Preventing bacterial adhesion on surfaces is a critical research area. Bacterial adhesion on material surfaces is normally the initial step in bacterial proliferation and biofilms formation that present several healthcare as well as environmental concerns. A number of solutions have been explored and implemented majorly based on immobilization of bactericidal elements including metal derivatives, poly(ammonium salts), antibiotics and graphene derivatives. However, these strategies haven’t been effective owing to their limited efficiency, cytotoxicity, and antibiotic resistance.
Essential oils, antibacterial peptides and bacteriolytic enzymes are the emerging natural strategies. These natural compounds have been developed over millions of years making plants and animals develop defense mechanism to fight against pathogen attacks. Unfortunately, for biomedical applications, safety and biological stability concerns cannot be overlooked. To date, a number of peptides have been developed to clinical trials presenting more application opportunities in essential oils.
In view of the current understanding of the hydrophobic interactions and chiral effects at bio-interfaces, and motivated by borneol, a natural product, researchers led by professor Xing Wang from Beijing University of Chemical Technology devoted their attention to implementing borneol to come up with a novel antibacterial material. They also focused on developing an approach for antibacterial adhesion via polymer surface stereochemistry. Their work is now published in ACS Applied Materials and Interfaces.
Borneol-based polymers are central in influencing bacterial senses, therefore, presenting a new surface for antibacterial adhesion. The authors dissolved borneol in tetrahydrofuran and triethylamine and acryloyl chloride added successively obtaining a yellow-brown oil. They extracted the monomer with ether and obtained the final product, borneol acrylate, through filtration and evaporation.
The researchers achieved polymerization by adding ammonium persulfate into a solution of methanol and borneol acrylate obtained. The product obtained was a white solid. The resulting bulk polyborneolacrylate polymer was coated on polymer films and ‘prison break’ experiment set up to investigate the antibacterial adhesion capacity of the borneol-based polymer.
The researchers conducted standard bacteria coincubation tests in a bid to analyze the interactions between the polyborneolacrylate surfaces and bacteria. They used the E. coli and Staphylococcus aureus for the experiment.
Poly(methyl methacrylate), as a control, and other films depending on borneol acrylate were applied to the ‘prison break’ experiment. They were cut into circular rings and fixed onto beef-protein medium. E. coli suspension was added into the ring and cultured at 37 °C. The authors observed and recorded with a camera, the growth of the E. Coli at different times.
Naturally, the researchers observed the expanding growth of the E. coli in the rings. Within the first 12 hours, they observed an E. coli stain, but none touched the edges of the rings. However, after 24 hours the stain covered approximately all inner sections. Therefore, Poly(methyl methacrylate) failed to function as a ‘prison’ to curtail bacterial escape. E. coli colonies moved beyond the control ring.
Fortunately, polyborneolacrylate rings displayed superior control. It was observed that no E. coli had escaped the ‘prison’ after incubation for 48hours whereas white E. coli colonies had grown and expanded out of the control ring and covered a larger space on the Poly(methyl methacrylate). Interestingly, in some cases the resistance capability extended to over 100 hours on a selected polyborneolacrylate rings.
This paper gives a proof-of-concept that the biocompatible polyborneol polyborneolacrylate could be efficient for antibacterial applications. Above all, the concept indicated that polymer surface stereochemistry is an excellent antibacterial adhesion. Therefore, this study will open research and various applications of antibacterial materials in biomedicine.
Lingqiong Luo, Guofeng Li, Di Luan, Qipeng Yuan, Yen Wei, and Xing Wang. Antibacterial Adhesion of Borneol-Based Polymer via Surface Chiral Stereochemistry. ACS Applied Materials and Interfaces, volume 6 (2014), pages 19371−19377.Go To ACS Applied Materials and Interfaces