Borosilicate Scaffold Processing for Bone Tissue Engineering

Abstract

Tissue engineering utilizes artificial porous structures, scaffolds, to temporarily replace parts of tissues or organs in order to enhance the healing process. Scaffolds for bone tissue repair should fulfill several structural, mechanical and chemical criteria. Bioactive glasses and biodegradable polymers are typical materials used in scaffold fabrication for bone tissue engineering. Bioactive glasses have remarkable biological performances but suffer from poor mechanical properties and processability. Whereas biodegradable polymers have a wide variety of processing options but generally have low strength and biological activity. In his study, borosilicate glasses were utilized to produce 3D scaffolds. In a first time, the aim was to produce mechanically strong scaffolds without significant crystalline phase which could lead to loss of bioactivity. The reactivity of the scaffolds in aqueous solution was studied in the light of the scaffolds´ morphologies. In a second time, the potential for developing porous glass/polymer scaffolds was investigated. In this study, borosilicate glasses were under investigation and calcium was substituted by magnesium and/or strontium to enhance the hot working domain while providing therapeutic effect. Structures and thermal properties of the glasses were determined. Glass scaffolds were prepared via the porogen burn-off method and robocasting using sintering temperatures enabling viscous flow without significant crystallization. Composite scaffolds were produced using supercritical carbon dioxide processing by adding glass powder to poly(lactide-co-ε-caprolactone) matrix. The scaffolds´ morphologies, mechanical properties and in vitro behavior were analyzed. Based on the results, it was concluded that both magnesium and strontium substitution enhanced the sinterability of the base glass but had a decreasing effect on reactivity. Utilized production methods yielded promising scaffold morphologies that seemed to be suitable for clinical applications. Robocasted scaffolds were found to have slightly higher reactivities than the scaffolds produced via porogen burn-off method, which was suspected to be due to higher interconnectivity of the pore network. Addition of glass particles into polymeric matrix was found to promote the polymer´s biological properties.