This paper presents the course of synthesis and the properties of biodegradable terpolymers obtained by ROP of L-lactide with glycolide, catalysed with zirconium(IV) acetylacetonate and conducted in the presence of a macroinitiatortrimethylene carbonate oligomers terminated with hydroxyl groups. The oligomers were also prepared by ROP reaction of TMC catalysed by zinc(II) acetylacetonate monohydrate in the presence of polyols as initiators. Depending on the type of initiator used, the oligomers had a linear or branched structure of the chain with different hydroxyl end-groups. Some of the obtained oligomers formed a network. The effect of the terpolymer chain structure on mechanical and thermomechanical properties as well as shape-memory behaviour was shown. The ability to control the speed of return from a temporary to a permanent shape, the value of stress of return triggered by this phenomenon, and the magnitude of the temperature range in which the phenomenon took place through appropriate selection of conditions for programming the temporary shape or/and terpolymer chain microstructure has been shown. The possibility of adjusting these parameters as presented in this paper is vital in the process of designing a bioresorbable material, which can be used for forming selfexpanding stents or self-clamping surgical staples.
The aim of the presented study was preparation, analysis of properties, and in vitro characterization of porous shape-memory scaffolds, designed for large bone defects treatment using minimally invasive surgery approach. Biodegradable terpolymers of l-lactide/glycolide/trimethylene carbonate (LA/GL/TMC) and l-lactide/glycolide/ε-caprolactone (LA/GL/Cap) were selected for formulation of these scaffolds. Basic parameters of shape memory behavior (i.e. recovery ratio, recovery time) and changes in morphology (SEM, average porosity) and properties (surface topography, water contact angle, compressive strength) during shape memory cycle were characterized. The scaffolds preserved good mechanical properties (compressive strength about 0.7 to 0.9 MPa) and high porosity (more than 80%) both in initial shape as well as after return from compressed shape. Then the scaffolds in temporary shape were inserted into the model defect of bone tissue at 37°C. After 12 min the defect was filled completely as a result of shape recovery process induced by body temperature. The scaffold obtained from LA/GL/TMC terpolymer was found the most prospective for the planned application thanks to its appropriate recovery time, high recovery ratio (more than 90%), and cytocompatibility in contact with human osteoblasts and chondrocytes.
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