Quantitative multiplexed SWIR imaging to study nanomedicine surface coatings in vivo

Shortwave infrared (SWIR) imaging capitalizes on the low tissue scattering and low autofluorescence in the near infrared- II (NIR-II) window (1000 nm – 1700 nm) for in vivo imaging with deep imaging penetration and high signal-to-noise contrast. Combining NIR-I excitation and emission in SWIR window, quantitative multiplexed imaging could be applied to study biological structures or physiological phenomenon in a single specimen. This study introduces a set of three high quantum yield lead sulfide/cadmium sulfide (PbS/CdS) core/shell quantum dots (QDs) with distinct SWIR emissions (1100 – 1550 nm). Applying these QDs, we demonstrated detailed lymphatic pathway, lymphatic drainage, and spatially overlapping vascular structures, marking a significant advancement beyond the conventional two-color schemes in SWIR imaging. We further evaluated the effect of surface coatings of the QDs on the pharmacokinetics and biodistribution of QDs in mice. The capacity to differentiate several fluorescent contrast agents through SWIR detection unlocks numerous opportunities for studies of disease progression, drug pharmacokinetics and biodistribution, and cell trafficking dynamics in living organisms.