Self-Reporting Conjugated Polymer Nanoparticles for Superoxide Generation and Detection

Area of Science:

• Nanotechnology
• Materials Science
• Photochemistry

Background:

• Conjugated polymer nanoparticles (CPNs) are popular fluorophores for multimodal imaging and phototherapy.
• CPN applications often focus on singlet oxygen generation, but superoxide formation can degrade fluorescence.

Purpose of the Study:

• To demonstrate that poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1',3}-thiadiazole)] (PFBT) CPNs generate superoxide upon irradiation.
• To develop a CPN-based method for detecting superoxide using a hydrocyanine dye.

Main Methods:

• Irradiation of PFBT CPNs to induce superoxide generation.
• Doping PFBT CPNs with a superoxide-responsive hydrocyanine dye.
• Monitoring fluorescence changes via fluorescence resonance energy transfer (FRET) upon superoxide interaction.

Main Results:

• PFBT CPNs generate superoxide upon irradiation.
• Superoxide induces an "off-to-on" fluorescence switch by converting quenching hydrocyanine dyes to fluorescent FRET acceptors.
• Amplified FRET signals up to 50-100 times greater than direct excitation were observed.
• Dye loading influences superoxide generation rate and the extent of fluorescence change.

Conclusions:

• CPNs can be utilized to deliver superoxide for specific applications.
• This study provides a caution for fluorescence-based CPN applications due to potential fluorophore damage by superoxide.
• The developed method offers highly sensitive superoxide detection using CPNs.