Mo-W-O nanowire intercalated graphene aerogel nanocomposite for the simultaneous determination of dopamine and tyrosine in human urine and blood serum sample

A novel electrode for simultaneous detection of multiple heavy metal ions without pre-enrichment in food samples

Integrating a pre-enrichment step into electrochemical detection methodologies has traditionally been employed to enhance the performance of heavy metal detection. However, this augmentation also introduces a degree of intricacy into the sensing process and increases energy consumption. In this work, Mo-doped WO3 is grown in situ on carbon cloth by one-step electrodeposition. The electrode detect multiple heavy metal ions simultaneously in the range of 0.1-100.0 μM with LODs ranging from 11.2 to 17.1 nM. The electrode successfully detected heavy metal ions in diverse food samples. This pioneering detection strategy realized the direct and simultaneous detection of multiple heavy metal ions by utilizing the valence property of WO3 and oxygen vacancies generated by molybdenum doping. The Mo-WO3/CC pre-enrichment-free detection electrode boasts straightforward preparation, a streamlined detection procedure, swift response kinetics, and superior performance relative to previously reported electrodes, which makes it possible to develop a portable heavy metal ion detection device.

Oxygen vacancy-rich Fe2(MoO4)3 combined with MWCNTs for electrochemical sensors of fentanyl and its analogs

Hundreds of thousands of people dying from the abuse of fentanyl and its analogs. Hence, the development of an efficient and highly accurate detection method is extremely relevant and challenging. Therefore, we proposed the introduction of oxygen defects into Fe2(MoO4)3 nanoparticles for improving the catalyst performance and combining it with multi-walled carbon nanotubes (MWCNTs) for electrochemical detection of fentanyl and its analogs. Oxygen vacancy-rich Fe2(MoO4)3 (called r-Fe2(MoO4)3) nanoparticles were successfully synthesized and characterized in detail by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectrometry (EDS), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman spectra, BET, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) and investigated by comparison with oxygen vacancy-poor Fe2(MoO4)3 (called p-Fe2(MoO4)3). The obtained oxygen vacancy-rich Fe2(MoO4)3 was ultrasonically composited with MWCNTs for modification of glassy carbon electrodes (GCEs) used for the electrochemical detection of fentanyl and its analogs. The modified MWCNT-GCE showed ultrasensitivity to fentanyl, sufentanil, alfentanil, and acetylfentanyl with limits of detection (LOD) of 0.006 µmol·L-1, 0.008 µmol·L-1, 0.018 µmol·L-1, and 0.024 µmol·L-1, respectively, and could distinguish among the four drugs based on their peak voltages. Besides, the obtained r-Fe2(MoO4)3/MWCNT composite also exhibited high repeatability, selectivity, and stability. It showed satisfactory detection performance on real samples, with recoveries of 70.53 ~ 94.85% and 50.98 ~ 82.54% in serum and urine for the four drugs in a concentration range 0.2 ~ 1 µM, respectively. The experimental results confirm that the introduction of oxygen vacancies effectively improves the sensitivity of fentanyl electrochemical detection, and this work provides some inspiration for the development of catalytic materials for electrochemical sensors with higher sensitivity.

A colorimetric detection of dopamine in urine and serum based on the CeO2 @ZIF-8/Cu-CDs laccase-like nanozyme activity

This study reports a sensitive and selective colorimetric approach for the analysis of dopamine (DA) based on CeO2 @ZIF-8/Cu-CDs laccase-like nanozymes activity. The CeO2 @ZIF-8/Cu-CDs was synthesized using cerium oxide (CeO2 ) and copper-doped carbon dots (Cu-CDs) with 2-methylimidazole by a facilely hydrothermal approach. The CeO2 @ZIF-8/Cu-CDs exhibited excellent laccase-like nanozymes activity and can oxidize the colorless substrate (DA) to red product with 4-aminoantipyrine as the chromogenic agent. The Michaelis-Menten constant (Km ) and the maximal velocity (Vmax ) of CeO2 @ZIF-8/Cu-CDs are 0.20 mM and 1.48 μM/min, respectively. The detection method has a linear range of 0.05-7.5 μg/mL and a detection limit as low as 8.5 ng/mL with good reproducibility. The developed colorimetric sensor was applied to rapid and precise quantitative evaluation of DA levels in serum and urine samples. This study presents a new approach for detecting biological molecules by utilizing the controlled regulation of nanozymes' laccase-like activity.

Highly Sensitive and Selective Dopamine Determination in Real Samples Using Au Nanoparticles Decorated Marimo-like Graphene Microbead-Based Electrochemical Sensors

A sensitive and selective electrochemical dopamine (DA) sensor has been developed using gold nanoparticles decorated marimo-like graphene (Au NP/MG) as a modifier of the glassy carbon electrode (GCE). Marimo-like graphene (MG) was prepared by partial exfoliation on the mesocarbon microbeads (MCMB) through molten KOH intercalation. Characterization via transmission electron microscopy confirmed that the surface of MG is composed of multi-layer graphene nanowalls. The graphene nanowalls structure of MG provided abundant surface area and electroactive sites. Electrochemical properties of Au NP/MG/GCE electrode were investigated by cyclic voltammetry and differential pulse voltammetry techniques. The electrode exhibited high electrochemical activity towards DA oxidation. The oxidation peak current increased linearly in proportion to the DA concentration in a range from 0.02 to 10 μM with a detection limit of 0.016 μM. The detection selectivity was carried out with the presence of 20 μM uric acid in goat serum real samples. This study demonstrated a promising method to fabricate DA sensor-based on MCMB derivatives as electrochemical modifiers.

Biocompatible formulations based on mycosynthesized iron oxide nanoparticles: Fabrication, characterization, and biological investigation

The current study was carried out to synthesize iron oxide nanoparticles (IONPs) via green reduction method from a wild mushroom collected from Quaid-i-Azam University, Islamabad, Pakistan. The collected fungus was identified as Daedalea sp. based on morphological characteristics. Prepared NPs were produced from iron chloride hexahydrate with fungal filtrate via combustion method. The as prepared NPs were characterized by using different techniques for example, scanning electron microscopy (SEM), X-ray diffractions (XRD), Fourier transform infrared spectroscopy (FT-IR), and ultraviolet visible (UV-Vis) spectroscopy. Morphology and size of the NPs were determined by SEM analysis. XRD study revealed crystalline nature of IONPs. The FT-IR spectrum exhibited peak at 3390.26 cm^{- 1} stretching that described the strong O-H band of the alcohol associated with mushroom texture. The major IONPs dose (0.75 mg/ml) demonstrated 71% growth inhibition against Aspergillus. Excellent antibacterial activities against Pseudomonas aeruginosa (28 mm), and Klesbsilla pneumonia (28 mm) were represented by the fabricated NPs. Further, highest reducing power (53.22 ± 0.72 µg AAE/mg) was shown by the highest administrated dose (400 µg/ml). Maximum 2,2-diphenyl-1-picrylhydrazyl and trolox antioxidant activity free radical scavenging activities at 400 µg/ml IONPs concentration were noted as 51.29 ± 0.48, and 83.12 ± 0.28 trolox equivalent antioxidant capacity, respectively. In brief, the negligible hemolytic activity against human red blood cells at the highest concentration (400 µg/ml), as well as, moderate antioxidant activities at low concentration suggest the application of the fabricated NPs in environmentally sound viable hygiene production.

SERS determination of dopamine using metal-organic frameworks decorated with Ag/Au noble metal nanoparticle composite after azo derivatization with p-aminothiophenol

A specific surface-enhanced Raman scattering (SERS) assay for dopamine (DA) based on an azo derivatization reaction is proposed for the first time by preparation of p-aminothiophenol (PATP)-modified composite SERS substrate, composed of metal-organic framework (MIL-101) decorated with Au and Ag nanoparticles. As the result, the SERS method for detection of the azo reaction between PATP and DA exhibits superior sensitivity, selectivity, and stability. A reasonable linearity in the range 10^-6 to 10^-10 mol∙L^-1 is achieved, and the limit of detection is 1.2 × 10^-12 mol∙L^-1. The reactive SERS assay is free from interference in complex physiological fluid. The feasibility of the proposed SERS method for the detection of DA levels in fetal bovine serum (FBS) samples and human serum samples is validated by HPLC-MS methods, displaying promising application potential in early disease diagnosis.

Synchronous electrochemical detection of dopamine and uric acid by a PMo12@MIL-100(Fe)@PVP nanocomposite

In this work, a noble-metal-free composite electrode was prepared based on PMo₁₂O₄₀^3- (PMo₁₂), C₉H₅FeO₇ (MIL-100(Fe), a Fe-based metal organic framework) and polyvinylpyrrolidone (PVP), and served as a high performance electrochemical sensor for synchronous detection of dopamine (DA) and uric acid (UA). The PMo₁₂@MIL-100(Fe)@PVP composite electrode was fabricated by a in-situ hydrothermal method. Thanks to the synergistic effect of three active components (PMo₁₂, MIL-100 and PVP), the electrode possesses large specific surface area and high electrical conductivity and therefore it shows high electrocatalytic oxidation performance of DA and UA with a spacing of 0.146 V between the two peak positions. These benefits of the electrode enable its electrochemical sensor to synchronously detect of DA and UA. Namely, the linear ranges can achieve 1-247 μM for DA and 5-406 μM for UA. Meanwhile, the detection limits are 0.586 μM for DA and 0.372 μM for UA. Moreover, the sensor can be applied to simultaneous determination of UA and DA in human serums with satisfactory recovery values.

CoFe2O4 supported g-C3N4 nanocomposite for the sensitive electrochemical detection of dopamine

The CoFe2O4@g-CN modified electrode has been applied for the real-time detection of DA in human biological samples with appreciable recovery results.