Applications and challenges of graphene, MXenes, and transition metal dichalcogenides in electrochemical sensors for doping detection

The integrity of competitive sports is perpetually challenged by the illicit use of performance-enhancing drugs. While laboratory-based methods like mass spectrometry represent the gold standard for confirmatory analysis, their inherent limitations in terms of cost, complexity, and turnaround time preclude their use for widespread, on-site screening. Electrochemical sensors have emerged as a powerful alternative, offering the potential for rapid, portable, and low-cost detection. This paradigm shift has been significantly accelerated by the advent of two-dimensional (2D) materials, whose unique physicochemical properties provide an ideal platform for developing next-generation sensing devices. This review provides a comprehensive and critical analysis of the application of 2D materials, including the graphene family, transition metal dichalcogenides (TMDs), and MXenes, in electrochemical sensors for detecting various classes of doping agents. Representative 2D-material-based platforms already achieve figures of merit compatible with anti-doping requirements, with rGO/CTAB-modified electrodes detecting testosterone down to 0.1 nM in urine and blood, MXene Ti₃C₂Tₓ–Fe₂O₃ aptasensors reaching limits of detection as low as 1.53 pg/mL across clinically relevant concentration ranges, and graphene-based stimulant sensors delivering stable electrochemical readouts from complex samples within tens of seconds to a few minutes. We critically examine the core arguments, controversies, and supporting evidence surrounding the performance of each material class, focusing on the intrinsic trade-offs between conductivity, functionalizability, and environmental stability. Furthermore, we delve into the overarching challenges that impede the transition from laboratory prototypes to field-deployable devices, namely the difficulties in scalable and reproducible material synthesis, the pervasive issue of biofouling in complex biological matrices, and the imperative for achieving high selectivity. Strategic solutions, including advanced surface modification techniques and the integration of specific molecular recognition elements like aptamers and molecularly imprinted polymers, are discussed in detail. Finally, we explore the future trajectory of the field, highlighting the integration of 2D material sensors into advanced systems such as wearable devices and microfluidic platforms, the development of multiplexed sensor arrays for simultaneous multi-analyte detection, and the transformative role of machine learning in processing complex sensor data to deliver actionable insights. The convergence of these technologies promises to revolutionize anti-doping enforcement, shifting the paradigm from reactive, post-competition testing to proactive, continuous monitoring to safeguard the health of athletes and ensure fair play.