Facile preparation of a highly sensitive non-enzymatic glucose sensor based on the composite of Cu(OH)2 nanotubes arrays and conductive polypyrrole

RGO decorated N-doped NiCo2O4 hollow microspheres onto activated carbon cloth for high-performance non-enzymatic electrochemical glucose detection

This paper reports the first effective fabrication of a high-performance non-enzymatic glucose sensor based on activated carbon cloth (ACC) coated with reduced graphene oxide (RGO) decorated N-doped urchin-like nickel cobaltite (NiCo₂O₄) hollow microspheres. Hierarchically mesoporous N-doped NiCo₂O₄ hollow microspheres were synthesized using a facile solvothermal method, followed by thermal treatment in a nitrogen (N₂) atmosphere. Subsequently, they were hydrothermally decorated with RGO nanoflakes. The resulting composite was dip-coated onto ACC, and its electrochemical and glucose sensing performances were investigated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and chronoamperometric measurements in a three-electrode system. The composite electrode sensor demonstrates admirable sensitivity (6122 μM mM^-1 cm^-2) with an ultralow detection limit (5 nM, S/N = 3), and it performs well within a substantial linear range (0.5-1.450 mM). Additionally, it exhibits good long-term response stability and outstanding anti-interference performance. These outstanding results can be attributed to the synergistic effects of the highly electrically conductive ACC with multiple channels, the enhanced catalytic activity of highly porous N-doped NiCo₂O₄ hollow microspheres, and the large electroactive sites provided by its well-developed hierarchical nanostructure and RGO nanoflakes. The findings highlight the enormous potential of the ACC/N-doped NiCo₂O₄@RGO electrode for non-enzymatic glucose sensing.

Progress on the influence of non-enzymatic electrodes characteristics on the response to glucose detection: a review (2016–2022)

Glucose sensing devices have experienced significant progress in the last years in response to the demand for cost-effective monitoring. Thus, research efforts have been focused on achieving reliable, selective, and sensitive sensors able to monitor the glucose level in different biofluids. The development of enzyme-based devices is challenged by poor stability, time-consuming, and complex purification procedures, facts that have given rise to the synthesis of enzyme-free sensors. Recent advances focus on the use of different components: metal-organic frameworks (MOFs), carbon nanomaterials, or metal oxides. Motivated by this topic, several reviews have been published addressing the sensor materials and synthesis methods, gathering relevant information for the development of new nanostructures. However, the abundant information has not concluded yet in commercial devices and is not useful from an engineering point of view. The dependence of the electrode response on its physico-chemical nature, which would determine the selection and optimization of the materials and synthesis method, remains an open question. Thus, this review aims to critically analyze from an engineering vision the existing information on non-enzymatic glucose electrodes; the analysis is performed linking the response in terms of sensitivity when interferences are present, stability, and response under physiological conditions to the electrode characteristics.

Label-free electrochemical aptasensor for rapid detection of SARS-CoV-2 spike glycoprotein based on the composite of Cu(OH)2 nanorods arrays as a high-performance surface substrate

The development of advanced electrode materials and the combination of aptamer with them have improved dramatically the performance of aptasensors. Herein, a new architecture based on copper hydroxide nanorods (Cu(OH)₂ NRs) are directly grown on the surface of screen printed carbon electrode (SPCE) using a two-step in situ, very simple and fast strategy and was used as a high-performance substrate for immobilization of aptamer strings, as well as an electrochemical probe to development a label-free electrochemical aptasensor for SARS-CoV-2 spike glycoprotein measurement. The Cu(OH)₂ NRs was characterized using X-ray Diffraction (XRD) and electron microscopy (FESEM). In the presence of SARS-CoV-2 spike glycoprotein, a decrease in Cu(OH)₂ NRs-associated peak current was observed that can be owing to the target-aptamer complexes formation and thus blocking the electron transfer of Cu(OH)₂ NRs on the surface of electrode. This strategy exhibited wide dynamic range in of 0.1 fg mL⁻¹ to 1.2 µg mL⁻¹ and with a high sensitivity of 1974.43 μA mM⁻¹ cm⁻² and low detection limit of 0.03 ± 0.01 fg mL⁻¹ of SARS-CoV-2 spike glycoprotein deprived of any cross-reactivity in the presence of possible interference species. In addition, the good reproducibility, repeatability, high stability and excellent feasibility in real samples of saliva and viral transport medium (VTM) were found from the provided aptasensor. Also, the aptasensor efficiency was evaluated by real samples of sick and healthy individuals and compared with the standard polymerase chain reaction (PCR) method and acceptable results were observed.