A simple electrochemical immunosensor based on a gold nanoparticle monolayer electrode for neutrophil gelatinase-associated lipocalin detection

Disposable label-free electrochemical immunosensor based on gold nanoparticles-Prussian blue for neutrophil gelatinase-associated lipocalin detection in urine samples

Neutrophil gelatinase-associated lipocalin (NGAL) is a remarkable biomarker for assessing acute kidney injury. In this study, we developed a novel label-free NGAL electrochemical immunosensor based on gold nanoparticles (AuNPs) and Prussian blue (PB) without an external mediator. The AuNPs-PB based immunosensor was fabricated on a custom gold-electrode (AuE)-based polypropylene (PP) substrate. We systematically assessed and optimized key experimental parameters, including the process of AuNPs-PB electrodeposition, antibody concentration, and incubation time. The immunosensor response toward NGAL was determined using differential pulse voltammetry, where the decrease in the oxidation current response of the PB redox probe correlating with the increase in NGAL concentration. Our results demonstrated that the synergistic benefits of both AuNPs and PB significantly improved electrochemical activity for NGAL detection and provided a highly stable sensor across a range of pH values. The label-free immunosensor exhibited two linear ranges: 0.10-1.40 ng mL-1 and 1.40-25.0 ng mL-1, with a low detection limit of 0.094 ng mL-1. The developed NGAL immunosensor displayed high selectivity and excellent reproducibility. Furthermore, NGAL detection was completed within 30 min and the immunosensor exhibited storage stability for six weeks. Notably, NGAL levels determined in human urine samples using this developed label-free immunosensor showed good agreement with the results obtained from the enzyme-linked immunosorbent assay. This novel label-free NGAL immunosensor provides great potential in developing NGAL point-of-care testing applications.

Gold nanowires-based sensor for quantification of H2O2 released by human airway epithelial cells

Hydrogen peroxide (H2O2) is a biomarker relevant for oxidative stress monitoring. Most chronic airway diseases are characterized by increased oxidative stress. To date, the main methods for the detection of this analyte are expensive and time-consuming laboratory techniques such as fluorometric and colorimetric assays. There is a growing interest in the development of electrochemical sensors for H2O2 detection due to their low cost, ease of use, sensitivity and rapid response. In this work, an electrochemical sensor based on gold nanowire arrays has been developed. Thanks to the catalytic activity of gold against hydrogen peroxide reduction and the high surface area of nanowires, this sensor allows the quantification of this analyte in a fast, efficient and selective way. The sensor was obtained by template electrodeposition and consists of gold nanowires about 5 μm high and with an average diameter of about 200 nm. The high active surface area of this electrode, about 7 times larger than a planar gold electrode, ensured a high sensitivity of the sensor (0.98 μA μM-1cm-2). The sensor allows the quantification of hydrogen peroxide in the range from 10 μM to 10 mM with a limit of detection of 3.2 μM. The sensor has excellent properties in terms of reproducibility, repeatability and selectivity. The sensor was validated by quantifying the hydrogen peroxide released by human airways A549 cells exposed or not to the pro-oxidant compound rotenone. The obtained results were validated by comparing them with those obtained by flow cytometry after staining the cells with the fluorescent superoxide-sensitive Mitosox Red probe giving a very good concordance.

Recent advances in gold electrode fabrication for low-resource setting biosensing

Gold electrodes are some of the most prevalent electrochemical biosensor substrate materials because they are readily functionalized with thiolated biomolecules. Yet, conventional methods to fabricate gold electrodes are costly and require onerous equipment, precluding them from implementation in low-resource settings (LRS). Recently, a number of alternative gold electrode fabrication methods have been developed to simplify and lower the cost of manufacturing. These methods include screen and inkjet printing as well as physical fabrication with common materials such as wire or gold leaf. All electrodes generated with these methods have successfully been functionalized with thiolated molecules, demonstrating their suitability for use in biosensors. Here, we detail recent advances in the fabrication, characterization and functionalization of these next-generation gold electrodes, with an emphasis on comparisons between cost and complexity with traditional cleanroom fabrication. We highlight gold leaf electrodes for their potential in LRS. This class of electrodes is anticipated to be broadly applicable beyond LRS due to their numerous inherent advantages.

Explore how immobilization strategies affected immunosensor performance by comparing four methods for antibody immobilization on electrode surfaces

Among the common methods used for antibody immobilization on electrode surfaces, which is the best available option for immunosensor fabrication? To answer this question, we first used graphene-chitosan-Au/Pt nanoparticle (G-Chi-Au/PtNP) nanocomposites to modify a gold electrode (GE). Second, avian reovirus monoclonal antibody (ARV/MAb) was immobilized on the GE surface by using four common methods, which included glutaraldehyde (Glu), 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide/N-hydroxysuccinimide (EDC/NHS), direct incubation or cysteamine hydrochloride (CH). Third, the electrodes were incubated with bovine serum albumin, four different avian reovirus (ARV) immunosensors were obtained. Last, the four ARV immunosensors were used to detect ARV. The results showed that the ARV immunosensors immobilized via Glu, EDC/NHS, direct incubation or CH showed detection limits of 10^0.63 EID₅₀ mL^-1, 10^0.48 EID₅₀ mL^-1, 10^0.37 EID₅₀ mL^-1 and 10^0.46 EID₅₀ mL^-1 ARV (S/N = 3) and quantification limits of 10^1.15 EID₅₀ mL^-1, and 10^1.00 EID₅₀ mL^-1, 10^0.89 EID₅₀ mL^-1 and 10^0.98 EID₅₀ mL^-1 ARV (S/N = 10), respectively, while the linear range of the immunosensor immobilized via CH (0-10^5.82 EID₅₀ mL^-1 ARV) was 10 times broader than that of the immunosensor immobilized via direct incubation (0-10^4.82 EID₅₀ mL^-1 ARV) and 100 times broader than those of the immunosensors immobilized via Glu (0-10^3.82 EID₅₀ mL^-1 ARV) or EDC/NHS (0-10^3.82 EID₅₀ mL^-1 ARV). And the four immunosensors showed excellent selectivity, reproducibility and stability.