Carbon Dots-based Fluorescent Probes For Monitoring And Imaging Of Functional Molecules In Alzheimer's Disease

Alzheimer's disease is the most common neurodegenerative disease of the central brain system.Previous studies have shown that,in addition to the well-known pathological features of amyloid peptide plaque deposition and neurofibrillary tangles,many patients of AD exhibit varying degrees of neuronal loss in the brain,which is closely related to specific gene expression disorders in the brain,such as microRNAs Furthermore,these pathological changes of AD are also the result of dysregulation of intracellular autophagy and apoptosis.Therefore,it is of great significance to conduct pathological analysis of Alzheimer's disease from the perspective of genetic material changes and intracellular molecular mechanism.Aimed at the above two aspects of the problem,this paper has launched a deep exploration to understand the AD pathology.In the first work,we successfully established a two-photon fluorescent probe for the detection of miR-9 in neurons and deep brain tissues of AD mice model(APP/PS1).Combining the red fluorescence emissive CDs with the enzyme-free fluorescence signal amplification design of the optical isomerism of azobenzene,the prepared probe showed good selectivity toward miR-9,with the detection limit as low as 0.57 fM.We found that in early onset of AD,the expression of miR-9 was up-regulated,while downregulated to lower than normal level in late stage of AD,providing insight for the genetic basis of Alzheimer's disease.In the second work,we for the first time successfully prepared a novel FLIM nanosensor based on carbon quantum dots and block polymers to simultaneously quantify ATG4 B and Caspase 3 and further monitor autophagy and apoptosis in neurons and brain tissue.This two-photon FLIM nanosensor exhibited excellent accuracy and selectivity,high spatial and temporal resolution,and long-term stability,with detection limits up to 8.21 and 4.39 pM for ATG4 B and Caspase 3.It was revealed that when neurons changes from normal state to the early apoptosis stage induced by A? oligomer,autophagy was induced by neuron apoptosis.At this time,appropriate induction of autophagy can inhibit neuron apoptosis,while excessive induction of autophagy could accelerate the process of apoptosis.However,in the late stage of apoptosis,upregulation of apoptosis inhibited autophagy,and the apoptosis that neurons went was severe,independent,and was no longer affected by autophagy.These findings provide a way to understand the signaling pathway between ad-related autophagy and apoptosis.