Free standing collagen films prepared by electrophoretic deposition

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Event Abstract Back to Event Free standing collagen films prepared by electrophoretic deposition David Barrett1, Terance Hart2, Serena Best1 and Ruth Cameron1 1 University of Cambridge, Department of Materials Science and Metallurgy, United Kingdom 2 Geistlich Pharma Ag, Switzerland Introduction: Electrophoretic deposition is a widely used technique in the ceramic industries for forming coatings and structures with reproducible properties and of arbitrary shape and size. It works by applying an electric field to a solid suspension of charge particles. The particles feel the field and experience a force that moves them towards one of the electrodes, which when reached leads to a deposit or film on the surface of the electrode, the properties of which can be set by altering parameters such as the applied field strength and the conductivity of the suspension. Recently there has been interest in the literature towards using the electrophoretic deposition technique with a wider variety of materials such as polymers and biomaterials[1]. In this study we have applied the technique of electrophoretic deposition to proteins to produce films for use in a variety of roles. These films can be removed from the electrodes after deposition and are self-supporting. Materials and Methods: Insoluble collagen I was rehydrated using 0.05M acetic acid and ethanol was added to 50 vol%. The suspension was then homogenised until a smooth consistency was achieved. Stress – strain data was determined by using a TA Instruments Q800 DMA operating in constant tensile stress ramping mode. SEM images were obtained by sputter coating the samples with gold and imaging with a JEOL 5800 LV SEM in secondary electron mode. Deposition was carried out using custom built deposition apparatus and consisted of two 304L steel plates separated by silicone spacers that could be adjusted to change the electrode spacing. The electric field was produced with a TGA1241 Arbitrary Waveform Generator (TTI) and was applied as either a series of pulses of varying length, between 1ms and 1s, or as a continuous. The voltage applied was fixed at 5V. Results and Discussion: Figure 1. Free standing collagen films Figure 1 shows an three films produced by the electrophoretic deposition of collagen demonstrating a range of different sizes and thicknesses of deposited films. They are macroscopically defect free and could be easily separated from the electrodes they were deposited onto. Figure 2. Stress-strain curve for collagen film with 1 or 2 layers Figure 2 shows the reproducible nature of the mechanical properties of collagen films produced by electrophoretic deposition and shows that delamination does not occur between layers deposited onto each other. The average UTS was found to be 47.4±3.3MPa for a single layer and 46.8±3.6MPa for a double layer of collagen. These values are comparable with those for collagen films produced by other techniques such as solvent casting[2]. Figure 3. SEM (left) and AFM (right) images of a collagen film Figure 3 shows representative SEM and AFM images confirming the defect free nature of the films produced. Small features approximately 5μm can be seen where gas bubbles have formed during film formation but the films are smooth overall with an average roughness Rq(RMS)= 287±90nm. Conclusion: This study has shown that electrophoretic deposition can be used as a technique to reliably produce free standing films of collagen rapidly and without macroscopic defects. These films have mechanical properties that match those of films produced by other techniques and can be produced in a range of sizes and thicknesses. They have low surface roughness values and show homogeneous microstructure. The authors would like to thank the EPSRC (Grant no: EP/L504920/1) and Geistlich Pharma AG for providing financial support to this project.