A red-emissive tripodal nanoprobe for the discrimination of serum albumin with conformational change from Y- to ω-like and probing mitochondrial viscosity

Serum albumins, such as bovine serum albumin (BSA) and human serum albumin (HSA), play a crucial role in various biological processes. Discrimination between BSA and HSA is challenging due to their similar structures and reactivity. Here, we report mitochondria-targeted red fluorescent tripodal nanoprobe DMAS-TP, forming spherical nano-aggregates (∼90 nm) in water for discrimination of BSA over HSA and detection and imaging of viscosity in HeLa cells. DMAS-TP exhibits an ∼56-fold fluorescence intensity increase in 95% glycerol compared to water, which indicates restricted movement in high-viscosity solvents. Furthermore, the addition of 5 equiv. BSA and HSA to DMAS-TP solution displays ∼50-fold and ∼10-fold fluorescence intensity increases at 630 nm (λex 490 nm), respectively, and can detect as low as 20 nM BSA and 140 nM HSA. The fluorescence anisotropy plot shows that the DMAS-TP anisotropy values decrease from 0.234 to 0.185 with increasing [BSA/HSA], suggesting a conformational change from Y- to ω-like structure. The fluorescence lifetime of DMAS-TP increases gradually with BSA/HSA, suggesting dynamic complexation. DMAS-TP aggregates diminish to 6 nm particles when encapsulated in BSA confirmed by DLS, SEM, and TEM, with reduced fluorescence intensity in the presence of bilirubin, indicating that DMAS-TP binds within the BSA cavity near site IB. DMAS-TP is highly permeable to HeLa cells and shows a strong affinity for mitochondria, making it suitable for imaging viscosity and BSA via strong fluorescence in the red channel.

Synthesis, and the optical and electrochemical properties of a series of push–pull dyes based on the 4-(9-ethyl-9H-carbazol-3-yl)-4-phenylbuta-1,3-dienyl donor

A series of twelve dyes based on the 4-(9-ethyl-9H-carbazol-3-yl)-4-phenylbuta-1,3-dienyl donor were prepared with electron acceptors varying in their structures but also in their electron-withdrawing ability.