Transcript NSF Grantees Meeting 12/4/07

NIRT: Self-Assembled Nanohydrogels for
Differential Cell Adhesion and Infection Control
Matthew Libera, Woo Lee, Svetlana Sukhishvili, Hongjun Wang, and Debra Brockway
Stevens Institute of Technology, Hoboken, New Jersey 07030
Project Overview
Infection: A Major Mode of Orthopaedic Implant Failure
Infection occurs in approximately 0.5 – 5% of all hip and knee replacements.
It is a catastrophic problem, because bacteria that colonize an implant surface develop
into biofilms where they are as much as 10,000 times more resistant to antibiotics than
planktonic bacteria. The most effective therapy is to remove an infected implant, cure
the infection, and then pursue a subsequent revision surgery. The consequences to
patient well being and medical cost in this situation are compellingly significant.
Infection Rates
 Hips
Biologics
$1.0, 23%
This project explores a new
mechanism to create differentially
adhesive surfaces. We hypothesize
that heterostructures of nanosized
hydrogels self assembled in 2D
over micrometer length scales will
allow focal contact formation and
subsequent osteoblast adhesion
but prevent bacterial adhesion.
Bacterial biofilms form complex and
hierarchically structured communities
which are as much as 10kx more resistant
to antibiotics than planktonic bacterial.
0.3 - 1%
Knees
At its core, implant infection is a biomaterials problem. While surfaces have
been developed which repel bacterial adhesion – e.g. PEGylated surfaces – these also
repel the eukaryotic cells necessary for the development of a healthy implant-tissue
interface. Instead, surfaces are needed that are differentially adhesive, i.e. that it
promote eukaryotic (e.g. osteoblast) adhesion and proliferation while simultaneously
repelling bacteria. This is a
Global Orthopaedic Markets (2005)
fundamental biomaterials problem
that remains unsolved.
BGS
$.4, 5%
1 - 4%
Fixation devices
~2 mm
attachment
• S. aureus (40%)
Hips
$4.0, 9%
Polysaccharide
secretion
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-
-
-
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• S. epidermis (20%)
adapted from Sauer, Genome Biology, 2003)
substrate
Sports Medicine
$1.0, 9%
Bone Cement
$0.3, 7%
Arthroscopy
$1.0, 8%
Multiplexed Microfluidic Methodology for
Evaluation of Differential Adhesion
Ancillary
$2.0, 10%
Source: Merrill Lynch
Courtesy of G. Grobe
DePuy Orthopaedics
Emulsion
Polymerization
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Broader Impact: A Partnership to Introduce
Nanotechnology Research in High School Classrooms
S. epidermidis
Therapeutic Delivery/
Host defense mechanism
Goals of the Outreach Effort
Protein Conditioning
- Expose high school students to
nanotechnology-based research
- Demonstrate societal relevance
- Enhance and modernize topics taught in
standard high school biology and chemistry
Objective
Lens
PEGDA, AA,
photo initiator
and DCM
Relevant Biomaterial/
Engineered Material
Add DI water
during stirring
Glass substrate
Prototype device bonded to glass
Attributes of the Module
Osteoblasts before S. epidermidis inoculation
20x
Sonicate for 30
min in darkness
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+
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- Ease of implementation
Year
in biology and chemistry courses
1
- Minimal time requirement for implementation
- Contain a hands-on or laboratory activity
Year
2
- Address National Science
Education Standards (NSES)
20x
20x
UV for 15 min
during sonication
Deposition Efficiency
Si
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- -
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-
- - - + + + + + +
- - - - - -
--
-+
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+
-
Si
CMFDA, pre-stained
deposition efficiency of nanohydrogel particles with different time
and concentration
particle number per micron^2
The PLL coated wafer was
then immersed in a
nanohydrogel suspension at
pH 7.4 for electrostatic gel
deposition.
C12-reazurin,
post-stained
MC3T3-E1 osteoblast were seeded (1M/ml M-aMEM) in a prototype
microchannel on a glass slide, cultured at 0.1 l/min flow rate for 24h
0.8
0.7
Year
3
Devices integrated to a
grit-blasted Ti alloy (top),
a polished Ti alloy (middle),
and a glass slide (bottom)
0.5
0.5 hr
3 hr
0.4
Osteoblasts co-cultured with S. epidermidis for 2h under flow
0.3
Implement
small pilot
Implement
larger pilot
Revise draft
modules
Finalize
modules
Dissemination
S. epidermidis
0.2
CMFDA,
pre-stained
0.1
0
0.2
0.4
0.6
0.8
1
nanohydrogel particle relative concentration
C12-reazurin/Sytox,
post-stained
20x
Stevens undergraduate Zareen Mobin
working with Ms. Clare Kennedy from
the Academies@Englewood/
Dwight Morrow High School
1.2
Reduced S. epi Adhesion
Si + PLL
Develop draft
modules
Dr. Ron Schreck from the
Academies@Englewood/
Dwight Morrow High School
and ACS SEED student
Ashley Contreras
0.6
0
Si
self-assembled
nanohydrogels
repulsive
adhesive
Extremities
$0.4, 11%
Osteoblast
-
S. epi
~350 m
polycation primer layer
Trauma
$3.0, 14%
A Si wafer was used as
substrate and hydroxylated by
NaOH. It was immersed in PLL
solution to get a positive
charged PLL primer layer.
+
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osteoblast
Knees
$5.0, 16%
Si
+ +
- -
Release of
planktonic
progeny
Spinal
$4.0, 24%
Self Assembly
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Maturation
and biofilm
growth
The biofilm cycle
vortex
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Cell-Interactive
nanohydrogels
hierarchically structured
on the surface of a
macroscopically beaded
surface of a modern
orthopaedic implant.
> 15%
Infection by
Staphylococcal Biofilms
Electrostatic
-
~1 m
e.g. Intramedullary trauma rods
Nanohydrogel Synthesis and Self Assembly
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Differentially Adhesive Surfaces Repulsive to Bacteria but Attractive to Eukaryotic Cells
Si + PLL + nanohydrogel
SYTO9
MC3T3-E1 osteoblasts were seeded (1M/ml) in a microchannel on a glass
slide, cultured in M-aMEM at 0.1 l/min flow rate for 24h, and then
inoculated with 103 CFU/ml S. epidermidis, and cultured for 2h
S. epidermidis, 108 CFU/ml,
5h flow culture in M-aMEM
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