Highly sensitive AlGaN/GaN HEMT biosensors using an ethanolamine modification strategy for bioassay applications

In this paper, we propose a highly efficient surface modification strategy on an AlGaN/GaN high electron mobility transistor (HEMT), where ethanolamine (EA) was utilized to functionalize the surface of GaN and provided amphoteric amine groups for probe molecular immobilization for bioassay application. The molecular gated-AlGaN/GaN HEMT was utilized for pH and prostate-specific antigen (PSA) detection to verify its performance as a biosensor. Benefitting from the high coating quality on the GaN surface, the performance of our biosensor is drastically improved compared to other AlGaN/GaN HEMT based pH and PSA biosensors reported before. Our molecular gated-AlGaN/GaN HEMT biosensor has achieved good static electrical performance for pH sensing, such as high sensitivity, good linearity and chemical stability. Moreover, after further immobilization of PSA antibody onto the EA aminated GaN surface, the limit of detection (LOD) for PSA detection is as low as 1 fg mL⁻¹ in PBS buffer, which has reached an at least two orders of magnitude decrease compared to any other AlGaN/GaN HEMT based PSA biosensor reported before. And the sensitivity of our PSA biosensor has achieved a substantial increase, reaching up to 2.04% for 100 ng mL⁻¹. The measurements of pH and PSA utilizing the EA modified AlGaN/GaN HEMT biosensor indicate that the surface modification strategy on the GaN proposed in this paper can effectively improve the performance of the AlGaN/GaN HEMT based biosensor, which demonstrates a promising application prospect in the AlGaN/GaN HEMT based biological detection field.

We propose a highly efficient surface modification strategy on an AlGaN/GaN high electron mobility transistor, where ethanolamine was utilized to functionalize the surface of GaN and provided amphoteric amine groups for bioassay application.

Fast Detection of Bismerthiazol in Cabbage Based on Fluorescence Quenching of Protein-Capping Gold Nanoclusters

In this work, bismerthiazol was firstly assayed by a fast and portable method employing protein-capping gold nanoculsters as probes. The luminescent intensity of the nanoclusters showed a correlative response towards bismerthiazol from 5 to 4000 μg/mL with a linear relation in the range of 5 - 100 μg/mL. As little as 5 μg/mL of bismerthiazol could be quantified. The high affinity of bismerthiazol to interact with the soybean protein-capped gold nanoclusters contributed to the excellent selectivity of this method over other common pesticides. The recoveries in several cabbage samples were 101 - 135%, indicating good performance in practical applications. By comparison to previous reported approaches, this method bears advantages including simple operation, fast response, visual readout and good selectivity.

Paper-Based Electrochemical Detection of Chlorate

We describe the use of a paper-based probe impregnated with a vanadium-containing polyoxometalate anion, [PMo₁₁VO₄₀]⁵⁻, on screen-printed carbon electrodes for the electrochemical determination of chlorate. Cyclic voltammetry (CV) and chronocoulometry were used to characterize the ClO₃⁻ response in a pH = 2.5 solution of 100 mM sodium acetate. A linear CV current response was observed between 0.156 and 1.25 mg/mL with a detection limit of 0.083 mg/mL (S/N > 3). This performance was reproducible using [PMo₁₁VO₄₀]⁵⁻-impregnated filter paper stored under ambient conditions for as long as 8 months prior to use. At high concentration of chlorate, an additional catalytic cathodic peak was seen in the reverse scan of the CVs, which was digitally simulated using a simple model. For chronocoulometry, the charge measured after 5 min gave a linear response from 0.625 to 2.5 mg/mL with a detection limit of 0.31 mg/mL (S/N > 3). In addition, the slope of charge vs. time also gave a linear response. In this case the linear range was from 0.312 to 2.5 mg/mL with a detection limit of 0.15 mg/mL (S/N > 3). Simple assays were conducted using three types of soil, and recovery measurements reported.

Highly sensitive extended gate-AlGaN/GaN high electron mobility transistor for bioassay applications

An extended gate-AlGaN/GaN high electron mobility transistor (EG-AlGaN/GaN HEMT) with a high sensitivity for bioassay has been developed.