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 µM in the linear range of 0–8 µM, which is lower than the required concentration value for detecting DA in human urine (0.3–3 µM). 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. Graphical abstract

Dopamine concentration abnormalities in the body can cause various disorders and diseases such as Parkinson's, Tourette's syndrome, and depression. In this study, graphene oxide (GO) was combined with Fe₃O₄ to sensitively and selectively detect dopamine. The performance was evaluated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. The results of testing with CV on the solution [Fe(CN)₆] showed that a modification with GO gave a maximum effective surface area value of 0.0127 cm², proving that GO can increase the effective area and conductivity of the sensor. DPV testing shows that dopamine detection using GO/Fe₃O₄ has a linear range at a concentration of 1–10 μM with a detection limit of 0.48 μM and a quantification limit of 1.6 μM. GO/Fe₃O₄ also shows good selectivity where the peak current is separated by 0.245 V with ascorbic acid, which is the closest interference compound. Graphical Abstract

Research on the application of graphene (G) and graphene quantum dots (GQDs) for biomedical engineering has attracted much attention over the last decade. Graphene and its derivatives have shown great biocompatibility, solubility, selectivity, large surface area, high purity, biofunctionalization, high drug loading capacity, and cell membrane penetration capability potential to be applied in biomedical engineering areas. The unique physical and chemical properties of GQDs, including small size, chemical inertness, high photoluminescence stability, low cytotoxicity, and good biocompatibility, made them a promising candidate for biomedical engineering applications. The recent progress related to the development of G and GQDs toward biomedical engineering applications is presented in this work. This study reviews and discusses the development of G and GQDs, both top-down and bottom-up synthesis methods, for biomedical engineering applications, such as biosensing, tissue engineering, drug delivery, bioimaging, antibacterial, and antiviral.

Electrochemical method is often chosen to analyze various bio-chemical reactions due to its operation simplicity with versatile applications. Thus, for this purpose, the procurement of potentiostat, an electrochemical-based analysis instrument, also needs to focus on the low price, but maintaining its rich analysis features. In this paper, we designed a low-cost and portable potentiostat system based on the ESP32 microcontroller. Even with the low-cost system design, it supports various electrochemical measurement methods, i.e. cyclic voltammetry (CV), linear sweep voltammetry (LSV), square wave voltammetry (SWV), differential pulse voltammetry (DPV), normal pulse voltammetry (NPV), and the observation of electrochemical current against time based on chronoamperometry measurement method. The potentiostat performance was assessed by the electrochemical signal accuracy and errors. Furthermore, the measurements can also be carried out semi-parallelly within three measurement channels simultaneously. The results showed that it could produce voltammograms with an average accuracy of more than 90%, compared to the commercial Emstat Pico. Even though having this comprehensive and extensive electrochemical analysis, the cost of the total system realization could be downsized to only USD 21.4.

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.