# High accuracy optical growth assay of 3D cellular systems

> **NIH NIH R01** · UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN · 2020 · $459,925

## Abstract

Project Summary
Growth regulation of mammalian cells has been described as "One of the last big unsolved problems in cell
biology". The ability to measure accurately the growth rate of single cells has been the main obstacle in
answering this question. From a clinical perspective, the basic understating of cell growth kinetics and how it is
modulated by disease and treatment will allow for more targeted drug development.
In recent years, there has been a significant interest in multidisciplinary work by biomedical engineers and
scientists with a vision of developing 3D ex vivo tissue models of human organ function, anatomy, and disease.
These 3D cellular systems are referred interchangeably as organoid, organotypic, or spheroid (spherical
organoid). Organoids self-assemble under proper conditions, i.e., when relevant components, such as
extracellular matrix (ECM) proteins, are present. Organoids are well documented to better recapitulate aspects
of in vivo organ function and human disease. The common tool for analysis of such systems has been confocal
(fluorescence) microscopy of fixed specimens. However, this approach does not reveal structural information in
the center of the construct and, most importantly, is limited in terms of time-lapse imaging. There is a critical
need for revealing subcellular structures in label-free mode with high contrast, which allows for dynamic, non-
destructive imaging. At the same time, quantifying the dry mass of the organoid and its cellular components will
inform on the basic organ function and disease, with and without treatment.
Despite this critical need, a unified, easy-to-use methodology to measure the growth rate of individual cells and
3D constructs is lacking. Until recently, the state-of-the-art method to assess a single cell growth curve was
using Coulter counters to measure the volume of a large number of cells, in combination with careful
mathematical analysis. For relatively simple cells such as Escherichia coli (E. coli), traditional microscopy
techniques have also been used to assess growth in great detail. In this type of method the assumption is that
volume is a good surrogate for mass; however, this assumption is not always valid, for example due to
variations in osmotic pressure.
We propose to develop a practical dry mass assay for 2D cell populations, as well as 3D organoids,
based on a novel imaging method developed in our laboratory: Spatial Light Interference Microscopy
(SLIM) for 2D cultures and Gradient Light Interference Microscopy (GLIM) for 3D organoids. SLIM/GLIM
takes advantage of the fact that optical phase delay accumulated through a live cell is linearly
proportional to the dry mass (non-aqueous content) of the cell. Due to its particular interferometric
principle, GLIM significantly suppresses multiple scattering and, as result, is capable of imaging thick
specimens such as organoid/spheroids. The project aims to optimize and translate the composite
SLIM/GLIM technology into a...

## Key facts

- **NIH application ID:** 9852604
- **Project number:** 5R01GM129709-02
- **Recipient organization:** UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN
- **Principal Investigator:** Gabriel Popescu
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $459,925
- **Award type:** 5
- **Project period:** 2019-02-01 → 2023-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9852604

## Citation

> US National Institutes of Health, RePORTER application 9852604, High accuracy optical growth assay of 3D cellular systems (5R01GM129709-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9852604. Licensed CC0.

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