High toughness biodegradable radiopaque composites based on polylactide and barium sulphate

In the present work, incorporation of submicron barium sulphate (BaSO4) particles to a poly(l-lactide) (PLLA) matrix is explored as a strategy to improve the radiopacity and simultaneously enhance the toughness of the resulting composites. Accordingly, BaSO4 loaded PLLA composites were prepared via melt-blending and were fully characterized in terms of thermal transitions, mechanical properties, morphology and radiopacity. X-ray analysis confirmed the enhanced radiopacity of the BaSO4 filled composites with respect to their unfilled counterparts. Additionally, toughness of PLLA matrix was impressively improved when BaSO4 particles were added. As an illustration, incorporation of 10 wt.% of BaSO4 particles resulted in a 1647 and 3338% increase in toughness and elongation of PLLA matrix, respectively.Authors are thankful for funds of Basque Government (GV/E) Department of Education, Universities and Research and Department of Industry of the Basque Government (projects S-PC13UN025 and GIC 12/161-IT632-13). Funding from MINECO (project MAT2013-45559-P) is also acknowledged. I. Martínez de Arenaza is thankful for the postdoctoral fellowship to POLYMAT Fundazioa-Basque Center for Macromolecular Design and Engineering (code 420)

Understanding the toughness mechanism prompted by submicron rigid particles in polylactide/barium sulfate composites

Polylactides are extensively employed as bone-fixation devices, due to their degradability and high tensile modulus. As demonstrated in a previous study, the incorporation of barium sulfate submicron particles impressively enhanced toughness with almost no adverse effect on yield strength. It is therefore a promising strategy in the design of radiopaque materials intended for use in safety-critical systems. In the present study, the mechanism that causes high-level plastic deformation in this system is identified through tensile and fracture tests, together with a thorough analysis of the microstructure via transmission and SEM (Scanning Electron Microscopy). The presence of submicron particles was observed to reduce crystallinity and to increase energy dissipation during the plastic deformation of the polymer matrix, inducing crack widening and fibrillated crazing that propagated around the crack opening. The result is a five-fold increase in the energy that is required to fracture the composite with respect to its neat polymer counterpart.The authors are grateful for funds from POLYMAT Fundazioa, Basque Government (GV/EJ) (IT-927-16, S-PC13UN025) and MINECO (MAT-2016-78527-P).N.S.and I.M. are respectively thankful for the predoctoral and postdoctoral fellowships to POLYMAT and A.L. wishes to acknowledge support from the Basque Government for his postdoctoral fellowship

Crystallization-Induced Gelling as a Method to 4D Print Low-Water-Content Non-isocyanate Polyurethane Hydrogels

[EN]The use of three-dimensional (3D) printable hydrogels for biomedical applications has attracted considerable attention as a consequence of the ability to precisely define the morphology of the printed object, allowing patients' needs to be targeted. However, the majority of hydrogels do not possess suitable mechanical properties to fulfill an adequate rheological profile for printability, and hence, 3D printing of cross-linked networks is challenging and normally requires postprinting modifications to obtain the desired scaffolds. In this work, we took advantage of the crystallization process of poly(ethylene glycol) to print non-isocyanate poly(hydroxyurethane) hydrogels with tunable mechanical properties. As a consequence of the crystallization process, the hydrogel modulus can be tuned up to 3 orders of magnitude upon heating up to 40 degrees C, offering an interesting strategy to directly 3D-print hydrogels without the need of postprinting cross-linking. Moreover, the absence of any toxicity makes these materials ideal candidates for biomedical applications.The authors acknowledge financial support from the European Commission through SUSPOL-EJD 642671 project. M.C.A. thanks the University of Birmingham for funding

Benefits of Polydopamine as Particle/Matrix Interface in Polylactide/PD-BaSO4 Scaffolds

This work reports the versatility of polydopamine (PD) when applied as a particle coating in a composite of polylactide (PLA). Polydopamine was observed to increase the particle–matrix interface strength and facilitate the adsorption of drugs to the material surface. Here, barium sulfate radiopaque particles were functionalized with polydopamine and integrated into a polylactide matrix, leading to the formulation of a biodegradable and X-ray opaque material with enhanced mechanical properties. Polydopamine functionalized barium sulfate particles also facilitated the adsorption and release of the antibiotic levofloxacin. Analysis of the antibacterial capacity of these composites and the metabolic activity and proliferation of human dermal fibroblasts in vitro demonstrated that these materials are non-cytotoxic and can be 3D printed to formulate complex biocompatible materials for bone fixation devices.The authors express thanks for technical and human support provided by SGIker of UPV/EHU and European funding: European Regional Development Fund (ERDF) and European Social Fund (ESF)

Radiopaque Material for 3D Printing Scaffolds

The so called “Additive manufacturing” is a new manufacturing process which consists in translating virtual solid model data into physical models in a quick and easy process. The most known example is 3D printing. In the present work, this novel technology will be used to print scaffolds with biomaterials. Due to the problems that arise when controlling the clinical course of an implant, graft or polymer inside the human body, an innovative idea has emerged: it consists in incorporating particles of barium sulfate in order to increase the radiopacity of the polylactide (PLLA) and thus making these materials visible to X-rays. Accordingly, BaSO4 loaded PLLA composites were prepared via melt-blending and then injected for further characterization by thermal transitions, mechanical properties, morphology and radiopacity. X-ray analyses confirmed the enhanced radiopacity of the BaSO4 filled composites in comparison to their unfilled counterparts. It is demonstrated that the loads not only contribute to the material's radiopacity, but also dramatically improve its ductility. As an illustration, the incorporation of 10 wt.% of BaSO4 particles resulted in an outstanding 1647% and 3338% increase in toughness and elongation of PLLA matrix, respectively. In view of the good properties of these materials, they will be used for 3D printing. Through this technique it can be molded with any shape in a matter of minutes, making the use of this technology appealing for further innovations.Authors are thankful for funds of Basque Government (GV/EJ) Department of Education (IT-927-16) and from MINECO (MAT 2016-78527-P). N. Sadaba is thankful for the predoctoral fellowship to POLYMAT Fundazioa- Basque Center for Macromolecular Design and Engineering