Biomaterials-associated infection is responsible for the failure of many tissue-contacting biomedical devices and is drawing increasing attention. Many strategies have been explored to resolve this problem. A common approach incorporates antimicrobials by way of adsorption on or covalent grafting to the device surface as well as by controlled release by antimicrobial elution from the surface. We have been exploring microgel-modifications of device surfaces that both inhibit bacterial adhesion and kill bacteria. This study identifies cationic antimicrobials that can be complexed within surface-deposited microgels and sequestered there under physiological conditions to achieve long-term antimicrobial properties. Acrylic-acid based microgels were electrostatically deposited onto poly(lysine)-primed glass substrates, and their response to various buffer solutions was observed by in situ microscopy. The buffers studied sampled various pH and salt concentrations with and without cationic antimicrobials. Microgel deswelling was caused by antimicrobial-microgel complexation. Subsequent antimicrobial release reswelled the microgels. These swelling and deswelling behaviors provide measureable indicators of the microgel-antimicrobial interactions. We studied several antimicrobials to sample size, charge density, and hydrophobicity, all of which influence complexation. Loading from salt-free buffer occurred in times as short as 30 s for small cationic antibiotics, like colistin and amikacin. Larger antimicrobials (e.g. L5 peptide) require ~30 min to load. Antimicrobial sequestration after loading and triggered-release studies used buffers with different ionic strengths and pH. Antimicrobials with lower charge density form stable complexes in low-salt buffers and can be sequestered within the microgels for extended periods of time. But the interactions are weakened by increasing ionic strength, which triggers antimicrobial release. On the other hand, antimicrobials with higher charge density form very stable complexes that remain stable in buffer at physiological pH and ionic strength. These antimicrobials could be sequestered for periods as long as 30 days. Bacterial culture showed these microgel-complexed antimicrobials can act very effectively when challenged by bacteria.

Electrostatic complexation of cationic antimicrobials within anionic microgels

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.