Researchers Use 3D Printing-Guided Method to Create Thermoresponsive Nanohybrid Scaffolds https://ift.tt/2Dsuho8 3D printed medical implants are typically stiffer and stronger than the surrounding tissue, and while they don’t always adapt well to biological and physical stimuli, that stiffness is important. The biological processes of our bodies are naturally dynamic, and many researchers are working to ensure that 3D printed implants are of the highest quality and will work well within the human body. Living tissues constantly remodel in response to changes. In particular, changes in cellular and extracellular matrix (ECM) stiffness are important to many pathological and physiological processes, like migration, cell motility, and stem cell differentiation. But scientists don’t quite understand the biomechanical factors that are instrumental in soft tissue development and maintenance. That’s why we hear so often about tissue engineering – combining cells with scaffolds, 3D printed or otherwise, to fabricate a self-sustaining tissue replacement. In a new paper, titled “Stiffness memory nanohybrid scaffolds generated by indirect 3D printing for biologically responsive soft implants,” a collaborative team of researchers from University College London, Brunel University London, and the Royal Free London NHS Foundation Trust developed thermoresponsive poly(urea-urethane) (PUU) nanohybrid scaffolds, with stiffness memory, using a 3D printing-guided, thermally induced phase separation (3D-TIPS) method.
While the controlled elastic modulus of several responsive polymeric materials for tissue engineering have been used as a model for studying stiffness effects in cell cultures, their combined elasticity and molecular structural change coupling effect does not have a wide range of tuneable stiffness. But block-copolymers, like polyurethane (PU) elastomers, have many tuneable properties without having to change their molecular structure – the method of self-assembly just needs to be switched up. When used in long-term implantable cardiovascular devices, PUU has previously demonstrated excellent biocompatability, biostability, compliance, and fatigue resistance, and some PUs even have shape memory. By using materials that are responsive to stimuli, it’s possible to print dynamic 3D structures that can transform their shapes or behavior – like stiffness.
The team used AutoCAD 2014 to design 3D printable polyvinyl alcohol (PVA) preforms for the manufacturing and characterization of PUU-POSS scaffolds, before exporting the STL files into Slic3r software, “where they were sliced into an array of consecutive 200μm layers” for versatile, cost-effective 3D-TIPS indirect printing.
The team used its 3D-TIPS indirect printing technique to manufacture a body temperature-responsive, bespoke tissue scaffold out of a PUU-POSS nanohybrid elastomer solution, which was confined inside a scalable, 3D printed, interconnected PVA preform network. The team produced 3D scaffolds with uniform, identical macroscopic dimensions and polymer content, but variable cellular and biomechanical properties, by thermally controlling PUU solution coagulation and micro-phase separation of polymer chains within the network.
No matter what the initial stiffness was at various thermal process conditions, the PUU-POSS scaffolds made with the team’s 3D-TIPS method would ‘remember’ to relax into their hyperelastic rubber phase once they’d reached the melting temperature of the soft segments.
Co-authors of the paper are Linxiao wu, Jatinder Virdee, Elizabeth Maughan, Arnold Darbyshire, Gavin Jell, Marilena Loizidou, Mark Emberton, Peter Butler, Ashley Howkins, Alan Reynolds, Ian W. Boyd, Martin Birchall, and Wenhui Song. Discuss this research and other 3D printing topics at 3DPrintBoard.com or share your thoughts in the comments below. Printing via 3DPrint.com | The Voice of 3D Printing / Additive Manufacturing https://3dprint.com September 25, 2018 at 01:54PM
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