Upconversion Nanoplatform for FRET-Based Sensing of Dopamine and pH

Dopamine (DA) plays a very critical role in controlling the key functionalities, such as in metabolic, memory and behavioural aspects. The deviation from the normal range of concentration has been linked to serious neurological disorders and cancers. Therefore, development of a facile sensing platform with a prospective potential to be applied in the real-time analysis of DA in vivo holds a great promise. To achieve this, an upconversion nanoparticle (UCNP) based nanoplatform with mesoporous silica functionality (BSCU-MS) has been proposed as an efficient DA sensing probe. The UCNP has been tuned to exhibit emission in particular region with high PL intensity that could be selectively absorbed by the DA in quinone form (q-DA) through Forster resonance energy transfer (FRET) mechanism. We showed that the proposed nanoplatforms are capable of detecting DA in a sensitive and very selective manner with the limit of detection (LOD) as 0.63 nM (with S/N=3). Also, owing to the interesting electronic behaviour of DA to undergo pH-dependent oxidation and reduction process, we also demonstrate the applicability of DA loaded BCSU-MS for fluorescence-based pH sensing. We propose that the method described offers a very promising and efficient strategy for the detection of DA-related diseases and the ensuing physiological pH changes.