Dopamine (DA) is an important neurotransmitter in the kidney, cardiovascular system, and central nervous system, which abnormality is associated with many diseases. In this work, we synthesized a functionalized multi-walled carbon nanotube/silver nanoparticle (f-MWCNT/ AgNP) nanocomposites as the biosensing material to detect DA. The SEM, EDS, and TEM characterizations indicated the success of the functionalization process with MWCNT as the base material. The values of the linear range, the limit of detection (LOD), and the selectivity of the nanocomposite were all obtained from the Differential Pulse Voltammetry (DPV) measurements. The obtained LOD value was 0.2778 mM in the linear range of 0-8 mM, which is lower than the required concentration value for detecting DA in human urine (0.3-3 mM). The biosensor's high selectivity on DA with the presence of other human-related biofluids was also reported. These results show that f-MWCNT/AgNP nanocomposites are a promising biosensor material for the detection of DA.
We demonstrated potential features of gold nanoparticle bipyramid (AuNB) for an electrochemical biosensor. The facile synthesis method and controllable shape and size of the AuNB are achieved through the optimization of cetyltrimethylammonium chloride (CTAC) surfactant over citric acid ratio determining the control of typically spherical Au seed size and its transition into a penta-twinned crystal structure. We observe that the optimized ratio of CTAC and citric acid (CA) facilitates flocculation control in which Au seeds with size as tiny as ~14.8 nm could be attained and finally transformed into AuNB structures with an average length of ~55 nm with high reproducibility. To improve the electrochemical sensing performance of a screen-printed carbon electrode (SPCE), surface modification with AuNB via distinctive linking procedures effectively enhanced the electroactive surface area by 40%. Carried out for the detection of dopamine (DA), a neurotransmitter frequently linked to the risk of Parkinson’s, Alzheimer’s, and Huntington's diseases, the AuNB decorated-carbon electrode shows outstanding electrocatalytic activity that improves sensing performance, including high sensitivity, low detection limit, wide dynamic range, high selectivity against different analytes, such as ascorbic acid (AA), uric acid (UA) and urea, and excellent reproducibility.
In this study, we reported the construction of Gold Nanospike (AuNS) structures on the surface of screen-printed carbon electrode (SPCE) used for non-enzymatic electrochemical detection. This modification was prepared with a one-step electrodeposition method by controlling the electrodeposition parameters, such as applied potential and deposition time, via Constant Potential Amperometry (CPA). Those parameters and precursor solution concentration were varied to investigate the optimum electrodeposition configuration. The results confirmed that AuNS were homogenously deposited and well-dispersed on the working electrode surface of SPCE. The AuNS-modified SPCE was implemented as a non-enzymatic sensor toward dopamine and could enhance the electrocatalytic ability compared with the bare SPCE. Further examination shows that the sensing performance of the AuNS-modified SPCE produced an increase in electrochemical surface area (ECSA) at 17.25 times higher than the bare electrode, a sensitivity of 0.056 µA mM−1 cm−2 with a wide linear range of 0.2–50 µM and a detection limit of 0.33 µM. In addition, AuNS-modified SPCE can selectively detect dopamine among other interfering analytes such as ascorbic acid, urea, and uric acid, which commonly coexist in the body fluid. This work demonstrated that AuNS-modified SPCE is a prospective sensing platform for non-enzymatic dopamine detection.
The rise of wearable technology has gradually shifted modern health monitoring from clinical to personal use. Smart wearables can collect physiological signals and show them directly on a smartphone. In contemporary healthcare scenarios, this big data could aid medical doctors in online health analysis. Most currently available wearables are designed to monitor specific health parameters, while the combination of many devices is practically not convenient and not cost-effective. Therefore, a strong trend is towards the development of multifunctional devices. This demands, however, alternative sources of power other than conventional batteries. The concept of human-body-powered biosensing textiles (HBBTs) addresses this challenge. By harvesting energy produced from the human body such as motion, pressure, vibration, heat, and metabolites and converting them into electricity, HBBTs could potentially work without a battery. Additionally, the textiles themselves provide a suitable substrate for interconnects and biosensors, such that a system based on HBBTs could provide multifunctional health monitoring. This review explains the fundamental theories, the classification, the energy-conversion efficiency assessment, and the possible biomonitoring applications of HBBTs. Furthermore, we discuss the challenges for technology maturity and the perspectives of HBBTs in shaping the future of health monitoring.
In this article, we presented the development of fully modular microfluidic flow cells for an electrochemical using 3D printing. The proposed devices are potential for electrochemical measurements using a small sample volume on a fully portable, reusable, simply fabricated, low-cost, PDMS-free, and leakage-free flow cell. This concept offers a simple, controllable sample over the conventional electrochemical platform with a three-electrode system, which requires a considerable volume of samples or a non-controllable drop cast method for sequential protocols. We demonstrated an easy alignment and lock, namely, click-and-fit modular microfluidics, for quick and easy assembly and disassembly of flow cell modules using magnetic force instead of the screw, polymer glue, or resin. Two microfluidic modules were presented using tube- and syringe-flow cells (TFC and SFC) to integrate the screen-printed carbon electrodes (SPCE) in the electrochemical sensor. The proof-of-concept of the integrated sensor-microfluidic platforms was conducted under cyclic voltammetry using a tiny volume of a ferricyanide redox probe at only ~50 µL, differential pulse voltammetry, and square wave voltammetry. Implementing the proposed click-and-fit microfluidic modules in electrochemical detection achieves higher current peaks than droplet measurements. These flow cell modules are promising for biosensing applications using a small volume of physiological fluid samples.
In lab-on-chip development, screen printed electrode (SPE) method is usually utilized as an electrochemical sensor. As a basic conductive material, carbon has several advantages compared to other conductive materials. SPE performance can be enhanced by using a nanomaterial due to its unique properties, such as its small size particle and large surface area that can accelerate the electron transfer on the surface of the electrode. Graphene as a carbon-based nanomaterial is an extraordinary material to work with because of its good electrical conductivity and large specific surface area. In this work, we developed a graphene paste from the water-based graphene ink with the addition of polyurethane binder material to realize a nanocarbon conductive paste, which insoluble in water and other electrolytes. Our graphene paste was deposited on the working electrode area of SPE and the performance was tested using cyclic voltammetry method. The result showed that the optimal ratio for the graphene carbon paste, polyurethane to graphene ink, was 1:15 %vol. With this ratio, the performance of the modified SPE could successfully be increased and it also showed a stable sensing performance by having a low error value, below 3%, for 7 times of repeated measurements.
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