A hollow porous magnetic nanocarrier for efficient near-infrared light- and pH-controlled drug release

Abstract

A multi-functional core–shell nanocarrier was successfully prepared for near-infrared light- and pH-controlled drug release as well as magnetic resonance imaging (MRI) and fluorescence imaging. On the one hand, the hollow porous Fe₃O₄ (HPFe₃O₄, ∼20 nm) which could be etched under acidic conditions inside the cancer cells was prepared as the “core” to load anti-cancer drugs. On the other hand, the targeting NIR light-responsive copolymer (DDACMM-PEG-FA) was synthesized by polymerization of coumarin-containing monomer (DDACMM), poly(ethylene glycol) (PEG) methyl ether methacrylate and N-hydroxysuccinimide (NHS) and then modified by folic acid (FA). The core–shell nanocarriers (HPFe₃O₄@DDACMM-PEG-FA) were obtained by coating the amphiphilic copolymers onto the hollow porous “core”. Since the copolymer could be disrupted under the irradiation of NIR light laser (800 nm) via a two-photon absorption process, the pre-loaded drugs (∼65–80%) could be released from the nanocarriers. More importantly, the subacid environment in the tumour could further etch the boundary area of uncovered HPFe₃O₄, which further improved the efficiency of the drug release (about 20% increase in 24 h). The in vitro experiments indicated that the nanocarriers were biocompatible and could easily target the tumour cells that over-expressed folic acid receptor (FR(+)) and release the pre-loaded drugs successfully. In addition, because of the superparamagnetism of HPFe₃O₄ and the fluorescence of the polymer, the MRI and cell fluorescence imaging could be used to track the process of drug delivery.