Natural Macromolecule Fluorescence-responsive Nanomaterials That Simultaneously Diagnose And Inhibit β-Amyloid Protein Aggregation

The aggregation ofβ-amyloid（Aβ）protein is closely related to the etiology of Alzheimer’s disease（AD）.Except for the inhibition of Aβaggregates formation,accurate detection of Aβaggregates is also essential for the early diagnosis and treatment of AD.However,most of the current nano-drugs do not have the capability of inhibiting and detecting Aβspecies at the same time,and some of them are confronted with defects of poor biocompatibility,high cytotoxicity,and fluorescence quenching in enrichment state.To overcome the above drawbacks and achieve the purpose of"integration of diagnosis and treatment"targeting Aβaggregates,a kind of multifunctional nanoparticles was successfully synthesized as a theranostic agent.The self-assembly between two natural macromolecules,chitosan and hyaluronic acid,was first formed through the electrostatic interaction,then the glutaraldehyde was added to react with amino groups,thereby generating the Glutaraldehyde-hyaluronic acid-glutaraldehyde nanoparticles（CHG NPs）which contain a large number of pyridine ring structure and electron-rich atoms（N,O）.In this study,dynamic light scattering instrument,transmission electron microscope,infrared spectrometer and fluorescence spectrophotometer were used to characterize CHG NPs.Thioflavin T（Th T）fluorescence method,fluorescence spectroscopy,circular dichroism spectroscopy,atomic force microscopy,inverted fluorescence microscopy and C.elegans experiments were used to determine the fluorescence detecting and inhibiting capabilities of CHG NPs for amyloidosis.The study showed that,the CHG NPs owed a uniform nano-spherical structure about 100nm and a great aggregation-induced emission characteristic.Under physiological p H conditions,CHG NPs could uniformly adsorb on Aβfibrils surface through electrostatic and hydrophobic interactions.This process increased the electron transfer between nanoparticles,thus enhancing the fluorescence intensity of CHG NPs.Therefore,the fluorescence detection of Aβ₄₀ oligomers and mature fibirls was successfully achieved.The results showed that the final fluorescence intensity of CHG NPs was in good positive correlation with the Aβ₄₀ oligomers/fibirls concentration,and the detection limit was 0.1 n M.Besides,CHG NPs could detect the amorphous products from the EGCG inhibition of Aβaggregation and the human islet amyloid polypeptide fibrils which show high similarity to Aβ.In addition,the CHG NPs did not respond to serum albumin,a common detection interferences present in the blood,exhibiting specificity for Aβoligomers and fibirls.Moreover,CHG NPs could effectively bind with Aβ₄₀ monomers to form stable complexes,limit the flexibility of Aβ₄₀ on the surface of NPs and affect its conformational transition,ultimately preventing the formation of Aβ₄₀ aggregates.The inhibitory effect was concentration-dependent;when the addition was 720μg/ml,CHG NPs could inhibit 91.50%of Aβ₄₀ aggregates formation(with an Aβ₄₀ concentration of 25μM).The abilities of CHG NPs to detect and inhibit the accumulation of Aβaggregates were further demonstrated with C.elegans assasy.In this study,a theranostic agent based on natural macromolecules was designed,which shows excellent biocompatibility as well as detecting and inhibiting capabilities targeting Aβspecies.It provides a new idea for the development of AD theranostic agents.