Smart Additive-Manufactured Humanoid Electronic-Skin Model Based One-Drop-Touch Electrochemical Sensing of the Alprazolam Drug

This research article analyzes the state-of-the-art technologies of bio-inspired, next-generation humanoid electronic skin (e-skin) electrochemical aptasensors developed for the detection of alprazolam. Current wearable devices suffer from poor flexibility, low durability, limited sensitivity, and discomfort during long-term use, thereby necessitating the development of sensors for flexible, sensitive, and real-time health monitoring applications. Here, 3D-printed flexible humanoid e-skin (silicon sheet) mimics human skin and holds the potential to replicate realistic skin for wearable and artificial interface systems to achieve noninvasive, real-time monitoring of physiological parameters. The 3D-printed foundation consisted of a polylactic (PLA) filament that is not conductive, offering a high-tech design and support system for the sensitive conductive humanoid e-skin electrode. Chemically synthesized gold nano-bullets (AuNBs) were utilized to raise the sensor's sensitivity by accelerating electron transport. The synthesis of gold nano-bullets (AuNBs) has been confirmed using colorimetric change, UV-vis absorption at 529 nm, FTIR analysis of their functional groups, and transmission electron microscopy and the selected area electron diffraction (TEM-SAED) investigations demonstrating their homogeneously distributed with a mean particle size of 13.379 ± 1.029 nm and a lattice parameter of 4.078 Å, providing a large active surface for aptamer immobilization and sensitive electrochemical detection. Cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) were used for the detection of the drug analyte, i.e., alprazolam (ALP), the estimated limit of detection (LOD) and the linear range were as low as 0.001 and 0.001-10 µg/mL, respectively. The performance of reproducibility (5 times) and low relative standard deviation (RSD) and stability (20 days) were satisfactory. Kinetic parameters of the interaction of the humanoid e-skin aptamer with the analyte were also investigated using current response, effective electrode surface area, charge transfer resistance (Rct), double-layer capacitance (Cdl), and apparent electron transfer rate constant (Kapp). The AuNBs layer improved electron transfer kinetics, whereas aptamer immobilization and subsequent alprazolam binding modified the interfacial electrochemical characteristics, hence validating effective drug analyte identification by the aptasensor. This humanoid e-skin aptasensor showed adequate performance by estimation of cross-reactivity and spiked analyte concentrations in beverages. It is envisaged that humanoid e-skin electrochemical sensors are anticipated to significantly impact future healthcare by providing continuous, non-invasive monitoring and promoting a transition from traditional blood-based diagnostics to decentralized, personalized, and remote diagnostic systems.