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Surface modification of electrospun PCL fibers
for enhanced cell adhesion and proliferation
Ahmad Arabi, Emily Boggs, Manan Patel
Senior Project Presentation
14 December 2012
Statement of Purpose
• Polycaprolactone (PCL) is widely used in Tissue Engineering (TE) as
a synthetic polymer
• Use of electrospun PCL nano fibers is growing in TE due to alignment
of fibers and tensile properties
• No protocols exists to modify electrospun PCL fibers to increase the
cell-material interaction
Project Goal:
• To find optimized set of parameters to modify PCL fibers to
improve the cell-material interaction
Polycaprolactone (PCL)
•
•
Synthetic polymer
Biocompatibility
•
•
•
•
Non-toxic degradation byproducts
Poor cell-material interaction
Low cost & easy processability
Slow degradation rate
Polycaprolactone monomers
Biomedical applications:
Drug delivery
•
[http://www.sigmaaldrich.com/materials-science/biomaterials/tutorial.html]
Polycaprolactone (PCL)
• Challenges in Tissue Engineering
• Hydrophobic surface: Water contact angle ~ 82o
• Cells like hydrophilic surfaces: ~50o
• Lacks surface functional groups
Visualization of contact angle on a PCL fiber
Extracellular matrix (ECM)
Functions
• Structural support to
cells
• Signaling functions
• Regulatory functions
In Tissue Engineering
scaffold = artificial ECM
[Tissue Engineering Lecture: “Midterm Review”]
Background
Surface modification methods:
• Immobilization of
Arginine(R)-Glycine(G)-Asparate(D)
peptide (RGD)
[U. Hersel et al. / Biomaterials 2003]
Sodium hydroxide (NaOH)
treatment
•
•
•
Nanotopography
Increase hydrophilicity
Produces functional groups
[Chen, ACS Nano, 2012]
Project Goal
• Find an optimized set of parameters for the modification
technique for enhanced
• cell adhesion
• proliferation
• ECM formation
• Establish modification and characterization protocols
PCL Fibers
Research Plan
Surface Modification
Control
NaOH
RGD immobilization
Surface Characterization
Hydrophilicity
Functional Groups
Cell Seeding and Characterization
3D study
Control Plate
Metabolism studies
Surface Modification
PCL Fibers
Surface Modification
1. NaOH
2. RGD immobilization
Methods: Surface Modification
1. Modification via Sodium Hydroxide
• Breaks the ester bonds of PCL
• Produces carboxylate functional group
• Increases hydrophilicity
• Nanotopography
• NaOH concentrations for 1 and 3 hours
time points
PCL
O
O
NaOH
HO
O
and
O
O
Methods: Surface Modification
2. Modification via RGD peptide
• Immobilization of RGD using 1-ethyl-3-(3dimethylaminopropyl)carbodiimide (EDC) chemistry
• RGD peptide linked to PCL via stable covalent amide
bond
PCL Fibers
Surface Modification
Surface Characterization
Hydrophilicity
Nanotopography
Functional Groups
•
•
•
Goniometer
eSEM
FT-IR, XPS
Methods: Surface Characterization
Contact angle
• Goniometer
• Allows hydrophilicity
evaluation
Expectation
• Improved hydrophilicity
• Water contact angle ~50o
Untreated PCL fiber
Preliminary Study
• 1M NaOH 3 hr treatment
• Contact angle of 46o
PCL fiber treated w/ 1M NaOH for 3 hours
Methods: Surface Characterization
Scanning Electron Microscope (eSEM):
• Detailed visual information regarding morphology of fibers
• Nanotopography
Preliminary study
• Fibers were rougher
PCL nanofibers as
viewed in SEM
Methods: Surface Characterization
Fourier transform Infrared Spectroscopy (FT-IR):
• Evaluates surface chemical composition
• Indicates functional groups present on modified surface
• Amide bonds detected at 1650 and 1530 cm-1
Amide
Bond
[Ghasemi-Mobarakeh,
Mater
Sci Eng, 2010]