Researchers Create Ship Hull Paintable Protein
A team at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, have recently developed a nontoxic, environmentally friendly paintable protein that inhibits fouling. The new coating reportedly stems from a 2021 patent for antimicrobial coatings.
The research results were published in the Journal of Coatings Technology and Research.
According to the release, active proteins, or enzymes, have previously been identified as potential nontoxic antifouling agents. However, until now, no one had reportedly developed an effective way to bind enzymes onto a specific location while maintaining their functionality. Enzymes must be covalently, or chemically, attached to a surface to maintain their antifouling properties.
“Many marine animals do not want to be covered in biofouling and have developed enzymes to protect themselves,” said project lead Reid Messersmith, a molecular engineer in APL’s Research and Exploratory Development Department (REDD). “Taking inspiration from animals, we developed an enzyme coating that could be applied directly to surfaces.”
Biological scientist Ryan Baker-Branstetter, who led the enzyme and antifouling research, added that biofouling develops from bacteria settling on a surface. Consequently, if the coating could prevent small bacteria from forming, larger organisms would not follow.
“It’s difficult to get enzymes to stick to just anything and remain active in the process. Bioconjugation is a technique to couple naturally occurring biomolecules and synthetic compounds. There have been promising laboratory results proving that certain enzymes can be attached to certain surfaces, but those results have not translated into real-world applications,” said Messersmith.
“We wanted to create a paint bucket approach, where someone could walk up and efficiently and effectively slap the coating on a surface.”
As a result, researchers needed to identify an agent capable of bonding an enzyme to a synthetic compound, or a “linker.” The team then developed an enzyme-based polymer coating with an ortho-phthaldialdehyde (oPA)-based linker capable of bonding enzymes onto surfaces.
APL reports it is also linked rapidly, taking less than five minutes to form a layer of material. The oPA-based linker reportedly maintained activity for extended periods of time in experiments, compared to no linker and a commercially available linker.
“The first protein we painted in 2021, red fluorescent protein, established that the chemistry behind the coating system and our linker worked. This allowed us to revisit which proteins would effectively prevent biofouling in our latest research,” said Messersmith.
The enzymes the researchers looked at were xylanase, a naturally occurring enzyme produced by fungi, bacteria, marine algae and many other organisms, often used in commercial baking, and a mixture of lysing complex enzymes, a molecule extracted from a fungus.
Using click chemistry, the team was reportedly able to attach the coating without any catalyst or heat. After two months submerged in artificial seawater, the xylanase and lysing complex coatings proved highly active, demonstrating the material’s longevity and potential for eco-friendly antifouling.
“I have worked on a lot of projects, and typically the tenth thing you try works. But it is very rare for the first approach to work out,” said Baker-Branstetter.
“Having early success with the enzymes allowed us to look further into other interesting questions, such as the paints’ longevity and activity across a range of environmental conditions.”
Additionally, APL reports that the team found not only that their coatings prevented the bacteria from adhering to a surface, but that they were also able to remove bacteria that had already settled.
According to the lab, paintable proteins have a variety of applications, including one example of using it as a paint-on sensor for detecting toxic gas in the air. The oPA linker can reportedly work with a wide variety of proteins because it acts on the exterior of proteins, without interfering with their functioning.
“Traditional sensors need to test for every single toxic gas independently, but the biochemistry in paintable proteins could act as a comprehensive sensor,” said Messersmith.
“The paintable approach can be used for a variety of different proteins—each protein performs a different function, and with this system, you could theoretically coat any protein you want.”