Surface charge effect on the cellular interaction and cytotoxicity of NaYF4:Yb3+, Er3+@SiO2 nanoparticles

Taking advantage of the unique optical properties of upconversion nanoparticles (NP) and the feasibly modified nature of SiO2, NaYF4:Yb3+, Er3+@SiO2 core@shell (UCNP@SiO2) NPs with excellent morphology have been synthesized to investigate the surface charge effect on the interactions of NPs with cells. The cellular uptake behaviors, cytotoxicities and intracellular metal ion release of the as-prepared NPs have been investigated in two cell lines (HeLa and HepG-2) by fluorescence microscopy, MTT assay and inductively coupled plasma mass spectrometry (ICP-MS), respectively. It is found that the UCNP@SiO2 NPs with positive surface charge have much higher cell internalization ability and cytotoxicity than those with negative surface charge. The experimental results also demonstrate that the cytotoxicity of UCNP@SiO2 NP is closely related to the increase of intracellular reactive oxygen species (ROS) and metal ion release of internalized NPs.