Journal article Open Access

Ultrafast photochemistry produces superbright short-wave infrared dots for low-dose in vivo imaging

Harrisson D. A. Santos; Irene Zabala Gutiérrez; Yingli Shen; José Lifante; Erving Ximendes; Marco Laurenti; Diego Méndez-González; Sonia Melle; Oscar G. Calderón; Enrique López Cabarcos; Nuria Fernández; Irene Chaves-Coira; Daniel Lucena-Agell; Luis Monge; Mark D. Mackenzie; José Marqués-Hueso; Callum M. S. Jones; Carlos Jacinto; Blanca del Rosal; Ajoy K. Kar; Jorge Rubio-Retama; Daniel Jaque

Optical probes operating in the second near-infrared window (NIR-II, 1,000-1,700 nm), where tissues are highly transparent, have expanded the applicability of fluorescence in the biomedical field. NIR-II fluorescence enables deep-tissue imaging with micrometric resolution in animal models, but is limited by the low brightness of NIR-II probes, which prevents imaging at low excitation intensities and fluorophore concentrations. Here, we present a new generation of probes (Ag2S superdots) derived from chemically synthesized Ag2S dots, on which a protective shell is grown by femtosecond laser irradiation. This shell reduces the structural defects, causing an 80-fold enhancement of the quantum yield. PEGylated Ag2S superdots enable deep-tissue in vivo imaging at low excitation intensities (<10 mW cm−2) and doses (<0.5 mg kg−1), emerging as unrivaled contrast agents for NIR-II preclinical bioimaging. These results establish an approach for developing superbright NIR-II contrast agents based on the synergy between chemical synthesis and ultrafast laser processing.

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