Selective Surface Enhanced Raman Scattering for Quantitative Detection of Lung Cancer Biomarkers in Superparticle@MOF Structure

Harnessing Surface-Enhanced Raman Spectroscopy for Breath-Based Diagnostics

Human breath contains a myriad of analytes that are associated with human health conditions, making it a noninvasive source of biomarkers. Researchers and engineers are pushing the boundaries of breath analysis for the next generation of diagnostics. Breath analysis with surface enhanced Raman spectroscopy, which allows for the identification of molecular fingerprints in a simple way, represents a powerful platform for the next generation of sensors which are expected to provide tools for personalized healthcare and preventive medicine.

Research advances in the diagnosis of infectious disease by aptasensor technology

Infectious diseases remain a major challenge to public health. The accurate and timely detection of pathogens responsible for these diseases is essential for controlling their spread, supporting clinical diagnosis, and enabling the application of appropriate therapies. Traditionally, the antibody-based assay has been the primary method for pathogen detection. However, recent advancements in aptamer-based technologies have initiated a transformative shift in diagnostic approaches. Aptamer-based sensors (aptasensors) are characterized by lower production costs and greater flexibility, making them compatible with various detection techniques. This broad applicability facilitates multifaceted, high-throughput applications, significantly improving the capacity to monitor and detect infectious diseases. In this review, we introduce the pathogenic mechanisms and characteristics of pathogens, provide an overview of recent advancements in the development of aptasensors for pathogen detection and highlight their versatility in identifying various infectious disease pathogens, including viruses, bacteria, parasites and other microorganisms. We systematically categorize aptasensors according to their detection mechanisms, including colorimetry, fluorescence, chemiluminescence, surface-enhanced Raman spectroscopy (SERS), surface plasmon resonance (SPR), electrochemistry and incorporation of field-effect transistors (FETs). We further demonstrate how these platforms leverage pathogen-specific biological features to achieve ultrasensitive and rapid diagnostics. Further optimization and validation of aptasensor platforms are anticipated to accelerate their clinical translation and industrialization. Advancing these innovative technologies will be crucial to meeting the growing demand for rapid, accurate and reliable pathogen detection across diverse clinical and environmental conditions, ultimately strengthening the ability to respond effectively to infectious disease threats.

Collaborative integration of SERS and QCM sensing for label-free multi-component gas detection

The effective qualitative and quantitative detection of mixed components of volatile organic compounds (VOCs) with similar molecular structures has always been a challenge and hotpoint in the research. A novel quartz-crystal microbalance (QCM) nanocomposite sensor integrated with a surface-enhanced Raman scattering (SERS) detection platform for multi-component gas analysis was proposed and fabricated in this paper. MIL-100 (Fe)/PAN composite fibers were developed on QCM via electrospinning of polyacrylonitrile (PAN) and hydrothermal synthesis, addressing the integration issues of MIL-100 particles in devices while maintaining high specific surface area. The MIL-100(Fe)/PAN@QCM sensor can simultaneously collect QCM frequency responses and SERS spectra, enabling the quantitative and qualitative detection of toluene and benzaldehyde in mixtures. The linear response relationship between the frequency obtained by the QCM sensor and the concentration of toluene and benzaldehyde gases was in the range of 0-100 ppm, and the limits of detections were 0.57 and 0.86 ppm, respectively. Additionally, an algorithm, that considered the relationship among the QCM frequency response signal, intensity values of the characteristic peaks in the SERS spectra, and the gas concentration, was developed and applied to measure the mixed gases of toluene and benzaldehyde in the concentration range of 0-100 ppm. The relative standard deviations (RSDs) of spiked sample determinations were found to be in the range of 3-8%. This work provided a new method for the efficient and rapid detection of gas molecules with similar structures, which could be extended and applied to detect more multi-component gas mixtures.

Pushing the Frontiers: Artificial Intelligence (AI)-Guided Programmable Concepts in Binary Self-Assembly of Colloidal Nanoparticles

Colloidal nanoparticle self-assembly is a key area in nanomaterials science, renowned for its ability to design metamaterials with tailored functionalities through a bottom-up approach. Over the past three decades, advancements in nanoparticle synthesis and assembly control methods have propelled the transition from single-component to binary assemblies. While binary assembly has been recognized as a significant concept in materials design, its potential for intelligent and customized assembly has often been overlooked. It is argued that the future trend in the assembly of binary nanocrystalline superlattices (BNLSs) can be analogous to the '0s' and '1s' in computer programming, and customizing their assembly through precise control of these basic units could significantly expand their application scope. This review briefly recaps the developmental trajectory of nanoparticle assembly, tracing its evolution from simple single-component assemblies to complex binary co-assemblies and the unique property changes they induce. Of particular significance, this review explores the future prospects of binary co-assembly, viewed through the lens of 'AI-guided programmable assembly'. Such an approach has the potential to shift the paradigm from passive assembly to active, intelligent design, leading to the creation of new materials with disruptive properties and functionalities and driving profound changes across multiple high-tech fields.

State-of-the-Art, Insights, and Perspectives for MOFs-Nanocomposites and MOF-Derived (Nano)Materials

Composite structures created from metal‒organic framework (MOF) matrices are reviewed in this work. Depending on the nature of the second component apart from the MOF platform, several synergistic properties may arise; at the same time, the initial features of the single constituent materials are usually maintained, and individual shortcomings are mitigated. Currently, timely energy and environmental challenges necessitate the quest for more advanced materials and technologies. Significant developments in MOF-nanocomposites have enabled their application across a wide range of modern and traditional fields. This review demonstrates in an exhaustive and critical way a broad range of MOF-based nanocomposites, namely, MOF/perovskite nanoparticles (NPs), MOF/metal (non-iron) oxide NPs, MOF/Fe3O4 NPs, MOF/metal chalcogenide NPs, MOF/metal NPs, and MOF/carbon-based materials, as well as nanocomposites of MOFs with other semiconductor NPs. Key points related to the synthesis, characterization, and applications of these materials are provided. Depending on their configuration, the composites under discussion can be applied in domains such as photoelectrochemical sensing, antibiotic/dye degradation, optoelectronics, photovoltaics, catalysis, solar cells, supercapacitors, batteries, water remediation, and drug loading. Sometimes, MOFs can undergo certain processes (e.g. pyrolysis) and act as precursors for composite materials with appealing characteristics. Therefore, a special section in the manuscript is devoted to MOF-derived NP composites. Toward the end of the text, we conclude while also describing the challenges and possibilities for further investigations in the umbrella of material categories analyzed herein. Despite the progress achieved, key questions remain to be answered regarding the relationships among the morphology, properties, and polyvalent activity of these materials. The present work aims to shed light on most of their aspects and innovative prospects, facilitating a deeper comprehension of the underlying phenomena, functionality, and mechanistic insights governing their behavior.

A Review on the Recent Progress of Metal-Organic Frameworks Based Surface Enhanced Raman Scattering Sensors

Surface enhanced Raman scattering (SERS) has evolved into a significant fingerprint spectroscopic technique for rapidly and nonintrusively tracing target analytes through effective SERS substrates. Metal-organic frameworks (MOFs), as a boom crystalline porous material, serve as promising SERS substrates by accommodating noble metal nanoparticles (NPs) to produce MOFs-based SERS-active materials. Recently, MOFs-based SERS materials (MNPs/MOFs) have gained significant attention due to their enhanced sensing performance. The unique porous nature of MOFs provides an efficient capture capability for analytes, while their shells prevent NPs from oxidization and corrosion, thereby enhancing the consistency of SERS substrates. So far, numerous MNPs/MOFs sensors have been documented. This review outlines the research progress of MNPs/MOFs composites, focusing on the classification, synthesis strategies, and applications in environment analysis, real-time monitoring, food safety, etc.

Recent progress in fluorescent chemosensors for selective aldehyde detection

Aldehydes (R-CHO) are volatile and chemically active compounds prevalent in the environment, industrial chemicals, food fermentation, and human metabolism. Their release into the atmosphere can lead to pollution and adverse health effects, from mild irritation to severe respiratory and immune system damage. Among aldehydes, formaldehyde (FA) and acetaldehyde (AA) are notable indoor air pollutants with stringent safety limits set by organizations like WHO and OSHA. Current detection techniques, including gas and liquid chromatography, while highly accurate, are expensive and require trained personnel. Conventional sensors, such as semiconductor and chemiresistive types, offer portability and online detection but are hindered by poor selectivity and sensitivity. Optical chemosensors, which operate based on fluorescence or colorimetric changes induced by chemical interactions, have emerged as a promising alternative due to their high sensitivity, selectivity, cost-effectiveness, and portability. This review explores the advancements in optical chemosensors for aldehyde detection, emphasizing novel molecular designs utilizing mechanisms like imine bond formation, cyclization reactions, and aza-Cope rearrangements etc. The applications of these sensors in environmental monitoring, biomedical analysis, and other industries are highlighted, showcasing their potential for real-time, low-concentration detection of aldehydes in diverse settings.

Janus Membrane-Based Wearable Dual-Channel SERS Sensor for Sweat Collection and Monitoring of Lactic Acid and pH Levels

Sweat, as a metabolic byproduct, encompasses a diverse array of molecular information pertinent to our physiological states and overall health. The extraction of minute quantities of sweat, coupled with sensitive monitoring and identification of its internal molecular components, constitutes an effective strategy for assessing bodily conditions. We engineer a Janus membrane utilizing electrospinning techniques for application on human skin to facilitate sweat collection. The hydrophilic layer efficiently extracts trace amounts of sweat secreted by the skin, while the hydrophobic layer maintains a dry contact interface, thereby enhancing the user's comfort during wear. Furthermore, we integrated functional self-assembled nanoparticle layers onto the hydrophilic surface to develop a dual-channel high-sensitivity sensor array capable of measuring pH and lactic acid concentrations. This system adeptly distinguishes between anaerobic exercise and calm state scenarios concerning pH and lactic acid levels.

Breakthrough in plasmonic enhanced MOFs: Design, synthesis, and catalytic mechanisms for various photocatalytic applications

Integrating metal-organic framework MOFs with plasmonic nanoparticles (NPs) addresses a significant shortcoming of standard plasmonic platforms: their low efficacy with non-adsorbing compounds. The corporation of porous MOFs complements the plasmonic characteristics, allowing for a broader range of applications. This study highlights recent advancements in the design, synthesis, structural engineering, and functional properties of heterostructures combining plasmonic NPs with MOFs, focusing on their plasmonic and catalytic reaction behaviors. These developments have greatly enhanced the protentional of plasmonic NPs-MOFs heterojunction in nanofabrication and various applications, such as chemical sensing techniques like localized surface plasmon resonance (LSPR) surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorbance (SEIRA). Additionally, the study thoroughly examines the interface interaction and photocatalytic performance of plasmonic NPs-MOFs. Various practical applications of plasmonic NPs-MOFs heterojunction are explored, including their promising role in tackling environmental challenges like industrial water pollution. Furthermore, we have a detailed discussion of various photocatalysis processes, including water splitting, CO2 reduction, pollutant degradation, and various sensing applications. Identifying current limitations and outlining future research directions to bridge existing knowledge gaps, including interface interaction, photocatalytic performance, and practical applications providing a comprehensive understanding, are the main aims of this review to inspire the development of next-generation plasmonic NPs-MOFs materials. It concludes by discussing future directions and challenges in composite development, emphasizing their potential to provide sustainable and efficient solutions for environmental remediation and energy conversion.

Surface-Enhanced Raman Spectroscopy for Biomedical Applications: Recent Advances and Future Challenges

The year 2024 marks the 50th anniversary of the discovery of surface-enhanced Raman spectroscopy (SERS). Over recent years, SERS has experienced rapid development and became a critical tool in biomedicine with its unparalleled sensitivity and molecular specificity. This review summarizes the advancements and challenges in SERS substrates, nanotags, instrumentation, and spectral analysis for biomedical applications. We highlight the key developments in colloidal and solid SERS substrates, with an emphasis on surface chemistry, hotspot design, and 3D hydrogel plasmonic architectures. Additionally, we introduce recent innovations in SERS nanotags, including those with interior gaps, orthogonal Raman reporters, and near-infrared-II-responsive properties, along with biomimetic coatings. Emerging technologies such as optical tweezers, plasmonic nanopores, and wearable sensors have expanded SERS capabilities for single-cell and single-molecule analysis. Advances in spectral analysis, including signal digitalization, denoising, and deep learning algorithms, have improved the quantification of complex biological data. Finally, this review discusses SERS biomedical applications in nucleic acid detection, protein characterization, metabolite analysis, single-cell monitoring, and in vivo deep Raman spectroscopy, emphasizing its potential for liquid biopsy, metabolic phenotyping, and extracellular vesicle diagnostics. The review concludes with a perspective on clinical translation of SERS, addressing commercialization potentials and the challenges in deep tissue in vivo sensing and imaging.

Recent advances in the design of SERS substrates and sensing systems for (bio)sensing applications: Systems from single cell to single molecule detection

The Raman effect originates from spontaneous inelastic scattering of photons by matter. These photons provide a characteristic fingerprint of this matter, and are extensively utilized for chemical and biological sensing. The inherently lower generation of these Raman scattered photons, do not hold potential for their direct use in sensing applications. Surface enhanced Raman spectroscopy (SERS) overcomes the low sensitivity associated with Raman spectroscopy and assists the sensing of diverse analytes, including ions, small molecules, inorganics, organics, radionucleotides, and cells. Plasmonic nanoparticles exhibit localized surface plasmon resonance (LSPR) and when they are closely spaced, they create hotspots where the electromagnetic field is significantly enhanced. This amplifies the Raman signal and may offer up to a 10 14-fold SERS signal enhancement. The development of SERS active substrates requires further consideration and optimization of several critical features such as surface periodicity, hotspot density, mitigation of sample or surface autofluorescence, tuning of surface hydrophilicities, use of specific (bio) recognition elements with suitable linkers and bioconjugation chemistries, and use of appropriate optics to obtain relevant sensing outcomes in terms of sensitivity, cross-sensitivity, limit of detection, signal-to-noise ratio (SNR), stability, shelf-life, and disposability. This article comprehensively reviews the recent advancements on the use of disposable materials such as commercial grades of paper, textiles, glasses, polymers, and some specific substrates such as blue-ray digital versatile discs (DVDs) for use as SERS-active substrates for point-of-use (POU) sensing applications. The advancements in these technologies have been reviewed and critiqued for analyte detection in resource-limited settings, highlighting the prospects of applications ranging from single-molecule to single-cell detection. We conclude by highlighting the prospects and possible avenues for developing viable field deployable sensors holding immense potential in environmental monitoring, food safety and biomedical diagnostics.

Emerging trends in SERS-based veterinary drug detection: multifunctional substrates and intelligent data approaches

Veterinary drug residues in poultry and livestock products present persistent challenges to food safety, necessitating precise and efficient detection methods. Surface-enhanced Raman scattering (SERS) has been identified as a powerful tool for veterinary drug residue analysis due to its high sensitivity and specificity. However, the development of reliable SERS substrates and the interpretation of complex spectral data remain significant obstacles. This review summarizes the development process of SERS substrates, categorizing them into metal-based, rigid, and flexible substrates, and highlighting the emerging trend of multifunctional substrates. The diverse application scenarios and detection requirements for these substrates are also discussed, with a focus on their use in veterinary drug detection. Furthermore, the integration of deep learning techniques into SERS-based detection is explored, including substrate structure design optimization, optical property prediction, spectral preprocessing, and both qualitative and quantitative spectral analyses. Finally, key limitations are briefly outlined, such as challenges in selecting reporter molecules, data imbalance, and computational demands. Future trends and directions for improving SERS-based veterinary drug detection are proposed.

Surface Enhanced Raman Scattering for Biomolecular Sensing in Human Healthcare Monitoring

Since the 1980s, surface enhanced Raman scattering (SERS) has been used for the rapid and sensitive detection of biomolecules. Whether a label-free or labeled assay is adopted, SERS has demonstrated low limits of detection in a variety of biological matrices. However, SERS analysis has been confined to the laboratory due to several reasons such as reproducibility and scalability, both of which have been discussed at length in the literature. Another possible issue with the lack of widespread adoption of SERS is that its application in point of use (POU) testing is only now being fully explored due to the advent of portable Raman spectrometers. Researchers are now investigating how SERS can be used as the output on several POU platforms such as lateral flow assays, wearable sensors, and in volatile organic compound (VOC) detection for human healthcare monitoring, with favorable results that rival the gold standard approaches. Another obstacle that SERS faces is the interpretation of the wealth of information obtained from the platform. To combat this, machine learning is being explored and has been shown to provide quick and accurate analysis of the generated data, leading to sensitive detection and discrimination of many clinically relevant biomolecules. This review will discuss the advancements of SERS combined with POU testing and the strength that machine learning can bring to the analysis to produce a powerful combined platform for human healthcare monitoring.

Metal-organic framework-based SERS probes with enrichment capability for trace detection: applications in biomarkers and pollutants

Surface-enhanced Raman scattering (SERS) has emerged as a powerful tool for trace substances detection due to its exceptional sensitivity, high anti-interference capability, and ease of operation, enabling detection at the single-molecule level. This makes SERS particularly promising for applications such as environmental monitoring, biomedical diagnostics, and food safety. Despite these advantages, SERS faces limitations due to the difficulty of enriching trace substances and the small Raman scattering cross sections of certain molecules. Metal-organic frameworks (MOFs), characterized by their high surface areas and porosity, tunable structures, and diverse functionalities, offer a promising solution to these challenges. By integrating MOFs with SERS technology, we explore how MOF-based SERS probes can enhance the sensitivity, selectivity, and efficiency of trace substance detection through mechanisms such as analyte enrichment, selective molecular capture, and electromagnetic field manipulation. In this paper, a comprehensive review of the structure and synthesis of MOF-SERS composites is presented, with an emphasis on their application in the detection of trace substances. The paper also discusses key challenges in the design and optimization of MOF-based SERS probes, particularly in terms of stability, reproducibility, and integration with existing detection platforms, aiming to broaden their practical applications and improve their detection efficiency.

Breath Analysis via Surface Enhanced Raman Spectroscopy

Breath analysis is increasingly recognized as a powerful noninvasive diagnostic technique, and a plethora of exhaled volatile biomarkers have been associated with various diseases. However, traditional analytical methodologies are not amenable to high-throughput diagnostic applications at the point of need. An optical spectroscopic technique, surface-enhanced Raman spectroscopy (SERS), mostly used in the research setting for liquid sample analysis, has recently been applied to breath-based diagnostics. This promising noninvasive diagnostic tool has been demonstrated for the identification of various diseases, including lung cancer, gastric cancer, and diabetes. The versatility of SERS has enabled the use of different diagnostic strategies and allowed for fast and accurate detection of small analytes in exhaled breath. In this review, we provide an overview of recent advances in SERS-based breath analysis, focusing on sensors for the detection of gases and volatile organic compounds (VOCs) in exhaled breath, and highlight generic strategies for sample preconcentration and methods for spectral analysis. We aim to provide an overview of the state of the art and inspiration for further SERS investigation of expiration.

Understanding the Electrochemical MOF Sensors in Detecting Cancer with Special Emphasis on Breast Carcinoma Biomarkers

Cancer is a disease that claims millions of lives each year, often because early symptoms go unnoticed, a situation which severely impacts society. Point-of-care biosensors using metal-organic frameworks (MOFs) have the power to transform cancer biomarker detection due to their exceptional structural and conductive properties. This review discusses the electrochemical sensor's design and development of electroactive MOF materials with mechanistic insights. It highlights recent advancements in utilizing MOF composites to effectively detect cancer biomarkers in real samples. The emphasis on the critical application of MOFs in breast cancer biomarker detection presents its importance for women's health. The review thoroughly examines the adjustable structures, porosity, and fabrication capabilities of MOFs in identifying cancer biomarkers. It provides a detailed analysis of methods to enhance the sensitivity and applicability of MOF composites for cancer detection. Furthermore, the review explores strategies to boost sensor performance, tackles existing challenges head-on, and outlines promising prospects. It emphasizes the urgent need for advanced cancer detection tools and aims to motivate researchers to develop innovative solutions.

Surface-enhanced Raman spectroscopy: a half-century historical perspective

Surface-enhanced Raman spectroscopy (SERS) has evolved significantly over fifty years into a powerful analytical technique. This review aims to achieve five main goals. (1) Providing a comprehensive history of SERS's discovery, its experimental and theoretical foundations, its connections to advances in nanoscience and plasmonics, and highlighting collective contributions of key pioneers. (2) Classifying four pivotal phases from the view of innovative methodologies in the fifty-year progression: initial development (mid-1970s to mid-1980s), downturn (mid-1980s to mid-1990s), nano-driven transformation (mid-1990s to mid-2010s), and recent boom (mid-2010s onwards). (3) Illuminating the entire journey and framework of SERS and its family members such as tip-enhanced Raman spectroscopy (TERS) and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) and highlighting the trajectory. (4) Emphasizing the importance of innovative methods to overcome developmental bottlenecks, thereby expanding the material, morphology, and molecule generalities to leverage SERS as a versatile technique for broad applications. (5) Extracting the invaluable spirit of groundbreaking discovery and perseverant innovations from the pioneers and trailblazers. These key inspirations include proactively embracing and leveraging emerging scientific technologies, fostering interdisciplinary cooperation to transform the impossible into reality, and persistently searching to break bottlenecks even during low-tide periods, as luck is what happens when preparation meets opportunity.

Porous Nanoframe Based Plasmonic Structure With High-Density Hotspots for the Quantitative Detection of Gaseous Benzaldehyde

Owing to its high sensitivity, surface-enhanced Raman scattering (SERS) has immense potential for the identification of lung cancer from the variation in volatile biomarkers in the exhaled gas. However, two prevailing factors limit the application of SERS: 1) the adsorption of target molecules into SERS hotspots and 2) the detection specificity in multiple interference environments. To improve the density of the SERS hotspots, 3D Au@Ag-Au particles are prepared in a porous nanoframes (PPFs) based plasmonic structure, which facilitated a richer local electromagnetic field distribution among the Au nanocubic (NC) cores, Au-Ag porous nanoframes, and Au nanoparticles, thereby promoting the adsorption probability of gaseous aldehydes into the hotspots. L-cysteines (l-Cys)-modified 3D Au@Ag-Au PPFs are proposed as a benzaldehyde (BA) gas detection carrier to accurately detect biomarkers in complex exhaled gases and eliminate interference from other components. Unlike the conventional use of 4-aminothiophenol as a linker molecule, the novel L-Cys-modified SERS substrate is sensitive toward the aldehyde molecules and immune to other volatile organic compounds (ethanol, cyclohexane, toluene, etc.). Furthermore, a medical mask consisting of this SERS substrate is designed to realize intelligent detection of gaseous BA concentrations assisted by a machine learning algorithm.

Surface-Enhanced Raman Spectroscopy for Nitrite Detection

Nitrite is an important chemical intermediate in the nitrogen cycle and is ubiquitously present in environmental and biological systems as a metabolite or additive in the agricultural and food industries. However, nitrite can also be toxic in excessive concentrations. As such, the development of quick, sensitive, and portable assays for its measurement is desirable. In this review, we summarize the working principles and applications of surface-enhanced Raman spectroscopy (SERS) as a rapid, portable, and ultrasensitive method for nitrite detection and showcase its applicability in various water, food, and biological samples. The challenges and opportunities for future developments are also discussed.

Polydopamine-Mediated, Centrifugal Force-Driven Gold Nanoparticle-Deposited Microneedle SERS Sensors for Food Safety Monitoring Theoretical Study of the SERS Substrate Fabrication

Microneedle (MN) sensors have great promise for food safety detection, but the rapid preparation of MNs for surface-enhanced Raman scattering (SERS) sensors with tunable and homogeneous nanoparticles remains a great challenge. To address this, a SERS sensor of gold nanoparticles@polydopamine@poly(methyl methacrylate) MN (AuNPs@PDA@PMMA-MN) was developed. The extended-Derjaguin-Landau-Verwey-Overbeek theory was applied to calculate the interaction energy between AuNPs and PDA. It was confirmed that an appropriate centrifugal force could be utilized to overcome the electrostatic repulsion between AuNPs and PDA. Together with the adhesion force of PDA, AuNPs can therefore be uniformly and densely deposited on the MN substrate. The AuNPs@PDA@PMMA-MN had an enhancement factor of up to 1.74 × 106 for R6G. Furthermore, a MN sensor for the selective detection of putrescine and cadaverine was successfully constructed by modifying 4-mercaptobenzaldehyde (4-MBA) on AuNPs@PDA@PMMA-MN substrates. This sensor could quantitatively detect putrescine and cadaverine in meat. It has been successfully applied to the in situ detection of putrescine and cadaverine in real meat samples. The AuNPs@PDA@PMMA-MN SERS sensor has the advantages of facile fabrication, high sensitivity, high specificity, and online, in situ detection capability. It is expected to have applications in food quality testing, environmental monitoring, and disease diagnosis.

SERS-Based Local Field Enhancement in Biosensing Applications

Surface-enhanced Raman scattering (SERS) stands out as a highly effective molecular identification technique, renowned for its exceptional sensitivity, specificity, and non-destructive nature. It has become a main technology in various sectors, including biological detection and imaging, environmental monitoring, and food safety. With the development of material science and the expansion of application fields, SERS substrate materials have also undergone significant changes: from precious metals to semiconductors, from single crystals to composite particles, from rigid to flexible substrates, and from two-dimensional to three-dimensional structures. This report delves into the advancements of the three latest types of SERS substrates: colloidal, chip-based, and tip-enhanced Raman spectroscopy. It explores the design principles, distinctive functionalities, and factors that influence SERS signal enhancement within various SERS-active nanomaterials. Furthermore, it provides an outlook on the future challenges and trends in the field. The insights presented are expected to aid researchers in the development and fabrication of SERS substrates that are not only more efficient but also more cost-effective. This progress is crucial for the multifunctionalization of SERS substrates and for their successful implementation in real-world applications.

Plasmonic MOF for Highly Selective SERS Sensing of Trace Mercury (II) in Complex Matrices

Developing Ag-based surface-enhanced Raman spectroscopy (SERS) sensors for detecting Hg(II) has garnered significant research interest due to their unparalleled selectivity, which is brought by the specific Ag-Hg amalgamation reaction. However, existing sensors perform unsatisfactorily in the trace detection of Hg(II) because the low concentration of Hg(II) does not have the redox potential sufficient to amalgamate with Ag. To address this challenge, a plasmonic MOF SERS sensor is developed, nanoetched Ag@UiO-68-SMe, by integrating the enormous Raman enhancement effects of nanoetched Ag with the selective enrichment function of UiO-68-SMe into single entity. This sensor enables on-site readout of Hg(II) in various real-world samples with high selectivity and sensitivity (0.17 ppb) using a portable Raman spectrometer coupled with a homemade 3D print holder. Mechanistic studies reveal that the UiO-68-SMe selectively captures and concentrates trace amounts of Hg(II) through thiomethyl groups, significantly increasing their redox potential. The resultant higher oxidative capacity allows for the spontaneous Ag-Hg amalgamation, inducing a SERS turn-off response to Hg(II), which is otherwise thermodynamically prohibited. This work not only reports a powerful SERS sensor for monitoring trace levels of Hg(II) pollution but also offers a proof-of-concept demonstration of utilizing the enrichment capabilities of MOF to manipulate redox reaction.

Sensing the Future-Frontiers in Biosensors: Exploring Classifications, Principles, and Recent Advances

Biosensors are transforming healthcare by delivering swift, precise, and economical diagnostic solutions. These analytical instruments combine biological indicators with physical transducers to identify and quantify biomarkers, thereby improving illness detection, management, and patient surveillance. Biosensors are widely utilized in healthcare for the diagnosis of chronic and infectious diseases, tailored treatment, and real-time health monitoring. This thorough overview examines several categories of biosensors and their uses in the detection of numerous biomarkers, including glucose, proteins, nucleic acids, and infections. Biosensors are commonly classified based on the type of transducer employed or the specific biorecognition element utilized. This review introduces a novel classification based on substrate morphology, offering a comprehensive perspective on biosensor categorization. Considerable emphasis is placed on the advancement of point-of-care biosensors, facilitating decentralized diagnostics and alleviating the strain on centralized healthcare systems. Recent advancements in nanotechnology have significantly improved the sensitivity, selectivity, and downsizing of biosensors, rendering them more efficient and accessible. The study examines problems such as stability, reproducibility, and regulatory approval that must be addressed to enable the widespread implementation of biosensors in clinical environments. The study examines the amalgamation of biosensors with wearable devices and smartphones, emphasizing the prospects for ongoing health surveillance and individualized medical care. This viewpoint clarifies the distinct types of biosensors and their particular roles, together with recent developments in the "smart biosensor" sector, facilitated by artificial intelligence and the Internet of Medical Things (IoMT). This novel approach seeks to deliver a comprehensive evaluation of the present condition of biosensor technology in healthcare, recent developments, and prospective paths, emphasizing their significance in influencing the future of medical diagnostics and patient care.

Exploring Plasmonic Standalone Surface-Enhanced Raman Scattering Nanoprobes for Multifaceted Applications in Biomedical, Food, and Environmental Fields

Surface-enhanced Raman scattering (SERS) is an innovative spectroscopic technique that amplifies the Raman signals of molecules adsorbed on rough metal surfaces, making it pivotal for single-molecule detection in complex biological and environmental matrices. This review aims to elucidate the design strategies and recent advancements in the application of standalone SERS nanoprobes, with a special focus on quantifiable SERS tags. We conducted a comprehensive analysis of the recent literature, focusing on the development of SERS nanoprobes that employ novel nanostructuring techniques to enhance signal reliability and quantification. Standalone SERS nanoprobes exhibit significant enhancements in sensitivity and specificity due to optimized hot spot generation and improved reporter molecule interactions. Recent innovations include the development of nanogap and core-satellite structures that enhance electromagnetic fields, which are crucial for SERS applications. Standalone SERS nanoprobes, particularly those utilizing indirect detection mechanisms, represent a significant advancement in the field. They hold potential for wide-ranging applications, from disease diagnostics to environmental monitoring, owing to their enhanced sensitivity and ability to operate under complex sample conditions.

Applications of Metal-Organic Frameworks (MOFs) in Drug Delivery, Biosensing, and Therapy: A Comprehensive Review

The porous materials known as metal-organic frameworks (MOFs) stand out for their enormous surface area, adaptable pore size and shape, and structural variety. These characteristics make them well-suited for various applications, especially in healthcare. This review thoroughly summarizes recent studies on the use of MOFs in drug delivery, biosensing, and therapeutics. MOFs may encapsulate medications, target certain cells or tissues, and regulate their release over time. Additionally, MOFs have the potential to be used in biosensing applications, allowing for the selective detection of chemical and biological substances. MOFs' optical or electrical characteristics may be modified to make biosensors that track physiological data. MOFs show potential for targeted drug delivery and the regulated release of therapeutic substances in cancer treatment. In addition, they may work as potent antibacterial agents, providing a less dangerous option than traditional antibiotics that increase antibiotic resistance. For practical applications, further research is required as well as more consideration for the problems with toxicity and biocompatibility. In addition to addressing the difficulties and promising possibilities in this area, this study intends to provide insights into the potential of MOFs in healthcare for drug delivery, biosensing, and treatment. Despite several essential reviews in this area, it was necessary to look into the most recent research on drug delivery, biosensing, and therapy as a combined concept.

Development and Biomedical Application of Non-Noble Metal Nanomaterials in SERS

Surface-enhanced Raman scattering (SERS) is vital in many fields because of its high sensitivity, fast response, and fingerprint effect. The surface-enhanced Raman mechanisms are generally electromagnetic enhancement (EM), which is mainly based on noble metals (Au, Ag, etc.), and chemical enhancement (CM). With more and more studies on CM mechanism in recent years, non-noble metal nanomaterial SERS substrates gradually became widely researched and applied due to their superior economy, stability, selectivity, and biocompatibility compared to noble metal. In addition, non-noble metal substrates also provide an ideal new platform for SERS technology to probe the mechanism of biomolecules. In this paper, we review the applications of non-noble metal nanomaterials in SERS detection for biomedical engineering in recent years. Firstly, we introduce the development of some more common non-noble metal SERS substrates and discuss their properties and enhancement mechanisms. Subsequently, we focus on the progress of the application of SERS detection of non-noble metal nanomaterials, such as analysis of biomarkers and the detection of some contaminants. Finally, we look forward to the future research process of non-noble metal substrate nanomaterials for biomedicine, which may draw more attention to the biosensor applications of non-noble metal nanomaterial-based SERS substrates.

Introduction and Development of Surface-Enhanced Raman Scattering (SERS) Substrates: A Review

Since its discovery, the phenomenon of Surface Enhanced Raman Scattering (SERS) has gradually become an important tool for analyzing the composition and structure of substances. As a trace technique that can efficiently and nondestructively detect single molecules, the application of SERS has expanded from environmental and materials science to biomedical fields. In the past decade or so, the explosive development of nanotechnology and nanomaterials has further boosted the research of SERS technology, as nanomaterial-based SERS substrates have shown good signal enhancement properties. So far, it is widely recognized that the morphology, size, composition, and stacking mode of nanomaterials have a very great influence on the strength of the substrate SERS effect. Herein, an overview of methods for the preparation of surface-enhanced Raman scattering (SERS) substrates is provided. Specifically, this review describes a variety of common SERS substrate preparation methods and explores the potential and promise of these methods for applications in chemical analysis and biomedical fields. By detailing the influence of different nanomaterials (e.g., metallic nanoparticles, nanowires, and nanostars) and their structural features on the SERS effect, this article aims to provide a comprehensive understanding of SERS substrate preparation techniques.

Molecular-Sieving Label-Free Surface-Enhanced Raman Spectroscopy for Sensitive Detection of Trace Small-Molecule Biomarkers in Clinical Samples

Small-molecule biomarkers are ubiquitous in biological fluids with pathological implications, but major challenges persist in their quantitative analysis directly in complex clinical samples. Herein, a molecular-sieving label-free surface-enhanced Raman spectroscopy (SERS) biosensor is reported for selective quantitative analysis of trace small-molecule trimetazidine (TMZ) in clinical samples. Our biosensor is fabricated by decorating a superhydrophobic monolayer of microporous metal-organic frameworks (MOF) shell-coated Au nanostar nanoparticles on a silicon substrate. The design strategy principally combines the hydrophobic surface-enabled physical confinement and preconcentration, MOF-assisted molecular enrichment and sieving of small molecules, and sensitive SERS detection. Our biosensor utilizes such a "molecular confinement-and-sieving" strategy to achieve a five orders-of-magnitude dynamic detection range and a limit of detection of ≈0.5 nM for TMZ detection in either urine or whole blood. We further demonstrate the applicability of our biosensing platform for longitudinal label-free SERS detection of the TMZ level directly in clinical samples in a mouse model.

Patterned Gold Nanoparticle Superlattice Film for Wearable Sweat Sensors

Nanoparticle superlattices are beneficial in terms of providing strong and uniform signals in analysis owing to their closely packed uniform structures. However, nanoparticle superlattices are prone to cracking during physical activities because of stress concentrations, which hinders their detection performance and limits their analytical applications. In this work, template printing methods were used in this study to prepare a patterned gold nanoparticle (AuNP) superlattice film. By adjustment of the size of the AuNP superlattice domain below the critical size of fracture, the mechanical stability of the AuNP superlattice domain is improved. Thus, long-term sustainable high-performance signal output is achieved. The patterned AuNP superlattice film was used to construct a wearable sweat sensor based on surface-enhanced Raman scattering (SERS). The designed sensor showed promise for long-term reliable use in actual scenarios in terms of recommending water replenishment, monitoring hydration states, and tracking the intensity of activity.

Multifunctional metal-organic framework-enhanced sodium alginate-based intelligent indicator: Mechanism and application for freshness monitoring

Intelligent food packaging has recently gained significant attention due to the heightened consumer awareness regarding food quality. Although anthocyanins avoid safety issues, the instability and leakage of anthocyanins restrict their utilization in freshness indicator labels. In this study, we introduced an innovative metal-organic framework (UiO-66-NH2) synergistic pH-colorimetric label with fast ammonia-responsive, incorporating sodium alginate, red cabbage anthocyanin, and UiO-66-NH2. The cross-linked sodium alginate substrate enabled the label to possess superior insolubility. The microscopic morphology of the labels was intricately analyzed, while their sensitivity was rigorously tested utilizing ammonia as a representative gas. Due to the remarkable UV absorption capability of UiO-66-NH2 and various molecular interactions with anthocyanins, the label exhibited good UV absorption, enhanced stability, and optimized performance in reducing anthocyanin leakage, ensuring the stability and effectiveness of the labels in practical applications. The prepared label exhibited good specificity for volatile amines and ammonia gases, and robust anti-interference properties, enabling visualization and early detection of shrimp spoilage during storage at different temperatures. The strategy employed in this study presents promising new possibilities for developing intelligent packaging solutions for food products.

Yolk-Shell Hierarchical Pore Au@MOF Nanostructures: Efficient Gas Capture and Enrichment for Advanced Breath Analysis

Surface-enhanced Raman scattering (SERS) offers a promising, cost-effective alternative for the rapid, sensitive, and quantitative analysis of potential biomarkers in exhaled gases, which is crucial for early disease diagnosis. However, a major challenge in SERS is the effective detection of gaseous analytes, primarily due to difficulties in enriching and capturing them within the substrate's "hotspot" regions. This study introduces an advanced gas sensor combining mesoporous gold (MesoAu) and metal-organic frameworks (MOFs), exhibiting high sensitivity and rapid detection capabilities. The MesoAu provides abundant active sites and interconnected mesopores, facilitating the diffusion of analytes for detection. A ZIF-8 shell enveloping MesoAu further enriches target molecules, significantly enhancing sensitivity. A proof-of-concept experiment demonstrated a detection limit of 0.32 ppb for gaseous benzaldehyde, indicating promising prospects for the rapid diagnosis of early stage lung cancer. This research also pioneers a novel approach for constructing hierarchical plasmonic nanostructures with immense potential in gas sensing.

Effective strategies to enhance the diagnosis and treatment of RCC: The application of biocompatible materials

Renal cell carcinoma (RCC) is recognized as one of the three primary malignant tumors affecting the urinary system, posing a significant risk to human health and life. Despite advancements in understanding RCC, challenges persist in its diagnosis and treatment, particularly in early detection and diagnosis due to issues of low specificity and sensitivity. Consequently, there is an urgent need for the development of effective strategies to enhance diagnostic accuracy and treatment outcomes for RCC. In recent years, with the extensive research on materials for applications in the biomedical field, some materials have been identified as promising for clinical applications, e.g., in the diagnosis and treatment of many tumors, including RCC. Herein, we summarize the latest materials that are being studied and have been applied in the early diagnosis and treatment of RCC. While focusing on their adjuvant effects, we also discuss their technical principles and safety, thus highlighting the value and potential of their application. In addition, we also discuss the limitations of the application of these materials and possible future directions, providing new insights for improving RCC diagnosis and treatment.

Metal-Organic Frameworks in Surface Enhanced Raman Spectroscopy-Based Analysis of Volatile Organic Compounds

Volatile Organic Compounds (VOC) are a major class of environmental pollutants hazardous to human health, but also highly relevant in other fields including early disease diagnostics and organoleptic perception of aliments. Therefore, accurate analysis of VOC is essential, and a need for new analytical methods is witnessed for rapid on-site detection without complex sample preparation. Surface-Enhanced Raman Spectroscopy (SERS) offers a rapidly developing versatile analytical platform for the portable detection of chemical species. Nonetheless, the need for efficient docking of target analytes at the metallic surface significantly narrows the applicability of SERS. This limitation can be circumvented by interfacing the sensor surface with Metal-Organic Frameworks (MOF). These materials featuring chemical and structural versatility can efficiently pre-concentrate low molecular weight species such as VOC through their ordered porous structure. This review presents recent trends in the development of MOF-based SERS substrates with a focus on elucidating respective design rules for maximizing analytical performance. An overview of the status of the detection of harmful VOC is discussed in the context of industrial and environmental monitoring. In addition, a survey of the analysis of VOC biomarkers for medical diagnosis and emerging applications in aroma and flavor profiling is included.

Prospects, advances and biological applications of MOF-based platform for the treatment of lung cancer

Nowadays in our society, lung cancer is exhibiting a high mortality rate and threat to human health. Conventional diagnostic techniques used in the field of lung cancer often necessitate the use of extensive instrumentation, exhibit a tendency for false positives, and are not suitable for widespread early screening purposes. Conventional approaches to treat lung cancer primarily involve surgery, chemotherapy, and radiotherapy. However, these broad-spectrum treatments suffer from drawbacks such as imprecise targeting and significant side effects, which restrict their widespread use. Metal-organic frameworks (MOFs) have attracted significant attention in the diagnosis and treatment of lung cancer owing to their tunable electronic properties and structures and potential applications. These porous nanomaterials are formed through the intricate assembly of metal centers and organic ligands, resulting in highly versatile frameworks. Compared to traditional diagnostic and therapeutic modalities, MOFs can improve the sensitivity of lung cancer biomarker detection in the diagnosis of lung cancer. In terms of treatment, they can significantly reduce side effects and improve therapeutic efficacy. Hence, this perspective provides an overview concerning the advancements made in the field of MOFs as potent biosensors for lung cancer biomarkers. It also delves into the latest research dealing with the use of MOFs as carriers for drug delivery. Additionally, it explores the applications of MOFs in various therapeutic approaches, including chemodynamic therapy, photodynamic therapy, photothermal therapy, and immunotherapy. Furthermore, this review comprehensively analyses potential applications of MOFs as biosensors in the field of lung cancer diagnosis and combines different therapeutic approaches aiming for enhanced therapeutic efficacy. It also presents a concise overview of the existing obstacles, aiming to pave the way for future advancements in lung cancer diagnosis and treatment.

A Dual-Function AgNW@COF SERS Membrane for Organic Pollutant Removal and Simultaneous Concentration Determination

Surface enhanced Raman spectroscopy (SERS) is a highly sensitive analytical detection method commonly employed in biochemical and environmental analysis. Nevertheless, the rapid movement of analytes and interfering components in flow systems can impact the real-time, online detection capability of Raman spectroscopy. To address this issue, we developed an innovative approach utilizing covalent organic framework (COF), a robust porous material with excellent water stability, to coat the surface of Ag nanowire (AgNW) for synthesizing AgNW@COF hybrid. The regular pores of the COF serve to effectively eliminate large interfering molecules while facilitating the efficient transport of specific analytes to SERS hot spots. Additionally, the fluid flow-induced scouring effect aids in excluding interfering molecules from the surface of AgNW. By incorporating AgNW@COF into a bifunctional filter membrane with simultaneous filtration and sensing capabilities, we had achieved efficient purification of organic pollutants as well as real-time identification of pollutant species and concentration.

Plasmonic trimers designed as SERS-active chemical traps for subtyping of lung tumors

Plasmonic materials can generate strong electromagnetic fields to boost the Raman scattering of surrounding molecules, known as surface-enhanced Raman scattering. However, these electromagnetic fields are heterogeneous, with only molecules located at the 'hotspots', which account for ≈ 1% of the surface area, experiencing efficient enhancement. Herein, we propose patterned plasmonic trimers, consisting of a pair of plasmonic dimers at the bilateral sides and a trap particle positioned in between, to address this challenge. The trimer configuration selectively directs probe molecules to the central traps where 'hotspots' are located through chemical affinity, ensuring a precise spatial overlap between the probes and the location of maximum field enhancement. We investigate the Raman enhancement of the Au@Al2O3-Au-Au@Al2O3 trimers, achieving a detection limit of 10-14 M of 4-methylbenzenethiol, 4-mercaptopyridine, and 4-aminothiophenol. Moreover, single-molecule SERS sensitivity is demonstrated by a bi-analyte method. Benefiting from this sensitivity, our approach is employed for the early detection of lung tumors using fresh tissues. Our findings suggest that this approach is sensitive to adenocarcinoma but not to squamous carcinoma or benign cases, offering insights into the differentiation between lung tumor subtypes.

Dinuclear Tridentate Ru(II) Complex with Strong Near-Infrared Light-Triggered Anticancer Activity

The design of the dinuclear Ru(II) complex (Ru2) with strong near-infrared (NIR) absorption properties has been reported for efficient anticancer phototherapy. Under 700 nm LED light excitation, Ru2 exhibited remarkable synergistic type I/II photosensitization ability and photocatalytic activity toward intracellular biomolecules. Ru2 showed impressive 700 nm light-triggered anticancer activity under normoxia and hypoxia compared with the clinically used photosensitizer Chlorin e6. The mechanistic studies showed that Ru2 induced intracellular redox imbalance and perturbed the energy metabolism and biosynthesis in A549 cancer cells. Overall, this work provides a new strategy for developing efficient metal-based complexes for anticancer phototherapy under NIR light.

Visual and quantitative lateral flow immunoassay based on Au@PS SERS tags for multiplex cardiac biomarkers

Rapid and sensitive detection of multiple biomarkers by lateral flow immunoassay (LFIA) remains challenging for signal amplification for commonly used nanotags. Herein, we report a novel LFIA strip for visual and highly sensitive analysis of two cardiac biomarkers based on functionalized gold nanoparticles @ polystyrene microsphere (Au@PS）microcavity as surface-enhanced Raman scattering (SERS) tags. Antibody-modified Au@PS was designed as a SERS label. The evanescent waves propagating along the surface of the PS microcavity and the localized surface plasmons of the gold nanoparticles were coupled to enhance the light-matter interaction synergistically for Raman signal enhancement. In this strategy, the proposed Au@PS SERS tags-based LFIA was carried out to quantify the content of the heart failure and infarct biomarkers synchronously within 15 min and get the limits of detection of 1 pg/mL and 10 pg/mL for cardiac troponin I (cTnI) and N-terminal natriuretic peptide precursor (NT-proBNP), respectively. The results demonstrated 10-20 folds more sensitivity than that of the standard colloidal gold strip and fluorescent strip for the same biomarkers. This novel quantitative LFIA shows promise as a high-sensitive and visual sensing method for relevant clinical and forensic analysis.

Recent advances in small-angle scattering techniques for MOF colloidal materials

This paper reviews the recent progress of small angle scattering (SAS) techniques, mainly including X-ray small angle scattering technique (SAXS) and neutron small angle scattering (SANS) technique, in the study of metal-organic framework (MOF) colloidal materials (CMOFs). First, we introduce the application research of SAXS technique in pristine MOFs materials, and review the studies on synthesis mechanism of MOF materials, the pore structures and fractal characteristics, as well as the spatial distribution and morphological evolution of foreign molecules in MOF composites and MOF-derived materials. Then, the applications of SANS technique in MOFs are summarized, with emphasis on SANS data processing method, structure modeling and quantitative structural information extraction. Finally, the characteristics and developments of SAS techniques are commented and prospected. It can be found that most studies on MOF materials with SAS techniques focus mainly on nanoporous structure characterization and the evolution of pore structures, or the spatial distribution of other foreign molecules loaded in MOFs. Indeed, SAS techniques take an irreplaceable role in revealing the structure and evolution of nanopores in CMOFs. We expect that this paper will help to understand the research status of SAS techniques on MOF materials and better to apply SAS techniques to conduct further research on MOF and related materials.

Liquid Interfacial Gating of Superhydrophobic Plasmonic Metal-Organic Frameworks for Three-in-One Separation, Enrichment, and Recognition in Bacterial Quorum Sensing

Poor adsorption properties of nonadsorbing targets and competing adsorption of nontargets at a liquid interface always hamper the development of interface sensing techniques. There is a need to fabricate materials that are applicable to various interface assemblies and, meanwhile, could be employed as interfacial gating to improve the performance of interface sensing by separating, enriching, and recognizing targets at the liquid interface. Here, superhydrophobic zeolite imidazole frameworks-8@gold nanoparticles-1H,1H,2H,2H-perfluorodecanethiol (ZIF-8@GNPs-PFDT) with a static water contact angle (WCA) of 155° was constructed via electrostatic self-assembly and surface graft modification. The plasmonic metal-organic framework (PMOF) nanohybrid realized all-purpose self-assembly at air/liquid and liquid/liquid interfaces and also facilely assembled on the surface of liquid droplets, hydrogels, and foams. The self-assembled porous materials displayed the capability for separating, enriching, and recognizing analytes at various oil/water interfaces and thus could be used to adsorb nonadsorbing targets and block the competing adsorption of nontargets. The self-assembled ZIF-8@GNPs-PFDT structures were employed as a three-in-one interfacial gating to endow the excellent surface-enhanced Raman scattering (SERS) sensing capability and has become a promising tool for dye molecular analysis, oil/water separation, organic phase identification, and in situ cultivation and monitoring of bacterial quorum sensing (QS).

Acid-Responsive Decomposable Nanomedicine Based on Zeolitic Imidazolate Frameworks for Near-Infrared Fluorescence Imaging/Chemotherapy Combined Tumor Theranostics

Zeolitic imidazolate framework-8 (ZIF-8) nanoparticles (NPs) are gaining traction in tumor theranostics for their effectiveness in encapsulating both imaging agents and therapeutic drugs. While typically, similar hydrophilic molecules are encapsulated in either pure aqueous or organic environments, few studies have explored co-encapsulation of chemotherapeutic drugs and imaging agents with varying hydrophilicity and, consequently, constructed multifunctional ZIF-8 composite NPs for acid-responsive, near-infrared fluorescence imaging/chemotherapy combined tumor theranostics. Here, we present a one-pot method for the synthesis of uniform Cy5.5&DOX@ZIF-8 nanoparticles in mixed solvents, efficiently achieving simultaneous encapsulation of hydrophilic doxorubicin (DOX) and hydrophobic Cyanine-5.5 (Cy5.5). Surface decoration with dextran (Dex) enhanced colloidal stability and biocompatibility. The method significantly facilitated co-loading of Cy5.5 dyes and DOX drugs, endowing the composite NPs with notable fluorescent imaging capabilities and pH-responsive chemotherapy capacities. In vivo near-infrared fluorescence (NIRF) imaging in A549 tumor-bearing mice demonstrated significant accumulation of Cy5.5 at tumor sites due to enhanced permeability and retention (EPR) effects, with fluorescence intensities approximately 48-fold higher than free Cy5.5. Enhanced therapeutic efficiency was observed in composite NPs compared to free DOX, validating tumor-targeted capability. These findings suggest ZIF-8-based nanomedicines as promising platforms for multifunctional tumor theranostics.

Hierarchical PVDF/ZnO/Ag/ZIF-8 nanofiber membrane used in trace-level Raman detection of H2S

surface enhanced Raman scattering (SERS) detection of gases has always been difficult due to the low affinity and poor Raman cross section of the moving molecules. To mitigate the impact of these problems on detection of gases, a structure of zinc oxide/silver nanowires coated with zeolitic imidazolate framework-8 (ZnO NWs/Ag/ZIF-8) was constructed on polyvinylidene fluoride (PVDF) nanofiber membrane (PVDF/ZnO NWs/Ag/ZIF-8) and in detail researched in this work. Benefitting from the quadruple synergistic effect of efficient Knudsen diffusion of gas molecules inside ZIF-8, enrichment of ZIF-8 microsponges for gaseous molecules, regulation of ZIF-8 dielectric layer for light and reverse light scattering of ZnO NW/Ag tip, the structure was proven to have precise co-confinement on both hot spots and gaseous molecules. As a result, this PVDF/ZnO NWs/Ag/ZIF-8 achieved excellent detection for hydrogen sulfide (H2S), with a limit of detection of 1 × 10-10 v/v and the minimum relative standard deviation value of ca. 7.13 %. Furthermore, as a proof of concept, in practical application, we designed and assembled our substrate (3.5 cm × 3.5 cm) into a SERS face mask and realized efficient monitoring of H2S in human's exhaled breath.

SERS-based AI diagnosis of lung and gastric cancer via exhaled breath

Distinct diagnosis between Lung cancer (LC) and gastric cancer (GC) according to the same biomarkers (e.g. aldehydes) in exhaled breath based on surface-enhanced Raman spectroscopy (SERS) remains a challenge in current studies. Here, an accurate diagnosis of LC and GC is demonstrated, using artificial intelligence technologies (AI) based on SERS spectrum of exhaled breath in plasmonic metal organic frameworks nanoparticle (PMN) film. In the PMN film with optimal structure parameters, 1780 SERS spectra are collected, in which 940 spectra come from healthy people (n = 49), another 440 come from LC patients (n = 22) and the rest 400 come from GC patients (n = 8). The SERS spectra are trained through artificial neural network (ANN) model with the deep learning (DL) algorithm, and the result exhibits a good identification accuracy of LC and GC with an accuracy over 89 %. Furthermore, combined with information of SERS peaks, the data mining in ANN model is successfully employed to explore the subtle compositional difference in exhaled breath from healthy people (H) and L/GC patients. This work achieves excellent noninvasive diagnosis of multiple cancer diseases in breath analysis and provides a new avenue to explore the feature of disease based on SERS spectrum.

Surface-Enhanced Raman Spectroscopy: Current Understanding, Challenges, and Opportunities

While surface-enhanced Raman spectroscopy (SERS) has experienced substantial advancements since its discovery in the 1970s, it is an opportunity to celebrate achievements, consider ongoing endeavors, and anticipate the future trajectory of SERS. In this perspective, we encapsulate the latest breakthroughs in comprehending the electromagnetic enhancement mechanisms of SERS, and revisit CT mechanisms of semiconductors. We then summarize the strategies to improve sensitivity, selectivity, and reliability. After addressing experimental advancements, we comprehensively survey the progress on spectrum-structure correlation of SERS showcasing their important role in promoting SERS development. Finally, we anticipate forthcoming directions and opportunities, especially in deepening our insights into chemical or biological processes and establishing a clear spectrum-structure correlation.

Hybrid plasmonic aerogel with tunable hierarchical pores for size-selective multiplexed detection of VOCs with ultrahigh sensitivity

Sensitive and rapid identification of volatile organic compounds (VOCs) at ppm level with complex composition is vital in various fields ranging from respiratory diagnosis to environmental safety. Herein, we demonstrate a SERS gas sensor with size-selective and multiplexed identification capabilities for VOCs by executing the pre-enrichment strategy. In particular, the macro-mesoporous structure of graphene aerogel and micropores of metal-organic frameworks (MOFs) significantly improved the enrichment capacity (1.68 mmol/g for toluene) of various VOCs near the plasmonic hotspots. On the other hand, molecular MOFs-based filters with different pore sizes could be realized by adjusting the ligands to exclude undesired interfering molecules in various detection environments. Combining these merits, graphene/AuNPs@ZIF-8 aerogel gas sensor exhibited outstanding label-free sensitivity (up to 0.1 ppm toluene) and high stability (RSD=14.8%, after 45 days storage at room temperature for 10 cycles) and allowed simultaneous identification of multiple VOCs in a single SERS measurement with high accuracy (error < 7.2%). We visualize that this work will tackle the dilemma between sensitivity and detection efficiency of gas sensors and will inspire the design of next-generation SERS technology for selective and multiplexed detection of VOCs.

Metal-Organic Framework-Enabled Trapping of Volatile Organic Compounds into Plasmonic Nanogaps for Surface-Enhanced Raman Scattering Detection

Utilizing electromagnetic hotspots within plasmonic nanogaps is a promising approach to create ultrasensitive surface-enhanced Raman scattering (SERS) substrates. However, it is difficult for many molecules to get positioned in such nanogaps. Metal-organic frameworks (MOFs) are commonly used to absorb and concentrate diverse molecules. Herein, we combine these two strategies by introducing MOFs into plasmon-coupled nanogaps, which has so far remained experimentally challenging. Ultrasensitive SERS substrates are fabricated through the construction of nanoparticle-on-mirror structures, where Au nanocrystals are encapsulated with a zeolitic imidazolate framework-8 (ZIF-8) shell and then coupled to a gold film. The ZIF-8 shell, as a spacer that separates the Au nanocrystal and the Au film, can be adjusted in thickness over a wide range, which allows the electric field enhancement and plasmon resonance wavelength to be varied. By trapping Raman-active molecules within the ZIF-8 shell, we show that our plasmon-coupled structures exhibit a superior SERS detection performance. A range of volatile organic compounds at the concentrations of 10-2 mg m-3 can be detected sensitively and reliably. Our study therefore offers an attractive route for synergistically combining plasmonic electric field enhancement and MOF-enabled molecular enrichment to design and create SERS substrates for ultrasensitive detection.

Ratiometric SERS quantification of SO2 vapor based on Au@Ag-Au with Raman reporter as internal standard

Practical gas sensing application requires sensors to quantify target analytes with high sensitivity and reproducibility. However, conventional surface enhanced Raman scattering (SERS) sensor lacks reproducibility and quantification arising from variations of "hot spot" distribution and measurement conditions. Here, a ratio-dependent SERS sensor was developed for quantitative label-free gas sensing. Au@Ag-Au nanoparticles (NPs) were filtered onto anodic aluminum oxide (AAO) forming Au@Ag-Au@AAO SERS substrate. 4-MBA was encapsulated in the gap of Au@Ag-Au and served as the internal standard (IS) to calibrate SERS signal fluctuation for improved quantification ability. Combined with headspace sampling method, SO2 residue in traditional Chinese medicine (TCM) can be extracted and captured on the immediate vicinity of Au@Ag-Au surface. The intensity ratio I613 cm-1/I1078 cm-1 showed excellent linearity within the range of 0.5 mg/kg-500 mg/kg, demonstrating superior quantification performance for SO2 detection. Signals for concentration as low as 0.05 mg/kg of SO2 could be effectively collected, much lower than the strictest limit 10 mg/kg in Chinese Pharmacopoeia. Combined with a handheld Raman spectrometer, handy and quantitative TCM quality evaluation in aspect of SO2 residue was realized. This ratiometric SERS sensor functioned well in rapid on-site SO2 quantification, exhibiting excellent sensitivity and simple operability.

Construction of smartphone-adapted signal visualization platform for dual-mode detection of H2S based on integrated metal-organic framework nanoprobes

Hydrogen sulfide (H2S) is a toxic contaminant and has great influence on many physiological processes. Due to various pathophysiological roles and environmental pollution problems, it is necessary to construct and develop simple and portable monitoring sensors for the precise detection of H2S. Herein, we developed a smartphone-adapted dual-mode detection platform by integrating the colorimetric and photothermal imaging analysis into a metal-organic framework-based chip (ZIF-8/Cu). Due to the nanoconfinement effect of ZIF-8, small-sized plasmonic CuS could be in-situ formed during the detection procedure of H2S and endowed the chips with excellent photothermal properties. By constructing a smartphone-adapted photothermal imager, the metal-organic framework-based chip could achieve a portable photothermal imaging analysis of H2S. Moreover, as the formed CuS was a good peroxidase-like nanozyme, the chips could also be used to trigger the enzymic catalytic reaction toward the chromogenic reaction of 3,3',5,5'-tetramethylbenzidine (TMB)-H2O2, thus providing another colorimetric sensing mode by using a smartphone App. In this smartphone-adapted visualization platform, the portable chemosensors could simultaneously achieve double detection modes at one electrode, which provided a new pathway for the accurate detection of H2S and circumvented the false-positive or negative errors during the detection process. Besides, by using the finite difference time domain (FDTD) simulation method, the in-depth mechanism, including the plasmonic effect and spatial electromagnetic field distribution, was explored to provide a possible reason for the excellent sensing performance of the dual-mode visualization platform. This work provides a new insight into the construction of the accurate, portable and smart sensing platform in the visual screening of H2S.

SERS sensing for cancer biomarker: Approaches and directions

These days, cancer is thought to be more than just one illness, with several complex subtypes that require different screening approaches. These subtypes can be distinguished by the distinct markings left by metabolites, proteins, miRNA, and DNA. Personalized illness management may be possible if cancer is categorized according to its biomarkers. In order to stop cancer from spreading and posing a significant risk to patient survival, early detection and prompt treatment are essential. Traditional cancer screening techniques are tedious, time-consuming, and require expert personnel for analysis. This has led scientists to reevaluate screening methodologies and make use of emerging technologies to achieve better results. Using time and money saving techniques, these methodologies integrate the procedures from sample preparation to detection in small devices with high accuracy and sensitivity. With its proven potential for biomedical use, surface-enhanced Raman scattering (SERS) has been widely used in biosensing applications, particularly in biomarker identification. Consideration was given especially to the potential of SERS as a portable clinical diagnostic tool. The approaches to SERS-based sensing technologies for both invasive and non-invasive samples are reviewed in this article, along with sample preparation techniques and obstacles. Aside from these significant constraints in the detection approach and techniques, the review also takes into account the complexity of biological fluids, the availability of biomarkers, and their sensitivity and selectivity, which are generally lowered. Massive ways to maintain sensing capabilities in clinical samples are being developed recently to get over this restriction. SERS is known to be a reliable diagnostic method for treatment judgments. Nonetheless, there is still room for advancement in terms of portability, creation of diagnostic apps, and interdisciplinary AI-based applications. Therefore, we will outline the current state of technological maturity for SERS-based cancer biomarker detection in this article. The review will meet the demand for reviewing various sample types (invasive and non-invasive) of cancer biomarkers and their detection using SERS. It will also shed light on the growing body of research on portable methods for clinical application and quick cancer detection.