PC12 live cell ultrasensitive neurotransmitter signaling using high quantum yield sulphur doped carbon dots and its extracellular Ca2+ ion dependence

Synthesizing bright, photostable and non-toxic doped fluorescent material is always a great challenge for its successful application. On the other hand, because of its very low concentration down to nM level, detection of neurotransmitter inside live cell is also very challenging. In this report, a novel one-step synthetic method for the synthesis of highly bright multicolor fluorescent sulphur doped carbon dots (CNDs), a new class of carbogenic nanomaterials, with quantum yield (QY) upto 58% is reported. The synthesized CNDs show ultrasensitive sensing for neurotransmitter dopamine (DA) detection without any surface functionalization using fluorometric assay down to 47 pM in water and 92 pM in blood plasma. Interestingly, the CNDs show very high selectivity to DA even in presence of high concentrations of other relevant interfering molecules. The CNDs are very efficient to detect the DA in live PC12 cell under hypoxic environment. We further provide fruitful information on Ca2+ dependent DA release inside neuron cells. It is still a debatable problem whether extracellular Ca2+ accelerates the DA release from synaptic vesicles or stored intracellular Ca2+ is sufficient for DA release. Our data shows that indeed extracellular Ca2+ influx inside neuron cells accelerates the DA release. (C) 2017 Elsevier B.V. All rights reserved.