Scientists at Penn State University have come up with a smart way to use ultrasound to see what our immune cells, particularly macrophages, are up to inside our bodies.
(Macrophages are a type of immune cells that act as a security guard to our body, fighting diseases and keeping our immune system in high gear.)
By using nanoemulsions — tiny bubbles sensitive to ultrasound and made from tiny oil droplets suspended in liquid — they were able to visualise macrophages with far greater clarity than existing techniques.
Why does their action matter? Because it could pave the way for doctors and scientists to gain a deeper understanding of macrophage function, ultimately leading to innovative treatments that enhance our body’s natural defence mechanisms. This innovation could unlock new treatments for conditions like cancer, autoimmune disorders, infections and tissue damage by enhancing our body’s natural defences.
How it works
The study, published in the journal Small, focused on macrophages. Lead author Inhye Kim, a post-doctoral fellow in biomedical engineering, highlights the need for precise control over bubble formation and persistence during imaging.
“We needed a way to get bubbles to form when we want them to form right at the time of imaging and not before, and also for these bubbles to persist as long as possible,” Kim says.
Their study introduced the nanoemulsion droplets into a laboratory medium containing macrophages. The droplets naturally absorb macrophages, and under ultrasound exposure, transform into gas bubbles due to the induced change in pressure. This transformation allows macrophage behaviour to be monitored through ultrasound imaging of the gas bubbles.
Senior author Scott Medina notes the significance of real-time visualisation for understanding disease progression and healing processes. “If we could visualise what these cells are doing in the body, in real-time, then we could learn a lot about just how diseases progress and how healing happens,” Medina comments.
Such a visualisation also has advantages over other methods of studying macrophages. In the past, conventional methods of studying macrophages in tissues involved taking samples of the tissue and treating them with special dyes or markers. The dyes or markers were used to make macrophages visible or to bind specifically to macrophages, distinguishing them from other cells in the tissue.
However, this process made the study longer and less precise than desired. Additionally, techniques like MRI and PET scans encountered challenges related to resolution and real-time tracking.
To overcome these limitations, the research team turned to ultrasound imaging, a widely used technique for examining internal tissues. However, conventional ultrasound struggled to distinguish macrophages from surrounding cells.
The novel use of phase-changing nanoemulsions as contrast agents in ultrasound imaging could significantly improve macrophage visualisation. In addition, the peptides used to create the emulsions can be customised, allowing specific interactions with different cell types, all without chemical modifications.
The technique was successfully tested on porcine tissue (obtained from domestic pigs). Further research aims to test its efficacy on other immune cell types within the body. The research team hopes to collaborate with immunology researchers to further refine and implement this technology.