Compressive Mechanical Characteristics of Multi-layered Gradient Hydroxyapatite Reinforced Poly (Vinyl Alcohol) Gel Biomaterial

Functional gradient materials provided us a new concept for artificial articular cartilage design with gradient component and gradient structure where one side of the material is high free water content thereby providing excellent lubrication function and the opposite side of the material is high hydroxyapatite content, thereby improving the bioactivity of the material and stimulating cell growth. The goal of the present study was to develop a multi-layered gradient HA/PVA gel biocomposites through layer-by-layer casting method combing with freeze/thaw cycle technology. The various influence factors on the compressive strength and modulus of the multi-layered gradient biocomposites were investigated. The results showed that the compressive mechanical characteristics of the biocomposites were similar to that of natural articular cartilage. Both the compressive strength and modulus of the multi-layered gradient HA/PVA gel biocomposites increased exponentially with the rise of compressive strain ratio. Both the compressive strength and average compressive modulus of the biocomposites improved with the rise of freeze/thaw cycle times and total concentration of HA particles in the biocomposites, but they showed decreasing tendency with the rise of HA concentration difference between adjacent layers.