Bidirectional Regulation of Singlet Oxygen Generation from Luminescent Gold Nanoparticles through Surface Manipulation.

Singlet oxygen (O-1(2)) generation has been observed from ultrasmall luminescent gold nanoparticles (AuNPs), but regulation of O-1(2) generation ability from the nanosized noble metals has remained challenging. Herein, the O-1(2) generation ability of ultrasmall AuNPs (d approximate to 1.8 nm) is reported to be highly correlated to the surface factors including the amount of Au(I) species and surface charge. By taking the advantages of facile in situ PEGylation, it is discovered that a high amount of Au(I) species and surface charge results in strong ability in generation of O-1(2), whereas a relative low amount of Au(I) species and surface charge leads to weak ability in O-1(2) production. A feasible general strategy is then developed to controllably regulate the O-1(2) generation efficiency of the AuNPs through facile ligand exchange with positively-charged or negatively-charged thiolated ligands. The AuNPs as nanophotosensitizer for O-1(2) generation in the cellular level is also demonstrated to be highly controllable through surface ligand exchange with synergistical effects of O-1(2) generation ability and subcellular distribution to lysosome or mitochondria. The strategy in the bidirectional regulation of O-1(2) generation from ultrasmall AuNPs provides guidance for future design of nanosized metal nanomedicine toward specific disease diagnosis and treatment.