# Biogenic Gas Nanostructures as Molecular Imaging Reporters for Ultrasound

> **NIH NIH R01** · CALIFORNIA INSTITUTE OF TECHNOLOGY · 2024 · $678,465

## Abstract

SUMMARY
Ultrasound is among the world’s most widely used biomedical imaging technologies due to its low cost and ability
to visualize deep tissues with high spatial and temporal resolution. However, ultrasound has had a relatively
small role in molecular and cellular imaging due to a lack of contrast agents and reporter genes connected to
specific aspects of cellular function such as gene expression and intracellular signaling. To address this
limitation, we are developing acoustic biomolecules – proteins that can be imaged with ultrasound. These
constructs are based on gas vesicles (GVs) – a unique class of air-filled protein nanostructures from buoyant
photosynthetic microbes, which we introduced as imaging agents for ultrasound in 2014 (Nature Nano. 9:311)
and as acoustic reporter genes for commensal microbes in 2018 (Nature 554:86). Since our last renewal, we
took the next major step of demonstrating that GVs can function as reporter genes in mammalian cells (Science
365:1469, 2019 and Nature Biotech. 2023), learned how to turn GVs into dynamic biosensors of intracellular
protease activity (Nature Chem. Biol. 16:988, 2020), developed methods to detect GV-expressing cells down to
single-cell sensitivity (Nature Methods 18:945, 2021), demonstrated their utility as injectable contrast agents in
a disease context (ACS Nano 14:12210, 2020), and made several other advances in understanding and
engineering GVs and accompanying ultrasound methods and applications. Much work remains to be done to
develop GVs as targeted nanoscale contrast agents and reporter genes with broad utility in biology and medicine.
Our proposed next steps will enable specific applications of GVs in biomedical research and clinically relevant
contexts. These next steps include developing GVs as both targeted nanoscale contrast agents and acoustic
reporter genes, focusing on biomedically impactful applications in (1) labeling tumors for intraoperative
ultrasound imaging and (2) visualizing the migration and proliferation of primary immune cells during
immunotherapy. We will support the future clinical translation of these applications by establishing standardized
protocols for high quality GV production, characterizing and optimizing their in vivo tolerability and
immunogenicity and developing new nonlinear pulse sequences allowing ultrasound to nondestructively image
lower doses of injected GVs and smaller numbers of GV-expressing cells. Successful completion of this work
will result in unprecedented capabilities for ultrasonic molecular and cellular imaging and lay the foundation for
developing clinical nanoscale and cell-based diagnostics and therapeutics.

## Key facts

- **NIH application ID:** 10804332
- **Project number:** 2R01EB018975-09A1
- **Recipient organization:** CALIFORNIA INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** Mikhail Shapiro
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $678,465
- **Award type:** 2
- **Project period:** 2024-01-01 → 2027-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10804332

## Citation

> US National Institutes of Health, RePORTER application 10804332, Biogenic Gas Nanostructures as Molecular Imaging Reporters for Ultrasound (2R01EB018975-09A1). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10804332. Licensed CC0.

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