Red-emitting Styryl-BODIPY dye with donor-π-acceptor architecture: Selective interaction with serum albumin via disaggregation-induced emission

Abstract

Serum albumin (SA) is an abundant protein in mammalian blood plasma and a biomarker for various diseases, such as cirrhosis or hepatitis in the case of the liver. The research of fluorescent probes for SA based on host-guest interactions provides an opportunity to study the nature of intermolecular interactions and thus reveals the structure information of SA at the molecular level. However, some commercially available fluorescent probes, such as boron dipyrromethenes (BODIPYs) have a general tendency to form aggregates under an aqueous environment, which is a drawback for their use due to the strong quenching of the emission. Additionally, short emission wavelength and small Stokes shift are the other common shortcomings. In this work, we explore this unfavourable property and provide an effective method for developing an “off-on” type probe for SA. A new probe named BOD-Red with red-emitting aggregation/disaggregation characters was then designed, consisting of donor-π-acceptor (D-π-A) architecture where boron-dipyrromethene (BODIPY) core as electron acceptor and N-phenylpiperazine as electron donor. The extended π-conjugation system provides not only the increase of emission wavelength due to the enhancement of intramolecular charge transfer strength, but also forms a higher rigid coplanar backbone, which can modulate the photophysical properties and aggregation process. Furthermore, the incorporated N-(2-hydroxyethyl) piperazine group behaves as a SA-binding receptor. BOD-Red formed aggregates in an aqueous solution and was non-emissive. In the presence of SA, it exhibited a pronounced enhancement of emission intensity centred at 630 nm owing to the disaggregation-induce emission. Notably, this probe in solution was non-responsive to any other tested proteins and small molecules. The mechanism responsible for the binding of BOD-Red with BSA was analyzed by a combined experimental and computational approach. The practical utility of BOD-Red as a fluorescent turn-on sensor was validated by quantifying BSA in real samples with reasonable recovery percentages.