Portable glucose meter: trends in techniques and its potential application in analysis

Point-Of-Care Ultra-Portable Single-Molecule Bioassays for One-Health

Screening asymptomatic organisms (humans, animals, plants) with a high-diagnostic accuracy using point-of-care-testing (POCT) technologies, though still visionary holds great potential. Convenient surveillance requires easy-to-use, cost-effective, ultra-portable but highly reliable, in-vitro-diagnostic devices that are ready for use wherever they are needed. Currently, there are not yet such devices available on the market, but there are a couple more promising technologies developed at readiness-level 5: the Clustered-Regularly-Interspaced-Short-Palindromic-Repeats (CRISPR) lateral-flow-strip tests and the Single-Molecule-with-a-large-Transistor (SiMoT) bioelectronic palmar devices. They both hold key features delineated by the World-Health-Organization for POCT systems and an occurrence of false-positive and false-negative errors <1-5% resulting in diagnostic-selectivity and sensitivity >95-99%, while limit-of-detections are of few markers. CRISPR-strip is a molecular assay that, can detect down to few copies of DNA/RNA markers in blood while SiMoT immunometric and molecular test can detect down to a single oligonucleotide, protein marker, or pathogens in 0.1mL of blood, saliva, and olive-sap. These technologies can prospectively enable the systematic and reliable surveillance of asymptomatic ones prior to worsening/proliferation of illnesses allowing for timely diagnosis and swift prognosis. This could establish a proactive healthcare ecosystem that results in effective treatments for all living organisms generating diffuse and well-being at efficient costs.

Monitoring saliva compositions for non-invasive detection of diabetes using a colorimetric-based multiple sensor

The increasing population of diabetic patients, especially in developing countries, has posed a serious risk to the health sector, so that the lack of timely diagnosis and treatment process of diabetes can lead to threatening complications for the human lifestyle. Here, a multiple sensor was fabricated on a paper substrate for rapid detection and controlling the progress of the diabetes disease. The proposed sensor utilized the sensing ability of porphyrazines, pH-sensitive dyes and silver nanoparticles in order to detect the differences in saliva composition of diabetic and non-diabetic patients. A unique color map (sensor response) was obtained for each studied group, which can be monitored by a scanner. Moreover, a good correlation was observed between the colorimetric response resulting from the analysis of salivary composition and the fasting blood glucose (FBG) value measured by standard laboratory instruments. It was also possible to classify participants into two groups, including patients caused by diabetes and those were non-diabetic persons with a total accuracy of 88.9%. Statistical evaluations show that the multiple sensor can be employed as an effective and non-invasive device for continuous monitoring of diabetes, substantially in the elderly.

Portable dual-mode biosensor based on smartphone and glucometer for on-site sensitive detection of Listeria monocytogenes

Contamination of Listeria monocytogenes (L. monocytogenes) in the environment and food can pose a serious threat to human health, and there is an urgent need to establish sensitive on-situ detection methods to mitigate its hazards. In this study, we have developed a field assay that combines magnetic separation technology with antibody-labeled ZIF-8 encapsulating glucose oxidase (GOD@ZIF-8@Ab) to capture and specifically identify L. monocytogenes while GOD catalyzes glucose catabolism to produce signal changes in glucometers. On the other side, horseradish peroxidase (HRP) and 3,3',5,5'-tetramethylbenzidine (TMB) were added to recombined with the H₂O₂ generated by the catalyst to form a colorimetric reaction system that changes from colorless to blue. The smartphone software was used for RGB analysis to complete the on-site colorimetric detection of L. monocytogenes. This dual-mode biosensor showed good detection performance for the on-site application of L. monocytogenes in lake water and juice samples, both with a limit of detection up to 10¹ CFU/mL and a good linear range of 10¹-10⁶ CFU/mL. Therefore, this dual-mode on-site detection biosensor has a promising application for the early screening of L. monocytogenes in environmental and food samples.

Coupling hCG-based protease sensors with a commercial pregnancy test strip for simple analyses of protease activities

Proteases play an essential role in many cellular processes, and consequently, abnormalities in their activities are related to various diseases. Methods have been developed to measure the activity of these enzymes, but most involve sophisticated instruments or complicated procedures, which hampers the development of a point-of-care test (POCT). Here, we propose a strategy for developing simple and sensitive methods to analyze protease activity using commercial pregnancy test strips that detect human chorionic gonadotropin (hCG). hCG was engineered to have site-specific conjugated biotin and a peptide sequence, which can be cleaved by a target protease, between hCG and biotin. hCG protein was immobilized on streptavidin-coated beads, resulting in a protease sensor. The hCG-immobilized beads were too large to flow through the membrane of the hCG test strip and yielded only one band in the control line. When the peptide linker was hydrolyzed by the target protease, hCG was released from the beads, and the signal appeared in both the control and test lines. Three protease sensors for matrix metalloproteinase-2, caspase-3, and thrombin were constructed by replacing the protease-cleavable peptide linker. The combination of the protease sensors and a commercial pregnancy strip enabled the specific detection of each protease in the picomolar range, with a 30-min incubation of the hCG-immobilized beads and samples. The modular design of the protease sensor and simple assay procedure will facilitate the development of POCTs for various protease disease markers.

Au@bovine serum albumin nanoparticle-based acid-resistant nanozyme quartz crystal microbalance sensing of urine glucose

A robust, efficient and sensitive quartz crystal microbalance (QCM) for glucose detection has been constructed using Au@bovine serum albumin (Au@BSA) nanoparticles as an active layer. The nanoparticles serve as tandem nanozymes and their stability over natural enzymes enable the sensor to show a wider linear dynamic range between 0.05 and 15 mM, a higher acid-resistance (pH 2.0-8.0) and heat-resistance (35-60 °C) than conventional glucose oxidase (GOx)-based sensors. The sensor has been further applied to measure glucose content in artificial urine directly without dilution, where the recovery of 99.6-105.2% and the relative standard deviations (RSDs) below 0.88% confirm a good reproducibility for the measurement results. In addition, the developed Au@BSA QCM sensor can retain 95% of its initial activity after 40 days of storage. Overall, the Au@BSA sensor shows better comprehensive performance than the commercial sensor strips for urine glucose analysis and provides a promising approach in a more precise and robust manner.

Flexible biochemical sensors for point-of-care management of diseases: a review

Health problems have been widely concerned by all mankind. Real-time monitoring of disease-related biomarkers can feedback the physiological status of human body in time, which is very helpful to the diseases management of healthcare. However, conventional non-flexible/rigid biochemical sensors possess low fit and comfort with the human body, hence hindering the accurate and comfortable long-time health monitoring. Flexible and stretchable materials make it possible for sensors to be continuously attached to the human body with good fit, and more precise and higher quality results can be obtained. Thus, tremendous attention has been paid to flexible biochemical sensors in point-of-care (POC) for real-time monitoring the entire disease process. Here, recent progress on flexible biochemical sensors for management of various diseases, focusing on chronic and communicable diseases, is reviewed, and the detection principle and performance of these flexible biochemical sensors are discussed. Finally, some directions and challenges are proposed for further development of flexible biochemical sensors.

Perception of veterinarians on monitoring diabetic cats with emphasis on the flash glucose monitoring system

ABSTRACT This study aimed to understand the perception of veterinarians regarding monitoring blood and interstitial glucose levels in cats with diabetes mellitus and/or diabetic ketoacidosis, with emphasis on the flash glucose monitoring system (FGMS) (FreeStyle Libre, Abbott, Brazil). This research consisted of two stages. In all, 516 response forms were obtained, and of these, 480 (93%) were considered valid. In total, 333 (69.4%) veterinarians did not use the FGMS, while 147 (30.6%) did. The cost of the FGMS (116, 78%) was the greatest deterrent to acceptability. Veterinarians who use the device consider it indispensable in the hospital monitoring of diabetic ketoacidosis and a facilitator in the accurate monitoring of measurements. In addition, the preferred location for application of the sensor is the cranial lateral wall of the chest and it is quite tolerable. Monitoring a diabetic cat requires commitment from the owner and the veterinary team to ensure feline-friendly management.

Colorimetric assay based on NiCo2S4@N,S-rGO nanozyme for sensitive detection of H2O2 and glucose in serum and urine samples

Traditional bimetallic sulfide-based nanomaterials often have a small specific surface area (SSA), low dispersion, and poor conductivity, thereby limiting their wide applications in the nanozyme-catalytic field. To address the above issues, we herein integrated NiCo2S4 with N,S-rGO to fabricate a nanocomposite (NiCo2S4@N,S-rGO), which showed a stronger peroxidase-mimetic activity than its pristine components. The SSA (155.8 m2 g-1) of NiCo2S4@N,S-rGO increased by ∼2-fold compared to NiCo2S4 with a pore size of 7-9 nm, thus providing more active sites and charge transfer channels. Based on the Michaelis-Menten equation, the affinity of this nanocomposite increased 40% and 1.1∼10.6-fold compared with NiCo2S4 with N,S-rGO, respectively, highlighting the significant enhancement of the peroxidase-like activity. The enhanced activity of this nanocomposite is derived from the joint participation of ˙OH, ˙O2 -, and photogenerated holes (h+), and was dominated by h+. To sum up, N,S-codoping, rich S-vacancies, and multi-valence states for this nanocomposite facilitate electron transfer and accelerate reaction processes. The nanocomposite-based colorimetric sensor gave low detection limits for H2O2 (12 μM) and glucose (0.3 μM). In comparison with the results detected by a common glucose meter, this sensor provided the relative recoveries across the range of 97.4-101.8%, demonstrating its high accuracy. Moreover, it exhibited excellent selectivity for glucose assay with little interference from common co-existing macromolecules/ions, as well as high reusability (>6 times). Collectively, the newly developed colorimetric sensor yields a promising methodology for practical applications in H2O2 and glucose detection with advantages of highly visual resolution, simple operation, convenient use, and satisfactory sensitivity.

An ultra-compact and wireless tag for battery-free sweat glucose monitoring

Glucose monitoring before, during, and after exercise is essential for people with diabetes as exercise increases the risk of activity-induced hyper- and hypo-glycemic events. The situation is even more challenging for athletes with diabetes as they have impaired metabolic control compared to sedentary individuals. In this regard, a compact and noninvasive wearable glucose monitoring device that can be easily worn is critical to enabling glucose monitoring. This report presents an ultra-compact glucose tag with a footprint and weight of 1.2 cm² and 0.13 g, respectively, for sweat analysis. The device comprises a near field communication (NFC) chip, antenna, electrochemical sensor, and microfluidic channels implemented in different material layers. The device has a flexible and conformal structure and can be easily attached to different body parts. The battery-less operation of the device was enabled by NFC-based wireless power transmission and the compact antenna. Femtosecond laser ablation was employed to fabricate a highly compact and flexible NFC antenna. The proposed device demonstrated excellent operating characteristics with a limit of detection (LOD), limit of quantification (LOQ), and sensitivity of 24 μM, 74 μM, and 1.27 μA cm^-2 mM^-1, respectively. The response of the proposed sensor in sweat glucose detection and quantification was validated by nuclear magnetic resonance spectroscopy (NMR). Also, the device's capability in attachment to the body, sweat collection, and glucose measurement was demonstrated through in vitro and in vivo experiments, and satisfactory results were obtained.

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.

A Microfluidic PET-Based Electrochemical Glucose Sensor

Paper-based microfluidic sensors have gained increased attention in the field of analytical assays in recent years due to their self-driven nature, ease of preparation, high integration, low reagent consumption, and low cost. However, paper-based microfluidic sensors still have many deficiencies when it comes to the detection of some specific detectors such as blood glucose. For example, the processing procedure for microfluidic channels is tedious, the sensor electrodes are easily damaged by bending, and they can only be used as disposable products. To solve the above problems, a PET-based microfluidic sensor was proposed in this paper, the performance of which was tested with glucose as the target detector. The experimental results showed that the analytical performance of this sensor is comparable to that of existing commercial glucose meters. This work provides implications for the substrate selection of microfluidic chips for some biochemical analyses.

Emergence of microneedles as a potential therapeutics in diabetes mellitus

Diabetes mellitus is a severe condition in which the pancreas produces inadequate insulin or the insulin generated is ineffective for utilisation by the body; as a result, insulin therapy is required for control blood sugar levels in patients having type 1 diabetes and is widely recommended in advanced type 2 diabetes patients with uncontrolled diabetes despite dual oral therapy, while subcutaneous insulin administration using hypodermic injection or pump-mediated infusion is the traditional route of insulin delivery and causes discomfort, needle phobia, reduced adherence, and risk of infection. Therefore, transdermal insulin delivery has been extensively explored as an appealing alternative to subcutaneous approaches for diabetes management which not only is non-invasive and easy, but also avoids first-pass metabolism and prevents gastrointestinal degradation. Microneedles have been commonly investigated in human subjects for transdermal insulin administration because they are minimally invasive and painless. The different types of microneedles developed for the transdermal delivery of anti-diabetic drugs are discussed in this review, including solid, dissolving, hydrogel, coated, and hollow microneedles. Numerous microneedle products have entered the market in recent years. But, before the microneedles can be effectively launched into the market, a significant amount of investigation is required to address the numerous challenges. In conclusion, the use of microneedles in the transdermal system is an area worth investigating because of its significant benefits over the oral route in the delivery of anti-diabetic medications and biosensing of blood sugar levels to assure improved clinical outcomes in diabetes management.

Portable, quantitative, and sequential monitoring of copper ions and pyrophosphate based on a DNAzyme-Fe3O4 nanosystem and glucometer readout

In this report, portable, quantitative, and sequential monitoring of copper ions and pyrophosphate (PPi) with a single sensor based on a DNAzyme-Fe₃O₄ system and glucometer readout was performed. Initially, streptavidin was functionalized on the surface of magnetic Fe₃O₄ spheres through glutaraldehyde. Then, an invertase-modified DNA Cu substrate was connected to the magnetic Fe₃O₄ spheres by a specific reaction between streptavidin and biotin. The sensing system was formed by a hybridization reaction between the Cu substrate and Cu enzyme. In the presence of Cu²⁺, Cu²⁺ will recognize the Cu DNA substrate and form an “off-on” signal switch, thereby resulting in the separation of invertase from the Fe₃O₄ nanospheres. PPi recognizes Cu²⁺ to form a Cu²⁺-PPi complex, resulting in an “on-off” signal switch. Under optimized conditions, linear detection ranges for Cu²⁺ and PPi of 0.01–5 and 0.5–10 μM, and detection limits for Cu²⁺ and PPi of 10 nM and 500 nM, respectively, were obtained. Good selectivity was achieved for the analysis of Cu²⁺ and PPi. Satisfactory results were achieved for this biosensor during the determination of Cu²⁺ in real tap samples and PPi in human urine samples. This verified that the sensor is portable and low cost, and can be applied to the sequential monitoring of multiple analytes with a single point-of-care biosensor.

Comparison of the accuracy of measuring blood glucose in whole blood of arteriovenous mixed blood by two kinds of blood glucose meters

BACKGROUND

Portable blood glucose meters are the main method for detecting the blood glucose status of clinical patients.

OBJECTIVE

To investigate the accuracy of detecting blood glucose in haemodialysis patients by sampling two blood glucose meters through the haemodialysis line.

METHODS

Convenient sampling was used to select 80 patients with maintenance haemodialysis. The patients were sampled through the arterial end of the haemodialysis line within three minutes of being put on the machine. One specimen was tested by glycemeter1, which can identify the type of blood in the arteries and veins, and glycemeter2, which can only detect blood glucose in the capillaries for bedside blood glucose testing. The other specimen was sent to the laboratory biochemical analyser for blood glucose testing.

RESULTS

When the blood glucose value of the first blood glucose meter (No. 1) was compared with the laboratory biochemical analyser, the correlation coefficient was r = 0.805 (p < 0.05), the out of value of the first blood glucose meter accounted for 4.4%, and the consistency reached 95% (p < 0.05). When the blood glucose value of the second blood glucose meter (No. 2) was compared with the laboratory biochemical analyser, the correlation coefficient was r = 0.800 (p < 0.05), the out of value of the second blood glucose meter accounted for 4.4%, and the consistency reached 95% (p < 0.05).

CONCLUSIONS

For patients with maintenance haemodialysis, the blood glucose values detected by the two bedside blood glucose meters using arteriovenous mixed blood in the pipeline do not affect the accuracy and can respond more realistically.

Advances and Challenges in Small-Molecule DNA Aptamer Isolation, Characterization, and Sensor Development

Aptamers are short oligonucleotides isolated in vitro from randomized libraries that can bind to specific molecules with high affinity, and offer a number of advantages relative to antibodies as biorecognition elements in biosensors. However, it remains difficult and labor-intensive to develop aptamer-based sensors for small-molecule detection. Here, we review the challenges and advances in the isolation and characterization of small-molecule-binding DNA aptamers and their use in sensors. First, we discuss in vitro methodologies for the isolation of aptamers, and provide guidance on selecting the appropriate strategy for generating aptamers with optimal binding properties for a given application. We next examine techniques for characterizing aptamer-target binding and structure. Afterwards, we discuss various small-molecule sensing platforms based on original or engineered aptamers, and their detection applications. Finally, we conclude with a general workflow to develop aptamer-based small-molecule sensors for real-world applications.

Hitting the diagnostic sweet spot: Point-of-care SARS-CoV-2 salivary antigen testing with an off-the-shelf glucometer

Significant barriers to the diagnosis of latent and acute SARS-CoV-2 infection continue to hamper population-based screening efforts required to contain the COVID-19 pandemic in the absence of widely available antiviral therapeutics or vaccines. We report an aptamer-based SARS-CoV-2 salivary antigen assay employing only low-cost reagents ($3.20/test) and an off-the-shelf glucometer. The test was engineered around a glucometer as it is quantitative, easy to use, and the most prevalent piece of diagnostic equipment globally, making the test highly scalable with an infrastructure that is already in place. Furthermore, many glucometers connect to smartphones, providing an opportunity to integrate with contact tracing apps, medical providers, and electronic health records. In clinical testing, the developed assay detected SARS-CoV-2 infection in patient saliva across a range of viral loads - as benchmarked by RT-qPCR - within 1 h, with 100% sensitivity (positive percent agreement) and distinguished infected specimens from off-target antigens in uninfected controls with 100% specificity (negative percent agreement). We propose that this approach provides an inexpensive, rapid, and accurate diagnostic for distributed screening of SARS-CoV-2 infection at scale.

Point-of-Care Monitoring of Colitis Using Intestinal Alkaline Phosphatase in Inflammatory Bowel Disease

Intestinal Alkaline Phosphatase (IAP) was investigated as a potential biomarker to monitor colitis in a mouse model of Inflammatory Bowel Disease (IBD). We developed a Point-Of-Care (POC) assay to detect IAP with a glucose meter in 15 min. We synthesized a paracetamol-bearing compound specifically cleaved by IAP to release paracetamol, which can be detected with a personal glucometer. Interleukin 10 deficient (IL 10-/-) mouse model samples were used to compare the IAP level in mice with mild or severe colitis. The results showed that fecal IAP level was significantly lower in each mouse sample with severe colitis than with mild colitis. Mice treated with anti-Tumor Necrosis Factor-alpha (anti-TNF-α) to decrease inflammation exhibited a much higher level of IAP than those without treatment (IAP levels from anti-TNF-α treated vs nontreated = 2.80 U vs 0.11 U, P < 0.0001). Taken together, IAP can be considered as a potential biomarker to monitor colitis, and a rapid, user-friendly POC glucometer-based assay can be potentially used to monitor colitis levels and inflammation flareups in IBD.

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.

Target-triggered aggregation of gold nanoparticles for photothermal quantitative detection of adenosine using a thermometer as readout

Colorimetric platform using the aggregation of gold nanoparticles (AuNPs) is a pretty simple method for biosensing, but advanced instruments such as specterophotometer is still needed to achieve accurately quantitative readout. Aggregated AuNPs exhibit excellent photothermal properties under near-infrared laser irradiation, which is significantly different from non-aggregated AuNPs. Herein, given the different photothermal effect, we translated the AuNPs-based colorimetric assay into a photothermal assay for the quantitative detection of adenosine using a thermometer as readout. Short single-stranded DNA (ssDNA, adenosine aptamer) was adsorbed on the surface of AuNPs and hence prevented the aggregation of AuNPs under high ionic concentration. The presence of adenosine caused the structural change of ssDNA and the AuNPs became aggregated. The enhanced temperature under NIR-laser irradiation has a linear response to the concentration of adenosine in the range of 2.0-50.0 μM. The detection limit was 1.7 μM. This proposed method is portable, easy and applicable to the quantitative assay of other targets by simply replacing of the sequence of ssDNA.