Mitochondria-Targeted DNA Nanoprobe for Real-Time Imaging and Simultaneous Quantification of Ca ²⁺ and pH in Neurons

Herein, a single highly selective DNA nanoprobe was designed and created for the real-time imaging and simultaneous quantification of two kinds of biological species using Ca ²⁺ and pH; the molecules were selected as models because of their close relationship with cellular functions and diseases. A Ca ²⁺ fluorescent probe was synthesized and assembled onto a DNA nanostructure together with pH-responsive, inner-reference, and mitochondria-targeted molecules. This nanoprobe with high spatial resolution, together with long-term fluorescent and structural stability, powerfully tracked pH and Ca ²⁺ dynamics at the same localization in mitochondria in response to O ₂ ^•- -induced oxidative stress and aggregated amyloid β (Aβ) stimulation with a temporal resolution of milliseconds. Using this tool, we discovered that O ₂ ^•- and Aβ triggered transitory cytoplasmic acidosis and then activated acid-sensing ion channel 1a (ASIC1a) in the mitochondrial membrane, leading to mitochondrial Ca ²⁺ overload and pH abnormalities, which contribute to neuron death. Moreover, psalmotoxin 1 effectively protected against O ₂ ^•- - and Aβ-induced neuron injury.