Dendritic phosphorescent probes for oxygen imaging in biological systems

Area of Science:

• Biomedical Engineering
• Materials Science
• Analytical Chemistry

Background:

• Accurate measurement of oxygen levels (pO(2)) is crucial for understanding biological processes.
• Phosphorescence quenching offers a sensitive method for oxygen sensing.
• Existing probes often lack tunable parameters and biocompatibility for in vivo applications.

Purpose of the Study:

• To develop a general approach for constructing phosphorescent nanosensors with controllable properties.
• To create probes with tunable spectral characteristics, variable quenching sensitivity, and high oxygen selectivity.
• To demonstrate the utility of these nanosensors for in vivo oxygen imaging.

Main Methods:

• Synthesis of phosphorescent probes based on Pt and Pd complexes of porphyrins and pi-extended porphyrins.
• Encapsulation of metalloporphyrins into poly(arylglycine) dendrimers to control oxygen diffusion.
• Modification of dendrimer periphery with poly(ethylene glycol) for enhanced solubility and biocompatibility.
• Characterization of probe parameters under physiological conditions, including stability in biological environments.

Main Results:

• Developed nanosensors with tunable spectral properties via pi-extension of porphyrin macrocycles.
• Achieved controllable sensitivity and dynamic range by regulating oxygen diffusion through dendrimer encapsulation.
• Demonstrated enhanced solubility, reduced toxicity, and minimal interaction with biomacromolecules due to PEGylation.
• Successfully applied the probes for in vivo microscopy of vascular pO(2) in the rat brain.

Conclusions:

• The developed phosphorescent nanosensors provide a versatile platform for accurate biological oxygen measurement.
• Tunable spectral characteristics and controlled sensitivity make these probes suitable for diverse imaging modalities.
• The biocompatible and stable nature of the nanosensors enables reliable in vivo applications, such as brain imaging.