Phosphorescent probes for in vivo two-photon microscopy of oxygen
Tatiana Esipova, University of Pennsylvania
The ability to quantify oxygen in vivo in 3D with high spatial and temporal resolution is invaluable for understanding of oxygen metabolism, delivery and consumption in normal and diseased tissues. An optical method based on oxygen-dependent quenching of phosphorescence is being developed, that allows quantitative minimally invasive real-time imaging of partial pressure of oxygen (pO2) in tissue.
In the past, dendritically protected phosphorescent oxygen probes with controllable quenching parameters and defined bio-distributions have been developed , and more recently our probe design strategy has been expanded on two-photon excitable oxygen probes . These latter molecules comprise FRET-based antenna-core constructs, which brought about first demonstrations of two-photon phosphorescence lifetime microscopy (2PLM) of oxygen in vivo, providing new valuable information for neuroscience [3-6] and stem cell biology . However, current two-photon oxygen probes suffer from a number of limitations, such as low brightness and high cost of synthesis, which dramatically reduce imaging performance and limit usability of the method.
Here we present an approach to new bright phosphorescent chromophores with internally enhanced two-photon absorption cross-sections, which allow construction of antenna-free probes for 2PLM. In addition to substantial increase in performance, the new probes can be synthesized by much more efficient methods, thereby greatly reducing the cost of synthesis.
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