TY - JOUR A1 - Baziulyte-Paulaviciene, Dovile A1 - Karabanovas, Vitalijus A1 - Stasys, Marius A1 - Jarockyte, Greta A1 - Poderys, Vilius A1 - Sakirzanovas, Simas A1 - Rotomskis, Ricardas T1 - Synthesis and functionalization of NaGdF4:Yb,Er@NaGdF4 core–shell nanoparticles for possible application as multimodal contrast agents JF - Beilstein Journal of Nanotechnology PY - 2017/// VL - 8 SP - 1815 EP - 1824 SN - 2190-4286 DO - 10.3762/bjnano.8.183 PB - Beilstein-Institut JA - Beilstein J. Nanotechnol. UR - https://doi.org/10.3762/bjnano.8.183 KW - cancer theranostics KW - core–shell structure KW - luminescence KW - multimodal KW - nanoparticles KW - upconverting nanoparticles KW - upconversion N2 - Upconverting nanoparticles (UCNPs) are promising, new imaging probes capable of serving as multimodal contrast agents. In this study, monodisperse and ultrasmall core and core–shell UCNPs were synthesized via a thermal decomposition method. Furthermore, it was shown that the epitaxial growth of a NaGdF4 optical inert layer covering the NaGdF4:Yb,Er core effectively minimizes surface quenching due to the spatial isolation of the core from the surroundings. The mean diameter of the synthesized core and core–shell nanoparticles was ≈8 and ≈16 nm, respectively. Hydrophobic UCNPs were converted into hydrophilic ones using a nonionic surfactant Tween 80. The successful coating of the UCNPs by Tween 80 has been confirmed by Fourier transform infrared (FTIR) spectroscopy. Scanning electron microscopy (SEM), powder X-ray diffraction (XRD), photoluminescence (PL) spectra and magnetic resonance (MR) T1 relaxation measurements were used to characterize the size, crystal structure, optical and magnetic properties of the core and core–shell nanoparticles. Moreover, Tween 80-coated core–shell nanoparticles presented enhanced optical and MR signal intensity, good colloidal stability, low cytotoxicity and nonspecific internalization into two different breast cancer cell lines, which indicates that these nanoparticles could be applied as an efficient, dual-modal contrast probe for in vivo bioimaging. ER -