Desenvolvimento de novos sensores de ph fluorescentes derivados do borodipirrometeno (bodipy) visando aplicação em biologia celular

Abstract

Fluorescent pH sensors are an important tool to monitor several processes in living cells. However, the development of new sensors with optimized photphysical properties is still necessary. In view of BODIPY’s favorable photophysical features and their chemical versatility, these probes are widely used for the development of these sensors. However, many of these developed sensors are based on less affordable methylated pyrrolic starting materials. Therefore, in this work we propose to characterize the spectroscopic properties of three groups of non-methylated BODIPYs functionalized in position 3 as pH sensors – 3-benzylamino, 3-(pyridin-3-yl) and 3 (4- aminophenyl) BODIPYs – and explore its application in cellular biology. For this purpose, fluorimetric and spectroscopic titrations were performed, and, through sigmoidal curve adjustments, the pKa was determined. To explore the application in cellular biology, a MTT assay was performed for compounds that showed sensitivity to pH. Two of the investigated compounds, those with benzylamino in position 3 as the recognition site (compounds 2 and 5), showed red-shifted emission with a ratiometric change, low cytotoxicity, and an applicable pH range of 3.6 to 5.7, suggesting a possible useful application as lysosomal sensors. The sensing mechanism was investigated and possible intramolecular charge transfer state (ICT) was inferred a for these compounds. Two other compounds showed fluorescence change with the pH, the 3-(4-aminophenyl) BODIPYs (compounds 14 and 15), which presented an OFF/ON application in a more acidic range, from pH 1.5 to 4.5. Through spectral properties and theoretical calculations, it was assumed that the fluorescence quenching was due to PET reactions. Microscopy analysis are in progress for compounds that exhibit pH sensitivity and are part of the continuation of this project.