# Living Additive Expansion Microscopy

> **NIH NIH F32** · MASSACHUSETTS INSTITUTE OF TECHNOLOGY · 2020 · $65,310

## Abstract

PROJECT SUMMARY/ABSTRACT
Expansion microscopy (ExM) is a powerful new imaging technique that physically magnifies tissue samples to
enable super-resolution imaging on conventional microscopes. The expansion process relies on the synthesis
and expansion of a polyelectrolyte network within a biological specimen. The effective resolution accomplished
by ExM is directly related to the factor of expansion achieved (effective resolution = (original
resolution)/(expansion factor)). Typical procedures expand samples to 4–4.5x their original size, thereby
enhancing resolution on conventional optical microscopes from ~300nm to ~70nm. Greater effective resolution
can therefore be achieved with increasing expansion; however, the expansion process is ultimately limited by
the thermodynamics of network swelling and the static nature of the gel, in which the polymer chains are “dead”,
unable to grow further after the polymerization. Living Additive Manufacturing (LAM) is a new way to synthesize
polymer gels unconfined by the limits of expansion. LAM relies on the photocontrolled radical polymerization of
a polymer network with embedded photoactive trithiocarbonate (TTC) groups in each network strand. In the
presence of monomer and light, polymerization of network strands is initiated, consuming monomer and growing
the polymer network equivalently in each direction. Because LAM uses controlled polymerization, chain
termination is minimized, thereby enabling reinitiation and continual growth of the network under light irradiation,
with essentially no restraints on achievable growth/expansion factors. In this proposal, we aim to combine LAM
and ExM to achieve unprecedented levels of expansion in a process we call Living Additive Expansion
Microscopy (LAExM). TTC-gel synthesis and photogrowth will be optimized for biological tissue and the ability
to grow the embedded network in an isotropic manner will be analyzed. LAExM is anticipated to enable near-
limitless expansion of the tissue network, thereby removing any current limitations due to accessible expansion
factors in ExM. LAExM will therefore be employed to obtain ultrahigh resolution images of important
supramolecular structures associated with memory and learning such as actin and spectrin in neurons and
amyloid plaques in brain parenchyma. This proposal requires extensive collaboration between the Johnson,
Boyden, and Tsai groups, in addition to the microscopy and imaging facilities at MIT. Training will be done by
members of the Johnson and Boyden labs for the optimization of the chemistry and tissue growth protocols,
respectively. The Tsai group will provide guidance in the imaging of amyloid plaques in tissue associated with
Alzheimer’s disease. Monthly meetings will be held to evaluate results and assess or optimize the current training
plan. The proposed work will benefit from the scientific environment at MIT and the Johnson, Boyden and Tsai
labs, all of which promote co-operation and collaboration w...

## Key facts

- **NIH application ID:** 10068111
- **Project number:** 1F32GM136190-01A1
- **Recipient organization:** MASSACHUSETTS INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** Megan Hill
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $65,310
- **Award type:** 1
- **Project period:** 2020-09-30 → 2023-09-29

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10068111

## Citation

> US National Institutes of Health, RePORTER application 10068111, Living Additive Expansion Microscopy (1F32GM136190-01A1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10068111. Licensed CC0.

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