Functionalized h‐BN Nanosheets as a Theranostic Platform for SERS Real‐Time Monitoring of MicroRNA and Photodynamic Therapy

CuPc-Fe@BSA nanocomposite: Intracellular acid-sensitive aggregation for enhanced sonodynamic and chemo-therapy

Due to their rigid π-conjugated macrocyclic structure, organic sonosensitizers face significant aggregation in physiological conditions, hindering the production of reactive oxygen species (ROS). An acid-sensitive nanoassembly was developed to address this issue and enhance sonodynamic therapy (SDT) and emission. Initially, copper phthalocyanine (CuPc) was activated using a H2SO4-assisted hydrothermal method to introduce multiple functional groups (-COOH, -OH, and -SO3H), disrupting strong π-π stacking and promoting ROS generation and emission. Subsequently, negatively charged CuPc-SO4 was incorporated into bovine serum albumin (BSA) to form CuPc-Fe@BSA nanoparticles (10 nm) with Fe3+ ions serving as linkers. In acidic conditions, protonation of CuPc-SO4 and BSA weakened the interactions, leading to Fe3+ release and nanostructure dissociation. Protonated CuPc-SO4 tended to self-aggregate into nanorods. This acidity-sensitive aggregation is vital for achieving specific accumulation within the tumor microenvironment (TME), thereby enhancing retention and SDT efficacy. Prior to this, the nanocomposites demonstrated cycling stability under neutral conditions. Additionally, the released Fe ions exhibited mimicry of glutathione peroxidase and peroxidase activity for chemotherapy (CDT). The synergistic effect of SDT and CDT increased intracellular oxidative stress, causing mitochondrial injury and ferroptosis. Furthermore, the combined therapy induced immunogenic cell death (ICD), effectively activating anticancer immune responses and suppressing metastasis and recurrence.

Biomedical Utility of Non-Enzymatic DNA Amplification Reaction: From Material Design to Diagnosis and Treatment

Nucleic acid nanotechnology has become a promising strategy for disease diagnosis and treatment, owing to remarkable programmability, precision, and biocompatibility. However, current biosensing and biotherapy approaches by nucleic acids exhibit limitations in sensitivity, specificity, versatility, and real-time monitoring. DNA amplification reactions present an advantageous strategy to enhance the performance of biosensing and biotherapy platforms. Non-enzymatic DNA amplification reaction (NEDAR), such as hybridization chain reaction and catalytic hairpin assembly, operate via strand displacement. NEDAR presents distinct advantages over traditional enzymatic DNA amplification reactions, including simplified procedures, milder reaction conditions, higher specificity, enhanced controllability, and excellent versatility. Consequently, research focusing on NEDAR-based biosensing and biotherapy has garnered significant attention. NEDAR demonstrates high efficacy in detecting multiple types of biomarkers, including nucleic acids, small molecules, and proteins, with high sensitivity and specificity, enabling the parallel detection of multiple targets. Besides, NEDAR can strengthen drug therapy, cellular behavior control, and cell encapsulation. Moreover, NEDAR holds promise for constructing assembled diagnosis-treatment nanoplatforms in the forms of pure DNA nanostructures and hybrid nanomaterials, which offer utility in disease monitoring and precise treatment. Thus, this paper aims to comprehensively elucidate the reaction mechanism of NEDAR and review the substantial advancements in NEDAR-based diagnosis and treatment over the past five years, encompassing NEDAR-based design strategies, applications, and prospects.

Phase-Tunable Molybdenum Boride Ceramics as an Emerging Sensitive and Reliable SERS Platform in Harsh Environments

Traditional surface-enhanced Raman scattering (SERS) sensors rely heavily on the use of plasmonic noble metals, which have limitations due to their high cost and lack of physical and chemical stability. Hence, it is imperative to explore new materials as SERS platforms that can withstand high temperatures and harsh conditions. In this study, the SERS effect of molybdenum boride ceramic powders is presented with an enhancement factor of 5 orders, which is comparable to conventional noble metal substrates. The molybdenum boride powders synthesized through liquid-phase precursor and carbothermal reduction have β-MoB, MoB2, and Mo2B5 phases. Among these phases, β-MoB demonstrates the most significant SERS activity, with a detection limit for rhodamine 6G (R6G) molecules of 10-9 m. The impressive SERS enhancement can be attributed to strong molecule interactions and prominent charge interactions between R6G and the various phases of molybdenum boride, as supported by theoretical calculations. Additionally, Raman measurements show that the SERS activity remains intact after exposure to high temperature, strong acids, and alkalis. This research introduces a novel molybdenum boride all-ceramic SERS platform capable of functioning in harsh conditions, thereby showing the promising of boride ultrahigh-temperature ceramics for detection applications in extreme environments.

Construction of Multiply Guaranteed DNA Sensors for Biological Sensing and Bioimaging Applications

Nucleic acids exhibit exceptional functionalities for both molecular recognition and catalysis, along with the capability of predictable assembly through strand displacement reactions. The inherent programmability and addressability of DNA probes enable their precise, on-demand assembly and accurate execution of hybridization, significantly enhancing target detection capabilities. Decades of research in DNA nanotechnology have led to advances in the structural design of functional DNA probes, resulting in increasingly sensitive and robust DNA sensors. Moreover, increasing attention has been devoted to enhancing the accuracy and sensitivity of DNA-based biosensors by integrating multiple sensing procedures. In this review, we summarize various strategies aimed at enhancing the accuracy of DNA sensors. These strategies involve multiple guarantee procedures, utilizing dual signal output mechanisms, and implementing sequential regulation methods. Our goal is to provide new insights into the development of more accurate DNA sensors, ultimately facilitating their widespread application in clinical diagnostics and assessment.

Recent progress in Surface-Enhanced Raman Spectroscopy detection of biomarkers in liquid biopsy for breast cancer

Breast cancer is the most commonly diagnosed cancer in women globally and a leading cause of cancer-related mortality. However, current detection methods, such as X-rays, ultrasound, CT scans, MRI, and mammography, have their limitations. Recently, with the advancements in precision medicine and technologies like artificial intelligence, liquid biopsy, specifically utilizing Surface-Enhanced Raman Spectroscopy (SERS), has emerged as a promising approach to detect breast cancer. Liquid biopsy, as a minimally invasive technique, can provide a temporal reflection of breast cancer occurrence and progression, along with a spatial representation of overall tumor information. SERS has been extensively employed for biomarker detection, owing to its numerous advantages such as high sensitivity, minimal sample requirements, strong multi-detection ability, and controllable background interference. This paper presents a comprehensive review of the latest research on the application of SERS in the detection of breast cancer biomarkers, including exosomes, circulating tumor cells (CTCs), miRNA, proteins and others. The aim of this review is to provide valuable insights into the potential of SERS technology for early breast cancer diagnosis.

Surface-Enhanced Raman Scattering Using 2D Materials

The use of surface-enhanced Raman scattering (SERS) as a technique for detecting small amounts of (bio)chemical analytes has become increasingly popular in various fields. While gold and silver nanostructures have been extensively studied as SERS substrates, the availability of other types of substrates is currently expanding the applications of this spectroscopic method. Recently, researchers have begun exploring two-dimensional (2D) materials (e. g., graphene-like nanostructures) as substrates for SERS analysis. These materials offer unique optical properties, a well-defined structure, and the ability to modify their surface chemistry. As a contribution to advance this field, this concept article highlights the significance of understanding the chemical mechanism that underlies the experimental Raman spectra of chemisorbed molecules onto 2D materials' surfaces. Therefore, the article discusses recent advancements in fabricating substrates using 2D layered materials and the synergic effects of using their metallic composites for SERS applications. Additionally, it provides a new perspective on using Raman imaging in developing 2D materials as analytical platforms for Raman spectroscopy, an exciting emerging research area with significant potential.

Exploring and Engineering 2D Transition Metal Dichalcogenides toward Ultimate SERS Performance

Surface-enhanced Raman spectroscopy (SERS) is an ultrasensitive surface analysis technique that is widely used in chemical sensing, bioanalysis, and environmental monitoring. The design of the SERS substrates is crucial for obtaining high-quality SERS signals. Recently, 2D transition metal dichalcogenides (2D TMDs) have emerged as high-performance SERS substrates due to their superior stability, ease of fabrication, biocompatibility, controllable doping, and tunable bandgaps and excitons. In this review, a systematic overview of the latest advancements in 2D TMDs SERS substrates is provided. This review comprehensively summarizes the candidate 2D TMDs SERS materials, elucidates their working principles for SERS, explores the strategies to optimize their SERS performance, and highlights their practical applications. Particularly delved into are the material engineering strategies, including defect engineering, alloy engineering, thickness engineering, and heterojunction engineering. Additionally, the challenges and future prospects associated with the development of 2D TMDs SERS substrates are discussed, outlining potential directions that may lead to significant breakthroughs in practical applications.

Potential of a deep eutectic solvent in silver nanoparticle fabrication for antibiotic residue detection

Deep eutectic solvents (DESs) have recently emerged as an alternative solvent for nanoparticle synthesis. There have been numerous advancements in the fabrication of silver nanoparticles (Ag NPs), but the potential of DESs in Ag NP synthesis was neither considered nor studied carefully. In this study, we present a novel strategy to fabricate Ag NPs in a DES (Ag NPs-DES). The DES composed of ᴅ-glucose, urea, and glycerol does not contain any anions to precipitate with Ag+ cations. Our Ag NPs-DES sample is used in a surface-enhanced Raman scattering (SERS) sensor. The two analytes for SERS quantitation are nitrofurantoin (NFT) and sulfadiazine (SDZ) whose residues can be traced down to 10-8 M. The highest enhancement factors (EFs) are competitive at 6.29 × 107 and 1.69 × 107 for NFT and SDZ, respectively. Besides, the linearity coefficients are extremely close to 1 in the range of 10-8 to 10-3 M of concentration, and the SERS substrate shows remarkable uniformity along with great selectivity. This powerful SERS performance indicates that DESs have tremendous potential in the synthesis of nanomaterials for biosensor substrate construction.

Boron nitride nanoplate-based strand exchange amplification with enhanced sensitivity and rapidity for quantitative detection of Staphylococcus aureus in food samples

Staphylococcus aureus is one of the most common foodborne pathogens that can cause serious food poisoning and infectious diseases in humans. Standard identification approaches include nucleic acid amplification, but current amplification tools suffer from low amplification efficiency, resulting in the risk of low sensitivity and long detection time. Herein, boron nitride nanoplates (BNNPs) were chosen as an additive for enhancing the sensitivity and rapidity of strand exchange amplification (SEA), thereby successfully expanding the application of nucleic acid detection for detecting Staphylococcus aureus in food samples. As a result, SEA based on boron nitride nanoplates (BNNP-SEA) was employed for sensitive and rapid detection of foodborne pathogen Staphylococcus aureus. Compared with classical SEA, the BNNP-based SEA assay was more than 10-fold sensitive, and the detection time was reduced by 15 minutes. The optimized BNNP-based SEA shows a wide linear range from 40 pg to 50 ng in a diluted solution of the target DNA with a low detection limit of 40 pg. Moreover, the BNNP-based SEA achieves the quantitative detection of Staphylococcus aureus in different food samples (pork, beef, mutton, duck, milk and shrimp). In contrast to the classical SEA, the BNNP-based SEA method enabled sensitive and rapid detection of Staphylococcus aureus in the above food samples at concentrations as low as 5 × 103 CFU mL-1. The BNNP-based SEA assay is specific, sensitive and reliable, offering a valuable diagnostic technology for routine analysis in food safety research.

SERS-based methods for the detection of genomic biomarkers of cancer

Genomic biomarkers of cancer are based on changes in nucleic acids, which include abnormal expression levels of some miRNAs, point mutations in DNA sequences, and altered levels of DNA methylation. The presence of tumor-related nucleic acids in body fluids (blood, saliva, or urine) makes it possible to achieve a non-invasive early-stage cancer diagnosis. Currently existing techniques for the discovery of nucleic acids require complex, time-consuming, costly assays and have limited multiplexing abilities. Surface-enhanced Raman spectroscopy (SERS) is a vibrational spectroscopy technique that is able to provide molecular specificity combined with trace sensitivity. SERS has gained research attention as a tool for the detection of nucleic acids because of its promising potential: label-free SERS can decrease the complexity of assays currently used with fluorescence-based detection due to the absence of the label, while labeled SERS may outperform the gold standard in terms of the multiplexing ability. The first papers about SERS-based methods for the measurement of genomic biomarkers were written in 2008, and since then, more than 150 papers have been published. The aim of this paper is to review and evaluate the proposed SERS-based methods in terms of their level of development and their potential for liquid biopsy application, as well as to contribute to their further evolution by attracting research attention to the field. This goal will be reached by grouping, on the basis of their experimental protocol, all the published manuscripts on the topic and evaluating each group in terms of its limit of detection and applicability to real body fluids. Thus, the methods are classified according to their working principles into five main groups, including capture-based, displacement-based, sandwich-based, enzyme-assisted, and specialized protocols.

Spatiotemporally Programmed Disassembly of Multifunctional Integrated DNAzyme Nanoplatfrom for Amplified Intracellular MicroRNA Imaging

The sensing performance of DNAzymes in live cells is tremendously hampered by the inefficient and inhomogeneous delivery of DNAzyme probes and their incontrollable off-site activation, originating from their susceptibility to nuclease digestion. This requires the development of a more compact and robust DNAzyme-delivering system with site-specific DNAzyme activation property. Herein, a highly compact and robust Zn@DDz nanoplatform is constructed by integrating the unimolecular microRNA-responsive DNA-cleaving DNAzyme (DDz) probe with the requisite DNAzyme Zn2+ -ion cofactors, and the amplified intracellular imaging of microRNA via the spatiotemporally programmed disassembly of Zn@DDz nanoparticles is achieved. The multifunctional Zn@DDz nanoplatform is simply composed of a structurally blocked self-hydrolysis DDz probe and the inorganic Zn2+ -ion bridge, with high loading capacity, and can effectively deliver the initially catalytic inert DDz probe and Zn2+ into living cells with enhanced stabilities. Upon their entry into the acidic microenvironment of living cells, the self-sufficient Zn@DDz nanoparticle is disassembled to release DDz probe and simultaneously supply Zn2+ -ion cofactors. Then, endogenous microRNA-21 catalyzes the reconfiguration and activation of DDz for generating the amplified readout signal with multiply guaranteed imaging performance. Thus, this work paves an effective way for promoting DNAzyme-based biosensing systems in living cells, and shows great promise in clinical diagnosis.

Enhancing charge transfer in a W18O49/g-C3N4 heterostructure via band structure engineering for effective SERS detection and flexible substrate applications

Chemical mechanism (CM)-related surface-enhanced Raman spectroscopy (SERS) has received tremendous interest due to its exceptional stability and excellent uniformity. Nevertheless, there remains a demand for ingenious methodologies for promoting effective charge transfer (CT) to improve SERS sensitivity further. Herein, a band structure engineered W18O49/g-C3N4 heterostructure (WCN) was first employed as a CM-based SERS substrate with remarkable enhancement and sensitivity. To investigate the Raman enhancement properties of the substrate, malachite green (MG) was employed as the Raman probe with the excitation of a 633 nm laser. The WCN substrate exhibits a Raman enhancement factor (EF) of 2.6 × 107, achieving a limit of detection (LOD) of 1.9 × 10-10 M for MG. The outstanding Raman amplification behavior can be attributed to the heterojunction-induced efficient CT process, energy band matching resonance due to minor doping with g-C3N4 serving as a band gap modifier, and improved photo-induced charge transfer (PICT) efficiency via the oxygen vacancies in the W18O49 units. Additionally, a flexible SERS substrate based on WCN was constructed using a vacuum filtration method and utilized to detect prohibited pharmaceutical residues on fish skin. The integration of this WCN and a nylon membrane not only preserves the Raman activity of the WCN for sensitive detection but also endows the Raman substrate with high flexibility and good mechanical durability, making it a potential candidate for in situ detection in particular environments.

A versatile MOF-derived theranostic for dual-miRNA controlled accurate cancer cell recognition and photodynamic therapy

Precise detection and monitoring of microRNAs (miRNAs) in living tumor cells is significant for the prompt diagnosis of cancer and provides important information for treatment of cancer. A significant challenge is developing methods for imaging different miRNAs simultaneously to further enhance diagnostic and treatment accuracy. In this work, a versatile MOF-derived theranostic system (DAPM) was constructed using photosensitive metal-organic frameworks (PMOF, PM) and a DNA AND logic gate (DA). The DAPM exhibited excellent biostability and enabled sensitive detection of miR-21 and miR-155, achieving a low limit of detection (LOD) for miR-21 (89.10 pM) and miR-155 (54.02 pM). The DAPM probe generated a fluorescence signal in tumor cells where miR-21 and miR-155 co-existed, demonstrating the enhanced ability of tumor cell recognition. Additionally, the DAPM achieved efficient ROS generation and concentration-dependent cytotoxicity under light irradiation, providing effective photodynamic therapy for anti-tumors. The proposed DAPM theranostic system enables accurate cancer diagnosis, and provides spatial and temporal information for PDT.

Microenvironment Restruction of Emerging 2D Materials and their Roles in Therapeutic and Diagnostic Nano-Bio-Platforms

Engineering advanced therapeutic and diagnostic nano-bio-platforms (NBPFs) have emerged as rapidly-developed pathways against a wide range of challenges in antitumor, antipathogen, tissue regeneration, bioimaging, and biosensing applications. Emerged 2D materials have attracted extensive scientific interest as fundamental building blocks or nanostructures among material scientists, chemists, biologists, and doctors due to their advantageous physicochemical and biological properties. This timely review provides a comprehensive summary of creating advanced NBPFs via emerging 2D materials (2D-NBPFs) with unique insights into the corresponding molecularly restructured microenvironments and biofunctionalities. First, it is focused on an up-to-date overview of the synthetic strategies for designing 2D-NBPFs with a cross-comparison of their advantages and disadvantages. After that, the recent key achievements are summarized in tuning the biofunctionalities of 2D-NBPFs via molecularly programmed microenvironments, including physiological stability, biocompatibility, bio-adhesiveness, specific binding to pathogens, broad-spectrum pathogen inhibitors, stimuli-responsive systems, and enzyme-mimetics. Moreover, the representative therapeutic and diagnostic applications of 2D-NBPFs are also discussed with detailed disclosure of their critical design principles and parameters. Finally, current challenges and future research directions are also discussed. Overall, this review will provide cutting-edge and multidisciplinary guidance for accelerating future developments and therapeutic/diagnostic applications of 2D-NBPFs.

Advances in drug delivery systems, challenges and future directions

Advances in molecular pharmacology and an improved understanding of the mechanism of most diseases have created the need to specifically target the cells involved in the initiation and progression of diseases. This is especially true for most life-threatening diseases requiring therapeutic agents which have numerous side effects, thus requiring accurate tissue targeting to minimize systemic exposure. Recent drug delivery systems (DDS) are formulated using advanced technology to accelerate systemic drug delivery to the specific target site, maximizing therapeutic efficacy and minimizing off-target accumulation in the body. As a result, they play an important role in disease management and treatment. Recent DDS offer greater advantages when compared to conventional drug delivery systems due to their enhanced performance, automation, precision, and efficacy. They are made of nanomaterials or miniaturized devices with multifunctional components that are biocompatible, biodegradable, and have high viscoelasticity with an extended circulating half-life. This review, therefore, provides a comprehensive insight into the history and technological advancement of drug delivery systems. It updates the most recent drug delivery systems, their therapeutic applications, challenges associated with their use, and future directions for improved performance and use.

Orthometric multicolor encoded hybridization chain reaction amplifiers for multiplexed microRNA profiling in living cells

Multiplexed microRNA (miRNA) profiling of more than four types in living cells is challenging due to fluorescent spectral overlap, representing a significant limitation in studying the complex interactions related to the occurrence and development of diseases. Herein, we report a multiplexed fluorescent imaging strategy based on an orthometric multicolor encoded hybridization chain reaction amplifier named multi-HCR. The targeting miRNA can trigger this multi-HCR strategy due to the specific sequence recognition, and then its self-assembly to amplify the programmability signals. We take the four-colored chain amplifiers, showing that the multi-HCR can form 15 combinations simultaneously. In a living process of hypoxia-induced apoptosis and autophagy under complicated mitochondria and endoplasmic reticulum stress, the multi-HCR demonstrates excellent performance in detecting eight different miRNA changes. The multi-HCR provides a robust strategy for simultaneously profiling multiplexed miRNA biomarkers in studying complicated cellular processes.

Recent development of surface-enhanced Raman scattering for biosensing

Surface-Enhanced Raman Scattering (SERS) technology, as a powerful tool to identify molecular species by collecting molecular spectral signals at the single-molecule level, has achieved substantial progresses in the fields of environmental science, medical diagnosis, food safety, and biological analysis. As deepening research is delved into SERS sensing, more and more high-performance or multifunctional SERS substrate materials emerge, which are expected to push Raman sensing into more application fields. Especially in the field of biological analysis, intrinsic and extrinsic SERS sensing schemes have been widely used and explored due to their fast, sensitive and reliable advantages. Herein, recent developments of SERS substrates and their applications in biomolecular detection (SARS-CoV-2 virus, tumor etc.), biological imaging and pesticide detection are summarized. The SERS concepts (including its basic theory and sensing mechanism) and the important strategies (extending from nanomaterials with tunable shapes and nanostructures to surface bio-functionalization by modifying affinity groups or specific biomolecules) for improving SERS biosensing performance are comprehensively discussed. For data analysis and identification, the applications of machine learning methods and software acquisition sources in SERS biosensing and diagnosing are discussed in detail. In conclusion, the challenges and perspectives of SERS biosensing in the future are presented.

Nucleic Acid Probes in Bio-Imaging and Diagnostics: Recent Advances in ODN-Based Fluorescent and Surface-Enhanced Raman Scattering Nanoparticle and Nanostructured Systems

Raman nanoparticle probes are a potent class of optical labels for the interrogation of pathological and physiological processes in cells, bioassays, and tissues. Herein, we review the recent advancements in fluorescent and Raman imaging using oligodeoxyribonucleotide (ODN)-based nanoparticles and nanostructures, which show promise as effective tools for live-cell analysis. These nanodevices can be used to investigate a vast number of biological processes occurring at various levels, starting from those involving organelles, cells, tissues, and whole living organisms. ODN-based fluorescent and Raman probes have contributed to the achievement of significant advancements in the comprehension of the role played by specific analytes in pathological processes and have inaugurated new possibilities for diagnosing health conditions. The technological implications that have emerged from the studies herein described could open new avenues for innovative diagnostics aimed at identifying socially relevant diseases like cancer through the utilization of intracellular markers and/or guide surgical procedures based on fluorescent or Raman imaging. Particularly complex probe structures have been developed within the past five years, creating a versatile toolbox for live-cell analysis, with each tool possessing its own strengths and limitations for specific studies. Analyzing the literature reports in the field, we predict that the development of ODN-based fluorescent and Raman probes will continue in the near future, disclosing novel ideas on their application in therapeutic and diagnostic strategies.

Spotting the driving forces for SERS of two-dimensional nanomaterials

Recently, two-dimensional (2D) layered nanomaterials have become promising candidates for surface-enhanced Raman scattering (SERS) substrates due to their unique characteristics of ultrathin layer structure, outstanding optical properties and good biocompatibility, significantly contributing to remarkable SERS sensitivity, stability, and compatibility. Unlike traditional SERS substrates, 2D nanomaterials possess unparalleled layer-dependent, phase transition induced and anisotropic optical properties, which as driving forces significantly promote the SERS performance and development, as well as greatly enrich the SERS substrates and provide versatile resources for SERS research. For a profound understanding of the SERS effect of 2D nanomaterials, a review concentrating on these driving forces for SERS enhancement on 2D nanomaterials is written here for the first time, which strongly emphasizes the importance and influence of these driving forces on the SERS effect of 2D nanomaterials, including their intrinsic physical and chemical properties and external influencing factors. Moreover, the essential mechanisms of these driving forces for the SERS effect are also elaborated systematically. Finally, the challenges and future perspectives of SERS substrates based on 2D nanomaterials are concluded. This review will provide guiding principles and strategies for designing highly sensitive 2D nanomaterial SERS substrates and extending their potential applications based on SERS.

Design and Synthesis of SERS Materials for In Vivo Molecular Imaging and Biosensing

Surface-enhanced Raman scattering (SERS) is a feasible and ultra-sensitive method for biomedical imaging and disease diagnosis. SERS is widely applied to in vivo imaging due to the development of functional nanoparticles encoded by Raman active molecules (SERS nanoprobes) and improvements in instruments. Herein, the recent developments in SERS active materials and their in vivo imaging and biosensing applications are overviewed. Various SERS substrates that have been successfully used for in vivo imaging are described. Then, the applications of SERS imaging in cancer detection and in vivo intraoperative guidance are summarized. The role of highly sensitive SERS biosensors in guiding the detection and prevention of diseases is discussed in detail. Moreover, its role in the identification and resection of microtumors and as a diagnostic and therapeutic platform is also reviewed. Finally, the progress and challenges associated with SERS active materials, equipment, and clinical translation are described. The present evidence suggests that SERS could be applied in clinical practice in the future.

Nanomaterials meet surface-enhanced Raman scattering towards enhanced clinical diagnosis: a review

Surface-enhanced Raman scattering (SERS) is a very promising tool for the direct detection of biomarkers for the diagnosis of i.e., cancer and pathogens. Yet, current SERS strategies are hampered by non-specific interactions with co-existing substances in the biological matrices and the difficulties of obtaining molecular fingerprint information from the complex vibrational spectrum. Raman signal enhancement is necessary, along with convenient surface modification and machine-based learning to address the former issues. This review aims to describe recent advances and prospects in SERS-based approaches for cancer and pathogens diagnosis. First, direct SERS strategies for key biomarker sensing, including the use of substrates such as plasmonic, semiconductor structures, and 3D order nanostructures for signal enhancement will be discussed. Secondly, we will illustrate recent advances for indirect diagnosis using active nanomaterials, Raman reporters, and specific capture elements as SERS tags. Thirdly, critical challenges for translating the potential of the SERS sensing techniques into clinical applications via machine learning and portable instrumentation will be described. The unique nature and integrated sensing capabilities of SERS provide great promise for early cancer diagnosis or fast pathogens detection, reducing sanitary costs but most importantly allowing disease prevention and decreasing mortality rates.

Recent Progress on Solid Substrates for Surface-Enhanced Raman Spectroscopy Analysis

Surface-enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy technique with distinguished features of non-destructivity, ultra-sensitivity, rapidity, and fingerprint characteristics for analysis and sensors. The SERS signals are mainly dependent on the engineering of high-quality substrates. Recently, solid SERS substrates with diverse forms have been attracting increasing attention due to their promising features, including dense hot spot, high stability, controllable morphology, and convenient portability. Here, we comprehensively review the recent advances made in the field of solid SERS substrates, including their common fabrication methods, basic categories, main features, and representative applications, respectively. Firstly, the main categories of solid SERS substrates, mainly including membrane substrate, self-assembled substrate, chip substrate, magnetic solid substrate, and other solid substrate, are introduced in detail, as well as corresponding construction strategies and main features. Secondly, the typical applications of solid SERS substrates in bio-analysis, food safety analysis, environment analysis, and other analyses are briefly reviewed. Finally, the challenges and perspectives of solid SERS substrates, including analytical performance improvement and largescale production level enhancement, are proposed.

Pigment microparticles and microplastics found in human thrombi based on Raman spectral evidence

INTRODUCTION

Environmental microparticle is becoming a global pollutant and the entire population is increasingly exposed to the microparticles from artificial materials. The accumulation of microparticles including microplastics and its subsequent effects need to be investigated timely to keep sustainable development of human society.

OBJECTIVES

This study aimed to explore the accumulation of environmental particles in thrombus, the pathological structure in the blood circulation system.

METHODS

Patients receiving cardiovascular surgical operations were screened and twenty-six thrombi were collected, digested and filtered. Non-soluble microparticles were enriched on the filter membrane and then were analyzed and identified with Raman Spectrometer. The associations of particle status (presence or absence) or particle number in the thrombus and clinical indicators were examined. One strict quality control-particle detection system was designed to eliminate environmental contaminations.

RESULTS

Among twenty-six thrombi, sixteen contained eighty-seven identified particles ranging from 2.1 to 26.0 μm in size. The number of microparticles in each thrombus ranged from one to fifteen with the median reaching five. All the particles found in thrombi were irregularly block-shaped. Totally, twenty-one phthalocyanine particles, one Hostasol-Green particle, and one low-density polyethylene microplastic, which were from synthetic materials, were identified in thrombi. The rest microparticles included iron compounds and metallic oxides. After the adjustment for potential confounders, a significantly positive association between microparticle number and blood platelet levels was detected (P < 0.01).

CONCLUSION

This study provides the first photograph and Raman spectrum evidence of microparticles in thrombi. A large number of non-soluble particles including synthetic material microparticles could accumulate in arteries, suggesting that the risk of microparticle exposure was under-estimated and the re-evaluation of its health effects is urgently needed. There will be a series of reports on assessing the health effects of microparticle exposure in humans in the future and this research provided clues for the subsequent research.

Quantitative and Noninvasive Detection of SAH-Related MiRNA in Cerebrospinal Fluids In Vivo Using SERS Sensors Based on Acupuncture-Based Technology

Quantitative analysis of microRNAs (miRNAs) in a noninvasive manner is of vital importance for disease diagnosis and prognosis evaluation. However, conventional strategies for realizing accurate, simple, and sensitive detection of target molecules are still a challenge, especially for miRNAs due to their low abundance and susceptibility in the complex biological environment. Here, a novel surface-enhanced Raman scattering (SERS) strategy was established for quantitative detection and monitoring of miRNA-21-5p (miR-21-5p) in living cells and in vivo cerebrospinal fluid (CSF) by applying hairpin DNA (hpDNA)-conjugated gold nanostars (GNSs) SERS probes combined with acupuncture-based technology. This strategy enabled ultrasensitive exploration toward miR-21-5p in a wide range from 1 fM to 100 pM in cell lysates. Moreover, SERS analysis facilitated the detection and long-term monitoring for in vivo miR-21-5p noninvasively. This developed strategy promises to offer a powerful method for the analysis of multiple biomolecules in single cells and living bodies.

Recent Progress in Fabrication and Application of BN Nanostructures and BN-Based Nanohybrids

Due to its unique physical, chemical, and mechanical properties, such as a low specific density, large specific surface area, excellent thermal stability, oxidation resistance, low friction, good dispersion stability, enhanced adsorbing capacity, large interlayer shear force, and wide bandgap, hexagonal boron nitride (h-BN) nanostructures are of great interest in many fields. These include, but are not limited to, (i) heterogeneous catalysts, (ii) promising nanocarriers for targeted drug delivery to tumor cells and nanoparticles containing therapeutic agents to fight bacterial and fungal infections, (iii) reinforcing phases in metal, ceramics, and polymer matrix composites, (iv) additives to liquid lubricants, (v) substrates for surface enhanced Raman spectroscopy, (vi) agents for boron neutron capture therapy, (vii) water purifiers, (viii) gas and biological sensors, and (ix) quantum dots, single photon emitters, and heterostructures for electronic, plasmonic, optical, optoelectronic, semiconductor, and magnetic devices. All of these areas are developing rapidly. Thus, the goal of this review is to analyze the critical mass of knowledge and the current state-of-the-art in the field of BN-based nanomaterial fabrication and application based on their amazing properties.

Multiply Guaranteed and Successively Amplified Activation of a Catalytic DNA Machine for Highly Efficient Intracellular Imaging of MicroRNA

DNA amplification machines show great promise for intracellular imaging, yet are always constrained by off-site machinery activation or signal leakage, originating from the inherent thermodynamically driven hybridization between machinery substrates. Herein, an entropy-driven catalytic DNA amplification machine is integrated with the on-site amplified substrate exposure procedure to realize the high-contrast in vivo imaging of microRNA (miRNA). The key machinery substrate (fuel strands) is initially split into substrate subunits that are respectively grafted into an auxiliary DNA polymerization amplification accessory for eliminating the undesired signal leakage. Meanwhile, in target cells, the auxiliary polymerization accessory can be motivated by cell-specific mRNA for successively restoring their intact machine-propelling functions for guaranteeing the on-site amplified imaging of miRNA with high specificity. This intelligent on-site multiply guaranteed machinery can improve the specificity of catalytic DNA machines for discriminating different cell types and, thus, can provide a remarkable prospect in biomedical diagnosis.

Understanding the bidirectional interactions between two-dimensional materials, microorganisms, and the immune system

Two-dimensional (2D) materials such as the graphene-based materials, transition metal dichalcogenides, transition metal carbides and nitrides (MXenes), black phosphorus, hexagonal boron nitride, and others have attracted considerable attention due to their unique physicochemical properties. This is true not least in the field of medicine. Understanding the interactions between 2D materials and the immune system is therefore of paramount importance. Furthermore, emerging evidence suggests that 2D materials may interact with microorganisms - pathogens as well as commensal bacteria that dwell in and on our body. We discuss the interplay between 2D materials, the immune system, and the microbial world in order to bring a systems perspective to bear on the biological interactions of 2D materials. The use of 2D materials as vectors for drug delivery and as immune adjuvants in tumor vaccines, and 2D materials to counteract inflammation and promote tissue regeneration, are explored. The bio-corona formation on and biodegradation of 2D materials, and the reciprocal interactions between 2D materials and microorganisms, are also highlighted. Finally, we consider the future challenges pertaining to the biomedical applications of various classes of 2D materials.

A nanohybrid of Prussian blue supported by boracic acid-modified g-C3N4 for Raman recognition of cell surface sialic acid and photothermal/photodynamic therapy

Theranostic nanoplatforms with accurate diagnosis and effective therapy show a bright prospect for tumor treatments. Herein, a novel boracic acid-modified graphite carbon nitride and Prussian blue nanohybrid (PB@B-g-C₃N₄) was developed, which provides sialic acid-targeted Raman recognition and synergistic photothermal/photodynamic therapy in the near-infrared region. Owing to the specific interaction between boracic acid and sialic acid and Raman response at 2157 cm^-1 of PB, the nanohybrids exhibit high specificity and Raman sensitivity for detection of the overexpressed sialic acid on tumor cells. Moreover, the photothermal conversion efficiency of PB@B-g-C₃N₄ is as high as 47.0% with 808 nm laser irradiation due to the enhanced absorbance of PB@B-g-C₃N₄. PB@B-g-C₃N₄ also possesses excellent photodynamic activity, which is attributed to the energy transfer of PB (type I) and electron transfer between PB and B-g-C₃N₄ (type II). This nanotheranostic agent for Raman recognition of cancer markers and synergistic photothermal/photodynamic therapy holds great potential for the development of efficient theranostic nanoplatforms.

Intracellular miRNA-Triggered Surface-Enhanced Raman Scattering Imaging and Dual Gene-Silencing Therapy of Cancer Cell

Development of theranostic nanosystems integrating cascaded surface-enhanced Raman scattering (SERS) imaging and gene silencing therapy for accurate cancer diagnosis and treatment is still a big challenge and rarely reported. Herein, a novel Au nanoparticles (AuNPs)-based theranostic nanosystem containing AuNP-Ys and AuNP-Ds for highly sensitive and specific cancer diagnosis and treatment was proposed for cascaded SERS imaging of intracellular cancer-related miR-106a and miR-106a-triggered DNAzyme-based dual gene-silencing therapy of cancer cells. The AuNP-Ys were prepared by modifying the AuNPs with specially designed Y-motifs, and the AuNP-Ds were obtained by colabeling Raman molecules and dsDNA linkers on AuNPs. When identifying the intracellular cancer-related miRNAs, the Y-motifs and dsDNA linkers undergoes miRNA-triggered ATP-driven conformational transitions and releases the miRNA for recycling, which results in the formation of AuNP network nanostructures to generate significantly enhanced SERS signals for sensitive identification of the cancer cells as well as the amplification and specific activation of DNAzymes to catalyze the Mg²⁺-assisted cleavage of the Survivin and c-Jun mRNAs for effective dual gene-silencing therapy of cancer cells. The AuNP-based theranostic nanosystem achieves the synergism of target-triggered SERS imaging and DNAzyme-based dual gene-silencing therapy with enhanced specificity, sensitivity, and curative effect, which can be a powerful tool for accurate diagnosis and efficient treatment of cancers.

Early detection of lung cancer via biointerference-free, target microRNA-triggered core-satellite nanocomposites

MicroRNAs (miRNAs) are emerging as essential liquid biopsy markers for early cancer detection. Currently, the clinical applications of miRNAs are lagging behind due to their high sequence similarity and rarity. Herein, we propose biointerference-free, target-triggered core-satellite nanocomposites for ultrasensitive surface-enhanced Raman spectroscopy (SERS) detection of lung cancer-related miRNA-21. Through the hybridization-based recognition effect, we observe an enormous SERS signal enhancement caused by miRNA-21-triggered assembly of core-satellite nanocomposites. This enables the sensitive detection of miRNA-21 down to the 0.1 fM level in a linear range of 10 fM to 1 nM. The use of a biointerference-free reporter further allows quantitative and direct detection of miRNA-21 from complex plasma samples, without RNA pre-extraction. As a proof of principle, we measure the level of plasma miRNA-21 in 20 lung cancer patients and 10 healthy participants. Significantly higher levels of miRNA-21 are determined in lung cancer patients than in healthy participants, with clear lower expression in stage I (n = 10) than in stage III-IV (n = 10) lung cancer patients. We, therefore, believe that this proposed strategy will have high clinical potential for sensitive quantification of miRNA markers in liquid biopsy samples and act as a complementary method for the early detection of lung cancer.

A bioinspired hollow g-C3N4-CuPc heterostructure with remarkable SERS enhancement and photosynthesis-mimicking properties for theranostic applications

Surface-enhanced Raman scattering (SERS) based on chemical mechanism (CM) has great potential for superior stability and selectivity. Moreover, a bioinspired CM-Raman substrate-Raman reporter system with charge separation and electron transport nature provides thylakoid-mimicking potential for multifunctional applications. Herein, hollow carbon nitride nanospheres hierarchically assembled with a well-oriented copper(ii) phthalocyanine layer and hyaluronic acid (HCNs@CuPc@HA) were designed as a light-harvesting nanocomposite and photosynthesis-mimicking nanoscaffold that enhance both CM-SERS and photoredox catalysis. Remarkable SERS enhancement was achieved due to the strengthened short-range substrate–molecule interaction, enriched CuPc molecule loading and enhanced light–mater interactions. Meanwhile, the uniform CuPc molecule film mimics a photo-pigment to accelerate the near infrared (NIR)-oxygen generation and photodynamic catalysis of photosynthetic membrane-like HCNs. The experimental findings were further validated by numerical theory analysis. The greatly enhanced SERS signal and photosynthetic-mimicking properties of the heterostructure (denoted as HCNCHs) were successfully employed for circulating tumor cell (CTC) diagnosis and SERS imaging-guided cancer catalytic therapy in tumor xenograft models.

Thylakoid-inspired HCNs@CuPc@HA is designed as a light-harvesting nanocomposite and photosynthesis-mimicking nanoscaffold to simultaneously enhance chemical mechanism-based SERS and photosynthesis-mimicking catalysis for theranostics application.

A Liquid Interfacial SERS Platform on a Nanoparticle Array Stabilized by Rigid Probes for the Quantification of Norepinephrine in Rat Brain Microdialysates

For the reliable determination of trace chemicals in the brain, we created a SERS platform based on a functionalized AuNPs array formed at a liquid/liquid interface in a uniform fashion over a large substrate area through ternary regulations for real-time quantification of trace norepinephrine (NE). The rigid molecule, 4-(thiophen-3-ylethynyl)-benzaldehyde (RP1) was designed and co-assembled at AuNPs with 4-mercaptophenylboronic acid (MPBA) to chemically define NE via dual recognition. Meanwhile, the rigid structure assembly of RP1 and MPBA efficiently fixed the interparticle gap, guaranteeing reproducible SERS analysis. Furthermore, the Raman peak of C≡C group in the silent region was taken as a response element to further improve the accuracy. Combined with microdialysis, this SERS platform was developed for in-the-field testing of NE in rat brain microdialysates following anxiety.

Endogenous MicroRNA Accurate Diagnostics to Guide Photothermal Therapy

Developing an intelligent theranostic nanoplatform with satisfied diagnostic accuracy and therapeutic efficiency holds great promise for personalized nanomedicine. Herein, we constructed a smart nanodevice for the accurate diagnosis of endogenous cancer microRNA (miRNA) biomarkers and efficient photothermal therapy (PTT). The nanodevice was composed of polydopamine (PDA)-functionalized CuS nanosheets (CuS@PDA NSs) and three elaborate DNA hairpin probes (TDHPs). The CuS@PDA NSs acted as efficient delivery vehicles and photothermal agents. They provided a large surface area available for an efficient and facile loading of TDHPs and a high-fluorescence (FL) quenching performance to achieve an ultralow background signal. The intracellular miRNA triggered TDHPs to assemble into three-arm branched junction structures for a strong fluorescence recovery as output signals to discriminate cancer cells from normal cells with an excellent sensitivity. The CuS@PAD NSs showed a good photothermal conversion efficiency in the near-infrared II (NIR II) region to mediate a good photothermal performance to kill cancer cells. A remarkable antitumor therapeutic effect was achieved in vivo. This work integrated highly sensitive detection to endogenous cancer biomarkers and valid therapeutic potency to tumor-bearing mice, indicating its promising biomedical applications.

High and stable surface-enhanced Raman spectroscopy activity of h-BN nanosheet/Au1Ag3 nanoalloy hybrid membrane for melamine determination

In this work, a hexagonal boron nitride (h-BN)/AuAg nanoalloy hybrids (NAHs) was synthesized to fabricate h-BN/Au1Ag3 membrane as a solid surface-enhanced Raman spectroscopy (SERS) substrate for sensitive SERS detection of melamine. The AuAg nanoalloys were in situ grown on h-BN by chemical reduction method, and the Au/Ag molar ratio was tuned to achieve optimal SERS performance. After the SERS performance of h-BN/AuAg NAHs with different Au/Ag ratios was analyzed, h-BN/Au1Ag3 NAHs were chosen for SERS analysis. The h-BN/Au1Ag3 membrane can be obtained through simple filtration of h-BN/Au1Ag3 NAHs on chromatographic paper. As expected, the solid SERS substrates of h-BN/Au1Ag3 membrane were uniform and demonstrated good selectivity, repeatability and reproducibility for SERS detection of melamine. The results demonstrate that h-BN/Au1Ag3 membrane exhibited high SERS activity for 4-mercaptobenzoic acid (4-MBA) with limit of detection (LOD) at 1.0 ng L-1, and its analytical enhancement factor (AEF) reached 3.6 × 108. The possible enhancement mechanism, including electromagnetic mechanisms (EM) and chemical mechanisms (CM) were illustrated by finite-difference time-domain (FDTD) and density functional theory (DFT) simulations in detail, respectively. The concentration of melamine in the 0.05-5.0 mg L-1 range showed good linear relationship (R2 = 0.9940) with SERS intensity with LOD of 0.01 mg L-1. Finally, the recoveries of melamine in liquid milk samples are 87.7-105.7% with relative standard deviations (RSDs) in range of 0.6-2.6%, providing precise safety evaluation of melamine in milk samples.

Shedding Light on DNA-Based Nanoprobes for Live-Cell MicroRNA Imaging

DNA-based nanoprobes integrated with various imaging signals have been employed for fabricating versatile biosensor platforms for the study of intracellular biological process and biomarker detection. The nanoprobes developments also provide opportunities for endogenous microRNA (miRNA) in situ analysis. In this review, the authors are primarily interested in various DNA-based nanoprobes for miRNA biosensors and declare strategies to reveal how to customize the desired nanoplatforms. Initially, various delivery vehicles for nanoprobe architectures transmembrane transport are delineated, and their biosecurity and ability for resisting the complex cellular environment are evaluated. Then, the novel strategies for designing DNA sequences as target miRNA specific recognition and signal amplification modules for miRNA detection are presented. Afterward, recent advances in imaging technologies to accurately respond and produce significant signal output are summarized. Finally, the challenges and future directions in the field are discussed.

Emergence of Responsive Surface-Enhanced Raman Scattering Probes for Imaging Tumor-Associated Metabolites

As a core hallmark of cancer, metabolic reprogramming alters the metabolic networks of cancer cells to meet their insatiable appetite for energy and nutrient. Tumor-associated metabolites, the products of metabolic reprogramming, are valuable in evaluating tumor occurrence and progress timely and accurately because their concentration variations usually happen earlier than the aberrances demonstrated in tissue structure and function. As an optical spectroscopic technique, surface-enhanced Raman scattering (SERS) offers advantages in imaging tumor-associated metabolites, including ultrahigh sensitivity, high specificity, multiplexing capacity, and uncompromised signal intensity. This review first highlights recent advances in the development of stimuli-responsive SERS probes. Then the mechanisms leading to the responsive SERS signal triggered by tumor metabolites are summarized. Furthermore, biomedical applications of these responsive SERS probes, such as the image-guided tumor surgery and liquid biopsy examination for tumor molecular typing, are summarized. Finally, the challenges and prospects of the responsive SERS probes for clinical translation are also discussed.

Multifunctional MnO2/Ag3SbS3 Nanotheranostic Agent for Single-Laser-Triggered Tumor Synergistic Therapy in the NIR-II Biowindow

Regulating the level of reactive oxygen species (ROS) in a tumor is an efficient and innovative anticancer strategy. However, the therapeutic efficacy of ROS-based therapies, such as chemodynamic therapy (CDT) and photodynamic therapy (PDT), offers finite outcomes due to the oxygen dependence and limited concentration of hydrogen peroxide (H₂O₂) and overexpression of glutathione (GSH) within the tumor microenvironment (TME), so a single therapeutic strategy is insufficient to completely eliminate tumors. Therefore, we demonstrated an omnipotent nanoplatform MnO₂/Ag₃SbS₃ (abbreviated as MA) with strong optical absorbance in the NIR-II biowindow and oxygen self-sufficient ROS-mediated ability, which not only relieves tumor hypoxia significantly but also enhances the photothermal therapy (PTT)/PDT/CDT efficacy. By 1064 nm laser irradiation, MnO₂/Ag₃SbS₃ nanoparticles (NPs) reveal a favorable photothermal conversion efficiency of 23.15% and achieve a single-laser-triggered NIR-II PTT/PDT effect, resulting in effective tumor elimination. Once internalized into the tumor, MnO₂/Ag₃SbS₃ NPs will be degraded to Mn²⁺ and Ag₃SbS₃. The released Ag₃SbS₃ NPs as a NIR-II phototherapy agent could be utilized for photoacoustic imaging-guided NIR-II PDT/PTT. Mn²⁺ could be used as a Fenton-like catalyst to continuously catalyze endogenous H₂O₂ for generating highly virulent hydroxyl radicals (^•OH) for CDT and O₂ for PDT, enhancing the efficiency of PDT and CDT, respectively. Meanwhile, Mn²⁺ realizes magnetic resonance imaging-guided accurate tumor therapy. Moreover, the MnO₂/Ag₃SbS₃ NPs could deplete intracellular GSH in TME to promote oxidative stress of the tumor, further strengthening ROS-mediated antitumor treatment efficacy. Overall, this work presents a distinctive paradigm of TME-responsive PDT/CDT/PTT in the second near-infrared biowindow by depleting GSH and decomposing H₂O₂ for efficient and precise cancer treatment.

Highly Sensitive Detection of Elevated Exosomal miR-122 Levels in Radiation Injury and Hepatic Inflammation Using an Aptamer-Functionalized SERS-Sandwich Assay

Radiation-induced organ injury is one of the major fallouts noticed during radiotherapy treatment of malignancies and other detrimental radiation exposures. MicroRNA (miRNA), which is involved in multiple critical cellular processes, is released from the cells of damaged organs in cellular vesicles, commonly known as exosomes. Specifically, exosomal miR-122 is reported to be actively involved in radiation-actuated rectal and hepatic injuries or inflammation. In this work, we developed a surface-enhanced Raman spectroscopy (SERS) assay for the quantitative and targeted detection of exosomal miR-122 in mice after drug/radiation treatments. In particular, an aptamer-functionalized magnetic capturing element and Au shell nanoparticle (NP)-based SERS tags were utilized, which upon recognition of the target miRNA constituted a "sandwich" formation, with which an 8 fM limit of detection (LOD) could be achieved. Using this SERS assay, we further found that radiation injury led to the elevated expression of exosomal miR-122 in mice at 4 h postirradiation, confirmed by the quantitative real-time PCR method. It was demonstrated that the drug-induced hepatic inflammation could also be assessed via detecting miR-122 using this SERS method. As such, this work has demonstrated the achievement of a highly selective and sensitive probe of exosomal miRNA, which may thus open a gateway for promising usage in drug/radiation-induced inflammation.

Recent advances in catalytic hairpin assembly signal amplification-based sensing strategies for microRNA detection

Accumulative evidences have indicated that abnormal expression of microRNAs (miRNAs) is closely associated with many health disorders, making them be regarded as potentialbiomarkers for early clinical diagnosis. Therefore, it is extremely necessary to develop a highly sensitive, specific and reliable approach for miRNA analysis. Catalytic hairpin assembly (CHA) signal amplification is an enzyme-free toehold-mediated strand displacement method, exhibiting significant potential in improving the sensitivity of miRNA detection strategies. In this review, we first describe the potential of miRNAs as disease biomarkers and therapeutics, and summarize the latest advances in CHA signal amplification-based sensing strategies for miRNA monitoring. We describe the characteristics and mechanism of CHA signal amplification and classify the CHA-based miRNA sensing strategies into several categories based on the "signal conversion substance", including fluorophores, enzymes, nanomaterials, and nucleotide sequences. Sensing performance, limit of detection, merits and disadvantages of these miRNA sensing strategies are discussed. Moreover, the current challenges and prospects are also presented.

Rational Utilization of Photoelectrochemistry of Photosystem II for Self-Powered Photocathodic Detection of MicroRNA in Cells

The photoanode, photosystem II (PSII)/hierarchical inverse opal (IO) TiO₂, is coupled to the complementary photocathode, PbS quantum dots (QDs)/DNA probes, which is then integrated into a two-compartment photoelectrochemical (PEC) cell to achieve a self-powered system to enable photocathodic detection of microRNA-10b from HeLa cells. In such a system, all of the PSII catalytic products, i.e., electrons, protons, and O₂, were rationally utilized and could overcome the general issue of varied O₂ levels in photocathodic detection. The correlation between the target-triggered formation of the DNA complexes and the catalytic reduction of the dissolved O₂ makes possible the steady microRNA-10b detection with good sensitivity and selectivity. This work has unveiled the ability of PSII to construct self-powered detecting devices and shed light on its application in new arenas.

Toward Sensitive and Reliable Surface-Enhanced Raman Scattering Imaging: From Rational Design to Biomedical Applications

Early specific detection through indicative biomarkers and precise visualization of lesion sites are urgent requirements for clinical disease diagnosis. However, current detection and optical imaging methods are insufficient for these demands. Molecular imaging technologies are being intensely studied for reliable medical diagnosis. In the past several decades, molecular imaging with surface-enhanced Raman scattering (SERS) has significant advances from analytical chemistry to medical science. SERS is the inelastic scattering generated from the interaction between photons and substances, presenting molecular structure information. The outstanding SERS virtues of high sensitivity, high specificity, and resistance to biointerference are highly advantageous for biomarker detection in a complex biological matrix. In this work, we review recent progress on the applications of SERS imaging in clinical diagnostics. With the assistance of SERS imaging, the detection of disease-related proteins, nucleic acids, small molecules, and pH of the cellular microenvironment can be implemented for adjuvant medical diagnosis. Moreover, multimodal imaging integrates the high penetration and high speed of other imaging modalities and imaging precision of SERS imaging, resulting in final complete and accurate imaging outcomes and exhibiting robust potential in the discrimination of pathological tissues and surgical navigation. As a promising molecular imaging technology, SERS imaging has achieved remarkable performance in clinical diagnostics and the biomedical realm. It is expected that this review will provide insights for further development of SERS imaging and promote the rapid progress and successful translation of advanced molecular imaging with clinical diagnostics.

Two-dimensional biomaterials: material science, biological effect and biomedical engineering applications

To date, nanotechnology has increasingly been identified as a promising and efficient means to address a number of challenges associated with public health. In the past decade, two-dimensional (2D) biomaterials, as a unique nanoplatform with planar topology, have attracted explosive interest in various fields such as biomedicine due to their unique morphology, physicochemical properties and biological effect. Motivated by the progress of graphene in biomedicine, dozens of types of ultrathin 2D biomaterials have found versatile bio-applications, including biosensing, biomedical imaging, delivery of therapeutic agents, cancer theranostics, tissue engineering, as well as others. The effective utilization of 2D biomaterials stems from the in-depth knowledge of structure-property-bioactivity-biosafety-application-performance relationships. A comprehensive summary of 2D biomaterials for biomedicine is still lacking. In this comprehensive review, we aim to concentrate on the state-of-the-art 2D biomaterials with a particular focus on their versatile biomedical applications. In particular, we discuss the design, fabrication and functionalization of 2D biomaterials used for diverse biomedical applications based on the up-to-date progress. Furthermore, the interactions between 2D biomaterials and biological systems on the spatial-temporal scale are highlighted, which will deepen the understanding of the underlying action mechanism of 2D biomaterials aiding their design with improved functionalities. Finally, taking the bench-to-bedside as a focus, we conclude this review by proposing the current crucial issues/challenges and presenting the future development directions to advance the clinical translation of these emerging 2D biomaterials.

Recent progress of SERS optical nanosensors for miRNA analysis

This review focuses on emerging applications of surface-enhanced Raman spectroscopy (SERS) optical nanosensors for miRNA analysis, in which the key enhancement factors of the SERS signal, i.e. SERS-active substrates, SERS nanoprobes and nano-assembly strategy, are emphasized. This article includes many nanomaterials for miRNA analysis by the SERS technique. We summarize these reported nanomaterials mainly according to their function in the miRNA assay biosensor. We also briefly summarize the research progress of these nanomaterials in SERS detection of intracellular miRNA. Finally, we discussed the prospect and limitations of SERS nanosensors for analyzing miRNA.

Stability of Boron Nitride Nanosphere Dispersions in the Presence of Polyelectrolytes

Boron nitride nanospheres (BNNSs) were functionalized with polyelectrolytes. The effect of the polyelectrolyte dose and ionic strength on the charging and aggregation properties was investigated. At appropriate polyelectrolyte doses, charge neutralization occurred, whereas by increasing the dose, charge reversal was observed. The complete coating of the particles was indicated by a plateau in the ζ-potential values, which do not change significantly beyond the dose corresponding to the onset of such a plateau. The dispersions were highly aggregated around the charge neutralization point, while at lower or higher doses, the particles were stable. The salt-induced aggregation experiments revealed that the polyelectrolyte coatings contribute to the colloidal stability of the particles, namely, the critical coagulation concentrations deviated from the one determined for bare BNNSs. The presence of electrostatic and steric interparticle forces induced by the adsorbed polyelectrolyte chains was assumed. The obtained results confirm that the comprehensive investigation of the colloidal stability of BNNS particles is crucial to design stable or unstable dispersions and that polyelectrolytes are suitable agents for both stabilization and destabilization of BNNS dispersions, depending on the purpose of their application.