# Biocompatible fluorophores for shortwave infrared imaging

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA LOS ANGELES · 2023 · $382,124

## Abstract

The shortwave infrared (SWIR) region of the electromagnetic spectrum has become an exciting avenue for
imaging in mammals due to the increased penetration of light through tissue, decreased light scattering, and
minimal autofluorescence. In the previous granting period, we showcased an additional advantage of the SWIR
region– the enhanced spectral real estate which facilitates non-invasive multicolor imaging in mice. Taken
together, all these advantages set the stage for: 1) fundamental biological studies in animal models analogous
to those which have been enormously successful in cells and transparent organisms, 2) the ability to evaluate
controls in same animal as the experimental group, and 3) advanced clinical diagnostics for both intraoperative
and non-invasive use.
While the SWIR region has great potential, it cannot be realized without biocompatible contrast agents. This
proposal focuses on contrast agent development for high resolution multicolor imaging in the SWIR region,
building on the expertise we have gained in polymethine fluorophores over the last granting period. We have
prepared over 100 polymethine fluorophores and gained predictive metrics on the most classical photophysical
parameters of lmax.abs, lmax,em and FF. We have also learned some key lessons regarding utility of the fluorophores
including how to solubilize them in water and have gained appreciation for the different approaches to formulating
fluorophores for imaging. In collaboration with the Bruns laboratory, we demonstrated excitation-based multicolor
imaging with fluorophores well-matched to common laser lines.
In the next granting period, we specifically focus on optimizing fluorophores for use in excitation-based
multiplexing with detection in the high-resolution region of the SWIR (above 1400 nm) such that mm resolution
can be achieved. Aim 1 explores the chromophore scaffold itself optimizing the photophysical properties for
maximum absorption at commercial laser lines and emission >1400 nm. We take a physical organic chemistry
approach to fluorophore optimization and capitalize on the continually growing, fully characterized set of
systematically modified fluorophores our laboratory has prepared. Our work is aided by computation and theory
collaborations with the Lopez and Caram Laboratories. Aim 2 transforms the lead fluorophores from aim 1 into
water-soluble, targeted contrast agents. Finally in Aim 3, we aim image the lymphatic system, demonstrating the
need for mm resolution imaging and then using excitation-based multicolor imaging to evaluate sentinel lymph
node mapping and cancer metastasis.

## Key facts

- **NIH application ID:** 10737471
- **Project number:** 2R01EB027172-05A1
- **Recipient organization:** UNIVERSITY OF CALIFORNIA LOS ANGELES
- **Principal Investigator:** Ellen May Sletten
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $382,124
- **Award type:** 2
- **Project period:** 2023-09-13 → 2027-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10737471

## Citation

> US National Institutes of Health, RePORTER application 10737471, Biocompatible fluorophores for shortwave infrared imaging (2R01EB027172-05A1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10737471. Licensed CC0.

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