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E. P. M. PemPlant Co. March 8, 2007 Design Review. Maricela Delgadillo Kay Furman Yushan Kim. Project Overview. Exploring use of Antibacterial Polyelectrolyte Multilayers (PEMs) on implantible medical devices such as pace makers

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pemplant co

E

P

M

PemPlant Co.

March 8, 2007

Design Review

Maricela Delgadillo

Kay Furman

Yushan Kim

PemPlant Co.

project overview
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
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
Key Project Accomplishments
  • Administrative Accomplishments
    • All Training Completed
    • Website Completed
    • Link to:http://web.mit.edu/3.042/team1_07/Website/Website/
  • 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
Further exploring glass PEM Antibacterial Properties
  • 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
Developing PEMs on Ti
  • 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
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
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
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
Anticipated PEM Mechanical Properties
  • Mechanical Data Reference Points:

Thompson, Van Vliet, et al. (2005)

PAA-terminal

PAH-terminal

PemPlant Co.

anticipated bacterial response
Anticipated Bacterial Response
  • Cell response possibly affected by
    • Mechanical properties
        • fibroblasts prefer stiffer substrates, on the order of 10^8 Pa
    • Surface chemical characteristic
        • 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
Previous Phase-Level Gantt Chart
  • Glass PEM, Titanium PEM, Mechanical, Bacterial, Cytophillic PEM, Fibroblast Seeding

PemPlant Co.

design review evaluation
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 evaluation1
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
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
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

E

P

M

Questions?
  • PemPlant, Co. Homepage:
    • http://web.mit.edu/3.042/team1_07/Website/Website/

PemPlant Co.