808 nm NIR-triggered Camellia sapogein/curcumin-based antibacterial upconversion nanoparticles for synergistic photodynamic-chemical combined therapy

Antibacterial upconversion nanoparticles (UCNP)-based photodynamic-chemical combined therapy (UCNP-aPCCT) provides an ideal method to solve the problem of antibiotic-resistant bacteria in deep-tissue infections. Saponin is a kind of natural product exhibiting promising antibacterial activity. Curcumin is also a natural product that could be used as photosensitizer for antibacterial photodynamic therapy (aPDT). Herein, we have designed the dual-layer silica-coated upconversion nanoparticles combined with UCNP-photodynamic therapy (PDT) and chemotherapy using curcumin as a photosensitizer and the Camellia sapogenin derivative (CSD) as an antibacterial agent. It turned out that the prepared UCNP@mSiO2(Cur)@DmSiO2(CSD)@PVP nanoparticles displayed high antibacterial activity against Escherichia coli and Staphylococcus aureus under near-infrared (NIR) irradiation at 808 nm. Its antibacterial activity is stronger than that of the simple sum of saponin and curcumin aPDT, indicating the existence of a synergetic photodynamic-chemical effect. The current nanoparticle drug system may have potential applications for deep-tissue anti-infection treatment.