Transport of NaYF4: Er3+, Yb3+ upconverting nanoparticles into HeLa cells

Abstract

An effective, simple and practically useful method to incorporate fluorescent nanoparticles inside live biological cells was developed. The internalization time and concentration dependence of a frequently used liposomal transfection factor Lipofectamine 2000 was studied. An users friendly, one-step technique to obtain water and organic solvents soluble Er3+and Yb3+ doped NaYF4 nanoparticles coated with polyvinylpyrrolidone (PVP) was obtained. The nanoparticles structural analysis confirmed the formation of nanocrystals of desired sizes and spectral properties. Internalization of NaYF4 nanoparticles in HeLa cervical cancer cells were determined at different nanoparticles concentrations and for incubation periods from 3 to 24 hours. The images revealed a redistribution of nanoparticles inside the cell, which increases with incubation time, concentration levels and depends on the presence of the transfection factor. The study identifies, for the first time, factors responsible for an effective endocytosis of the up-converting nanoparticles to HeLa cells. Thus the method could be applied to investigate a wide range of future “smart” theranostic agents. The nanoparticles incorporated into the liposomes appear to be very promising fluorescent probes for imaging real-time cellular dynamics.