Using commercially available personal glucose meters for portable quantification of DNA

New sensing methods using commercially available products: Based on PGM and PTS

In recent years, detection technology has made remarkable progress in the field of food safety, in vitro diagnosis, and environment monitoring under the impetus of trace substances detection requirements. However, in sharp contrast to the rapid development of detection technology, its marketization process is relatively lagging behind. One possible approach is to integrate novel sensing strategies with mature commercial devices, such as personal glucose meters (PGMs) and pregnancy test strips (PTS) to speed up their marketization process. In this review, we systematically summarized design principle, evolution, and application progress for the integration of novel sensing strategies with commercial devices PGMs and PTS. Meanwhile, key factors and difficulties for the integration novel sensing strategies with commercial devices were emphasized. More importantly, the future of prospects and remaining challenges were discussed.

Microvolumetric determination of thrombomodulin based on competitive immunoreaction using a portable glucometer

A new method of reducing the amount of reagent and sample for determination of thrombomodulin (TM) was developed based on competitive immunoreaction using a portable glucometer (PGM). Two types of nanocomposites, TM protein-modified magnetic nanoparticles (MNPs-TM) and TM antibody-/glucose oxidase-modified gold nanoparticles (Ab-GNPs-GOx), were prepared. Their binding product, MNPs-TM-Ab-GNPs-GOx, in the microvolumetric solution was used to catalyze the oxidation of glucose, leading to a decline of the glucose content. The TM-involved competitive immunoreaction had a negative effect on the generation of MNPs-/GNPs-based nanocomposites and inhibited the catalytic oxidation of glucose. The glucose content difference in the microvolumetric solution, which was revealed by a PGM, was in proportion to the logarithm of the TM concentration from 25 ng mL-1 to 2.5 μg mL-1. The limit of detection was 5.7 ng mL-1. Microvolumetric solution and a PGM were used in the measurement, which overcame some deficiencies of classical methods in chemo/biosensing, for example, special instrument, complicated measurement procedure, and high cost.

A personal glucose meter-utilized strategy for portable and label-free detection of hydrogen peroxide

Rapid and precise detection of hydrogen peroxide (H2O2) holds great significance since it is linked to numerous physiological and inorganic catalytic processes. We herein developed a label-free and washing-free strategy to detect H2O2 by employing a hand-held personal glucose meter (PGM) as a signal readout device. By focusing on the fact that the reduced redox mediator ([Fe(CN)6]4-) itself is responsible for the final PGM signal, we developed a new PGM-based strategy to detect H2O2 by utilizing the target H2O2-mediated oxidation of [Fe(CN)6]4- to [Fe(CN)6]3- in the presence of horseradish peroxidase (HRP) and monitoring the reduced PGM signal in response to the target amount. Based on this straightforward and facile design principle, H2O2 was successfully determined down to 3.63 μM with high specificity against various non-target molecules. We further demonstrated that this strategy could be expanded to identify another model target choline by detecting H2O2 produced through its oxidation promoted by choline oxidase. Moreover, we verified its practical applicability by reliably determining extracellular H2O2 released from the breast cancer cell line, MDA-MB-231. This work could evolve into versatile PGM-based platform technology to identify various non-glucose target molecules by employing their corresponding oxidase enzymes, greatly advancing the portable biosensing technologies.

Nanotechnology in the Diagnosis and Treatment of Antibiotic-Resistant Infections

The development of antimicrobial resistance (AMR), along with the relative reduction in the production of new antimicrobials, significantly limits the therapeutic options in infectious diseases. Thus, novel treatments, especially in the current era, where AMR is increasing, are urgently needed. There are several ongoing studies on non-classical therapies for infectious diseases, such as bacteriophages, antimicrobial peptides, and nanotechnology, among others. Nanomaterials involve materials on the nanoscale that could be used in the diagnosis, treatment, and prevention of infectious diseases. This review provides an overview of the applications of nanotechnology in the diagnosis and treatment of infectious diseases from a clinician's perspective, with a focus on pathogens with AMR. Applications of nanomaterials in diagnosis, by taking advantage of their electrochemical, optic, magnetic, and fluorescent properties, are described. Moreover, the potential of metallic or organic nanoparticles (NPs) in the treatment of infections is also addressed. Finally, the potential use of NPs in the development of safe and efficient vaccines is also reviewed. Further studies are needed to prove the safety and efficacy of NPs that would facilitate their approval by regulatory authorities for clinical use.

Recent Advances in Personal Glucose Meter-Based Biosensors for Food Safety Hazard Detection

Food safety has emerged as a significant concern for global public health and sustainable development. The development of analytical tools capable of rapidly, conveniently, and sensitively detecting food safety hazards is imperative. Over the past few decades, personal glucose meters (PGMs), characterized by their rapid response, low cost, and high degree of commercialization, have served as portable signal output devices extensively utilized in the construction of biosensors. This paper provides a comprehensive overview of the mechanism underlying the construction of PGM-based biosensors, which consists of three fundamental components: recognition, signal transduction, and signal output. It also detailedly enumerates available recognition and signal transduction elements, and their modes of integration. Then, a multitude of instances is examined to present the latest advancements in the application of PGMs in food safety detection, including targets such as pathogenic bacteria, mycotoxins, agricultural and veterinary drug residues, heavy metal ions, and illegal additives. Finally, the challenges and prospects of PGM-based biosensors are highlighted, aiming to offer valuable references for the iterative refinement of detection techniques and provide a comprehensive framework and inspiration for further investigations.

Advanced biosensors for mycotoxin detection incorporating miniaturized meters

Advanced biosensors, considered as emerging technologies, are capable of accurate, quantitative and real-time analysis for point-of-care testing (POCT) applications. Moreover, the integrating of miniaturized meters into these advanced biosensors makes them ideally appropriate for portable, sensitive and selective detection of biomolecules. Miniaturized meters including PGMs (personal glucose meters), thermometer, pressuremeter, pH meter, etc. are the most accurate devices and wide availability in the market, exhibiting a promising potential towards detection of small molecule mycotoxins. In this article, we introduce and analyze the recent advancements for sensing of mycotoxins measured by handheld meters since the first report in 2012. Furthermore, limitations and challenges for versatile meters application against mycotoxins in food matrix are highlighted. By overcoming the bottleneck problems, we believe the miniaturized meters-based biosensor platform will provide great possibilities for mycotoxins analysis and launch them to the market.

Aptamer-based rapid diagnosis for point-of-care application

Aptasensors have attracted considerable interest and widespread application in point-of-care testing worldwide. One of the biggest challenges of a point-of-care (POC) is the reduction of treatment time compared to central facilities that diagnose and monitor the applications. Over the past decades, biosensors have been introduced that offer more reliable, cost-effective, and accurate detection methods. Aptamer-based biosensors have unprecedented advantages over biosensors that use natural receptors such as antibodies and enzymes. In the current epidemic, point-of-care testing (POCT) is advantageous because it is easy to use, more accessible, faster to detect, and has high accuracy and sensitivity, reducing the burden of testing on healthcare systems. POCT is beneficial for daily epidemic control as well as early detection and treatment. This review provides detailed information on the various design strategies and virus detection methods using aptamer-based sensors. In addition, we discussed the importance of different aptamers and their detection principles. Aptasensors with higher sensitivity, specificity, and flexibility are critically discussed to establish simple, cost-effective, and rapid detection methods. POC-based aptasensors' diagnostic applications are classified and summarised based on infectious and infectious diseases. Finally, the design factors to be considered are outlined to meet the future of rapid POC-based sensors.

Overcoming Major Barriers to Developing Successful Sensors for Practical Applications Using Functional Nucleic Acids

For many years, numerous efforts have been focused on the development of sensitive, selective, and practical sensors for environmental monitoring, food safety, and medical diagnostic applications. However, the transition from innovative research to commercial success is relatively sparse. In this review, we identify four scientific barriers and one technical barrier to developing successful sensors for practical applications, including the lack of general methods to (a) generate receptors for a wide range of targets, (b) improve sensor selectivity to overcome interferences, (c) transduce the selective binding to different optical, electrochemical, and other signals, and (d) tune dynamic range to match thresholds of detection required for different targets; and the costly development of a new device. We then summarize solutions to overcome these barriers using sensors based on functional nucleic acids that include DNAzymes, aptamers, and aptazymes and how these sensors are coupled to widely available measurement devices to expand their capabilities and lower the barrier for their practical applications in the field and point-of-care settings.

A versatile CRISPR Cas12a-based point-of-care biosensor enabling convenient glucometer readout for ultrasensitive detection of pathogen nucleic acids

Pathogen nucleic acid detection is of great significance to control the spread of diseases caused by the viruses. Nevertheless, traditional methods for nucleic acid detection such as polymerase chain reaction (PCR) and oligonucleotide microarrays require bulky instruments, which restrain their point-of-care (POC) testing application. Here, we proposed a POC method enabling sensitive detection of pathogen nucleic acids by combining the clustered regularly interspaced short palindromic repeat (CRISPR) Cas12a-based assay and personal glucometer readout (PGM). The quantification of target pathogen DNA by PGM was achieved based on pathogen DNA activates Cas12a ssDNase to cleave magnetic bead-DNA-invertase reporter probe, and separated free invertase to catalyze hydrolysis of sucrose to glucose. Without using nucleic acid amplification technology, we demonstrated here dual signal amplifications based on Cas12a and invertase-mediated catalytic reactions, making it possible to sensitively detect HIV-related DNA or SARS-CoV-2 pseudovirus with the limits of detection of 11.0 fM and 50 copies/μL, respectively. This strategy also showed excellent selectivity as well as potential applicability for detection of HIV in human serum samples or of SARS-CoV-2 in saliva samples. Therefore, our CRISPR-PGM-based dual signal amplifications detection platform might offer a great promise in POC diagnosis of pathogen nucleic acids.

Diagnosis of disease relevant nucleic acid biomarkers with off-the-shelf devices

Changes in the level of nucleic acids in blood may be correlated with some clinical disorders like cancer, stroke, trauma and autoimmune diseases, and thus, nucleic acids can serve as potential biomarkers for pathological processes. The requirement of technical equipment and operator expertise in effective information readout of modern molecular diagnostic technologies significantly restricted application outside clinical laboratories. The ability to detect nucleic acid biomarkers with off-the-shelf devices, which have the advantages of portability, simplicity, low cost and short response time, is critical to provide a prompt clinical result in circumstances where the laboratory instruments are not available. This review throws light on the current strategies and challenges for nucleic acid diagnosis with commercial portable devices, indicating the future prospect of portable diagnostic devices and making a great difference in improving the healthcare and disease surveillance in resource-limited areas.

Rapid Detection and Antimicrobial Susceptibility Testing of Pathogens Using AgNPs-Invertase Complexes and the Personal Glucose Meter

Rapid detection of pathogens and assessment of antimicrobial susceptibility is of great importance for public health, especially in resource-limiting regions. Herein, we developed a rapid, portable, and universal detection method for bacteria using AgNPs-invertase complexes and the personal glucose meter (PGM). In the presence of bacteria, the invertase could be released from AgNPs-invertase complexes where its enzyme activity of invertase was inhibited. Then, the enzyme activity of invertase was restored and could convert sucrose into glucose measured by a commercially PGM. There was a good linear relationship between PGM signal and concentration of E. coli or S. aureus as the bacteria model with high sensitivity. And our proposed biosensor was proved to be a rapid and reliable method for antimicrobial susceptibility testing within 4 h with consistent results of Minimum Inhibitory Concentrations (MICs) testing, providing a portable and convenient method to treat infected patients with correct antibiotics and reduce the production of antibiotic-resistant bacteria, especially for resource-limiting settings.

Advances in the DNA Nanotechnology for the Cancer Biomarkers Analysis: Attributes and Applications

The most commonly used clinical methods are enzyme-linked immunosorbent assay (ELISA) and quantitative PCR (qPCR) in which ELISA was applied for the detection of protein biomarkers and qPCR was especially applied for nucleic acid biomarker analysis. Although these constructed methods have been applied in wide range, they also showed some inherent shortcomings such as low sensitivity, large sample volume and complex operations. At present, many methods have been successfully constructed on the basis of DNA nanotechnology with the merits of high accuracy, rapid and simple operation for cancer biomarkers assay. In this review, we summarized the bioassay strategies based on DNA nanotechnology from the perspective of the analytical attributes for the first time and discussed and the feasibility of the reported strategies for clinical application in the future.

Photothermal Detection of MicroRNA Using a Horseradish Peroxidase-Encapsulated DNA Hydrogel With a Portable Thermometer

MicroRNA (miRNA) detection has attracted widespread interest as a tumor detection marker. In this work, a miRNA-responsive visual and temperature sensitive probe composed of a horseradish peroxidase (HRP)-encapsulated DNA hydrogel was designed and synthesized. The biosensor converted the miRNA hybridization signal to a photothermal effect which was measured using a digital thermometer. The substrate DNA linker strand of the hydrogel hybridizes with different sequences of miRNA resulting in the collapse of the hydrogel and the release of HRP. HRP oxidizes 3,3',5,5'-tetramethylbenzidine (TMB) resulting in a color change and a strong photothermal effect was observed after shining near-infrared light on the oxidized product. The thermometer-based readout method has a wide linear range (0.5-4.0 µM) and a limit of detection limit of 7.8 nM which is comparable with traditional UV-vis absorption spectrometry detection and quantitative real time polymerase chain reaction methods. The low cost, ease of operation, and high sensitivity shows that this biosensor has potential for point-of-care biomolecular detection and biomedical applications.

Amplification-free smartphone-based attomolar HBV detection

Classical gold standard HBV detection relies on expensive devices and complicated procedures, thus is always restricted in large-scale hospitals and centers for disease control and prevention. To extend HBV detection to primary clinics especially in underdeveloped areas, we design amplification-free smartphone-based attomolar HBV detecting technique based on single molecule sensing. Verified by synthesized HBV target DNA, this technique reaches a detection limit at attomolar concentration (100 aM); and verified by 110 clinical samples, it also reaches a rather high sensitivity of 10⁴ copy/mL (≈2000 IU/mL) with a high accuracy of 93.64% certificated by gold standard HBV detecting devices. Besides, this technique can quantify HBV viral load in 70 min only using portable and inexpensive devices as well as simple operations. Because of its cost-effective, field-portable and operable design, highly sensitive and selective detecting capability and wireless data connectivity, this technique can be potentially used in mobile HBV diagnoses and share HBV epidemic information especially in resource limited situations.

Portable quantification of silver ion by using personal glucose meter (PGM) and magnetite cross-linked invertase aggregates (MCLIA)

Heavy metal detection is critical due to its harmful effects on human health and the ecosystem. Enzyme-based platforms attract attention for heavy metal detection such as silver, a toxic metal, due to being small, portable, and requiring only essential equipment compared with the basic analytical methods. In this study, magnetic cross-linked invertase aggregates (MCLIA) were developed for the first time as an enzyme-based signaling platform to detect Ag⁺ using a personal glucose meter (PGM). EDX, FTIR, and VSM results depicted that MCLIA was successfully developed and exhibits super-paramagnetism. In addition, MCLIA selectively detected the Ag⁺ at a sensitivity of 1.2 inhibition rate/μM in a linear range from 5 to 70 μM with a detection limit of 4.6 μM and IC₅₀ value of 42.3 μM. These findings strongly indicate that MCLIA is applicable as a signal platform for portable quantification of other analytes that inhibits the invertase enzyme.

Point-of-Care Analyte Quantification and Digital Readout via Lysate-Based Cell-Free Biosensors Interfaced with Personal Glucose Monitors

Field-deployable diagnostics based on cell-free systems have advanced greatly, but on-site quantification of target analytes remains a challenge. Here we demonstrate that Escherichia coli lysate-based cell-free biosensors coupled to a personal glucose monitor (PGM) can enable on-site analyte quantification, with the potential for straightforward reconfigurability to diverse types of analytes. We show that analyte-responsive regulators of transcription and translation can modulate the production of the reporter enzyme β-galactosidase, which in turn converts lactose into glucose for PGM quantification. Because glycolysis is active in the lysate and would readily deplete converted glucose, we decoupled enzyme production and glucose conversion to increase the end point signal output. However, this lysate metabolism did allow for one-pot removal of glucose present in complex samples (like human serum) without confounding target quantification. Taken together, our results show that integrating lysate-based cell-free biosensors with PGMs enables accessible target detection and quantification at the point of need.

Immunoglobulin E Detection Method Based on Cascade Enzymatic Reaction Utilizing Portable Personal Glucose Meter

We herein describe a cascade enzymatic reaction (CER)-based IgE detection method utilizing a personal glucose meter (PGM), which relies on alkaline phosphatase (ALP) activity that regulates the amount of adenosine triphosphate (ATP). The amount of sandwich assay complex is determined according to the presence or absence of the target IgE. Additionally, the ALP in the sandwich assay catalyzes the dephosphorylation of ATP, a substrate of CER, which results in the changes in glucose level. By employing this principle, IgE was reliably detected at a concentration as low as ca. 29.6 ng/mL with high specificity toward various proteins. Importantly, the limit of detection (LOD) of this portable PGM-based approach was comparable to currently commercialized ELISA kit without expensive and bulky analysis equipment as well as complexed washing step. Finally, the diagnostic capability of this method was also successfully verified by reliably detecting IgE present in a real human serum sample with an excellent recovery ratio within 100 ± 6%.

Biosensing with DNAzymes

This article provides a comprehensive review of biosensing with DNAzymes, providing an overview of different sensing applications while highlighting major progress and seminal contributions to the field of portable biosensor devices and point-of-care diagnostics. Specifically, the field of functional nucleic acids is introduced, with a specific focus on DNAzymes. The incorporation of DNAzymes into bioassays is then described, followed by a detailed overview of recent advances in the development of in vivo sensing platforms and portable sensors incorporating DNAzymes for molecular recognition. Finally, a critical perspective on the field, and a summary of where DNAzyme-based devices may make the biggest impact are provided.

Recent advances of using personal glucose meter as a biosensor readout for non-glucose targets

Background

Personal glucose meter (PGM) has become the most successful biosensor in past decades due to its advantages of small size, convenient operation, and low cost. To take advantage of many years of research and development of PGMs, new signal transduction methods has been developed to expand the PGM from simple monitoring blood glucose to detection of numerous non-glucose targets.

Objectives

This review summarizes recent advance of PGM-based biosensors for non-glucose targets including signal transduction, signal amplification and target molecule recognition and analysis. Current challenges and future directions are also discussed.

Conclusion

PGM can be used as biosensor readout to detect various non-glucose targets from metal ion, small molecule to protein and even living organisms such as bacteria and other pathogens by using different signal transduction elements such as invertase and amylase, and different signal amplification methods such as nanomaterials, nucleic acid reaction, liposome encapsulation, hydrogel trapping, DNAzyme amplification and biotin-streptavidin reaction.

Duplex-Specific Nuclease-Assisted CRISPR-Cas12a Strategy for MicroRNA Detection Using a Personal Glucose Meter

A CRISPR-Cas system holds great promise as a next-generation biosensing technology for molecular diagnostics. Nevertheless, the current CRISPR-Cas12a-based detection strategies always need bulky instruments or auxiliary devices to obtain a quantitative signal output, which restrains its point-of-care testing application. Herein, we proposed a duplex-specific nuclease-assisted CRISPR-Cas12a strategy to detect microRNA (miRNA) with a personal glucose meter. The target miRNA was first converted into an amplified initiator DNA via duplex-specific nuclease. Afterward, the initiator DNA activated the collateral cleavage activity of CRISPR-Cas12a to cleave the single-strand DNA (ssDNA) linker on sucrase-ssDNA-modified magnetic beads, which led to the release of sucrase. The released sucrase was collected and then utilized to catalyze sucrose to glucose, which could be quantitatively detected by a personal glucose meter. The change in the glucose signal directly reflected the concentration of miRNA, which avoided expensive equipment for signal quantification. Two different miRNAs (miRNA21 and miRNA205) could be detected by simply changing the sequence of the template strand (H strand). The developed strategy showed high sensitivity with a limit of detection (LOD) of 2.4 and 1.1 pM for miRNA21 and miRNA205, respectively. In addition, good selectivity and anti-interference ability were achieved using this method, which enabled it promising for miRNA detection at the point-of-care.

Hybridization Chain Reaction-Amplified Electrochemical DNA-Based Sensors Enable Calibration-Free Measurements of Nucleic Acids Directly in Whole Blood

Hybridization chain reaction (HCR) amplification strategy has been extensively explored for the application of electrochemical DNA-based sensors. Despite the enhancement in its sensitivity using the HCR, such sensor platform exhibited significant sensor-to-sensor variations in current due to variations in probe counts and lengths. To circumvent this, we are developing here a calibration-free "O-N" approach to generate a ratiometric, unitless value that is independent of these variations. Specifically, this approach employs two types of redox reporters, denoted as "One reporter" and "N reporters", with the former attached on the capture DNA and the latter on H1 and H2 strands. By optimizing the attachment sites of these reporters onto DNA strands, we demonstrate a significantly enhanced sensitivity of such sensor platform by four orders of magnitude, achieving accurate, calibration-free measurement of nucleic acids including ctDNA directly in undiluted whole blood without the requirement to calibrate each individual sensor.

Recent progress of personal glucose meters integrated methods in food safety hazards detection

Development of personal glucose meters (PGMs) for blood glucose monitoring and management by the diabetic patients has been a long history since its first invention in 1968 and commercial application in 1975. The main reasons for its wide acceptance and popularity can be attributed mainly to the easy operation, test-to-result model, low cost, and small volume of sample required for blood glucose concentration test. During past decades, advances in analytical techniques have repurposed the use of PGMs into a general point-of-care testing platform for a variety of non-glucose targets, especially the food hazards. In this review, we summarized the recent published research using PGMs to detect the food safety hazards of mycotoxins, illegal additives, pathogen bacteria, and pesticide and veterinary drug residues detection with PGMs. The progress on PGM-based detection achieved in food safety have been carefully compared and analyzed. Furthermore, the current bottlenecks and challenges for practical applications of PGM for hazards detection in food safety have also been proposed.

Installing CRISPR-Cas12a sensors in a portable glucose meter for point-of-care detection of analytes

Integrating CRISPR-Cas12a sensors with a portable glucose meter (PGM) was developed based on the target-induced activation of the collateral cleavage activity of Cas12a. Considering the portability, low cost and facile incorporation of the PGM system with suitable Cas12a sensors to recognize many targets, the CRISPR/Cas12a-PGM system demonstrated here paves a way to further broaden the POC applications of CRISPR-based diagnostics.

In-situ generation of potassium ferricyanide for label-free and enzyme-free chemiluminescence detection of telomerase activity

Chemiluminescence (CL) assay is a promising point-of-care testing (POCT) technology due to the fast response, high sensitivity, and easy miniaturization. The application and performance of CL POCT method were highly dependent on the CL reaction. Herein, based on the CL reaction between luminol and in-situ generated K₃Fe(CN)₆, a low-cost, enzyme-free, and label-free CL POCT method was explored via a portable and handheld luminometer to detect telomerase activity. Telomerase elongated telomere substrate (TS) primer to form (TTAGGG)_n repeats which hybridize with multiple short DNAs. The intercalation of SYBR Green I (SGI) into double-stranded DNA (dsDNA) generated singlet oxygen under the irradiation of LED light source. Singlet oxygen was then employed for in-situ oxidation of K₄Fe(CN)₆ to K₃Fe(CN)₆, which could react with luminol to generate a strong CL intensity. Thus, telomerase activity could be specifically, sensitively, and label-free detected. The detection limit was down to 98 HeLa cells. The detection process was very simple, and the cost was about $0.01 for each measurement. Furthermore, telomerase activity was detectable in human serum samples, with spike recoveries from 96% to 105%. According to our knowledge, it is the first effort to develop a low-cost, label-free and enzyme-free CL method with good repeatability for detecting biomarker based on the analyte-triggered and in-situ generated K₃Fe(CN)₆/luminol CL reaction.

Dual cascade isothermal amplification reaction based glucometer sensors for point-of-care diagnostics of cancer-related microRNAs

The practical use of a point-of-care (POC) device is of particular interest in performing liquid biopsies related to cancer. Herein, taking advantage of the practical convenience of a commercially available personal glucose meter (PGM), we report a convenient, low-cost and sensitive detection strategy for circulating microRNA-155 (miRNA155) in human serum. First, miRNA155 in serum triggers the catalyzed hairpin assembly (CHA) reaction, and then the CHA product is specifically captured by the peptide nucleic acid (PNA) probes attached to the surface of a 96-well plate, which in turn triggers the hybridization chain reaction (HCR), resulting in the local enrichment of invertase. Next, introduction of a substrate (sucrose) for the invertase results in the generation of glucose, which can be detected by a PGM. In this sensor, neutrally charged PNA (12 nt) is more likely to hybridize with the CHA products than with the negatively charged DNA in kinetics, which improves the detection sensitivity and specificity. Due to the synergistic isothermal amplification reaction between CHA and HCR, the sensor is able to achieve a broad dynamic range (from 1 fM to 10 nM) with a detection limit down to 0.36 fM (3 orders of magnitude lower than that without HCR) and is capable of distinguishing single-base mismatched sequences. Thus the convenient, sensitive, robust and low-cost PGM sensor makes on-site nucleic acids detection possible, suggesting its great application prospect as a promising POC device in cancer diagnostics.

DNAzyme Amplified Aptasensing Platform for Ochratoxin A Detection Using a Personal Glucose Meter

Aptamer-based sensors have emerged as a major platform for detecting small-molecular targets, because aptamers can be selected to bind these small molecules with higher affinity and selectivity than other receptors such as antibodies. However, portable, accurate, sensitive, and affordable detection of these targets remains a challenge. In this work, we developed an aptasensing platform incorporating magnetic beads and a DNAzyme for signal amplification, resulting in high sensitivity. The biosensing platform was constructed by conjugating a biotin-labeled aptamer probe of small-molecular targets such as toxins and a biotin-labeled substrate strand on magnetic beads, and the DNAzyme strand hybridized with the aptamer probe to block the substrate cleavage activity. The specific binding of the small-molecular target by the aptamer probe can replace the DNAzyme strand and then induce the hybridization between the DNAzyme strand and substrate strand, and the iterative signal amplification reaction of hydrolysis and cleavage of the substrate chain occurs in the presence of a metal ion cofactor. Using invertase to label the substrate strand, the detection of small molecules of the toxin is successfully transformed into the measurement of glucose, and the sensitive analysis of small molecules such as toxins can be realized by using the household portable glucose meter as a readout. This platform is shown to detect ochratoxin, a common toxin in food, with a linear detection range of 5 orders of magnitude, a low detection limit of 0.88 pg/mL, and good selectivity. The platform is easy to operate and can be used as a potential choice for quantitative analysis of small molecules, at home or under point-of-care settings. Moreover, by changing and designing the aptamer probe and the arm of DNAzyme strand, it can be used for the analysis of other analytes.

A glucose meter interface for point-of-care gene circuit-based diagnostics

Recent advances in cell-free synthetic biology have given rise to gene circuit-based sensors with the potential to provide decentralized and low-cost molecular diagnostics. However, it remains a challenge to deliver this sensing capacity into the hands of users in a practical manner. Here, we leverage the glucose meter, one of the most widely available point-of-care sensing devices, to serve as a universal reader for these decentralized diagnostics. We describe a molecular translator that can convert the activation of conventional gene circuit-based sensors into a glucose output that can be read by off-the-shelf glucose meters. We show the development of new glucogenic reporter systems, multiplexed reporter outputs and detection of nucleic acid targets down to the low attomolar range. Using this glucose-meter interface, we demonstrate the detection of a small-molecule analyte; sample-to-result diagnostics for typhoid, paratyphoid A/B; and show the potential for pandemic response with nucleic acid sensors for SARS-CoV-2.

Getting synthetic biology circuit-based sensors into field applications is still a challenge. Here the authors combine a circuit sensor with a glucose meter for small analyte and nucleic acid detection.

Catalytic hairpin assembly mediated liposome-encoded magnetic beads for signal amplification of peroxide test strip based point-of-care testing of ricin

Herein, we propose a new peroxide test strip (PTS) based point-of-care testing (POCT) method to detect ricin B-chain qualitatively and quantitatively by using catalytic hairpin assembly (CHA) mediated liposome-encoded magnetic beads for signal amplification. The sensitivity of this PTS based POCT method was improved significantly because it combined CHA signal amplification and liposome-based signal amplification.

New Uses for the Personal Glucose Meter: Detection of Nucleic Acid Biomarkers for Prostate Cancer Screening

A personal glucose meter (PGM)-based method for quantitative detection of a urinary nucleic acid biomarker in prostate cancer screening, the so-called PCA3, is reported herein. A sandwich-type genoassay is conducted on magnetic beads to collect the target from the sample by specific hybridization, making the assay appropriate for PCA3 detection in biological fluids. The success of the method hinges on the use of alkaline phosphatase (ALP) to link the amount of nucleic acid biomarker to the generation of glucose. In particular, specifically attached ALP molecules hydrolyze D-glucose-1-phosphate into D-glucose, thus enabling the amplification of the recorded signal on the personal glucose meter. The developed genoassay exhibits good sensitivity (3.3 ± 0.2 mg glucose dL-1 pM-1) for PCA3, with a dynamic range of 5 to 100 pM and a quantification limit of 5 pM. Likewise, it facilitates point-of-care testing of nucleic acid biomarkers by using off-the-shelf PGM instead of complex instrumentation involved in traditional laboratory-based tests.

Simple and label-free strategy for terminal transferase assay using a personal glucose meter

We herein developed a simple personal glucose meter (PGM)-based method for terminal transferase (TdT) activity assay by utilizing the glucose oxidase (GOx)-mimicking activity of cerium oxide nanoparticles (CeO₂ NPs). Using this strategy, the TdT activity was reliably determined down to 0.7 U mL^-1 with high selectivity against other non-specific enzymes.

An aptasensor for the detection of ampicillin in milk using a personal glucose meter

Antibiotic residues in foods have aroused wide public concern because of their potential side-effects. It is imperative to develop a simple, accurate and reliable method for the detection of antibiotic residues in foods. In this paper, we report a novel, facile and sensitive method for the detection of ampicillin in milk using a commercial personal glucose meter (PGM). Magnetic beads (MBs) were employed as the platform, an ampicillin aptamer was used as the recognition element and streptavidin was utilized as the bridge to link invertase and the aptamer. After the hydrolysis of sucrose to glucose, the concentration of glucose was quantitatively measured using the PGM. The difference of PGM signals with and without addition of ampicillin exhibits a good linear correlation with the logarithm of ampicillin concentrations in the range of 2.5 × 10-10 mol L-1 to 1.0 × 10-7 mol L-1 with a detection limit of 2.5 × 10-10 mol L-1 (S/N = 3). Finally, the proposed method was successfully applied for the detection of ampicillin residue in milk.

Homogeneous and universal transduction of various nucleic acids to an off-shelf device based on programmable toehold switch sensing

Through a rational construction of an RNA toehold switch sensor, the glucometer-based detection of nucleic acids was innovatively simplified into a completely homogeneous and label-free process. Compared with traditional strategies that rely on multiple operations such as chemical conjugation and bead separation, this new strategy is more robust, user-friendly, reagent-saving, and reproducible, and can be universally adapted for use on extensive target species, e.g. herein, the real-world pathogen genes.

Glucose oxidase-like activity of cerium oxide nanoparticles: use for personal glucose meter-based label-free target DNA detection

Recently, personal glucose meter (PGM) has been utilized for the detection of non-glucose targets for point-of-care (POC) testing. Aimed at this goal, we herein developed a new PGM-based label-free read-out method for polymerase chain reaction (PCR) based on our novel finding that cerium oxide nanoparticles (CeO2 NPs) exhibit glucose oxidase-like activity comparable to the natural glucose oxidase enzyme. Methods: In principle, DNA amplicons produced by PCR in the presence of target DNA electrostatically bind to CeO2 NPs, leading to their aggregation and reducing the efficiency for CeO2 NP-catalyzed glucose oxidation reaction. Thus, glucose is hardly oxidized to gluconic acid, resulting in the maintenance of initial high glucose level. On the contrary, in the absence of target DNA or presence of non-target DNA, DNA amplicons are not produced and glucose is effectively oxidized by the glucose oxidase-like activity of CeO2 NPs, leading to the significant reduction of glucose level. Finally, the resulting glucose level is simply measured by using PGM. Results: With this strategy, DNA amplicons were quantitatively examined within 5 min, realizing ultrafast analysis of PCR results without any cumbersome and labor-intensive procedures. In addition, the target genomic DNA derived from Escherichia coli (E. coli) was sensitively determined down to 10 copies with high selectivity. Conclusion: Importantly, the use of PGM as a detection component enables its direct application in POC settings. Based on the meritorious features of PGM such as rapidity, simplicity, and cost-effectiveness, we expect that the devised system could serve as a core platform for the on-site read-out of PCR amplification.

Translating in vitro diagnostics from centralized laboratories to point-of-care locations using commercially-available handheld meters

There is a growing demand for high-performance point-of-care (POC) diagnostic technologies where in vitro diagnostics (IVD) is fundamental for prevention, identification, and treatment of many diseases. Over the past decade, a shift of IVDs from the centralized laboratories to POC settings is emerging. In this review, we summarize recent progress in translating IVDs from centralized labs to POC settings using commercially available handheld meters. After introducing typical workflows for IVDs and highlight innovative technologies in this area, we discuss advantages of using commercially available handheld meters for translating IVDs from centralized labs to POC settings. We then provide comprehensive coverage of different signal transduction strategies to repurpose the commercially-available handheld meters, including personal glucose meter, pH meter, thermometer and pressure meter, for detecting a wide range of targets by integrating biochemical assays with the meters for POC testing. Finally, we identify remaining challenges and offer future outlook in this area.

An in vitro site-specific cleavage assay of CRISPR-Cas9 using a personal glucose meter

Personal glucose meter has been applied to sensitively and cost-effectively detect the in vitro site-specific cleavage efficiency of CRISPR-Cas9.

DNA template-mediated click chemistry-based portable signal-on sensor for ochratoxin A detection

A novel signal-on portable sensing system has been developed for OTA detection using personal glucose meter (PGM) as signal transducer. In the study, we explore the potential of using a short dsDNA as template to trigger the "click" ligation of two DNA strands, further improve the stability of DNA strand on the magnetic beads (MBs) surface, and thereby reduce the background signal. Compared with no "click" ligation, the background signal decreases 7.5 times. Both the sensitivity and selectivity are greatly promoted. A high sensitivity with OTA detection down to 72 pg/mL is achieved, which is comparable with several existing detectors, such as fluorescence-based detectors and electrochemical detectors. The feasibility of the strategy in real samples is well verified and evaluated by detecting OTA in feed samples, indicating the potential application in the food safety field.