# TR&D Project 3: Photoacoustic Detection of Metal Fluxes at the Tissue Level

> **NIH NIH P41** · MICHIGAN STATE UNIVERSITY · 2022 · $184,442

## Abstract

PROJECT SUMMARY – TR&D PROJECT 3
Photoacoustic Detection of Metal Fluxes at the Tissue Level
Modern optical microscopic modalities offer the following optical contrasts: optical scattering, autofluorescence
(intrinsic fluorescence), molecular probes (extrinsic fluorescence), and nonlinear optical effects. One key
contrast, optical absorption, is inaccessible by established microscopic modalities. As a result, bioelement
investigation in biological tissue mainly rely on various fluorescence probes. A lasting challenge in designing
fluorescence probes is to overcome low quantum yield, where major optical energy deposited to the probes is
dissipated via a non-radiative pathway as heat instead of as fluorescent emissions.
Measuring nonradiative thermal generation or optical absorption could offer a new way to conduct bioelement
imaging and bypass the quantum yield challenge. Imaging optical absorption quantifies ionic concentrations
with high accuracy when the molar extinction coefficient is known. Imaging optical absorption permits direct
quantitation of certain highly-optically absorbing ions (i.e. Fe in hemoglobin) and will stimulate the development
of a new class of molecular probes that focus on high extinction coefficients only, for which the struggle to
achieve high fluorescent quantum yield becomes much less critical.
In this Technology Research and Development (TR&D) project we will develop a new optical absorption
microscopy modality, referred to as optical Micro-Ring Resonator-Based Photoacoustic Microscopy or MRR-
PAM, which measures optical absorption using ultrasound. MRR-PAM detects ultrasound waves induced by
laser energy absorption and, consequently, heat generation and thermoelastic vibration. Compared with
existing photoacoustic microscopy, MRR-PAM improves the ultrasound detection bandwidth and axial
resolution by 10-fold and detection sensitivity by 100-fold. MRR-PAM provides a unique tool to enable tissue
imaging in all the DBP themes, such as the strongly scattering brain slices, thick tissue slice or whole mouse
kidney, whole zebrafish and zebrafish larvae. It will provide a new tool to quantify iron metabolism. MRR-PAM
extends the imaging capabilities developed in other TR&D projects to quantify bioelement distributions and
fluxes in both fixed and living tissue slices. It offers the possibility to image whole organs and, potentially, living
animals. The unique MRR developed in this TR&D project can be broadly disseminated and will likely impact
several other biomedical fields beyond bioelement research.

## Key facts

- **NIH application ID:** 10494062
- **Project number:** 5P41GM135018-03
- **Recipient organization:** MICHIGAN STATE UNIVERSITY
- **Principal Investigator:** Hao F Zhang
- **Activity code:** P41 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $184,442
- **Award type:** 5
- **Project period:** 2020-07-01 → 2025-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10494062

## Citation

> US National Institutes of Health, RePORTER application 10494062, TR&D Project 3: Photoacoustic Detection of Metal Fluxes at the Tissue Level (5P41GM135018-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10494062. Licensed CC0.

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