The objective of this study was to design a partly-degradable scaffold to repair cartilage defects. The scaffold, based on poly(vinyl alcohol), PVA, was intended to maintain long-term mechanical integrity and to facilitate cell proliferation via bioactive agent release from contained microparticles, made from either alginate, ALG or poly(lactic-co-glycolic acid), PLGA. The aim of this study was to characterize the morphological features and mechanical behaviour of composite scaffolds as a function of microparticle type and percent content. Our hypothesis was that the dynamic mechanical properties (Dynamic Modulus and Phase Angle) of the composite scaffold would not be affected by microparticle type, but that Dynamic Modulus would increase as a function of increased microparticle content. Scanning Electron Microscopy confirmed that the manufacturing process homogenously dispersed microspheres within the scaffolds. For pure PVA samples Dynamic Modulus ranged from 66±3 kPa at 0.01 Hz to 83±3 kPa at 50 Hz. As ALG microsphere content increased from 25% to 75%, Dynamic Modulus ranged from 92±5 kPa at 0.01 Hz to 153±19 kPa at 50 Hz. As the microsphere content increased from 25% to 75% PLGA, Dynamic Modulus ranged from 85±9 kPa at 0.01 Hz, to 157±16 kPa at 50 Hz. As expected, Dynamic Modulus increased with increasing test frequencies. For pure PVA specimens Phase Angle ranged from 4.3±0.8 degrees at 0.01 Hz to 12±1.2 degrees at 50 Hz. Phase Angle was not affected by microsphere content. In conclusion, the addition of microspheres affected the dynamic mechanical behavior, in particular Dynamic Modulus, of PVA scaffolds. However, the dynamic mechanical properties were not affected by the polymer from which the microspheres were manufactured. These findings suggest that microsphere type can be chosen to optimize the inclusion of bioactive factors, without detrimentally affecting the mechanical properties of the composite scaffold. It also suggests that % content of included microspheres can be used to modulate the mechanical properties of the scaffold at time zero.

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