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

A dual-mode strategy based on β-galactosidase and target-induced DNA polymerase protection for transcription factor detection using colorimetry and a glucose meter

In this work, we report a novel dual-mode method for the highly specific and sensitive detection of transcription factors (TFs) via the integration of Klenow polymerase protection induced by target-specific recognition, cascade-signal amplification using the hybridization chain reaction (HCR) and CRISPR/Cas12a system, and dual-signal transduction mediated by β-galactosidase (β-gal) and two substrates. A dual-mode signal-sensing interface was constructed by immobilizing the oligo DNA probe (P1) tethered β-gal in a 96-well plate. A hairpin H1 with the ability to initiate HCRs was designed to contain the TF binding site. The binding between the TF and H1 protected the H1 from being extended by the Klenow fragment. After thermal denaturation, the reserved H1 launched the HCR and the HCR products activated CRISPR/Cas12a to cleave P1 and reduce the β-gal on the sensing interface, and thus the contents of the TFs and the corresponding signals mediated by the catalysis of β-gal showed a correlation. This work was the first attempt at utilizing β-gal for dual-signal transduction. It is a pioneering study to utilize the HCR-CRISPR/Cas12a system for dual-mode TF sensors. It revealed that DNA polymerase protection through the binding of TF and DNA could be applied as a new pattern to develop TF sensors.

Personal Glucose Meters Coupled with Signal Amplification Technologies for Quantitative Detection of Non-Glucose Targets: Recent Progress and Challenges in Food Safety Hazards Analysis

Ensuring food safety is paramount worldwide. Developing effective detection methods to ensure food safety can be challenging owing to trace hazards, long detection time, and resource-poor sites, in addition to the matrix effects of food. Personal glucose meter (PGM), a classic point-of-care testing device, possesses unique application advantages, demonstrating promise in food safety. Currently, many studies have used PGM-based biosensors and signal amplification technologies to achieve sensitive and specific detection of food hazards. Signal amplification technologies have the potential to greatly improve the analytical performance and integration of PGMs with biosensors, which is crucial for solving the challenges associated with the use of PGMs for food safety analysis. This review introduces the basic detection principle of a PGM-based sensing strategy, which consists of three key factors: target recognition, signal transduction, and signal output. Representative studies of existing PGM-based sensing strategies combined with various signal amplification technologies (nanomaterial-loaded multienzyme labeling, nucleic acid reaction, DNAzyme catalysis, responsive nanomaterial encapsulation, and others) in the field of food safety detection are reviewed. Future perspectives and potential opportunities and challenges associated with PGMs in the field of food safety are discussed. Despite the need for complex sample preparation and the lack of standardization in the field, using PGMs in combination with signal amplification technology shows promise as a rapid and cost-effective method for food safety hazard analysis.

CRISPR/Cas13a-assisted AMP generation for SARS-CoV-2 RNA detection using a personal glucose meter

Herein, we described a washing- and label-free clustered regularly interspaced short palindromic repeats (CRISPR)/LwaCas13a-based RNA detection method utilizing a personal glucose meter (PGM), which relies on the trans-cleavage activity of CRISPR/Cas13a and kinase reactions. In principle, the presence of target RNA activates the trans-cleavage of CRISPR/Cas13a, generating 2',3'-cyclic phosphate adenosine, which is converted to adenosine monophosphate (AMP) by the T4 polynucleotide kinase. Subsequently, the AMP is converted to adenosine diphosphate (ADP) through phosphorylation by a myokinase; ADP is then used as a substrate in the cascade enzymatic reaction promoted by pyruvate kinase and hexokinase. The overall reaction leads to the continuous conversion of glucose to glucose-6-phosphate, resulting in a reduction of glucose concentration proportional to the level of target RNA, which can therefore be indirectly measured with a PGM. By employing this novel strategy, severe acute respiratory syndrome coronavirus-2 RNA can be successfully detected with excellent specificity. In addition, we were able to overcome non-specific responses of CRISPR/Cas13a and distinguish single nucleotide polymorphisms by introducing a single-base mismatch in the complementary RNA. Our study provides an alternative coronavirus disease 2019 detection technology that is affordable, accessible, and portable with a fast turnaround time and excellent selectivity.

Washing-Free and Label-Free Onsite Assay for Inorganic Pyrophosphatase Activity Using a Personal Glucose Meter

In this study, we demonstrated a personal glucose meter-based method for washing-free and label-free inorganic pyrophosphatase (PPase) detection, which relies on the cascade enzymatic reaction (CER) promoted by hexokinase and pyruvate kinase. In principle, the absence of target PPase enables adenosine triphosphate sulfurylase to catalyze the conversion of pyrophosphate (PPi) to ATP, a substrate of CER, which results in the significant reduction of glucose levels by the effective CER process. In contrast, the PPi cleavage activity works in the presence of target PPase by decomposing PPi to orthophosphate (Pi). Therefore, the CER process cannot be effectively executed, leading to the maintenance of the initial high glucose level that may be measured by a portable personal glucose meter. Based on this novel strategy, a quantitative evaluation of the PPase activity may be achieved in a dynamic linear range of 1.5-25 mU/mL with a detection limit of 1.18 mU/mL. Compared with the previous PPase detection methods, this method eliminates the demand for expensive and bulky analysis equipment as well as a complex washing step. More importantly, the diagnostic capability of this method was also successfully verified by reliably detecting PPase present in an undiluted human serum sample with an excellent recovery ratio of 100 ± 2%.