# Design, synthesis and application of long wavelength fluorophores for bioimaging

> **NIH NIH F32** · UNIVERSITY OF CALIFORNIA BERKELEY · 2022 · $67,582

## Abstract

Project Summary
 Neurons and cardiomyocytes utilize rapid changes in membrane potential for cellular signaling. Understanding how
changes in membrane potential affect cell behavior across a population of neurons or cardiomyocytes is an important
challenge in biology. Widely used techniques to measure membrane potential, either directly or indirectly, consist of patch
clamp electrophysiology and calcium ion imaging agents. Using patch clamp electrophysiology to measure membrane
potential results in accurate measurements of membrane potential on the timescale of the action potentials. However, these
experiments are limited to a single cell membrane, which precludes using patch clamp electrophysiology to study larger cell
populations. Calcium ion imaging agents are widely used, as it has a higher throughput and is less invasive than patch clamp
electrophysiology. By measuring temporary changes in calcium ion concentrations, we are able to indirectly measure
changes in membrane potential. Unfortunately, a major drawback in this technique is the long durations of calcium ion
uptake (10-100 ms) found during a neuronal action potential, which is significantly longer than the actual action potential
itself (1-2 ms). This our ability to understand cell behavior and how it relates to these rapid signaling events.
 To address this challenge, our group has developed several different fluorescent probes called VoltageFluor dyes to
measure these rapid changes in membrane potential. The VoltageFluor dyes consist of a fluorescent xanthene core tethered
to a hydrophobic molecular wire. The molecular wire localizes in the cell membrane while the xanthene core orients itself
in the extracellular space. Using this system, we can measure rapid changes in membrane potential in large populations of
cells on the same time scale as the action potentials themselves.
 While our previous VoltageFluors work as intended, we wish to develop new VoltageFluors that emit light in the near
infrared. A red-shifted emission spectrum would allow these VoltageFluor dyes to be used in vivo as well as in conjunction
with other indicators that emit light at <600 nm. To accomplish this goal, we will develop new VoltageFluor dyes that
contain electron withdrawing groups in the xanthene backbone. In accordance with Dewar’s rule, the inclusion of electron
withdrawing groups will result in a red-shifted absorption and emission spectra. This hypothesis is supported by
computational studies we have undertaken. The planned syntheses of these xanthene cores will also be more robust and
tolerant of various functional groups than the syntheses of our previous dimethylcarbon and dimethylsilicon VoltageFluor
dyes.
 In comparison to our previously synthesized VoltageFluor dyes that utilize a dimethylcarbon and dimethylsilicon
backbone in the xanthene core, the electron withdrawing groups found in the proposed VoltageFluors offer new functional
handles that can easily be diversified. This expands the r...

## Key facts

- **NIH application ID:** 10437616
- **Project number:** 5F32GM139263-02
- **Recipient organization:** UNIVERSITY OF CALIFORNIA BERKELEY
- **Principal Investigator:** Nels Gerstner
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $67,582
- **Award type:** 5
- **Project period:** 2021-06-01 → 2023-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10437616

## Citation

> US National Institutes of Health, RePORTER application 10437616, Design, synthesis and application of long wavelength fluorophores for bioimaging (5F32GM139263-02). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10437616. Licensed CC0.

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