Hydrogels for Coating Medical Devices

Hydrogels for Coating
Medical Devices
University of Wisconsin
BME 400
Our Team




Brett Mulawka – Team Leader
Patrick Schenk – Communicator
Benjamin Roedl – BWIG
Darshan Patel - BSAC
Client & Advisor

Client: Arthur J. Coury, Ph.D.
• Vice President Biomaterials Research
Genzyme Corporation

Advisor: William Murphy, Professor of
Biomedical Engineering
Genzyme Corporation

One of world’s foremost
biotechnology companies with the
goal of applying the most advanced
technologies to address unmet
medical needs.
Problem Statement

To form PEG macromer-based
hydrogels on a latex Foley catheter
surface in an interfacial
photopolymerization process and to
screen the coatings for interactions
with cells and media that mimic
physiologic fluids. It is hypothesized
that these coatings will resist fouling
and may be useful for reducing
infections resulting from the use of
urinary catheters.
Motivation
• Our ultimate goal is to coat a urinary
catheter with a uniform hydrogel
with sufficient material adhesion.
We believe that the hydrogel will
improve upon the problems
associated with existing long-term
catheters.
Catheters

Made of various materials
• Latex, PVC, silicon, PTFE (Teflon)

Why focus on catheters?
• Chance of failure 100% within weeks to
months

Catheter obstruction and leakage
• Caused by bacteria and protein buildup

Dependant upon patient and coating
Latex

Our primary material choice
• Most common material for urinary
catheters

Sulfur bridges formed during
vulcanization
Cis
Polyethylene Glycol (PEG)

Properties
• Clear, viscous, odorless, miscible in
water, non-toxic

Uses
• Wound dressing, soft tissue
replacement, drug delivery
Visible Light Initiating System
Na
COO
Br
Br
514 nm
O
O
[Eosin Y]*
+
:N(CH2CH2OH)3
O
Na
Br
Br
Eosin Y
POLYMERIZATION
Macromer
:N(CH2CH2OH)2
+
CHCH2OH
+
COO
Br
Na
Br
O
O
OH
Na
Br
Br
COO
Br
Na
Br
O
O
O
Na
Br
Br
Na
H
Interfacial Polymerization
Last Semester

What we coated
Adhesion of PEG to Substrates Using Eosin Y
• PVC, Polystyrene
and Glass

All showed very
poor adhesion
Why?
• Hydrophilic and
Hydrophobic
interactions
3
Adhesion Score

4
2
1
<1
1
0
PVC
Polystyrene
Glass
Latex
This Semester


Focused on latex
substrates
Modified staining
procedure
• 125ppm Ethyl Eosin
in acetone solution


Hydrophobic stain
Poor adhesion
persisted
Adhesion


We reject our hypothesis that stain
adhesion correlates to hydrogel
adhesion
Why?
• The Eosin molecule does not bind with
PEG hydrogel

Intermediate compounds continue the freeradical reaction and form the covalent bonds
Continued Poor Adhesion
Latex Adhesion Observations
Stain:
Eosin Y
Ethyl Eosin
<1
X
X
X
X
X
X
X
X
Adhesion Strength:
2
3
4
Each X represents a trial.
5
Alter Substrate

Increase porosity of latex
• Stretching when in contact with PEG


Increases surface area for PEG interaction
with substrate
Opens pores on substrate surface
• Allows PEG to interact with crevices
Experiment





Stain latex with Ethyl Eosin solution
Rinse with acetone
Stretch latex and place in PEG
solution overnight
Photopolymerize
Test adhesion
Modified PEG Molecules

PEG has many variations of end chains
• Hydrophobic
• Hydrophilic

Also could use “block” polymer
• PEG--PLA--PEG
Experiment




Stain latex with Ethyl Eosin
Rinse with acetone
Place in modified PEG solution and
polymerize the monomer
Test adhesion
Covalent Link

Use chemical reaction to form
covalent bond between PEG and
latex
• PEG molecule with a sulfhydryl end


Similar to vulcanization process used to
form latex bonds
Cons to covalent link
• Need to find safe chemical reaction
• Reaction could be difficult to run
Experiment






Stain latex with Ethyl Eosin
Rinse with acetone
Place in PEG solution
Run chemical reaction to covalently
bond PEG to substrate
Polymerize PEG monomer
Test adhesion of macromer
Future Work

Once strong gel adhesion to the
substrate is established…
• Modify procedure to obtain homogenous
thickness under 100 microns

Want it thin enough to restrict entry of
bacteria
• Test PEG coated latex for protein
interaction

Minimize protein adhesion
• Test with common plasma protein: albumin
Thank you
Questions?