A Simple and Universal Nucleic Acid Assay Platform Based on Personal Glucose Meter Using SARS-CoV-2 N Gene as the Model

A portable and efficient strategy for ofloxacin detection using Ce-based MOF-loaded glucose oxidase and a personal glucose meter

Antibiotic residues in food and the environment pose significant risks to public health and safety, necessitating the development of rapid, portable, and efficient detection methods. Ofloxacin (OFL), a widely used antibiotic, is of particular concern due to its potential for contamination in milk and surface water. Current detection methods often require expensive instrumentation and complex procedures, limiting their applicability for on-site testing. This work addresses the critical need for a cost-effective, portable approach to reliably detect OFL residues. We developed a novel personal glucose meter (PGM)-based aptasensor utilizing a porous spherical cerium-based metal-organic framework (Ce-MOF) as a loading platform for glucose oxidase (GOx) and oligonucleotide sequences (Ce-MOF-GOx-cDNA). The hybrid probe, formed by conjugating Ce-MOF-GOx-cDNA with aptamer-modified magnetic beads, enabled specific recognition of OFL through nucleobase pairing. The sensor exhibited a detection range of 50 pg/mL to 500 ng/mL with a detection limit of 40 pg/mL under optimal conditions. The process showed excellent selectivity, stability, and reproducibility. Real-sample testing in spiked milk and surface water demonstrated recovery rates of 99.5% - 108%, with relative standard deviations of less than 4.7%. This study presents a portable and efficient strategy for detecting OFL residues using a PGM-based aptasensor. The method combines simplicity, rapid detection, and high sensitivity, offering significant potential for on-site applications in food and environmental safety monitoring.

The Personal Glucose Meter as the Measurement Principle in Point-of-Care Applications

A personal glucose meter (PGM) is a medical device that measures blood glucose levels and can be found worldwide. Owing to their sensitivity, simplicity, portability, and low cost, PGMs stand as one of the most frequently utilized analytical methods. This work reviews the different applied methodologies for detecting analytes other than glucose employing a PGM and how it can be incorporated for point-of-care diagnosis needs. To visualize the variants, first, a classification is made according to the biorecognition elements used (aptamers, antibodies, etc.), and where the determination of different analytes is done through the glucose signal using different glucose-generating enzymes such as invertase or glucosidase. Transduction can also be based on the use of nanocarriers that generally encapsulate glucose, although it is also possible to find a combination of the two aforementioned strategies. The PGM can also be used for the direct detection of interfering substances of the biosensor, such as NADH or paracetamol. Lastly, we discuss how a PGM might have been implemented to detect COVID-19 and how it could be used on a massive scale for the point-of-care diagnosis of a pandemic.

Recent Developments in Personal Glucose Meters as Point-of-Care Testing Devices (2020-2024)

Point-of-care testing (POCT) is a contemporary diagnostic approach characterized by its user-friendly nature, cost efficiency, environmental compatibility, and lack of reliance on professional experts. Therefore, it is widely used in clinical diagnosis and other analytical testing fields to meet the demand for rapid and convenient testing. The application of POCT technology not only improves testing efficiency, but also brings convenience and benefits to the healthcare industry. The personal glucose meter (PGM) is a highly successful commercial POCT tool that has been widely used not only for glucose analysis, but also for non-glucose target detection. In this review, the recent advances from 2020 to 2024 in non-glucose target analysis for PGMs as POCT devices are summarized. The signal transduction strategies for non-glucose target analysis based on PGMs, including enzymatic transduction, nanocarrier transduction (enzyme or glucose), and glucose consumption transduction are briefly introduced. Meanwhile, the applications of PGMs in non-glucose target analysis are outlined, encompassing biomedical, environmental, and food analysis, along with other diverse applications. Finally, the prospects of and obstacles to employing PGMs as POCT tools for non-glucose target analysis are discussed.

Cascaded nanozyme-based high-throughput microfluidic device integrating with glucometer and smartphone for point-of-care pheochromocytoma diagnosis

The development of point-of-care (POC) diagnostics devices for circulating tumor cells (CTCs) detection plays an important role in the early diagnosis of pheochromocytoma (PCC), especially in a low-resource setting. To further realize the rapid, portable, and high-throughput detection of CTCs, an Au@CuMOF cascade enzyme-based microfluidic device for instant point-of-care detection of CTCs was constructed by combining a smartphone application and a commercial portable glucose meter (PGM). In this microfluidic system, DOTA and norepinephrine (NE) modified Au@CuMOF signal probes and Fe3O4@SiO2 capture probes were used for the dual recognition and capture of rare PCC-CTCs. Then, the targeted binding of the Au@CuMOF cascade nanozymes to the CTCs endowed the cellular complexes with multienzyme mimetic activities (i.e., glucose oxidase-like and peroxidase-like activity) to catalyze glucose reduction as signal output for colorimetric and personal glucose meter (PGM) dual-mode detection of CTCs. The developed method has a linear range of 4 to 105 cells mL-1 and a detection limit of 3 cells mL-1. This method allows the simultaneous detection of six samples and demonstrates good applicability for CTCs detection in whole blood samples. More importantly, the combination of PGM, smartphone app and array microfluidic chips enables the rapid, portable, and high-throughput diagnoses of PCC, and providing provide a convenient and reliable alternative to traditional liquid biopsy diagnosis of various cancers.

Bovine Serum Albumin-Protected Gold Nanoclusters for Sensing of SARS-CoV-2 Antibodies and Virus

An approach to assess severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (and past infection) was developed. For virus detection, the SARS-CoV-2 virus nucleocapsid protein (NP) was targeted. To detect the NP, antibodies were immobilized on magnetic beads to capture the NPs, which were subsequently detected using rabbit anti-SARS-CoV-2 nucleocapsid antibodies and alkaline phosphatase (AP)-conjugated anti-rabbit antibodies. A similar approach was used to assess SARS-CoV-2-neutralizing antibody levels by capturing spike receptor-binding domain (RBD)-specific antibodies utilizing RBD protein-modified magnetic beads and detecting them using AP-conjugated anti-human IgG antibodies. The sensing mechanism for both assays is based on cysteamine etching-induced fluorescence quenching of bovine serum albumin-protected gold nanoclusters where cysteamine is generated in proportion to the amount of either SARS-CoV-2 virus or anti-SARS-CoV-2 receptor-binding domain-specific immunoglobulin antibodies (anti-RBD IgG antibodies). High sensitivity can be achieved in 5 h 15 min for the anti-RBD IgG antibody detection and 6 h 15 min for virus detection, although the assay can be run in "rapid" mode, which takes 1 h 45 min for the anti-RBD IgG antibody detection and 3 h 15 min for the virus. By spiking the anti-RBD IgG antibodies and virus in serum and saliva, we demonstrate that the assay can detect the anti-RBD IgG antibodies with a limit of detection (LOD) of 4.0 and 2.0 ng/mL in serum and saliva, respectively. For the virus, we can achieve an LOD of 8.5 × 10⁵ RNA copies/mL and 8.8 × 10⁵ RNA copies/mL in serum and saliva, respectively. Interestingly, this assay can be easily modified to detect myriad analytes of interest.

Utilization of a Glucometer Test Strip and Enzymatic Reactions to Quantify Anti-SARS-CoV-2 Spike RBD IgG Antibody and SARS-CoV-2 Virus in Saliva and Serum

A sensor capable of quantifying both anti-SARS-CoV-2 spike receptor-binding domain (RBD) antibody levels and the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus in saliva and serum was developed. This was accomplished by exploiting the enzymatic reaction of maltose and orthophosphate (PO43-) in the presence of maltose phosphorylase to generate an equivalent amount of glucose that was detected using a commercial glucometer test strip and a potentiostat. Important for this approach is the ability to generate PO43- in an amount that is directly related to the concentration of the analytes. RBD-modified magnetic microparticles were used to capture anti-SARS-CoV-2 spike RBD antibodies, while particles modified with anti-SARS-CoV-2 nucleocapsid antibodies were used to capture SARS-CoV-2 nucleocapsid protein from inactivated virus samples. A magnet was used to isolate and purify the magnetic microparticles (with analyte attached), and alkaline phosphatase-conjugated secondary antibodies were bound to the analytes attached to the respective magnetic microparticles. Finally, through enzymatic reactions, specific amounts of PO43- (and subsequently glucose) were generated in proportion to the analyte concentration, which was then quantified using a commercial glucometer test strip. Utilizing glucose test strips makes the sensor relatively inexpensive, with a cost per test of ∼US $7 and ∼US $12 for quantifying anti-SARS-CoV-2 spike RBD antibody and SARS-CoV-2, respectively. Our sensor exhibited a limit of detection of 0.42 ng/mL for anti-SARS-CoV-2 spike RBD antibody, which is sensitive enough to quantify typical concentrations of antibodies in COVID-19-infected or vaccinated individuals (>1 μg/mL). The limit of detection for the SARS-CoV-2 virus is 300 pfu/mL (5.4 × 106 RNA copies/mL), which exceeds the performance recommended by the WHO (500 pfu/mL). In addition, the sensor exhibited good selectivity when challenged with competing analytes and could be used to quantify analytes in saliva and serum matrices with an accuracy of >94% compared to RT-qPCR.