Real-Time 3D Imaging and Inhibition Analysis of Various Amyloid Aggregations Using Quantum Dots

Abstract

Amyloidosis refers to aggregates of protein that accumulate and are deposited as amyloid fibrils into plaques. When these are detected in organs, they are the main hallmark of Alzheimer’s disease, Parkinson’s disease, and other related diseases. Recent medical advances have shown that many precursors and proteins can induce amyloidosis even though the mechanism of amyloid aggregation and the relationship of these proteins to amyloidosis remains mostly unclear. In this study, we report the real-time 3D-imaging and inhibition analysis of amyloid β (Aβ), tau, and α-synuclein aggregation utilizing the affinity between quantum dots (QD) and amyloid aggregates. We successfully visualized these amyloid aggregations in real-time using fluorescence microscopy and confocal microscopy simply by adding commercially available QD. The observation by transmission electron microscopy (TEM) showed that QD particles bound to all amyloid fibrils. The 3D-imaging with QD revealed differences between amyloid aggregates composed of different amyloid peptides that could not be detected by TEM. We were also able to quantify the inhibition activities of these proteins by rosmarinic acid, which has high activity for Aβ aggregation, from fluorescence micrographs as half-maximal effective concentrations. These imaging techniques with QD serve as quick, easy, and powerful tools to understand amyloidosis and to discover drugs for therapies.

Dietary Intake of Rosmarinic Acid Increases Serum Inhibitory Activity in Amyloid A Aggregation and Suppresses Deposition in the Organs of Mice

“…In this study, we used recombinant mouse SAA 1.1 (mSAA) protein to create an image of amyloid aggregation using QDs [ 36 , 39 ]. Long-term inflammation has this complication, and is best characterized by the SAA 1 genotype.…”

“…Long-term inflammation has this complication, and is best characterized by the SAA 1 genotype. We semi-quantified the amount of amyloid aggregates from the standard deviation (SD) of the brightness of each pixel in fluorescence microscopic images according to the methodology employed in previous studies [ 27 , 28 , 30 , 36 ]. In this method, the concentration of amyloid protein having a peak SD value is the optimum concentration for evaluating aggregation inhibitory activity.…”

“…Aggregates were observed after 2 h of incubation, increasing over time ( Figure 1 A). Figure 1 B plots the amount of aggregates estimated from the SD of the brightness of each pixel of a fluorescence microscope image [ 28 , 36 ]. Under similar conditions, Aβ began to aggregate at around 5 h [ 34 ], suggesting that the lag time of SAA aggregation is shorter than that of Aβ.…”

“…It was subsequently reported that Aβ plaque deposition in RA-fed mice was reduced [ 33 ]. RA also shows high antioxidant activity, and antioxidants with a catechol moiety inhibited the aggregation of various amyloid proteins such as Aβ, tau, and α-synuclein [ 34 , 35 , 36 , 37 ].…”

Amyloid‐Mediated Fabrication of Organic–Inorganic Hybrid Materials and Their Biomedical Applications

“…In addition, another important research direction is the use of QDs to detect the formation of amyloid fibrils by fluorescent testing. [72][73][74] For example, Quan et al developed a nanoprobe consisting of a red-emitting fluorescent QD core encapsulated in a PEGylated shell with benzotriazole (BTA) on the surface (QD-PEG-BTA). [75] BTA is able to target to the β2 position of the Aβ fibers with high affinity, enabling the QD-PEG-BTA to detect amyloid fibrils sensitively.…”