Synthesis, photophysical study and BSA association of water-insoluble squaraine dyes

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 2013-01, Vol.252, p.77-83
• Main Authors: Pisoni, Diego dos Santos, de Abreu, Marluza Pereira, Petzhold, Cesar Liberato, Rodembusch, Fabiano Severo, Campo, Leandra Franciscato
• Format: Article
• Language: English
• Subjects: BSA association; Photophysical characterisation; Squaraine dyes
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2012.11.013

[Display omitted] ► Three water-insoluble squaraine dyes based on indoleninium and benzothiazolium moieties were synthesised. ► The dyes presented intense absorption and fluorescence emission in the red region. ► In the phosphate buffer solution and absence of bovine serum albumin the squaraine dyes were almost nonfluorescent. ► The fluorescence intensities of the dyes increased with addition of protein in the buffer/dye solutions. In this work, the synthesis, spectroscopic characterisation, photophysical study and bovine serum albumin association of water-insoluble squaraine dyes are described. The photophysical behaviour of the dyes was investigated using UV–vis and steady-state fluorescence in solution, as well as its association with bovine serum albumin in phosphate buffer solution. No squaraine aggregation was observed in organic solvents, but a J-type aggregation could be observed in phosphate buffer solution. In the absence of protein, the J-aggregation promoted the fluorescence quenching; however, upon addition of protein, the fluorescence intensity increased by a factor of up to 80. Additionally, a linear relationship between the fluorescence intensity and the protein concentration could be observed for the squaraine dyes in a concentration range around 0.02–0.10μM.