Fluorogenic-Antioxidants: Novel Probes for Visualizing Reactive Oxygen Species in the Lipid Membranes of Live Cells

Abstract

We are pioneering the preparation of lipophilic fluorogenic antioxidant probes for the specific imaging of ROS in the membrane of live cells. Our strategy involves synthesizing a two segment receptor-reporter type free radical scavenger-fluorophore probe (an off-on fluorescent antioxidant indicator). The receptor segment in the probe mimics the structure and activity of the naturally occurring antioxidant α-tocopherol. A covalently tethered bodipy fluorophore serves the purpose of reporting, via emission enhancement, structural changes at the receptor end which result from the radical scavenging activity of the receptor.Here we will present our most recent results involving the preparation of a second generation set of probes relying on newly synthesized bodipy dyes with improved redox properties. The new fluorogenic antioxidant probes undergo a 30 fold fluorescence enhancement upon reaction with peroxyl radicals in model lipid membranes. We will also illustrate a high-throughput fluorescence method enabled by the new probes, for the rapid determination of relative rates of free radical scavenging by α-tocopherol analogues. Rates are evaluated for tocopherol analogues with a modified lipophilic tail, when embedded in liposomes prepared from either unsaturated or saturated lipids, upon exposure to either hydrophilic or lipophilic peroxyl radicals. This work provides new insights and a quantitative understanding on the critical role of lipid diversity in modulating chemical reactions in the lipid milieu. Finally studies will be described where we utilize these new probes to image ROS in the lipid membrane of live cells.