Quantum dot-enabled optical codes for neurotransmitter sensing at the bio-nano interface with translational relevance.

Quantum dots (QDs), including semiconductor (Cd-based and III-V), carbon/graphene, and emerging halide perovskite QDs, offer size-tunable, bright, and photostable optical signals, making them uniquely suited as nanoreporters for neurotransmitter sensing. This review surveys recent advances in QD chemistry and surface engineering, recognition strategies (aptamers, molecularly imprinted polymers, enzymes, and small-molecule ligands), and signal transduction modalities (photoluminescence quenching/turn-on, FRET, electrochemiluminescence, and photoelectrochemical detection). We emphasise integration at the bio-nano interface for clinically relevant, minimally invasive platforms such as microfluidic sampling, wearable patches, and implantable probes, and analyse the principal barriers to translation (toxicity, stability in aqueous/biofluids, selectivity interferents, and quantitation). Finally, we highlight promising directions: multiplexed spectral coding, ratiometric and lifetime-based readouts, renal-clearable/biodegradable QDs, and hybrid QD-polymer platforms for continuous monitoring of neurochemical signatures in diagnostic settings.