3-D Printed Substrate Kills Microbes

Photo by Andreas Herrmann.


Photo by Andreas Herrmann.

Researchers at the University of Groningen in Germany have developed a 3-D printed substrate that kills microbes on contact. Its immediate applications will be in dentistry, but other implants may follow.

“Kids with braces have small metal blocks glued to their teeth, and these are an ideal breeding ground for the microbes that cause tooth decay,” said Andreas Herrmann, a materials scientist at the university’s Zernike Institute for Advanced Materials.

After the director of the Kolff Institute for Biomedical Engineering and Materials Science asked Hermann to come up with an antimicrobial dental glue, he decided to try incorporating antimicrobials in 3-D prints.

Herrmann added quaternary ammonium ions to routinely used monomers that polymerize under ultraviolet (UV) light. These positively charged molecules interact with the negatively charged bacterial membrane and puncture it, killing microbes. The researchers next used 2 approaches to make a printable antimicrobial material.

First, they mixed 2 different monomers and an additional quaternary ammonium compound with a polymerizable unit and used UV light to polymerize the whole mixture. But some antimicrobials could still leach out of the polymer mesh.

In the second approach, they polymerized the antimicrobial groups to form long chains. The resulting antimicrobial polymer was added to the 3-D printing fluid and got entangled with the other polymers during polymerization. Very little antimicrobial material diffused out.

“The trick in both approaches was to get the mixture right to enable 3-D printing and minimize any leakage of the antimicrobials. You don’t want them to enter the mouth and thus the intestines, where they could kill off gut microbes,” said Herrmann.

The researchers have tested printed objects with saliva. Also, Herrmann notes that all of the components already are used in human beings, but more tests are needed before the 3-D antimicrobials can be brought to market.

The first applications probably will be in orthodontics, where 3-D printed retainers and aligners already are common. Looking ahead, 3-D printed crowns with antimicrobial properties could be an option. Overall, antimicrobials could solve a major problem in dentistry.

“Any artificial objects in the mouth can be colonized by bacteria,” Herrmann said, which causes billions of dollars in dental costs each year. But these devices could be used beyond dentistry too. “All implants in medicine suffer from biofilm formation, so giving them antibacterial properties would be beneficial,” he added.

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