In vitro degradation and mechanical properties of PCL/HAp scaffold tested with PeakForce Quantitative NanoMechanics AFM Adrian Chlanda1, Michal J. Wozniak1,2, and Krzysztof J. Kurzydlowski1 1. Faculty of Materials Science and Engineering – Warsaw University of Technology, Warsaw, Poland 2. University Research Centre – Functional Materials, Warsaw University of Technology, Warsaw, Poland
Abstract An increasing interest in porous scaffold substitutes for bone replacement has arisen in recent years. This kind of material does not need to be removed with additional surgery after bone repair. One of the most widely used degradable materials is polycaprolactone (PCL). PCL can be fabricated into porous scaffold, which play an important role in bone repair by supplying space for bone cell growth and differentiation both in vitro and in vivo. The ideal bone substitute material should possess osteoconduction, mechanical properties similar to those at the bone and cartilage repair sites. Weak mechanical properties of porous polymer scaffold limit the applications. To improve the mechanical properties for bone repair and provide a better environment for cell attachment and proliferation, bioceramics is usually considered as fillers or coatings. In this research, PCL and hydroxyapatatite (HAp) were mixed to compose a porous scaffold. HAp as a reinforced phase, can improve the mechanical properties and osteoconduction of composite. The aim of this study was to determine the changes in mechanical properties of scaffold in the nanoscale during in vitro degradation. For this purpose novel atomic force microscopy technique – Peak Force Quantitative NanoMechanics was implemented.
Peak Force Quantitative NanoMechanics 1
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Average reduced Young`s modulus[MPa]
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1. 3D topography reconstruction of pure PCL tissue engineering scaffold, 2. Topography of HAp particles used as reinforcement, 3. Reduced Young`s modulus map of PCL/HAp scaffold before degradation, Reduced Young`s modulus map of PCL/HAp scaffold after one (4), two (5), three (6), four (7), five (8), and six (9) months of in vitro degradation, 10. Average value of reduced Young`s modulus value calculated with the DMT (Derjaguin Muller Toporov) model: Where: F is the force acting on the cantilever,Fadhadhesion force between probe and the surface,R is the tip radius, d-d0 is the sample deformation, and E* is the reduced Young`s modulus.
Conclusions Based on obtained results, it can be stated that polycaprolactone-based tissue engineering scaffolds are characterized by stable mechanical properties at the nanoscale. Average value of reduced Young's modulus, determined by novel PeakForce Quantitative NanoMechanics atomic force microscopy technique remained constant during the half year scaffold degradation.
Acknowledgement The work was supported by: National Science Center of Poland under grant UMO-2011/01/B/ST8/07559
Contact E-mail address: adrian.chlanda@inmat.pw.edu.pl Website: www.bio.materials.pl