1. Antibacterial Polyelectrolyte Multilayers (PEMs) Team X Maricela Delgadillo Kay Furman Yushan Kim

2. Industrial Application Implantable Medical Devices:  Pacemakers treat Bradycardia (slow heart rhythm) Size: 45x48x8  Defibrilators treat Tachyarrhythmia (fast heart rhythm) Size: 62x51x15mm Potential for Bacterial Exposure  6% of all vascular surgeries result in surgery site infection (Health Protection Agency)  Packaged and handled sterilely  1-2 hr surgical procedure Images from http://www.medtronic.com/

3. Brief PEM Background Layer-by-layer fabrication  Polycation - Poly(allylamine hydrochloride) PAH  Polyanion - Poly(acrylic acid) PAA  Easy to control pH and number of bilayers Polyelectrolyte pH affects:  Film Thickness  Interpenetration between layers Highly ionized polyelectrolytes (pH~6.5) result in thin films  Possible cell adhesion applications pH~3.0 loopy conformations

4. Project Plan Desired property Desired timescale Material selection Validation BacteriocidalHoursIncorporation of active: peptide? e.g. cecropin No Staphylococcus epidermidis growth Promote epithelial cell attachment Min. days/weeks Film of high stiffness Supports fibroblast seeding sepidermidis.mlst.net/ Berg, 2000

5. PEM Design TiO 2 substrate: + charge 1 st PEM layer: PAA PAH/PAA bilayers Incorporation of antibacterial active by use of electrostatic charge Other design considerations  Porosity  Cross-linking

6. Project Plan Coat PEMs onto Ti sheet substrates  TiO 2 has pos. charge; basal PAA layer Selectivity of cell interaction  PEM which promotes cell adhesion to encourage engraftment: test by fibroblast seeding  Addition of antibacterial properties by other functionalities (nanoparticle, etc): test by Staphylococcus epidermidis seeding Stability testing

7. Potential Material Issues Metal substrate and PEM processing  Titanium use in implantable devices  Previously published studies with metal PEM on device stimulation electrodes (Patent 5964794, 1999) PEMs for corrosion-resistant metals (Patent 027011, 2003)  Necessitates (-) PAA layer deposition first Imaging Issues  Microscopy requires transparent substrate  TEM or SEM availability Ti disk Staph aureus

8. Further Issues and Questions Feasibility of bacteria/eukaryote selectivity