For the millions living with Parkinson's disease or schizophrenia, monitoring dopamine levels currently requires invasive procedures or indirect proxies. A new electrochemical sensing platform built on laser-induced graphene suggests that tears — one of the body's most accessible biofluids — may one day serve as a window into neurological status, potentially transforming how clinicians track disease progression without a single needle.

The sensor was fabricated by treating a graphene substrate with nickel nitrate and urea, creating a porous, nitrogen-doped structure confirmed via Raman spectroscopy and scanning electron microscopy. This functionalization dramatically increased active surface sites and accelerated electron transfer kinetics, enabling dopamine oxidation to be detected electrochemically with high sensitivity. Using differential pulse voltammetry, the device achieved a detection limit of 17.86 nmol·L⁻¹ and a linear range of 0.25–16.44 μmol·L⁻¹ in buffered solution — well within the physiologically relevant tear dopamine range. Crucially, when tested in both synthetic and real tear fluid across four concentration points (3.23–9.32 μmol·L⁻¹), recovery rates approached 100%, indicating the sensor resists matrix interference from proteins and salts naturally present in tears.

This work sits within a rapidly expanding field of wearable and point-of-care bioelectronics, where tears have attracted growing interest alongside sweat and saliva as non-invasive sampling matrices. Dopamine in tears is not a well-characterized surrogate for central nervous system dopamine — the blood-brain barrier and peripheral dopamine metabolism complicate direct translation — and this remains the study's most significant unresolved question. The current work is a proof-of-concept with no clinical cohort, no longitudinal validation, and no comparison against established dopaminergic biomarkers. That said, the near-perfect analytical recovery in real tear samples, combined with the low-cost laser-fabrication method, gives this approach genuine translational credibility. It is an incremental but technically solid step toward wearable neurological monitoring devices that clinicians and patients would find genuinely practical.