Simultaneous Fluorescence Lifetime Analysis Of Intracellular Cu⁺ And Ca²⁺ Based On DNA Nanosensor

Metals are vital for all living cells as the foundation of cellular metabolism and signal transduction.Among them,copper,as an essential trace element in organisms,plays an important role in maintaining normal physiological functions of human beings,growth of infants,development of brain,immunity of the human body and so on.Calcium is also an essential ion for various physiological activities in the organism.It maintains the membrane potential on both sides of the cell membrane,maintains normal muscle expansion and diastolic function,the conduction function between nerves and muscles,as well as the mechanism of action of some hormones.Cu⁺and Ca²⁺are closely associated with cellular metabolism and neuronal signal transduction,thus,simultaneous imaging and biosensing are vital for exploring relationship of Cu⁺and Ca²⁺in physiological and pathological processes.Here we developed the first fluorescence lifetime-based bipyramidal DNA nanosensor for real-time imaging and simultaneous quantification of Cu⁺and Ca²⁺in neurons,in which a new g-C₃N₄-based Cu⁺fluorescent probe and a new carbon dots-based Ca²⁺fluorescent probe were synthesized and assembled onto a bipyramidal DNA nanostructure together.The new nanosensor can quantify the variations of Cu⁺and Ca²⁺in neurons in response to ROS and aggregated Aβstimulation by two-photon fluorescence lifetime imaging.Using the new nanosensor,we discovered that Cu⁺could induce intracellular release of Ca²⁺,which may be a key signal of Cu⁺-induced neuronal apoptosis.Besides,ROS,pH and Aβcan affect the intracellular Cu⁺and Ca²⁺,which can further explore relationship of two ions.