Polylactic acid/rifampicin/hydroxyapatite/GnPs 3D‐printable composites for targeted antibiotic delivery in bone infections

Abstract Long‐term antibiotic‐loaded products are the cornerstone in developing targeted bone regeneration therapies. Here, the fabrication of new antibacterial composite products, by a two‐step homogenization process, is governed by the isolation of an antibiotic with thermal stability at the processing temperature (200°C). Based on preliminary thermogravimetric assessment, only rifampicin (RIF) responds positively. The composites’ synthesis involves, for the first time, the concomitant modulation of RIF (1–5 wt.%), bovine bone‐derived hydroxyapatite (HA) (0–30 wt.%), and graphene nanoplatelets (0–3 wt.%) into the poly(lactic acid) matrix. The conjoined incorporation of all materials evolved into superimposed strong molecular cross‐links, without any structural alteration during preparation. The microporous morphology of the HA particles facilitates the adhesion to the polymeric matrix and the entrapment/attachment of the RIF particles, contributing to a prolonged drug release and effect during the patient's recovery. The ascending trend of RIF release over 24 h corroborates the strong antibacterial activity of the products against Staphylococcus aureus (the principal bacteria responsible for the occurrence of osteomyelitis) and a medium‐low response against Escherichia coli , providing evidence that the antimicrobial properties were preserved during composite manufacturing at a maximum temperature of 200°C. The degradation process is indicative of the fragmentation of the ceramic particles, leading to the formation of new nucleation sites required for the growth of new bone in the long term. Overall, the results pinpointed the desired features for novel antibacterial composite materials compatible for future filament extrusion and 3D printing of implantable products for bone applications.