Capturing Live Cell Dynamics with 3-D Nanoscale Resolution

May 20, 2020

Technion scientists have developed a method for three-dimensional imaging of nanometric processes, such as those in live flowing cells. The group, headed by Dr. Yoav Shechtman of Technion Faculty of Biomedical Engineering, took apart an existing imaging machine worth hundreds of thousands of dollars and reassembled it. The result is a machine that produces three-dimensional images of 1,000 cells per minute.

The research was led by post-doctoral researcher Dr. Lucien E. Weiss. The team’s findings were recently published in Nature Nanotechnology.

“Our goal is to enable three-dimensional imaging within live cells under conditions that resemble their natural environment,” explained Dr. Shechtman. “No less important, we aim to do so at high throughput rates. It’s a huge challenge, since 3-D microscopy usually requires extensive amounts of time and some sort of scanning. Here we use single images while the cells are flowing.”

Experiments using the new system were carried out on DNA molecules of live yeast cells and white blood cells with engineered nanometric particles provided by the laboratory of Professor Avi Schroeder of the Technion’s Wolfson Faculty of Chemistry Engineering.

“This success can have very important applications in basic science, such as understanding DNA’s three-dimensional structure in a living cell, but also in the field of nano-medicine, meaning medical treatment based on engineered nanometric particles such as those created in Prof. Schroeder’s lab,” explained Dr. Shechtman. “For example, the new technology will enable us to measure the absorption rate of therapeutic particles in live cells, track their dispersal in the cell and monitor their effect on the cell. Today there are techniques for mapping and measuring cells, but those that provide high throughput only show a partial and two-dimensional picture. Our technology combines the advantages of the various techniques and provides a three-dimensional image at a high rate.”

The innovative technology is based on reengineering of ImageStream ― a sophisticated imaging machine that was procured by the Lorry I. Lokey Interdisciplinary Center for Life Sciences and Engineering at Technion at a cost of hundreds of thousands of dollars. This machine combines two different technologies ― flow cytometry and fluorescent microscopy ― making it possible to analyze cells at a rapid rate.

“The sampling rate and number of cells sampled are very important in the biological context, since biology is typically ‘noisy’ and not precise, and in order to reach a conclusion it is necessary to have statistics for large quantities,” said Dr. Shechtman. “In certain cases, due to low sampling rates, it is impossible to collect this type of statistic information. Until you finish collecting the data, the interesting phenomenon has already changed. Therefore, it is important to use a technology that enables high rates of sampling.”

ImageStream serves many purposes, including defining population attributes, diagnosing medical conditions, and testing new drugs. According to Dr. Shechtman, “It’s an excellent tool, but it has a serious shortcoming ― it can only create two-dimensional images of objects. In other words, it only gives us two-dimensional mapping. This is clearly a problem since in real life objects are three-dimensional. Even if we just want to determine distances between two particles, a two-dimensional measurement is not sufficient, since the depth dimension also contributes to the distance between two points.”

This was precisely the main technological challenge in this research: transforming ImageStream into a three-dimensional imaging system.

“To that end, we needed to ‘open the hood’ and assemble our unique optic system inside. Keep in mind that this is a $600,000 machine and we couldn’t take for granted that the Lokey Center’s Imaging Unit would agree, but from the moment that we opened up the machine and looked inside, it was obvious what we needed to do (without causing damage),” said Dr. Shechtman.

The research group installed on the ImageStream the technology it has developed in recent years ― technology for localization microscopy based on wavefront design. This is actually controlled distortion of the optic system, so that the position of particles in 3-D space can be mapped. This technology is based on imaging colored molecules imbedded in the sample that mark important locations, such as cell nuclei. Using the shape obtained from the camera after it has passed through the distorted optic system, the machine analyzes the three-dimensional location of the object being examined. To date, this technology has been used for three-dimensional imaging of one or a few cells at a time, and connecting it to the cytometry instrument renders it capable of mapping flowing cells. This connection, which is in itself an enormous technological challenge, accounts for the successful sampling at an extremely high throughput ― thousands of cells per minute.

The scientists expect that this technological achievement will lead to important scientific developments and applications in the fields of biological and biotechnological research, medical diagnostics, and development of new medical treatments.

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