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Additive manufacturing of bioactive composites for tissue engineering

Abstract

The increase in life expectancy and trauma caused by accidents has led to a growth in the number of interventions for bone repairs and motivated the development of new materials for application in bone tissue engineering, with emphasis on the development of scaffolds capable to mimic the natural extracellular matrix of bone to enable the connection, proliferation and differentiation of cells. One way to obtain bioactive scaffolds is the production of biocompatible and bioabsorbable polymer-based composites (such as poly(lactic acid), PLA) with bioactive fillers. Conventional composite production techniques usually employ high temperatures and shear rates, and a severe degradation of the polymer matrix can be triggered when ions released by the bioburden interact during the mixing process. The control of the molar mass of the polyester matrix can be carried out through surface treatment of the fillers or the use of a chain extender. The addition of this compound modifies the viscoelastic behavior of the matrix, making it feasible to process the composite by extrusion-based methods, such as additive manufacturing. Another way to control matrix degradation is by reducing the surface area of charge/matrix contact and the exposure time of the molten polymer to the bioactive fillers, using the filler in the form of continuous fibers. In this project, hybrid fiber-particulate composites will be developed. The polymer matrix will be based on PLA composites with bioactive fillers, such as bioglasses, zinc oxide (ZnO), hydroxyapatite (HA), ²-tricalcium phosphate (²-TCP) or magnesium (Mg), with or without surface treatments and use of chain extenders. The particulate composite will cover continuous bioglass fibers and the filaments will be obtained through the extrusion process to cover wires. Scaffolds of polymer matrix/bioactive fiber will be obtained by additive manufacturing. Since length, concentration and fiber orientation influence composites characteristics, modulations of mechanical properties can be obtained in order to simulate the behavior of bones that have spongy and compact regions, through 3D printing of structures containing continuous and particulate fibers (in the matrix composite), being the printing of filaments with continuous fibers and the modulation of the properties the main challenges of the project. The mechanical, morphological, thermal and biological properties of the scaffolds will be fully characterized. Therefore, bioactive scaffolds will be obtained with controlled morphology and that could be applied to tissue engineering. (AU)

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