Nucleic acid amplification free biosensors for pathogen detection

Intelligent near-infrared light-activatable DNA machine with DNA wire nano-scaffold-integrated fast domino-like driving amplification for high-performance imaging in live biological samples

While there is significant potential for DNA machine-built enzyme-free fluorescence biosensors in the imaging analysis of live biological samples, they persist certain shortcomings. These encompass a deficiency of signal enrichment within a singular interface, uncontrolled premature activation during bio-delivery, and a slow reaction rate due to free nucleic acid collisions. In this contribution, we are committed to resolving the above challenges. Firstly, a single-interface-integrated domino-like driving amplification is constructed. In this conception, a specific target acts as the domino promotor (namely the energy source), initiating a cascading chain reaction that grafts onto a singular interface. Next, an 808 nm near-infrared (NIR) light-excited up-converting luminescence-induced light-activatable biosensing technique is introduced. By locking the target-specific identification segment with a photo-cleavage connector, the up-converted ultraviolet emission can activate target binding in a completely controlled manner. Moreover, a fast reaction rate is achieved by confining nucleic acid collisions within the surface of a DNA wire nano-scaffold, leading to a substantial enhancement in local contact concentration (30.8-fold increase, alongside a 15 times elevation in rate). When a non-coding microRNA (miRNA-221) is positioned as the model low-abundance target for proof-of-concept validation, our intelligent DNA machine demonstrates ultra-high sensitivity (with a limit of detection down to 62.65 fM) and good specificity for this hepatic malignant tumor-associated biomarker in solution detection. Going further, it is worth highlighting that the biosensing system can be employed to carry out high-performance imaging analysis in live bio-samples (ranging from the cellular level to the nude mouse body), thereby propelling the field of DNA machines in disease diagnosis.

A microfluidic chip platform based on Pt nanozyme and magnetized phage composite probes for dual-mode detecting and imaging pathogenic bacteria viability

The detection of pathogen viability is critically important to evaluate its infectivity. In the study, an integrated microfluidic chip based on dual-mode analytical strategy was developed to rapidly realize detection of bacteria activity (with Salmonella typhimurium, S.T, as a model analyte). Firstly, the composite probes, including deactivated phage modified magnetic beads and nano Pt-antimicrobial peptide (AMP) which can specifically recognize Gram-negative bacteria as nanozyme were prepared. When the composite probes are introduced into the chip together with target bacteria, after enrichment, oscillating and magnetic separation, they will conjugate with S.T and produce a magnetic sandwich complex. The complex can catalyze tetramethylbenzidine (TMB)-H2O2 to produce visible colorimetric signals which is correspondent to the total S.T content. Simultaneously, PtNPs in the complex can produce hydroxyl radical oxidation (∙OH) by decomposing H2O2. Under the synergistic action of ∙OH and AMP, the captured live S.T can be lysed to release ATP and emit bioluminescence signals which corresponds to the live S.T concentration. Therefore, the chip can simultaneously detect and image S.T at different viability in one test. The dual-mode assay demonstrated high sensitivity (≤33 CFU/mL), high specificity (identifying strain), signal amplification (5 folds) and short time (≤40min). The chip array can detect four samples in one test and exhibited advantages of high-integration, -sensitivity, -specificity and miniaturization, which are suitable to rapidly detect and image pathogen's viability in trace level. The replacement of phage probes can detect other bacteria. It has a wide prospect in pathogens screening.

An ultrasensitive genosensor for detection of toxigenic and non-toxigenic Clostridioides difficile based on a conserved sequence in surface layer protein coding gene

Clostridioides difficile (C. difficile) is the most common agent of antibiotic-associated diarrhea, leading to intestinal infection through the secretion of two major toxins. Not all strains of this bacterium are toxigenic, but some of them cause infection via their accessory virulence factors, such as surface layer protein (SlpA). SlpA is conserved in both toxigenic and non-toxigenic strains of C. difficile. In the present work, an amplification-free electrochemical genosensor was designed for the detection of the slpA gene. A glassy carbon electrode coated with gold nanoparticle-reduced graphene oxide nanocomposite was used as the working electrode, and its surface was modified using a simple thiolated linear oligonucleotide as the bioreceptor. Moreover, the hexaferrocenium tri[hexa(isothiocyanato) iron(III)] trihydroxonium (HxFc) complex was used as an intercalator, and its redox signal was recorded using differential pulse voltammetry. Scan rate studies indicated a quasi-reversible adsorption-controlled process for the HxFc complex. This genosensor showed high sensitivity with a limit of detection of 0.2 fM, a linear response range of 0.46-1900 fM, and a satisfactory specificity toward the synthetic slpA target gene. Also, the genosensor indicated responses in the mentioned linear range toward the genome extracted from either toxigenic or non-toxigenic strains of C. difficile.

Manipulation of magnetic beads for actively capturing Vibrio parahaemolyticus and nucleic acid based on microfluidic system

Rapid biological detection of pathogen micro-organisms has attracted much attention for practical biomedical applications. Despite the development in this field, it is still challenging to achieve simple and rapid biological detection using the microfluidic method. Herein, we propose a novel strategy of biological detection that combines precise detection control of the capillary microfluidic chip and versatile manipulation of magnetic beads. The microfluidic chip was fabricated via laser cutting, which utilized capillary pressure to realize rapid passive injection of liquid samples. Under an external magnetic field, the aptamer-modified magnetic beads were actuated to mix with Vibrio parahaemolyticus (V. parahaemolyticus) and its nucleic acid in the capillary microfluidic chip for rapid selective capture and detection, which could be achieved within 40 min. The experimental results demonstrated that V. parahaemolyticus could be captured using on-chip immunomagnetic beads with a high efficiency and significantly enhanced detection value. Due to these superior performances, the capillary microfluidic system, based on the manipulation of magnetic beads, demonstrated great potential for automatic biological detection.

Recent advances in microfluidic-based spectroscopic approaches for pathogen detection

Rapid identification of pathogens with higher sensitivity and specificity plays a significant role in maintaining public health, environmental monitoring, controlling food quality, and clinical diagnostics. Different methods have been widely used in food testing laboratories, quality control departments in food companies, hospitals, and clinical settings to identify pathogens. Some limitations in current pathogens detection methods are time-consuming, expensive, and laborious sample preparation, making it unsuitable for rapid detection. Microfluidics has emerged as a promising technology for biosensing applications due to its ability to precisely manipulate small volumes of fluids. Microfluidics platforms combined with spectroscopic techniques are capable of developing miniaturized devices that can detect and quantify pathogenic samples. The review focuses on the advancements in microfluidic devices integrated with spectroscopic methods for detecting bacterial microbes over the past five years. The review is based on several spectroscopic techniques, including fluorescence detection, surface-enhanced Raman scattering, and dynamic light scattering methods coupled with microfluidic platforms. The key detection principles of different approaches were discussed and summarized. Finally, the future possible directions and challenges in microfluidic-based spectroscopy for isolating and detecting pathogens using the latest innovations were also discussed.

A review of the recent achievements and future trends on 3D printed microfluidic devices for bioanalytical applications

3D printing has revolutionized the manufacturing process of microanalytical devices by enabling the automated production of customized objects. This technology promises to become a fundamental tool, accelerating investigations in critical areas of health, food, and environmental sciences. This microfabrication technology can be easily disseminated among users to produce further and provide analytical data to an interconnected network towards the Internet of Things, as 3D printers enable automated, reproducible, low-cost, and easy fabrication of microanalytical devices in a single step. New functional materials are being investigated for one-step fabrication of highly complex 3D printed parts using photocurable resins. However, they are not yet widely used to fabricate microfluidic devices. This is likely the critical step towards easy and automated fabrication of sophisticated, complex, and functional 3D-printed microchips. Accordingly, this review covers recent advances in the development of 3D-printed microfluidic devices for point-of-care (POC) or bioanalytical applications such as nucleic acid amplification assays, immunoassays, cell and biomarker analysis and organs-on-a-chip. Finally, we discuss the future implications of this technology and highlight the challenges in researching and developing appropriate materials and manufacturing techniques to enable the production of 3D-printed microfluidic analytical devices in a single step.

Investigation of the Efficacy of a Listeria monocytogenes Biosensor Using Chicken Broth Samples

Foodborne pathogens are microbes present in food that cause serious illness when the contaminated food is consumed. Among these pathogens, Listeria monocytogenes is one of the most serious bacterial pathogens, and causes severe illness. The techniques currently used for L. monocytogenes detection are based on common molecular biology tools that are not easy to implement for field use in food production and distribution facilities. This work focuses on the efficacy of an electrochemical biosensor in detecting L. monocytogenes in chicken broth. The sensor is based on a nanostructured electrode modified with a bacteriophage as a bioreceptor which selectively detects L. monocytogenes using electrochemical impedance spectroscopy. The biosensing platform was able to reach a limit of detection of 55 CFU/mL in 1× PBS buffer and 10 CFU/mL in 1% diluted chicken broth. The biosensor demonstrated 83-98% recovery rates in buffer and 87-96% in chicken broth.

Cascaded signal amplification strategy for ultra-specific, ultra-sensitive, and visual detection of Shigella flexneri

Pathogen infections including Shigella flexneri have posed a significant threat to human health for numerous years. Although culturing and qPCR were the gold standards for pathogen detection, time-consuming and instrument-dependent restrict their application in rapid diagnosis and economically less-developed regions. Thus, it is urgently needed to develop rapid, simple, sensitive, accurate, and low-cost detection methods for pathogen detection. In this study, an immunomagnetic beads-recombinase polymerase amplification-CRISPR/Cas12a (IMB-RPA-CRISPR/Cas12a) method was built based on a cascaded signal amplification strategy for ultra-specific, ultra-sensitive, and visual detection of S. flexneri in the laboratory. Firstly, S. flexneri was specifically captured and enriched by IMB (Shigella antibody-coated magnetic beads), and the genomic DNA was released and used as the template in the RPA reaction. Then, the RPA products were mixed with the pre-loaded CRISPR/Cas12a for fluorescence visualization. The results were observed by naked eyes under LED blue light, with a sensitivity of 5 CFU/mL in a time of 70 min. With no specialized equipment or complicated technical requirements, the IMB-RPA-CRISPR/Cas12a diagnostic method can be used for visual, rapid, and simple detection of S. flexneri and can be easily adapted to monitoring other pathogens.

Solid-Phase Extraction and Enhanced Amplification-Free Detection of Pathogens Integrated by Multifunctional CRISPR-Cas12a

Public healthcare demands effective and pragmatic diagnostic tools to address the escalating challenges in infection management in resource-limited areas. Recent advances in clustered regularly interspaced short palindromic repeat (CRISPR)-based biosensing promise the development of next-generation tools for disease diagnostics, including point-of-care (POC) testing for infectious diseases. The currently prevailing strategy of developing CRISPR/Cas-based diagnostics exploits only the target identification and trans-cleavage activity of a CRISPR-Cas12a/Cas13a system to provide diagnostic results, and they need to be combined with an additional preamplification reaction to enhance sensitivity. In contrast to this dual-function strategy, here, we present a new approach that collaboratively integrates the triple functions of CRISPR-Cas12a: target identification, sequence-specific enrichment, and signal generation. With this approach, we develop a nucleic acid assay termed Solid-Phase Extraction and Enhanced Detection Assay integrated by CRISPR-Cas12a (SPEEDi-CRISPR) that negates the need for preamplification but significantly improves the detection of limit (LOD) from the pM to fM level. Specifically, using Cas12a-coated magnetic beads, this assay combines efficient solid-phase extraction and enrichment of DNA targets enabled by the sequence-specific affinity of CRISPR-Cas12a with fluorogenic detection by activated Cas12a on beads. SPEEDi-CRISPR, for the first time, leverages the possibility of employing CRISPR/Cas12a in nucleic acid extraction and integrates the ability of both enrichment and detection of CRISPR/Cas into a single platform. Our proof-of-concept studies revealed that the SPEEDi-CRISPR assay has great specificity to distinguish HPV-18 from HPV-16, and Parvovirus B19, in addition to being able to detect HPV-18 at a concentration as low as 2.3 fM in 100 min and 4.7 fM in 60 min. Furthermore, we proved that this assay can be coupled with two point-of-care testing strategies: the smartphone-based fluorescence detector and the lateral flow assay. Overall, these results suggested that our assay could pave a new way for developing CRISPR diagnostics.

A Point-of-Care Nucleic Acid Quantification Method by Counting Light Spots Formed by LAMP Amplicons on a Paper Membrane

Nucleic acid quantification, allowing us to accurately know the copy number of target nucleic acids, is significant for diagnosis, food safety, agricultural production, and environmental protection. However, current digital quantification methods require expensive instruments or complicated microfluidic chips, making it difficult to popularize in the point-of-care detection. Paper is an inexpensive and readily available material. In this study, we propose a simple and cost-effective paper membrane-based digital loop-mediated isothermal amplification (LAMP) method for nucleic acid quantification. In the presence of DNA fluorescence dyes, the high background signals will cover up the amplicons-formed bright spots. To reduce the background fluorescence signals, a quencher-fluorophore duplex was introduced in LAMP primers to replace non-specific fluorescence dyes. After that, the amplicons-formed spots on the paper membrane can be observed; thus, the target DNA can be quantified by counting the spots. Take Vibrio parahaemolyticus DNA detection as an instance, a good linear relationship is obtained between the light spots and the copy numbers of DNA. The paper membrane-based digital LAMP detection can detect 100 copies target DNA per reaction within 30 min. Overall, the proposed nucleic acid quantification method has the advantages of a simple workflow, short sample-in and answer-out time, low cost, and high signal-to-noise, which is promising for application in resourced limited areas.

Efficient magnetic enrichment cascade single-step RPA-CRISPR/Cas12a assay for rapid and ultrasensitive detection of Staphylococcus aureus in food samples

Staphylococcus aureus (S. aureus) is a prevalent foodborne pathogen that could cause severe food poisoning. Thus, rapid, efficient, and ultrasensitive detection of S. aureus in food samples is urgently needed. Here, we report an efficient magnetic enrichment cascade single-step recombinase polymerase amplification (RPA)-CRISPR/Cas12a assay for the ultrasensitive detection of S. aureus. Magnetic beads (MBs) functionalized with S. aureus-specific antibodies were initially used for S. aureus enrichment from the complex matrix, with 98% capture efficiency in 5 min and 100-fold sensitivity improvement compared with unenriched S. aureus. Next, a single-step RPA-CRISPR/Cas12a-based diagnostic system with optimized extraction-free bacteria lysis was constructed. This assay could detect as low as 1 copy/μL (five copies/reaction) of extracted DNA template and 10 CFU/mL of S. aureus within 40 min. Furthermore, the assay could effectively detect S. aureus in real food samples such as lake water, orange juice, pork, and lettuce, with concordant results to qPCR assays. The proposed cascade signal-amplification assay eliminates the need for lengthy bacterial culture and complex sample preparation steps. Hence, the proposed assay shows great application potential for rapid, efficient, and ultrasensitive detection of pathogens in real food samples.

Recent progress on the CRISPR/Cas system in optical biosensors

Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) protein systems are adaptive immune systems unique to archaea and bacteria, with the characteristics of targeted recognition and gene editing to resist the invasion of foreign nucleic acids. Biosensors combined with the CRISPR/Cas system and optical detection technology have attracted much attention in medical diagnoses, food safety, agricultural progress, and environmental monitoring owing to their good sensitivity, high selectivity, and fast detection efficiency. In this review, we introduce the mechanism of CRISPR/Cas systems and developments in this area, followed by summarizing recent progress on CRISPR/Cas system-based optical biosensors combined with colorimetric, fluorescence, electrochemiluminescence and surface-enhanced Raman scattering optical techniques in various fields. Finally, we discuss the challenges and future perspectives of CRISPR/Cas systems in optical biosensors.

Ultraspecific One-Pot CRISPR-Based "Green-Yellow-Red" Multiplex Detection Strategy Integrated with Portable Cartridge for Point-of-Care Diagnosis

Versatile, informative, sensitive, and specific nucleic acid detection plays a crucial role in point-of-care pathogen testing, genotyping, and disease monitoring. In this study, we present a novel one-pot Cas12b-based method coupled with the "Green-Yellow-Red" strategy for multiplex detection. By integrating RT-LAMP amplification and Cas12b cleavage in a single tube, the entire detection process can be completed within 1 h. Our proposed method exhibits high specificity, enabling the discrimination of single-base mutations with detection sensitivity approaching single molecule levels. Additionally, the fluorescent results can be directly observed by the naked eye or automatically analyzed using our custom-designed software Result Analyzer. To realize point-of-care detection, we developed a portable cartridge capable of both heating and fluorescence excitation. In a clinical evaluation involving 20 potentially SARS-CoV-2-infected samples, our method achieved a 100% positive detection rate when compared to standard RT-PCR. Furthermore, the identification of SARS-CoV-2 variants using our method yielded results that were consistent with the sequencing results. Notably, our proposed method demonstrates excellent transferability, allowing for the simultaneous detection of various pathogens and the identification of mutations as low as 0.5% amidst a high background interference. These findings highlight the tremendous potential of our developed method for molecular diagnostics.

Ultrasensitive reporter DNA sensors built on nucleic acid amplification techniques: Application in the detection of trace amount of protein

The detection of protein is of great significance for the study of biological physiological function, early diagnosis of diseases and drug research. However, the sensitivity of traditional protein detection methods for detecting trace amount of proteins was relatively low. By integrating sensitive nucleic acid amplification techniques (NAAT) with protein detection methods, the detection limit of protein detection methods can be substantially improved. The DNA that can specifically bind to protein targets and convert protein signals into DNA signals is collectively referred to reporter DNA. Various NAATs have been used to establish NAAT-based reporter DNA sensors. And according to whether enzymes are involved in the amplification process, the NAAT-based reporter DNA sensors can be divided into two types: enzyme-assisted NAAT-based reporter DNA sensors and enzyme-free NAAT-based reporter DNA sensors. In this review, we will introduce the principles and applications of two types of NAAT-based reporter DNA sensors for detecting protein targets. Finally, the main challenges and application prospects of NAAT-based reporter DNA sensors are discussed.

Precise Detection of Viral RNA by Programming Multiplex Rolling Circle Amplification and Strand Displacement

Detection of viral infections (e.g., SARS-CoV-2) with high precision is critical to disease control and treatment. There is an urgent need to develop point-of-care detection methods to complement the gold standard laboratory-based PCR assay with comparable sensitivity and specificity. Herein, we developed a method termed mCAD to achieve ultraspecific point-of-care detection of SARS-CoV-2 RNA while maintaining high sensitivity by programming multiplex rolling circle amplification and toehold-mediated strand displacement reactions. RCA offers sufficient amplification of RNA targets for subsequent detection. Most importantly, a multilayer of detection specificity is implemented into mCAD via sequence-specific hybridization of nucleic acids across serial steps of this protocol to fully eliminate potential false-positive detections. Using mCAD, we demonstrated a highly specific, sensitive, and convenient visual detection of SARS-CoV-2 RNA from both synthetic and clinical samples, exhibiting performance comparable to qPCR. We envision that mCAD will find its broad applications in clinical prospects for nucleic acid detections readily beyond SARS-CoV-2 RNA.

Microfluidic Device-Based Virus Detection and Quantification in Future Diagnostic Research: Lessons from the COVID-19 Pandemic

The global economic and healthcare crises experienced over the past three years, as a result of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has significantly impacted the commonplace habits of humans around the world. SARS-CoV-2, the virus responsible for the coronavirus 2019 (COVID-19) phenomenon, has contributed to the deaths of millions of people around the world. The potential diagnostic applications of microfluidic devices have previously been demonstrated to effectively detect and quasi-quantify several different well-known viruses such as human immunodeficiency virus (HIV), influenza, and SARS-CoV-2. As a result, microfluidics has been further explored as a potential alternative to our currently available rapid tests for highly virulent diseases to better combat and manage future potential outbreaks. The outbreak management during COVID-19 was initially hindered, in part, by the lack of available quantitative rapid tests capable of confirming a person's active infectiousness status. Therefore, this review will explore the use of microfluidic technology, and more specifically RNA-based virus detection methods, as an integral part of improved diagnostic capabilities and will present methods for carrying the lessons learned from COVID-19 forward, toward improved diagnostic outcomes for future pandemic-level threats. This review will first explore the context of the COVID-19 pandemic and how diagnostic technology was shown to have required even greater advancements to keep pace with the transmission of such a highly infectious virus. Secondly, the historical significance of integrating microfluidic technology in diagnostics and how the different types of genetic-based detection methods may vary in their potential practical applications. Lastly, the review will summarize the past, present, and future potential of RNA-based virus detection/diagnosis and how it might be used to better prepare for a future pandemic.

Progress in quantum dot-based biosensors for microRNA assay: A review

MicroRNAs (miRNAs) are responsible for post-transcriptional gene regulation, and may function as valuable biomarkers for diseases diagnosis. Accurate and sensitive analysis of miRNAs is in great demand. Quantum dots (QDs) are semiconductor nanomaterials with superior optoelectronic features, such as high quantum yield and brightness, broad absorption and narrow emission, long fluorescence lifetime, and good photostability. Herein, we give a comprehensive review about QD-based biosensors for miRNA assay. Different QD-based biosensors for miRNA assay are classified by the signal types including fluorescent, electrochemical, electrochemiluminescent, and photoelectrochemical outputs. We highlight the features, principles, and performances of the emerging miRNA biosensors, and emphasize the challenges and perspectives in this field.

PCR-Free Innovative Strategies for SARS-CoV-2 Detection

The pandemic outbreak caused by SARS-CoV-2 coronavirus brought a crucial issue in public health causing up to now more than 600 million infected people and 6.5 million deaths. Conventional diagnostic methods are based on quantitative reverse transcription polymerase chain reaction (RT-qPCR assay) and immuno-detection (ELISA assay). However, despite these techniques have the advantages of being standardized and consolidated, they keep some main limitations in terms of accuracy (immunoassays), time/cost consumption of analysis, the need for qualified personnel, and lab constrain (molecular assays). There is crucial the need to develop new diagnostic approaches for accurate, fast and portable viral detection and quantification. Among these, PCR-free biosensors represent the most appealing solution since they can allow molecular detection without the complexity of the PCR. This will enable the possibility to be integrated in portable and low-cost systems for massive and decentralized screening of SARS-CoV-2 in a point-of-care (PoC) format, pointing to achieve a performant identification and control of infection. In this review, the most recent approaches for the SARS-CoV-2 PCR-free detection are reported, describing both the instrumental and methodological features, and highlighting their suitability for a PoC application.

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.

Recent Uses of Paper Microfluidics in Isothermal Nucleic Acid Amplification Tests

Isothermal nucleic acid amplification tests have recently gained popularity over polymerase chain reaction (PCR), as they only require a constant temperature and significantly simplify nucleic acid amplification. Recently, numerous attempts have been made to incorporate paper microfluidics into these isothermal amplification tests. Paper microfluidics (including lateral flow strips) have been used to extract nucleic acids, amplify the target gene, and detect amplified products, all toward automating the process. We investigated the literature from 2020 to the present, i.e., since the onset of the COVID-19 pandemic, during which a significant surge in isothermal amplification tests has been observed. Paper microfluidic detection has been used extensively for recombinase polymerase amplification (RPA) and its related methods, along with loop-mediated isothermal amplification (LAMP) and rolling circle amplification (RCA). Detection was conducted primarily with colorimetric and fluorometric methods, although a few publications demonstrated flow distance- and surface-enhanced Raman spectroscopic (SERS)-based detection. A good number of publications could be found that demonstrated both amplification and detection on paper microfluidic platforms. A small number of publications could be found that showed extraction or all three procedures (i.e., fully integrated systems) on paper microfluidic platforms, necessitating the need for future work.

Nucleic Acid Based Testing (NABing): A Game Changer Technology for Public Health

Timely and accurate detection of the causal agent of a disease is crucial to restrict suffering and save lives. Mere symptoms are often not enough to detect the root cause of the disease. Better diagnostics applied for screening at a population level and sensitive detection assays remain the crucial component of disease surveillance which may include clinical, plant, and environmental samples, including wastewater. The recent advances in genome sequencing, nucleic acid amplification, and detection methods have revolutionized nucleic acid-based testing (NABing) and screening assays. A typical NABing assay consists of three modules: isolation of the nucleic acid from the collected sample, identification of the target sequence, and final reading the target with the help of a signal, which may be in the form of color, fluorescence, etc. Here, we review current NABing assays covering the different aspects of all three modules. We also describe the frequently used target amplification or signal amplification procedures along with the variety of applications of this fast-evolving technology and challenges in implementation of NABing in the context of disease management especially in low-resource settings.

Simultaneous and rapid screening of live and dead E. coli O157:H7 with three signal outputs: An all-in-one biosensor using phage-apoferritin@CuO2 signal tags on MXenes-modified electrode platform

Simultaneous detection of live and dead bacteria is a huge challenge for food safety. To solve this issue, an all-in-one biosensor for bacteria was developed using the phage-apoferritin@CuO₂ (phage-Apo@CP) probe on an antimicrobial peptide (AMP)/MXenes-modified detection platform. With the specific recognition of AMP and phage-Apo@CP, the biosensor for the target Escherichia coli O157:H7 (E. coli O157:H7) presented multi-mode (bioluminescent, colorimetric, and electrochemical) signals to simultaneously measure live and dead bacteria. The bioluminescent signal caused by the adenosine triphosphate (ATP) from the bacteria was used to quantify live bacteria. The colorimetric and voltammetric signals triggered by ·OH and Cu²⁺ from the probe with the assistance of acid could rapidly screen and quantitative determination of total E. coli O157:H7 concentration. Thus, the dead one was obtained according to the total and live ones. All three signals could be mutually corrected to improve the accuracy. The biosensor was successfully used for on-site measurement of live and dead E. coli O157:H7 in food samples with the limit of detection of 30 CFU/mL for live ones and 6 CFU/mL for total bacteria within 50 min. This work presents a novel pathway for rapid and simultaneous quantification of both live and dead bacteria.

Hybridization chain reaction cascaded amplification platform for sensitive detection of pathogen

Rapid, sensitive, and accurate identification of pathogens is vital for preventing and controlling fish disease, reducing economic losses in aquaculture, and interrupting the spread of food-borne diseases in human populations. Herein, we proposed a hybridization chain reaction (HCR) cascaded dual-signal amplification platform for the ultrasensitive and specific detection of pathogenic microorganisms. A couple of specific primers for target bacterial 16S rRNAs were used to obtain amplified target single-stranded DNAs (AT-ssDNA). Then, AT-ssDNA initiated HCR amplification along with the opening of fluorophore (FAM) and a quencher (BHQ1) labeled hairpin reporter probe (H1), and the FAM fluorescence signal recovered. The proposed strategy could achieve a detection limit down to 0.31 CFU/mL for Staphylococcus aureus (S. aureus), 0.49 CFU/mL for Escherichia coli (E. coli) in buffer, and a linear range from 1 to 1 × 10⁶ CFU/mL for S. aureus, 1 to 1 × 10⁷ CFU/mL for E. coli. Furthermore, this platform enabled sensitive and precise detection of pathogenic microorganisms in complex samples such as fish blood and different organ tissues (large intestine, gallbladder, heart, liver, ren, gill, skin), which shows great potential in disease prevention and control in aquatic products.

Solid-Phase Extraction and Enhanced Amplification-Free Detection of Pathogens Integrated by Dual-Functional CRISPR-Cas12a

Public healthcare demands effective and pragmatic diagnostic tools to address the escalating challenges in infection management in resource-limited areas. Recent advance in CRISPR-based biosensing promises the development of next-generation tools for disease diagnostics, including point-of-care (POC) testing for infectious diseases. Currently prevailing strategy of developing CRISPR assays exploits only the non-specific trans-cleavage function of a CRISPR-Cas12a/Cas13a system for detection and combines it with an additional pre-amplification reaction to enhance the sensitivity. In contrast to this single-function strategy, here we present a new approach that collaboratively integrates the dual functions of CRISPR-Cas12a: sequence-specific binding and trans-cleavage activity. With this approach, we developed a POC nucleic acid assay termed Solid-Phase Extraction and Enhanced Detection assay Integrated by CRISPR-Cas12a (SPEEDi-CRISPR) that negates the need for preamplification but significantly improves the detection of limit (LOD) from the pM to fM level. Specifically, using Cas12a-coated magnetic beads, this assay combines efficient solid-phase extraction and enrichment of DNA targets enabled by the sequence-specific affinity of CRISPR-Cas12a with the fluorogenic detection by the activated Cas12a on beads. Our proof-of-concept study demonstrated that the SPEEDi-CRISPR assay affords an improved detection sensitivity for human papillomavirus (HPV)-18 with a LOD of 2.3 fM and excellent specificity to discriminate HPV-18 from HPV-16, Parvovirus B19, and scramble HPV-18. Furthermore, this robust assay was readily coupled with a portable smartphone-based fluorescence detector and a lateral flow assay for quantitative detection and visualized readout, respectively. Overall, these results should suggest that our dual-function strategy could pave a new way for developing the next-generation CRISPR diagnostics and that the SPEEDi-CRISPR assay provides a potentially useful tool for point-of-care testing.

Amplification-Free COVID-19 Detection by Digital Droplet REVEALR

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, exposed a pressing need for new public health tools for pathogen detection, disease diagnosis, and viral genotyping. REVEALR (RNA-encoded viral nucleic acid analyte reporter) is an isothermal DNAzyme-based point-of-care diagnostic that functions with a detection limit of ∼10 copies/μL when coupled with a preamplification step and can be utilized for viral genotyping of SARS-CoV-2 variants of concern through base pair mismatch recognition in a competitive binding format. Here, we describe an advanced REVEALR platform, termed digital droplet REVEALR (ddREVEALR), that can achieve direct viral detection and absolute sample quantitation utilizing a signal amplification strategy that relies on chemical modifications, DNAzyme multiplexing, and volume compression. Using an AI-assisted image-based readout, ddREVEALR was found to achieve 95% positive predictive agreement from a set of 20 nasal pharyngeal swabs collected at UCI Medical Center in Orange, California. We propose that the combination of amplification-free and protein-free analysis makes ddREVEALR a promising application for direct viral RNA detection of clinical samples.

Naked-eye on-site detection platform for Pasteurella multocida based on the CRISPR-Cas12a system coupled with recombinase polymerase amplification

Pasteurella multocida (P. multocida) is an important pathogenic bacterium that poses a serious threat to the development of the livestock economy and human health. Currently, the existing methods for P. multocida detection are time-consuming and require complex professional operations, limiting the application of field detection. In the study, we presented a single-pot naked-eye CRISPR-Cas12a platform (Cas12a-NEye) for the detection of P. multocida. The round tube cover allowed more Cas12a detection solution to be temporarily stored than the flat cap, enabling single-pot assays and avoiding aerosol contamination. The positive samples generated obvious red using naked eye using no excitation light and the negative samples generated blue. The limit of detection (LOD) was a single copy, without cross-reactivity with other closely related bacteria. Furthermore, we validated this platform using 16 P. multocida clinical lung samples and obtained consistent results with the real-time quantitative polymerase chain reaction (qPCR) method. The entire experimental process included rapid DNA extraction (<1 h) and Cas12a-NEye assay (25 min), which was accomplished within 1.5 h. Thus, this "sample-to-answer" platform has significant potential for P. multocida detection.

Environmental DNA/RNA for pathogen and parasite detection, surveillance, and ecology

Detection of pathogens, parasites, and other symbionts in environmental samples via eDNA/eRNA (collectively eNA) is an increasingly important source of information about their occurrence and activity. There is great potential for using such detections as a proxy for infection of host organisms in connected habitats, for pathogen monitoring and surveillance, and for early warning systems for disease. However, many factors require consideration, and appropriate methods developed and verified, in order that eNA detections can be reliably interpreted and adopted for surveillance and assessment of disease risk, and potentially inclusion in international standards, such as the World Organisation for Animal Health guidelines. Disease manifestation results from host-symbiont-environment interactions between hosts, demanding a multifactorial approach to interpretation of eNA signals.

A fast RT-qPCR system significantly shortens the time for SARS-CoV-2 nucleic acid test

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a serious threat to global development. Rapid and accurate diagnosis is critical for containing the pandemic and treating patients in time. As the gold standard for SARS-CoV-2 diagnosis, the qualitative reverse transcription-PCR (RT-qPCR) test has long been criticized for its long detection time. In this study, we optimized the primers and probes targeting SARS-CoV-2 ORF1ab and N gene designed by the Chinese Center for Disease Control and Preventions (CDC) to increase their Tm values to meet the optimal elongation temperature of Taq DNA polymerase, thus greatly shortened the elongation time. The higher elongation temperature in turn narrowed the temperature range of the reaction and saved more time. In addition, by shortening the distance between the fluorophore at the 5' end and the quencher in the middle we got a probe with higher signal-to-noise ratio. Finally, by using all these measures and optimized RT-qPCR program we successfully reduced the time (nucleic acid extraction step is not included) for nucleic acid test from 74 min to 26 min.

Stimulus-Responsive DNA Hydrogel Biosensors for Food Safety Detection

Food safety has always been a major global challenge to human health and the effective detection of harmful substances in food can reduce the risk to human health. However, the food industry has been plagued by a lack of effective and sensitive safety monitoring methods due to the tension between the cost and effectiveness of monitoring. DNA-based hydrogels combine the advantages of biocompatibility, programmability, the molecular recognition of DNA molecules, and the hydrophilicity of hydrogels, making them a hotspot in the research field of new nanomaterials. The stimulus response property greatly broadens the function and application range of DNA hydrogel. In recent years, DNA hydrogels based on stimulus-responsive mechanisms have been widely applied in the field of biosensing for the detection of a variety of target substances, including various food contaminants. In this review, we describe the recent advances in the preparation of stimuli-responsive DNA hydrogels, highlighting the progress of its application in food safety detection. Finally, we also discuss the challenges and future application of stimulus-responsive DNA hydrogels.

Piezocatalytic Medicine: An Emerging Frontier using Piezoelectric Materials for Biomedical Applications

Emerging piezocatalysts have demonstrated their remarkable application potential in diverse medical fields. In addition to their ultrahigh catalytic activities, their inherent and unique charge-carrier-releasing properties can be used to initiate various redox catalytic reactions, displaying bright prospects for future medical applications. Triggered by mechanical energy, piezocatalytic materials can release electrons/holes, catalyze redox reactions of substrates, or intervene in biological processes to promote the production of effector molecules for medical purposes, such as decontamination, sterilization, and therapy. Such a medical application of piezocatalysis is termed as piezocatalytic medicine (PCM) herein. To pioneer novel medical technologies, especially therapeutic modalities, this review provides an overview of the state-of-the-art research progress in piezocatalytic medicine. First, the principle of piezocatalysis and the preparation methodologies of piezoelectric materials are introduced. Then, a comprehensive summary of the medical applications of piezocatalytic materials in tumor treatment, antisepsis, organic degradation, tissue repair and regeneration, and biosensing is provided. Finally, the main challenges and future perspectives in piezocatalytic medicine are discussed and proposed, expecting to fuel the development of this emerging scientific discipline.

Identification of Mycobacterium tuberculosis in pulmonary and extrapulmonary specimens of Iranian hospitalized patients during 2017-2021

Background

Tuberculosis (TB) is one of the most serious public health problems worldwide which is a chronic infectious disease and is still one of the major challenges for developing countries. This study was undertaken to identify Mycobacterium TB (MTB) in clinical specimens in hospitalized patients.

Methods

The study was carried out on specimens from pulmonary and extrapulmonary suspected TB patients that were admitted to one of the largest tertiary hospitals located in Tehran, Iran from 2017 to 2021. The GeneXpert MTB/rifampin (RIF) method was applied to detect MTB and RIF resistance. Characteristics of demography, clinical features, and lifestyle were obtained from medical case records registered in the hospital.

Results

Of 957 specimens, 92 (9.61%) were found positive for TB by GeneXpert assay. Of positive samples, 72 (78.26%) were considered pulmonary TB, and 20 (21.73%) of them are associated with extrapulmonary involvement. Four (4.3%) positive TB cases were categorized as rifampicin-resistant.

Conclusion

This study showed a relatively high incidence rate of TB in distinct types of specimens in Iranian hospitalized patients but a low level of RIF resistance.

A Rapid and Simple Method for Purification of Nucleic Acids on Porous Membranes: Simulation vs. Experiment

Paper-based microfluidic systems have emerged as one of the most promising technologies for developing point-of-care diagnostic platforms (POCT) for detecting and monitoring various diseases. Saliva is a non-invasive biofluid easily collected, transported, and stored. Due to its accessibility and connection to systemic diseases, saliva is one of the best candidates for medical advancement at the point of care, where people can easily monitor their health. However, saliva is a complex mixture of DNA, RNA, proteins, exosomes, and electrolytes. Thus, nucleic acid separation from the salivary components is essential for PCR applications. Paper membranes are a highly porous and foldable structure capable of transporting fluids without pumps and sophisticated systems. The current work presents an insight into simulations for nucleic acid extraction on three types of porous paper membranes for use in point-of-care devices. The flow fluid model is solved on a COMSOL Multiphysics 5.3 free version platform, and the results are compared with experimental assays. The results show that pore uniformity, wet strength, porosity, and functional groups of MF1™ and Fusion 5™ paper membranes are vital parameters affecting nucleic acid extraction and PCR amplification efficiency.

Comparison of Biosensing Methods Based on Different Isothermal Amplification Strategies: A Case Study with Erwinia amylovora

Isothermal amplifications allow for the highly sensitive detection of nucleic acids, bypassing the use of instrumental thermal cycling. This work aimed to carry out an experimental comparison of the four most promising techniques: recombinase polymerase amplification (RPA) and loop-mediated isothermal amplification (LAMP) coupled with lateral flow test or coupled with additional amplification based on CRISPR/Cas12a resulting from the fluorescence of the Cas12a-cleaved probe. To compare the four amplification techniques, we chose the bacterial phytopathogen Erwinia amylovora (causative agent of fire blight), which has a quarantine significance in many countries and possesses a serious threat to agriculture. Three genes were chosen as the targets and primers were selected for each one (two for RPA and six for LAMP). They were functionalized by labels (biotin, fluorescein) at the 5' ends for amplicons recognition by LFT. As a result, we developed LAMP-LFT, LAMP-CRISPR/Cas, RPA-LFT, and RPA-CRISPR/Cas for E. amylovora detection. The detection limit was 10⁴ CFU/mL for LAMP-LFT, 10³ CFU/mL for LAMP-CRISPR/Cas, and 10² CFU/mL for RPA-LFT and RPA-CRISPR/Cas. The results of four developed test systems were verified by qPCR on a panel of real samples. The developed assays based on RPA, LAMP, CRISPR/Cas12a, and LFT are rapid (30-55 min), user-friendly, and highly sensitive for E. amylovora detection. All proposed detection methods can be applied to fire blight diagnosis and effective management of this disease.

Immunosensors-The Future of Pathogen Real-Time Detection

Pathogens and their toxins can cause various diseases of different severity. Some of them may be fatal, and therefore early diagnosis and suitable treatment is essential. There are numerous available methods used for their rapid screening. Conventional laboratory-based techniques such as culturing, enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) are dominant. However, culturing still remains the "gold standard" for their identification. These methods have many advantages, including high sensitivity and selectivity, but also numerous limitations, such as long experiment-time, costly instrumentation, and the need for well-qualified personnel to operate the equipment. All these existing limitations are the reasons for the continuous search for a new solutions in the field of bacteria identification. For years, research has been focusing on the use of immunosensors in various types of toxin- and pathogen-detection. Compared to the conventional methods, immunosensors do not require well-trained personnel. What is more, immunosensors are quick, highly selective and sensitive, and possess the potential to significantly improve the pathogen and toxin diagnostic-processes. There is a very important potential use for them in various transport systems, where the risk of contamination by bioagents is very high. In this paper, the advances in the field of immunosensor usage in pathogenic microorganism- and toxin-detection, are described.

CRISPR-Cas-based techniques for pathogen detection: Retrospect, recent advances, and future perspectives

BACKGROUND

Early detection of pathogen-associated diseases are critical for effective treatment. Rapid, specific, sensitive, and cost-effective diagnostic technologies continue to be challenging to develop. The current gold standard for pathogen detection, polymerase chain reaction technology, has limitations such as long operational cycles, high cost, and high technician and instrumentation requirements.

AIM OF REVIEW

This review examines and highlights the technical advancements of CRISPR-Cas in pathogen detection and provides an outlook for future development, multi-application scenarios, and clinical translation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Approaches enabling clinical detection of pathogen nucleic acids that are highly sensitive, specific, cheap, and portable are necessary. CRISPR-Cas9 specificity in targeting nucleic acids and "collateral cleavage" activity of CRISPR-Cas12/Cas13/Cas14 show significant promise in nucleic acid detection technology. These methods have a high specificity, versatility, and rapid detection cycle. In this paper, CRISPR-Cas-based detection methods are discussed in depth. Although CRISPR-Cas-mediated pathogen diagnostic solutions face challenges, their powerful capabilities will pave the way for ideal diagnostic tools.

Understanding the Origin of Tensile Response in a Graphene Textile Strain Sensor with Negative Differential Resistance

The flexible strain sensors based on the textile substrate have natural flexibility, high sensitivity, and wide-range tensile response. However, the textile's complex and anisotropic substructure leads to a negative differential resistance (NDR) response, lacking a deeper understanding of the mechanism. Therefore, we examined a graphene textile strain sensor with a conspicuous NDR tensile response, providing a requisite research platform for mechanism investigation. The pioneering measurement of single fiber bundles confirmed the existence of the NDR effect on the subgeometry scale. Based on the in situ characterization of tensile morphology and measurement, we conducted quantitative behavior analyses to reveal the origin of tensile electrical responses in the full range comprehensively. The results showed that the dominant factor in generating the NDR effect is the relative displacement of fibers within the textile bundles. Based on the neural spiking-like tensile response, we further demonstrated the application potential of the textile strain sensor in threshold detection and near-sensor signal processing. The proposed NDR behavior model would provide a reference for the design and application of wearable intelligent textiles.

Research progress on detection techniques for point-of-care testing of foodborne pathogens

The global burden of foodborne disease is enormous and foodborne pathogens are the leading cause of human illnesses. The detection of foodborne pathogenic bacteria has become a research hotspot in recent years. Rapid detection methods based on immunoassay, molecular biology, microfluidic chip, metabolism, biosensor, and mass spectrometry have developed rapidly and become the main methods for the detection of foodborne pathogens. This study reviewed a variety of rapid detection methods in recent years. The research advances are introduced based on the above technical methods for the rapid detection of foodborne pathogenic bacteria. The study also discusses the limitations of existing methods and their advantages and future development direction, to form an overall understanding of the detection methods, and for point-of-care testing (POCT) applications to accurately and rapidly diagnose and control diseases.

Electromagnetically-driven integrated microfluidic platform using reverse transcription loop-mediated isothermal amplification for detection of severe acute respiratory syndrome coronavirus 2

Rapid, sensitive and accurate diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is of great need for effective quarantining and treatment. Real-time reverse-transcription polymerase chain reaction requiring thermocyling has been commonly used for diagnosis of SARS-CoV-2 though it may take two to 4 h before lengthy sample pretreatment process and require bulky apparatus and well-trained personnel. Since multiple reverse transcription loop-mediated isothermal amplification (multiple RT-LAMP) process without thermocycling is sensitive, specific and fast, an electromagnetically-driven microfluidic chip (EMC) was developed herein to lyse SARS-CoV-2 viruses, extract their RNAs, and perform qualitative analysis of three marker genes by on-chip multiple RT-LAMP in an automatic format within 82 min at a limit of detection of only ∼5000 copies per reaction (i.e. 200 virus/ μL). This compact EMC may be especially promising for SARS-CoV-2 diagnostics in resource-limited countries.

Isothermal circular strand displacement-based assay for microRNA detection in liquid biopsy

Extracellular miRNAs are promising targets for developing new assays for the early diagnosis and prognosis of diseases based on liquid biopsy. The detection of miRNAs in liquid biopsies is challenged by their short sequence length, low concentration, and interferences with bodily fluid components. Isothermal circular strand displacement polymerization has emerged as a convenient method for nucleic acid amplification and detection. Herein, we describe an innovative strategy for microRNA detection directly from biological fluids based on hairpin probe–assisted isothermal amplification reaction. We designed and optimized the assay to detect target analytes in 1 µL of the complex media’s biological matrix using a microfluidic device for the straightforward analysis of multiple samples. We validated the assay to detect circulating miR-127-5p in synovial fluid, recently indicated as a predictive biomarker for osteoarthritis disease. The combined use of a mutant polymerase operating with high yield and a primer incorporating locked nucleic acid nucleosides allowed detection of miR-127-5p with 34 fmol L⁻¹ LOD. We quantified circulating miR-127-5p directly in synovial fluid, thus demonstrating that the assay may be employed for the convenient detection of 4.3 ± 0.5 pmol L⁻¹ concentrated miRNAs in liquid biopsy samples.

A Review on Potential Electrochemical Point-of-Care Tests Targeting Pandemic Infectious Disease Detection: COVID-19 as a Reference

Fast and accurate point-of-care testing (POCT) of infectious diseases is crucial for diminishing the pandemic miseries. To fight the pandemic coronavirus disease 2019 (COVID-19), numerous interesting electrochemical point-of-care (POC) tests have been evolved to rapidly identify the causal organism SARS-CoV-2 virus, its nucleic acid and antigens, and antibodies of the patients. Many of those electrochemical biosensors are impressive in terms of miniaturization, mass production, ease of use, and speed of test, and they could be recommended for future applications in pandemic-like circumstances. On the other hand, self-diagnosis, sensitivity, specificity, surface chemistry, electrochemical components, device configuration, portability, small analyzers, and other features of the tests can yet be improved. Therefore, this report reviews the developmental trend of electrochemical POC tests (i.e., test platforms and features) reported for the rapid diagnosis of COVID-19 and correlates any significant advancements with relevant references. POCTs incorporating microfluidic/plastic chips, paper devices, nanomaterial-aided platforms, smartphone integration, self-diagnosis, and epidemiological reporting attributes are also surfed to help with future pandemic preparedness. This review especially screens the low-cost and easily affordable setups so that management of pandemic disease becomes faster and easier. Overall, the review is a wide-ranging package for finding appropriate strategies of electrochemical POCT targeting pandemic infectious disease detection.

A switchable Cas12a enabling CRISPR-based direct histone deacetylase activity detection

The efficient and robust signal reporting ability of CRISPR-Cas system exhibits huge value in biosensing, but its applicability for non-nucleic acid analyte detection relies on the coupling of additional recognition modules. To address this limitation, we described a switchable Cas12a and exploited it for CRISPR-based direct analysis of histone deacetylase (HDAC) activity. Starting from the acetylation-mediated inactivation of Cas12a by anti-CRISPR protein AcrVA5, we demonstrated that the acetyl-inactivated Cas12a could be reversibly activated by HDAC-mediated deacetylation based on computational simulations (e.g., deep learning and protein-protein docking analysis) and experimental verifications. By leveraging this switchable Cas12a for both target sensing and signal amplification, we established a sensitive one-pot assay capable of detecting deacetylase sirtuin-1 with sub-nanomolar sensitivity, which is 50 times lower than the standard two-step peptide-based assay. The versability of this assay was validated by the sensitive assessment of cellular HDAC activities in different cell lines with good accuracy, making it a valuable tool for biochemical studies and clinical diagnostics.

Advances, limitations, and prospects of biosensing technology for detecting phytopathogenic bacteria

Phytopathogenic bacteria cause severe economic losses in agricultural production worldwide. The spread rates, severity, and emerging plant bacterial diseases have become serious threat to the sustainability of food sources and the fruit industry. Detection and diagnosis of plant diseases are imperative in order to manage plant diseases in field conditions, greenhouses, and food storage conditions as well as to maximize agricultural productivity and sustainability. To date, various techniques including, serological, observation-based, and molecular methods have been employed for plant disease detection. These methods are sensitive and specific for genetic identification of bacteria. However, these methods are specific for genetic identification of bacteria. Currently, the innovative biosensor-based disease detection technique is an attractive and promising alternative. A biosensor system involves biological recognition and transducer active receptors based on sensors used in plant-bacteria diagnosis. This system has been broadly used for the rapid diagnosis of plant bacterial pathogens. In the present review, we have discussed the conventional methods of bacterial-disease detection, however, the present review mainly focuses on the applications of different biosensor-based techniques along with point-of-care (POC), robotics, and cell phone-based systems. In addition, we have also discussed the challenges and limitations of these techniques.

Bio-piezoelectricity: fundamentals and applications in tissue engineering and regenerative medicine

In recent years, smart materials have piqued the interest of scientists and physicians in the biomedical community owing to their ability to modify their properties in response to an external stimulation or changes in their surroundings. Biocompatible piezoelectric materials are an interesting group of smart materials due to their ability to produce electrical charges without an external power source. Electric signals produced by piezoelectric scaffolds can renew and regenerate tissues through special pathways like that found in the extracellular matrix. This review summarizes the piezoelectric phenomenon, piezoelectric effects generated within biological tissues, piezoelectric biomaterials, and their applications in tissue engineering and their use as biosensors.

Facile, Rapid, and Low-Cost Detection for Influenza Viruses and Respiratory Syncytial Virus Based on a Catalytic DNA Assembly Circuit

Influenza viruses and respiratory syncytial virus (RSV) have contributed to severe respiratory infections, causing huge economic and healthcare burdens. To achieve rapid and precise detection of influenza viruses and RSV, we proposed a catalytic hairpin assembly (CHA) combined with the lateral flow immunoassay (CHA-LFIA) detection method. The presence of the target RNA triggers the initiation of CHA circuits. H1/H2 complexes, the amplified signal products, which were labeled with digoxin and biotin, were detected with a highly sensitive lateral flow immunoassay system. The sensitivity of the CHA-LFIA system to influenza A and B viruses and RSV reached up to 1, 1, and 5 pM, respectively. In addition, this method exhibited excellent capability for differentiating between target RNA and base-mismatched RNA. The results demonstrated that an enzyme-free, rapid, highly sensitive, and specific method had been developed to detect influenza A and B viruses and RSV.