Xiaopeng Li looks at his work as a kind of art form. But instead of painting or sculpting, his mediums are intricate molecular designs, and his masterpieces are paving the way for new and innovative techniques in the fight against deadly bacteria.
An assistant professor in the University of South Florida Department of Chemistry, Li and his research team, along with collaborators at USF and around the world, recently published a new set of supramolecular structures they call Kandinsky circles. Li says the structures, published in Nature Communications, are named after Russian artist Wassily Kandinsky because of their likeness to the artist’s famous painting, ‘Color Study. Squares with Concentric Circles.’
“My son loves painting and last year he started incorporating these concentric rings into his art. When I asked him why, he told me they’re Kandinsky circles,” Li explained. “After doing some research on the artist, I realized the design looked very similar to the supramolecules we were trying to build, so it seemed right to name them after this famous artist.”
Supramolecules are large molecular structures made up of individual molecules. Unlike traditional chemistry, which focuses on covalent bonds between atoms, supramolecular chemistry studies the noncovalent interactions between molecules themselves. Many times, these interactions lead to molecular self-assembly, naturally forming complex structures capable of performing a variety of functions.
Li and his team started working on their latest set of supramolecules in 2013, trying to fine tune the chemistry to increase the number of concentric ring layers that form to make up the structure. The more layers, the more stable the supramolecules become, according to Li. The latest and most promising iteration is a positively-charged hexagonal supramolecule with four concentric rings.
In laboratory tests, the molecular-Kandinsky circles exhibited high antimicrobial activity against Gram-positive pathogen methicillin-resistant Staphylococcus aureus, or MRSA. Li says the structure’s antibacterial properties could help spur the development of a new type of antibiotic.
“Our supramolecules attach to the surface of the MRSA bacteria and destroys the cell membrane, effectively killing the cells,” he said. “What’s interesting is that most traditional antibiotics impact cellular function whereas our supramolecule makes a physical impact. It basically punches a hole in the cell membrane. It’s really a different approach to killing the bacteria.”
The tactic comes at a time when researchers are seeing more and more antibiotic drug resistance. In fact, the World Health Organization (WHO) has identified this evolving challenge as one of the three greatest threats facing mankind in the 21st Century.
“The fact that our supramolecule uses a different mechanism to kill the bacteria is very exciting,” Li said.
Researchers believe the destruction of the cell membrane is a result of the size and shape of the Kandinsky circles. After the initial self-assembly to form the individual supramolecules, the structures are prone to stack on top of one another, forming tubular nanostructures. It’s these nanotubes that researchers believe cut into the cell, and eventually kill it.
Li and his team, along with USF Professor Jianfeng Cai, PhD, are continuing to perfect the efficiency and antibacterial properties of the supramolecule. While the initial results are very promising, the research team says they are still in the early stages of developing these structures but hope they will lead to a new class of supramolecules capable of treating bacterial diseases in an entirely new way.