Integration of Glutamate Dehydrogenase and Nanoporous Gold for Electrochemical Detection of Glutamate.

Glutamate, a non-essential amino acid produced by fermentation, plays a significant role in disease diagnosis and food safety. It is important to enable the real-time monitoring of glutamate concentration for human health and nutrition. Due to the challenges in directly performing electrochemical oxidation-reduction reactions of glutamate, this study leverages the synergistic effect of glutamate dehydrogenase (GLDH) and nanoporous gold (NPG) to achieve the indirect and accurate detection of glutamate within the range of 50 to 700 µM by measuring the generated quantity of NADH during the enzymatic reaction. The proposed biosensor demonstrates remarkable performance characteristics, including a detection sensitivity of 1.95 µA mM-1 and a limit of detection (LOD) of 6.82 µM. The anti-interference tests indicate an average recognition error ranging from -3.85% to +2.60%, spiked sample recovery rates between 95% and 105%, and a relative standard deviation (RSD) of less than 4.97% for three replicate experiments. Therefore, the GLDH-NPG/GCE biosensor presented in this work exhibits excellent accuracy and repeatability, providing a novel alternative for rapid glutamate detection. This research contributes significantly to enhancing the precise monitoring of glutamate concentration, thereby offering more effective guidance and control for human health and nutrition.

Sensitivity Detection of Uric Acid and Creatinine in Human Urine Based on Nanoporous Gold.

Given the significance of uric acid and creatinine in clinical diagnostic, disease prevention and treatment, a multifunctional electrochemical sensor was proposed for sensitive detection of uric acid and creatinine. The sensitive detection of uric acid was realized based on the unique electrochemical oxidation of nanoporous gold (NPG) towards uric acid, showing good linearity from 10 µM to 750 µM with a satisfactory sensitivity of 222.91 µA mM-1 cm-2 and a limit of detection (LOD) of 0.06 µM. Based on the Jaffé reaction between creatinine and picric acid, the sensitive detection of creatinine was indirectly achieved in a range from 10 to 2000 µM by determining the consumption of picric acid in the Jaffé reaction with a detection sensitivity of 195.05 µA mM-1 cm-2 and a LOD of 10 µM. For human urine detection using the proposed electrochemical sensor, the uric acid detection results were comparable to that of high-performance liquid chromatography (HPLC), with a deviation rate of less than 10.28% and the recoveries of uric acid spiked in urine samples were 89~118%. Compared with HPLC results, the deviation rate of creatinine detection in urine samples was less than 4.17% and the recoveries of creatinine spiked in urine samples ranged from 92.50% to 117.40%. The multifunctional electrochemical sensor exhibited many advantages in practical applications, including short detection time, high stability, simple operation, strong anti-interference ability, cost-effectiveness, and easy fabrication, which provided a promising alternative for urine analysis in clinical diagnosis.

A rapid anti-Helicobacter pylori biofilm drug screening biosensor based on AlpB outer membrane protein and colloidal gold/nanoporous gold framework.

Inhibition or disruption of biofilms has been recognized as an important means to eradicate Helicobacter pylori (H. pylori) infection. However, a fast and efficient drug screening method against H. pylori biofilms has not yet been established. Therefore, AlpB, an important outer membrane protein in H. pylori biofilm formation, was selected as a biological recognition element to screen anti-biofilm drugs in this study. A novel AlpB/colloidal gold (CG)/nanoporous gold (NPG)/Nafion-reduced graphene oxide (rGO)/glassy carbon electrode (GCE) biosensor was constructed based on the heterologous expression of AlpB. The prepared AlpB-based biosensor not only successfully identified six anti-biofilm drugs, but also evaluated the sensitivity and action intensity of different anti-biofilm drugs binding to AlpB by interaction kinetics analysis. The sensitivity order of AlpB to the six anti-biofilm drugs was: allicin > erythromycin > SCC > curcumin > rifampicin > NAC and the action intensity of the six anti-biofilm drugs on AlpB was: rifampicin > NAC > allicin > erythromycin > SCC > curcumin. In addition, molecular docking results showed that the six anti-biofilm drugs might exert their anti-biofilm effects by spontaneously binding to the conserved region of AlpB protein. This study provided a rapid screening platform and a unified data processing method for potential anti-biofilm drug development.

The development of NAD+-dependent dehydrogenase screen-printed biosensor based on enzyme and nanoporous gold co-catalytic strategy.

Given the significance of dihydronicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotide (NAD+) in numerous biochemical fields such as clinical diagnostics and fermentation monitoring, a synergistic strategy was proposed based on the co-catalysis of NAD+-dependent dehydrogenases and nanoporous gold (NPG) towards the oxidation of substrates and NADH, respectively. An NAD+-dependent dehydrogenase/NPG/SPE biosensing platform was developed by modifying screen-printed electrode (SPE) with NPG and NAD+-dependent dehydrogenase for the electrochemical detections of NADH, ethanol, and glucose. Owing to the exceptional oxidation activity of NPG towards NADH, the amperometric detection of NADH exhibited good linearity from 50 µM to 2.0 mM with a low detection limit (LOD) of 15.18-16.39 µM and a satisfactory sensitivity of 1.58-1.72 µA mM-1 within a wide pH range. With alcohol dehydrogenase (ADH) and glucose dehydrogenase (GDH) as model enzymes, ADH/NPG/SPE and GDH/NPG/SPE exhibited excellent analytic characteristics (sensitivity of 0.66 µA mM-1 and 2.04 µA mM-1, LOD of 40.72 µM and 14.83 µM) of ethanol and glucose detection in buffer solution as well as in human serum and fermentation broth. The sensitive micro-sample detections of ethanol and glucose in both real samples were achieved using the proposed biosensors with comparable accuracy (deviation rates of 0.85-7.92%) as automatic analyzers. The proposed biosensing platform elicited many advantageous properties in practical applications, including micro-sample analysis, cost-efficient, easy fabrication, and flexible adaptability, which made it a promising candidate for the clinical blood test, urinalysis, and fermentation monitoring.

Sensitive electrochemical detection of cholesterol using a portable paper sensor based on the synergistic effect of cholesterol oxidase and nanoporous gold.

As a crucial biomarker for some diseases, the determination of cholesterol in human serum is of great significance for the diagnosis and prevention of these diseases. Hence, a portable cholesterol detection method is necessary for clinical and domestic applications. Here, a portable paper sensor was designed for cholesterol detection by modifying screen-printed electrode (SPE) with nanoporous gold (NPG). To achieve the reliable cholesterol detection, a synergistic strategy was proposed based on the oxidation of cholesterol by cholesterol oxidase (ChOx) and the reduction of oxidation product (H2O2) by NPG. Compared to existing electrochemical sensors, the resulting paper sensor exhibited a wider linear response in a range from 50 µM to 6 mM as well as a higher sensitivity of 32.68 µA mM-1 cm-2 with a lower detection limit of 8.36 µM. Moreover, the portable paper sensor presented strong anti-interference capability and stability in the detection of cholesterol in human serum, and the data detected by the portable paper sensor were consistent with that obtained by an automatic biochemical analyzer. These unique performances confirmed that the proposed paper sensor was a sensitive, reliable, and portable cholesterol detection method, making it a good choice for cholesterol detection.