PemPlant Co. 1 March 8, 2007 Design Review P E M PemPlant Co. Maricela Delgadillo Kay Furman Yushan Kim

PemPlant Co. Project Overview Exploring use of Antibacterial Polyelectrolyte Multilayers (PEMs) on implantible medical devices such as pace makers ▪6% of all vascular surgeries result in surgery site infection (Health Protection Agency) ▪Packaged and handled sterilely ▪1-2 hr surgical procedure Explore the stability of antibacterial properties of PEMs on glass. Develop the glass system on medical grade Ti

PemPlant Co. Experimental Objectives Analyze glass PEM antibacterial properties ▪Currently only experiments across 2 hour time points have been performed ▪Test the stability of antibacterial PEMs at 4 and 8 hour time points Develop and characterize the glass/PEM system on Ti: ▪Stability Testing ◦ In air ◦ In buffer ▪Mechanical testing ◦ Nanoindentation, MFP ▪Bactericidal testing

PemPlant Co. Key Project Accomplishments Administrative Accomplishments ▪All Training Completed ▪Website Completed ▪Link to: Experimental Accomplishments ▪Ti substrates ◦ Purchased and cut (Yin-Lin) ◦ Cleaning method developed ◦ Coated with PAA/PAAm system ▪Completed PEM Formulations: ◦ PAA/PAAm on silane-glass slides ◦ PAA/PAH on silane-glass slides ▪Bacteria inoculation performed Cytophillic biological agent selected (RGD)

PemPlant Co. Further exploring glass PEM Antibacterial Properties PEM CompositionGlass Substrate PAH/PAA, 2.0/2.0 PAAm/PAA, 3.0/3.0 Will PEMs continue to display antibacterial properties at across longer time points? Staph. Epidermidis 4 h, and 8 h incubations Microscopy PAAm=Polyacrylamide

PemPlant Co. Developing PEMs on Ti PEM CompositionTi Substrate in Air (shelf-life) Ti Substrate in Buffer (in vitro) PAA/PAH 2.0/2.0 PAAm/PAA 3.0/3.0 Test duration 2 wks-1 mo Ti PEM stability/mechanical properties unknown Visual observation ▪methylene blue binds to carboxyl groups to give visual quantification of the polymer on the sample

PemPlant Co. Film construction Layer-By-Layer dipping technique PAA/PAH 2.0/2.0 ▪9.5 Bilayers (PAA first and last layer) ◦ 15 min dip in polymer PAA (anion) and PAH (cation) ◦ 2,1, and 1 min dip in DI water ▪Crosslink at 80°C for 1 h PAAm/PAA ▪5.5 Bilayers (PAA first and last layer) ◦ 15 min dip in PAAm (cation) and PAA (anion) ◦ 2,1, and 1 min dip in DI water at pH 3 ▪Crosslink at 130°C for 2 hours under vacuum

PemPlant Co. Film Properties PAAm/PAA (pH=3) ▪Prevent Hydrogen bonds from hydrolyzing at a neutral pH ▪Must use low pH to prevent film break up ▪Not stable in water until crosslinked

PemPlant Co. Preparing and Cleaning Ti surface Simple cleaning method acquired from several literature sources ▪Remove organic contaminants ▪Clean surface with acetone ◦ Rub with kimwipe ▪Sonicate in 100% ethanol for 5 minutes XPS and Contact angle test will be used to ensure oxide layer remains on Ti after it is cleaned

PemPlant Co. Anticipated PEM Mechanical Properties Mechanical Data Reference Points: Thompson, Van Vliet, et al. (2005) PAA-terminal PAH-terminal

PemPlant Co. Anticipated Bacterial Response Cell response possibly affected by 1.Mechanical properties 1.fibroblasts prefer stiffer substrates, on the order of 10^8 Pa 2.Surface chemical characteristic 1. cells have a positive surface charge, they stick better to the negative surface charged PAA- topped films (Carboxylates) Data refers to fibroblast, however, unpublished data shows similar trends for bacteria.

PemPlant Co. Previous Phase-Level Gantt Chart Glass PEM, Titanium PEM, Mechanical, Bacterial, Cytophillic PEM, Fibroblast Seeding

PemPlant Co. Design Review Evaluation Considerations Prompting Re-evaluation: ▪Ambitious team goals ▪Initial scheduling of Gantt Implemented Realistic Timeframes with Achievable Goals ▪SMART= specific, measurable, achievable, realistic, time-based Utilized Consultations: ▪Prof. Chiang ▪Todd ▪Mike

PemPlant Co. Design Review Evaluation Revised Phase-Level Gantt Chart: ▪Removed cytophillic experiments ▪Stream-lined several experiments ▪More realistic, achievable time frames

PemPlant Co. Design Review: Team Goals Antibacterial PEM Coatings on Glass ▪Low risk, higher benefit ▪Novel longevity experiments ▪Measurable outcome: 4 h, 8 h antibacterial character Transfer PEM System to Titanium ▪Higher risk, large potential benefit ▪Novel substrate for MIT ▪Provide knowledge-base for Industry ▪Measurable outcome: PEMs on Ti, mechanical characterization

PemPlant Co. Next Steps Upcoming weekend: ▪Inoculate bacteria (prepare for testing) ▪Expose glass PEMs (PAA/PAH and PAAm) to bacteria ▪Take images of 2 h, 4 h exposure Before next presentation: ▪Analyze bacteria experiment results ▪Assess presence of PEMs on titanium

PemPlant Co. Questions? PemPlant, Co. Homepage: ▪ P E M