ROLE OF MESENCHYMAL MULTIPOTENT STROMAL CELLS IN REMODELING OF BONE DEFECTS

Ability of mesenchymal multipotent stromal cells (MSCs) to differentiate into several types of mesenchymal tissues allows to consider these cells the main candidates for creating tissue engineering constructions for regenerative medicine. MSCs promote integration of bio-implants into the native bone and stimulate osteogenesis. MSCs are characterized by immunomodulatory properties, due to inflammation control and modification of immune cells. MSCs affect not only the in vivo immune response by preventing immunological rejection of implanted tissue engineering designs, but it can also influence the bone tissue immunity. MSCs play an important role in bone regeneration, by regulating the osteoblastic generation, and suppressing activity of inflammation effectors and osteoclastogenesis. Some pre-clinical and first clinical trials of bone bio-implants colonized with MSC, demonstrate promising outlooks for this strategy in order to obtain tissue engineering constructions for bone regeneration

Probing the complex thermo-mechanical properties of a 3D-printed polylactide-hydroxyapatite composite using in situ synchrotron X-ray scattering

Polylactide (PLA)-hydroxyapatite (HAp) composite components have attracted extensive attentions for a variety of biomedical applications. This study seeks to explore how the biocompatible PLA matrix and the bioactive HAp fillers respond to thermo-mechanical environment of a PLA-HAp composite manufactured by 3D printing using Fused Filament Fabrication (FFF). The insight is obtained by in situ synchrotron small- and wide- angle X-ray scattering (SAXS/WAXS) techniques. The thermo-mechanical cyclic loading tests (0–20 MPa, 22–56 °C) revealed strain softening (Mullins effect) of PLA-HAp composite at both room and elevated temperatures (50 °C) due to the increased chain mobility. Above this temperature the deformation behaviour of the soft PLA lamella changes drastically. The thermal test (0–110 °C) identified multiple crystallisation mechanisms of the PLA amorphous matrix, including reversible stress-induced large crystal formation at room temperature, reversible coupled stress-temperature-induced PLA crystal formation appearing at around 60 °C, as well as irreversible heating-induced crystallisation above 92 °C. The shape memory test (0–3.75 MPa, 0–70 °C) of the PLA-HAp composite demonstrates a fixing ratio (strain upon unloading/strain before unloading) of 65% and rather a ∼100% recovery ratio, showing an improved shape memory property. These findings provide a new framework for systematic characterisation of the thermo-mechanical response of composites, and open up ways towards improved material design and enhanced functionality for biomedical applications

Artificial muscles based on coiled UHMWPE fibers with shape memory effect

Ultra-high molecular weight polyethylene (UHMWPE) fibers drawn at drawing ratio of 6 (pre-deformation strain 500%) demonstrating the obtained one-way shape memory effect. Artificial muscles have been manufactured in the form of coiled UHMWPE fibers. Isometric recovery stress and recovery strain of the fibers were measured during heating by using a dynamic mechanical analyzer (DMA). As a result, the fibers were capable to demonstrate large contraction of 78% (recovery strain of 93%) due to the entropic elasticity. The recovery stresses of the fibers reach up to 27 MPa. The work of stroke cycle for coiled artificial muscles with a constant stress of 1 MPa was recorded. Artificial muscles based on coiled UHMWPE fibers have a large stroke of 64 %. The structural mechanisms of muscle-like behavior were discussed