Due to the continuous evolution of additive manufacturing (AM), the development of new materials as feedstock for a given technology has been gained interest in several areas, including tissue engineering. Polylactic acid (PLA) has been extensively explored as a Fused Filament Fabrication (FFF) feedstock material to produce structures for bone tissue engineering applications. Although PLA presents a good compromise between mechanical properties and biocompatibility, this thermoplastic polyester lacks bioactivity and its biodegradation rate is usually slow. In contrast, calcium phosphate-based (CaP) bioceramics are widely known due to their similarity with the inorganic part of bone and bioactive properties. Thus, the development of a composite by filling the PLA matrix with CaP-based powders could be a viable option to enhance the bioactivity of neat PLA, as well as to improve its mechanical performance. Magnetic biomaterials have captured interest in the scientific community since they have been demonstrating great ability to accelerate the tissues’ restoration process, encouraging the use of these biomaterials also for bone regeneration. Therefore, by resorting to iron ions (Fe²⁺ and Fe³⁺) as dopants, the development of magnetic calcium phosphates could be a solution to enhance magnetic susceptibility of calcium phosphate powders and to confer as well magnetic properties to PLA composites.
This study presents an innovative strategy to develop injection moulded PLA-based magnetic biocomposites, by using CaP-based intrinsic magnetic powders as fillers, circumventing the use of magnetic nanoparticles whose long-term side effects are still unclear. Magnetic biocomposites were obtained by incorporating 5 wt% of iron doped biphasic calcium phosphate (FeBCP) powders into the PLA matrix and compared with similar composites containing 2 and 5 wt% of non-doped BCP powder, as well as neat PLA. The powders were incorporated in PLA matrix by a melt mixing method, without requiring the use of organic solvents which may be harmful in biological environment. The chemical, thermal, mechanical, and magnetic properties, as well as biodegradation rate comparing two sterilization methods, were all assessed. The magnetic FeBCP composites demonstrated a typical ferromagnetic-like behaviour and enhanced tensile strength, when compared to PLA or even PLA in presence of non-magnetic CaP-based powders. The magnetic biocomposite developed presents high potential to be explored in several applications, including bone regeneration.

Acknowledgments: This work is funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT - Portuguese Foundation for Science and Technology under the projects MulBioImplant and 2BBone with references PTDC/EMEEME/ 32486/2017 and PTDC/CTM-CER/29940/2017, respectively. The project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MCTES (PIDDAC) is also acknowledged. P M C Torres and S M Olhero acknowledge FCT for CEECIND/01891/2017 and CEECIND/03393/2017 contracts, respectively. J H Belo thanks FCT for the projects PTDC/FISMAC/ 31302/2017, PTDC/EME-TED/3099/2020 and CERN/FISTEC/0003/2019 and for his contract DL57/2016 (SFRH-BPD- 87430/2012).