# Imaging enzyme activity by Overhauser-enhanced MRI

> **NIH NIH R21** · WEST VIRGINIA UNIVERSITY · 2020 · $218,640

## Abstract

ABSTRACT
Mapping the activity of an enzyme in vivo, directly within its natural environment, may provide unique insights
into the role of a particular enzymes in pathophysiology of various diseases but remains extremely challenging.
Recently, PI and colleagues demonstrated for the first time the ability of electron paramagnetic resonance (EPR)
to image enzymatic activity using a nitroxide radical substrate of alkaline phosphatase (ALP). However, the in
vivo application is hampered by the fast bioreducation of the nitroxide fragment. This project aims to develop
the first biostable paramagnetic probes sensitive to enzymatic activity. The design is based on the triarylmethyl
(TAM) radical scaffold known for its exceptional stability in biological milieu, narrow linewidth and high
performance in polarization for Overhauser enhanced magnetic resonance imaging (OMRI). To achieve this goal
we will rely on our recent advances in the chemistry of TAM functional probes that allow for multifunctional
mapping using EPR imaging and/or OMRI. To prove the concept, under specific aim 1 (SA1) we will synthesize
TAM-based paramagnetic substrates of alkaline phosphatase whose spectrum is modified upon enzymatic
dephosphorylation. In addition, the synthesized probes will inherit the intrinsic sensitivity of TAM radical to tissue
pO2, therefore making them dual function enzymatic ALP & pO2 probes. Under SA2 we will perform in vitro
optimization of the OMRI sequences for dual ALP & pO2. Under SA3, as a first application of this new concept
in vivo, we will image alkaline phosphatase (ALP) activity concurrently with tissue oxygenation using OMRI in
the tumor microenvironment of a HeLa subcutaneous flank tumor model. Cancer research has recently
experienced a paradigm shift from the seemingly obvious target of tumor cells towards key support systems of
cancer, the tumor microenvironment (TME). Tissue pO2 and the activities of enzymes are among the important
TME biomarkers. The imaging results will be validated using independent techniques, namely Oxylite for pO2
and optical imaging for ALP. The project focuses on the dual ALP & pO2 mapping using OMRI as a proof of
concept but the probe scaffold has been designed for easy application to many other important enzymes in the
future. The success of this proposal will provide a unique tool for in vivo enzymology allowing to map the activity
of an enzyme and to correlate spacially this activity with tissue pO2. This unique tools will allows for outstanding
applications in drug screening, therapy optimization, predication of the response to a particular treatment or to
study the role of a particular enzyme in physiology and physiopathology.

## Key facts

- **NIH application ID:** 9979029
- **Project number:** 1R21EB028553-01A1
- **Recipient organization:** WEST VIRGINIA UNIVERSITY
- **Principal Investigator:** Benoit Driesschaert
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $218,640
- **Award type:** 1
- **Project period:** 2020-08-04 → 2023-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9979029

## Citation

> US National Institutes of Health, RePORTER application 9979029, Imaging enzyme activity by Overhauser-enhanced MRI (1R21EB028553-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9979029. Licensed CC0.

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