Tailoring the pore structure of iron oxide core@stellate mesoporous silica shell nanocomposites: effects on MRI and magnetic hyperthermia properties and applicability to anti-cancer therapies.

Core-shell nanocomposites made of iron oxide core (IO NPs) coated with mesoporous silica (MS) shells are promising theranostic agents. While the core is being used as an efficient heating nanoagent under alternating magnetic field (AMF) and near infra-red (NIR) light and as a suitable contrast agent for magnetic resonance imaging (MRI), the MS shell is particularly relevant to ensure colloidal stability in a biological buffer and to transport a variety of therapeutics. However, a major challenge with such inorganic nanostructures is the design of adjustable silica structures, especially with tunable large pores which would be useful, for instance, for the delivery of large therapeutic biomolecule loading and further sustained release. Furthermore, the effect of tailoring a porous silica structure on the magneto- or photothermal dissipation still remains poorly investigated. In this work, we undertake an in-depth investigation of the growth of stellate mesoporous silica (STMS) shells around IO NPs cores and of their micro/mesoporous features respectively through time-lapse and in situ liquid phase transmission electron microscopy (LPTEM) and detailed nitrogen isotherm adsorption studies. We found here that the STMS shell features (thickness, pore size, surface area) can be finely tuned by simply controlling the sol-gel reaction time, affording a novel range of IO@STMS core@shell NPs. Finally, regarding the responses under alternating magnetic fields and NIR light which are evaluated as a function of the silica structure, IO@STMS NPs having a tunable silica shell structure are shown to be efficient as T2-weighted MRI agents and as heating agents for magneto- and photoinduced hyperthermia. Furthermore, such IO@STMS are found to display anti-cancer effects in pancreatic cancer cells under magnetic fields (both alternating and rotating).

Orienting the Pore Morphology of Core-Shell Magnetic Mesoporous Silica with the Sol-Gel Temperature. Influence on MRI and Magnetic Hyperthermia Properties.

The controlled design of robust, well reproducible, and functional nanomaterials made according to simple processes is of key importance to envision future applications. In the field of porous materials, tuning nanoparticle features such as specific area, pore size and morphology by adjusting simple parameters such as pH, temperature or solvent is highly needed. In this work, we address the tunable control of the pore morphology of mesoporous silica (MS) nanoparticles (NPs) with the sol-gel reaction temperature (Tsg). We show that the pore morphology of MS NPs alone or of MS shell covering iron oxide nanoparticles (IO NPs) can be easily tailored with Tsg orienting either towards stellar (ST) morphology (large radial pore of around 10 nm) below 80 °C or towards a worm-like (WL) morphology (small randomly oriented pores channel network, of 3-4 nm pore size) above 80 °C. The relaxometric and magnetothermal features of IO@STMS or IO@WLMS core shell NPs having respectively stellar or worm-like morphologies are compared and discussed to understand the role of the pore structure for MRI and magnetic hyperthermia applications.

Wrapped stellate silica nanocomposites as biocompatible luminescent nanoplatforms assessed in vivo.

The engineering of luminescent nanoplatforms for biomedical applications displaying ability for scaling-up, good colloidal stability in aqueous solutions, biocompatibility, and providing an easy detection in vivo by fluorescence methods while offering high potential of functionalities, is currently a challenge. The original strategy proposed here involves the use of large pore (ca. 15 nm) mesoporous silica (MS) nanoparticles (NPs) having a stellate morphology (denoted STMS) on which fluorescent InP/ZnS quantum dots (QDs) are covalently grafted with a high yield (≥90%). These nanoplatforms are after that further coated to avoid a potential QDs release. To protect the QDs from potential release or dissolution, two wrapping methods are developed: (i) a further coating with a silica shell having small pores (≤2 nm) or (ii) a tight polysaccharide shell deposited on the surface of these STMS@QDs particles via an original isobutyramide (IBAM)-mediated method. Both wrapping approaches yield to novel luminescent nanoplatforms displaying a highly controlled structure, a high size monodispersity (ca. 200 and 100 nm respectively) and colloidal stability in aqueous solutions. Among both methods, the IBAM-polysaccharide coating approach is shown the most suitable to ensure QDs protection and to avoid metal cation release over three months. Furthermore, these original STMS@QDs@polysaccharide luminescent nanoplatforms are shown biocompatible in vitro with murine cancer cells and in vivo after injections within zebrafish (ZF) translucent embryos where no sign of toxicity is observed during their development over several days. As assessed by in vivo confocal microscopy imaging, these nanoplatforms are shown to rapidly extravasate from blood circulation to settle in neighboring tissues, ensuring a remanent fluorescent labelling of ZF tissues in vivo. Such fluorescent and hybrid STMS composites are envisioned as novel luminescent nanoplatforms for in vivo fluorescence tracking applications and offer a versatile degree of additional functionalities (drug delivery, incorporation of magnetic/plasmonic core).

Mesoporous silica templated-albumin nanoparticles with high doxorubicin payload for drug delivery assessed with a 3-D tumor cell model.

Human serum albumin (HSA) nanoparticles emerge as promising carriers for drug delivery. Among challenges, one important issue is the design of HSA nanoparticles with a low mean size of ca. 50 nm and having a high drug payload. The original strategy developed here is to use sacrificial mesoporous nanosilica templates having a diameter close to 30 nm to drive the protein nanocapsule formation. This new approach ensures first an efficient high drug loading (ca. 30%) of Doxorubicin (DOX) in the porous silica by functionalizing silica with an aminosiloxane layer and then allows the one-step adsorption and the physical cross-linking of HSA by modifying the silica surface with isobutyramide (IBAM) groups. After silica template removal, homogenous DOX-loaded HSA nanocapsules (30-60 nm size) with high drug loading capacity (ca. 88%) are thus formed. Such nanocapsules are shown efficient in multicellular tumor spheroid models (MCTS) of human hepatocarcinoma cells by their significant growth inhibition with respect to controls. Such a new synthesis approach paves the way toward new protein based nanocarriers for drug delivery.

Micro-chlorido, micro-hydroxo-bridged dicarbonyl ruthenacycles: synthesis, structure and catalytic properties in hydrogen atom transfer.

Micro-chlorido, micro-hydroxo-bridged ruthenacycles containing the Ru(CO)2 motif were synthesized by reaction of micro-dichlorido-bridged congener complexes with water in the presence of disodium carbonate. The substitution of one chlorido ligand for one hydroxo occurs with high stereoselectivity affording essentially hydroxo-bridged ruthenacycles, whereby the OH ligand occupies axial positions with respect to the mean plane defined by the chelating ligand. According to computational DFT investigations this stereoselectivity stems from a marked transphobia of the hydroxo ligand towards the carbanion of the ruthenacycle. The catalytic properties of the title compounds in hydrogen atom transfer process and particularly in the partial hydrogenation of alkynes have been investigated.