Tat peptide mediated cellular uptake of SiO2 submicron particles

Internalization of nano- and microparticles into live cells correlates closely with their potential applications, functions, cytotoxicity and intracellular drug delivery. Particularly, delivery of a large variety of cargoes such as proteins, peptides, nucleic acids and small particles into cells could be enhanced by some ligands such as Tat peptide. In this work, the ability of Tat mediated cellular uptake was assessed. The Tat peptide was covalently immobilized to fluorescein tagged SiO2 particles (FITC–SiO2–NH2 particles) with a diameter of 200 nm. BCA protein assay determined that the grafting amount of the Tat peptide could be controlled within a range of 0–3.5 μg/mg SiO2 particles by the Tat feeding amount. Surface immobilization of the Tat peptide did not bring apparent changes on the surface morphology and charge property of the SiO2–NH2 particles. By contrast, the surface charge of both the FITC–SiO2–NH2 particles and the FITC–SiO2–Tat particles was reversed from slight positive in Dulbecco's Modified Eagles Medium (DMEM) to slight negative in DMEM/fetal bovine serum, conveying adsorption of plasma proteins on the particles. Flow cytometry measurement showed that the FITC–SiO2–Tat particles were internalized by HepG2 cells with a significant faster rate and a higher number of particles than that of the FITC–SiO2–NH2 particles. Moreover, internalization of the Tat peptide decorated particles was less influenced by the low temperature at 4 °C. The Tat decoration affected the subcellular distribution of the particles as well, resulting in localization of the particles in the cell nucleus. No obvious cytotoxicity was detected for both the FITC–SiO2–NH2 particles and the FITC–SiO2–Tat particles.