Fabrication of a novel HKUST-1/CoFe2O4/g-C3N4 electrode for the electrochemical detection of ciprofloxacin in physiological samples

In this work, a novel HKUST-1/CoFe2O4/g-C3N4 electrode was successfully prepared via the hydrothermal method and the high-temperature calcination method, which can be applied as an electrochemical sensor for the precise detection of ciprofloxacin (CIP) in physiological samples. The novel electrode was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR), and its electrochemical performance was further evaluated via the cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The results demonstrated that the HKUST-1/CoFe2O4/g-C3N4 electrode exhibited an optimal linear range of 0.05-180 μmol L-1 for the CIP detection, which demonstrated a low limit of detection (LOD) of 0.0026 μmol L-1 and a low limit of quantitation (LOQ) of 0.0087 μmol L-1, respectively. Additionally, the novel semiconductor sensors exhibited exceptional selectivity, stability and repeatability in the determination of CIP. The recovery rate of CIP was found to range from 98.00% to 104.00% in serum, with the relative standard deviations (RSD) below 2.62% (n = 5), while the recovery rate of CIP was found to range from 96.00% to 105.00%, with the RSD less than 3.23% (n = 5) in urine. The current study extends to the application of the semiconductor-based electrochemical sensors and offers a new approach for the clinical pharmaceutical analysis to ensure medication safety, which could provide valuable insights into the potential of semiconductor sensors for future clinical applications.

An efficient electrochemical sensor based on the Ce-MOF/g-C3N5 composite for the detection of nitrofurazone

The Ce-MOF/g-C3N5 composite was first constructed using a simple reflux method in an oil bath. Herein, we report that the electrochemical sensor fabricated based on this composite exhibits high performance in the detection of nitrofurazone. Interestingly, this sensor exhibits an extra-wide linear range of detection composed of two line segments (7-100 μM and 100-2913 μM), as well as a low detection limit (LOD) of 6.15 μM (S/N = 3) under optimal experimental conditions. Additionally, the sensor demonstrates exceptional selectivity, reproducibility and stability. More importantly, the proposed electrochemical sensor can effectively monitor nitrofurazone in real samples such as urea and tap water, and obtain ideal recoveries. The sensor has such excellent performance because of the synergistic effect of the two components in the Ce-MOF/g-C3N5 composite. Compared with Ce-MOF, the introduction of g-C3N5 effectively not only enhances the conductivity of Ce-MOF/g-C3N5 but also exposes more active sites, which is conducive to increasing the electrocatalytic activity to reduce nitrofurazone. This research contributes new scientific research ideas for fabricating ideal electrochemical sensors based on g-C3N5 and MOFs.

Constructing a Hydrophilic Microsensor for High-Antifouling Neurotransmitter Dopamine Sensing

Real-time sensing of dopamine is essential for understanding its physiological function and clarifying the pathophysiological mechanism of diseases caused by impaired dopamine systems. However, severe fouling from nonspecific protein adsorption, for a long time, limited conventional neural recording electrodes concerning recording stability. This study reported a high-antifouling nanocrystalline boron-doped diamond microsensor grown on a carbon fiber substrate. The antifouling properties of this diamond sensor were strongly related to the grain size (i.e., nanocrystalline and microcrystalline) and surface terminations (i.e., oxygen and hydrogen terminals). Experimental observations and molecular dynamics calculations demonstrated that the oxygen-terminated nanocrystalline boron-doped diamond microsensor exhibited enhanced antifouling characteristics against protein adsorption, which was attributed to the formation of a strong hydration layer as a physical and energetic barrier that prevents protein adsorption on the surface. This finally allowed for in vivo monitoring of dopamine in rat brains upon potassium chloride stimulation, thus presenting a potential solution for the design of next-generation antifouling neural recording sensors. Experimental observations and molecular dynamics calculations demonstrated that the oxygen-terminated nanocrystalline boron-doped diamond (O-NCBDD) microsensor exhibited ultrahydrophilic properties with a contact angle of 4.9°, which was prone to forming a strong hydration layer as a physical and energetic barrier to withstand the adsorption of proteins. The proposed O-NCBDD microsensor exhibited a high detection sensitivity of 5.14 μA μM-1 cm-2 and a low detection limit of 25.7 nM. This finally allowed for in vivo monitoring of dopamine with an average concentration of 1.3 μM in rat brains upon 2 μL of potassium chloride stimulation, thus presenting a potential solution for the design of next-generation antifouling neural recording sensors.