3D-Printed PLLA/Pt–GO Scaffolds with Synergistic Photodynamic and Photothermal Antibacterial Activity

Platinum nanoparticles (Pt NPs) as nanozymes presented great potential in photodynamic antibacterial applications. However, the tendency for aggregation and the presence of bacterial biofilms limit their photodynamic antibacterial efficacy. Herein, Pt NPs were grown in situ on graphene oxide (GO) nanosheets to prepare Pt–GO nanohybrids, which were subsequently blended with poly(l-lactic acid) (PLLA) powder and fabricated into PLLA/Pt–GO scaffolds via laser 3D printing technology. On one hand, GO possessed a high specific surface area, providing a large space for the uniform deposition of Pt NPs. On the other hand, GO had excellent photothermal properties, which not only enhanced the permeability of the bacterial biofilm but also further improved the photodynamic catalytic effect of Pt NPs. Results demonstrated that the scaffold exhibited favorable photothermal stability and transformation efficiency under near-infrared (NIR) light irradiation. Methylene blue degradation and o-phenylenediamine oxidation assays demonstrated that the scaffold exhibited peroxidase-like activity. Antibacterial experiments demonstrated that under NIR light irradiation, the PLLA/Pt–GO group exhibited decreased bacterial colonies, damaged bacterial morphology, enhanced biofilm permeability, elevated intracellular reactive oxygen species (ROS) levels, and increased bacterial protein leakage compared to the ice bath-cooled PLLA/Pt–GO group. These findings indicated that thermal energy enhanced biofilm permeability, facilitated the entry of ROS into bacterial cells, induced protein leakage, and ultimately resulted in bacterial death. In summary, the scaffold demonstrated antibacterial efficacy rates of 94.15% and 91.42% against E. coli and S. aureus, respectively. Therefore, this study holds promise for providing therapeutic strategies for implant-related infections.