A Single Silicon Nanowire-Based Ratiometric Biosensor for Ca at Various Locations in a Neuron.

Ionic calcium (Ca) is an important second messenger in cells, particularly in the neuron. A deficiency or excess of Ca would lead to neuronal apoptosis and further injury to the brain. For accurate analysis of intracellular Ca, a single silicon nanowire (SiNW)-based ratiometric biosensor was constructed by simultaneously anchoring Ru(bpy)(mcbpy-O-Su-ester)(PF), as a reference molecule, and Fluo-3, as a response molecule, onto the surface of a single SiNW. The SiNW-based biosensor exhibits high sensitivity and favorable selectivity for detecting Ca. With the assistance of a micromanipulator and laser scanning confocal microscope, two single SiNW sensors were placed in the body and the neurites of an individual neuron to detect Ca. The difference between the concentrations of Ca in the body and neurites was identified. The results from the present study provide new insights into Ca in neurons at a high spatial resolution, and the strategy used in this study provides a new opportunity to investigate cellular metabolism by combining the advantages of a single-cell detection technique and physiology.