Novel fluorescent probes for highly selective two-photon imaging of mitochondria in living cells

The synthesis and characterization of a pair of novel pyridine cation derivatives possessing two-photon excitation fluorescence (TPEF) properties and selectively staining mitochondria in living SiHa cells within 30 min, CAI and CAEI, were reported. And the green-emitting CAI displayed a much larger two-photon excitation fluorescence action absorption cross-section (delta x Phi) of 328 g at 860 nm in comparison with commercial MitoTracker Green (MTG) with maximum delta x Phi value of 2.18 g at 850 nm. As is known to all, delta x Phi is a crucial parameter to obtain a high-quality microscopic photo in living cells in two-photon microscopy (TPM). Moreover, the fact that the co-localization coefficient between CAI and conventional MitoTracker Red (MTR) was 0.95 in SiHa cells demonstrated specific staining performance of CAI to mitochondria. As biosensors, both CAI and CAEI possessed a number of beneficial properties such as large delta x Phi and Stokes shifts, good membrane permeability, long retention time, high photostability and excellent counterstain compatibility with different biosensors for instance Hoechst 33342 and D 307, which ranked them as one of the best TPEF mitochondrial probes. Furthermore, related mechanism research suggested that their localization properties were dependent on the mitochondria] membrane potential in living cells. And their remarkable properties can extend the investigation on mitochondria in a biological context. (C) 2013 Elsevier B.V. All rights reserved.