Plasmonic enzyme immunoassay via nanobody-driven controllable aggregation of gold nanoparticles for detection of ochratoxin A in pepper

Ochratoxin A (OTA) in food poses a serious challenge to public health. Herein, using the nanobody-driven controllable aggregation of gold nanoparticles (AuNPs) in a glucose oxidase-tyramine-horseradish peroxidase (GOx-TYR-HRP) system, we propose a direct competitive plasmonic enzyme immunoassay (dc-PEIA) for OTA detection. The OTA-GOx conjugate catalyzes glucose to produce hydrogen peroxide (H2O2), and then HRP catalyzes H2O2 to generate hydroxyl radical which induces the crosslink of TYR. Crosslinked TYR leads to aggregation of AuNPs through strong electrostatic interactions, which is tunable based on the competition of OTA-GOx and free OTA for binding the immobilized nanobody. The optimized dc-PEIA achieves an instrumental limit of detection (LOD) of 0.275 ng/mL and a visual LOD of 1.56 ng/mL. It exhibits good selectivity for OTA and accuracy in the analysis of pepper samples, with the confirmation of high-performance liquid chromatography. Overall, the dc-PEIA is demonstrated as a useful tool for detecting OTA in food.

The Nanozyme Revolution: Enhancing the Performance of Medical Biosensing Platforms

Nanozymes represent a class of nanosized materials that exhibit innate catalytic properties similar to biological enzymes. The unique features of these materials have positioned them as promising candidates for applications in clinical sensing devices, specifically those employed at the point-of-care. They notably have found use as a means to amplify signals in nanosensor-based platforms and thereby improve sensor detection limits. Recent developments in the understanding of the fundamental chemistries underpinning these materials have enabled the development of highly effective nanozymes capable of sensing clinically relevant biomarkers at detection limits that compete with "gold-standard" techniques. However, there remain considerable hurdles that need to be overcome before these nanozyme-based sensors can be utilized in a platform ready for clinical use. An overview of the current understandings of nanozymes for disease diagnostics and biosensing applications and the unmet challenges that must be considered prior to their translation in clinical diagnostic tests is provided.

Application of the Peroxidase‒like Activity of Nanomaterials for the Detection of Pathogenic Bacteria and Viruses

Infectious diseases caused by pathogenic bacteria and viruses pose a significant threat to human life and well-being. The prompt identification of these pathogens, characterized by speed, accuracy, and efficiency, not only aids in the timely screening of infected individuals and the prevention of further transmission, but also facilitates the precise diagnosis and treatment of patients. Direct smear microscopy, microbial culture, nucleic acid-based polymerase chain reaction (PCR), and enzyme-linked immunosorbent assay (ELISA) based on microbial surface antigens or human serum antibodies, have made substantial contributions to the prevention and management of infectious diseases. Due to its shorter processing time, simple equipment requirements, and no need for professional and technical personnel, ELISA has inherent advantages over other methods for detecting pathogenic bacteria and viruses. Horseradish peroxidase mediated catalysis of substrate coloration is the key for the detection of target substances in ELISA. However, the variability, high cost, and environmental susceptibility of natural peroxidase greatly limit the application of ELISA in pathogen detection. Compared with natural enzymes, nanomaterials with enzyme-mimicking activity are inexpensive, highly environmentally stable, easy to store and mass producing, etc. Based on their peroxidase-like activities and unique physicochemical properties, nanomaterials can greatly improve the efficiency and ease of use of ELISA-like detection methods for pathogenic bacteria and viruses. This review introduces recent advances in the application of nanomaterials with peroxidase-like activity for the detection of pathogenic bacteria (both gram-negative bacteria and gram-positive bacteria) and viruses (both RNA viruses and DNA viruses). The emphasis is on the detection principle and the evaluation of effectiveness. The limitations and prospects for future translations are also discussed.

Nanomaterials for detection of biomolecules and delivering therapeutic agents in theragnosis: A review

Nanomaterials are emerging facts used to deliver therapeutic agents in living systems. Nanotechnology is used as a compliment by implementing different kinds of nanotechnological applications such as nano-porous structures, functionalized nanomaterials, quantum dots, carbon nanomaterials, and polymeric nanostructures. The applications are in the initial stage, which led to achieving several diagnoses and therapy in clinical practice. This review conveys the importance of nanomaterials in post-genomic employment, which includes the design of immunosensors, immune assays, and drug delivery. In this view, genomics is a molecular tool containing large databases that are useful in choosing an apt molecular inhibitor such as drug, ligand and antibody target in the drug delivery process. This study identifies the expression of genes and proteins in analysis and classification of diseases. Experimentally, the study analyses the design of a disease model. In particular, drug delivery is a boon area to treat cancer. The identified drugs enter different phase trails (Trails I, II, and III). The genomic information conveys more essential entities to the phase I trials and helps to move further for other trails such as trails-II and III. In such cases, the biomarkers play a crucial role by monitoring the unique pathological process. Genetic engineering with recombinant DNA techniques can be employed to develop genetically engineered disease models. Delivering drugs in a specific area is one of the challenging issues achieved using nanoparticles. Therefore, genomics is considered as a vast molecular tool to identify drugs in personalized medicine for cancer therapy.

Optical Biosensor Based on Graphene and Its Derivatives for Detecting Biomolecules

Graphene and its derivatives show great potential for biosensing due to their extraordinary optical, electrical and physical properties. In particular, graphene and its derivatives have excellent optical properties such as broadband and tunable absorption, fluorescence bursts, and strong polarization-related effects. Optical biosensors based on graphene and its derivatives make nondestructive detection of biomolecules possible. The focus of this paper is to review the preparation of graphene and its derivatives, as well as recent advances in optical biosensors based on graphene and its derivatives. The working principle of face plasmon resonance (SPR), surface-enhanced Raman spectroscopy (SERS), fluorescence resonance energy transfer (FRET) and colorimetric sensors are summarized, and the advantages and disadvantages of graphene and its derivatives applicable to various types of sensors are analyzed, and the methods of surface functionalization of graphene and its derivatives are introduced; these optical biosensors can be used for the detection of a range of biomolecules such as single cells, cellular secretions, proteins, nucleic acids, and antigen-antibodies; these new high-performance optical sensors are capable of detecting changes in surface structure and biomolecular interactions with the advantages of ultra-fast detection, high sensitivity, label-free, specific recognition, and the ability to respond in real-time. Problems in the current stage of application are discussed, as well as future prospects for graphene and its biosensors. Achieving the applicability, reusability and low cost of novel optical biosensors for a variety of complex environments and achieving scale-up production, which still faces serious challenges.

Nanobody and Nanozyme-Enabled Immunoassays with Enhanced Specificity and Sensitivity

Immunoassay as a rapid and convenient method for detecting a variety of targets has attracted tremendous interest with its high specificity and sensitivity. Among the commonly used immunoassays, enzyme-linked immunosorbent assay has been widely used as a gold standard method in various fields that consists of two main components including a recognition element and an enzyme label. With the rapid advances in nanotechnology, nanobodies and nanozymes enable immunoassays with enhanced specificity and sensitivity compared with conventional antibodies and natural enzymes. This review is focused on the applications of nanobodies and nanozymes in immunoassays. Nanobodies advantage lies in their small size, high specificity, mass expression, and high stability. Nanozymes with peroxidase, phosphatase, and oxidase activities and their applications in immunoassays are highlighted and discussed in detail. In addition, the challenges and outlooks in terms of the use of nanobodies and the development of novel nanozymes in practical applications are discussed.

Two-dimensional material-based virus detection

Cost-effective, rapid, and accurate virus detection technologies play key roles in reducing viral transmission. Prompt and accurate virus detection enables timely treatment and effective quarantine of virus carrier, and therefore effectively reduces the possibility of large-scale spread. However, conventional virus detection techniques often suffer from slow response, high cost or sophisticated procedures. Recently, two-dimensional (2D) materials have been used as promising sensing platforms for the high-performance detection of a variety of chemical and biological substances. The unique properties of 2D materials, such as large specific area, active surface interaction with biomolecules and facile surface functionalization, provide advantages in developing novel virus detection technologies with fast response and high sensitivity. Furthermore, 2D materials possess versatile and tunable electronic, electrochemical and optical properties, making them ideal platforms to demonstrate conceptual sensing techniques and explore complex sensing mechanisms in next-generation biosensors. In this review, we first briefly summarize the virus detection techniques with an emphasis on the current efforts in fighting again COVID-19. Then, we introduce the preparation methods and properties of 2D materials utilized in biosensors, including graphene, transition metal dichalcogenides (TMDs) and other 2D materials. Furthermore, we discuss the working principles of various virus detection technologies based on emerging 2D materials, such as field-effect transistor-based virus detection, electrochemical virus detection, optical virus detection and other virus detection techniques. Then, we elaborate on the essential works in 2D material-based high-performance virus detection. Finally, our perspective on the challenges and future research direction in this field is discussed.

Nanotechnology: A Potential Weapon to Fight against COVID-19

The COVID-19 infections have posed an unprecedented global health emergency, with nearly three million deaths to date, and have caused substantial economic loss globally. Hence, an urgent exploration of effective and safe diagnostic/therapeutic approaches for minimizing the threat of this highly pathogenic coronavirus infection is needed. As an alternative to conventional diagnosis and antiviral agents, nanomaterials have a great potential to cope with the current or even future health emergency situation with a wide range of applications. Fundamentally, nanomaterials are physically and chemically tunable and can be employed for the next generation nanomaterial-based detection of viral antigens and host antibodies in body fluids as antiviral agents, nanovaccine, suppressant of cytokine storm, nanocarrier for efficient delivery of antiviral drugs at infection site or inside the host cells, and can also be a significant tool for better understanding of the gut microbiome and SARS-CoV-2 interaction. The applicability of nanomaterial-based therapeutic options to cope with the current and possible future pandemic is discussed here.

Plasmonic Imaging of Dynamic Interactions between Membrane Receptor Clusters beyond the Diffraction Limit in Live Cells

As a general mechanism, ligand-induced receptor clustering on cell membrane plays determinative roles in pattern recognition and transmembrane signaling. Nevertheless, probing the dynamic characteristics for the complicated interactions between receptor clusters remains difficult because of the lack of strategy for receptor cluster labeling and long-term monitoring in live cells. Herein, we proposed a data-mining-integrated plasmon coupling microscopy to study the dynamic cluster-cluster interactions on cell surface. The receptor clusters were activated and labeled with multivalent plasmonic nanoprobes, which enables the real-time monitoring of individual receptor clusters and the measurement of cluster-cluster interactions from the analysis of plasmonic coupling for the nanoprobe pairs beyond the diffraction limit. Using this method, we found that the protease-activated receptor 1 (PAR1) clusters would experience an initial contact and then form a weakly bound cluster-cluster complex, followed by cluster fusion to generate large-sized signaling complexes. The underlying state transitions for the cluster-cluster fusion process were uncovered using a data-mining technique named the K-means-based hidden Markov model with the scattering intensity of coupled nanoprobe pairs as observations. All of the findings from single-particle analysis and bulk measurements suggested that the allosteric inhibitors could suppress the dynamic transitions from the weakly bound cluster-cluster complexes to fused signaling complexes, leading to the subsequent downregulation of intracellular calcium signaling pathways. We believe that this strategy is promising for imaging and monitoring receptor clustering as well as protein phase separation on the cell surface in various biological and physiological processes.

Micro/nanotechnology-inspired rapid diagnosis of respiratory infectious diseases

Humans have suffered from a variety of infectious diseases since a long time ago, and now a new infectious disease called COVID-19 is prevalent worldwide. The ongoing COVID-19 pandemic has led to research of the effective methods of diagnosing respiratory infectious diseases, which are important to reduce infection rate and help the spread of diseases be controlled. The onset of COVID-19 has led to the further development of existing diagnostic methods such as polymerase chain reaction, reverse transcription polymerase chain reaction, and loop-mediated isothermal amplification. Furthermore, this has contributed to the further development of micro/nanotechnology-based diagnostic methods, which have advantages of high-throughput testing, effectiveness in terms of cost and space, and portability compared to conventional diagnosis methods. Micro/nanotechnology-based diagnostic methods can be largely classified into (1) nanomaterials-based, (2) micromaterials-based, and (3) micro/nanodevice-based. This review paper describes how micro/nanotechnologies have been exploited to diagnose respiratory infectious diseases in each section. The research and development of micro/nanotechnology-based diagnostics should be further explored and advanced as new infectious diseases continue to emerge. Only a handful of micro/nanotechnology-based diagnostic methods has been commercialized so far and there still are opportunities to explore.

Visible-Light-Driven Photocatalysis-Enhanced Nanozyme of TiO2 Nanotubes@MoS2 Nanoflowers for Efficient Wound Healing Infected with Multidrug-Resistant Bacteria

To enhance the catalytic activity of the nanozymes for efficient wound healing infected with multidrug-resistant bacteria, photo-based motivations have been suggested, but attention is mainly focused on the external stimulus of near-infrared light, while the inexhaustible visible one is promising but lack of study. Herein, an efficient visible light-stimulated peroxidase-like nanozyme system, TiO₂ nanotubes coated with MoS₂ nanoflowers (TiO₂ NTs@MoS₂ ), is discovered for efficient bacterial treatment. Based on the synergetic effects between the two components, the bandgap of the TiO₂ NTs can be narrowed from 3.2 to 2.97 eV due to the MoS₂ loading, which extended the light response of TiO₂ to visible-light range and enhanced the photocatalytic activity accordingly. Meanwhile, the peroxidase-like activity of MoS₂ can be significantly enhanced due to the combination with TiO₂ NTs in return. Especially, the peroxidase-like activity of the TiO₂ NTs@MoS₂ nanocomposite can be further improved under the sunlight irradiation, rendering much more hydroxyl radical (•OH) generation. Accordingly, the as-obtained TiO₂ NTs@MoS₂ shows an outstanding antibacterial effect against drug-resistance extended spectrum β-lactamases producing Escherichia coli and methicillin-resistant Staphylococcus aureus under the visible light. In vivo wound healing test further confirms the high antimicrobial efficiency and good biocompatibility of the synergistic antimicrobial system.

Two-Dimensional Material-Based Colorimetric Biosensors: A Review

Two-dimensional (2D) materials such as graphene, graphene oxide, transition metal oxide, MXene and others have shown high potential for the design and fabrication of various sensors and biosensors due to their 2D layered structure and unique properties. Compared to traditional fluorescent, electrochemical, and electrical biosensors, colorimetric biosensors exhibit several advantages including naked-eye determination, low cost, quick response, and easy fabrication. In this review, we present recent advances in the design, fabrication, and applications of 2D material-based high-performance colorimetric biosensors. Potential colorimetric sensing mechanisms and optimal material selection as well as sensor fabrication are introduced in brief. In addition, colorimetric biosensors based on different 2D materials such as graphene, transition metal dichalcogenide/oxide, MXenes, metal-organic frameworks, and metal nanoplates for the sensitive detection of DNA, proteins, viruses, small molecules, metallic ions, and others are presented and discussed in detail. This work will be helpful for readers to understand the knowledge of 2D material modification, nanozymes, and the synthesis of hybrid materials; meanwhile, it could be valuable to promote the design, fabrication, and applications of 2D material-based sensors and biosensors in quick bioanalysis and disease diagnostics.

Recent Advances in Nucleic Acid Modulation for Functional Nanozyme

Nanozymes have the potential to replace natural enzymes, so they are widely used in energy conversion technologies such as biosensors and signal transduction (converting biological signals of a target into optical, electrical, or metabolic signals). The participation of nucleic acids leads nanozymes to produce richer interface effects and gives energy conversion events more attractive characteristics, creating what are called “functional nanozymes”. Since different nanozymes have different internal structures and external morphological characteristics, functional modulation needs to be compatible with these properties, and attention needs to be paid to the influence of nucleic acids on nanozyme activity. In this review, “functional nanozymes” are divided into three categories, (nanozyme precursor ion)/ (nucleic acid) self-assembly, nanozyme-nucleic acid irreversible binding, and nanozyme-nucleic acid reversible binding, and the effects of nucleic acids on modulation principles are summarized. Then, the latest developments of nucleic acid-modulated nanozymes are reviewed in terms of their use in energy conversion technology, and their conversion mechanisms are critically discussed. Finally, we outline the advantages and limitations of “functional nanozymes” and discuss the future development prospects and challenges in this field.

Recent progress in nanomaterial-based sensing of airborne viral and bacterial pathogens

Airborne pathogens are small microbes that can cause a multitude of diseases (e.g., the common cold, flu, asthma, anthrax, tuberculosis, botulism, and pneumonia). As pathogens are transmitted from infected hosts via a number of routes (e.g., aerosolization, sneezing, and coughing), there is a great demand to accurately monitor their presence and behavior. Despite such need, conventional detection methods (e.g., colony counting, immunoassays, and various molecular techniques) generally suffer from a number of demerits (e.g., complex, time-consuming, and labor-intensive nature). To help overcome such limitations, nanomaterial-based biosensors have evolved as alternative candidates to realize portable, rapid, facile, and direct on-site identification of target microbes. In this review, nano-biosensors developed for the detection of airborne pathogens are listed and discussed in reference to conventional options. The prospects for the development of advanced nano-biosensors with enhanced accuracy and portability are also discussed.

Two-Dimensional Material-Based Biosensors for Virus Detection

Viral infections are one of the major causes of mortality and economic losses worldwide. Consequently, efficient virus detection methods are crucial to determine the infection prevalence. However, most detection methods face challenges related to false-negative or false-positive results, long response times, high costs, and/or the need for specialized equipment and staff. Such issues can be overcome by access to low-cost and fast response point-of-care detection systems, and two-dimensional materials (2DMs) can play a critical role in this regard. Indeed, the unique and tunable physicochemical properties of 2DMs provide many advantages for developing biosensors for viral infections with high sensitivity and selectivity. Fast, accurate, and reliable detection, even at early infection stages by the virus, can be potentially enabled by highly accessible surface interactions between the 2DMs and the analytes. High selectivity can be obtained by functionalization of the 2DMs with antibodies, nucleic acids, proteins, peptides, or aptamers, allowing for specific binding to a particular virus, viral fingerprints, or proteins released by the host organism. Multiplexed detection and discrimination between different virus strains are also feasible. In this Review, we present a comprehensive overview of the major advances of 2DM-based biosensors for the detection of viruses. We describe the main factors governing the efficient interactions between viruses and 2DMs, making them ideal candidates for the detection of viral infections. We also critically detail their advantages and drawbacks, providing insights for the development of future biosensors for virus detection. Lastly, we provide suggestions to stimulate research in the fast expanding field of 2DMs that could help in designing advanced systems for preventing virus-related pandemics.

Human virus detection with graphene-based materials

Our recent experience of the COVID-19 pandemic has highlighted the importance of easy-to-use, quick, cheap, sensitive and selective detection of virus pathogens for the efficient monitoring and treatment of virus diseases. Early detection of viruses provides essential information about possible efficient and targeted treatments, prolongs the therapeutic window and hence reduces morbidity. Graphene is a lightweight, chemically stable and conductive material that can be successfully utilized for the detection of various virus strains. The sensitivity and selectivity of graphene can be enhanced by its functionalization or combination with other materials. Introducing suitable functional groups and/or counterparts in the hybrid structure enables tuning of the optical and electrical properties, which is particularly attractive for rapid and easy-to-use virus detection. In this review, we cover all the different types of graphene-based sensors available for virus detection, including, e.g., photoluminescence and colorimetric sensors, and surface plasmon resonance biosensors. Various strategies of electrochemical detection of viruses based on, e.g., DNA hybridization or antigen-antibody interactions, are also discussed. We summarize the current state-of-the-art applications of graphene-based systems for sensing a variety of viruses, e.g., SARS-CoV-2, influenza, dengue fever, hepatitis C virus, HIV, rotavirus and Zika virus. General principles, mechanisms of action, advantages and drawbacks are presented to provide useful information for the further development and construction of advanced virus biosensors. We highlight that the unique and tunable physicochemical properties of graphene-based nanomaterials make them ideal candidates for engineering and miniaturization of biosensors.

Colorimetric detection uranyl ions based on the enhanced peroxidase-like activity by GO adsorption

Based on the fact that uranyl ions (UO₂²⁺) adsorbed on GO can enhanced the peroxidase-like activity of graphene oxide (GO), a novel colorimetric strategy for visualizing quantitative determination of uranyl ions was established. The peroxidase-like activity of GO-UO₂²⁺ nanocomposites was assessed by catalyzing H₂O₂ oxidation of TMB to produce a distinct color reaction. A good linearity between the UO₂²⁺ concentration and absorption at 652 nm was acquired in the range of 5.90 × 10^-6 to 9.43 × 10^-4 M with a detection limit of 4.70 μM. This strategy was also successfully applied to determination of uranyl ions in environmental water samples.

Enhancement of the Peroxidase-Like Activity of Iodine-Capped Gold Nanoparticles for the Colorimetric Detection of Biothiols

A colorimetric assay was developed for the detection of biothiols, based on the peroxidase-like activity of iodine-capped gold nanoparticles (AuNPs). These AuNPs show a synergetic effect in the form of peroxidase-mimicking activity at the interface of AuNPs, while free AuNPs and iodine alone have weak catalytic properties. Thus, iodine-capped AuNPs possess good intrinsic enzymatic activity and trigger the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), leading to a change in color from colorless to yellow. When added to solution, biothiols, such as cysteine, strongly bind to the interface of AuNPs via gold-thiol bonds, inhibiting the catalytic activity of AuNPs, resulting in a decrease in oxidized TMB. Using this strategy, cysteine could be linearly determined, at a wide range of concentrations (0.5 to 20 μM), with a detection limit of 0.5 μM using UV-Vis spectroscopy. This method was applied for the detection of cysteine in diluted human urine.

Recent Progress of Nanozymes in the Detection of Pathogenic Microorganisms

Infectious diseases are among the world's principal health problems. It is crucial to develop rapid, accurate and cost-effective methods for the detection of pathogenic microorganisms. Recently, considerable progress has been achieved in the field of inorganic enzyme mimics (nanozymes). Compared with natural enzymes, nanozymes have higher stability and lower cost. More interestingly, their properties can be designed for various demands. Herein, we introduce the latest research progress on the detection of pathogenic microorganisms by using various nanozymes. We also discuss the current challenges of nanozymes in biosensing and provide some strategies to overcome these barriers.

A gold nanoparticle-intercalated mesoporous silica-based nanozyme for the selective colorimetric detection of dopamine

Highly dispersed aggregation-free gold nanoparticles intercalated into the walls of mesoporous silica (AuMS) were synthesized using thioether-functionalized silica as a nanozyme, which exhibited an excellent peroxidase mimic activity. The AuMS material was characterized via XRD, N₂ adsorption-desorption, FESEM, SEM-EDS particle mapping, TEM, and XPS. The peroxidase-like activity of the AuMS material was studied thoroughly, and the effect of pH and temperature was evaluated. The reproducibility of the peroxidase mimic activity and long-term stability of the AuMS catalyst were also studied. Furthermore, the AuMS catalyst was successfully utilized for the detection and quantification of dopamine, an important neurotransmitter, colorimetrically with a linear range of 10-80 μM and a limit of detection (LOD) value of 1.28 nM. The determination of dopamine concentration in commercially available dopamine hydrochloride injection showed high accuracy, good reproducibility, and high selectivity in the presence of uric acid, ascorbic acid, glucose, tryptophan, phenylalanine, and tyrosine.

Recent developments of nanoenzyme-based colorimetric sensors for heavy metal detection and the interaction mechanism

This work highlights the application and interaction mechanism of metal nanoparticles, metal oxides, metal sulfides, graphene-based nanomaterials and G-quadruplex, etc. in nanoenzyme-based colorimetric sensors.

AuNPs-LISA, an efficient detection assay for Opisthorchis viverrini (Ov) antigen in urine

The enzyme-linked immunosorbent assay (ELISA) is currently a powerful technique for the detection of Opisthorchis viverrini antigen (OvAg) in urine samples. However, its sensitivity and analysis time need to be improved. In the present study, we aimed to improve the signal enhancing system of traditional ELISA by using gold nanoparticles (AuNPs) with peroxidase-like activity on its surface instead of the horseradish peroxidase (HRP) system. The catalytic activity of the AuNPs probe can be boosted by the gold enhancing solution and the addition of ATP. The catalytic ability of the AuNPs probe depended on the probe and the H₂O₂ concentration. The proposed approach can reduce the number of the traditional ELISA steps with better detection sensitivity. Interestingly, the limit of detection (LOD) of the test was 23.4 ng mL^-1, substantially lower than the 93.8 ng mL^-1 for the traditional ELISA. The AuNPs-LISA assay showed higher sensitivity and specificity, 93.81% and 91.34%, respectively, compared to the traditional ELISA. The proposed assay was successfully applied for the detection of OvAg in urine samples. This will provide an effective tool for the detection, control and elimination of human opisthorchiasis.

Nanomaterials-Based Colorimetric Immunoassays

Colorimetric immunoassays for tumor marker detection have attracted considerable attention due to their simplicity and high efficiency. With the achievements of nanotechnology and nanoscience, nanomaterials-based colorimetric immunoassays have been demonstrated to be promising alternatives to conventional colorimetric enzyme-linked immunoassays. This review is focused on the progress in colorimetric immunoassays with the signal amplification of nanomaterials, including nanomaterials-based artificial enzymes to catalyze the chromogenic reactions, analyte-induced aggregation or size/morphology change of nanomaterials, nanomaterials as the carriers for loading enzyme labels, and chromogenic reactions induced by the constituent elements released from nanomaterials.

Inorganic Complexes and Metal-Based Nanomaterials for Infectious Disease Diagnostics

Infectious diseases claim millions of lives each year. Robust and accurate diagnostics are essential tools for identifying those who are at risk and in need of treatment in low-resource settings. Inorganic complexes and metal-based nanomaterials continue to drive the development of diagnostic platforms and strategies that enable infectious disease detection in low-resource settings. In this review, we highlight works from the past 20 years in which inorganic chemistry and nanotechnology were implemented in each of the core components that make up a diagnostic test. First, we present how inorganic biomarkers and their properties are leveraged for infectious disease detection. In the following section, we detail metal-based technologies that have been employed for sample preparation and biomarker isolation from sample matrices. We then describe how inorganic- and nanomaterial-based probes have been utilized in point-of-care diagnostics for signal generation. The following section discusses instrumentation for signal readout in resource-limited settings. Next, we highlight the detection of nucleic acids at the point of care as an emerging application of inorganic chemistry. Lastly, we consider the challenges that remain for translation of the aforementioned diagnostic platforms to low-resource settings.

Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes (II)

An updated comprehensive review to help researchers understand nanozymes better and in turn to advance the field.

Functional nanomaterials with unique enzyme-like characteristics for sensing applications

We highlight the recent developments in functional nanomaterials with unique enzyme-like characteristics for sensing applications.

Colorimetric determination of Hg2+ in environmental water based on the Hg2+-stimulated peroxidase mimetic activity of MoS2-Au composites

A colorimetric assay is described for sensitive determination of Hg²⁺ ions based on the MoS₂-Au composites as peroxidase mimetics, which are synthesized by microwave-assisted solvothermal method. The addition of Hg²⁺ stimulates their peroxidase-like activity, along with lower Michaelis constant toward the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) with H₂O₂, allowing the composites for direct determination of Hg²⁺. A broad linear response is obtained ranging from 20 nM to 20 μM with a detection limit (LOD) of 5 nM. The superior peroxidase-like activity is attributed to the large surface area of MoS₂ nanosheets and the synergistic catalytic effect of MoS₂ and Au. The Hg²⁺-stimulation effect implies the strong interaction between Hg²⁺ and MoS₂-Au, where the XPS results confirm the presence of metallic Hg⁰, indicative of an Au-Hg amalgam. This colorimetric assay is successfully applied for the determination of Hg²⁺ in environmental water (tap water and Yellow River water) with excellent selectivity over interfering cations.

Graphene-based nanomaterials in biosystems

Graphene-based nanomaterials have emerged as a novel type of materials with exceptional physicochemical properties and numerous applications in various areas. In this review, we summarize recent advances in studying interactions between graphene and biosystems. We first provide a brief introduction on graphene and its derivatives, and then discuss on the toxicology and biocompatibility of graphene, including the extracellular interactions between graphene and biomacromolecules, cellular studies of graphene, and in vivo toxicological effects. Next, we focus on various graphene-based practical applications in antibacterial materials, wound addressing, drug delivery, and water purification. We finally present perspectives on challenges and future developments in these exciting fields.

The Role of Nanomaterials and Nanotechnologies in Wastewater Treatment: a Bibliometric Analysis

Nanomaterials and nanotechnologies (NNs) have been shaping the wastewater treatment process unprecedentedly. Bibliometric methods are regarded as an indispensable light to guide direction in scientific domain. The present study aims to investigate the role of NNs in wastewater treatment with bibliometric techniques based on SCI databases from 1997 to 2016. Results showed that China (962), USA (324) and Iran (140) are the most productive countries. Chinese Academy of Sciences (149), Tongji University (49), and Harbin Institute of Technology (40) from China are the most contributive institutions. China and USA played central roles in cross-national cooperation, but the top three Chinese institutions displayed limited vitality in overseas communication. Rsc Advances (108) was the most productive journal followed by Desalination (97) and Desalination and Water Treatment (96). The research direction of NNs in wastewater treatment was bound up with new NNs. Novel preparation methods and nanostructures were powerful impetus for its progress. Nanomaterials like graphene, nanotube, magnetic nanoparticle, and silver nanoparticle were hotpots in this field. Current and potential application of NNs in wastewater treatment as well as challenges were reviewed based on bibliometric results. This study also provided researchers future-minded advice about research topic selection.

Enhanced Plasmonic Biosensors of Hybrid Gold Nanoparticle-Graphene Oxide-Based Label-Free Immunoassay

In this study, we propose a modified gold nanoparticle-graphene oxide sheet (AuNP-GO) nanocomposite to detect two different interactions between proteins and hybrid nanocomposites for use in biomedical applications. GO sheets have high bioaffinity, which facilitates the attachment of biomolecules to carboxyl groups and has led to its use in the development of sensing mechanisms. When GO sheets are decorated with AuNPs, they introduce localized surface plasmon resonance (LSPR) in the resonance energy transfer of spectral changes. Our results suggest a promising future for AuNP-GO-based label-free immunoassays to detect disease biomarkers and rapidly diagnose infectious diseases. The results showed the detection of antiBSA in 10 ng/ml of hCG non-specific interfering protein with dynamic responses ranging from 1.45 nM to 145 fM, and a LOD of 145 fM. Considering the wide range of potential applications of GO sheets as a host material for a variety of nanoparticles, the approach developed here may be beneficial for the future integration of nanoparticles with GO nanosheets for blood sensing. The excellent anti-interference characteristics allow for the use of the biosensor in clinical analysis and point-of-care testing (POCT) diagnostics of rapid immunoassay products, and it may also be a potential tool for the measurement of biomarkers in human serum.

Neuroprotective effect of gold nanoparticles composites in Parkinson's disease model

Parkinson's disease (PD) is second most common neurodegenerative disorder worldwide. Although drugs and surgery can relieve the symptoms of PD, these therapies are incapable of fundamentally treating the disease. For PD patients, over-expression of α-synuclein (SNCA) leads to the death of dopaminergic neurons. This process can be prevented by suppressing SNCA over-expression through RNA interference. Here, we successfully synthesized gold nanoparticles (GNP) composites (CTS@GNP-pDNA-NGF) via the combination of electrostatic adsorption and photochemical immobilization, which could load plasmid DNA (pDNA) and target specific cell types. GNP was transfected into cells via endocytosis to inhibiting the apoptosis of PC12 cells and dopaminergic neurons. Simultaneously, GNP composites are also used in PD models in vivo, and it can successfully cross the blood-brain barrier by contents of GNP in the mice brain. In general, all the works demonstrated that GNP composites have good therapeutic effects for PD models in vitro and in vivo.

Unveiling the role of ATP in amplification of intrinsic peroxidase-like activity of gold nanoparticles

Peroxidase enzyme-like activity of gold nanoparticles (AuNPs) is currently being investigated for the potential application in the several realms of biomedicines. However, little is explored about the peroxidase activity of AuNPs decorated with different surface charges. It is well-documented that the catalytic activity and the interaction with mammalian cells are significantly different among AuNPs carrying different surface charges. We have recently reported that ATP enhances the peroxidase-like activity of AuNPs and iron oxide nanoparticles. However, a comprehensive and systematic study to reveal the role of surface charge on nanoparticles peroxidase-like activity has not been studied. In this work, we have shown that AuNPs coated with PEG (PEG AuNPs), citrate (citrate AuNPs) or CTAB (CTAB AuNPs) exhibit varying peroxidase-like activity and the boosting effect imparted by ATP was also different. We found that the peroxidase-like activity of PEG AuNPs and citrate AuNPs is dependent on hydroxyl radical formation, whereas CTAB AuNPs did not show any significant activity under the same experimental conditions. We also studied the boosting effect of ATP on the peroxidase-like activity of PEG and citrate AuNPs. Although the use of ATP resulted in enhanced peroxidase-like activity; however, contrary to the expectation, it did not facilitate the enhanced production of hydroxyl radical. In further studies, we found that the likely mechanism of boosting effect by ATP is the stabilization of oxidized TMB after peroxidase reaction. ATP imparts stabilization to the oxidized TMB produced due to PEG AuNPs, citrate AuNPs as well as HRP.

Synergistic antiviral effect of curcumin functionalized graphene oxide against respiratory syncytial virus infection

The diseases attributable to viruses remain a global burden. The respiratory syncytial virus (RSV), which is considered as the major viral pathogen of the lower respiratory tract of infants, has been implicated in severe lung disease. In this contribution, we developed a β-cyclodextrin (CD) functionalized graphene oxide (GO) composite, which displayed excellent antiviral activity and could load curcumin efficiently. RSV, a negative-sense single-stranded enveloped RNA virus, was employed as a model virus to investigate the antiviral activity of multifunctional GO. Proved by the tissue culture infectious dose assay and immunofluorescence assay, the curcumin loaded functional GO was confirmed with highly efficient inhibition for RSV infection and great biocompatibility to the host cells. The results showed that the composite could prevent RSV from infecting the host cells by directly inactivating the virus and inhibiting the viral attachment, and possessed prophylactic and therapeutic effects towards the virus. Our data indicate that the composite may provide new insights into antiviral therapy for RSV infection.