Naphthalene-Dipeptide Hydrogels Destroy Antibiotic-Resistant Bacterial Biofilms

Novel hydrogels derived from self-assembling dipeptides conjugated to naphthalene were shown to dissolve bacterial biofilms, which indicated considerable promise for use in constructing bacteria-resistant nanomaterial structures, biomaterials, and drug delivery devices.

Biofilm bacteria, which thrive on the surfaces of implants and catheters, are a major medical problem, as they are highly resistant to current therapeutic strategies. To correct this problem, investigators at Queen's University (Belfast, United Kingdom) introduced a novel form of hydrogel based on ultrashort cationic self-assembled peptides bound to naphthalene.

Results published in the July 28, 2014, online edition of the journal Biomacromolecules revealed that lysine-conjugated variants displayed the greatest potency with 2% NapFFKK (K is the abbreviation for lysine) hydrogels significantly reducing viable Staphylococcus epidermidis biofilm by 94%. Cytotoxicity assays against murine fibroblast (NCTC 929) cell lines confirmed that the gels possessed reduced cytotoxicity towards eukaryotic cells and caused only limited hemolysis of equine erythrocytes.

First author Dr. Garry Laverty, pharmacy lecturer at Queen's University, said, "When bacteria attach to surfaces, including medical implants such as hip replacements and catheters, they produce a jelly-like substance called the biofilm. This protective layer is almost impossible for current antibiotics to penetrate through. Therefore bacteria deep within this protective layer are resistant as they remain unexposed to the therapy. They grow and thrive on surfaces to cause infections that are very difficult to treat. The only option is often to remove the medical implant leading to further pain and discomfort for the patient. Our gels would prevent this. Our gels are unique as they target and kill the most resistant forms of hospital superbugs. It involves the use of gels composed of the building blocks of natural proteins, called peptides, the same ingredients that form human tissue. These molecules are modified slightly in the laboratory to allow them to form gels that will rapidly kill bacteria."

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