Cell membrane potential is associated with numerous normal and anomalous (driven by diseases or injuries) activities of mammalian neuron and muscle cells. Recently, significant interest has arisen in the development of new optical probes for the visualization of the membrane potential of large numbers (hundreds to thousands) of neurons simultaneously with single cell resolution. Ideally, such probes would overcome some of the limitations of current materials and techniques. Patch clamp, for example, is limited to single cell analysis while voltage-sensitive dyes and fluorescent proteins are plagued by photobleaching and intracellular instability. Semiconductor nanocrystals or quantum dots (QDs) offer superior optical properties for cellular sensing applications given their photostability, amenability to bioconjugation, and their ability to engage in efficient energy and electron transfer. We have developed a voltage-sensitive QD-based assembly comprised of a central QD scaffold around which is appended multiple copies of a peptide-fullerene (C<sub>60</sub>) conjugate. The photoexcited QD engages in electron transfer to the fullerene electron acceptor and the rate of this transfer process is modulated by changes in cellular membrane potential. We show the ability to control the efficiency of electron transfer by ratiometrically controlling the number of fullerene electron acceptors arrayed around the QD as well as by controlling the distance of the fullerene from the QD surface. In HeLa cells and in primary mouse cortical neurons, this optical construct efficiently reports on changes in cellular membrane potential induced by potassium chloride depolarization. The implications of this sensing modality on the ability to visualize the activity of neuronal cells, and other electrically excitable cells, will be discussed.

Quantum dot (QD)-fullerene (C<sub>60</sub>) conjugates for imaging real-time changes in cellular membrane potential

253rd National Meeting (2017)

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Quantum dot (QD)-fullerene (C60) conjugates for imaging real-time changes in cellular membrane potential

Quantum dot (QD)-fullerene (C₆₀) conjugates for imaging real-time changes in cellular membrane potential