Bacteria-Triggered pH-Responsive Osteopotentiating Coating on 3D-Printed Polyetheretherketone Scaffolds for Infective Bone Defect Repair

Biomaterial-enabled regeneration of the infected or contaminated bone defects remains one of the critical challenges in the development of new clinical treatments. Three-dimensional (3D) porous scaffolds, which can synchronously emulate the hierarchy of bone structures and additionally provide bactericidal and osteogenic features, offer a potential solution to tackle this issue. In this work, we construct hierarchical porous polyetheretherketone (PEEK) scaffolds via 3D printing, equipped with a pH-triggered osteopotentiating coating. In the design of the coating, silver nanoparticles (AgNPs) are trapped onto the first polydopamine (pDA) layer, and apatite is further anchored onto the second pDA layer. The unique pDA-Ag-pDA sandwich structure imparts bacteria-triggered pH-responsive ion-releasing behavior to the inert PEEK scaffolds, i.e., the liberation of Ag+ ions from the coating is augmented with decreasing pH value, which is associated with the metabolism of bacteria. These bioscaffolds exhibit excellent capability for eradicating bacteria, as well as harness acceptable cytocompatibility and protuberant osteogenetic potential of osteoblastic MC3T3-E1 cells. Importantly, in vivo evaluation indicates that the Ag/apatite codecorated multifunctional bioscaffolds present appealing in vivo antibacterial efficacy and excellent bone ingrowth and osseointegration in an infected critical-sized bone defect. Accordingly, such smart pH-triggered osteopromotive PEEK implants demonstrate strong potential in the treatment of the complicated infective bone disorders.