Surface modification strategy based on the conjugation of NaYF4:5%Eu luminescent nanoprobe with organic aromatic compounds for application in bioimaging assays

Colon cancer is one of the world’s most deadly diseases. Because of its internal location, it is necessary to obtain faster and more efficient diagnostic tools for this organ site. In this context, we studied the development of new luminescent nanoprobes (LNPs) as an alternative diagnostic apparatus for detecting this disease. The nanoparticles examined herein are lanthanide-doped sodium yttrium fluoride (NaYF4:Ln) and have shown to be promising as investigative devices. However, significant problems with the use of LNPs are the lack of biocompatibility and the targeting of the system to tumor regions. One of the strategies to bypass these problems is to increase of the particle lipophilicity modifying their surfaces with organic compounds that present high similarity to the biological system. In this work, we synthesized six new materials for use in bioimaging techniques obtained from the combination of nanoparticles of NaYF4:5%Eu with organic aromatic compounds covalently bonded. The materials were characterized structurally and morphologically using XRD and TEM, techniques, which showed the identification of the crystallographic phase β-NaYF4:5%Eu and its nanometric size (particles smaller than 50 nm). The conjugation process was confirmed by FT-IR spectra analysis and from the TGA profile. Excitation and emission spectra allowed the evaluation of the optical properties of the synthesized compounds. The interaction and cellular uptake was confirmed when HT-29 colon cancer cells were exposed to LNPs, indicating that the developed system has promising applications in bioimaging procedures.