The dosage of neurological drugs greatly influences the kinetics of body fluids. The treatment of neurological diseases like Parkinson's and Alzheimer's is dose-dependent. As such, quantitative analysis of neurological drugs is critical to regulating the biological functions of body fluids.
Study: 2D MXene/Graphene Nanocomposite Preparation and Its Electrochemical Performance Towards the Identification of Nicotine Level in Human Saliva. Image Credit: Danijela Maksimovic/Shutterstock.com
An article published in the Journal of Hazardous Materials demonstrated the fabrication of a two-dimensional (2D) hybrid MXene/graphene (MX/Gr) film to prepare an electrochemical transducer for electrochemical sensing of nicotine.
Analytical methods including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution scanning electron microscopy (HR-SEM) were used to confirm the formation of Gr sheets, MX, and MX/Gr hybrid film.
Furthermore, the MX/Gr hybrid nanocomposite was used to modify the glassy carbon electrode (GCE) for detecting nicotine in a phosphate buffer solution (PBS). The MX/Gr/GCE-based sensor showed a linear response against nicotine from concentrations 1 to 55 micromoles and 30 to 500 micromoles with a limit of detection (LOD) of 290 and 0.28 nanomoles, respectively.
Thus, the MX/Gr hybrid film-modified electrode developed in the present study was sensitive and selective towards nicotine with high reproducibility. Ultimately the practical application of the designed sensor was demonstrated by detecting nicotine in artificial and human saliva samples.
Nicotine Sensing Methods
Nicotine is a plant-derived toxic drug (alkaloid) that hampers the central nervous system when consumed, leading to neurodegenerative disorders like Parkinson's and Alzheimer's disease. Tobacco has about 1 to 3 % nicotine, and smoking tobacco can cause respiratory issues, stroke, heart attack, and even causes severe brain damage.
The presence of nicotine in the concentration range between 500 and 800 nanomoles in body fluids leads to physiological damage in humans. Thus, it is critical to detect the concentration of nicotine in the body fluids of humans, toxicology samples, drugs, and other fields.
Although the detection of nicotine using gas chromatography-mass spectrometry, capillary electrophoresis (CE), and high-performance liquid chromatography (HPLC) provide accurate detection levels of nicotine, these are expensive and time-delayed apparatus, requiring highly skilled technical personnel.
Nanomaterial-based electrodes have been used in electrochemical nicotine sensing. However, all the reported methods exhibited drawbacks, including the need for expensive reagents/chemicals, electrode fouling, complicated sample preparation, and the sensor’s poor stability.
Graphene is a two-dimensional (2D) material made of carbon with outstanding electrical properties, electrochemical activity, conductivity, and biocompatibility. In addition, the surface functionalization of graphene enhances these properties.
MXenes have witnessed remarkable progress in two-dimensional (2D) materials. MAX phase has a general formula Mn+1AXn, where M is attributed to early transition metals, A is essentially a group of 13 or 14 elements, and X represents either/both carbon and nitrogen. Mxene is obtained by selective etching of the ‘A’ element from the MAX phase to mostly yield carbide and nitrides.
MX/Gr Nanocomposite Towards Nicotine Sensing
In the present work, MXene and graphene sheet dispersion was synthesized via a top-down method. The presence of functional groups on the surface of Gr enhanced the stability of MXene dispersion. The analytical methods, including Raman spectroscopy, TEM, HR-SEM, XPS, and XRD, confirmed the formation of MX/Gr hybrid film.
The electrode modified with MX/Gr hybrid film had high electrocatalytic activity against the oxidation of nicotine in PBS at a pH of 7.4. Here, PBS electrolyte helped simulate the physiological condition during electrochemical sensing of nicotine.
The sensor modified with MX/Gr film showed a linear response for nicotine from 30 nanomoles to 500 micromoles and 1 to 55 micromoles with sensitivities of 0.527 and 3.5 amperes per micromoles per square centimeters and LODs of 0.28 nanomoles and 0.29 micromoles, respectively.
Furthermore, the experimental studies on MX/Gr hybrid film-based sensor’s selectivity, repeatability, and stability demonstrated that the sensor showed high selectivity with longer stability, despite the presence of interfering molecules. Finally, the MX/Gr hybrid film-based sensor was used for the accurate detection of nicotine levels in artificial and human saliva samples.
Conclusion
In summary, MX/Gr nanocomposite-modified electrode was present as a new sensor for accurate detection of nicotine with high selectivity and sensitivity. The analytical methods, including Raman, TEM, HR-SEM, XPS, and XRD, confirmed the successful synthesis of Gr sheets bonded with MX layers.
The MX/Gr nanocomposite-coated electrode showed a high oxidation peak current density at reduced over-potential for nicotine compared to other modified sensors and electrodes. The fabricated new sensor modified with MX/Gr nanocomposite had a wide detection range with low LOD for nicotine with good repeatability and high stability, demonstrating the efficiency of MX/Gr film in preparing electrochemical transducers to analyze the levels of nicotine in a wide range of samples.
The new MX/Gr hybrid film-based sensor was applied for nicotine levels detection in artificial and human saliva samples using 0.1 molar PBS as the electrolyte, demonstrating a recovery rate of 98.1 to 100.9%.
Reference
Rajendran,J ., Sundramoorthy, AK., Ganapathy, D., Atchudan, R., Habila, MA., Nallaswamy,D. (2022) 2D MXene/Graphene Nanocomposite Preparation and Its Electrochemical Performance Towards the Identification of Nicotine Level in Human Saliva. Journal of Hazardous Materials. https://www.sciencedirect.com/science/article/pii/S0304389422014984?via%3Dihub
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