An optical fiber made from agar was produced at the State University of Campinas (Unicamp). The device is edible, biocompatible and biodegradable. And it could be used in vivo for imaging body structures, localized delivery of light for phototherapy or optogenetics [for example, the stimulation of neurons by light to study neuronal circuits] and localized delivery of medicines. Another possible use would be the detection of microorganisms in specific organs – in which case the probe, after being implanted and meeting its objective, would be completely absorbed by the organism.
The research, supported by Fapesp, was developed and led by professors Eric Fujiwara (Faculty of Mechanical Engineering, Unicamp) and Cristiano Cordeiro (Institute of Physics Gleb Wataghin, Unicamp), in collaboration with professor Hiromasa Oku (University of Gunma, Japan) .
An article about this was published by the researchers in the journal Scientific Reports, from the Nature Group.
Agar, also called agar-agar, is a natural gelatin extracted from seaweed. Its composition consists of a mixture of two polysaccharides: agarose and agaropectin. “Our optical fiber consists of an agar cylinder, with an external diameter of 2,5 millimeters [mm], and a regular internal arrangement of six cylindrical air holes, each 0,5 mm in diameter, surrounding a solid core. The light is confined due to the difference between the refractive indices of the agar core and the air holes”, says Fujiwara to Agência Fapesp.
“To produce the fiber, we pour food-grade agar into a mold, with six longitudinal rods arranged symmetrically around the main axis. The gelatin was distributed throughout the available space. After cooling, the rods are removed to form air holes and the solidified waveguide is released from the mold. The refractive index and fiber geometry can be adapted by varying the composition of the agar solution and the mold design, respectively,” explains Fujiwara.
The researchers tested the fiber in different media: air, water, ethanol and acetone. And they found that it is context sensitive. “The fact that gelatin undergoes structural changes under variations in temperature, humidity and pH makes the fiber suitable for optical sensing purposes,” says Fujiwara.
Another promising application is the simultaneous use of fiber as an optical sensor and growth medium for microorganisms. “In this case, the waveguide can be designed as a disposable sample unit, containing the necessary nutrients. The cells immobilized in the device would be optically sensed and the signal analyzed using a camera or spectrometer”, describes the researcher.
Read the article Agarose-based structured optical fiber published in Scientific Reports, from the Nature Group.
Published article originally on the Agência Fapesp website.
