Aza-BODIPY: Improved synthesis and interaction with soluble Aβ1–42 oligomers

Abstract

Dye-binding assays that are used to evaluate anti-aggregation ability of small molecule inhibitors towards amyloids are known to be prone to false-positive effects due to spectral overlaps between the dye and the inhibitor. Aza-BODIPY dye, which has both excitation and emission maxima above 600 nm, exhibits a significant increase in its fluorescence intensity in the presence of soluble oligomers of Aβ1-42. These results indicate that aza-BODIPY could serve as a near-IR probe for detecting conformational changes of Aβ1-42 soluble oligomers in vitro, and it should eliminate false-positive effects that are associated with currently utilized thioflavin T-based dyes. In addition, a facile synthesis of aza-BODIPY has been developed, which might further expand the applications of this dye.

Naphthyridyl‐Substituted 4,4‐Difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) Luminophores: Photophysics and Application as Molecular Imaging Probes in Live Cells

“…Compound 15 was dissolved in N,N-dimethylformamide (DMF; 0.5 mL) with O-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU; 1.3 equivalents) and stirred for 20 min. Amino-(PEG) 15 (1.3 equivalents) in DMF was added followed by DIPEA (5 equivalents). The solution was then stirred for 24 h, which was followed by purification on silica gel by elution with CH 2 Cl 2 /MeOH (9:1) to yield 16 as a dark purple material (35 %).…”

“…This versatile active ester is valuable across a range of applications, most notably as a biological conjugate. The synthesis of 14 was then achieved by treating 10 with amino-(PEG) 15 in the presence of N,N-diisopropylethylamine (DIPEA; 5 equivalents) in CH 2 Cl 2 /MeCN (3:1) with stirring for 2 h (TLC). The removal of the solvent in vacuo was followed by purification by flash column chromatography using an eluent system of CH 2 Cl 2 /MeOH (9:1) to yield a viscous red/orange material, 14 (44 %).…”

“…Correspondingly, there has been significant effort invested in the successful development of BODIPY derivatives with red and NIR emission. [15,[32][33][34][35][36][37][38] Finally, water solubility is a requirement of any biological probe, and the majority of BODIPY derivatives are insoluble in water. In many imaging applications this is overcome by dissolving the fluorophore first in a solution of ethanol or dimethylsulfoxide (DMSO) and then introducing the predissolved dye into the buffer or cell culture media.…”

Chemical Fluorescent Probe for Detection of Aβ Oligomers

“…One of the reported oligomer-specific fluorescence sensors showed the capability of distinguishing soluble Aβ from Aβ of ordered conformation but fell short of discriminating oligomers from fibrils and lack demonstration of biological application capabilities. 15,16 …”

Real‐Time BODIPY‐Binding Assay To Screen Inhibitors of the Early Oligomerization Process of Aβ1–42 Peptide

“…[15] Consequently,t he improvement of fluorescent probest os pecifically detect oligomersi sh ighly relevant and, in particular,t he development of new screening assays specific for the early oligomerization process is of high current interest. [16][17][18][19][20] Herein, we report the development of an ew real-time 96well plate assay based on aB ODIPY dye that is applicable to screena nd discover new inhibitors of early Ab1-42 oligomerization, which fail to be discovered in the typical ThT assay.T he employed BODIPYd ye, containing at riazole moiety (Figure 1A), is as uitable probe for protein hydrophobicity and amyloid conformational transitions, even at al ow dye concentration( 0.53 mm). [16] The BODIPY real-time 96-well plate assay combines high sensitivity towards Ab1-42 soluble oligomers and statistical robustness of the kinetics curve obtained under oligomerization conditions.…”