Dual contrasting ability of NaGd0.7Eu0.3F4 nanocrystals tuned by their hydrophilic coating mode

This work introduces non-covalent hydrophilic coating of NaGd_0.7Eu_0.3F₄ nanocrystals by polylysine (PL) and polyethyleneimine (PEI) for MRI and fluorescent imaging purposes. PL- and PEI-stabilized nanocrystals exhibit high colloidal stability, cell internalization, fluorescent contrasting of nuclei and cytoplasm, low cytotoxicity, and relaxivity (r₁= 0.17 dm³ mmol^–1 s^–1 and r₁ = 0.23 dm³ mmol^–1 s^–1).