Supercritically dried superparamagnetic mesoporous silica nanoparticles for cancer theranostics.

Mesoporous silica nanoparticles with a superparamagnetic iron oxide core were prepared in this work, in order to obtain multifunctional platforms with adequate features for cancer theranostics. Three different core-shell nanocomplexes were obtained: IO-OAm/mSiO, IO-APTES/mSiO and IO/SiO/mSiO. In the case of IO-OAm/mSiO and IO-APTES/mSiO, iron oxide (IO) was obtained by thermal decomposition, having in this case a coating of oleylamine (OAm) that was in the second formulation exchanged by (3-aminopropyl)triethoxysilane ligand (APTES). Regarding the IO/SiO/mSiO formulation, iron oxide was synthesized by microemulsion. The mesoporous silica shell (mSiO) on the IO nanoparticles was obtained by sol-gel and the final materials were dried by supercritical fluids drying. VSM confirmed the superparamagnetic behaviour of the nanoparticles, leading to M of 4.0, 1.8 and 10.2 emu·g, for IO-OAm/mSiO, IO-APTES/mSiO and IO/SiO/mSiO, respectively. NMR relaxometry has shown the potential of these nanoparticles to be used as T contrast agents, with r values as high as 63.93 s·mM Fe. The three types of nanoparticles exhibited loading contents of epirubicin of ~3% and drug release percentages of 19% for IO-OAm/mSiO, 24% for IO-APTES/mSiO and 31% for IO/SiO/mSiO. The cytotoxicity of drug-loaded and non-loaded most promising nanoparticles was assessed, showing high potential of these platforms for application as anticancer drug carriers.