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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]