No abstract

Cadmium (Cd2+) is one of the most toxic heavy metals causing serious health problems; thus, designing accurate analytical methods for monitoring such pollutants is highly urgent. Herein, we report a label-free electrochemical aptasensor for cadmium detection in water. For this, a nanocomposite combining the advantages of gold nanoparticles (AuNPs), carbon nanotubes (CNTs) and chitosan (Cs) was constructed and used as immobilization support for the cadmium aptamer. First, the surface of a glassy carbon electrode (GCE) was modified with CNTs-CS. Then, AuNPs were deposited on CNTs-CS/GCE using chrono-amperometry. Finally, the immobilization of the amino-modified Cd-aptamer was achieved via glutaraldehyde cross-linking. The different synthesis steps of the AuNPs/CNTs/CS nano assembly were characterized by cyclic voltammetry (CV). Electrochemical impedance spectroscopy (EIS) was employed for cadmium determination. The proposed biosensor exhibited excellent performances for cadmium detection at a low applied potential (−0.5 V) with a high sensitivity (1.2 KΩ·M−1), a detection limit of 0.02 pM and a wide linear range (10−13–10−4 M). Moreover, the aptasensor showed a good selectivity against the interfering ions: Pb2+; Hg2+ and Zn2+. Our electrochemical biosensor provides a simple and sensitive approach for Cd2+ detection in aqueous solutions, with promising applications in the monitoring of trace amounts of heavy metals in real samples.

Monitoring of circulating N-terminal proBNP (NT-proBNP) biomarkers is crucial for the diagnosis of people suffering from heart failure (HF). In this work, we describe a novel ultrasensitive NT-proBNP immunosensor for NT-proBNP detection in artificial human saliva. The surface of the developed immunosensor based on gold working microelectrodes (WEs) was biofunctionalized through carboxyl diazonium to immobilize anti-NT-proBNP antibodies. The chemical surface modification of WEs was carried out by cyclic voltammetery CV whilst the quantification of NT-proBNP biomarkers was made by electrochemical impedance spectroscopy (EIS). The immunosensor has demonstrated a linear detection response within the range 1-20 pg/mL for NTproBNP detection in artificial human saliva with a good selectivity in the presence of other interferences.

An aptasensing platform was employed for Hb determination. The catalytic activity of the bound Hb was explored by measuring H2O2 and nitrite. The developed platform was highly sensitive and selective.

In this study, a novel, sensitive electrochemical enzyme‐based biosensor for urea detection was presented. This biosensor combines a three‐electrode system consisting of a classic Glassy Carbon Electrode (GCE) as the working electrode, a platinum counter electrode, and Ag/AgCl as the reference electrode. To construct this urea platform, a GCE was modified with a polyaniline (PANi) film. Then, bacterial urease from Proteus mirabilis was immobilized on the modified GCE (Pm‐Urease‐PANi‐GCE). For the characterization of surface modification, Cyclic Voltammetry (CV) and Scanning Electron Microscope (SEM) were applied, while the Square Wave Voltammetry (SWV) technique was performed for urea detection. The main analytical characteristics of the Pm‐Urease‐PANi‐GCE biosensor showed a good linear range from 0.1 to 10 mM of urea, a limit of detection (LOD) of 0.1 mM, a Michaelis‐Menten Km of 0.23 mM, and a sensitivity value 46 μA/mM/cm2. This biosensor allows the detection of urea in solutions, and it could be improved for further medical, environmental, or engineering applications.