Engineering DNA–Nanozyme Interfaces for Rapid Detection of Dental Bacteria

Convenient Biochemical Testing Technologies for Oral Disease Risk Warning: Opportunities and Challenges

In recent years, attention toward oral health issues has increased with economic development and improvements in quality of life. Biochemical testing technologies offer an efficient method for identifying insidious pathological changes in the oral cavity. Frequent home-based self-screening can enable early identification of dental disease risks, thus facilitating timely interventions. Convenient home-based biochemical testing methods must be user-friendly, cost-effective, and operable without specialized equipment or extensive training. This review summarizes recent advances in convenient biochemical testing methods for the detection and diagnosis of oral diseases, focusing on their reliability, user compliance, and practicality for home-based applications. This review highlights the significance of biomarker distribution imaging for simultaneously identifying multiple lesions and provides perspectives on future research directions. By promoting interdisciplinary collaboration in biochemical diagnostics, this review outlines pathways toward personalized oral healthcare, precision dentistry, and enhanced overall health outcomes.

Aptamers in dentistry: diagnosis, therapeutics, and future perspectives

Oral health is essential to general health. The diagnosis of dental diseases and treatment planning of dental care need to be straightforward and accurate. Recent studies have reported the use of aptamers in dentistry to achieve a simple diagnosis and facilitate therapy. Aptamers comprise nucleic acid sequences that possess a strong affinity for their target. Synthesized chemically, aptamers have several advantages, including smaller size, higher stability, and lower immunogenicity compared with monoclonal antibodies. They can be used to detect biomarkers in saliva and the presence of various pathogens, or can be used as a targeted drug delivery system for disease treatment. This review highlights current research on aptamers for dental care, especially the recent progress in oral disease diagnosis and therapeutics. The challenges and unresolved problems faced by the clinical use of aptamers are also discussed. In the future, the clinical applications of aptamers will be further extended to include, for example, dental indications and regenerative dentistry.

Exploring Nucleic Acid Nanozymes: A New Frontier in Biosensor Development

With the growing interest in nucleic acids and nanozymes, nucleic acid nanozymes (NANs) have emerged as a promising alternative to traditional enzyme catalysts, combining the advantages of nucleic acids and nanomaterials, and are widely applied in the field of biosensing. This review provides a comprehensive overview of recent studies on NAN-based biosensors. It classifies NANs based on six distinct enzymatic activities: peroxidase-like, oxidase-like, catalase-like, superoxide dismutase-like, laccase-like, and glucose oxidase-like. This review emphasizes how the catalytic activity of nanozymes is significantly influenced by the properties of nucleic acids and explores the regulatory mechanisms governing the catalytic activity of NANs. Additionally, it systematically reviews important research progress on NANs in colorimetric, fluorescent, electrochemical, SERS, and chemiluminescent sensors, offering insights into the development of the NAN field and biosensor applications.

Emerging Combination of Hydrogel and Electrochemical Biosensors

Electrochemical sensors are among the most promising technologies for biomarker research, with outstanding sensitivity, selectivity, and rapid response capabilities that make them important in medical diagnostics and prognosis. Recently, hydrogels have gained attention in the domain of electrochemical biosensors because of their superior biocompatibility, excellent adhesion, and ability to form conformal contact with diverse surfaces. These features provide distinct advantages, particularly in the advancement of wearable biosensors. This review examines the contemporary utilization of hydrogels in electrochemical sensing, explores strategies for optimization and prospective development trajectories, and highlights their distinctive advantages. The objective is to provide an exhaustive overview of the foundational principles of electrochemical sensing systems, analyze the compatibility of hydrogel properties with electrochemical methodologies, and propose potential healthcare applications to further illustrate their applicability. Despite significant advances in the development of hydrogel-based electrochemical biosensors, challenges persist, such as improving material fatigue resistance, interfacial adhesion, and maintaining balanced water content across various environments. Overall, hydrogels have immense potential in flexible biosensors and provide exciting opportunities. However, resolving the current obstacles will necessitate additional research and development efforts.

How Will Nanomedicine Revolutionize Future Dentistry and Periodontal Therapy?

Periodontitis is a prevalent inflammatory disease affecting the supporting structures of the teeth, leading to gum recession, tooth loss, and systemic health complications. Traditional diagnostic methods and treatments, such as clinical evaluation and scaling, often fall short in early detection and targeted therapy, particularly in complex or advanced cases. Recent advancements in nanomedicine offer promising solutions for improving both the diagnosis and treatment of periodontitis. Nanoparticles, such as liposomes, quantum dots, and nanorods, have demonstrated potential in enhancing diagnostic accuracy by enabling more precise detection of periodontal pathogens and biomarkers at the molecular level. Furthermore, nanotechnology-based therapies, including drug delivery systems and antimicrobial agents, offer localized and controlled release of therapeutic agents, enhancing efficacy and reducing side effects compared to conventional treatments. This study reviews the current applications of nanomedicine in the diagnosis and treatment of periodontitis, highlighting its potential to revolutionize periodontal care by improving early detection, reducing treatment times, and enhancing therapeutic outcomes.

Nanozymes and their biomolecular conjugates as next-generation antibacterial agents: A comprehensive review

Antimicrobial resistance (AMR), the ability of bacterial species to develop resistance against exposed antibiotics, has gained immense global attention in the past few years. Bacterial infections are serious health concerns affecting millions of people annually worldwide. Therefore, developing novel antibacterial agents that are highly effective and avoid resistance development is imperative. Among various strategies, recent developments in nanozyme technology have shown promising results as antibacterials in several antibiotic-sensitive and resistant bacterial species. Nanozymes offer several advantages over corresponding natural enzymes, such as inexpensive, stable, multifunctional, tunable catalytic properties, etc. Although the use of nanozymes as antibacterial agents has provided promising results, the specific biomolecule-conjugated nanozymes have shown further improvement in catalytic performance and associated antibacterial efficacy. The exclusive design of functional nanozymes with theranostic potential is found to simultaneously inhibit the growth and image of AMR bacterial species. This review comprehensively summarizes the history of nanozymes, their classification, biomolecules conjugated nanozyme, and their mechanism of enzyme-mimetic activity and associated antibacterial activity in antibiotic-sensitive and resistant species. The futureneeds to effectively engineer the existing or new nanozymes to curb AMR have also been discussed.

Smart Nanozymes for Diagnosis of Bacterial Infection: The Next Frontier from Laboratory to Bedside Testing

The global spread of infectious diseases caused by pathogenic bacteria significantly poses public health concerns, and methods for sensitive, selective, and facile diagnosis of bacteria can efficiently prevent deterioration and further spreading of the infections. The advent of nanozymes has broadened the spectrum of alternatives for diagnosing bacterial infections. Compared to natural enzymes, nanozymes exhibit the same enzymatic characteristics but offer greater economic efficiency, enhanced durability, and adjustable dimensions. The importance of early diagnosis of bacterial infection and conventional diagnostic approaches is introduced. Subsequently, the review elucidates the definition, properties, and catalytic mechanism of nanozymes. Eventually, the detailed application of nanozymes in detecting bacteria is explored, highlighting their utilization as biosensors that allow for accelerated and highly sensitive identification of bacterial infections and reflecting on the potential of nanozyme-based bacterial detection as a point-of-care testing (POCT) tool. A brief summary of obstacles and future perspectives in this field is presented at the conclusion of this review.

Emerging Nanomaterials as Versatile Nanozymes: A New Dimension in Biomedical Research

The enzyme-mimicking nature of versatile nanomaterials proposes a new class of materials categorized as nano-enzymes, ornanozymes. They are artificial enzymes fabricated by functionalizing nanomaterials to generate active sites that can mimic enzyme-like functions. Materials extend from metals and oxides to inorganic nanoparticles possessing intrinsic enzyme-like properties. High cost, low stability, difficulty in separation, reusability, and storage issues of natural enzymes can be well addressed by nanozymes. Since 2007, more than 100 nanozymes have been reported that mimic enzymes like peroxidase, oxidase, catalase, protease, nuclease, hydrolase, superoxide dismutase, etc. In addition, several nanozymes can also exhibit multi-enzyme properties. Vast applications have been reported by exploiting the chemical, optical, and physiochemical properties offered by nanozymes. This review focuses on the reported nanozymes fabricated from a variety of materials along with their enzyme-mimicking activity involving tuning of materials such as metal nanoparticles (NPs), metal-oxide NPs, metal-organic framework (MOF), covalent organic framework (COF), and carbon-based NPs. Furthermore, diverse applications of nanozymes in biomedical research are discussed in detail.

Portable Saliva Sensor Based on Dual Recognition Elements for Detection of Caries Pathogenic Bacteria

Dental caries is one of the most common diseases affecting more than 2 billion people's health worldwide. In a clinical setting, it is challenging to predict and proactively guard against dental cavities prior to receiving a confirmed diagnosis. Streptococcus mutans (S. mutans) in saliva has been recognized as the main causative bacterial agent that causes dental caries. High sensitivity, good selectivity, and a wide detection range are incredibly important factors to affect S. mutans detection in practical applications. In this study, we present a portable saliva biosensor designed for the early detection of S. mutans with the potential to predict the occurrence of dental cavities. The biosensor was fabricated using a S. mutans-specific DNA aptamer and S. mutans-imprinted polymers. Methylene blue was utilized as a redox probe in the sensor to generate current signals for analysis. When S. mutans enters complementarily S. mutans cavities, it blocks electron transfer between methylene blue and the electrode, resulting in decreases in the reduction current signal. The signal variations are associated with S. mutans concentrations that are useful for quantitative analysis. The linear detection range of S. mutans is 102-109 cfu mL-1, which covers the critical concentration of high caries risk. The biosensor exhibited excellent selectivity toward S. mutans in the presence of other common oral bacteria. The biosensor's wide detection range, excellent selectivity, and low limit of detection (2.6 cfu mL-1) are attributed to the synergistic effect of aptamer and S. mutans-imprinted polymers. The sensor demonstrates the potential to prevent dental caries.

The potential use of nanozymes as an antibacterial agents in oral infection, periodontitis, and peri-implantitis

Several studies suggest that oral pathogenic biofilms cause persistent oral infections. Among these is periodontitis, a prevalent condition brought on by plaque biofilm. It can even result in tooth loss. Furthermore, the accumulation of germs around a dental implant may lead to peri-implantitis, which damages the surrounding bone and gum tissue. Furthermore, bacterial biofilm contamination on the implant causes soft tissue irritation and adjacent bone resorption, severely compromising dental health. On decontaminated implant surfaces, however, re-osseointegration cannot be induced by standard biofilm removal techniques such as mechanical cleaning and antiseptic treatment. A family of nanoparticles known as nanozymes (NZs) comprise highly catalytically active multivalent metal components. The most often employed NZs with antibacterial activity are those that have peroxidase (POD) activity, among other types of NZs. Since NZs are less expensive, more easily produced, and more stable than natural enzymes, they hold great promise for use in various applications, including treating microbial infections. NZs have significantly contributed to studying implant success rates and periodontal health maintenance in periodontics and implantology. An extensive analysis of the research on various NZs and their applications in managing oral health conditions, including dental caries, dental pulp disorders, oral ulcers, peri-implantitis, and bacterial infections of the mouth. To combat bacteria, this review concentrates on NZs that imitate the activity of enzymes in implantology and periodontology. With a view to the future, there are several ways that NZs might be used to treat dental disorders antibacterially.

Recent advances in nanomaterial-based biosensor for periodontitis detection

Periodontitis, a chronic inflammatory condition caused by bacteria, often causes gradual destruction of the components that support teeth, such as the alveolar bone, cementum, periodontal ligament, and gingiva. This ultimately results in teeth becoming loose and eventually falling out. Timely identification has a crucial role in preventing and controlling its progression. Clinical measures are used to diagnose periodontitis. However, now, there is a hunt for alternative diagnostic and monitoring methods due to the progress of technology. Various biomarkers have been assessed using multiple bodily fluids as sample sources. Furthermore, conventional periodontal categorization factors do not provide significant insights into the present disease activity, severity and amount of tissue damage, future development, and responsiveness to treatment. In recent times, there has been a growing utilization of nanoparticle (NP)-based detection strategies to create quick and efficient detection assays. Every single one of these platforms leverages the distinct characteristics of NPs to identify periodontitis. Plasmonic NPs include metal NPs, quantum dots (QDs), carbon base NPs, and nanozymes, exceptionally potent light absorbers and scatterers. These find application in labeling, surface-enhanced spectroscopy, and color-changing sensors. Fluorescent NPs function as photostable and sensitive instruments capable of labeling various biological targets. This article presents a comprehensive summary of the latest developments in the effective utilization of various NPs to detect periodontitis.

Enhanced "Electronic Tongue" for Dental Bacterial Discrimination and Elimination Based on a DNA-Encoded Nanozyme Sensor Array

Bacterial infections are the second leading cause of death around the world, especially those caused by delayed treatment and misdiagnosis. Therefore, rapid discrimination and effective elimination of multiple bacteria are of great importance for improving the survival rate in clinic. Herein, a novel colorimetric sensor array for bacterial discrimination and elimination is constructed using programmable DNA-encoded iron oxide nanoparticles (IONPs) as sensing elements. Utilizing differential interactions of bacteria on DNA-encoded IONPs, 11 kinds of dental bacteria and 6 kinds of proteins have been successfully identified by linear discriminant analysis (LDA). Moreover, the developed sensing system also performs well in the quantitative determination of individual bacteria and identification of bacterial mixtures. More importantly, the practicability of this sensing strategy is further verified by precise differentiation of blind and artificial saliva samples. Furthermore, the sensor array is used for efficiently killing multiple bacteria, demonstrating great potential in clinical prophylaxis and therapy.

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.

A pomegranate seed-structured nanozyme-based colorimetric immunoassay for highly sensitive and specific biosensing of Staphylococcus aureus

Staphylococcus aureus (S. aureus) infections are a serious threat to human health. The development of rapid and sensitive detection methods for pathogenic bacteria is crucial for accurate drug administration. In this research, by combining the advantages of enzyme-linked immunosorbent assay (ELISA), we synthesized nanozymes with high catalytic performance, namely pomegranate seed-structured bimetallic gold-platinum nanomaterials (Ps-PtAu NPs), which can catalyze a colorless TMB substrate into oxidized TMB (oxTMB) with blue color to achieve colorimetric analysis of S. aureus. Under the optimal conditions, the proposed biosensor could quantitatively detect S. aureus at levels ranging from 1.0 × 101 to 1.0 × 106 CFU mL-1 with a limit of detection (LOD) of 3.9 CFU mL-1. Then, an integrated color picker APP on a smartphone enables on-site point-of-care testing (POCT) of S. aureus with LOD as low as 1 CFU mL-1. Meanwhile, the proposed biosensor is successfully applied to the detection of S. aureus in clinical samples with high sensitivity and specificity.

A robust and facile label-free method for highly sensitive colorimetric detection of ascorbic acid in fresh fruits based on peroxidase-like activity of modified FeCo-LDH@WO3 nanocomposite

Many compounds such as amino acids and oligonucleotides have been shown to effectively change peroxidase-like activity of nanoparticles. While a few studies have focused on mimicking the active site of natural enzymes on nanozymes and thus increasing their substrate affinity. Therefore, in this work, the surface of FeCo@WO3 nanocomposite was modified using guanosine triphosphate (GTP) to mimic the histidine of peroxidase enzyme's active site and its modification was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). Then, the peroxidase-mimicking activity of the modified nanocomposite was tested using a colorimetric method, based on the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). It was found that GTP improves the activity of FeCo@WO3 as a natural peroxidase active site's distal histidine residue. Ascorbic acid (AA) is a powerful antioxidant that induces the reduction of blue color (oxidized TMB) ox-TMB to colorless TMB. The colorimetric method was applied for the sensitive detection of AA in common fruits. The linear range of AA was 10-100 μM with a limit of detection (LOD) of 0.27 μM, which provides a rapid and sensitive method for testing AA in the field of food analysis.

Recent Advances in Nanozyme-Mediated Strategies for Pathogen Detection and Control

Pathogen detection and control have long presented formidable challenges in the domains of medicine and public health. This review paper underscores the potential of nanozymes as emerging bio-mimetic enzymes that hold promise in effectively tackling these challenges. The key features and advantages of nanozymes are introduced, encompassing their comparable catalytic activity to natural enzymes, enhanced stability and reliability, cost effectiveness, and straightforward preparation methods. Subsequently, the paper delves into the detailed utilization of nanozymes for pathogen detection. This includes their application as biosensors, facilitating rapid and sensitive identification of diverse pathogens, including bacteria, viruses, and plasmodium. Furthermore, the paper explores strategies employing nanozymes for pathogen control, such as the regulation of reactive oxygen species (ROS), HOBr/Cl regulation, and clearance of extracellular DNA to impede pathogen growth and transmission. The review underscores the vast potential of nanozymes in pathogen detection and control through numerous specific examples and case studies. The authors highlight the efficiency, rapidity, and specificity of pathogen detection achieved with nanozymes, employing various strategies. They also demonstrate the feasibility of nanozymes in hindering pathogen growth and transmission. These innovative approaches employing nanozymes are projected to provide novel options for early disease diagnoses, treatment, and prevention. Through a comprehensive discourse on the characteristics and advantages of nanozymes, as well as diverse application approaches, this paper serves as a crucial reference and guide for further research and development in nanozyme technology. The expectation is that such advancements will significantly contribute to enhancing disease control measures and improving public health outcomes.

Detection and discrimination of pathogenic bacteria with nanomaterials-based optical biosensors: A review

Pathogenic bacteria can pose a great threat to food safety and human health. It is therefore imperative to develop a rapid, portable, and sensitive determination and discrimination method for pathogenic bacteria. Over the past few years, various nanomaterials (NMs) have been employed as desirable nanoprobes because they possess extraordinary properties that can be used for optical signal enabled detection and identification of bacteria. By means of modification, NMs can, depending on different mechanisms, sense targets directly or indirectly, which then provides an essential support for the detection and differentiation of pathogenic bacteria. In this review, recent application of NMs-based optical biosensors for food safety bacterial detection and discrimination is performed, mainly in but not limited to noble metal NMs, fluorescent NMs, and point-of-care testing (POCT). This review also focuses on future trends in bacterial detection and discrimination, and machine learning in performing intelligent rapid detection and multiple accurate identification of bacteria.

Magnetite-Based Biosensors and Molecular Logic Gates: From Magnetite Synthesis to Application

In the last few decades, point-of-care (POC) sensors have become increasingly important in the detection of various targets for the early diagnostics and treatment of diseases. Diverse nanomaterials are used as building blocks for the development of smart biosensors and magnetite nanoparticles (MNPs) are among them. The intrinsic properties of MNPs, such as their large surface area, chemical stability, ease of functionalization, high saturation magnetization, and more, mean they have great potential for use in biosensors. Moreover, the unique characteristics of MNPs, such as their response to external magnetic fields, allow them to be easily manipulated (concentrated and redispersed) in fluidic media. As they are functionalized with biomolecules, MNPs bear high sensitivity and selectivity towards the detection of target biomolecules, which means they are advantageous in biosensor development and lead to a more sensitive, rapid, and accurate identification and quantification of target analytes. Due to the abovementioned properties of functionalized MNPs and their unique magnetic characteristics, they could be employed in the creation of new POC devices, molecular logic gates, and new biomolecular-based biocomputing interfaces, which would build on new ideas and principles. The current review outlines the synthesis, surface coverage, and functionalization of MNPs, as well as recent advancements in magnetite-based biosensors for POC diagnostics and some perspectives in molecular logic, and it also contains some of our own results regarding the topic, which include synthetic MNPs, their application for sample preparation, and the design of fluorescent-based molecular logic gates.

Colorimetric aptasensor for fumonisin B1 detection based on the DNA tetrahedra-functionalized magnetic beads and DNA hydrogel-coated bimetallic MOFzyme

The toxicity and incidence of fumonisin B₁ (FB₁) pose a major challenge to public health and the environment, prompting the development of alternative quantitative strategies for FB₁. Herein, a colorimetric aptasensor was constructed based on DNA tetrahedra-functionalized magnetic beads (MBs) and DNA hydrogel-coated Mn-Zr bimetallic metal-organic frameworks-based nanozyme (MOFzyme). Initially, MBs functionalized by DNA tetrahedra demonstrated excellent capturing capability for FB₁. Along with the capture of FB₁, catalyst DNA (C) was released into the supernatant. Aided by fuel DNA (F), C can trigger continuous cleavage of the main chains and cross-linking points of the DNA hydrogel through an entropy-driven DNA circuit integrated into the hydrogel coating. Subsequently, the bimetallic MOFzyme encapsulated inside the DNA hydrogel was exposed and exerted its superb peroxidase-like activity, producing a colorimetric signal whose intensity was positively dependent on the amount of FB₁. The developed aptasensor exhibited good linearity in the range of 5 × 10^-4 to 50 ng mL^-1 with a limit of detection (LOD) of 0.38 pg mL^-1, and reasonable specificity in different matrices. Furthermore, the aptasensor was successfully applied to quantify FB₁ in actual samples with recoveries fell within 92.25 %- 108.00 %, showing its great potential in environmental monitoring and food safety.

Nanomaterials in Dentistry: Current Applications and Future Scope

Nanotechnology utilizes the mechanics to control the size and morphology of the particles in the required nano range for accomplishing the intended purposes. There was a time when it was predominantly applied only to the fields of matter physics or chemical engineering, but with time, biological scientists recognized its vast benefits and explored the advantages in their respective fields. This extension of nanotechnology in the field of dentistry is termed ‘Nanodentistry.’ It is revolutionizing every aspect of dentistry. It consists of therapeutic and diagnostic tools and supportive aids to maintain oral hygiene with the help of nanomaterials. Research in nanodentistry is evolving holistically but slowly with the advanced finding of symbiotic use of novel polymers, natural polymers, metals, minerals, and drugs. These materials, in association with nanotechnology, further assist in exploring the usage of nano dental adducts in prosthodontic, regeneration, orthodontic, etc. Moreover, drug release cargo abilities of the nano dental adduct provide an extra edge to dentistry over their conventional counterparts. Nano dentistry has expanded to every single branch of dentistry. In the present review, we will present a holistic view of the recent advances in the field of nanodentistry. The later part of the review compiled the ethical and regulatory challenges in the commercialization of the nanodentistry. This review tracks the advancement in nano dentistry in different but important domains of dentistry.

DNA-Engineered iron-based metal-organic framework bio-interface for rapid visual determination of exosomes

In this study, a rapid, low-cost and facile method for detecting exosomes was developed by engineering DNA ligands on the surface of an iron-based metal-organic framework (Fe-MOF). Aptamers of exosomal transmembrane CD63 protein (CD63-aptamers) were utilized as both the optically active layer and the exosome-specific recognition element to engineer an Fe-MOF bio-interface for high-efficiency regulation of the catalytic behavior of Fe-MOF toward the chromogenic substrate. The effective enhancement of the intrinsic peroxidase-like catalytic activity was confirmed via the self-assembly of CD63-aptamers on the surface of Fe-MOF. The specific binding of exosomes with CD63-aptamers altered the conformation of DNA ligands on the surface of Fe-MOF, contributing to sensitive variation in Fe-MOF catalytic activity. This directly produced a distinct color change and enabled the visual detection of exosomes. Via one-step "mixing-and-detection", the Fe-MOF bio-interface exhibited excellent performance in quantitative analysis of exosomes derived from human breast cancer cell lines ranging from 1.1 × 10⁵ to 2.2 × 10⁷ particles/μL with a detection limit of 5.2 × 10⁴ particles/μL. The expression of exosomal CD63 proteins originated from three types of cancer cell lines, including breast cancer, gastric cancer and lung cancer cell lines, was differentiated within only 17 min. Furthermore, the method was successfully applied to the identification of exosomes in serum samples, suggesting its potential in clinical analysis as a valuable tool for the rapid, convenient and economical testing of exosomes.

Single Probe-Based Chemical-Tongue Sensor Array for Multiple Bacterial Identification and Photothermal Sterilization in Real Time

Simple and efficient identification of multiple bacteria and sterilization in real time is of considerable significance for clinical diagnostics and quality control in food. Herein, a novel chemical-tongue sensor array with 3,3',5,5'-tetramethylbenzidine (TMB) as a single probe was developed for bacterial identification and photothermal elimination. The synthesized bimetallic palladium/platinum nanoparticles (Pd/Pt_NPs) present excellent catalytic capability that can catalyze TMB into oxidized TMB (oxTMB) with four feature absorption peaks. Bacteria have different ability on inhibiting the reaction between TMB and Pd/Pt_NPs. With the absorbance intensity of oxTMB at the four feature peaks as readout, nine kinds of bacteria including two drug-resistant bacteria can be successfully distinguished via linear discriminant analysis. Remarkably, oxTMB exhibits excellent photothermal properties and can effectively kill bacteria in real time under near-infrared laser irradiation. The strategy of selecting TMB as a single probe simplifies the experimental operation and reduces the time cost. Furthermore, the developed sensing system was used to promote the wound healing process of MRSA-infected mice in vivo. The investigation provides a promising simple and efficient strategy for bacterial identification and sterilization with a universal platform, which has great potential application in clinical diagnosis and therapy.

Regulation Mechanism of ssDNA Aptamer in Nanozymes and Application of Nanozyme-Based Aptasensors in Food Safety

Food safety issues are a worldwide concern. Pathogens, toxins, pesticides, veterinary drugs, heavy metals, and illegal additives are frequently reported to contaminate food and pose a serious threat to human health. Conventional detection methods have difficulties fulfilling the requirements for food development in a modern society. Therefore, novel rapid detection methods are urgently needed for on-site and rapid screening of massive food samples. Due to the extraordinary properties of nanozymes and aptamers, biosensors composed of both of them provide considerable advantages in analytical performances, including sensitivity, specificity, repeatability, and accuracy. They are considered a promising complementary detection method on top of conventional ones for the rapid and accurate detection of food contaminants. In recent years, we have witnessed a flourishing of analytical strategies based on aptamers and nanozymes for the detection of food contaminants, especially novel detection models based on the regulation by single-stranded DNA (ssDNA) of nanozyme activity. However, the applications of nanozyme-based aptasensors in food safety are seldom reviewed. Thus, this paper aims to provide a comprehensive review on nanozyme-based aptasensors in food safety, which are arranged according to the different interaction modes of ssDNA and nanozymes: aptasensors based on nanozyme activity either inhibited or enhanced by ssDNA, nanozymes as signal tags, and other methods. Before introducing the nanozyme-based aptasensors, the regulation by ssDNA of nanozyme activity via diverse factors is discussed systematically for precisely tailoring nanozyme activity in biosensors. Furthermore, current challenges are emphasized, and future perspectives are discussed.

Biosensors and Point-of-Care Devices for Bacterial Detection: Rapid Diagnostics Informing Antibiotic Therapy

With an exponential rise in antimicrobial resistance and stagnant antibiotic development pipeline, there is, more than ever, a crucial need to optimize current infection therapy approaches. One of the most important stages in this process requires rapid and effective identification of pathogenic bacteria responsible for diseases. Current gold standard techniques of bacterial detection include culture methods, polymerase chain reactions, and immunoassays. However, their use is fraught with downsides with high turnaround time and low accuracy being the most prominent. This imposes great limitations on their eventual application as point-of-care devices. Over time, innovative detection techniques have been proposed and developed to curb these drawbacks. In this review, a systematic summary of a range of biosensing platforms is provided with a strong focus on technologies conferring high detection sensitivity and specificity. A thorough analysis is performed and the benefits and drawbacks of each type of biosensor are highlighted, the factors influencing their potential as point-of-care devices are discussed, and the authors' insights for their translation from proof-of-concept systems into commercial medical devices are provided.

The recent development of nanozymes for food quality and safety detection

As potential mimics of natural enzymes, nanozymes overcome many disadvantages of natural enzymes such as complex preparation and purification process, high price, poor stability and low recycling efficiency. Combined with...

A Review on Metal- and Metal Oxide-Based Nanozymes: Properties, Mechanisms, and Applications

Since the ferromagnetic (Fe3O4) nanoparticles were firstly reported to exert enzyme-like activity in 2007, extensive research progress in nanozymes has been made with deep investigation of diverse nanozymes and rapid development of related nanotechnologies. As promising alternatives for natural enzymes, nanozymes have broadened the way toward clinical medicine, food safety, environmental monitoring, and chemical production. The past decade has witnessed the rapid development of metal- and metal oxide-based nanozymes owing to their remarkable physicochemical properties in parallel with low cost, high stability, and easy storage. It is widely known that the deep study of catalytic activities and mechanism sheds significant influence on the applications of nanozymes. This review digs into the characteristics and intrinsic properties of metal- and metal oxide-based nanozymes, especially emphasizing their catalytic mechanism and recent applications in biological analysis, relieving inflammation, antibacterial, and cancer therapy. We also conclude the present challenges and provide insights into the future research of nanozymes constituted of metal and metal oxide nanomaterials.

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.

Construction of Bio-Nano Interfaces on Nanozymes for Bioanalysis

Nanomaterials with enzyme-like activity (nanozymes) have been of great interest in broad applications ranging from biosensing to biomedical applications. Despite that much effort has been devoted to the development of the synthesis and applications of nanozymes, it is essential to understand the interactions between nanozymes and most commonly used biomolecules, i.e., avidin, streptavidin (SA), bovine serum albumin (BSA), immunoglobulin G (IgG), and glutathione (GSH), yet they have been rarely explored. Here, a series of bio-nano interfaces were constructed through direct immobilization of proteins on a variety of iron oxide and carbon-based nanozymes with different dimensions, including Fe₃O₄ nanoparticles (NPs, 0D), Fe₃O₄@C NPs (0D), Fe₃O₄@C nanowires (NWs, 1D), and graphene oxide nanosheets (GO NSs, 2D). Such interfaces enabled the modulation of the catalytic activities of the nanozymes with varying degrees, which allowed a good identification of multiplex proteins with high accuracy. Given the maximum inhibition on Fe₃O₄@C NP by BSA, we established molecular switches based on aptamer and toehold DNA, as well as Boolean logic gates (AND and NOR) in response to both DNA and proteins. Also importantly, we developed an on-particle reaction strategy for colorimetric detection of GSH with ultrahigh sensitivity and good specificity. The proposed sensor achieved a broad dynamic range spanning 7 orders of magnitude with a detection limit down to 200 pg mL^-1, which was better than that of an in-solution reaction-based biosensor by 2 orders of magnitude. Furthermore, we explored the mechanisms of the interactions at bio-nano interfaces by studying the interfacial factors, including surface coverage, salt concentration, and the curvature of the nanozyme. This study offered new opportunities in the elaborate design and better utilization of nanozymes for bioanalysis in clinical diagnosis and in vivo detection.

Recent Innovations in Bacterial Infection Detection and Treatment

Bacterial infections are a major threat to human health, exacerbated by increasing antibiotic resistance. These infections can result in tremendous morbidity and mortality, emphasizing the need to identify and treat pathogenic bacteria quickly and effectively. Recent developments in detection methods have focused on electrochemical, optical, and mass-based biosensors. Advances in these systems include implementing multifunctional materials, microfluidic sampling, and portable data-processing to improve sensitivity, specificity, and ease of operation. Concurrently, advances in antibacterial treatment have largely focused on targeted and responsive delivery for both antibiotics and antibiotic alternatives. Antibiotic alternatives described here include repurposed drugs, antimicrobial peptides and polymers, nucleic acids, small molecules, living systems, and bacteriophages. Finally, closed-loop therapies are combining advances in the fields of both detection and treatment. This review provides a comprehensive summary of the current trends in detection and treatment systems for bacterial infections.

Fluorescent and Opt-Electric Recording Bacterial Identification Device for Ultrasensitive and Specific Detection of Microbials

Since microbial detection is an important aspect for the prevention and control of foodborne diseases, an ideal detection system with high sensitivity, strong specificity, and timeliness is needed. Here, we proposed a fluorescent and opt-electric recording bacterial identification device (FORBID) for fully automatic real-time photoelectric sensing analysis of microbials by integrating the metabolic characteristics of microbial and selective substrate catalysis. It simplifies the testing process (one-step) and decreases the need of professional technicians. Besides, the system exhibits ultrasensitive (1 CFU/mL) and specific detection (99%) in both microbials, Escherichia coli and Pseudomonas aeruginosa. More importantly, the timeliness of this system is even better than that of the traditional culture methods. It is believed that this system can be extended to the detection of other microorganisms and provide a potential alternative for the detection of pathogens.

Applications of DNA-nanozyme-based sensors

Since the discovery of the enzyme-like activities of nanomaterials, the study of nanozymes has become one of the most popular research frontiers of diverse areas including biosensors. DNA also plays a very important role in the construction of biosensors. Thus, the idea of combined applications of nanozymes with DNA (DNA-nanozyme) is very attractive for the development of nanozyme-based biosensors, which has attracted considerable interest of researchers. To date, many sensors based on DNA-functionalized or templated nanozymes have been reported for the detection of various targets and highly accelerated the development of nanozyme-based sensors. In this review, we summarize the main applications and advances of DNA-nanozyme-based sensors. Additionally, perspectives and challenges are also discussed at the end of the review.

Nanozymes go oral: nanocatalytic medicine facilitates dental health

Nanozymes are multi-functional nanomaterials with enzyme-like activity, which rapidly won a place in biomedicine due to their number of nanocatalytic materials types and applications. Yan and Gao first discovered horseradish peroxidase-like activity in ferromagnetic nanoparticles in 2007. With the joint efforts of many scientists, a new concept-nanocatalytic medicine-is emerging. Nanozymes overcome the inherent disadvantages of natural enzymes, such as poor environmental stability, high production costs, difficult storage and so on. Their progress in dentistry is following the advancement of materials science. The oral research and application of nanozymes is becoming a new branch of nanocatalytic medicine. In order to highlight the great contribution of nanozymes facilitating dental health, we first review the overall research progress of multi-functional nanozymes in oral related diseases, including treating dental caries, dental pulp diseases, oral ulcers and peri-implantitis; the monitoring of oral cancer, oral bacteria and ions; and the regeneration of soft and hard tissue. Additionally, we also propose the challenges remaining for nanozymes in terms of their research and application, and mention future concerns. We believe that the new catalytic nanomaterials will play important roles in dentistry in the future.

Conjugation of antibodies and aptamers on nanozymes for developing biosensors

Nanozymes are engineered nanomaterials with enzyme-like activities. Over the past decade, impressive progresses on nanozymes in biosensing have been made due to their unique advantages of high stability, low cost, and easy modification compared to natural enzymes. For many biosensors, it is critical to conjugate nanozymes to affinity ligands such as antibodies and aptamers. Since different nanomaterials have different surface properties, conjugation methods need to be compatible with these properties. In addition, the effect of biomolecules on nanozyme activity needs to be considered. In this review, we first categorized nanozyme-based biosensors into four parts, respectively describing noncovalent and covalent modifications with antibodies and aptamers. Meanwhile, recent advances in antibody and aptamer labeled nanozyme biosensors are summarized, and the methods of their conjugation are further illustrated. Finally, conclusions and future perspectives for the development and application of nanozyme bioconjugates are discussed.

Recent Progress in the Identification of Aptamers Against Bacterial Origins and Their Diagnostic Applications

Aptamers have gained an increasing role as the molecular recognition element (MRE) in diagnostic assay development, since their first conception thirty years ago. The process to screen for nucleic acid-based binding elements (aptamers) was first described in 1990 by the Gold Laboratory. In the last three decades, many aptamers have been identified for a wide array of targets. In particular, the number of reports on investigating single-stranded DNA (ssDNA) aptamer applications in biosensing and diagnostic platforms have increased significantly in recent years. This review article summarizes the recent (2015 to 2020) progress of ssDNA aptamer research on bacteria, proteins, and lipids of bacterial origins that have implications for human infections. The basic process of aptamer selection, the principles of aptamer-based biosensors, and future perspectives will also be discussed.

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 multifunctional plasmonic chip for bacteria capture, imaging, detection, and in situ elimination for wound therapy

A multifunctional plasmonic gold chip has been constructed for early diagnosis and highly effective killing of bacteria, which is critical for human health. The chip features high bacterial capture efficiency, plasmon-enhanced fluorescence (PEF) and surface-enhanced Raman scattering (SERS) and can act as a highly sensitive sensor for dual-mode bacteria imaging and detection (down to 102 CFU mL-1) with good reliability and accuracy. The developed assay can distinguish Gram-positive S. aureus bacteria from Gram-negative E. coli bacteria, providing valuable information for therapy. Importantly, the chip presents excellent photothermal antibacterial activity (98%) and can inactivate both Gram-positive and Gram-negative bacteria in situ. Furthermore, the chip was used to effectively promote the wound healing process in bacteria infected mice in vivo, showing great potential for antibacterial applications.

Ultrasensitive aptamer-based protein assays based on one-dimensional core-shell nanozymes

In enzyme-based immunoassys, the use of natural enzyme has been remarkably restricted by the inconvenience in preparation and storage, especially for point-of-care testing. Nanozymes, which can mimic the functions of natural enzymes, have been regarded as promising alternatives due to their robust stability and convenience in fabrication. Here we fabricated one-dimensional Fe₃O₄@C core-shell nanostructures via a solvent-thermal method. Thus prepared nanocomposites showed excellent peroxidase-like activity, capable of catalyzing chromogenic substrates into colored products in the presence of H₂O₂. We then developed a nanozyme-linked aptamer sorbent assay (NLASA) in a sandwich format, in which the as-prepared Fe₃O₄@C nanowires were employed as catalytic labels for colorimetric detection by naked eyes. In the detection of platelet-derived growth factor BB (PDGF-BB), this assay reliably exhibited detection limits as low as 10 fM, with a working range from 10 fM to 100 nM. By incorporating G-quadruplex-hemin DNAzyme with Fe₃O₄@C nanowires, the detection limit could be further lowered to 50 aM. The detection limit of PDGF-BB in 50% human serum was 100 fM. This ultrasensitive, cost-effective and easy-to-operate sensing platform offers new opportunities for protein detection in clinical diagnosis.