A study by Professor Svetlana Sukhishvili and her collaborators was recently featured in the "Editors’ Choice" section of Science Magazine. The prestigious publication is one of “the world's leading outlet for scientific news, commentary, and cutting-edge research.” It claims the largest paid circulation of any peer-reviewed general-science journal.
The work is the first to report a bioactive material that securely retains antibiotics in the absence of bacteria and acts only when bacteria arrive. The novel and highly efficient drug-delivery film is designed to prevent bacterial infections in biomedical implants, said Sukhishvili, Professor in the Department of Chemistry, Chemical Biology and Biomedical Engineering.
“We were aiming to develop a ‘smart’ coating which delivers antimicrobial agents only where and when needed,” said Sukhishvili. ‘Smart’ coatings support localized delivery of drugs and elute them on demand in response to external stimuli, therefore reducing side effects and enhancing the efficacy of therapeutic treatment.”
The new biomaterial was developed to lower the risk of infection that often occurs in orthopedic implant procedures. Such infections result from bacteria attaching to the surface of implant devices, where they can propagate, said Matthew Libera, Professor and Associate Dean of Engineering and Science and co-author of the study.
“Infection has become the leading failure mechanism of many biomedical implants,” said Libera. “If we can reduce the number of infections, we will improve patient well-being and relieve a costly burden to the health-care system.”
The secret to the clever mechanism of the new coating is that it can be activated by a biological trigger. The material doesn’t release antibiotics under normal physiological conditions. However, in the presence of bacteria, the pH of the local environment decreases, and this change activates the delivery of the drug.
“While other groups including ours reported that ‘smart’ coatings could be activated by external stimuli, such as pH or electric field, these physical stimuli were not linked to bacterial metabolism, and bacteria-triggered pH changes had not been used to activate a ‘dormant’ material containing a drug,” said Sukhishvili.
This development is a major breakthrough, said Athula Attygalle, Research Professor in the Department of Chemistry, Chemical Biology and Biomedical Engineering and co-author of the study. “There are many drug patches and other similar devices that constantly release their active ingredients,” said Attygalle, “The coatings described here release antibiotics only when pathogenic bacteria are present.”
The new ‘smart’ coating is made by combining tannic acid - a natural substance with antitumor, antibacterial, antimutagenic and antioxidant properties - with clinically relevant antibiotics - small molecules whose retention within biomaterials has been hard to achieve.
The next step for the team is to test the efficiency of the coated biomaterials in vivo. The researchers envision that their methodology can be extended beyond the proposed coatings on biomedical implants. By modifying the chemistry of the coatings, it might be possible to create a variety of biodefensive materials and garments.
The findings were first reported in the journal ACS Nano, in a study titled “Self-Defensive Layer by-Layer Films with Bacteria-Triggered Antibiotic Release” The first author is Iryna Zhuk, a graduate student in the Department of Chemistry, Chemical Biology and Biomedical Engineering. Other co-authors are Freneil Jariwala, a graduate student in the Department of Chemistry, Chemical Biology and Biomedical Engineering; and Yong Wu, a graduate student in the Department of Chemical Engineering and Material Science.