A scalable opto-electrochemical sensor for salivary and urinary detection of ketamine: towards selective assay by naked-eye.

Despite the therapeutic potential of ketamine (KET) as a psychoactive drug, off-dose use or abuse may lead to irreversible consequences, ranging from mild to severe dependency, cardiovascular complications, and even death. Thus, its accurate detection in human biological samples is essential. In this study, a novel opto-electrochemical sensor is developed based on a scalable indium tin oxide (ITO) surface modified with molecularly imprinted polymer (MIP) using β-cyclodextrin (β.CD) and polyaniline (PANI) for the selective detection of KET. In the embedded sensing interface, the β.CD serves as a host molecule to form specific cavities for KET entrapment, and PANI acts as an electrochromic material. This strategy enables visual detection via vivid color changes that correspond to KET concentration, along with electrochemical outputs. The sensor exhibits a linear response range from 1 to 700 nM, with a detection limit of 0.33 nM (S/N = 3) and a limit of quantification of 3.3 nM (± 0.002 nM) across electrochemical, optical, and RGB signals. Selectivity tests against structurally similar drugs confirm negligible cross-reactivity toward KET. Real sample analysis in human urine and saliva, with recoveries between 99.45% and 101.68%, validates the sensor's reliability. The dual-mode capability-electrochemical and visual-combined with green chemistry compliance (AGREE score: 0.84) promises the sensor's potential to provide technical support for point-of-care applications in clinical diagnostics and forensic medicine.