Porous Iron Oxide Based Nanorods Developed as Delivery Nanocapsules

Abstract

A low-temperature solution approach (90–95 °C) using FeCl₃ and urea was carried out to synthesize β-FeOOH nanorods in aqueous solution. The as-synthesized β-FeOOH nanorods were further calcined at 300 °C to form porous nanorods with compositions including both β-FeOOH and α-Fe₂O₃. The derived porous nanorods were engineered to assemble with four layers of polyelectrolytes (polyacrylic acid (PAA)/polyethylenimine(PEI)/PAA/PEI) on their surfaces as polyelectrolyte multilayer nanocapsules. Fluorescein isothiocyanate (FITC) molecules were loaded into the polyelectrolyte multilayer nanocapsules in order to investigate drug release and intracellular delivery in Hela cells. The as-prepared nanocapsules showed ionic strength-dependent control of the permeability of the polyelectrolyte shells. The release behavior of the entrapped FITC from the FITC-loaded nanocapsules exhibited either controlled- or sustained-release trends, depending on the compactness of the polyelectrolyte shells on the nanorod surfaces. Cytotoxicity measurements demonstrate that the native nanorods and the polymer-coated nanorods have excellent biocompatibility in all dosages between 0.1 ng mL⁻¹ and 100 μgm L⁻¹. The time dependence of uptake of FITC-loaded nanocapsules by Hela cancer cells observed by laser confocal microscopy indicates that the nanocapsules can readily be taken up by cancer cells in 15 min, a relatively short period of time, while the slow release of the FITC from the initial perimembrane space into the cytoplasm was followed by release into the nucleus after 24 h.