Lanthanide-doped rare earth nanoparticles for near-infrared-II imaging and cancer therapy

The optical nanoprobes with emissions in the second near-infrared window (NIR-II, 1000–1700 nm) show low tissue autofluorescence and photon scattering; therefore, they provide high spatial resolution and acceptable tissue penetration depth. These advantages make them appropriate for in vivo applications, including bioimaging, NIR-II triggered disease therapy, and even on-site efficacy monitoring. Among the various developed NIR-II fluorescence probes, lanthanide-doped nanoparticles (LDNPs) exhibit high photo stability and narrow emission bandwidths with long photoluminescence lifetimes and low cytotoxicity; therefore, they have been widely studied in the biomedical field. This review summarizes the typical compositions and optical properties of recently developed NIR-II emitting LDNPs. Their applications in in vivo NIR-II bioimaging and cancer therapy are reviewed. The perspectives and challenges of NIR-II LDNPs are also discussed.