In vivo surface-enhanced Raman scattering nanosensor for the real-time monitoring of multiple stress signalling molecules in plants

Recent Advances in Fluorescent Probe for Detecting Biorelevant Analytes during Stress in Plants

Plants are constantly exposed to various stressors that can severely hinder their growth and threaten agricultural productivity. Recent advancements in plant imaging using fluorescent probes have opened new avenues for exploring the intricate processes involved in plant stress perception and signaling. This review represents the comprehensive effort to consolidate recent advances in fluorescent probe technologies, encompassing small-molecule probes, nanoprobes, and genetically encoded indicators, as revolutionary tools for deciphering stress-induced physiological dynamics. We present a comprehensive classification of fluorescent probes designed for detecting key biomolecules involved in plant stress responses, including reactive species, phytohormones, enzymes, and other signaling molecules. By critically evaluating their design principles, practical applications, and distinct advantages over conventional analytical methods, we aim to empower plant scientists in unraveling the spatiotemporal regulation of stress signaling networks. Finally, we propose strategic directions to overcome current technical bottlenecks and maximize the potential of fluorescence-based sensing in advancing sustainable agriculture.

In vitro diagnosis based on SERS-LFIA: research hotspots, increase sensitivities, combined detection, multimodal detection and related patents

In recent years, the SERS-LFIA platform has gained significant traction in in vitro diagnostics. However, a comprehensive review of its advancements and applications is still lacking. This review first employing a bibliometric approach to analyze research trends. It then outlines strategies to enhance sensitivity, focusing on Raman reporter molecules, SERS tags, coupling methods, detection instruments. Additionally, the review explores the use of SERS-LFIA for diagnosing multiple disease biomarkers, highlighting its potential to improve diagnostic accuracy. The review also synthesizes the application of multimodal SERS-LFIA technology, integrating signals such as colorimetric, magnetic, photothermal, fluorescent, and catalytic modalities. This approach enhances detection versatility and broadens diagnostic capabilities. Furthermore, it examines the current patent landscape, providing insights into the technology's commercial and technological progress. Lastly, the review discusses ongoing challenges, including stability and reproducibility and quantitative detection, while suggesting directions for future research. In summary, this review consolidates the latest advancements in SERS-LFIA technology for in vitro diagnostics over the past decade. Anticipated to furnish a robust scientific foundation and theoretical underpinning for the advancement of SERS-LFIA technology, this endeavor aims to enhance its efficacy in clinical diagnostics.

In vivo surface-enhanced Raman scattering techniques: nanoprobes, instrumentation, and applications

Surface-enhanced Raman scattering (SERS) has emerged as a powerful tool in various biomedical applications, including in vivo imaging, diagnostics, and therapy, largely due to the development of near-infrared (NIR) active SERS substrates. This review provides a comprehensive overview of SERS-based applications in vivo, focusing on key aspects such as the design considerations for SERS nanoprobes and advancements in instrumentation. Topics covered include the development of NIR SERS substrates, Raman label compounds (RLCs), protective coatings, and the conjugation of bioligands for targeted imaging and therapy. The review also discusses microscope-based configurations such as scanning, widefield imaging, and fiber-optic setups. Recent advances in using SERS nanoprobes for in vivo sensing, diagnostics, biomolecule screening, multiplex imaging, intraoperative guidance, and multifunctional cancer therapy are highlighted. The review concludes by addressing challenges in the clinical translation of SERS nanoprobes and outlines future directions, emphasizing opportunities for advancing biomedical research and clinical applications.

Flexible substrate-based mass spectrometry platform for in situ non-destructive molecular imaging of living plants

Monitoring and localizing molecules on living plants is critical for understanding their growth, development and disease. However, current techniques for molecular imaging of living plants often lack spatial information or require tedious pre-labelling. Here, we proposed a novel molecular imaging platform that combines sliver nanowire-doped Ti3C2 MXene (Ag NWs@MXene) flexible film substrate with laser desorption/ionization mass spectrometry imaging (AMF-LDI-MSI) to study the spatial distribution of biomolecules on the surface of living plants. This platform overcomes the MSI challenges posed by difficult-to-slice plant tissues (e.g., tough or water-rich roots and fragile flowers) and enables precisely transfer and visualize the molecule. Comparisons of the measurement results to those from matrix-assisted LDI-MSI (MALDI-MSI) technology demonstrate the accuracy and reliability of the platform. Biocompatibility evaluations indicated that the platform without observable adverse effects on the health of living plants. The distribution of growth and disease-associated signalling molecules, such as choline, organic acids and carbohydrates, can be in situ non-destructively detected on the surfaces of living plants, which is important for tracking the health of plants and their diseased areas. AMF-LDI-MSI platform can serve as a promising tool for label-free, in situ and non-destructive monitoring of functional biomolecules and plant growth from a spatial perspective.

Trends of Nanobiosensors in Modern Agriculture Systems

Sustainable agriculture and the provision of food for all become dependent on the availability of efficient diagnostic techniques for the prompt identification of plant diseases. Current scientific findings suggest that nanotechnology can positively affect the agrifood industry by reducing the adverse effects of agricultural practices on human health and the environment, increasing food security and productivity, and fostering social and economic justice. Nanomaterials' unique physical and chemical characteristics have made it possible to employ them as cutting-edge, effective diagnostic instruments for various plant infections and other significant disease biomarkers. By creating diagnostic instruments and methods, nanobiosensors significantly contribute to the revolution of farming. In real time, nanobiosensors can detect infections, metabolites, pesticides, nutrient levels, soil moisture, and temperature. This helps with precision farming techniques and maximises resource use. To better address agricultural concerns, we have included the most recent research on the concept, types, applications, commercial aspects, and future scope of nanobiosensors in this review.

Real-Time Monitoring of Volatile Organic Compound-Mediated Plant Intercommunication Using Surface-Enhanced Raman Scattering Nanosensor

Plants communicate through volatile organic compounds (VOCs), but real-time monitoring of VOCs for plant intercommunication is not practically possible yet. A nanobionic VOC sensor plant is created to study VOC-mediated plant intercommunication by incorporating surface-enhanced Raman scattering (SERS) nanosensors into a living plant. This sensor allows real-time monitoring of VOC with a sensitivity down to the parts per trillion level. A quantitative VOC diffusion model in plants is proposed to describe this extreme sensitivity. The sensor plant is paired with a customized portable Raman device, demonstrating its ability to detect multiple VOCs on-field. The sensor demonstrated that plants collect VOCs emitted from neighboring plants and hazardous volatile chemicals in the air at a certain distance. As a feasibility study, this nanobionic VOC sensor plant successfully monitored the early stages of fungal infection in strawberry fruits. This result suggests that interfacing nanosensors with plants offers an innovative approach to studying interplant communication and can be used as a compelling tool for monitoring VOC occurrence.

Trade-off strategies for driving the toxicity and metabolic remodeling of copper oxide nanoparticles and copper ions in Ipomoea aquatica

The ecological safety of copper oxide nanoparticles (CuO NPs) in the environment determines the advancement of nano-agriculture owing to breakthroughs in nanotechnology; however, the release of Cu2+ is an uncontrollable factor. Currently, the trade-off mechanisms of CuO NPs and Cu2+ dominating the potential hazards of plant-nano systems remain unclear. This study proposed the trade-off strategy for reconstructing physiological responses and metabolic profiles and deciphered the differential regulation of dominant CuO NPs and Cu2+ in plants. The results showed that 100 and 500 mg/kg CuO NPs promoted root fresh weight but reduced shoot fresh weight, while 1000 mg/kg Cu2+ demonstrated the strongest inhibition on both roots and shoots. The net photosynthetic perturbation in photosynthetic disorders is accompanied by superoxide anion and hydrogen peroxide accumulation, which are severe under 1000 mg/kg CuO NPs and Cu2+ stress. Metabolomics revealed that CuO NPs significantly altered coumaric acid and derivatives, for example, down-regulating coumaroyl hexoside (isomers of 690 and 691) by 40.79 %. Additionally, Cu2+ treatment severely interfered with the dominant metabolic response, activating plant hormone signal transduction and α-linolenic acid metabolism. The trade-off strategies of galactose metabolism, amino sugar and nucleotide sugar metabolism, pantothenate and coenzyme A (CoA) biosynthesis, and β-alanine metabolism as differential metabolism were confirmed by comparing the CuO NPs and Cu2+ exposure. Protein secondary structure analysis revealed specific regulation of protein conformation upon exposure to CuO NPs and Cu2+. These findings provide new insights into differential metabolism and environmental effects in plant-nano systems.

Mechanochemical activation of 2D MnPS3 for sub-attomolar sensing

Molecular detection is important in biosensing, food safety, and environmental surveillance. The high biocompatibility, superior mechanical stability, and low cost make plasmon-free surface-enhanced Raman scattering (SERS) a promising sensing technique, the ultrahigh sensitivity of which is urgently pursued for realistic applications. As a proof of concept, we report a mechanochemical strategy, which combines the wrinkling and chemical functionalization, to fabricate a plasmon-free SERS platform based on 2D MnPS3 with a sub-attomolar detection limit. In detail, the formation of wrinkles in 2D MnPS3 enables a SERS substrate of the material to detect trace methylene blue molecules. The mechanism is experimentally revealed that the wrinkled structures contribute to the improvement of light-matter coupling. On this basis, decorating a wrinkled MnPS3 which has absorbed methylene blue with histamine dihydrochloride further lowers the detection limit to 10-19 M. Because the amino groups in histamine dihydrochloride molecules are crosslinkers that create more pathways to promote charge transfer between these substances. This work provides a guidance for the design of SERS sensors with single-molecule-level sensitivity.

Phase-Engineered Transition Metal Dichalcogenides for Highly Efficient Surface-Enhanced Raman Scattering

Phase engineering of two-dimensional (2D) transition metal dichalcogenides (TMDs) is an attractive avenue to construct new surface-enhanced Raman scattering (SERS) substrates. Herein, 2D WS2 and MoS2 monolayers with high-purity distorted octahedral phase (1T') are prepared for highly sensitive SERS detection of analytes (e.g., rhodamine 6G, rhodamine B and crystal violet). 1T'-WS2 and 1T'-MoS2 monolayers show the detection limits of 8.28 × 10-12 and 8.57 × 10-11 M for rhodamine 6G, with the enhancement factors of 4.6 × 108 and 3.9 × 107, respectively, which are comparable to noble-metal substrates, outperforming semiconducting 2H-W(Mo)S2 monolayers and most of the reported non-noble-metal substrates. First-principles density functional theory calculations show that their Raman enhancement effect is mainly ascribed to highly efficient interfacial charge transfer between the 1T'-W(Mo)S2 monolayers and analytes. Our study reveals that 2D TMDs with semimetallic 1T' phase are promising as next-generation SERS substrates.

High Spatiotemporal Precision Mapping of Optical Nanosensor Array Using Machine Learning

Optical nanosensors, including single-walled carbon nanotubes (SWCNTs), provide real-time spatiotemporal reporting at the single-molecule level within a nanometer-scale area. However, their superior sensitivity also makes them susceptible to slight environmental influences such as reference analytes in media, external fluid flow, and mechanical modulations. Consequently, they often fail to achieve the optimal limit of detection (LOD) and frequently convey misinformation spatiotemporally. To address this challenge, we developed a single-pixel mapping technique for optical nanosensor arrays that operates with high spatiotemporal precision using machine learning. We systematically measured the spatial sensing images of various analyte concentrations below the LOD by using a near-infrared (nIR) fluorescent SWCNT nanosensor array. For dopamine (DA) as an example analyte, we extracted single-pixel level sensing features such as entropy, the Laplacian operator, and neighboring values under noise levels. We then trained the artificial intelligence (AI) model to accurately identify specific reaction pixels of the nanosensor array, even below the LOD region. Additionally, our method can distinguish subtle noise caused by fluid in the media or mechanical modulation of the array substrate. As a result, our approach significantly improved the detection sensitivity of the nanosensor array, achieving a 13-fold increase over the original LOD and halving the detection time of the reporter pixels, with F1 scores exceeding 0.9. This method not only lowers the LOD of optical nanosensors but also isolates sensor responses specific to the analyte, providing accurate spatiotemporal information to the user, even in noisy conditions. It can be universally applied to various optical nanosensor materials and analytes, maximizing the sensitivity and accuracy of the nanosensors used in diagnostics and analysis.

Electric Field-Induced Enhanced Raman Spectroscopy Sensor and Photocatalysis with Thermoelectric-Plasmonic Metal Nanocomposites

Electric field-induced surface-enhanced Raman scattering (E-SERS) substrates have been proven to further enhance the attained Raman intensity. Herein, integrated with plasmonic Ag nanoparticles (Ag NPs), the thermoelectric Bi2Te3 plate as an E-SERS substrate decreased the limit of detection by 2 orders of magnitude and increased the SERS signal by >20 times compared to those without electrical field induction. The thermoelectric potential produced by the Bi2Te3 plate could modulate the electron density and subsequently change the Fermi level of Ag. This increases the resonant electron transition probability using a broad range of molecules. The plasmon-activated catalytic reactions of the interconversion between p-nitrothiophenol and p,p'-dimercaptoazobenzene could be controlled through the E-SERS template. On the basis of the finite element method, explicit theoretical analysis indicated that the Ag NP-Bi2Te3-molecule charge transfer could improve our understanding of the SERS and photocatalytic mechanism.

Plasmonics nanorod biosensor for in situ intracellular detection of gene expression biomarkers in intact plant systems

The intracellular developmental processes in plants, particularly concerning lignin polymer formation and biomass production are regulated by microRNAs (miRNAs). MiRNAs including miR397b are important for developing efficient and cost-effective biofuels. However, traditional methods of monitoring miRNA expression, like PCR, are time-consuming, require sample extraction, and lack spatial and temporal resolution, especially in real-world conditions. We present a novel approach using plasmonics nanosensing to monitor miRNA activity within living plant cells without sample extraction. Plasmonic biosensors using surface-enhanced Raman scattering (SERS) detection offer high sensitivity and precise molecular information. We used the Inverse Molecular Sentinel (iMS) biosensor on unique silver-coated gold nanorods (AuNR@Ag) with a high-aspect ratio to penetrate plant cell walls for detecting miR397b within intact living plant cells. MiR397b overexpression has shown promise in reducing lignin content. Thus, monitoring miR397b is essential for cost-effective biofuel generation. This study demonstrates the infiltration of nanorod iMS biosensors and detection of non-native miRNA 397b within plant cells for the first time. The investigation successfully demonstrates the localization of nanorod iMS biosensors through TEM and XRF-based elemental mapping for miRNA detection within plant cells of Nicotiana benthamiana. The study integrates shifted-excitation Raman difference spectroscopy (SERDS) to decrease background interference and enhance target signal extraction. In vivo SERDS testing confirms the dynamic detection of miR397b in Arabidopsis thaliana leaves after infiltration with iMS nanorods and miR397b target. This proof-of-concept study is an important stepping stone towards spatially resolved, intracellular miRNA mapping to monitor biomarkers and biological pathways for developing efficient renewable biofuel sources.

Polymeric Nanocarriers Autonomously Cross the Plant Cell Wall and Enable Protein Delivery for Stress Sensing

Delivery of proteins in plant cells can facilitate the design of desired functions by modulation of biological processes and plant traits but is currently limited by narrow host range, tissue damage, and poor scalability. Physical barriers in plants, including cell walls and membranes, limit protein delivery to desired plant tissues. Herein, a cationic high aspect ratio polymeric nanocarriers (PNCs) platform is developed to enable efficient protein delivery to plants. The cationic nature of PNCs binds proteins through electrostatic. The ability to precisely design PNCs' size and aspect ratio allowed us to find a cutoff of ≈14 nm in the cell wall, below which cationic PNCs can autonomously overcome the barrier and carry their cargo into plant cells. To exploit these findings, a reduction-oxidation sensitive green fluorescent protein (roGFP) is deployed as a stress sensor protein cargo in a model plant Nicotiana benthamiana and common crop plants, including tomato and maize. In vivo imaging of PNC-roGFP enabled optical monitoring of plant response to wounding, biotic, and heat stressors. These results show that PNCs can be precisely designed below the size exclusion limit of cell walls to overcome current limitations in protein delivery to plants and facilitate species-independent plant engineering.

Contemporary applications of vibrational spectroscopy in plant stresses and phenotyping

Plant pathogens, including viruses, bacteria, and fungi, cause massive crop losses around the world. Abiotic stresses, such as drought, salinity and nutritional deficiencies are even more detrimental. Timely diagnostics of plant diseases and abiotic stresses can be used to provide site- and doze-specific treatment of plants. In addition to the direct economic impact, this "smart agriculture" can help minimizing the effect of farming on the environment. Mounting evidence demonstrates that vibrational spectroscopy, which includes Raman (RS) and infrared spectroscopies (IR), can be used to detect and identify biotic and abiotic stresses in plants. These findings indicate that RS and IR can be used for in-field surveillance of the plant health. Surface-enhanced RS (SERS) has also been used for direct detection of plant stressors, offering advantages over traditional spectroscopies. Finally, all three of these technologies have applications in phenotyping and studying composition of crops. Such non-invasive, non-destructive, and chemical-free diagnostics is set to revolutionize crop agriculture globally. This review critically discusses the most recent findings of RS-based sensing of biotic and abiotic stresses, as well as the use of RS for nutritional analysis of foods.

Micro-/nanostructures for surface-enhanced Raman spectroscopy: Recent advances and perspectives

Surface-enhanced Raman spectroscopy (SERS) has great potential for the analysis of molecules adsorbed on metals with rough surfaces or substrates with micro-/nanostructures. Plasmonic coupling between metal nanoparticles and the morphology of the rough metal surface can produce "hot spots" that enhance Raman scattering by adsorbed molecules, typically at micro- to nanomolar concentrations, although high enhancement factors can also facilitate single-molecule detection. This phenomenon is widely applicable for chemical analysis and sensing in various fields. In this review, the latest research progress on SERS micro-/nanosensors is evaluated, and the sensors are classified according to their individual functions. Furthermore, the design principles and working mechanisms of reported SERS-active micro-/nanostructured substrates are analyzed, and the design features adopted to overcome the difficulties associated with precision detection are explored. Finally, challenges and directions for future development in this field are discussed. This review serves as a design guide for novel SERS-active substrates.

Negatively Charged Carbon Dots Employed Symplastic and Apoplastic Pathways to Enable Better Plant Delivery than Positively Charged Carbon Dots

Efficient delivery of nanoparticles (NPs) to plants is important for agricultural application. However, to date, we still lack knowledge about how NPs' charge matters for its translocation pathway, i.e., symplastic and apoplastic pathways, in plants. In this study, we synthesized and used negatively charged citrate sourced carbon dots (C-CDs, -37.97 ± 1.89 mV), Cy5 coated C-CDs (Cy5-C-CDs, -41.90 ± 2.55 mV), positively charged PEI coated carbon dots (P-CDs, +43.03 ± 1.71 mV), and Cy5 coated P-CDs (Cy5-P-CDs, +48.80 ± 1.21 mV) to investigate the role of surface charges and coatings on the employed translocation pathways (symplastic and apoplastic pathways) of charged NPs in plants. Our results showed that, different from the higher fluorescence intensity of P-CDs and Cy5-P-CDs in extracellular than intracellular space, the fluorescence intensity of C-CDs and Cy5-C-CDs was similar between intracellular and extracellular space in cucumber and cotton roots. It suggests that the negatively charged CDs were translocated via both symplastic and apoplastic pathways, but the positively charged CDs were mainly translocated via the apoplastic pathway. Furthermore, our results showed that root applied negatively charged C-CDs demonstrated higher leaf fluorescence than did positively charged P-CDs in both cucumber (8.09 ± 0.99 vs 3.75 ± 0.23) and cotton (7.27 ± 1.06 vs 3.23 ± 0.22), indicating that negatively charged CDs have a higher translocation efficiency from root to leaf than do positively charged CDs. It should be noted that CDs do not affect root cell activities, ROS level, and photosynthetic performance in cucumber and cotton, showing its good biocompatibility. Overall, this study not only figured out that root applied negatively charged CDs employed both symplastic and apoplastic pathways to do the transportation in roots compared with mainly the employment of apoplastic pathway for positively charge CDs, but also found that negatively charge CDs could be more efficiently translocated from root to leaf than positively charged CDs, indicating that imparting negative charge to NPs, at least CDs, matters for its efficient delivery in crops.

Recent advances in nano-enabled immunomodulation for enhancing plant resilience against phytopathogens

Plant diseases caused by microbial pathogens pose a severe threat to global food security. Although genetic modifications can improve plant resistance; however, environmentally sustainable strategies are needed to manage plant diseases. Nano-enabled immunomodulation involves using engineered nanomaterials (ENMs) to modulate the innate immune system of plants and enhance their resilience against pathogens. This emerging approach provides unique opportunities through the ability of ENMs to act as nanocarriers for delivering immunomodulatory agents, nanoprobes for monitoring plant immunity, and nanoparticles (NPs) that directly interact with plant cells to trigger immune responses. Recent studies revealed that the application of ENMs as nanoscale agrochemicals can strengthen plant immunity against biotic stress by enhancing systemic resistance pathways, modulating antioxidant defense systems, activating defense-related genetic pathways and reshaping the plant-associated microbiomes. However, key challenges remain in unraveling the complex mechanisms through which ENMs influence plant molecular networks, assessing their long-term environmental impacts, developing biodegradable formulations, and optimizing targeted delivery methods. This review provides a comprehensive investigation of the latest research on nano-enabled immunomodulation strategies, potential mechanisms of action, and highlights future perspectives to overcome existing challenges for sustainable plant disease management.

Automated identification of pesticide mixtures via machine learning analysis of TLC-SERS spectra

Identification of components in pesticide mixtures has been a major challenge in spectral analysis. In this paper, we assembled monolayer Ag nanoparticles on Thin-layer chromatography (TLC) plates to prepare TLC-Ag substrates with mixture separation and surface-enhanced Raman scattering (SERS) detection. Spectral scans were performed along the longitudinal direction of the TLC-Ag substrate to generate SERS spectra of all target analytes on the TLC plate. Convolutional neural network classification and spectral angle similarity machine learning algorithms were used to identify pesticide information from the TLC-SERS spectra. It was shown that the proposed automated spectral analysis method successfully classified five categories, including four pesticides (thiram, triadimefon, benzimidazole, thiamethoxam) as well as a blank TLC-Ag data control. The location of each pesticide on the TLC plate was determined by the intersection of the information curves of the two algorithms with 100 % accuracy. Therefore, this method is expected to help regulators understand the residues of mixed pesticides in agricultural products and reduce the potential risk of agricultural products to human health and the environment.

Targeted SERS Imaging and Intraoperative Real-Time Elimination of Microscopic Tumors for Improved Breast-Conserving Surgery

Breast-conserving surgery is the favorable option for breast cancer patients owing to its advantages of less aggressiveness and better cosmetic outcomes over mastectomy. However, it often suffers from postsurgical lethal recurrence due to the incomplete removal of microscopic tumors. Here, a surface-enhanced Raman scattering (SERS) surgical strategy is reported for precise delineation of tumor margins and intraoperative real-time elimination of microscopic tumor foci, which is capable of complete surgical removal of breast tumors and significantly improve the outcomes of breast-conserving surgery without local tumor recurrence. The technique is chiefly based on the human epidermal growth factor receptor 2 (HER2)-targeting SERS probes with integrated multifunctionalities of ultrahigh sensitive detection, significant HER2 expression suppression, cell proliferation inhibition, and superior photothermal ablation. In a HER2+ breast tumor mouse model, the remarkable capability of the SERS surgical strategy for complete removal of HER2+ breast tumors through SERS-guided surgical resection and intraoperative real-time photothermal elimination is demonstrated. The results show complete eradiation of HER2+ breast tumors without local recurrence, consequently delivering a 100% tumor-free survival. Expectedly, this SERS surgical strategy holds great promise for clinical treatment of HER2+ breast cancer with improved patients' survival.

High-Power Impulse Magnetron Sputter Deposition of Ag on Self-Assembled Au Nanoparticle Arrays at Low-Temperature Dewetting Conditions

Plasmons have facilitated diverse analytical applications due to the boosting signal detectability by hot spots. In practical applications, it is crucial to fabricate straightforward, large-scale, and reproducible plasmonic substrates. Dewetting treatment, via applying direct thermal annealing of metal films, has been used as a straightforward method in the fabrication of such plasmonic nanostructures. However, tailoring the evolution of the dewetting process of metal films poses considerable experimental complexities, mainly due to nanoscale structure formation. Here, we use grazing-incidence small- and wide-angle X-ray scattering for the in situ investigation of the high-power impulse magnetron sputter deposition of Ag on self-assembled Au nanoparticle arrays at low-temperature dewetting conditions. This approach allows us to examine both the direct formation of binary Au/Ag nanostructure and the consequential impact of the dewetting process on the spatial arrangement of the bimetallic nanoparticles. It is observed that the dewetting at 100 °C is sufficient to favor the establishment of a homogenized structural configuration of bimetallic nanostructures, which is beneficial for localized surface plasmon resonances (LSPRs). The fabricated metal nanostructures show potential application for the surface-enhanced Raman scattering (SERS) detection of rhodamine 6G molecules. As SERS platform, bimetallic nanostructures formed with dewetting conditions turn out to be superior to those without dewetting conditions. The method in this work is envisioned as a facile strategy for the fabrication of plasmonic nanostructures.

SERS imaging investigation of the removal efficiency of pesticide on vegetable leaves by using different surfactants

Pesticide residues on vegetables could be removed by commercial detergents to guarantee food safety, but the removal efficiencies of different formulations of detergents need to be further investigated. In this work, surface enhanced Raman scattering (SERS) imaging method due to its good space resolution as well as high sensitivity is used to track the thiram residue, and evaluate the pesticide removing efficiencies by mixtures of several surfactants at different ratios. Sodium linear alkylbenzene sulphonate-alkyl glycoside (LAS-APG) with the ratio at 5:5 and the concentration at 0.2 % show the best removing effect. In addition, HPLC method is employed to validate the results of SERS imaging. Furthermore, LAS-APG mixture could be efficiently washed out from the leaves through simple household cleaning, meaning no secondary contamination. It is perspective that SERS imaging is an effective technique to explore the effect of fruit and vegetable detergents in removing pesticide residues.

Real time imaging of cell-permeable nanoreactor with SERS for insight into cellular processes

Intracellular glucose detection is crucial due to its pivotal role in metabolism and various physiological processes. Precise glucose monitoring holds significance in diabetes management, metabolic studies, and biotechnological applications. In this study, we developed an innovative and expedient cell-permeable nanoreactor for intracellular glucose based on surface-enhanced Raman scattering (SERS). The nanoreactor was designed with gold nanoparticles (AuNPs), which were engineered with glucose oxide (GOx) and a H2O2-responsive Raman reporter 2-mercaptohydroquinone (2-MHQ). The interaction between 2-MHQ and H2O2 generated by glucose and GOx could simultaneously induce the appearance in the peak at 985 cm-1. Our results showed excellent performance in detecting glucose within the concentration range from 0.1 μM to 10 mM, with a low detection limitation of 14.72 nM. In addition, the glucose distribution in single HeLa cells was evaluated by real time SERS mapping. By combining noble metal particles and natural oxidases, the nanoreactor possesses both Raman activity and enzymatic functionality, thus enables sensitive glucose detection and facilitates imaging at a single cell level, which offers an insightful monitoring of cellular processes.

Adsorption of Cu Nanoparticles on Polystyrene-Based Microspheres

Nanoparticle composite microspheres are a versatile material with unique features and wide-ranging applications, including catalysis, biological medicine, and electronic devices. The adsorption behavior of nanoparticles on the surface of microspheres plays a crucial role in determining the further application potentials. The understanding of nanoparticle adsorption behavior on microsphere surfaces is essential for guiding future applications in nanoparticle composite microspheres. In this work, the adsorption behavior of unstable copper nanoparticles (Cu NPs) on polystyrene-based (PS-based) microspheres was investigated. The influence of PS-based microspheres' surface properties and the oxidation degree of Cu NPs were determined. The adsorption mechanism of Cu NPs on PS-based microspheres was analyzed. Furthermore, the amounts and rates of adsorption were examined. It was found that the Cu NPs can be rapidly and firmly adsorbed on the surface of carboxyl-modified polystyrene microspheres. Additionally, precise control over the distribution of Cu NPs on the surface of PS-based microspheres can be achieved by manipulating the solvent's polarity.

Sensing nature's alarm: SnO2/MXene gas sensor unveils methyl jasmonate signatures of plant insect stress

The incorporation of artificial intelligence into agriculture presents challenges, particularly due to hardware limitations, especially in sensors. Currently, pest detection relies heavily on manual scouting by humans. Therefore, the objective of this study is to create a chemoresistive sensor that enables early identification of the characteristic volatile compound, viz., methyl jasmonate, released during pest infestations. Given the lower reactivity of esters, we have fine-tuned a composite consisting of SnO2 nanoparticles and 2D-MXene sheets to enhance adsorption and selective oxidation, resulting in heightened sensitivity. The optimized composite demonstrated a notable response even at concentrations as low as 120 ppb, successfully confirming pest infestations in tomato crops.

Surface-Enhanced Raman Spectroscopy Sensor Integrated with Ag@ZIF-8@Au Core-Shell-Shell Nanowire Membrane for Enrichment, Ultrasensitive Detection, and Inactivation of Bacteria in the Environment

A core-shell-shell sandwich material is developed with silver nanowires as the core, ZIF-8 as an inner shell, and gold nanoparticles as the outer shell, namely, Ag@ZIF-8@Au nanowires (AZA-NW). Then, the synthesized AZA-NW is transformed into a surface-enhanced Raman spectroscopy (SERS) sensor (named M-AZA) by the vacuum filtration method and used to enrich, detect, and inactivate traces of bacteria in the environment. The M-AZA sensor has three main functions: (1) trace bacteria are effectively enriched, with an enrichment efficiency of 91.4%; (2) ultrasensitive detection of trace bacteria is realized, with a minimum detectable concentration of 1 × 101 CFU/mL; (3) bacteria are effectively killed up to 92.4%. The shell thickness of ZIF-8 (5-75 nm) is controlled by adjusting the synthesis conditions. At an optimum shell thickness of 15 nm, the effect of gold nanoparticles and ZIF-8 shell on the sensor's stability, SERS activity, and antibacterial performance is investigated. The simulation of the SERS sensor using the finite difference time domain (FDTD) method is consistent with the experimental results, theoretically demonstrating the role of the gold nanoparticles and the ZIF-8 shell. The sensor also shows excellent stability, safety, and generalizability. The campus water sample is then tested on-site by the M-AZA SERS sensor, indicating its potential for practical applications.

Acoustic Levitation Synthesis of Ultrahigh-Density Spherical Nucleic Acid Architectures for Specific SERS Analysis

Controllably regulating the electrostatic bilayer of nanogold colloids is a significant premise for synthesizing spherical nucleic acid (SNA) and building ordered plasmonic architectures. We develop a facile acoustic levitation reactor to universally synthesize SNAs with an ultra-high density of DNA strands, which is even higher than those of various state-of-the-art methods. Results reveal a new mechanism of DNA grafting via acoustic wave that can reconfigure the ligands on colloidal surfaces. The acoustic levitation reactor enables substrate-free three-dimentional (3D) spatial assembly of SNAs with controllable interparticle nanogaps through regulating DNA lengths. This kind of architecture may overcome the plasmonic enhancement limits by blocking electron tunneling and breaking electrostatic shielding in dried aggregations. Finite element simulations support the architecture with 3D spatial plasmonic hotspot matrix, and its ultrahigh surface-enhanced Raman scattering (SERS) capability is evidenced by in situ untargeted tracking of biomolecular events during photothermal stimulation (PTS)-induced cell death process. For biomarker diagnosis, the conjugation of adenosine triphosphate (ATP) aptamer onto SNAs enables in situ targeted tracking of ATP during PTS-induced cell death process. Particularly, the CD71 receptor and integrin α3β1 protein on PL45 cell membrance could be well distinguished by label-free SERS fingerprints when using specific XQ-2d and DML-7 aptamers, respectively, to synthesize SNA architectures. Our current acoustic levitation reactor offers a new method for synthesizing SNAs and enables both targeted and untargeted SERS analysis for tracking molecular events in living systems. It promises great potentials in biochemical synthesis and sensing in future.

Perspective on Tailored Nanostructure-Dominated SPP Effects for SERS

Localized surface plasmon resonance (LSPR) excited by an incident light can normally produce strong surface-enhanced Raman scattering (SERS) at the nanogaps among plasmonic nano-objects (so-called hot spots), which is extensively explored. In contrast, surface plasmon polaritons (SPPs) that can be generated by an incident beam via particular structures with a conservation of wave vectors can excite SERS effects as well. SPPs actually play an indispensable role in high-performance SERS devices but receive much less attention. In this perspective, SPPs and their couplings with LSPR for SERS excitations with differing effectiveness through particular plasmonic/dielectric structures/configurations, along with relevant fabrication approaches, are profoundly reviewed and commented on from a unique perspective from in situ to ex situ excitations of SERS enabled by spatiotemporally separated multiple processes of SPPs. Quantitative design of particular configurations/architectures enabling highly efficient and effective multiple processes of SPPs is particularly emphasized as one giant leap toward ultimate full quantitative design of intrinsically high-performance SERS chips and very critical for their batch manufacturability and applications as well. The viewpoints and prospects about innovative SERS devices based on tailored structure-dominated SPPs effects and their coupling with LSPR are presented and discussed.

Deciphering biomolecular complexities: the indispensable role of surface-enhanced Raman spectroscopy in modern bioanalytical research

Surface-enhanced Raman spectroscopy (SERS) has emerged as an indispensable analytical tool in biomolecular research, providing unmatched sensitivity critical for the elucidation of biomolecular structures. This review presents a thorough examination of SERS, outlining its fundamental principles, cataloging its varied applications within the biomolecular sphere, and contemplating its future developmental trajectories. We begin with a detailed analysis of SERS's mechanistic principles, emphasizing both the phenomena of surface enhancement and the complexities inherent in Raman scattering spectroscopy. Subsequently, we delve into the pivotal role of SERS in the structural analysis of diverse biomolecules, including proteins, nucleic acids, lipids, carbohydrates, and biochromes. The remarkable capabilities of SERS extend beyond mere detection, offering profound insights into biomolecular configurations and interactions, thereby enriching our comprehension of intricate biological processes. This review also sheds light on the application of SERS in real-time monitoring of various bio-relevant compounds, from enzymes and coenzymes to metal ion-chelate complexes and cellular organelles, thereby providing a holistic view and empowering researchers to unravel the complexities of biological systems. We also address the current challenges faced by SERS, such as enhancing sensitivity and resolution, developing stable and reproducible substrates, and conducting thorough analyses in complex biological matrices. Nonetheless, the continual advancements in nanotechnology and spectroscopy solidify the standing of SERS as a formidable force in biomolecular research. In conclusion, the versatility and robustness of SERS not only deepen our understanding of biomolecular intricacies but also pave the way for significant developments in medical research, therapeutic innovation, and diagnostic approaches.

Beyond the promise: Exploring the complex interactions of nanoparticles within biological systems

The exploration of nanoparticle applications is filled with promise, but their impact on the environment and human health raises growing concerns. These tiny environmental particles can enter the human body through various routes, such as the respiratory system, digestive tract, skin absorption, intravenous injection, and implantation. Once inside, they can travel to distant organs via the bloodstream and lymphatic system. This journey often results in nanoparticles adhering to cell surfaces and being internalized. Upon entering cells, nanoparticles can provoke significant structural and functional changes. They can potentially disrupt critical cellular processes, including damaging cell membranes and cytoskeletons, impairing mitochondrial function, altering nuclear structures, and inhibiting ion channels. These disruptions can lead to widespread alterations by interfering with complex cellular signaling pathways, potentially causing cellular, organ, and systemic impairments. This article delves into the factors influencing how nanoparticles behave in biological systems. These factors include the nanoparticles' size, shape, charge, and chemical composition, as well as the characteristics of the cells and their surrounding environment. It also provides an overview of the impact of nanoparticles on cells, organs, and physiological systems and discusses possible mechanisms behind these adverse effects. Understanding the toxic effects of nanoparticles on physiological systems is crucial for developing safer, more effective nanoparticle-based technologies.

Ultrabright Green-Emissive Nanodots for Precise Biological Visualization

Developing general methods to fabricate water-dispersible and biocompatible fluorescent probes will promote different biological visualization applications. Herein, we report a metal-facilitated method to fabricate ultrabright green-emissive nanodots via the one-step solvothermal treatment of rose bengal, ethanol, and various metal ions. These metal-doped nanodots show good water dispersity, ultrahigh photoluminescence quantum yields (PLQYs) (e.g., the PLQY of Fe-doped nanodots (FeNDs) was ∼97%), and low phototoxicity. Owing to the coordination effect of metal ions, the FeNDs realize glutathione detection with outstanding properties. Benefiting from the high endoplasmic reticulum (ER) affinity of the chloride group, the FeNDs can act as an ER tracker with long ER imaging capacity (FeNDs: >24 h; commercial ER tracker: ∼1 h) and superb photostability and can achieve tissue visualization in living Caenorhabditis elegans. The metal-doped nanodots represent a general nanodot preparation method and may shed new light on diverse biological visualization uses.

Dosage-sensitive and simultaneous detection of multiple small-molecule pollutants in environmental water and agriproducts using portable SERS-based lateral flow immunosensor

The co-contamination of pesticide residues and mycotoxins in agricultural products is a global concern, with the potential for cumulative and synergistic damaging effects, imposing substantial health and economic burdens to the public. The dosage-sensitive and simultaneous detection of multiple pollutants, with a heightened sensitivity in real samples, poses a significant demand and challenge. Herein, we propose a portable detection method integrating surface-enhanced Raman scattering (SERS)-with lateral flow immunoassay (LFIA), offering high sensitivity and multiplex analysis capabilities. This approach enables the simultaneous detection of imidacloprid (IMI), pyraclostrobin (PYR) and aflatoxin B1 (AFB1) through a single test strip. Utilizing the immune-specific binding between antigen and antibodies, we immobilised antibody- conjugated SERS nanotags on three test lines of the strips to generate Raman signal amplification in the proposed biosensor. Accurate quantitative analysis was performed by measuring the SERS signal intensity on the test lines. The limits of detection were 8.6 pg/mL for IMI, 97.4 pg/mL for PYR and 8.9 pg/mL for AFB1, exhibiting sensitivities 12-fold, 102-fold and11-fold higher than the colorimetric signals, respectively. Importantly, the SERS-LFIA immunosensor demonstrated robust performance when applied to real samples, yielding recoveries ranging from 86.16 % to 115.0 %, with relative standard deviation values below 8.67 %. These results underscore the excellent stability, high selectivity and reliability the proposed SERS-LFIA immunosensor. Consequently, it holds promise for the detection of multiple pesticides and mycotoxins in both environmental and agricultural samples.

Self-Organized SERS Substrates with Efficient Analyte Enrichment in the Hot Spots

One of the requirements of an efficient surface-enhanced Raman spectroscopy (SERS) substrate is a developed surface morphology with a high density of "hot spots", nm-scale spacings between plasmonic nanoparticles. Of particular interest are plasmonic architectures that could enable self-localization (enrichment) of the analyte in the hot spots. We report a straightforward method of fabrication of efficient SERS substrates that comply with these requirements. The basis of the substrate is a large-area film of tightly packed SiO2 spheres formed by their quick self-assembling upon drop casting from the solution. Thermally evaporated thin Ag layer is converted by quick thermal annealing into nanoparticles (NPs) self-assembled in the trenches between the silica spheres, i.e., in the places where the analyte molecules get localized upon deposition from solution and drying. Therefore, the obtained substrate morphology enables an efficient enrichment of the analyte in the hot spots formed by the densely arranged plasmonic NPs. The high efficiency of the developed SERS substrates is demonstrated by the detection of Rhodamine 6G down to 10-13 mol/L with an enhancement factor of ∼108, as well as the detection of low concentrations of various nonresonant analytes, both small dye molecules and large biomolecules. The developed approach to SERS substrates is very straightforward for implementation and can be further extended to using gold or other plasmonic NPs.

Direct Detection of Tobacco Mosaic Virus in Infected Plants with SERS-Sensing Hydrogels

The impact of plant pathogens on global crop yields is a major societal concern. The current agricultural diagnostic paradigm involves either visual inspection (inaccurate) or laboratory molecular tests (burdensome). While field-ready diagnostic methods have advanced in recent years, issues remain with detection of presymptomatic infections, multiplexed analysis, and requirement for in-field sample processing. To overcome these issues, we developed surface-enhanced Raman scattering (SERS)-sensing hydrogels that detect pathogens through simple contact with a leaf. In this work, we developed a novel reagentless SERS sensor for the detection of tobacco mosaic virus (TMV) and embedded it in an optimized hydrogel material to produce sensing hydrogels. To test the diagnostic application of our sensing hydrogels, we demonstrate their use to detect TMV infection in tobacco plants. This technology has the potential to shift the current agricultural diagnostic paradigm by offering a field-deployable tool for presymptomatic and multiplexed molecular identification of pathogens.

Handheld Crop Pest Sensor Using Binary Catalyst-Loaded Nano-SnO2 Particles for Oxidative Signal Amplification

In agriculture, pest management is a major challenge. Crop releases volatiles in response to the pest; hence, sensing these volatile signals at a very early stage will ease pest management. Here, binary catalyst-loaded SnO2 nanoparticles of <5 nm were synthesized for the repeated capture and oxidation of the signature volatile and its products to amplify the chemoresistive signal to detect concentrations as low as ≈120 ppb. The sensitivity may be due to the presence of the elements in the Sn-Fe-Pt bond evidenced by extended X-ray absorption fine-structure spectroscopy (EXAFS) that captures and oxidize the volatile without escaping. This strong catalyst may oxidize nontarget volatiles and can cause false signals; hence, a molecular sieve filter has been coupled to ensure high selectivity for the detection ofTuta absolutainfestation in tomato. Finally, with the support of a mobile power bank, the optimized sensor has been assembled into a lightweight handheld device.

Porous carbon film/WO3-x nanosheets based SERS substrate combined with deep learning technique for molecule detection

The Surface-enhanced Raman scattering (SERS) is an attractive optical detecting method with high sensitivity and detectivity, however challenges on large-area signal uniformity and complex spectra analysis methods always retards its wide application. Herein, a highly sensitive and uniform SERS detection strategy supported by porous carbon film/WO3-x nanosheets (PorC/WO3-x) based noble-metal-free SERS substrate and deep learning algorithm are reported. Experimentally, the PorC/WO3-x substrate was prepared by high-temperature annealing the PorC/WO3 films under the argon atmosphere. The defect density of the WO3 was controlled by tuning the reducing reaction time during the annealing process. The SERS performance was evaluated by using R6G as the Raman reporter, it showed that the SERS intensity obtained on the substrate with the optimal annealing time of 3 h was about 8 times as high as that obtained on the PorC/WO3 substrate without annealing treatment. And detection limit of 10-7 M and Raman enhancement factor of 106 could be achieved. Moreover, the above optimal SERS substrate was utilized to detect flavonoids of quercetin, 3-hydroxyflavone and flavone, and a deep learning algorithms was incorporated to identify the quercetin. It revealed that quercetin can be accurately detected within the above flavonoids, and lowest detectable concentration of 10-5 M can be achieved.

Heat and Wheat: Adaptation strategies with respect to heat shock proteins and antioxidant potential; an era of climate change

Extreme changes in weather including heat-wave and high-temperature fluctuations are predicted to increase in intensity and duration due to climate change. Wheat being a major staple crop is under severe threat of heat stress especially during the grain-filling stage. Widespread food insecurity underscores the critical need to comprehend crop responses to forthcoming climatic shifts, pivotal for devising adaptive strategies ensuring sustainable crop productivity. This review addresses insights concerning antioxidant, physiological, molecular impacts, tolerance mechanisms, and nanotechnology-based strategies and how wheat copes with heat stress at the reproductive stage. In this study stress resilience strategies were documented for sustainable grain production under heat stress at reproductive stage. Additionally, the mechanisms of heat resilience including gene expression, nanomaterials that trigger transcription factors, (HSPs) during stress, and physiological and antioxidant traits were explored. The most reliable method to improve plant resilience to heat stress must include nano-biotechnology-based strategies, such as the adoption of nano-fertilizers in climate-smart practices and the use of advanced molecular approaches. Notably, the novel resistance genes through advanced molecular approach and nanomaterials exhibit promise for incorporation into wheat cultivars, conferring resilience against imminent adverse environmental conditions. This review will help scientific communities in thermo-tolerance wheat cultivars and new emerging strategies to mitigate the deleterious impact of heat stress.

Plasmonic nanosensors for pharmaceutical and biomedical analysis

The detection and identification of clinical biomarkers with related sensitivity have become a source of considerable concern for biomedical analysis. There have been increasing efforts toward the development of single-molecule analytical platforms to overcome this concern. The latest developments in plasmonic nanomaterials include fascinating advances in energy, catalyst chemistry, optics, biotechnology, and medicine. Nanomaterials can be successfully applied to biomolecule and drug detection in plasmonic nanosensors for pharmaceutical and biomedical analysis. Plasmonic-based sensing technology exhibits high sensitivity and selectivity depending on surface plasmon resonance (SPR) or localized surface plasmon resonance (LSPR) phenomena. In this critical paper, we offer an overview of the methodology of the SPR, LSPR, surface-enhanced Raman scattering (SERS), surface-enhanced infrared absorption (SEIRA), surface-enhanced fluorescence (SEF), and plasmonic nanoplatforms advanced for pharmaceutical and biomedical applications. First of all, we present here a brief discussion of the above trends. We have devoted the last section to the explanation of SPR, LSPR, SERS, SEIRA, and SEF platforms, which have found a wide range of applications, and reviewed recent advances for biomedical and pharmaceutical analysis.

UV-B responses in the spotlight: Dynamic photoreceptor interplay and cell-type specificity

Plants are constantly exposed to a multitude of external signals, including light. The information contained within the full spectrum of light is perceived by a battery of photoreceptors, each with specific and shared signalling outputs. Recently, it has become clear that UV-B radiation is a vital component of the electromagnetic spectrum, guiding growth and being crucial for plant fitness. However, given the large overlap between UV-B specific signalling pathways and other photoreceptors, understanding how plants can distinguish UV-B specific signals from other light components deserves more scrutiny. With recent evidence, we propose that UV-B signalling and other light signalling pathways occur within distinct tissues and cell-types and that the contribution of each pathway depends on the type of response and the developmental stage of the plant. Elucidating the precise site(s) of action of each molecular player within these signalling pathways is key to fully understand how plants are able to orchestrate coordinated responses to light within the whole plant body. Focusing our efforts on the molecular study of light signal interactions to understand plant growth in natural environments in a cell-type specific manner will be a next step in the field of photobiology.

Spectroscopic techniques for monitoring stem cell and organoid proliferation in 3D environments for therapeutic development

Spectroscopic techniques for monitoring stem cell and organoid proliferation have gained significant attention in therapeutic development. Spectroscopic techniques such as fluorescence, Raman spectroscopy, and infrared spectroscopy offer noninvasive and real-time monitoring of biochemical and biophysical changes that occur during stem cell and organoid proliferation. These techniques provide valuable insight into the underlying mechanisms of action of potential therapeutic agents, allowing for improved drug discovery and screening. This review highlights the importance of spectroscopic monitoring of stem cell and organoid proliferation and its potential impact on therapeutic development. Furthermore, this review discusses recent advances in spectroscopic techniques and their applications in stem cell and organoid research. Overall, this review emphasizes the importance of spectroscopic techniques as valuable tools for studying stem cell and organoid proliferation and their potential to revolutionize therapeutic development in the future.

Fast Raman imaging through the combination of context-aware matrix completion and low spectral resolution

Raman hyperspectral imaging is an effective method for label-free imaging with chemical specificity, yet the weak signals and correspondingly long integration times have hindered its wide adoption as a routine analytical method. Recently, low resolution Raman imaging has been proposed to improve the spectral signal-to-noise ratio, which significantly improves the speed of Raman imaging. In this paper, low resolution Raman spectroscopy is combined with "context-aware" matrix completion, where regions of the sample that are not of interest are skipped, and the regions that are measured are under-sampled, then reconstructed with a low-rank constraint. Both simulations and experiment show that low-resolution Raman boosts the speed and image quality of the computationally-reconstructed Raman images, allowing deeper sub-sampling, reduced exposure time, and an overall >10-fold improvement in imaging speed, without sacrificing chemical specificity or spatial image quality. As the method utilizes traditional point-scan imaging, it retains full confocality and is "backwards-compatible" with pre-existing traditional Raman instruments, broadening the potential scope of Raman imaging applications.

Crystal-Phase Engineering of Two-Dimensional Transition-Metal Dichalcogenides for Surface-Enhanced Raman Scattering: A Perspective

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) have emerged as promising materials for surface-enhanced Raman scattering (SERS) due to their unique electronic, optical, and mechanical properties. In this Perspective, we briefly introduce the fundamental properties, crystal-phase configurations, and phase transition strategies of TMDs materials. We then discuss the importance of the crystal phase in determining the SERS effect of TMDs, highlighting recent advances in phase-engineering approaches to affording remarkable SERS performance. By considering the current challenges and future directions for improving the crystal-phase engineering of TMDs in SERS, we also offer new insights into the design and synthesis of more promising TMD-based SERS substrates.

Interfacial Self-Assembly of Surfactant-Free Au Nanoparticles as a Clean Surface-Enhanced Raman Scattering Substrate for Quantitative Detection of As5+ in Combination with Convolutional Neural Networks

Surface-enhanced Raman scattering (SERS) is a highly sensitive tool in the field of environmental testing. However, the detection and accurate quantification of weakly adsorbed molecules (such as heavy metal ions) remain a challenge. Herein, we combine clean SERS substrates capable of capturing heavy metal ions with convolutional neural network (CNN) algorithm models for quantitative detection of heavy metal ions in solution. The SERS substrate consists of surfactant-free Au nanoparticles (NPs) and l-cysteine molecules. As plasmonic nanobuilt blocks, surfactant-free Au NPs without physical or chemical barriers are more accessible to target molecules. The amino and carboxyl groups in the l-cysteine molecule can chelate As5+ ions. The CNN algorithm model is applied to quantify and predict the concentration of As5+ ions in samples. The results demonstrated that this strategy allows for fast and accurate prediction of As5+ ion concentrations, and the determination coefficient between the predicted and actual values is as high as 0.991.

Plasmonic nanorod probes' journey inside plant cells for in vivo SERS sensing and multimodal imaging

Nanoparticle-based platforms are gaining strong interest in plant biology and bioenergy research to monitor and control biological processes in whole plants. However, in vivo monitoring of biomolecules using nanoparticles inside plant cells remains challenging due to the impenetrability of the plant cell wall to nanoparticles beyond the exclusion limits (5-20 nm). To overcome this physical barrier, we have designed unique bimetallic silver-coated gold nanorods (AuNR@Ag) capable of entering plant cells, while conserving key plasmonic properties in the near-infrared (NIR). To demonstrate cellular internalization and tracking of the nanorods inside plant tissue, we used a comprehensive multimodal imaging approach that included transmission electron microscopy (TEM), confocal fluorescence microscopy, two-photon luminescence (TPL), X-ray fluorescence microscopy (XRF), and photoacoustics imaging (PAI). We successfully acquired SERS signals of nanorods in vivo inside plant cells of tobacco leaves. On the same leaf samples, we applied orthogonal imaging methods, TPL and PAI techniques for in vivo imaging of the nanorods. This study first demonstrates the intracellular internalization of AuNR@Ag inside whole plant systems for in vivo SERS analysis in tobacco cells. This work demonstrates the potential of this nanoplatform as a new nanotool for intracellular in vivo biosensing for plant biology.