Biological oxygen sensing via two-photon absorption by an Ir(III) complex using a femtosecond fiber laser

Abstract

Near-infrared two-photon absorption of the phosphorescent Ir(III) complex (2,4-pentanedionato-κO 2,κO 4)bis[2-(6-phenanthridinyl-κN)benzo[b]thien-3-yl-κC]iridium (BTPHSA) was characterized. It exhibited a 800–1200 nm two-photon absorption band, and thus could be electronically excited by 1030-nm femtosecond Ti:sapphire and Yb-doped fiber lasers. By using BTPHSA, oxygen concentrations in human embryonic kidney 293 (HEK293) cells were imaged. These results demonstrate two-photon oxygen sensing of live tissues via easily operable excitation sources.

Two-photon absorption properties of simple neutral Ir(iii) complexes

“…This value is four times higher than that reported for 4-(para-di-nbutylaminostyryl)pyridine (190 GM), demonstrating how s (2) can be highly enhanced upon coordination to the Ir metal centre. Some examples of neutral iridium(III) complexes with TPA properties and direct application in vivo were also reported by the Kawamata 11 and Monnereau groups. 12 The investigated complexes exhibit TPA in the near-infrared, at wavelengths suitable for biological applications, with TPA crosssection values quite low (around 20-40 GM) but sufficient to allow recognition of two-photon induced emission in cells.…”

Simultaneous visualization of flow fields and oxygen concentrations to unravel transport and metabolic processes in biological systems

“…This limitation can be overcome by using O 2 -sensitive dyes, which are excited in the deep red or near-infrared range and thereby avoid autofluorescence spillover from photopigments (e.g., Niedermair et al., 2010 ). If information on O 2 concentrations within the tissue are of interest, confocal laser scanning microscopy or two-photon phosphorescence lifetime microscopy may be a powerful alternative to sensPIV (see, e.g., Shen et al., 2018 and Moritomo et al., 2016 ). Finally, during the synthesis of sensor particles, the amount of dye embedded within individual sensor particles can vary.…”

Shining New Light on Biological Systems: Luminescent Transition Metal Complexes for Bioimaging and Biosensing Applications

“…Additionally, the complex shows TPA across 800−1,200 nm, rendering it compatible with two-photon excitation using a femtosecond Yb-doped fiber laser operating at 1,030 nm. 1181 Huang, Gao, and co-workers have encapsulated the complex within the hydrophobic pocket of β-CD labeled with cyanine 7 to construct a ratiometric O 2 probe. 1182 The probe not only allows quantitative measurement of O 2 levels in live cells and in vivo but also noninvasive mapping of the hypoxia microenvironment of solid tumors.…”

“…This complex can image tumors located 6–7 mm below the surface of the abdominal skin. Additionally, the complex shows TPA across 800–1,200 nm, rendering it compatible with two-photon excitation using a femtosecond Yb-doped fiber laser operating at 1,030 nm . Huang, Gao, and co-workers have encapsulated the complex within the hydrophobic pocket of β-CD labeled with cyanine 7 to construct a ratiometric O 2 probe .…”