The global rise of antibiotic resistance of pathogenic bacteria has become an increasing medical and public concern, which is further urging the development of antimicrobial channels for treating infectious diseases. The combination of photodynamic therapy (PDT) with photothermal therapy (PTT) has been considered as a promising alternative way for the replacement of traditional antibiotic therapy. In this research, the newly fabricated Chlorin-e6 (Ce6) conjugated mesoporous silica-coated AuNRs, designated AuNR@SiO2-NH2-Ce6, exhibited synergistic photothermal effects and single oxygen localized generation property, and showed stronger photoinactivation for bacteria compared with Ce6. AuNR@SiO2-NH2-Ce6 can anchor to the cell membrane and accumulate in the interior of cells. Furthermore, the unique porous structure of AuNR@SiO2NH2 enabled Ce6 encapsulation in the mesopores and was subsequently released and activated by photothermic effect, allowing the generated single oxygen to penetrate into the cytoplasmic membrane or directly enter the interior of bacteria cells, thus overcoming the inherent defects of single oxygen. AuNR@SiO2-NH2-Ce6 not only damaged the integrity of the cell membrane of bacteria but also facilitated the cellular permeation and accumulation of external nanoagents in the bacteria upon light irradiation. In addition, AuNR@SiO2-NH2-Ce6 exhibited negligible cytotoxicity toward mammalian cells and hemolytic activity. Therefore, AuNR@SiO2-NH2-Ce6 may be highly promising candidates as topical antibacterial agents, and this study has wide implications on the design of next-generation antimicrobial agents.
Keywords: antibacterial; chlorin-e6; gold nanorod; photodynamic therapy; photothermal therapy.