Core-shell iron oxide@stellate mesoporous silica for combined nearinfrared photothermia and drug delivery : influence of pH and surface chemistry

The chemical design of smart nanocarriers, providing in one nanoformulation combined anticancer therapies, still remains a challenge in the field of nanomedicine. Among nanomaterials, iron oxide-based coreshell nanostructures have been already studied for their intrinsic magnetic hyperthermia features that may be coupled with drug delivery. However, despite the great interest today for photo-induced hyperthermia, very few studies investigated the potential of such nanocarriers to combine photothermia and drug delivery. In this work, our aim was to design functional iron oxide@stellate mesoporous silica nanoparticles (denoted IO@STMS NPs) loaded with a drug and able to combine in a same formulation near infrared (NIR) light induced photothermia with antitumor drug release. Herein, the NIR photothermal properties (SAR, specific absorption rates) of such nanomaterials were quantified for the first time as a function of the laser power and the NP amount. Aside the response to NIR light, the conditions to obtain very high drug loading (drug payloads up to 91 wt%) of the model antitumor drug doxorubicin (DOX) were optimized by varying different parameters, such as the NP surface chemistry (BARE (Si-OH), aminopropylsiloxane (APTES) and isobutyramide (IBAM)) and the pH of the drug impregnation aqueous solution. The drug release study of these core-shell systems in the presence or absence of NIR light demonstrated that the DOX release efficiency is mainly influenced by two parameters: surface chemistry (BARE ≥ IBAM ≥ APTES) and pH (pH 5.5 ≥ pH 6.5 ≥ pH 7.5). Furthermore, the temperature profiles under NIR light are found similar and independent from the pH range, the surface chemistry and the cycle number. Hence, the combination of local photothermia with lysosomal-like pH induced drug delivery (up to 40% release of the loaded drug) with these nanostructures could open the way towards new drug delivery nanoplatforms for nanomedecine applications.