Analysis Of Relative Species In The Alzheimer's Diseases Based On Raman Spectroscopy And Polarized Light Microscopy

Alzheimer's Disease is a neurodegenerative disease,which afflicts about 30million people worldwide,and the number of the patients is going to increase rapidly in the future.Clinically,the disease is characterized by mild memory loss in the early stages,then gradually develop into severe cognitive impairment and loss of life ability.According to the research,many features were found in the brains of people with Alzheimer's,the main of which are two morphological hallmarks:the intracellular neurofibrillary tangles and the extracellular amyloid plaques?or senile plaques?.What's more,other related symptoms also appear in Alzheimer's patients,such as the oxidative modification of the biological molecules of the brain,impaired glucose tolerance,metal ions imbalance in the body,especially calcium,iron,copper and zinc.However,there is no clear understanding of the pathology of Alzheimer's disease,and also no effective treatment.In this paper,using Raman spectroscopy combined with polarized light microscope,nitric oxide?NO?and amyloid beta?A??,which are closely linked to Alzheimer's disease are studied and analyzed.In the first work,a ratiometric SERS probe was designed and created for determination of NO with high sensitivity,selectivity and accuracy,and was further applied in imaging and biosensing of NO in live cells.Firstly,a novel organic compound 3,4-diaminobenzene-thiol?DABT?was designed and synthesized.This molecule consists of two parts:one is o-phenylenediamine group for specifically recognizing NO to generate benzotriazole,another is thiol group for immobilizing DABT molecule onto gold nanostructures through a strong Au-S covalent bond.Secondly,for enhancing the sensitivity of SERS signal,trisoctahedral gold nanocrystals?AuHT?were synthesized as an effective SERS substrate.Then in the SERS experiment,the peak intensity I₆₉₈/I₉₇₄ shows a good linearity with the concentration of NO in the range from 54 n M to 918 nM.Also,the established probe demonstrated high selectivity against other reactive oxygen species?ROS?,reactive nitrogen species?RNS?and metal ions.The MTT assay further indicated the probe have low toxicity towards cells.The remarkable analytical performance of the present SERS probe,together with good biocompatibility and long-time stability,enabled real-time monitoring of the NO level in live cells.Then in the second work,combined with surface enhanced Raman spectroscopy and polarized light microscope,the aggregation state of A?1-16 was studied.First of all,using the atom force microscope,the morphology of A?_1-16 monomers,fibrils together with the sample added Cu²⁺were observed.Then the structure of A?_1-16 monomers,fibrils together with the sample added Cu²⁺were analyzed using surface enhanced Raman spectroscopy.Furthermore,we find the experiment conditions which can ensure the growth of A?-16 spherulite.Also,using the polarized light microscope,the growth rates of A?-16 spherulite and the spherulite sample added Cu²⁺were calculated and analyzed.