Synthesis, Characterization, and Electrochemical Evaluation of Copper Sulfide Nanoparticles and Their Application for Non-Enzymatic Glucose Detection in Blood Samples.

Glutathione-capped copper sulfide (CuxSy) nanoparticles with two different average sizes were successfully achieved by using a simple reduction process that involves only changing the reaction temperature. Temperature-induced changes in the size of CuxSy nanoparticles resulted in particles with different optical, morphological, and electrochemical properties. The dependence of electrochemical sensing properties on the sizes of CuxSy nanoparticles was studied by using voltammetric and amperometric techniques. The spherical CuxSy nanoparticles with the average particle size of 25 ± 0.6 nm were found to be highly conductive as compared to CuxSy nanoparticles with the average particle size of 4.5 ± 0.2 nm. The spherical CuxSy nanoparticles exhibited a low bandgap energy (Eg) of 1.87 eV, resulting in superior electrochemical properties and improved electron transfer during glucose detection. The sensor showed a very good electrocatalytic activity toward glucose molecules in the presence of interference species such as uric acid (UA), ascorbic acid (AA), fructose, sodium chloride, and sucrose. These species are often present in low concentrations in the blood. The sensor demonstrated an excellent dynamic linear range between 0.2 to 16 mM, detection limit of 0.2 mM, and sensitivity of 0.013 mA/mM. The applicability of the developed sensor for real field determination of glucose was demonstrated by use of spiked blood samples, which confirmed that the developed sensor had great potential for real analysis of blood glucose levels.

Development of a Versatile Half-Strip Lateral Flow Assay toward the Detection of Rift Valley Fever Virus Antibodies.

Rift Valley fever (RVF) is a mosquito-borne zoonotic disease that is caused by the Rift Valley fever virus (RVFV); Bunyaviridae: Phlebovirus. RVF disease can affect several different species, including ruminants, camels and humans and thus present a dual threat to public health and livestock food production in endemic regions. In livestock, the RVFV infection is characterised by an acute hepatitis, abortion and high mortality rates in new-born animals. The current RVF diagnostic techniques have shown good sensitivity. However, they require extensive sample processing and complex instrumentation. Owing to speed, low cost, ease of use, and most importantly, the ability to diagnose diseases at sites where they are managed, lateral flow immunoassays (LFIA) are the most widely used point-of-care (POC) tools for disease diagnosis. In this study, a lateral flow assay (LFA) device that is able to detect antibodies against RVFV, with a minimum detectable concentration of 0.125 mg/mL, was successfully developed. The LFA also successfully detected RVFV antibodies in reference RVFV sera. Protein A (ProA), which has the ability to bind immunoglobulins from different species, was used in the detection probe, giving the developed RVFV LFA potential for multi-species diagnosis.

Gold nanoparticle based Tuberculosis immunochromatographic assay: the quantitative ESE Quanti analysis of the intensity of test and control lines.

A rapid dual channel lateral flow assay for the detection of Mycobacterium Tuberculosis antibodies (MTB 38 kDa monoclonal antibody) in human blood was developed. The MTB 6-14-38 kDa fusion antigen and anti-Protein A were used as the capture proteins for test and control lines respectively. Protein A labeled 40 nm gold nanoparticles were used as the detection conjugate. Whole blood and serum were spiked with MTB 38 kDa monoclonal antibody to make a positive sample model. The developed lateral flow was used to test MTB 38 kDa monoclonal antibody, and a detection limit of 5 ng/ml was used as a cut-off concentration of the analytes. The effect of the analyte concentration on the MTB lateral flow assay was studied using the variation of the intensity obtained from a ESE Quanti reader. There was a direct correlation between the analyte (MTB 38 kDa monoclonal antibody) concentration and the intensity of the test line. The intensity increased with an increase in the concentration of MTB 38 kDa monoclonal antibody, while in contrast, an increase in analyte concentration decreased the intensity of the control line.

Electrochemical impedimetric immunosensor for the detection of measles-specific IgG antibodies after measles infections.

The detection of measles-specific primary antibodies (IgG) using electrochemical impedimetric immunosensors is reported. The optimum conditions for electrode saturation were reached after 40 min for 1 µg ml(-1) antibody concentrations. Surface roughness using AFM increased with each immobilization or antigen-antibody reaction step clearly confirming the surface modification and recognition between antigen and antibody. The human serum (HS) and new-born calf serum (NCS) spiked with antigen-specific antibody were studied to mimic the real sample analysis. The HS and NCS sera containing antibodies due to measles exhibited correlation between the increasing antibody serum concentrations and the charge-transfer resistance (electrochemically measured). This work clearly showed the potential use of impedance as the preferred electrochemical method for detecting measles-antibodies in label-free manner.