HSA-based phosphorescent probe for two-photon in vitro visualization

• HSA adduct with Au-Ag alkynyl-diphosphine complex shows δTPA up to 1300 GM at 740 nm.
• Human serum albumin-based phosphorescent probe for two-photon in vitro visualization.
• Novel non-covalent HSA adduct shows superior two-photon absorption in NIR region.
• Novel phosphorescent non-covalent HSA adduct for 3D tissue visualization.

Two-photon microscopy reveals several advantages over conventional one since it provides higher spatial resolution as well as deeper penetration into the sample under study. The development of suitable two-photon probes is one of the most challenging tasks in this area. Here we present phosphorescent non-covalent adduct of human serum albumin and Au-Ag alkynyl-diphosphine complex, [Au14Ag4(C2Ph)12(PPh2C6H4PPh2)6][PF6]4, which exhibits high cross section of two-photon-induced luminescence (δTPE) within large near-infrared excitation wavelength region (700–800 nm) with maximum δTPE about 38 GM at 740 nm. This feature makes it a promising probe for multiphoton bioimaging as demonstrated by successful visualization of glioma C6 cells and various tissues by two-photon confocal microscopy both in planar and z-stacking modes. Additionally, the broad excitation region enables optimization of the signal-to-background auto-fluorescence ratio via variation of excitation wavelength.

Novel phosphorescent non-covalent HSA adduct for 3D tissue visualizationFigure optionsDownload as PowerPoint slide