhou University, Yangzhou, People’s Republic of China; 2Institute of Translational Medicine, Medical College, Yangzhou University, Yangzhou, People’s Republic of China; 3Jiangsu Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment of Senile Diseases, Yangzhou University, Yangzhou, People’s Republic of China; 4Department of Pathology, Yangzhou Maternal and Child Health Hospital, Yangzhou, People’s Republic of ChinaCorrespondence: Zheng Wang; Yayun Qian, Email yzdxfsyywz@163.com; yyqian@yzu.edu.cnIntroduction: As the most common malignant tumor in the world, the prognosis of patients with advanced lung cancer remains poor even after treatment. There are many prognostic marker assays available, but there is still more room for the development of high-throughput and sensitive detection of circulating tumor DNA (ctDNA). Surface-enhanced Raman spectroscopy (SERS), a spectroscopic detection method that has received wide attention in recent years, can achieve exponential amplification of Raman signals by using different metallic nanomaterials. Integrating SERS with signal amplification strategy into the microfluidic chip and applying it to ctDNA detection is expected to be an effective tool for the prognosis of lung cancer treatment effect in the future.Methods: To construct a high-throughput SERS microfluidic chip integrated with enzyme-assisted signal amplification (EASA) and catalytic hairpin self-assembly (CHA) signal amplification strategies, using hpDNA-functionalized Au nanocone arrays (AuNCAs) as capture substrates and cisplatin-treated lung cancer mice to simulate the detection environment for sensitive detection of ctDNA in serum of lung cancer patients after treatment.Results: The SERS microfluidic chip constructed by this scheme, with two reaction zones, can simultaneously and sensitively detect the concentrations of four prognostic ctDNAs in the serum of three lung cancer patients with a limit of detection (LOD) as low as the aM level. The results of the ELISA assay are consistent with this scheme, and its accuracy is guaranteed.Conclusion: This high-throughput SERS microfluidic chip has high sensitivity and specificity in the detection of ctDNA. This could be a potential tool for prognostic assessment of lung cancer treatment efficacy in future clinical applications.Keywords: circulating tumor DNA, surface-enhanced Raman scattering, lung cancer, AuNCAs, prognostic assessment

Yuexing Gu,1,2,* Yan Li,3,* Shengjie Ge,1,2 Wenbo Lu,4 Yu Mao,1,2 Miao Chen,1,2 Yayun Qian1,2 1Institute of Translational Medicine, Medical College, Yangzhou University, Yangzhou, People’s Republic of China; 2Jiangsu Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment of Senile Diseases, Yangzhou University, Yangzhou, People’s Republic of China; 3Department of Obstetrics and Gynecology, The Second People’s Hospital of Taizhou City, Taizhou, People’s Republic of China; 4Shanxi Normal University, College of Chemistry and Material Science, Linfen, People’s Republic of China*These authors contributed equally to this workCorrespondence: Yayun Qian, Email yyqian@yzu.edu.cnPurpose: This paper aims to construct a surface-enhanced Raman spectroscopy (SERS) biosensor based on functionalized Au-Si nanocone arrays (Au-SiNCA) using a dual signal amplification strategy (SDA-CHA) to evaluate telomerase activity during epithelial-mesenchymal transition (EMT) in laryngeal carcinoma (LC).Methods: A SERS biosensor based on functionalized Au-SiNCA was designed with an integrated dual-signal amplification strategy to achieve ultrasensitive detection of telomerase activity during EMT in LC patients.Results: Labeled probes (Au-AgNRs@4-MBA@H1) and capture substrates (Au-SiNCA@H2) were prepared by modifying hairpin DNA and Raman signal molecules. Using this scheme, telomerase activity in peripheral mononuclear cells (PMNC) could be successfully detected with a limit of detection (LOD) as low as 10− 6 IU/mL. In addition, biological experiments using BLM treatment of TU686 effectively mimicked the EMT process. The results of this scheme were highly consistent with the ELISA scheme, confirming its accuracy.Conclusion: This scheme provides a reproducible, selective, and ultrasensitive assay for telomerase activity, which is expected to be a potential tool for the early screening of LC in future clinical applications.Keywords: surface-enhanced Raman scattering, telomerase, laryngeal carcinoma, epithelial-mesenchymal transition, Au-SiNCA

Abrin and ricin, both type II ribosome-inactivating proteins, are toxins of significant concern and are under international restriction by the Chemical Weapons Convention and the Biological and Toxin Weapons Convention. The development of a rapid and sensitive detection method for these toxins is of the utmost importance for the first emergency response. Emerging rapid detection techniques, such as surface-enhanced Raman spectroscopy (SERS) and lateral flow assay (LFA), have garnered attention due to their high sensitivity, good selectivity, ease of operation, low cost, and disposability. In this work, we generated stable and high-affinity nanotags, via an efficient freezing method, to serve as the capture module for SERS-LFA. We then constructed a sandwich-style lateral flow test strip using a pair of glycoproteins, asialofetuin and concanavalin A, as the core affinity recognition molecules, capable of trace measurement for both abrin and ricin. The limit of detection for abrin and ricin was 0.1 and 0.3 ng/mL, respectively. This method was applied to analyze eight spiked white powder samples, one juice sample, and three actual botanic samples, aligning well with cytotoxicity assay outcomes. It demonstrated good inter-batch and intra-batch reproducibility among the test strips, and the detection could be completed within 15 min, indicating the suitability of this SERS-LFA method for the on-site rapid detection of abrin and ricin toxins.

Optical bioassays are challenged by the growing requirements of sensitivity and simplicity. Recent developments in the combination of redox cycling with different optical methods for signal amplification have proven to have tremendous potential for improving analytical performances. In this review, we summarized the advances in optical bioassays based on the signal amplification of redox cycling, including colorimetry, fluorescence, surface-enhanced Raman scattering, chemiluminescence, and electrochemiluminescence. Furthermore, this review highlighted the general principles to effectively couple redox cycling with optical bioassays, and particular attention was focused on current challenges and future opportunities.

This paper reports a two-step method for preparing a metal-organic framework (MOF) MIL-101 (Fe) based substrate with high sensitivity and stability for surface-enhanced Raman scattering (SERS) analysis. Firstly, MIL-101 (Fe) nanoparticles were synthesized using a traditional solvothermal method. Next, gold nanoparticles (AuNPs) were produced through a reduction method, and the AuNPs/MIL-101 (Fe) composite substrate was created by combining MIL-101 (Fe) with AuNPs. The adsorption capacity of the substrate and its SERS activity after multiple cleaning were tested. Using Rhodamine 6 G (R6G) as the probe molecule, the substrate's detection capability reached 10-8 M, with a relative standard deviation (RSD) of approximately 13.15%, indicating excellent SERS performance and uniformity. The ideal detection capability for sulfapyridine using the composite matrix can be as low as 10-6 M. This proposed substrate is convenient and efficient, holding great potential for the rapid and sensitive detection of antibiotic residues and other environmental pollutants.

Abstract Glycans are the most abundant fundamental biomolecules, but profiling glycans is challenging due to their structural complexity. To address this, a novel glycan detection platform is developed by integrating surface‐enhanced Raman spectroscopy (SERS), boronic acid receptors, and machine learning tools. Boronic acid receptors bind with glycans, and the reaction influences molecular vibrations, leading to unique Raman spectral patterns. Unlike prior studies that focus on designing a boronic acid with high binding selectivity toward a target glycan, this sensor is designed to analyze overall changes in spectral patterns using machine learning algorithms. For proof‐of‐concept, 4‐mercaptophenylboronic acid (4MBA) and 1‐thianthrenylboronic acid (1TBA) are used for glycan detection. The sensing platform successfully recognizes the stereoisomers and the structural isomers with different glycosidic linkages. The collective spectra that combine the spectra from both boronic acid receptors improve the performance of the support vector machine model due to the enrichment of the structural information of glycans. In addition, this new sensor could quantify the mole fraction of sialic acid in lactose background using the machine learning regression technique. This low‐cost, rapid, and highly accessible sensor will provide the scientific community with another option for frequent comparative glycan screening in standard biological laboratories.

Abstract Tumor cells display heterogenous molecular signatures during the course of cancer and create distinct tumor cell subpopulations which challenge effective therapeutic decisions. Detection and monitoring of these heterogenous molecular events at single cell level are imperative to identify tumor cell subpopulations and to engage the best therapeutic options for the individual patient. Herein, a microfluidic liquid biopsy platform to analyze circulating tumor cells (CTCs) at single cell level is reported. The individual CTCs are captured in an alternating current‐induced microfluidic platform and analyzed by using surface‐enhanced Raman scattering spectroscopy. This platform selectively captures single CTCs from the patient's peripheral blood mononuclear cells. Using cell line models and patient samples, it is shown that the assay can simultaneously detect multiple protein biomarkers on a single CTC. The platform can stratify the CTCs into different subpopulations based on their cancer‐associated protein signature changes in response to drug treatment. This enables the identification of CTC subpopulations that are probably not responding to treatment and may assist clinicians in specifically monitoring and eliminating therapy‐resistant cancer cells within a lesion. This single CTC monitoring chip will likely have high clinical importance in disease diagnosis and treatment monitoring, and advance the knowledge of cancer heterogeneity.

Introduction: In this study, a surface-enhanced Raman scattering (SERS) sensor based on a functionalized Au/Si cap-cone array (Au/Si CCA) was constructed using the identity-release strategy to detect Vimentin changes during epithelial-mesenchymal transition (EMT) in gastric cancer (GC).Methods: The periodic structure of Au/Si CCA, which can form “hot spots” with high density and regular arrangement, is a substrate with excellent performance. Au/Si CCA was functionalized with aptamers as the capture substrate, and Au nanocubes (AuNCs) were modified with 5-carboxyfluorescein (5-FAM) labelled complementary strand as SERS probe. The capture substrate and SERS probe were assembled by hybridization, and the SERS signal intensity of 5-FAM was greatly enhanced. The binding of Vimentin to the aptamer resulted in a broken connection between the SERS sensor Au/Si CCA array and AuNCs, which resulted in a decrease in the signal intensity of 5-FAM. The identity-release strategy requires only a simple step of reaction to achieve rapid detection of target proteins, which has clinical practicability.Results: Using this protocol, the concentration of Vimentin in GES-1 cells could be successfully detected, and the detection limit was as low as 4.92 pg/mL. Biological experiments of Vincristine, Oncovin (VCR)-treated GES-1 cells effectively mimicked the EMT process, and Vimentin changes during EMT could be accurately detected by this method.Discussion: This study provides a selective, ultra-sensitive and accurate assay for Vimentin detection, which may provide a means for the future detection of EMT process in GC.

A general polymerization‐induced strategy is developed to synthesize large‐area (100 cm2) transition metal nitride (TMN: TiN, MoN, WN, VN) porous arrays with high specific surface area (187.5–215.5 m2 g−1) for the first time, which also can be used to prepare TMN porous arrays uniformly doped with multiple elements. The formation of homogeneous organic/inorganic hybrid polymer precursors is a key factor in forming such TMN porous arrays. The TiN porous arrays exhibit an intense blue‐light localized surface plasmon resonance effect centered at 508 nm. The TiN porous arrays also show a remarkable surface‐enhanced Raman scattering (SERS) effect with a Raman enhanced factor of 5.7 × 107 and the lowest detection limit of 1.0 × 10−12 m. They show ultrahigh corrosion resistance and oxidation resistance, which are not available on traditional noble metal and semiconductor SERS substrates. These results suggest the possibility of the development of effective SERS substrates by using cheap TiN to replace the expensive commercial Au substrates.

Biofluid biomarkers, as objective predictors of traumatic brain injury (TBI) pathobiological processes, play an important role in the early detection of TBI. However, the lack of sensitive and rapid detection assays to detect biomarker levels has been an urgent problem. In this study, we devised a novel surface-enhanced Raman scattering (SERS)-based paper lateral flow strip (PLFS) based on gold nanorods (AuNRs) with controlled aspect ratios for the screening and diagnosis of TBI. To improve the sensitivity of the designed device, AuNRs, as the key component of SERS probes, were optimized by controlling the particle morphology, showing great local plasma enhancement. Furthermore, using thionin acetate (THI) as a Raman reporter, the detection performance of PLFS was further improved due to the unique molecular structure of THI. Thus, the constructed PLFS has been demonstrated to be ultrasensitive, with a limit of detection (LOD) reaching ∼10–1 pg·mL–1. Fo r real-world measurements of glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP) in blood samples, the results monitored by the SERS assay were exactly consistent with those obtained through the traditional enzyme-linked immunosorbent assay (ELISA). The above result demonstrated that the developed SERS-PFLS has extensive application prospects in the screening and diagnosis of TBI in the emergency department as point-of-care testing (POCT) and may further shift the paradigm of TBI patient management and clinical outcome in emergency departments. [ABSTRACT FROM AUTHOR]

Molecular recognition of complex isomeric biomolecules remains challenging in surface‐enhanced Raman scattering (SERS) spectroscopy due to their small Raman cross‐sections and/or poor surface affinities. To date, the use of molecular probes has achieved excellent molecular sensitivities but still suffers from poor spectral specificity. Here, we induce "charge and geometry complementarity" between probe and analyte as a key strategy to achieve high spectral specificity for effective SERS molecular recognition of structural analogues. We employ 4‐mercaptopyridine (MPY) as the probe, and chondroitin sulfate (CS) disaccharides with isomeric sulfation patterns as our proof‐of‐concept study. Our experimental and in silico studies reveal that "charge and geometry complementarity" between MPY's binding pocket and the CS sulfation patterns drives the formation of site‐specific, multidentate interactions at the respective CS isomerism sites, which "locks" each CS in its analogue‐specific complex geometry, akin to molecular docking events. Leveraging the resultant spectral fingerprints, we achieve > 97 % classification accuracy for 4 CSs and 5 potential structural interferences, as well as attain multiplex CS quantification with < 3 % prediction error. These insights could enable practical SERS differentiation of biologically important isomers to meet the burgeoning demand for fast‐responding applications across various fields such as biodiagnostics, food and environmental surveillance. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) can boost the pristine Raman signal significantly which could be exploited for producing innovative sensing devices with advanced properties. However, the inherent complexity of SERS systems restricts their further applications in rapid detection, especially in situ detection in narrow areas. Here, we construct an efficient and flexible SERS-based Lab-on-Fiber (LOF) sensor by integrating Ag/Au nanocap arrays obtained by Ag/Au coating polystyrene nanospheres on the optical fiber face. We obtain rich "hot spots" at the nanogaps between neighboring nanocaps, and further achieve SERS performance with the assistance of laser-induced thermophoresis on the metal film that can achieve efficiency aggregation of detected molecules. We achieve a high Raman enhancement with a low detection limitation of 10−7 mol/L for the most efficient samples based on the above sensor. This sensor also exhibits good repeatability and stability under multiple detections, revealing the potential application for in situ detection based on the reflexivity of the optical fiber. [ABSTRACT FROM AUTHOR]

Nanostructures intrinsically possessing two different structural or functional features, often called Janus nanoparticles, are emerging as a potential material for sensing, catalysis, and biomedical applications. Herein, we report the synthesis of plasmonic gold Janus nanostars (NSs) possessing a smooth concave pentagonal morphology with sharp tips and edges on one side and, contrastingly, a crumbled morphology on the other. The methodology reported herein for their synthesis – a single‐step growth reaction – is different from any other Janus nanoparticle preparation involving either template‐assisted growth or a masking technique. Interestingly, the coexistence of lower‐ and higher‐index facets was found in these Janus NSs. The general paradigm for synthesizing gold Janus NSs was investigated by understanding the kinetic control mechanism with the combinatorial effect of all the reagents responsible for the structure. The optical properties of the Janus NSs were realized by corelating their extinction spectra with the simulated data. The size‐dependent surface‐enhanced Raman scattering (SERS) activity of these Janus NSs was studied with 1,4‐BDT as the model analyte. Finite‐difference time‐domain simulations for differently sized particles revealed the distribution of electromagnetic hot‐spots over the particles resulting in enhancement of the SERS signal in a size‐dependent manner. [ABSTRACT FROM AUTHOR]

In this study, cellulose filter paper (CFP) was used to create three-dimensional ZnO nanoflowers coated with three-layered plasmonic metals (Ag@Au@Ag) by using an in situ generated method. The substrate was created as a surface-enhanced Raman scattering (SERS) paper chip with dual functions for quick enrichment and ultrasensitive antibiotic detection. It was possible to detect amoxicillin, ciprofloxacin, and tetracycline quantitatively with good linear responses at low detection limits of 1, 10, and 10 nM, respectively, thanks to the characteristics of three-dimensional nanostructures, the charge transfer effect of ZnO–plasmonic metal, and electromagnetic coupling of Ag@Au@Ag. Even with a paper chip and a mobile phone–Raman spectrometer integrated system, it was possible to identify human urine antibiotics at ppb levels with high accuracy. Meanwhile, 10 min detection of the antibiotics was accomplished by merely soaking them in their analyte solutions due to CFP wicking. With the help of PCA-LDA analysis, the multiplexed SERS spectral data of the three antibiotics could be successfully separated. Additionally, the paper chip's exceptional mechanical endurance even against 30-fold and strong ultrasonication was made possible by the in situ growing method. The bifunctional, affordable, and long-lasting SERS paper chip has a lot of potential for on-site and point-of-care drug detection. [ABSTRACT FROM AUTHOR]

Ferroptosis is a non-apoptotic cell death regulated by iron-dependent lipid peroxidation. Glutathione (GSH), a key antioxidant against oxidative damage, is involved in one of the most important metabolic pathways of ferroptosis. Herein, an excellent plasmonic nanoprobe was developed for highly sensitive, in situ, dynamic real-time monitoring of intracellular GSH levels during ferroptosis. A nanoprobe was prepared by functionalizing gold nanoparticles (AuNPs) with the probe molecule crystal violet (CV). The fluctuation in the SERS signal intensity of CV via the competitive displacement reaction can be used to detect GSH. The advantages of the plasmonic nanoprobe including low-cost production techniques, outstanding stability and biocompatibility, high specificity and sensitivity towards GSH with a detection limit of 0.05 μM. It enables real-time dynamic monitoring of GSH levels in living cells during erastin-induced ferroptosis. This approach is expected to provide important theoretical support for elucidating the GSH-related ferroptosis metabolic mechanism and advancing our understanding of ferroptosis-based cancer therapy. [ABSTRACT FROM AUTHOR]

Raman spectroscopy exhibits potential as a tool for identifying the chemical composition of substances and has witnessed a growing application in urological oncology. This study undertook a bibliometric analysis to chart the present state and future prospects of Raman spectroscopy applications in urological tumors. The present study retrieved literature on the utilization of Raman spectroscopy in urological oncology from the Science Citation Index Expanded of Web of Science Core Collection, spanning from its inception to June 2023. Data from included studies were analyzed using CiteSpace, Python, and Excel. Our study examined 897 articles from 65 countries and identified a significant exponential growth in annual publications. The USA and China were prominent contributors to this field, with high publication rates and funding agencies. Shanghai Jiao Tong University emerged as the most influential institution. The journals Analytical Chemistry and Analyst were found to be the most productive. Our keyword analysis revealed an intense interest for "gold nanoparticle" and "pathology," with the most recent bursts occurring for "surface-enhanced Raman scattering (SERS)," "biomarkers," and "prostate specific antigen." As a detection tool, Raman spectroscopy holds the potential to assist in the identification, management, and prognostication of urological tumors. Notably, adjuvant diagnosis and prognosis evaluation based on SERS of tumor markers is a hot research topic. These findings offer valuable insights into the current state of Raman spectroscopy research in urological oncology, which could inform future studies and clinical practice. [ABSTRACT FROM AUTHOR]

Plasmonic nanostructure biosensors based on metal are a powerful tool in the biosensing field. Surface plasmon resonance (SPR) can be classified into localized surface plasmon resonance (LSPR) and propagating surface plasmon polariton (PSPP), based on the transmission mode. Initially, the physical principles of LSPR and PSPP are elaborated. In what follows, the recent development of the biosensors related to SPR principle is summarized. For clarity, they are categorized into three groups according to the sensing principle: (i) inherent resonance-based biosensors, which are sensitive to the refractive index changes of the surroundings; (ii) plasmon nanoruler biosensors in which the distances of the nanostructure can be changed by biomolecules at the nanoscale; and (iii) surface-enhanced Raman scattering biosensors in which the nanostructure serves as an amplifier for Raman scattering signals. Moreover, the advanced application of single-molecule detection is discussed in terms of metal nanoparticle and nanopore structures. The review concludes by providing perspectives on the future development of plasmonic nanostructure biosensors. [ABSTRACT FROM AUTHOR]

A variety of innovative point-of-care (POC) solutions using Raman systems have been explored. However, the vast effort is in assay development, while studies of the characteristics required for Raman spectrometers to function in POC applications are lacking. In this study, we tested and compared the performance of eight commercial Raman spectrometers ranging in size from benchtop Raman microscopes to portable and handheld Raman spectrometers using paper fluidic cartridges, including their ability to detect cardiac troponin I and heart fatty acid binding protein, both of which are well-established biomarkers for evaluating cardiovascular health. Each spectrometer was evaluated in terms of excitation wavelength, laser characteristics, and ease of use to investigate POC utility. We found that the Raman spectrometers equipped with 780 and 785 nm laser sources exhibited a reduced background signal and provided higher sensitivity compared to those with 633 and 638 nm laser sources. Furthermore, the spectrometer equipped with the single acquisition line readout functionality showed improved performance when compared to the point scan spectrometers and allowed measurements to be made faster and easier. The portable and handheld spectrometers also showed similar detection sensitivity to the gold standard instrument. Lastly, we reduced the laser power for the spectrometer with single acquisition line readout capability to explore the system performance at a laser power that change the classification from a Class 3B laser device to a Class 3R device and found that it showed comparable performance. Overall, these findings show that portable Raman spectrometers have the potential to be used in POC settings with accuracy comparable to laboratory-grade instruments, are relatively low-cost, provide fast signal readout, are easy to use, and can facilitate access for underserved communities. Graphical Abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

An easy and low-cost way to fabricate monometallic Au nanoislands for plasmonic enhanced spectroscopy is presented. The method is based on direct thermal evaporation of Au on glass substrates to form nanoislands, with thicknesses between 2 and 15 nm, which are subsequently covered by a thin layer of silicon dioxide. We have used HR-SEM and AFM to characterize the nanoislands, and their optical transmission reveals strong plasmon resonances in the visible. The plasmonic performance of the fabricated substrates has been tested in fluorescence and Raman scattering measurements of two probe materials. Enhancement factors up to 1.8 and 9×104 are reported for confocal fluorescence and Raman microscopies, respectively, which are comparable to others obtained by more elaborated fabrication procedures. [ABSTRACT FROM AUTHOR]

[Display omitted] Surface topography has become a powerful tool to control cell behaviors, however, it's still difficult to monitor cellular microenvironment changes during topography-induced cell responses. Here, a dual-functional platform integrating cell alignment with extracellular pH (pHe) measurement is proposed. The platform is fabricated by assembling gold nanorods (AuNRs) into micro pattern via wettability difference interface method, which provides topographical cues and surface-enhanced Raman scattering (SERS) effect for cell alignment and biochemical detection respectively. Results demonstrate that contact guidance and cell morphology changes are achieved by the AuNRs micro pattern, and pHe are also obtained by the changes of SERS spectra during cell alignment, where the pHe near cytoplasm is lower than nucleus, revealing the heterogeneity of extracellular microenvironment. Moreover, a correlation between lower extracellular pH and higher cell migration ability is revealed, and AuNRs micro pattern can differentiate cells with different migration ability, which may be an inheritable character during cell division. Furthermore, mesenchymal stem cells response dramatically to AuNRs micro pattern, showing different morphology and increased pHe level, offering the potential of impacting stem cell differentiation. This approach provides a new idea for the research of cell regulation and response mechanism. [ABSTRACT FROM AUTHOR]

The AuAgNB@SiO 2 -AuNP nanoassemblies with core-shell-satellite structure are fabricated based on anisotropic nanoboxes. The SERS activity of the nanoassemblies is multiply enhanced by strong plasmon coupling between AuAgNB and AuNP satellites, chemical enhancement from the AuAg-SiO 2 -Au heterogeneous interface, and tip "hot spots" of AuAgNB. The probe prepared by the nanoassemblies demonstrates satisfactory sensitivity and accuracy in the detection of stroke marker S100B. [Display omitted] Herein, A novel gold-silver alloy nanobox (AuAgNB)@SiO 2 -gold nanosphere (AuNP) nanoassembly based on core–shell-satellite structure is fabricated and applied to the surface-enhanced Raman scattering (SERS) detection of S100 calcium-binding protein B protein (S100B). It contains an anisotropic hollow porous AuAgNB core with rough surface, an ultrathin silica interlayer labeled with reporter molecules, and AuNP satellites. The nanoassemblies were systematically optimized by tuning the reporter molecules concentration, silica layer thickness, AuAgNB size, and the size and number of AuNP satellite size. Remarkably, AuNP satellites are adjacent to AuAgNB@SiO 2 , developing AuAg-SiO 2 -Au heterogeneous interface. With the strong plasmon coupling between AuAgNB and AuNP satellites, chemical enhancement from heterogeneous interface, and the tip "hot spots" of AuAgNB, the SERS activity of the nanoassemblies was multiply enhanced. Additionally, the stability of nanostructure and Raman signal was significantly improved by the silica interlayer and AuNP satellites. Eventually, the nanoassemblies were applied for S100B detection. It demonstrated satisfactory sensitivity and reproducibility with a wide detection range of 10 fg/mL-10 ng/mL and a limit of detection (LOD) of 1.7 fg/mL. This work based on the AuAgNB@SiO 2 -AuNP nanoassemblies with multiple SERS enhancements and favorable stability demonstrates the promising application in stroke diagnosis. [ABSTRACT FROM AUTHOR]

Bloodstream infections are a growing public health concern due to emerging pathogens and increasing antimicrobial resistance. Rapid antibiotic susceptibility testing (AST) is urgently needed for timely and optimized choice of antibiotics, but current methods require days to obtain results. Here, we present a general AST protocol based on surface-enhanced Raman scattering (SERS-AST) for bacteremia caused by eight clinically relevant Gram-positive and Gram-negative pathogens treated with seven commonly administered antibiotics. Our results show that the SERS-AST protocol achieves a high level of agreement (96% for Gram-positive and 97% for Gram-negative bacteria) with the widely deployed VITEK 2 diagnostic system. The protocol requires only five hours to complete per blood-culture sample, making it a rapid and effective alternative to conventional methods. Our findings provide a solid foundation for the SERS-AST protocol as a promising approach to optimize the choice of antibiotics for specific bacteremia patients. This novel protocol has the potential to improve patient outcomes and reduce the spread of antibiotic resistance. [ABSTRACT FROM AUTHOR]

In the macroscopic world, we can obtain some important information through the vibration of objects, that is, listening to the sound. Likewise, we can also get some information of the nanoparticles that we want to know by the means of "listening" in the microscopic world. In this review, we will introduce two sensing methods (cavity optomechanical sensing and surface-enhanced Raman scattering sensing) which can be used to detect the nanoparticles. The cavity optomechanical systems are mainly used to detect sub-gigahertz nanoparticle or cavity vibrations, while surface-enhanced Raman scattering is a well-known technique to detect molecular vibrations whose frequency generally exceeds terahertz. Therefore, the vibrational information of nanoparticles from low-frequency to high-frequency could be obtained by these two methods. The size of the viruses is at the nanoscale and we can regard it as a kind of nanoparticles. Rapid and ultrasensitive detection of the viruses is the key strategies to break the spread of the viruses in the community. Cavity optomechanical sensing enables rapid, ultrasensitive detection of nanoparticles through the interaction of light and mechanical oscillators and surface-enhanced Raman scattering is an attractive qualitatively analytical technique for chemical sensing and biomedical applications, which has been used to detect the SARS-CoV-2 infected. Hence, investigation in these two fields is of vital importance in preventing the spread of the virus from affecting human's life and health. [ABSTRACT FROM AUTHOR]

Semiconductors demonstrate great potentials as chemical mechanism‐based surface‐enhanced Raman scattering (SERS) substrates in determination of biological species in complex living systems with high selectivity. However, low sensitivity is the bottleneck for their practical applications, compared with that of noble metal‐based Raman enhancement ascribed to electromagnetic mechanism. Herein, a novel Cu2O nanoarray with free carrier density of 1.78×1021 cm−3 comparable to that of noble metals was self‐assembled, creating a record in enhancement factor (EF) of 3.19×1010 among semiconductor substrates. The significant EF was mainly attributed to plasmon‐induced hot electron transfer (PIHET) in semiconductor which was never reported before. This Cu2O nanoarray was subsequently developed as a highly sensitive and selective SERS chip for non‐enzyme and amplification‐free SARS‐CoV‐2 RNA quantification with a detection limit down to 60 copies/mL within 5 min. This unique Cu2O nanoarray demonstrated the significant Raman enhancement through PIHET process, enabling rapid and sensitive point‐of‐care testing of emerging virus variants. [ABSTRACT FROM AUTHOR]

The drive to achieve ultrasensitive target detection with exceptional efficiency and accuracy requires the advancement of immunoassays. Optical immunoassays have demonstrated significant potential in clinical diagnosis, food safety, environmental protection, and other fields. Through the innovative and feasible combination of enzyme catalysis and optical immunoassays, notable progress has been made in enhancing analytical performances. Among the kinds of reporter enzymes, alkaline phosphatase (ALP) stands out due to its high catalytic activity, elevated turnover number, and broad substrate specificity, rendering it an excellent candidate for the development of various immunoassays. This review provides a systematic evaluation of the advancements in optical immunoassays by employing ALP as the signal label, encompassing fluorescence, colorimetry, chemiluminescence, and surface-enhanced Raman scattering. Particular emphasis is placed on the fundamental signal amplification strategies employed in ALP-linked immunoassays. Furthermore, this work briefly discusses the proposed solutions and challenges that need to be addressed to further enhance the performances of ALP-linked immunoassays. [ABSTRACT FROM AUTHOR]

Metal@dielectric core@shell nanoparticles (NPs) have attracted significant attention due to their multifunctional properties and vast applications in different fields of catalysis, photonics, sensing, nanomedicine, etc. However, there is a dearth of reports about the synthesis of controlled aggregation of gold cores without using any cross-linkers and the effects of the presence of multiple metallic cores in one shell, particularly for surface-enhanced Raman scattering (SERS) and electrochemical sensing. Nanoaggregates, N ≥ 2 (where N is the number of nanoparticles in aggregation), can effectively be used for fine-tuning plasmon wavelength, whereas collective encapsulation of number-selected nanoaggregates by functionalized SiO2 generates multiple capacitors which in turn enhance the field at the nanojunctions and nanogaps for improved SERS and catalytic sensing activity. We successfully prepared controlled AuNP aggregation, passivated them by the SiO2 outer layer to make them suitable for preservation in the solid state and functionalization by 3-aminopropyl trimethoxysilane (APTMS), and separated the nanoaggregates based on the aggregation size (individual nanoaggregates having 2 to 100 nanoparticles in each). The thickness of the silica shell was engineered in such a way that shell thickness does not make any hindrance in optical measurements, and the effect of multiple nanoparticle cores on the surface plasmon resonance and SERS can be understood properly and also allows external molecules to reach active gold nanoparticle surface for electrocatalytic activity. Functionalization allows individual encapsulations to further form multi-junction capacitors by bridging them through a positively charged dye molecule, here Rhodamine 6G (Rh6G). By using these multiple gold nanoparticle cores within a single silica shell (multi-Au@SiO2 core@shell nanoparticles) with improved SERS and electrocatalytic activity, we have also successfully ultrasensed (0.003 μA·μM–1·cm–2) glucose in a nonenzymatic electrochemical pathway. [ABSTRACT FROM AUTHOR]

Sample-preparation methods have been developed and adapted for using gold nanoparticles in qualitative analysis of paint layer compositions with surface-enhanced Raman scattering (SERS). Use of plasmonic nanoparticles for SERS analysis of art materials in actual paintings could significantly reduce the luminescent background caused by the presence of organic binders in the paint layer and led to multiple amplification of the chromophore Raman-line intensities and an increase in the signal-to-noise ratio. The techniques were successfully tested on paint layers of 12 easel paintings of the XVI–XIX centuries in close cooperation with museums of the Republic of Belarus and could be systematically used in art history expertise to identify the composition of paints and attribution of cultural heritage objects. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride (PVDF), polyamide (Nylon) and anodic aluminum oxide (AAO) filter membranes were coated with in-situ synthesized silver nanoparticle/reduced graphene oxide (AgNP/rGO) nanocomposite by vacuum filtration, and surface-enhanced Raman scattering (SERS) performance of the prepared substrates was investigated using Rhodamine 6G (R6G) as a probe molecule. Analyte solutions were applied by drop casting and penetrated into the flexible PVDF and Nylon-based substrates within minutes, enabling very fast SERS measurements; however, this step took up to 2 hrs in the rigid AAO-based substrate. Scanning electron microscopy and Energy-dispersive X-ray spectroscopy mapping results showed that filter membrane surfaces were completely covered with AgNP/rGO nanocomposite at which AgNPs were uniformly distributed on rGO flakes; however, some large, partially reduced or unreduced GO flakes decorated with AgNP agglomerates (AgNP/GO) were also observed. Higher SERS signals were generally obtained from these AgNP/GO flakes compared to the AgNP/rGO coated regions, since they contain higher amount of oxygen-rich functional groups which enabled a higher chemical and electromagnetic enhancement in SERS signals. All the substrates could detect 10−7 M R6G even after being stored in a vacuum desiccator for 3 months, indicating that AgNP/rGO coated filter membranes are promising as stable SERS substrates thanks to their long shelf life. [ABSTRACT FROM AUTHOR]

For a very long period, tin was considered one of the most important metals for humans due to its easy access in nature and abundance of sources. In the past, tin was mainly used to make various utensils and weapons. Today, nanostructured tin and especially its oxide materials have been found to possess many characteristic physical and chemical properties that allow their use as functional materials in various fields such as energy storage, photocatalytic process, gas sensors, and solar cells. This review discusses current methods for the synthesis of Sn/SnO2 composite materials in form of powder or thin film, as well as the application of the most advanced characterization tools based on large-scale synchrotron radiation facilities to study their chemical composition and electronic features. In addition, the applications of Sn/SnO2 composites in various fields are presented in detail. [ABSTRACT FROM AUTHOR]

With the recent global outbreaks of infectious diseases such as coronavirus disease 2019, developing a detection system capable of quickly and accurately diagnosing diseases on‐site has become a pressing need. The ability to diagnose patients in the field is crucial for the prompt isolation and treatment of infected individuals and the prevention of the spread of the disease. Our research group has recently developed a surface‐enhanced Raman scattering optofluidic system that enables rapid and accurate point‐of‐care diagnostics. This account will introduce the principle and configuration of the fluidic devices, such as lateral flow assay strips or microfluidic channels, and the portable Raman spectrometer. We will also highlight the challenges that must be addressed for using this system in clinical settings. Rapid and accurate diagnosis is critical for effective disease management and control, and developing this system can significantly improve our ability to respond to outbreaks of infectious diseases. [ABSTRACT FROM AUTHOR]

Optical imaging and spectroscopic modalities are of broad interest for in-vivo molecular imaging, fluorescence guided cancer surgery, minimally invasive diagnostic procedures, and wearable devices. However, considerable debate still exists as to how deeply visible and near-infrared (NIR) light could penetrate normal and diseased tissues under clinically relevant conditions. Here we report the use of surface-enhanced Raman scattering (SERS) nanotags embedded in ex-vivo animal tissues for direct and quantitative measurements of light attenuation and spectroscopic detection depth at both the NIR-I and NIR-II spectral windows. SERS nanotags are well suited for this purpose because of their sharp spectral features that can be accurately differentiated from fluorescence and background emission. For the first time, the spectroscopic detection depth is quantitatively defined and measured as the maximal thickness of tissues through which the embedded SERS nanotags are still detected at a signal-to-noise ratio (SNR) of three (99.7% confidence level). Based on data from six types of fresh ex-vivo tissues (brain, kidney, liver, muscle, fat, and skin), we find that the maximum detection depth values range from 1—3 mm in the NIR-I window, to 3—6 mm in the NIR-II window. The depth values are largely determined by two factors – the intrinsic optical properties of the tissue, and the overall SNRs of the system without the tissue (system SNR, a result of nanotag brightness, instrument efficiency, and data acquisition parameters). In particular, there is an approximately linear-logarithmic relationship between the system SNR and maximum detection depth. Thus, the detection of hidden or occult lesions can be improved by three strategies – reducing tissue attenuation, minimizing background noise, and maximizing the system's performance as judged by SNR. Highlights: The spectroscopic detection depth is quantitatively defined and measured as the maximal thickness of tissues through which the embedded Raman nanotags are detected at a signal-to-noise ratio of three. The intrinsic optical properties of the tissue and the system signal-to-noise ratio are the two deciding factors of signal penetration in bio-tissues. A generalized linear-logarithmic relationship is revealed between the system SNR and spectroscopic detection depth for each tissue. [ABSTRACT FROM AUTHOR]

This paper introduces an approach that enables highly adjustable surface adsorption of single plasmonic nanostructures using polar surface arrays. The plasmonic nanostructures are made from DNA origami and functionalized with gold nanoparticles for surface-enhanced spectroscopic techniques. To ensure that the contribution of individual nanostructures to the measured signal can be detected without any interference from the surrounding structures, we aimed to control the distance and set a minimum gap between the nanostructures on the substrate surface. We describe the fabrication process of the polar surface array based on electron beam lithography, followed by functionalization. Our results indicate that the concentration of DNA origami structures and the duration of the incubation primarily affect the number of adsorbed nanostructures. Density functional theory simulation explains the selective adsorption of plasmonic nanostructures due to the substrate surface properties. The spatial arrangement of nanostructures allows for the reliable identification of the Raman signal's location, while a falsified identification resulting from agglomeration is prevented. [ABSTRACT FROM AUTHOR]

π‐Conjugated organic semiconductors are promising materials for surface‐enhanced Raman scattering (SERS)‐active substrates based on the tunability of electronic structures and molecular orbitals. Herein, we investigate the effect of the temperature‐mediated resonance‐structure transitions of poly(3,4‐ethylenedioxythiophene) (PEDOT) in poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT : PSS) films on the interactions between substrate and probe molecules, thereby affecting the SERS activity. Absorption spectroscopy and density functional theory calculations show that this effect occurs mainly due to delocalization of the electron distribution in molecular orbitals, effectively promoting the charge transfer between the semiconductor and probe molecules. In this work, we investigate for the first time the effect of electron delocalization in molecular orbitals on SERS activity, which will provide new design ideas for the development of highly sensitive SERS substrates. [ABSTRACT FROM AUTHOR]

Non‐invasive detection and precise localization of deep lesions have attracted significant attention for both fundamental and clinical studies. Optical modality techniques are promising with high sensitivity and molecular specificity, but are limited by shallow tissue penetration and the failure to accurately determine lesion depth. Here the authors report in vivo ratiometric surface‐enhanced transmission Raman spectroscopy (SETRS) for non‐invasive localization and perioperative surgery navigation of deep sentinel lymph nodes in live rats. The SETRS system uses ultrabright surface‐enhanced Raman spectroscopy (SERS) nanoparticles with a low detection limit of 10 pM and a home‐built photosafe transmission Raman spectroscopy setup. The ratiometric SETRS strategy is proposed based on the ratio of multiple Raman spectral peaks for obtaining lesion depth. Via this strategy, the depth of the phantom lesions in ex vivo rat tissues is precisely determined with a mean‐absolute‐percentage‐error of 11.8%, and the accurate localization of a 6‐mm‐deep rat popliteal lymph node is achieved. The feasibility of ratiometric SETRS allows the successful perioperative navigation of in vivo lymph node biopsy surgery in live rats under clinically safe laser irradiance. This study represents a significant step toward the clinical translation of TRS techniques, providing new insights for the design and implementation of in vivo SERS applications. [ABSTRACT FROM AUTHOR]

Novel low‐cost materials to uptake and detect vestigial amounts of pesticides are highly desirable for water quality monitoring. Herein, are demonstrated, for the first time, surface‐enhanced Raman scattering (SERS) sensors enabled via additively manufactured lattices coated with plasmonic nanoparticles (NPs) for detecting pesticides in real water samples. The architected lattices comprising polypropylene (PP) and multiwall carbon nanotubes (MWCNTs) are realized via fused filament fabrication (FFF). In the first stage, the SERS performance of the PP/MWCNT filaments coated with distinct metallic NPs (Ag NPs and Au NPs) is evaluated using methylene blue (MB) as molecular probe. Thereafter, distinctly architected hybrid SERS sensors with periodic porous and fully dense geometries are investigated as adsorbents to uptake MB from aqueous solutions and subsequent detection using SERS. The spatial distribution of MB and Ag NPs on the FFF‐printed lattices is accomplished by SERS imaging. The best hybrid composite is used as SERS probing system to detect low amounts of pesticides (thiram and paraquat) and offers a detection limit of 100 nm for both pesticides. As a proof‐of‐concept, FFF‐enabled test strips are used to detect in loco paraquat molecules spiked on real water samples (Estuary Aveiro water and tap water) using a portable Raman spectrometer. [ABSTRACT FROM AUTHOR]

A novel stimulus-responsive surface-enhanced Raman scattering (SERS) nanoprobe has been developed for sensitive glutathione (GSH) detection based on manganese dioxide (MnO2) core and silver/gold nanoparticles (Ag/Au NPs). The MnO2 core is not only capable to act as a scaffold to amplify the SERS signal via producing "hot spots", but also can be degraded in the presence of the target and thus greatly enhance the nanoprobe sensitivity for sensing of GSH. This approach enables a wide linear range from 1 to 100 µM with a 2.95 µM (3σ/m) detection limit. Moreover, the developed SERS nanoprobe represents great possibility in both sensitive detection of intracellular GSH and even can monitor the change of intracellular GSH level when the stimulant occurs. This sensing system not merely offers a novel strategy for sensitive sensing of GSH, but also provides a new avenue for other biomolecules detection. [ABSTRACT FROM AUTHOR]

• Aggregation-induced emission and aggregation-related surface-enhanced Raman scattering technologies in cancer detection are reviewed. • Two strategies of target-driven aggregation and aggregated nanoprobes enabling biomarker detection are discussed. • Outlook and challenges of aggregation approaches are summarized. The implementation of early cancer detection benefits the treatment outcomes with remarkably improved survival rate through the detection of rare circulating biomarkers in body fluids. Spectroscopic technologies play a crucial role in sensitive biomarker measurements by outputting extremely strong signals. In particular, the aggregation enhanced fluorescence and Raman technologies feature the detection of targets down to single-molecule level, thereby demonstrating the great promise of early cancer detection. In this review, we focus on the aggregation-induced emission (AIE) and aggregation-related surface-enhanced Raman scattering (SERS) spectroscopic strategies for detecting cancer biomarkers. We discuss the AIE and SERS based biomarker detection using target-driven aggregation as well as the aggregated nanoprobes. Furthermore, we deliberate on the progress of developing AIE and SERS integrated platforms. Ultimately, we put forth the potential challenges and perspectives on the way to use these two spectroscopic technologies in clinical settings. It is expected this review can inspire the design of AIE and SERS integrated platform for highly sensitive and accurate cancer detection. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS), a powerful spectroscopic technique owing to its abundant vibrational fingerprints, has been widely employed for the assay of analytes. It is generally considered that one of the critical factors determining the SERS performance is the property of the substrate materials. Apart from noble metal substrates, non-noble metal nanostructured materials, as emerging new substrates, have been extensively studied for SERS research by virtue of their superior biocompatibility, good chemical stability, outstanding selectivity, and unique physicochemical properties such as adjustable band structure and carrier concentration. Herein, in this review, we summarized the research on the analytical application of non-noble metal SERS substrates from three aspects. Firstly, we started with an introduction to the possible enhancement mechanism of non-noble metal substrates. Then, as a guideline for substrates design, several main types of materials, including carbon nanomaterials, transition metal dichalcogenides (TMDs), metal oxides, metal-organic frameworks (MOFs), transition metal carbides and nitrides (MXenes), and conjugated polymers were discussed. Finally, we especially emphasized their analytical application, such as the detection of pollutants and biomarkers. Moreover, the challenges and attractive research prospects of non-noble metal SERS substrates in practical application were proposed. This work may arouse more awareness of the practical application of the non-noble metal material-based SERS substrates, especially for bioanalysis. [ABSTRACT FROM AUTHOR]

Recent advances in molecular technologies have provided various assay strategies for monitoring biomarkers, such as miRNAs for early detection of various diseases and cancers. However, there is still an urgent unmet need to develop practical and accurate miRNA analytical tools that could facilitate the incorporation of miRNA biomarkers into clinical practice and management. In this study, we demonstrate the feasibility of using a cascade amplification method, referred to as the "Cascade Amplification by Recycling Trigger Probe" (CARTP) strategy, to improve the detection sensitivity of the inverse Molecular Sentinel (iMS) nanobiosensor. The iMS nanobiosensor developed in our laboratory is a unique homogeneous multiplex bioassay technique based on surface-enhanced Raman scattering (SERS) detection, and was used to successfully detect miRNAs from clinical samples. The CARTP strategy based on the toehold-mediated strand displacement reaction is triggered by a linear DNA strand, called the "Recycling Trigger Probe" (RTP) strand, to amplify the iMS SERS signal. Herein, by using the CARTP strategy, we show a significantly improved detection sensitivity with the limit of detection (LOD) of 45 fM, which is 100-fold more sensitive than the non-amplified iMS assay used in our previous report. We envision that the further development and optimization of this strategy ultimately will allow multiplexed detection of miRNA biomarkers with ultra-high sensitivity for clinical translation and application. [ABSTRACT FROM AUTHOR]

Rapid antimicrobial susceptibility testing (AST) is an integral tool to mitigate the unnecessary use of powerful and broad-spectrum antibiotics that leads to the proliferation of multi-drug-resistant bacteria. Using a sensor platform composed of surface-enhanced Raman scattering (SERS) sensors with control of nanogap chemistry and machine learning algorithms for analysis of complex spectral data, bacteria metabolic profiles post antibiotic exposure are correlated with susceptibility. Deep neural network models are able to discriminate the responses of Escherichia coli and Pseudomonas aeruginosa to antibiotics from untreated cells in SERS data in 10 min after antibiotic exposure with greater than 99% accuracy. Deep learning analysis is also able to differentiate responses from untreated cells with antibiotic dosages up to 10-fold lower than the minimum inhibitory concentration observed in conventional growth assays. In addition, analysis of SERS data using a generative model, a variational autoencoder, identifies spectral features in the P. aeruginosa lysate data associated with antibiotic efficacy. From this insight, a combinatorial dataset of metabolites is selected to extend the latent space of the variational autoencoder. This culture-free dataset dramatically improves classification accuracy to select effective antibiotic treatment in 30 min. Unsupervised Bayesian Gaussian mixture analysis achieves 99.3% accuracy in discriminating between susceptible versus resistant to antibiotic cultures in SERS using the extended latent space. Discriminative and generative models rapidly provide high classification accuracy with small sets of labeled data, which enormously reduces the amount of time needed to validate phenotypic AST with conventional growth assays. Thus, this work outlines a promising approach toward practical rapid AST.

Lyotropic liquid crystals (LLCs) produced by the self-assembly of surfactant in water represent an important class of highly ordered soft materials that have a wide range of applications. This study investigates the LLCs formed by a zwitterionic surfactant (tetradecyldimethylaminoxide, C14DMAO) in water. The organization of C14DMAO within the LLCs was determined based on a detailed analysis of small-angle X-ray scattering measurements and polarized microscopy observations of a typical sample. Additional to the singe-phase region, which has a hexagonal organization, several two-phase regions were observed, exhibiting the coexistence of hexagonal/cubic, cubic/lamellar, and hexagonal/lamellar phases. The phase behavior showed an obvious dependence on temperature, with more pronounced two-phase regions at lower temperatures. Using the LLCs as a matrix, Au nanospheres, nanoellipsoids, and nanorods were prepared without requiring additional reducing reagents. These three- and one-dimensional Au nanomaterials could be converted to two-dimensional plates via the introduction of a small amount of cationic surfactant to the LLCs, such as cetyltrimethylammonium bromide (CTAB) and 1-hexadecyl-3-methylimidazolium bromide ([C16MIm]B), which showed pronounced surface-enhanced Raman scattering activity towards solid rhodamine. The LLCs loaded with CTAB (or [C16MIm]B) and HAuCl4 exhibited slightly different structures and mechanical strength from the original LLCs, thereby forming a new class of highly crowded colloidal materials.

Abstract Drug checking is increasingly being explored outside of festivals and events to be an ongoing service within communities, frequently integrated within responses to illicit drug overdose. The choice of instrumentation is a common question, and the demands on these chemical analytical instruments can be challenging as illicit substances may be more complex and include highly potent ingredients at trace levels. The answer remains nuanced as the instruments themselves are not directly comparable nor are the local demands on the service, meaning implementation factors heavily influence the assessment and effectiveness of instruments. In this perspective, we provide a technical but accessible introduction to the background of a few common drug checking methods aimed at current and potential drug checking service providers. We discuss the following tools that have been used as part of the Vancouver Island Drug Checking Project in Victoria, Canada: immunoassay test strips, attenuated total reflection IR-absorption spectroscopy, Raman spectroscopy from powder samples, surface-enhanced Raman scattering in a solution of colloidal gold nanoparticles, and gas chromatography–mass spectrometry. Using four different drug mixtures received and tested at the service, we illustrate the strengths, limitations, and capabilities of such instruments, and expose the scientific theory to give further insight into their analytical results. Each case study provides a walk-through-style analysis for a practical comparison between data from several different instruments acquired on the same sample. Ideally, a single instrument would be able to achieve all of the objectives of drug checking. However, there is no clear instrument that ticks every box; low cost, portable, rapid, easy-to-use and provides highly sensitive identification and accurate quantification. Multi-instrument approaches to drug checking may be required to effectively respond to increasingly complex and highly potent substances demanding trace level detection and the potential for quantification.