Taking glucose as intermediate bridge-signal-molecule for on-site and convenient detection of ochratoxin A in rice with portable glucose meter.

On-site screening of biotoxins is of great importance for food safety. A new electrochemical-biosensing strategy was constructed for ochratoxin A (OTA) detection by direct using ready-made commercial portable-glucose-meter (PGM). Aptamer against OTA was adopted as the recognition probe and pre-immobilized onto the sensing interface. The complementary biotin-modified probe was further decorated by hybridization. Biotinylated invertase was further introduced onto the sensing system with streptavidin, which also acted as the signal amplification unit. The invertase, which was depended on the amount of OTA, produced the glucose from sucrose in the sensing solution. The glucose could be directly and conveniently measured with PGM. Quantitative analysis of OTA was achieved with a linear range from 0.5 ng/mL to 10 ng/mL and detection limit of 0.45 ng/mL. Of significance, it has been successfully applied for OTA analysis in rice with satisfied recoveries. This unique PGM-based electrochemical platform reveals prospective potential in food safety monitoring.

Personal Glucose Meter for α-Glucosidase Inhibitor Screening Based on the Hydrolysis of Maltose.

As a key enzyme regulating postprandial blood glucose, α-Glucosidase is considered to be an effective target for the treatment of diabetes mellitus. In this study, a simple, rapid, and effective method for enzyme inhibitors screening assay was established based on α-glucosidase catalyzes reactions in a personal glucose meter (PGM). α-glucosidase catalyzes the hydrolysis of maltose to produce glucose, which triggers the reduction of ferricyanide (K3[Fe(CN)6]) to ferrocyanide (K4[Fe(CN)6]) and generates the PGM detectable signals. When the α-glucosidase inhibitor (such as acarbose) is added, the yield of glucose and the readout of PGM decreased accordingly. This method can achieve the direct determination of α-glucosidase activity by the PGM as simple as the blood glucose tests. Under the optimal experimental conditions, the developed method was applied to evaluate the inhibitory activity of thirty-four small-molecule compounds and eighteen medicinal plants extracts on α-glucosidase. The results exhibit that lithospermic acid (52.5 ± 3.0%) and protocatechualdehyde (36.8 ± 2.8%) have higher inhibitory activity than that of positive control acarbose (31.5 ± 2.5%) at the same final concentration of 5.0 mM. Besides, the lemon extract has a good inhibitory effect on α-glucosidase with a percentage of inhibition of 43.3 ± 3.5%. Finally, the binding sites and modes of four active small-molecule compounds to α-glucosidase were investigated by molecular docking analysis. These results indicate that the PGM method is feasible to screening inhibitors from natural products with simple and rapid operations.

Detection of p53 DNA using commercially available personal glucose meters based on rolling circle amplification coupled with nicking enzyme signal amplification.

The development of cost-effective methods for early detection and identification of prognostic markers still remains a significant challenge to improve diagnosis and reduce the mortality of cancer. Herein, on the basis of rolling circle amplification (RCA) coupled with nicking endonuclease-assisted signal amplification (NESA), a simple, sensitive and portable biosensor was developed for the determination of p53 DNA by using the personal glucose meter (PGM) as readout. Initially, biotin-modified hairpin probe (HP) was immobilized onto streptavidin-coated magnetic beads (MBs). The target DNA hybridized with the loop region of the HP, which triggered target recycling process and produced the complementary sequences for the padlock probes. Next, the liberated complementary sequences hybridized with the padlock probes to form a circular template, inducing the subsequent RCA reaction and replicating a long tandem repeated sequences. Then, numerous DNA-invertase conjugation were tagged on the resulted RCA products on the surface of MBs. The DNA-invertase efficiently catalyzed the hydrolysis of sucrose to generate abundant glucose, leading to an amplified response of glucometer. By virtue of the multiple signal amplification strategy, the proposed biosensor toward p53 DNA could achieve a low detection limit of 0.36 pM with a linear calibration range from 0.5 to 10 pM and exhibited excellent sequence selectivity. In addition, the resulting biosensor was also applied to detect the p53 DNA sequence in spiked human serum samples with satisfactory results, which possessed enormous potential to be applied in clinical diagnostics and biomedical research.