| dc.description.abstract | Layer-by-layer (LbL) assembly has proven to be a powerful technique for
assembling thin films with a variety of properties including electrochromic, molecular
sensing, oxygen barrier, and antimicrobial. LbL involves the deposition of alternating
cationic and anionic ingredients from solution, utilizing the electrostatic charges to
develop multilayer films. The present work incorporates cationic antimicrobial agents
into the positively-charged layers of LbL assemblies. When these thin films are exposed
to a humid environment, the antimicrobial molecules readily diffuse out and prevent
bacterial growth. The influence of exposure time, testing temperature, secondary
ingredients and number of bilayers on antimicrobial efficacy is evaluated here.
Additionally, film growth and microstructure are analyzed to better understand the
behavior of these films.
The antimicrobial used here is a positively-charged quaternary ammonium
molecule (e.g. cetyltrimethylammonium bromide [CTAB]) that allow assemblies to be
made with or without an additional polycation like polydiallyldimethylamine. While
films without this additional polymer are effective, they do not have the longevity or uniformity of films prepared with its addition. All of the recipes studied show linear
growth as a function of the number of bilayers deposited and this growth is relatively
thick (i.e. > 100 nm per bilayer). In general, 10-bilayer films prepared with CTAB and
poly(acrylic acid) are able to achieve a 2.3 mm zone of inhibition against S. aureus
bacteria and 1.3 mm against E. coli when test are conducted at body temperature (i.e.
37oC). Fewer bilayers reduces efficacy, but lower test temperatures improve zones of
inhibition. As long as they are stored in a dry atmosphere, antimicrobial efficacy was
found to persist even when films were used four weeks after being prepared. The best
films remain effective (i.e. antimicrobially active) for 4-6 days of constant exposure to
bacteria-swabbed plates. This technology holds promise for use in transparent wound
bandages and temporary surface sterilization. | en |
