The Synthesis Of Functional Molybdenum Disulfide Quantum Dots And Their Inhibitory Effect On Protein Aggregation

Misfolding and aggregation of proteins can lead to fibrosis in the biological body,which can lead to the production of various amyloid diseases.Inhibition of protein aggregation and fibrosis is the main way to treat protein aggregation disease.Molybdenum disulfide quantum dots?MoS₂ QDs?is a novel zero-dimensional nanomaterials with good biocompatibility and the ability to penetrate cell membrane,which has potential applications prospect in inhibiting protein aggregation.However,research on this aspect has rarely been reported.Therefore,this study synthesized different functionalized MoS₂ QDs using cysteamine?CA?,glutathione?GSH?and 4-mercaptophenylboronic acid?MPBA?as modifiers,and bovine serum albumin?BSA?was used as an aggregation model in vitro.Then the inhibitory effect of different functionalized MoS₂ QDs on BSA fibrosis was studied.The results provide useful reference for the design and research of novel protein aggregation nano-inhibitors.The details are as follows:1.Construction of self-aggregation system of bovine serum albuminWe investigated the effects of different pH,temperature,and protein concentration on BSA amyloid fibrosis using ThT as a fluorescent probe and determined the experimental model BSA self-aggregation.Under the determined conditions,the changes of hydrophobic area exposure and?-sheet folding structure were detected by ANS fluorescence,CD spectroscopy and transmission electron microscopy?TEM?.The results showed that 40?M BSA was dissolved in 20 mM Tris-Hcl buffer solution at pH 7.4 and incubited for 8 h at 65?C to construct successfully an experimental model for the study of bovine serum albumin aggregation fibrosis.It laid a foundation for the subsequent experimental research.2.Effects of CA-MoS₂ QDs on bovine serum albumin fibrosis.In this chapter,CA-MoS₂ QDs were prepared by hydrothermal method using sodium molybdate as molybdenum source and cysteamine?CA?as sulfur source and functionalized molecule,and characterized by TEM,AFM,XPS,FT-IR,PL and UV-vis spectroscopy.Under the determined optimal aggregation conditions,the effects of CA-MoS₂ QDs on BSA fibrosis were studied.The results showed that CA-MoS₂ QDs could effectively inhibit the formation of fibrils in a concentration-dependent manner,and even at a mass ratio of 1:5,the inhibition rate of BSA aggregation could reach71.1%.At the same time,CA-MoS₂ QDs had strong depolymerization effect on BSA oligomers and fibers formed at different incubation times,which could achieve a depolymerization effect of 22.9%-39.0%.Thiazole blue?MTT?assay and cell imaging experiments showed that CA-MoS₂ QDs have good cell penetrating ability.At the concentration of 250?g�mL^-1,the cell survival rate was still above 90%.Moreover,it could effectively inhibit the cytotoxicity induced by BSA fibrils.3.Effects of GSH-MoS₂ QDs on bovine serum albumin fibrosis.This chapter used GSH as a functional molecule to synthesize GSH-MoS₂ QDs,and studied its effect on self-aggregation and pre-formed amyloid fibers of BSA.The results showed that GSH-MoS₂ QDs could not only effectively inhibit the formation of fibrils,but also depolymerize the pre-formed oligomers and fibrils of BSA.The inhibition and depolymerization effects were positively correlated with the concentration;the maximum inhibition rate was 84.1%,the depolymerization effect could achieve 29.0%-46.6%.After GSH-MoS₂ QDs co-incubated with BSA for 3hours,QDs were allowed to enter the cells.At a concentration of 250?g�mL^-1,the cell survival rate achieved 92%.Moreover,it could effectively inhibit the cytotoxicity induced by BSA fibrils.4.Effects of MPBA-MoS₂ QDs on bovine serum albumin fibrosis.This chapter synthesized MPBA-MoS₂ QDs with MPBA as functional molecules,and its effect on BSA amyloid fibrosis were studied.The results showed that MPBA-MoS₂ QDs not only can effectively inhibit the formation of fibrils,but also depolymerize the pre-formed oligomers and fibrils of BSA.The inhibition and depolymerization effects were positively correlated with the concentration;the optimal inhibition rate was 74.9%.the depolymerization effect could achieve 33.0%-55.9%.After MPBA-MoS₂ QDs co-incubated with BSA for 3 hours,QDs were allowed to enter the cells.At a concentration of 250?g�mL^-1,the cell survival rate achieved 90%.Moreover,it could effectively inhibit the cytotoxicity induced by BSA fibrils.5.Molecular docking study of functionalized MoS₂ QDs interacting with BSA.The molecular docking technique was used to simulate the binding mode and interaction force type of three functionalized molecules interacting with BSA,and the mechanism of functionalized MoS₂ QDs inhibiting BSA amyloid fibrosis was preliminarily explored at the molecular level.The results showed that L-cysteamine combined between the IIIA and IB domains of BSA and does not enter the hydrophobic cavity of BSA.Glutathione and 4-mercaptophenylboronic acid were bound in the hydrophobic cavity of III A.The interaction between the three small molecules and BSA is glutathione>4-mercaptophenylboronic acid>L-cysteamine.Corresponding to the previous spectral experiment inhibition results,and they complement each other.L-cysteine forms a hydrogen bond with the amino acid residue of the BSA active site,and electrostatic interaction dominates in the interaction;electrostatic interaction and hydrophobic interaction dominantly occured in the interaction of glutathione,4-mercaptophenylboronic acid and BSA,and a hydrogen bond and van der Waals force are formed between the amino acid residues of the BSA active site;the benzene ring of4-mercaptophenylboronic acid forms?-?conjugate with VAL481 of BSA.These forces can maintain the stability of the BSA conformation,thereby achieving the purpose of inhibiting BSA aggregation.