Rapid Fluorescence Imaging And Analysis Of Alzheimer's Disease

Alzheimer's disease(AD)is a multi-factorial and irreversible neurodegenerative disorder.At present,there is still no effective way for early diagnosis and treatment of Alzheimer's disease,and it has become the major disease following cardiopathy and cancer.Alzheimer's disease exerted great influence on family and society as a global health problem.It is also a difficult problem for the current international medicine.If it can be diagnosed at a very early stage,followed by treatment at the early stage,the Alzheimer's patient's quality of life and rate of survival might be significantly improved.Therefore,early diagnosis should play a vital role in treating and prevention of this disease.However,there lack of high sensitive detection methods.Fluorescent nanoclusters have great potential applications in optical imaging for their good properties such as ultra small size,good biocompatibility and strong fluorescence emission etc.Our recent research illustrates that biosynthesized fluorescent nanoclusters(NCs)like gold,silver and zinc NCs could be readily utilized as a great potential probe for highly sensitive optical imaging of oxidative stress linked pathologies such as cancers,and then reduced the further development of tumors.Fluorescence imaging has many advantages such as noninvasive,high selectivity,high sensitivity,real-time monitoring,strong fluorescence signal and low cost etc.It plays an important role in revealing the basic rule of life activities and monitoring the main physiological and biochemical process in vivo.Therefore,it has received a great deal of attention in academic world.By investigating researchs on the Alzheimer's disease,fluorescent imaging for early and rapid targeting diagnosis of Alzheimer's disease are rarely reported currently.Alzheimer's disease involves formation of numerous senile plaques(SPs)composed of?-amyloid(A?)peptides,various redox-active metal ions,different kinds of reactive oxygen specie(ROS)and inflammatory reaction which leading to a completely different redox environment in the brain of Alzheimer's patients compared with the normal brain.In view of these considerations,in this study,we take various reagents inclouding precious metal ions and transition metal ions with excellent biocompatibility to realize rapid,sensitive and targeting bio-marking of relevant lesion of Alzheimer's disease through in situ synthesis of functional nanoclusters.Besides,these methods are simple,convenient and feasible,having a broad application prospect in diagnosis of Alzheimer's disease.The main contributions of this dissertation are summarized as follows:We have explored a new strategy of in vivo rapid fluorescence bio-imaging of Alzheimer 's disease through target bio-labeling of the diseased sites.The sites are exposed to aqueous solutions of chloroauric acid(HAuCl4)which subsequently forms Au salts.These salts then self-assemble to gold nanoclusters(Au NCs)which can then be used for fluorescence imaging.For instance,taking Alzheimer's model mice(AD)and a normal control group of mice(NOR)as models,our studies demonstrate that intravenous injection of aqueous AuCl4-through the AD mice tails allowed accurate bright fluorescence labeling around the affected sites of the Alzheimer's brain within a couple of hours,while this did not in normal mice(controls):The control mice did not exhibit any fluorescent areas even 24 h after intravenous injection of an identical or larger amount of aqueous AuCl-.These observations suggest that AuCl4-ions could readily pass through the blood-brain barrier(BBB)of the AD mice and then mainly accumulate on the hippocampus specific region followed by in situ biosynthesis of the Au NCs for fluorescent labeling of the affected sites of Alzheimer's brain.This strategy provides a new way for the rapid and early diagnosis of Alzheimer's disease and may have potential for effective theranostics of Alzheimer's disease.We have successfully explored another new strategy of in vivo rapid fluorescence imaging of Alzheimer's disease through target bio-labeling of zinc oxide nanoclusters which was biosynthesized in vivo in the Alzheimer's brain via intravenous injection of 0.3 mL 5 mmol/L zinc gluconate solution.As we known,zinc is one of the essential trace elements in the human body,which is closely related to a variety of physiological processes and has extremely important biological functions in vivo,including nervous system,body immunity,growth and development,metabolic system,etc.zinc gluconate is an ideal organic zinc supplements with good biological compatibility and high bioavailability.By using the three-month-old and six-month-old Alzheimer's model mice as models,our observations demonstrate that biocompatible zinc ions could pass through the blood-brain barrier of the Alzheimer's disease mice and generate fluorescent zinc oxide nanoclusters(ZnO NCs)through biosynthesis,and then the bio-synthesized ZnO NCs could readily accumulate in situ on the hippocampus specific region for in vivo fluorescent labeling of the affected sites.This study provides a new way for the rapid and high sensitive diagnosis of Alzheimer's disease and may have promising prospects in effective diagnose of Alzheimer's disease.Our research results provide a new promising strategy for the rapid and early dual-modality bio-imaging(i.e.,including fluorescence bio-imaging(FL)and magnetic resonance imaging(MRI))of Alzheimer's disease for the first time by biosynthesizing the fluorescent zinc oxide nanoclusters and magnetic iron oxide nanoclusters,respectively,in the lesions area of the AD model mice.Zinc and iron are essential trace elements for human and animal body.Both of them have many important physiological functions.Iron is the most abundant trace element in human body.It participates in many life processes and widely distributes in various tissues and organs.It is the necessary component not only for oxygen transport protein and electron transfer protein,but also for many enzymes cofactors.Many iron nanoparticles(eg.?-Fe2O3,Fe3O4 and FePt etc.),as the advanced contrast agents to shorten imaging time and increase image contrast and resolution,have been widely used in many fields especially in biomedicine such as MRI,drug targeting transport and diagnosis of cancer.We have demonstrated that both zinc gluconate solution and FeCl2 solution could readily biosynthesized the fluorescent zinc oxide nanoclusters and magnetic iron oxide nanoclusters,respectively,in the lesions area of the AD model mice,and thus enable fluorescence and MRI dual-modality bio-imaging of Alzheimer's disease.Based on the special redox environment in the brain of Alzheimer's patients,in this study,we take precious metal ions and transition metal ions to realize rapid and targeting bio-marking of the relevant lesion of Alzheimer's disease through in situ synthesis of functional nanoclusters,which shows an important research value and broad application prospect in diagnosis of Alzheimer's disease.