Methylene blue intercalated aptamer to amplify signals toward sensitively electrochemical detection of dopamine released from living Parkinson's disease model cells

Dopamine plays a critical role in some fatal diseases including Parkinson's disease, schizophrenia, Tourette syndrome and HIV infection studies but its detection sensitivity demands further improvement. Aptamer-based biosensor has good selectivity to detect biologically active substances; however, it is very challenging to achieve high sensitivities for practical applications. Here an electrochemical biosensor is constructed by hollow carbon spheres, aptamer and methylene blue (MB) to monitor dopamine released from Parkinson's disease model (SH-SY5Y) cells with a low detection limit, wide detection range, high sensitivity and good selectivity for much better performance than reported aptamer sensors. Investigation discovers that MB intercalation in aptamers can offer two sites to absorb two dopamine through π-π interaction instead of one DA absorption on an aptamer alone, thereby doubling the detection sensitivity. The sensor was further used to monitor dopamine released from SH-SY5Y cells, clearly confirming the effect of 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine on dopamine synthesis in SH-SY5Y cells and demonstrating the great potential of the sensor in real-time detect dopamine released from living cells. This work renders a new avenue to amplify the detection sensitivity by intercalating redox small molecule to increase the aptamer reaction sites while bridging the interfacial electron transfer.