Mg-MOF-74@MnO2 koosh ball-like nanoparticles modified PLLA bone scaffold achieving mild-temperature photothermal antibacterial function.

Regarding the issue that poly-L-lactic acid (PLLA) bone scaffold lacks antibacterial function, koosh ball-like nanoparticles, Mg-MOF-74@MnO2, have been synthesized by evenly in situ growing MnO2 nanowires on Mg-MOF-74 nanoparticles, and they were incorporated into PLLA matrix to fabricate bone scaffold with mild-temperature photothermal antibacterial activity. The results demonstrated that the Mg-MOF-74@MnO2 koosh ball-like nanoparticles generated hydroxyl radical (∙OH) synergistically due to redox reaction of the Mg-MOF-74 particles and enzyme-like activities of the MnO2 nanowires. The MnO2 nanowires can convert near-infrared (NIR) light energy into heat, and the in-situ growth enabled the MnO2 nanowires to disperse uniformly so as to better exert its photothermal property. After incorporation, the PLLA/Mg-MOF-74@MnO2 bone scaffold was fabricated via selective laser sintering (SLS). The bone scaffold reached a stable photothermal temperature of 40-45 °C under NIR irradiation, and had good ∙OH generating capacity. The generated∙OH inhibited bacterial adenosine triphosphate (ATP) level and weakened their thermotolerance without impairing osteoblasts, thereby enabling efficient bacterial killing under mild photothermal heating without damaging osteoblasts, endowing the scaffold with mild-temperature photothermal antibacterial function. As a result, the scaffold's in vitro antibacterial rates were 99.50% against Staphylococcus aureus and 99.88% against Escherichia coli. Implanted subcutaneously in the rats, the scaffold's in vivo antibacterial rate was 91.39%. Moreover, the PLLA/Mg-MOF-74@MnO2 bone scaffold also presented satisfying mechanical properties and biocompatibility.