Over the past decade, the development of amperometric sensors and biosensors using microfabrication techniques has gained considerable attention. This interdisciplinary approach aims at bringing together scientific fields such as: chemistry, physics, engineering and biology to achieve devices’ miniaturization, integration and automatization. Among the technologies that have been reviewed for the fabrication of the microelectrodes, the most common are: soft lithography and microfabrication techniques, such as physical vapor deposition of different metals, photolithography, chemical wet etching method and anodic bonding process. The required parameters in the design of a microfabricated electrode array, such as inter-electrode distance, the three-electrode system, and the role of each electrode have been intensively discussed. This review provides an overview about the state-of-the-art microfabrication devices and their applications, as well as the recent advances in the fabrication of microelectrodes as transducers for amperometric sensors, immunosensors and biosensors with various applications in environmental, biomedical and pharmaceutical fields.

Bisphenol A is an organic compound, belonging to the group of diphenylmethane derivates and is worldwide used in the fabrication of plastic and some resins. It leaches from plastic products and affects the environment and mostly the human body. BPA is known to be a xenoestrogen that mimics the role of hormones in the human body and disturbs the endocrine and reproductive systems. High doses are correlated with many disorders of the reproductive system. Being an electro-active molecule, it was intensively studied using electrochemical sensors with applications in food industry, environmental field and biomedical field. This review covers a big number of papers that had studied the electro oxidation of BPA from real samples using different types of electrochemical sensors.

A novel synthesized gold (Au)-reduced graphene oxide composite (rGO) was used for the fabrication of an electroactive paste inserted in a three-dimensional (3D)-printed platform for the determination of bisphenol A (BPA). The proposed method exhibits good response towards oxidation of BPA in the linear concentration range from 1.00 × 10⁻⁷ mol L⁻¹ to 1.00 × 10⁻² mol L⁻¹. The Au-rGO based 3D-printed platform determined BPA with a detection limit of 3.52 × 10⁻⁹ mol L⁻¹, in comparison with rGO based 3D-printed platform, where the limit of detection was 3.05 × 10⁻⁶ mol L⁻¹. Gold modification of rGO improves the sensitivity and electrochemical behavior of the material for BPA oxidation. The method was validated using five saliva samples collected from children.

Graphene decorated with gold nanoparticles (Au-rGO) was obtained in a single-step synthesis by exfoliating graphite rods via pulses of current. The morphological and structural features of Au-rGO were explored by TEM/SEM/EDX and XRD techniques. TEM images reveal the co-existence of thin and transparent sections corresponding to few-layer graphene along with darker regions corresponding to multi-layer graphene. Such a mixture was further confirmed by XRD examination of the sample. Au-rGO was next deposited on top of a screen-printed electrode (Au-rGO/SPE), and its electro-catalytic activity toward catechol oxidation was compared with that of a laccase-modified electrode (Lac/SPE). For Au-rGO/SPE, the dependence between the peak current and catechol concentration was linear within a wide range (1.0 × 10⁻⁹–1.0 × 10⁻³ M) with a sensitivity of 0.048 A/M. The limit of quantification was very low, 1.0 × 10⁻⁹ M, and the limit of detection was calculated to be 3.3 × 10⁻¹⁰ M (S/N = 3). In contrast, the Lac/SPE has three times lower sensitivity toward catechol (0.016 A M⁻¹) and a higher LOD (3.3 × 10⁻⁶ M). The Au-rGO/SPE was tested for the detection of catechol in tap and mineral water samples with recovery percentages from 90.9% to 100.1%.

This study addresses the necessity to monitor the presence of glyphosate (Gly) in waters, highlighting the need for on-site detection of Gly by using electrochemical sensors in environmental and agricultural monitoring programs. Two approaches were employed: (1) modification with graphene decorated with gold nanoparticles (AuNPs-Gr) and dispersed in either dimethylformamide (DMF) or a solution containing Nafion and isopropanol (NAF), and (2) molecularly imprinted polymers (MIPs) based on polypyrrole (PPy) deposited on gold SPEs (AuSPE). Electrochemical characterization revealed that sensors made of AuNPs-Gr/SPCE exhibited enhanced conductivity, larger active area, and improved charge transfer kinetics compared to unmodified SPEs and SPEs modified with graphene alone. However, the indirect detection mechanism of Gly via complex formation with metallic cations in AuNPs-Gr-based sensors introduces complexities and compromises sensitivity and selectivity. In contrast, MIPPy/AuSPE sensors demonstrated superior performance, offering enhanced reliability and sensitivity for Gly analysis. The MIPPy/AuSPE sensor allowed the detection of Gly concentrations as low as 5 ng/L, with excellent selectivity and reproducibility. Moreover, testing in real surface water samples from the Olt River in Romania showed recovery rates ranging from 90% to 99%, highlighting the effectiveness of the detection method. Future perspectives include expanding the investigation to monitor Gly decomposition in aquatic environments over time, providing insights into the decomposition’s long-term effects on water quality and ecosystem health, and modifying regulatory measures and agricultural practices for mitigating its impact. This research contributes to the development of robust and reliable electrochemical sensors for on-site monitoring of Glyphosate in environmental and agricultural settings.