Organic fluorescent switches are fluorophores with potential for distinguishable, and occasionally reversible, changes in their emission intensity or wavelength. For intensity-based sensors, these states can be interpreted as “ON” and “OFF” modes of fluorescence, and the OFF to ON activation of the emission can be triggered by exposure to rationally selected environmental stimuli, enabling emission with spatial (‘where’ fluorescence in activated) and temporal (‘when’) control. Activatable fluorescent probes thus have great potential for sensing or super-resolution imaging applications, however their hydrophobicity is a barrier for use in biology. Moreover, sensitivity of the probe to a target is also desirable vs. non-controlled activation of fluorescence. To overcome these challenges, we investigated the supramolecular confinement of a hydrophobic boron-dipyrromethene-2,2,6,6,tetramethylpiperidine-N-oxyl (BODIPY-TEMPO) activatable probe and the radical photoinitiator Irgacure-1173 (the ‘activator’). The paramagnetic TEMPO moiety quenches BODIPY fluorescence through electron exchange; mild UVA irradiation causes Irgacure-1173 to generates radicals which are then scavenged by TEMPO, suppressing the quenching pathway and restoring BODIPY fluorescence. Encapsulating this pair of organic molecules in a self-assembling polymer micelle aims to address both aqueous solubility and controlled activation concerns by: 1. Capturing the pair in the internal hydrophobic pore, meanwhile ensuring solubility in physiological buffer and biocompatibility through external hydrophilic polymer side-chains; 2. Isolating the switch from endogenous biological radicals (toward which TEMPO is sensitive), enabling activation only upon user-initiated ultraviolet irradiation. Our goal is to investigate the viability of assembling this supramolecular system, and to explore its optical properties, including fluorescence activation and ON-OFF cyclability, for super-resolution microscopy.

Supramolecular confinement of photogenerated radical initiated fluorescence

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.