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

The aggregation of?-amyloid(A?)protein is closely related to the etiology of Alzheimer's disease(AD).Except for the inhibition of A?aggregates formation,accurate detection of A?aggregates 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 A?species 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 A?aggregates,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 A?fibrils 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 A?₄₀ 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 A?₄₀ 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 A?aggregation and the human islet amyloid polypeptide fibrils which show high similarity to A?.In addition,the CHG NPs did not respond to serum albumin,a common detection interferences present in the blood,exhibiting specificity for A?oligomers and fibirls.Moreover,CHG NPs could effectively bind with A?₄₀ monomers to form stable complexes,limit the flexibility of A?₄₀ on the surface of NPs and affect its conformational transition,ultimately preventing the formation of A?₄₀ aggregates.The inhibitory effect was concentration-dependent;when the addition was 720?g/ml,CHG NPs could inhibit 91.50%of A?₄₀ aggregates formation(with an A?₄₀ concentration of 25?M).The abilities of CHG NPs to detect and inhibit the accumulation of A?aggregates 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 A?species.It provides a new idea for the development of AD theranostic agents.