A step-index fibre has a core material that transmits light and a cladding that protects the core and keeps the light from escaping
Researchers at Penn State University have developed a safe optical fibre which can deliver light and drugs into the body. This was developed out of a collaboration between electrical engineers and biomaterials engineers in Penn State's Materials Research Institute.
The ability to deliver light into the body is important for laser surgery, drug activation, optical imaging, diagnosis of disease, and in optogenetics— the experimental field in which light is used to manipulate the function of neurons in the brain. The task of delivering light into the body is difficult and usually, needs implantation of an optical fibre made of glass.
"The problem is that visible light can only penetrate to a certain depth, maybe hundreds of microns," said Jian Yang, professor of biomedical engineering, Penn State. "Near-infrared light might be able to penetrate a few millimetres to a centimetre, but that is not enough to see what is going on."
The fibreglass used by doctors today is brittle and not biodegradable. If it breaks, it damages the internal tissues. Yang is using a polymer based on citrate, a naturally occurring key ingredient in metabolism to create a step-index optical fibre for light delivery inside the body.
A step-index fibre has a core material that transmits light and a cladding that protects the core and keeps the light from escaping. "The present work demonstrates the first citrate-based flexible biodegradable polymeric step-index fibre," said Dingying Shan, a PhD student in Yang's group.
"The use of the citrate-based polymers enables ultrafine tuning of refractive index differences between the core and the cladding layers," added co-first author Chenji Zhang, a recent PhD graduate."We believe this new type of biodegradable, biocompatible and low-loss step-index optical fibre can facilitate organ-scale light delivery and collection," Shan said highlighting the usage of the new discovery. "And that it will become an enabling tool for diverse biomedical applications where light delivery, imaging or sensing are desired."