Instantly measure tissue health using only light
Aggie researchers have created a new noninvasive method to monitor the health of 3D-printed and natural tissues in real time, empowering experts to design better disease treatments and print more complex tissues — potentially paving the way for printed organs.
Dr. Michael McShane holds an optical sensor that can read the sensor particles in 3D-printed or implanted structures.
Using 3D printers to create complex structures out of biocompatible materials that can include living cells has the potential to revolutionize medicine. This process — 3D bioprinting — has powered breakthroughs in tissue engineering, medical implants and reconstructive surgery and may ultimately allow for the creation of transplantable human organs.
Despite these advances, researchers have few ways to accurately track the health of the structures they make. As tissue engineers pursue creating larger and more complex structures — such as full transplantable organs — this becomes increasingly problematic.
“The biggest challenge is to monitor the health of the cells that we are cultivating. There are very limited technologies available to measure these things,” said Dr. Waqas Saleem, who earned his Ph.D. from the Texas A&M University Department of Biomedical Engineering. “The real-time monitoring options are extremely limited, bulky and invasive. You have to pierce and damage the structure in order to measure metabolite levels.”
Dr. Waqas Saleem
Saleem created a potential solution. Alongside Dr. Michael McShane and fellow researchers, he developed a method for placing microscopic sensor particles within the printed material itself, allowing researchers to measure the levels of nutrients — and from this information infer cell health — using only light. Their research was published in Advanced Functional Materials.
“We are integrating sensors in the exact place from which we want to receive information,” said McShane, biomedical engineering professor and department head. “We don’t have to do a physical collection or any kind of penetration of the tissue. We can transmit light to the material — even through skin in the case of implants — and it will allow us to noninvasively monitor what is going on inside.”
The sensor particles are phosphorescent, meaning they absorb and then emit light, much like the glow-in-the-dark materials used in children’s toys. When exposed to light from an inexpensive red LED, the sensor particles absorb that light and then emit their own, modified by their surroundings. The entire process lasts only milliseconds — too fast for the human eye to even detect — but provides optical sensor equipment with a wealth of information.
The way the particles emit their light is sensitive to oxygen. As oxygen levels change, so do the characteristics of the light from the sensor particles. By packaging the particles with enzymes that consume oxygen when they interact with specific nutrients, researchers can use this oxygen detection to accurately measure the amount of other vital nutrients, like glucose and lactate. A single flash of light gives researchers real-time chemical data without any invasive procedures.
Implementing this technology simply requires researchers to mix Saleem and McShane’s sensor particles into their material before printing. The created structure can then be measured using only optical equipment.
While the technology is still in its infancy, the potential applications are numerous. For patients living with chronic conditions that require constant monitoring, like diabetes or kidney failure, a single injection could implant a sensor smaller than a grain of rice just below the skin, eliminating the need for continuous blood testing. For patients recovering from transplants or even cancer surgery, these sensors could allow doctors an immediate and continuous chemical analysis of how healthy affected tissues are without having to perform painful biopsies.
“We could build something into a phone,” said McShane. “It would be as simple as holding up your phone over your implant, pressing a button and holding it there while it makes the reading. If you needed continuous measurements, we could design patches that adhere to the skin. These kinds of tools can help patients manage themselves without having to constantly go get blood tests or face-to-face consulting. They can collect information from their own body more frequently than lab testing, and have online analytics, feedback and guidance informed by what is happening inside of them right now.”
The ability to noninvasively monitor cell health would empower researchers across numerous disciplines. Drug development teams could better test the effectiveness of new treatments, and tissue engineers would be able to print larger and more complex bioprinting structures.
“I personally believe that this technology will help researchers to rapidly monitor the growth of cells, especially in complex environments,” said Saleem. “For researchers who are developing or screening drugs, it could be extremely beneficial to see the impact of a certain drug on the growth of cells or the inhibiting of the growth of cancer cells. What that would eventually lead to is new therapies and new ways of growing cells in bulk quantities. In the future, it could potentially lead to transplantable organs.”
