Mechanical characterization of surface modified scaffolds

• Main Author: Koh, Marc Zhen Yang.
• Other Authors: Leong Kah Fai
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Mechanical engineering::Surgical assistive technology
• Online Access: http://hdl.handle.net/10356/50098
• Institution: Nanyang Technological University

This project is to investigate surface modifications of Polycaprolactone (PCL) scaffold to improve the biocompatibility with human cancellous bone cells. It describes the use of rapid prototyping techniques, focusing on selective laser sintering fabrication. Selective laser sintering uses carbon dioxide laser for powder fusion, without the need for a binder. Prior to fabrication, a design process using Computer-aided Design system, CAD was involved in the project to configure scaffold model. The platform used is Pro/ENGINEER Wildfire with a modular scaffold library, namely Computer Aided System for Tissue Scaffolds (CASTS). By setting parameters in CASTS, desired scaffold design can be obtained. The surface modifications that were studied consists of alkaline treatment with sodium hydroxide, (NaOH) solution and Poly (vinyl alcohol), (PVA) surface treatment. Thus 3 category of treatments were investigated, the untreated PCL material, PVA(5)-PCL material and NaOH PCL material. 3 different shapes of scaffold models were fabricated according to experiments prerequisite. A 40 mm x 40 mm x 2 mm flat model was made for surface roughness testing. Another fabrication is a 12.7 mm x 12.7 mm x 25.4 mm scaffold model to be subjected to compressive testing. Last of all is a 10 mm x 10 mm x 5 mm cuboid for contact angle measurement. Various experimental methods were designed to perform comparison test on the different surface treatments on PCL scaffolds. For surface roughness testing, SJ-301 surface roughness tester was used by the author. The Ra values of all specimens were recorded and analyze. Next in compressive test section, Instron Universal Tester 5569 is used to measure compressive stress and compressive strain of the scaffolds. Finally for contact angle measurement, the Attension Optical Tensiometer was the equipment used to obtain contact angle of water droplets on the specimens. It was analyzed for the hydrophilicity degree of the materials. From all the results collected, material selection was performed to choose the most suitable treatment method. Results of different scaffold materials were analyzed to match with properties of human cancellous bone. Untreated PCL material possesses average surface roughness of 9.53 μm, yield strength of 3.25 MPa, stiffness of 23.80 MPa and hydrophobic nature with an average contact angle of 120.70°. PVA(5)-PCL results show that it has average surface roughness of 9.80 μm, yield strength of 3.40 MPa, stiffness of 25.05 MPa and hydrophilic nature with an average contact angle of 23.50°. NaOH PCL displays results with average surface roughness of 9.79 μm, yield strength of 3.45 MPa, stiffness of 23.80 MPa and a very hydrophilic nature with an average contact angle of 7.08°. In conclusion PVA(5)-PCL demonstrated properties that appeared most suitable for human cancellous bone requirement.