Size-controlled preparation of peroxidase-like graphene-gold nanoparticle hybrids for the visible detection of norovirus-like particles

Prospects for the use of nanozyme-based electrochemical and colorimetric sensors for antibiotic detection

Rapid and accurate monitoring of residual antibiotic concentrations is of great importance in environmental monitoring. Therefore, research is active to develop new methods for analyzing antibiotics. Biosensors, including those based on nanozymes, are very successful for antibiotic analysis. Nanozymes (nanomaterials with enzymelike activity) have emerged as a promising solution offering improved stability, cost-effectiveness, and versatility, as compared with natural enzymes. The use of nanozyme-based electrochemical and colorimetric sensors for detecting antibiotics remains underexplored. This review presents the main prospects for the use of electrochemical and colorimetric nanozyme sensor systems to detect antibiotics. It identifies major shortcomings of these platforms and ways to deal with them. Finally, it highlights the advantages of these sensors over other systems and explains the main mechanisms of signal generation for antibiotic detection.

A novel strategy for Escherichia coli detection in raw beef in combination with click chemistry

Bacteria-assisted click chemistry for enhanced nanozyme-based Escherichia coli (E. coli) detection. The size and shape of the alkyne-modified Fe3O4@Au NPs were 110 nm and urchin-like, respectively. The azide-functionalized Au QDs were spherical in shape, and their size was ~5 nm. The absorbance and emission peaks of Fe3O4@Au NPs and Au QDs were located at 526 nm and 520 nm, respectively. The nanozymatic activity of both materials significantly improved in the presence of Cu2+, E. coli, and 3,3',5,5'-tetramethylbenzidine (TMBZ)/H2O2 mixture. Here, the bacterial metabolic product Cu+ was utilized to trigger the click reaction between alkyne-modified Fe3O4@Au NPs and azide-functionalized Au QDs which enables magnetic separation. The calculated limits of detection (LODs) of E. coli were as high as 5 CFU/mL and 25 CFU/mL in the PBS buffer and spiked raw meat samples, respectively. The proposed nanozymatic E. coli assay was selective in the presence of other bacteria.

Dual-mode exosome detection leveraging a nanozyme-active artificial receptor: PDA@Fe@Zn-based nucleic acid aptamer sensor

Exosomes, extracellular vesicles crucial for intercellular communication, are emerging as significant biomarkers for disease diagnosis, especially in cancer. This study presented a dual-mode exosome detection platform using polydopamine microspheres doped with iron and zinc ions (PDA@Fe@Zn). These materials served as both artificial receptors for nucleic acid aptamers and nanozymes with peroxidase-like activity. By integrating colorimetric and fluorescence detection, the platform enables cross-validation of results. PDA@Fe@Zn nanozymes catalyzed the TMB-H2O2 reaction under acidic conditions, producing a colorimetric signal proportional to exosome concentration. Concurrently, the fluorescence of FAM-labeled aptamers was dynamically quenched by PDA@Fe@Zn and the presence of exosomes restores the fluorescence signal for a "turn-on" detection mode. DNase I amplified detection signals by cleaving bound exosomes for multiple cycles, achieving a limit of detection (LOD) of 4.7 × 104 particles/mL for colorimetric detection and 2.2 × 104 particles/mL for fluorescence detection. Notably, the colorimetric platform revealed that the relative expression of the CD63 protein on exosomes from breast cancer cells MCF-7 and MDA-MB-231 was approximately 2.7 and 2.4 times higher, respectively, than in normal breast cells MCF-10A; similar fold changes of 2.9 and 2.4 were observed with fluorescence detection, underscoring the robustness of the dual-mode system. The platform demonstrated rapid detection (within 30 min), high sensitivity, strong anti-interference capability, and the ability to distinguish exosomes from cancerous and normal cells effectively.

Innovative strategies for enhancing AuNP-based point-of-care diagnostics: Focus on coronavirus detection

Highly pathogenic coronaviruses have consistently threatened humanity, encompassing SARS-CoV, MERS-CoV, SARS-CoV-2 and others. Swift detection and accurate diagnosis play a crucial role in promptly identifying high-risk populations, enabling timely intervention, and effectively breaking the transmission chain to reduce casualties. However, the diagnostic "gold standard" reverse transcription-polymerase chain reaction (RT-PCR) failed to meet the overwhelming demand during the pandemic due to insufficient equipment and trained personnel, impeding the effective control of viral spread. Undoubtedly, there is an urgent need for the development of convenient, rapid, and sensitive point-of-care (POC) diagnostic technology. Gold nanoparticles (AuNPs) satisfy the substantial market demand for biosensors owing to their exceptional optical properties and stability. In this comprehensive review, we summarize the potential advantages of AuNPs in visual solution colorimetry and lateral flow assays (LFAs) for the diagnosis of COVID-19. We delve into the techniques for enhancing LFA signals, with the goal of increasing both detection sensitivity and specificity. Furthermore, we include the application of smartphones for unbiased and objective interpretation of results. The examples presented in this review are anticipated to inspire researchers in designing AuNPs biosensors to address current and potential outbreaks of infectious diseases in the future.

Fc-binding M13 phage-enhanced electrochemical biosensors for influenza virus detection

The importance of in vitro diagnostics (IVDs) has significantly increased, driving the demand for rapid and sensitive diagnostic platforms. Molecular probes play a pivotal role in improving the sensitivity and accuracy of IVDs because of their target-specific signal transduction capabilities. Antibodies, which are commonly used as detection probes, face several challenges, including limited stability, high production costs, and low signal output. In this study, we developed an engineered M13 bacteriophage-based detection system for influenza virus hemagglutinin (HA) using an Electrical ImmunoSorbent Assay (El-ISA). Our design featured Fc-binding motifs on pIII to enable conjugation with target-specific antibodies, along with signal-enhancing biotin modifications on pVIII. The resulting Fc-binding phage probes combined with anti-HA antibodies significantly improved the signal intensity by up to 6.0-fold. This approach enabled the detection of viral proteins in lysate samples at concentrations as low as 44.9 pfu/mL. These findings demonstrated the potential of Fc-binding phage probes as versatile platforms that synergize antibody specificity with enhanced signal transduction. This strategy not only enhances the sensitivity of antibody-based diagnostics but also expands their applicability in diverse research and diagnostic settings.

Norovirus detection technologies: From conventional methods to innovative biosensors

The norovirus (NoV), known for its high contagion rate, is the leading cause of acute gastroenteritis. The development of a NoV vaccine is hindered by significant antigenic variation, lack of suitable models, unknown vaccine protection duration, limited human challenge studies, complex performance patterns, and the absence of a reliable in vitro cultivation system, making prevention, early detection, and control the only effective measures to mitigate outbreaks. This review aims to discuss about several norovirus biosensor for point-of-care analysis. Several innovative biosensors have been developed, including techniques such as electrochemical NoV biosensors, colorimetric NoV biosensors, fluorescence NoV biosensors, CRISPR-based NoV biosensors, and other NoV biosensors. These approaches have detected norovirus in biological samples with high sensitivity and specificity. This biosensing technique holds significant promise, not only in improving the speed and accuracy of diagnostic processes but also in strengthening the global response to norovirus infections, thereby underscoring its pivotal role in public health and disease prevention.

Research progress on the synthesis, performance regulation, and applications of Prussian blue nanozymes

Nanocatalytic medicine offers a novel solution to address the issues of low efficacy, potential side effects, and the development of drug resistance associated with traditional therapies. Therefore, developing highly efficient and durable nanozymes is of great significance for treating diseases related to oxidative stress. In recent years, prussian blue nanoparticles (PBNPs) have been demonstrated to possess multiple enzyme-like catalytic activities and are thus referred to as prussian blue nanozymes (PBNZs). Their excellent biocompatibility and biodegradability make PBNZs promising candidates as biomedical materials. Due to their remarkable catalytic activities, PBNZs have shown great potential in various biomedical applications, such as heavy metal detoxification, antioxidative damage, and anticancer therapies. This paper systematically summarizes the Synthetic strategies of PBNZs, analyzes the regulatory factors of their catalytic performance, and highlights the corresponding modulation methods. Furthermore, the biomedical applications of PBNZs are also reviewed. This study aims to provide researchers with insights and inspirations for the design and preparation of high-performance PBNZs.

Advances in nanozymes with peroxidase-like activity for biosensing and disease therapy applications

Natural enzymes are crucial in biological systems and widely used in biomedicine, but their disadvantages, such as insufficient stability and high cost, have limited their widespread application. Since discovering the enzyme-like activity of Fe3O4 nanoparticles, extensive research progress in diverse nanozymes has been made with their in-depth investigation, resulting in rapid development of related nanotechnologies. Nanozymes can compensate for the defects of natural enzymes and show higher stability with lower costs. Among them, peroxidase (POD)-like nanozymes have attracted extensive attention in biomedical applications owing to their efficient catalytic performance and diverse structures. This review explores different types of nanozymes with POD-like activity and discusses their activity regulation, particularly emphasizing their latest development trends and advances in biosensing and disease treatment. Finally, the challenges and prospects for the development of POD-like nanozymes and their potential future applications in the biomedical field are also provided.

Hybrid paper/PDMS microfluidic device integrated with RNA extraction and recombinase polymerase amplification for detection of norovirus in foods

Human norovirus (HuNoV) is recognized as the leading causative agent of foodborne outbreaks of epidemic gastroenteritis. Consequently, there is a high demand for developing point-of-care testing for HuNoV. We developed an origami microfluidic device that facilitates rapid detection of murine norovirus 1 (MNV-1), a surrogate for HuNoV, encompassing the entire process from sample preparation to result visualization. This process includes RNA absorption via a paper strip, RNA amplification using recombinase polymerase amplification (RPA), and a lateral flow assay for signal readout. The on-chip detection of MNV-1 was completed within 35 min, demonstrating 100% specificity to MNV-1 in our settings. The detection limit of this microfluidic device for MNV-1 was 200 PFU/mL, comparable to the in-tube RPA reaction. It also successfully detected MNV-1 in lettuce and raspberries at concentrations of 170 PFU/g and 230 PFU/g, respectively, without requiring extra concentration steps. This device demonstrates high compatibility with isothermal nucleic acid amplification and holds significant potential for detecting foodborne viruses in agri-food products in remote and resource-limited settings.

IMPORTANCE

HuNoV belongs to the family of Caliciviridae and is a leading cause of acute gastroenteritis that can be transmitted through contaminated foods. HuNoV causes around one out of five cases of acute gastroenteritis that lead to diarrhea and vomiting, placing a substantial burden on the healthcare system worldwide. HuNoV outbreaks can occur when food is contaminated at the source (e.g., wild mussels exposed to polluted water), on farms (e.g., during crop cultivation, harvesting, or livestock handling), during packaging, or at catered events. The research outcomes of this study expand the approaches of HuNoV testing, adding value to the framework for routine testing of food products. This microfluidic device can facilitate the monitoring of HuNoV outbreaks, reduce the economic loss of the agri-food industry, and enhance food safety.

Copper oxide nanosheets as an effective nanozyme with haloperoxidase-like activity for the colorimetric detection of H2O2 and glucose

Copper oxide nanosheets (CuO NSs) have been successfully obtained by exploiting an effective one-step approach of sugar-blowing method followed by calcination. The nanosheets were characterized by several techniques like X-ray powder diffraction (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Impressively, CuO NSs display haloperoxidase (HPO) like catalytic activity which catalyses the oxidation of chloride ions by H2O2 giving rise to reactive chlorine species (RCS). A sensitive and selective colorimetric sensor was then demonstrated via the oxidation of chromogenic substrate 3,3',5,5'- tetramethylbenzidine (TMB) by the novel nanoenzyme CuO NSs through the generation of RCS for H2O2 and glucose detection with limit of detection of 109 nM and 21 nM in the linear ranges of 4.6 µM to 769 µM and 0.22 µM to 19.57 µM respectively. Additionally, the methodology is validated for the analysis of glucose in real samples.

Sensitive Electrochemical and Thermal Detection of Human Noroviruses Using Molecularly Imprinted Polymer Nanoparticles Generated against a Viral Target

Norovirus (NoV) is the predominant cause of foodborne illness globally; current detection methods are typically expensive, have inadequate sensitivities, and utilize biological receptors with poor stability. Therefore, accurate, cost-effective, and highly stable detection methods are needed to screen for NoV in foods. We developed molecularly imprinted polymer nanoparticles (nanoMIPs) to detect NoV using a small target epitope (12 amino acids) with a solid-phase synthesis approach. The performance of three batches of nanoMIPs with varying monomer compositions (nanoMIP-1, -2, and -3) were compared both experimentally and computationally. Surface plasmon resonance examined nanoMIP binding affinity to norovirus virus-like particles (NoV-LPs), whereby nanoMIP-1 had the lowest KD value of 0.512 μM. This is significant, as traditional targets for generation of norovirus ligands previously reported were generated against drastically larger norovirus capsid segments that have limitations in ease of production. Further, an electrochemical sensor was developed by covalently attaching the nanoMIPs to glassy carbon electrodes. In agreement with our predictions from density functional theory simulations, electrochemical impedance spectroscopy showed a sensitive response toward NoV-LPs for nanoMIP batches tested; however, nanoMIP-1 was optimal, with an excellent detection limit of 3.4 pg/mL (1.9 × 105 particles/mL). Due to its exceptional performance, nanoMIP-1 was immobilized to screen-printed electrodes and utilized within a thermal sensor, where it exhibited a low detection limit of 6.5 pg/mL (3.7 × 105 particles/mL). Crucially, we demonstrated that nanoMIP-1 could detect NoV in real food samples (romaine lettuce) by using electrochemical and thermal sensors. Consequently, the study highlights the exceptional potential of nanoMIPs to replace traditional biological materials (e.g., antibodies) as sensitive, versatile, and highly stable receptors within NoV sensors.

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.

Ni-Pt nanozyme-mediated relaxation and colorimetric sensor for dual-modality detection of norovirus

An NiPt nanozyme-mediated relaxation and colorimetric sensor is developed for dual-modality detection of norovirus (NoV). The relaxation modality is based on the "catalase-like" activity of the NiPt nanozyme, which adjusts the hydrogen peroxide (H2O2) mediated Fe (II)/Fe(III) conversion, thereby changing the relaxation signal. Poly-γ-glutamic acid (MW ≈ 1w) can enhance the relaxivity of Fe(III) (r1 = 7.11 mM-1 s-1; r2 = 8.94 mM-1 s-1). The colorimetric modality exploits the "peroxidase-like" activity of the NiPt nanozyme, which can catalyze the oxidation of colorless 3, 3', 5, 5'-tetramethylbenzidine (TMB) to blue oxTMB in H2O2. Under optimal conditions, the relaxation modality exhibits a wide working range (1.0 × 101-1.0 × 104 fM) and a limit of detection (LOD) of 4.7 fM (equivalent to 2820 copies/μL). The spiked recoveries range from 99.593 to 106.442 %, and the relative standard deviation (RSD) is less than 5.124 %. The colorimetric modality exhibited the same working range with a lower LOD of 2.9 fM (equivalent to 1740 copies/μL) and an RSD of less than 2.611 %. Additionally, the recombinase polymerase amplification reaction enabled the detection of low NoV levels in food samples with a working range of 102-106 copies/mL and LOD of 102 copies/mL. The accuracy of the sensor in the analysis of spiked samples is consistent with the gold standard method (real-time quantitative reverse transcription-polymerase chain reaction), demonstrating the high accuracy and practical utility of the sensor.

Multienzyme-Like Nanozymes: Regulation, Rational Design, and Application

Nanomaterials with more than one enzyme-like activity are termed multienzymic nanozymes, and they have received increasing attention in recent years and hold huge potential to be applied in diverse fields, especially for biosensing and therapeutics. Compared to single enzyme-like nanozymes, multienzymic nanozymes offer various unique advantages, including synergistic effects, cascaded reactions, and environmentally responsive selectivity. Nevertheless, along with these merits, the catalytic mechanism and rational design of multienzymic nanozymes are more complicated and elusive as compared to single-enzymic nanozymes. In this review, the multienzymic nanozymes classification scheme based on the numbers/types of activities, the internal and external factors regulating the multienzymatic activities, the rational design based on chemical, biomimetic, and computer-aided strategies, and recent progress in applications attributed to the advantages of multicatalytic activities are systematically discussed. Finally, current challenges and future perspectives regarding the development and application of multienzymatic nanozymes are suggested. This review aims to deepen the understanding and inspire the research in multienzymic nanozymes to a greater extent.

Enhanced Nanozymatic Activity on Rough Surfaces for H2O2 and Tetracycline Detection

The needless use of tetracyclines (TCs) in foodstuffs is a huge health concern in low- and middle-income and Arab countries. Herein, a sensitive and faster monitoring system for H2O2 and TCs is proposed, utilizing the large surface-to-volume ratio of a non-spherical gold nanoparticle/black phosphorus nanocomposite (BP-nsAu NPs) for the first time. BP-nsAu NPs were synthesized through a single-step method that presented nanozymatic activity through 3,3',5,5'-Tetramethylbenzidine (TMB) oxidation while H2O2 was present and obeyed the Michaelis-Menten equation. The nanozymatic activity of the BP-nsAu NPs was enhanced 12-fold and their detection time was decreased 83-fold compared to conventional nanozymatic reactions. The proposed method enabled us to quantify H2O2 with a limit of detection (LOD) value of 60 nM. Moreover, target-specific aptamer-conjugated BP-nsAu NPs helped us detect TCs with an LOD value of 90 nM. The present strategy provides a proficient route for low-level TC monitoring in real samples.

Electrochemical assisted enhanced nanozymatic activity of functionalized borophene for H2O2 and tetracycline detection

This study unveils the electrochemically-enhanced nanozymatic activity exhibited by borophene during the reaction of 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2. Herein, the surface of the pristine borophene was first modified with the addition of thiocyanate groups to improve hydroxyl radical (•OH) scavenging activity. Then, the oxidation reaction of TMB was accelerated under applied electrochemical potential. Both factors significantly improved the detection limit and drastically decreased the detection time. DPPH testing revealed that the radical scavenging nature of borophene was more than 70%, boosting its catalytic activity. In the presence of H2O2, borophene catalyzed the oxidation of TMB and produced a blue-colored solution that was linearly correlated with the concentration of H2O2 and allowed for the detection of H2O2 up to 38 nM. The present finding was further extended to nanozymatic detection of tetracyclines (TCs) using a target-specific aptamer, and the results were colorimetrically quantifiable up to 1 μM with a LOD value of 150 nM. Moreover, transferring the principles of the discussed detection method to form a portable and disposable paper-based system enabled the quantification of TCs up to 0.2 μM. All the sensing experiments in this study indicate that the nanozymatic activity of borophene has significantly improved under electrochemical potential compared to conventional nanozyme-based colorimetric detection. Hence, the present discovery of electrochemically-enhanced nanozymatic activity would be promising for various sensitive and time-dependent colorimetric sensor development initiatives in the future.

Mesoporous silica-stabilized magnetite nanoparticles with peroxidase-like activities for sensitively detecting cholesterol in animal-derived foods

Sensitive detection of cholesterol in animal-derived foods is crucial for maintaining human healthy diets. In this study, an elegant approach utilizing inorganic nanozyme-based magnetic mesoporous silica nanoparticles (MMSNs) for the highly sensitive detection of cholesterol in animal-derived food products was reported. The results revealed the fabricated MMSNs exhibited remarkably intrinsic peroxidase (POD)-like catalytic activities with improved affinity, and the catalytic behavior aligned well with Michaelis-Menten equation. In addition, the data indicated that the MMSNs enabled visual colorimetric detection of cholesterol with a remarkably low detection limit of 7.12 μM by combining catalytic oxidation with cholesterol oxidase (ChOx). Furthermore, the prepared MMSNs were successfully employed for assessing cholesterol content in milk and egg yolk samples, indicating potential applications for cholesterol detection in animal-derived foods in future.

Micro- and nanosystems for the detection of hemorrhagic fever viruses

Hemorrhagic fever viruses (HFVs) are virulent pathogens that can cause severe and often fatal illnesses in humans. Timely and accurate detection of HFVs is critical for effective disease management and prevention. In recent years, micro- and nano-technologies have emerged as promising approaches for the detection of HFVs. This paper provides an overview of the current state-of-the-art systems for micro- and nano-scale approaches to detect HFVs. It covers various aspects of these technologies, including the principles behind their sensing assays, as well as the different types of diagnostic strategies that have been developed. This paper also explores future possibilities of employing micro- and nano-systems for the development of HFV diagnostic tools that meet the practical demands of clinical settings.

Molybdenum Disulfide-Integrated Iron Organic Framework Hybrid Nanozyme-Based Aptasensor for Colorimetric Detection of Exosomes

Tumor-derived exosomes are considered as a potential marker in liquid biopsy for malignant tumor screening. The development of a sensitive, specific, rapid, and cost-effective detection strategy for tumor-derived exosomes is still a challenge. Herein, a visualized and easy detection method for exosomes was established based on a molybdenum disulfide nanoflower decorated iron organic framework (MoS2-MIL-101(Fe)) hybrid nanozyme-based CD63 aptamer sensor. The CD63 aptamer, which can specifically recognize and capture tumor-derived exosomes, enhanced the peroxidase activity of the hybrid nanozyme and helped to catalyze the 3,3',5,5'-tetramethylbenzidine (TMB)-H2O2 system to generate a stronger colorimetric signal, with its surface modification on the hybrid nanozyme. With the existence of exosomes, CD63 aptamer recognized and adsorbed them on the surface of the nanozyme, which rescued the enhanced peroxidase activity of the aptamer-modified nanozyme, resulting in a deep-to-moderate color change in the TMB-H2O2 system where the change is visible and can be monitored with ultraviolet-visible spectroscopy. In the context of optimal circumstances, the linear range of this exosome detection method is measured to be 1.6 × 104 to 1.6 × 106 particles/μL with a limit of detection as 3.37 × 103 particles/μL. Generally, a simple and accessible approach to exosome detection is constructed, and a nanozyme-based colorimetric aptamer sensor is proposed, which sheds light on novel oncological biomarker measurements in the field of biosensors.

Recent Advances in Colorimetric Tests for the Detection of Infectious Diseases and Antimicrobial Resistance

Diagnosis of infection-causing microorganisms with sensitive, rapid, selective and economical diagnostic tests is critical to start the right treatment. With these tests, the spread of infections can be prevented. In addition to that, the detection of antimicrobial resistance also makes a significant contribution to public health. In recent years, different types of diagnostic tests have been developed as alternatives to traditional diagnostic tests used in clinics. In particular, colorimetric tests, which minimize the need for an instrument, have advantages owing to their cost effectiveness, rapid response and naked-eye detection and practical use. In this review, we especially focused on pH indicators and nanomaterial-based colorimetric tests in detection of infection-causing microorganisms and antimicrobial resistance.

Advances in Nanozymes as a Paradigm for Viral Diagnostics and Therapy

Over the past few decades, humankind has constantly encountered new viral species that create havoc in the socioeconomic balance worldwide. Among the method to combat these novel viral infections, fast and point-of-care diagnosis is of prime importance to contain the spreading of viral infections. However, most sensitive diagnostic systems for viral infections are time-consuming and require well-trained professionals, making it difficult for the patients. In recent years nanozymes emerged as promising therapeutic and fast diagnostic tools due to their multienzyme-like catalytic performance. Nanozymes can be designed using inorganic or organic components with tailorable physicochemical surface properties, enabling the attachment of various molecules and species on the surface of the nanozyme for specific recognition. In addition to the composition, the multienzyme-like catalytic performance can be modulated by the shape and size of the nanoparticles. Due to their multicatalytic abilities, nanozymes can be used for fast diagnosis and therapy for viral infections. Here we attempt to focus on the insights and recent explorations on the advances in designing various types of nanozymes as a theranostic tool for viral infections. Thus, this review intends to generate interest in the clinical translation of nanozymes as a theranostic tool for viral infections by providing knowledge about the multidisciplinary potential of nanozyme. SIGNIFICANCE STATEMENT: The multienzyme-like properties of nanozymes suggest their role in diagnosing and treating various diseases. Although the potential roles of nanozymes for various viral infections have been studied in the last few decades, no review provides recent explorations on designing various types of nanozymes for the detection and treatment of viral infections. This review provides insights into designing nanozymes to diagnose and treat viral infections, assisting future researchers in developing clinically translatable nanozymes to combat novel viral infections.

Mn3O4 nanoparticles decorated porous reduced graphene oxide with excellent oxidase-like activity for fast colorimetric detection of ascorbic acid

Mn₃O₄ nanoparticles composed of porous reduced graphene oxide nanosheets (Mn₃O₄@p-rGO) with enhanced oxidase-like activity were successfully fabricated through an in-situ approach for fast colorimetric detection of ascorbic acid (AA). The residual Mn²⁺ in the GO suspension of Hummers method was directly reused as the manganese source, improving the atom utilization efficiency. Benefiting from the uniform distribution of Mn₃O₄ nanoparticles on the surface of p-rGO nanosheets, the nanocomposite exhibited larger surface area, more active sites, and accelerated electron transfer efficiency, which enhanced the oxidase-like activity. Mn₃O₄@p-rGO nanocomposite efficiently activate dissolved O₂ to generate singlet oxygen (¹O₂), leading to high oxidation capacity toward the substrate 3,3',5,5'-tetramethylbenzidine (TMB) without the extra addition of H₂O₂. Furthermore, the prominent absorption peak of the blue ox-TMB at 652 nm gradually decreased in the presence of AA, and a facile and fast colorimetric sensor was constructed with a good linear relationship (0.5-80 μM) and low LOD (0.278 μM) toward AA. Owing to the simplicity and excellent stability of the sensing platform, its practical application for AA detection in juices has shown good feasibility and reliability compared with HPLC and the 2, 4-dinitrophenylhydrazine colorimetric method. The oxidase-like Mn₃O₄@p-rGO provides a versatile platform for applications in food testing and disease diagnosis.

Synthesis and characterization of Au-decorated graphene oxide nanocomposite for magneto-electrochemical detection of SARS-CoV-2 nucleocapsid gene

Fast and effective diagnosis is the first step in monitoring the current coronavirus 2 (CoV-2) pandemic. Herein, we establish a simple and sensitive electrochemical assay using magnetic nanocomposite and DNA sandwich probes to rapidly quantify the CoV-2 nucleocapsid (N) gene down to the 0.37 fM level. This assay uses a pair of specific DNA probes. The capture probe is covalently conjugated to Au-decorated magnetic reduced graphene oxide (AMrGO) nanocomposite for efficiently capturing target RNA. In contrast, the detection probe is linked to peroxidase for signal amplification. The probes target the COV-2 gene, allowing for specific magnetic separation, enzymatic signal amplification, and subsequent generation of voltammetric current with a total assay time of 45 min. The developed biosensor has high selectivity and can discriminate non-specific gene sequences. Synthetic COV-2 N-gene can be detected efficiently in serum and saliva, while 1-bp mismatch gene yielded a low response. The performance of the genosensor was good in an extensive linear range of 5 aM-50 pM. For synthetic N-gene, we achieved the detection limit of 0.37, 0.33, and 0.19 fM in human saliva, urine, and serum. This simple, selective, and sensitive genosensor could have various genetics-based biosensing and diagnostic applications.

Current decontamination challenges and potentially complementary solutions to safeguard the vulnerable seafood industry from recalcitrant human norovirus in live shellfish: Quo Vadis?

Safeguarding the seafood industry is important given its contribution to supporting our growing global population. However, shellfish are filter feeders that bioaccumulate microbial contaminants in their tissue from wastewater discharged into the same coastal growing environments leading to significant human disease outbreaks unless appropriately mitigated. Removal or inactivation of enteric viruses is very challenging particularly as human norovirus (hNoV) binds to specific histo-blood ligands in live oyster tissue that are consumed raw or lightly cooked. The regulatory framework that sets out use of clean seawater and UV disinfection is appropriate for bacterial decontamination at the post-harvest land-based depuration (cleaning) stage. However, additional non-thermal technologies are required to eliminate hNoV in live shellfish (particularly oysters) where published genomic studies report that low-pressure UV has limited effectiveness in inactivating hNoV. The use of the standard genomic detection method (ISO 15, 216-1:2017) is not appropriate for assessing the loss of infectious hNoV in treated live shellfish. The use of surrogate viral infectivity methods appear to offer some insight into the loss of hNoV infectiousness in live shellfish during decontamination. This paper reviews the use of existing and potentially other combinational treatment approaches to enhance the removal or inactivation of enteric viruses in live shellfish. The use of alternative and complementary novel diagnostic approaches to discern viable hNoV are discussed. The effectiveness and virological safety of new affordable hNoV intervention(s) require testing and validating at commercial shellfish production in conjunction with laboratory-based research. Appropriate risk management planning should encompass key stakeholders including local government and the wastewater industry. Gaining a mechanistic understanding of the relationship between hNoV response at molecular and structural levels in individually treated oysters as a unit will inform predictive modeling and appropriate treatment technologies. Global warming of coastal growing environments may introduce additional contaminant challenges (such as invasive species); thus, underscoring need to develop real-time ecosystem monitoring of growing environments to alert shellfish producers to appropriately mitigate these threats.

Non-spherical gold nanoparticles enhanced fluorescence of carbon dots for norovirus-like particles detection

BACKGROUND

Norovirus is a common pathogen that causes foodborne outbreaks every year and the increasing number of deaths caused by it has become a substantial concern in both developed and underdeveloped countries. To date, no vaccines or drugs are able to control the outbreak, highlighting the importance of finding specific, and sensitive detection tools for the viral pathogen. Current diagnostic tests are limited to public health laboratories and/or clinical laboratories and are time-consuming. Hence, a rapid and on-site monitoring strategy for this disease is urgently needed to control, prevent and raise awareness among the general public.

RESULTS

The present study focuses on a nanohybridization technique to build a higher sensitivity and faster detection response to norovirus-like particles (NLPs). Firstly, the wet chemical-based green synthesis of fluorescent carbon quantum dots and gold nanoparticles (Au NPs) has been reported. Then, a series of characterization studies were conducted on the synthesized carbon dots and Au NPs, for example, high-resolution transmission emission microscopy, fluorescence spectroscopy, fluorescence life-lime measurement, UV-visible spectroscopy, and X-ray diffraction (XRD). The fluorescence emission of the as-synthesized carbon dots and the absorption of Au NPs were located at 440 nm and 590 nm, respectively. Then, the plasmonic properties of Au NPs were utilized to enhance the fluorescence emission of carbon dots in the presence of NLPs in human serum. Here, the enhanced fluorescence response was linearly correlated up to 1 μg mL^-1. A limit of detection (LOD) value was calculated to be 80.3 pg mL^-1 demonstrating that the sensitivity of the proposed study is 10 times greater than that of the commercial diagnostic kits.

CONCLUSIONS

The proposed exciton-plasmon interaction-based NLPs-sensing strategy was highly sensitive, specific, and suitable for controlling upcoming outbreaks. Most importantly, the overall finding in the article will take the technology a step further to applicable point-of-care (POC) devices.

Recent advancements of nanomodified electrodes - Towards point-of-care detection of cardiac biomarkers

The increasing number of deaths from cardiovascular diseases has become a substantial concern in both developed and underdeveloped countries. Rapid and on-site monitoring of this disease is urgently important to control, prevent and make awareness of public health. Recently, a lot of focus has been placed on nanomaterials and modify these nanomaterials have been explored to detect cardiac biomarkers. By implementing biosensors that are modified with novel recognition elements and more stable nanomaterials, the use of electrochemistry for point-of-care devices is more realistic every day. This review focuses on the current state of nanomaterials conjugated biorecognition elements (enzyme integrated with nanomaterials, antibody conjugated nanomaterials and aptamer conjugated nanomaterials) for electrochemical cardiovascular disease detection. Specifically, a lot of attention has been given to the trends toward more stable biosensors that have increased the potential to be used as point-of-care devices for the detection of cardiac biomarkers due to their high stability and specificity. Moreover, the recent progress on biomolecule-free electrochemical nanosensors for cardiovascular disease detection has been considered. At last, the possibility and drawbacks of some of these techniques for point-of-care cardiac device development in the future have been discussed.

Peroxidase-Mimicking Hierarchically Organized Gold Particles for Glucose Detection

In this work, we synthesize a series of hierarchically organized gold nanoparticles (Au HOPs-X) with peroxidase (POD)-like catalytic activity by the in situ reduction of Au-thiolate hierarchically organized particles (Au HOPs). The initial Au HOPs show little POD-like catalytic activity. However, after the reduction of the particles, the Au HOPs-X showed enhanced POD-like catalytic activity, where X represents the reduction degree of Au HOPs. The reasons are as follows: (1) the Au-thiolate complexes on the surface of the Au HOPs-X were reduced into Au nanoparticles, and the active Au⁰ content increases with the increase of the reduction degree; (2) the specific surface area of Au HOPs-X becomes larger. Based on this, the Au HOPs-10 with the highest catalytic activity were combined with glucose oxidase to obtain a standard curve as a function of glucose concentrations. The color of the solutions was captured by mobile phone photos to determine their saturation, and the rapid detection of glucose was achieved through the standard curve of glucose concentration and saturation determined in this study.

SERS-based error calibration of a TMB-H2O2 colorimetric system

3,3',5,5'-tetramethylbenzidine (TMB)-H₂O₂ is widely used as an effective colorimetric system, in which the color reaction is implemented with peroxidase-catalyzed TMB oxidation by H₂O₂ that usually measured UV-vis absorption spectra or Raman spectra. However, its low accuracy significantly limits its application. Blue charge transfer complex (CTC), which is the product of TMB and H₂O₂ reaction and is used as the basis for partial colorimetric methods, usually causes colorimetric error owing to changes in the UV-vis absorption and Raman spectra during TMB oxidation under various environmental conditions (catalyst type, temperature, H₂O₂ concentration). Herein, we propose a surface-enhanced Raman spectrum (SERS)-based error calibration method to improve the accuracy of the TMB-H₂O₂ colorimetric system. It is found that under 633 nm laser excitation, TMB has three Raman peaks at 1189, 1335 and 1609 cm^-1 in the single-electron oxidation phase, and these peaks disappear completely in the two-electron oxidation phase. By comparing these Raman peaks, we can conveniently obtain the actual process information during TMB oxidation. Using the proposed method, the accuracy of the TMB-H₂O₂ colorimetric system improved by more than 15%. Importantly, this SERS-based TMB-H₂O₂ error calibration method will open a new horizon for enzyme-linked immunosorbent assay (ELISA) and other biomedical applications.

Recent advances in airborne pathogen detection using optical and electrochemical biosensors

The world is currently facing an adverse condition due to the pandemic of airborne pathogen SARS-CoV-2. Prevention is better than cure; thus, the rapid detection of airborne pathogens is necessary because it can reduce outbreaks and save many lives. Considering the immense role of diverse detection techniques for airborne pathogens, proper summarization of these techniques would be beneficial for humans. Hence, this review explores and summarizes emerging techniques, such as optical and electrochemical biosensors used for detecting airborne bacteria (Bacillus anthracis, Mycobacterium tuberculosis, Staphylococcus aureus, and Streptococcus pneumoniae) and viruses (Influenza A, Avian influenza, Norovirus, and SARS-CoV-2). Significantly, the first section briefly focuses on various diagnostic modalities applied toward airborne pathogen detection. Next, the fabricated optical biosensors using various transducer materials involved in colorimetric and fluorescence strategies for infectious pathogen detection are extensively discussed. The third section is well documented based on electrochemical biosensors for airborne pathogen detection by differential pulse voltammetry, cyclic voltammetry, square-wave voltammetry, amperometry, and impedance spectroscopy. The unique pros and cons of these modalities and their future perspectives are addressed in the fourth and fifth sections. Overall, this review inspected 171 research articles published in the last decade and persuaded the importance of optical and electrochemical biosensors for airborne pathogen detection.

Nanomaterials for virus sensing and tracking

The effect of the on-going COVID-19 pandemic on global healthcare systems has underlined the importance of timely and cost-effective point-of-care diagnosis of viruses. The need for ultrasensitive easy-to-use platforms has culminated in an increased interest for rapid response equipment-free alternatives to conventional diagnostic methods such as polymerase chain reaction, western-blot assay, etc. Furthermore, the poor stability and the bleaching behavior of several contemporary fluorescent reporters is a major obstacle in understanding the mechanism of viral infection thus retarding drug screening and development. Owing to their extraordinary surface-to-volume ratio as well as their quantum confinement and charge transfer properties, nanomaterials are desirable additives to sensing and imaging systems to amplify their signal response as well as temporal resolution. Their large surface area promotes biomolecular integration as well as efficacious signal transduction. Due to their hole mobility, photostability, resistance to photobleaching, and intense brightness, nanomaterials have a considerable edge over organic dyes for single virus tracking. This paper reviews the state-of-the-art of combining carbon-allotrope, inorganic and organic-based nanomaterials with virus sensing and tracking methods, starting with the impact of human pathogenic viruses on the society. We address how different nanomaterials can be used in various virus sensing platforms (e.g. lab-on-a-chip, paper, and smartphone-based point-of-care systems) as well as in virus tracking applications. We discuss the enormous potential for the use of nanomaterials as simple, versatile, and affordable tools for detecting and tracing viruses infectious to humans, animals, plants as well as bacteria. We present latest examples in this direction by emphasizing major advantages and limitations.

Nanozymatic detection of thiocyanate through accelerating the growth of ultra-small gold nanoparticles/graphene quantum dots hybrids

Thiocyanate (SCN^-) concentration monitoring in food is important to ensure the health and safety of the consumers.A colorimetric detection of thiocyanate (SCN^-) based on the nanozymatic activity of gold nanoparticle-graphene quantum dots (GQDs-Au NPs) hybrids in the presence of 3,3',5,5'-tetramethylbenzidine (TMB) and H₂O₂ has been proposed. Here, a new synthesis method of GQDs directly from graphite was introduced. Transmission electron microscopy (TEM) images revealed that the size of the GQDs was 3-5 nm, and the emission peak appeared at 450 nm. As-synthesized GQDs was utilized to produce GQDs-Au NPs hybrids without additional chemicals. However, the presence of SCN^- inhibits the growth of Au NPs, the resulting Au NPs are smaller in size. Moreover, SCN^- group is well-known for hydroxyl radical (OH) scavenging activity that could oxidize TMB. Both effects boosted the nanozymatic activity of GQDs-Au NPs to detect SCN^- under optimized conditions with a limit of detection (LOD) of 3 nM. Present study also validates the methodology to detect SCN^- in raw milk.

Positively Charged Gold Quantum Dots: An Nanozymatic "Off-On" Sensor for Thiocyanate Detection

The concentration of thiocyanate (SCN⁻) in bodily fluids is a good indicator of potential and severe health issues such as nasal bleeding, goiters, vertigo, unconsciousness, several inflammatory diseases, and cystic fibrosis. Herein, a visual SCN⁻ sensing method has been developed using the enzyme-like nature of positively charged gold quantum dots (Au QDs) mixed with 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide (H₂O₂₎. This research also reports a new method of synthesizing positively charged Au QDs directly from gold nanoparticles through a hydrothermal process. Microscopic imaging has showed that the Au QDs were 3–5 nm in size, and the emission wavelength was at 438 nm. Au QDs did not display any enzyme-like nature while mixed up with TMB and H₂O₂. However, the nanozymatic activity of Au QDs appeared when SCN⁻ was included, leading to a very low detection limit (LOD) of 8 nM and 99–105% recovery in complex media. The steady-state kinetic reaction of Au QDs showed that Au QDs had a lower Michaelis–Menten constant (Km) toward H₂O₂ and TMB, which indicates that the Au QDs had a higher affinity for H₂O₂ and TMB than horseradish peroxidase (HRP). A mechanism study has revealed that the scavenging ability of hydroxyl (•OH) radicals by the SCN⁻ group plays an important role in enhancing the sensitivity in this study. The proposed nanozymatic “Off–On” SCN⁻ sensor was also successfully validated in commercial milk samples.

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.

PdIr Aerogels with Boosted Peroxidase-like Activity for a Sensitive Total Antioxidant Capacity Colorimetric Bioassay

Metallic aerogels (MAs), imparting the active catalytic properties of nanostructured noble metals to macroscopic aerogels, draw tremendous interest in diverse fields owing to the unique features of three-dimensional interconnected channels, self-supported architectures, and pure metallic backbones. Moreover, flexible manipulation of compositions, high electrical conductivity, and abundant active sites of MAs contribute to the great potential to mimic natural enzymes. However, the cumbersome synthetic process takes a couple of hours to days, and unavoidable impurities usually impede surface electrons/mass transfer, posing the decrease of stability and enzyme-like activity of MAs. Here, a PdIr bimetallic aerogel prepared in the ethanol phase via spontaneous assembly and a surfactant-free strategy is reported. Gelation kinetics of PdIr aerogels in ethanol is increased with 2-4 orders of magnitude compared to the traditional preparation method in water. Owing to the intrinsic physicochemical properties, PdIr aerogels exhibit the high activity of peroxidase mimics using 3,3',5,5'-tetramethylbenzidine as a chromogenic probe. In addition, the PdIr aerogels maintain relatively high activity at an elevated temperature and pH of 3-7, demonstrating their good stability and survivability. Utilizing the exceptional peroxidase-like activity of PdIr aerogels, we realized the quantitative bioassay for H₂O₂ and total antioxidant capacity, indicating enormous potential in the quality evaluation of real samples.

Innovative and versatile nanoplasmonic approach for the full sensing of proteinogenic aminoacids in nutritional supplements

A current nourishment issue is the development of smart and reliable analytical strategies to control in a simple way main bioactive compounds of nutritional supplements whose increasing use is deemed a trend nowadays. With this aim a quick and highly sensitive plasmonic sensor using simple citrate coated gold nanoparticles (AuNPs) as optical probe, was developed for both qualitative and quantitative global assessment of all the proteinogenic amino acids in nutritional supplements. AuNPs of five different sizes (from 19 to 74 nm) were synthesized, characterized and evaluated as optimal transductor element for the sensing approach. Critical physic-chemical conditions controlling aggregation (pH, incubation time, AuNPs amount and ionic strength) were investigated on the main five types of aas, structurally different attending to their R-side chain and with expected distinctive behaviour on aggregation mechanisms, which are also discussed. All proteinogenic amino acids induced AuNPs aggregation at low pH (2.5) causing a change in the colour solution from red to blue, as well as a redshift in the plasmon band from 518 nm (disperse NPs) to 650 nm (aggregated NPs). Based on this sensing approach two different strategies are allowed, a preliminary qualitative/semi-quantitative screening just by the naked eye (simple spot test) and a second quantitative confirmation procedure using the analytical signal (A₆₅₀/A₅₁₈). Reliability of quantitative approach was assessed by an exhaustive validation procedure, where matrix effects and potential interferences usually present in commercial samples and affecting the analytical signal were mainly focussed. The results for the analysis of complex nutritional samples were validated by means of a statistical comparison with those ones of the official reference Kjeldahl method (paired Student test-t) at a 95% confidence level. This is the first sensing approach able to provide the global estimation of proteinogenic aas amount based on their simply AuNPs aggregation induction, irrespectively of their R-side chain structure.

Gold nanoparticles in virus detection: Recent advances and potential considerations for SARS-CoV-2 testing development

Viruses are infectious agents that pose significant threats to plants, animals, and humans. The current coronavirus disease 2019 pandemic, which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread globally and resulted in over 2 million deaths and immeasurable financial losses. Rapid and sensitive virus diagnostics become crucially important in controlling the spread of a pandemic before effective treatment and vaccines are available. Gold nanoparticle (AuNP)-based testing holds great potential for this urgent unmet biomedical need. In this review, we describe the most recent advances in AuNP-based viral detection applications. In addition, we discuss considerations for the design of AuNP-based SARS-CoV-2 testings. Finally, we highlight and propose important parameters to consider for the future development of effective AuNP-based testings that would be critical for not only this COVID-19 pandemic, but also potential future outbreaks. This article is categorized under: Diagnostic Tools > Biosensing Diagnostic Tools > In Vitro Nanoparticle-Based Sensing.

Strong nanozymatic activity of thiocyanate capped gold nanoparticles: an enzyme–nanozyme cascade reaction based dual mode ethanol detection in saliva

This article reports on the strong nanozymatic activity of thiocyanide capped gold nanoparticles (TC-AuNPs) in the presence of 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2.

Graphene-based Nanomaterials in Fighting the Most Challenging Viruses and Immunogenic Disorders

Viral diseases have long been among the biggest challenges for healthcare systems around the world. The recent Coronavirus Disease 2019 (COVID-19) pandemic is an example of how complicated the situation can get if we are not prepared to combat a viral outbreak in time, which brings up the need for quick and affordable biosensing platforms and vast knowledge of potential antiviral effects and drug/gene delivery opportunities. The same challenges have also existed for nonviral immunogenic disorders. Nanomedicine is considered a novel candidate for effectively overcoming these worldwide challenges. Among the versatile nanomaterials commonly used in biomedical applications, graphene has recently earned much attention thanks to its special and inspiring physicochemical properties, such as its large surface area, efficient thermal/electrical properties, carbon-based chemical purity with controllable biocompatibility, easy functionalization, capability of single-molecule detection, anticancer characteristics, 3D template feature in tissue engineering, and, in particular, antibacterial/antiviral activities. In this Review, the most important and challenging viruses of our era, such as human immunodeficiency virus, Ebola, SARS-CoV-2, norovirus, and hepatitis virus, and immunogenic disorders, such as asthma, Alzheimer's disease, and Parkinson's disease, in which graphene-based nanomaterials can effectively take part in the prevention, detection, treatment, medication, and health effect issues, have been covered and discussed.

Ultrasmall Au nanoparticles modified 2D metalloporphyrinic metal-organic framework nanosheets with high peroxidase-like activity for colorimetric detection of organophosphorus pesticides

Ultrasmall Au nanoparticles (UsAuNPs) in the size range of 4.0-7.0 nm was successfully immobilized on the surface of 2D metalloporphyrinic metal-organic framework nanosheets (2D MOF). Firstly, The obtained hybrid nanomaterial, UsAuNPs/2D MOF, was fully characterized by TEM, HRTEM, element mapping images and XPS. Then, the peroxidase-like activity of UsAuNPs/2D MOF was comparatively studied with other hybrid nanozyme to explore the influence of AuNPs size on peroxidase-like activity. Further, UsAuNPs/2D MOF with outstanding peroxidase-like activity was selected to form ternary cascade enzyme reaction with acetylcholinesterase (AChE) and choline oxidase (ChOx). Based on the inhibitory effect of organophosphorus pesticides on AChE, a fast and sensitive colorimetric method was established for trichlorfon detection with the advantages of simple operation, low detection limit (1.7 μM), good linear range (1.7-42.4 μM) and high accuracy (recovery rate of 96.6-105.3%). Finally, this method was applied to visual analysis of trichlorfon concentration in tomatoes, cucumbers and eggplants.

Advances and Future Perspective on Detection Technology of Human Norovirus

Human norovirus (HuNoV) is a food-borne pathogen that causes acute gastroenteritis in people of all ages worldwide. However, no approved vaccines and antiviral drugs are available at present. Therefore, the development of accurate and rapid detection technologies is important in controlling the outbreak of HuNoVs. This paper reviewed the research progress on HuNoV detection, including immunological methods, molecular detection and biosensor technology. Immunological methods and molecular detection technologies are still widely used for HuNoV detection. Furthermore, biosensors will become an emerging developmental direction for the rapid detection of HuNoVs because of their high sensitivity, low cost, easy operation and suitability for onsite detection.

Axial Ligand-Engineered Single-Atom Catalysts with Boosted Enzyme-Like Activity for Sensitive Immunoassay

Inspired by the key role of the coordination environment in the catalytic activity of enzymes, a rational design of the coordination structure of active sites at the atom scale is expected to develop high-performance enzyme-like catalysts. Here, we design a simple model system involving pentacoordinated and tetracoordinated Fe-N-C single-atom catalysts (named NG-Heme and G-Heme, respectively) to investigate structure-activity relationships. NG-Heme with axial ligand-engineered Fe sites exhibits superior enzyme-like activity to G-Heme, achieving the goal of vivid mimicking of the active sites of peroxidase. Experiments and theoretical studies reveal that the enhanced intrinsic catalytic activity originates from the "push effect" of the additional axial ligand, which can strengthen the interaction between the active site and the intermediate. Based on the outstanding catalytic activity, an NG-Heme-linked immunosorbent assay was constructed for colorimetric detection of carcinoembryonic antigen, exhibiting satisfactory sensitivity and feasibility in the analysis of clinical samples.

Self-Assembled Chromogenic Polymeric Nanoparticle-Laden Nanocarrier as a Signal Carrier for Derivative Binary Responsive Virus Detection

In the current biosensor, the signal generation is limited to single virus detection in the reaction chamber. An adaptive strategy is required to enable the recognition of multiple viruses for diagnostics and surveillance. In this work, a nanocarrier is deployed to bring specific signal amplification into the biosensor, depending on the target viruses. The nanocarrier is designed using pH-sensitive polymeric nanoparticle-laden nanocarriers (PNLNs) prepared by sequential nanoprecipitation. The nanoprecipitation of two chromogens, phenolphthalein (PP) and thymolphthalein (TP), is investigated in three different solvent systems in which PNLNs demonstrate a high loading of the chromogen up to 59.75% in dimethylformamide (DMF)/dimethyl sulfoxide (DMSO)/ethanol attributing to the coprecipitation degree of the chromogens and the polymer. The PP-encapsulated PNLNs (PP@PNLNs) and TP-encapsulated PNLNs (TP@PNLNs) are conjugated to antibodies specific to target viruses, influenza virus A subtype H1N1 (IV/A/H1N1) and H3N2 (IV/A/H3N2), respectively. After the addition of anti-IV/A antibody-conjugated magnetic nanoparticles (MNPs) and magnetic separation, the enriched PNLNs/virus/MNPs sandwich structure is treated in an alkaline solution. It demonstrates a synergy reaction in which the degradation of the polymeric boundary and the pH-induced colorimetric development of the chromogen occurred. The derivative binary biosensor shows feasible detection on IV/A with excellent specificities of PP@PNLNs on IV/A/H1N1 and TP@PNLNs on IV/A/H3N2 with LODs of 27.56 and 28.38 fg mL^-1, respectively. It intrigues the distinguished analytical signal in human serum with a variance coefficient of 25.8% and a recovery of 93.6-110.6% for one-step subtype influenza virus detection.

Nanoscience and quantum science-led biocidal and antiviral strategies

The severe acute respiratory syndrome coronavirus (SARS-CoV-2) caused the COVID-19 pandemic. According to the World Health Organization, this pandemic continues to be a serious threat to public health due to the worldwide spread of variants and their higher rate of transmissibility. A range of measures are necessary to slow the pandemic and save lives, which include constant evaluation and the careful adjustment of public-health responses augmented by medical treatments, vaccines and protective gear. It is hypothesized that nanostructured particulates underpinned by nanoscience and quantum science yield high-performing antiviral strategies, which can be applied in preventive, diagnostic, and therapeutic applications such as face masks, respirators, COVID test kits, vaccines, and drugs. This review is aimed at providing comprehensive and cohesive perspectives on various nanostructures that are suited to intensifying and amplifying the effectiveness of antiviral strategies. Growing scientific literature over the past eighteen months indicates that quantum dots, iron oxide, silicon oxide, polymeric and metallic nanoparticles have been employed in COVID-19 diagnostic assays, vaccines, and personal protective equipment (PPE). Quantum dots have displayed their suitability as more sensitive imaging probes in diagnostics and prognostics, and as controlled drug-release carriers that target the virus. Nanoscience and quantum science have assisted the design of advanced vaccine delivery since nanostructured materials are suited for antigen delivery, as mimics of viral structures and as adjuvants. Furthermore, the quantum science- and nanoscience-supported tailored functionalization of nanostructured materials offers insight and pathways to deal with future pandemics. This review seeks to illustrate several examples, and to explain the underpinning quantum science and nanoscience phenomena, which include wave functions, electrostatic interactions, van der Waals forces, thermal and electrodynamic fluctuations, dispersion forces, local field-enhancement effects, and the generation of reactive oxygen species (ROS). This review discusses how nanostructured materials are helpful in the detection, prevention, and treatment of the SARS-CoV-2 infection, other known viral infection diseases, and future pandemics.

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.

Nanotechnology-based Colorimetric Approaches for Pathogenic Virus Sensing: A review

Fast and inexpensive virus identification protocols are paramount to hinder the further extent of pandemic diseases, minimize economic and social damages, and expedite proper clinical rehabilitation. Until now, various biosensors have been fabricated for the identification of pathogenic particles. But, they offer many difficulties. Nanotechnology resolves these difficulties and offers direct identification of pathogenic species in real-time. Among them, nanomaterial based-colorimetric sensing approach of pathogenic viruses by the naked eye has attracted much awareness because of their simplicity, speed, and low cost. In this review, the latest tendencies and advancements are overviewed in detecting pathogenic viruses using colorimetric concepts. We focus on and reconsider the use of distinctive nanomaterials such as metal nanoparticles, carbon nanotubes, graphene oxide, and conducting polymer to form colorimetric pathogenic virus sensors.