Polymer bilayers with a two stage defense mechanism (first stage defense: contact killing or bacterial adhesion prevention by outer polymer layer; second stage defense: pH-responsive release of antibiotics from inner polymer layer) against bacterial infection were proposed.  Chitosan (CH), possessing inherent antibacterial and biocompatible properties, and poly(acrylic acid) (PAA), electrostatically interacting with antibacterial cationic drugs, were proposed as the outer and inner layers, respectively.  To synthesize the polymer bilayers, the PAA brush layer was synthesized via surface initiated atomic transfer radical polymerization, by followed by grafting CH onto the PAA brush via Sulfo-N-hydroxysuccinimide ester funtionalization of acrylic acid of the PAA brush and quenching with NaOH solution (pH 8).  The CH/PAA bilayer was characterized using in-situ spectroscopic ellipsometry.  The resultant CH/PAA polymer bilayer exhibited fast, fully reversible pH-dependent swelling and contraction. Studies of pH-dependent swelling showed that the thickness and percent water content of the CH (outer) layer decreased with increasing pH, whereas the thickness and percent water contents of the PAA (inner) brush layer increased.  Antibiotic loading into, and release from the CH/PAA bilayer will be evaluated as a model system with a two stage defense strategy.

In-situ pH dependent swelling studies of polymer bilayers: Chitosan grafted onto a poly(acrylic acid) brush

246th National Meeting (2013)

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