New combination techniques may isolate cell types and prove effective against pathogens

To develop effective treatments for pathogens, scientists first need to figure out how they attack host cells. An efficient way to carry out these studies on a large scale is to use a fast screening test called an assay.

Researchers at the University of Texas A & M have invented a high-throughput cell separation method that can be used in combination with droplet microfluidics. This is a technology that allows small droplets of fluid, including biological or other cargo, to move accurately and quickly.

Specifically, researchers have used an electric field to successfully separate pathogens attached to host cells from pathogens that are not attached within a single droplet.

With the exception of cell isolation, most biochemical assays have been successfully converted into a droplet microfluidic system that enables high-throughput testing. We have addressed that gap, and now cell separation can be done in a high-throughput way within the droplet microfluidic platform. While this new system certainly simplifies the study of host-pathogen interactions, it is also very useful in environmental microbiology and drug screening applications.“”

Arum Han, Senior Researcher and Professor, Department of Electrical and Computer Engineering, University of Texas A & M

Researchers reported their findings in the August issue of the journal Lab-on-a-chip..

Microfluidic devices consist of a network of micron-sized channels or tubes that allow controlled movement of the fluid. Recently, microfluidics using water droplets in oil have become popular in a wide range of biotechnology applications.

These droplets, which are picolitres (or one millionth of a microliter) in volume, can be used as a platform for carrying out biological reactions and transporting biological material.Millions of droplets in a single chip facilitate high-throughput experiments, saving laboratory space as well as chemical costs reagent And manual labor.

Biological assays can contain different cell types within a single droplet and will eventually need to be isolated for subsequent analysis. According to Han, this task is very difficult with a liquid drop microfluidic system.

“It is very difficult to separate cells within a small droplet, because when you think about it, it is a small droplet with a diameter of 100 microns first, and then within this very small droplet, multiple cells. Because all the types are mixed, “he said. ..

To develop the techniques needed for cell isolation, Han and his team selected a host pathogen model system consisting of Salmonella and human macrophages, a type of immune cell. When both of these cell types are introduced into the droplet, some bacteria attach to macrophage cells. The purpose of their experiments was to isolate Salmonella that adhered to macrophages and Salmonella that did not.

For cell separation, Han and his team built two pairs of electrodes that generate an oscillating electric field in the immediate vicinity of a droplet containing two cell types. Because bacteria and host cells have different shapes, sizes, and electrical properties, they found that electric fields produce different forces for each cell type.

This force moved one cell type at a time, separating the cells into two different locations within the droplet. To separate the mother droplet into two daughter droplets containing one type of cell, researchers also created a downstream Y-shaped split junction.

According to Han, these experiments were performed with well-established hosts and pathogens, but new microfluidic systems with droplet separation are available when the pathogenicity of the bacterial species is unknown. Most useful for.

He added that their technology enables fast, high-throughput screening in these situations and other applications that require cell isolation.

“The hands of a liquid processing robot can perform millions of assays, but they are very costly. Droplet microfluidics do the same with millions of droplets much faster and much faster. It’s cheap, “Han said. “Currently, we have integrated cell separation technology into the droplet microfluidic system to accurately manipulate cells within droplets in a high-throughput way that was not possible before.”