3-D Printing: How Riboflavin Can Be Used to Fabricate Implantable Medical Devices

By Bob Michaels, Senior Technical Editor

Slowly but surely, 3-D printing is wending its way into the medical device sphere. From blood vessels and kidneys to tissue scaffolds and drug-delivery vehicles, many medical devices could eventually be fabricated using 3-D printing techniques.

One such method, known as two-photon polymerization, utilizes femtosecond lasers and photoinitiators to create structures with precise small-scale features out of photoreactive materials. However, because many commonly used synthetic photoinitiators exhibit poor biocompatibility, structures created using conventional synthetic photoinitiators have inherent limitations for use in medical implant applications.

Seeking an alternative, a team of researchers at North Carolina State University (NC State; Raleigh), the University of North Carolina at Chapel Hill, and Laser Zentrum Hannover has discovered that a photoinitiator containing riboflavin (vitamin B2) can replace conventional synthetic photoinitiators in two-photon polymerization, facilitating the use of this technique for the manufacture of medical device implants.

Riboflavin and the photoinitiator triethanolamine have previously been combined for polymerizing materials at larger length scales. Now, however, the research team has achieved a breakthrough by combining riboflavin and triethanolamine to create small-scale structures by means of two-photon polymerization.

In addition, the researchers have confirmed that materials polymerized using the riboflavin-triethanolamine combination exhibit greater biocompatibility than materials polymerized using two common synthetic photoinitiators. "A genotoxicity study showed that one of the materials polymerized using the riboflavin-triethanolamine combination was less toxic than a glass material that served as a control," says Roger Narayan, a professor in the UNC/NCSU Joint Department of Biomedical Engineering. "And when cells were grown on a tissue-engineering scaffold created using this method, a significant number of them were alive and few were dead after a period of five days."

"Right now, 3-D printing is commercially used to create a variety of medical devices, such as hearing aids," Narayan comments. "But there is a growing need to manufacture implantable medical devices and artificial organs with precise small-scale geometries. The results of this study form the basis for using two-photon polymerization as a platform to create 3-D printed medical implants with precise small-scale features.