Researchers Use Gold Nanorods To Distinguish Between "Killer" and "Healer" Cells

Researchers have found a way to distinguish between M1 and M2 macrophage cells, identifying the "killer" and the "healer" cells.

A team from the Bar-Ilan University in Ramat Gan in Israel has illustrated a novel solution - using the scattering effect of Gold Nanorods. By manipulating the scattering effect and modifying the gold nanorods' surface coating, they can observe macrophages and see changes in whether they become M1 or M2 cells. Their study is published in the journal Nano Letters.

The Macrophage Problem

One of the body's defense against foreign and often harmful materials is the macrophage - a specialized type of white blood cell that can either eliminate invaders or work to repair injuries. Researchers have now devised a method for telling the two apart, helping future diagnostics of diseases.

Almost all biological systems have their defense mechanism to maintain the stability of its internal environment and protect itself from damage caused by external factors. For humans, there are white blood cells that work to defend the body. One of its types, the macrophage, is mainly made up of M1 and M2 - with M1 being the "killer" of foreign organisms and M2 being the "healer."

For healthy bodies, the human immune system generally keeps the M1 and M2 cells balanced. However, in the event of a disease or infection, or cases such as cancer or arthritis, the balance between these macrophages changes - increasing the concentration of either type of cell as needed. Enabling doctors to monitor these changes would allow easier and faster diagnosis. Unfortunately, no existing tool enables the detection of M1 and M2 cells from blood samples or tissue fluids without fluorescent tagging.

Exploiting The Scattering Effect

The scattering effect is the dispersal of light when it hits a material, usually dust and gas molecules. Since nanoparticles based on gold are known for their optical properties, having high absorbance in its surface and scattering effect, researchers used gold nanorods in their experiment.

To observe changes, researchers used a flow cytometer (FCM) to see changes in the cells' granularity - its internal complexity and structure. This method inquired whether it was possible to identify the macrophages that carried bits of gold nanorods and distinguish it through the nanorods' scattering properties. An FCM is generally used to determine the presence and volume of fluorescence-labeled cells. In the Bar-Ilan University study, however, the process was used for a label-free detection that would only detect the scattering from gold nanorods. Researchers observed that a specific coating in the gold nanorods had a greater selectivity for M2 cells compared to M1.

Dr. Ruchira Chakraborty, a lead researcher of the study from the Kofkin Faculty of Engineering and Institute of Nanotechnology and Advanced Materials, explained that their research creates a novel method of using FCM for cellular identification activities, using increased scattering from "internalized nanoparticles" - gold nanorods in this case.

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