Staphylococcus epidermidis represents the most common source of medical device-related infections usually associated with biofilm formation. Biofilms have the characteristics physiology and architecture to resist many antibiotics and host defense mechanisms.
The aim of the present study is to produce a thin plasma polymeric matrix encapsulated with antibiotic levofloxacin to prevent biofilm formation. The process involved the deposition of amine plasma polymer layer onto Thermanox slides by using n-heptylamine monomer (HA). Drug encapsulation was completed by immersing plasma coated samples in a solution of levofloxacin under standardized conditions. Two solvent systems - 2-(N-morpholino) ethanesulfonic acid (MES) and dimethyl sulfoxide (DMSO) - were used for dissolving levofloxacin. The samples were assessed for biofilm formation by measuring the colony-formation units and also by BacLight (Live/Dead) staining followed by imaging using fluorescence microscopy. In vitro mammalian cell attachment assay was also performed with human embryonic lung (HEL), human foreskin fibroblast (HFF) cell lines and human epidermal keratinocytes, neonatal (HEKn) primary cells. The attached cells were quantified via staining with crystal violet followed by UV Vis measurement (λmax = 595 nm). Release of levofloxacin from polymeric matrices was assessed with the aid of UV Vis spectroscopy (λmax = 285 nm).
Diffusive release of levofloxacin from heptylamine plasma polymer coatings (~ 40nm thickness by ellipsometry) was found to produce concentrations above the minimum inhibitory concentration (MIC) of Staphylococcus epidermidis (ATCC 35984) and it prevented the formation of biofilm on the surface of the coating. There was very little effect of the fabricated antimicrobial coatings on cell attachment. The extraction experiments also indicated that the levofloxacin loading can be controlled by the solvent used.