Lanthanide-Doped Materials as Probes for Hyperspectral Imaging—A Powerful Combination to Assess Nano-Bio Interactions

Hyperspectral imaging (HSI) is an analytical technique, that consists in mapping a region of interest while simultaneously collecting spectral information from each pixel of the image. This process generates a set of data called hyperspectral cube, that allows for a detailed study of structure-property relationships of the mapped region. When used in association with luminescent probes, HSI can be a powerful tool towards multiplexing detection, including biological samples. In this presentation, various surface-modified luminescent lanthanide-based upconverting nanoparticles (UCNPs) will be presented and the suitability of HSI to study their nano-bio interaction with cells and small animal models such as zebra fish embryos will be discussed. UCNPs of various chemical compositions were synthesized by an easy microwave-assisted thermal decomposition approach, resulting in multiple emission colors under a single excitation wavelength, i.e. near-infrared (NIR) light. Post-synthesis surface modification was achieved making use of newly developed methodologies with different biopolymers as well as traditional ligand-removal strategies. By using the HSI technique, we assessed how the surface chemistry of UCNPs resulted in different uptake behavior depending on the type of biological model used: macrophages, neuron cells or zebra fish embryos. The possibility to use NIR excitation to trigger a characteristic spectral signature of the UCNPs allows for outstanding bioimaging capabilities: no photodamage to the cells and embryos in addition to unmistakable identification of the probe signal. Moreover, tuning of the emission color of the surface-modified probes allows for their easy identification by HSI when mixed in buffer, showcasing their multiplexing capabilities. Ultimately, our findings represent an important step towards better understanding of nano-bio interactions of UCNPs. These insights can help the further development of UCNPs as powerful luminescent bioimaging probes.