A Small-Molecule Photoactivatable Optical Sensor of Transmembrane Potential

Area of Science:

• Neuroscience
• Biochemistry
• Optical Imaging

Background:

• Transmembrane potential is crucial for neuronal function.
• Existing voltage sensors have limitations in specificity and application.
• Photoactivatable probes offer potential for targeted optical measurements.

Purpose of the Study:

• To design and synthesize a new class of small-molecule photoactivatable optical sensors (SPOTs) for transmembrane potential.
• To characterize the properties and imaging applications of SPOT2.1.Cl.
• To demonstrate the utility of SPOT2.1.Cl in neuronal imaging.

Main Methods:

• Design and synthesis of SPOT2.1.Cl, incorporating VoltageFluor2.1.Cl (VF) dye and a dimethoxy-o-nitrobenzyl (DMNB) caging group.
• Localization studies in cell membranes.
• Photoactivation using spatially restricted light.
• Imaging of action potentials and neuronal structure via backfilling.

Main Results:

• SPOT2.1.Cl localizes to cell membranes and exhibits minimal fluorescence until photoactivated.
• Spatially controlled illumination of SPOT2.1.Cl-loaded cells results in bright, voltage-sensitive fluorescence.
• Activated SPOT enables single-trial action potential recording and structural tracing in neurons.
• Demonstrated cellular specificity and precise optical reporting of membrane voltage changes.

Conclusions:

• SPOT2.1.Cl is the first small-molecule photoactivatable optical sensor for transmembrane potential.
• This probe offers cellular specificity through patterned illumination.
• SPOT2.1.Cl provides fast, sensitive, and noncapacitive voltage sensing for neuronal systems.