Researchers at Stanford have developed a noninvasive method to deliver light deep inside the body for medical use. Light is useful in medicine because it can stimulate cell growth, control nerve signals, and help treat cancer. However, light does not travel well through tissue, so current methods usually require surgery or inserted optical fibers.
The new approach uses special nanoparticles injected into the bloodstream. These tiny particles travel through blood vessels and reach any tissue. They stay inactive until hit by focused ultrasound waves, which then make the particles emit light exactly where needed. Ultrasound can penetrate deep into the body more easily than light.
In tests with mice, the researchers injected the nanoparticles and used a small ultrasound device shaped like a hat. The ultrasound created light inside the brain, which activated specific neurons and caused the mice to turn left or right depending on which brain area received light. This showed that the light could reliably control behavior without any implants.
Noninvasive light delivery opens new treatment possibilities
The technique worked in different body regions and allowed light to be produced at multiple spots or scanned across tissue. The current nanoparticles produce blue light, which can stimulate neurons or be used in photodynamic therapy for cancer. Researchers are also testing materials that emit ultraviolet light, useful for killing bacteria and viruses.
Future plans include combining the system with light-activated gene editing to turn gene changes on and off in precise locations. Before human use, safety must be confirmed. The current particles do not break down quickly and could build up in organs such as the liver. The researchers hope to replace them with safer biological materials that the body can clear naturally.
This proof-of-concept demonstrates that ultrasound can trigger programmable light emission deep inside living tissue. The method could make light-based treatments for brain disorders, cancer, infections, and gene editing simpler and less invasive.
The study was published in Nature Materials.