Magnetic nanocarriers for the specific delivery of siRNA: Contribution of breast cancer cells active targeting for down-regulation efficiency.

The association between superparamagnetic iron oxide nanoparticles (SPION), carrying small interfering RNA (siRNA) as therapeutic agents and humanized anti- human epidermal growth factor receptor-2 (HER2) single-chain antibody fragments (scFv) for the active delivery into HER2-overexpressing cells appears as an interesting approach for patients with HER2-overexpressing advanced breast cancer. The obtained Targeted Stealth Magnetic siRNA Nanovectors (TS-MSN) are formulated by combining: (i) the synthesis protocol of Targeted Stealth Fluorescent Particles (T-SFP) which form the core of TS-MSN and (ii) the formulation protocol allowing the loading of T-SFP with polyplexes (siRNA and cationic polymers). TS-MSN have suitable physico-chemical characteristics for intravenous administration and protect siRNA against enzymatic degradation up to 24 h. The presence of HER2-targeting scFv on TS-MSN allowed an improved internalization (3-4 times more compared to untargeted S-MSN) in HER2-overexpressing breast cancer cells (BT-474). Furthermore, anti-survivin siRNA delivered by TS-MSN in HER2-negative breast-cancer control cells (MDA-MB-231) allowed significant down-regulation of the targeted anti-apoptotic protein of about 70%. This protein down-regulation increased in HER2+ cells to about 90% (compared to 70% with S-MSN in both cell lines) indicating the contribution of the HER2-active targeting. In conclusion, TS-MSN are promising nanocarriers for the specific and efficient delivery of siRNA to HER2-overexpressing breast cancer cells.

Stealth magnetic nanocarriers of siRNA as platform for breast cancer theranostics.

The endogenous mechanism of RNA interference is more and more used in research to obtain specific down-regulation of gene expression in diseases such as breast cancer. Currently, despite the new fields of study open up by RNA interference, the rapid degradation of siRNA by nucleases and their negative charges prevent them from crossing cell membranes. To overcome these limitations, superparamagnetic iron oxide nanoparticles (SPIONs) represent a promising alternative for nucleic acid delivery. Previously, we reported the magnetic siRNA nanovectors (MSN) formulation using electrostatic assembly of (1) SPIONs, also able to act as contrast agents for magnetic resonance imaging (MRI), (2) siRNA and (3) chitosan aiming at their protection and enhancing their transfection efficacy. However, these nanoparticles displayed low stability in biological suspensions and inefficient transfection of active siRNA. This work aimed at upgrading MSN to Stealth MSN (S-MSN) by adding a polyethylene glycol coating to ensure colloidal stability and stealth properties. Furthermore, another polymer (poly-L-arginine) was added for efficient siRNA transfection and the quantitative composition of the formulation was adapted for biological purposes. Results showed that S-MSN provide high siRNA complexation and protection against enzymatic degradation. Green fluorescent protein (GFP) specific down-regulation on MDA-MB231/GFP cells was comparable to that of commercially available reagents, without observable cytotoxicity. According to our works, S-MSN appears as an effective formulation for in vitro siRNA specific delivery.

Design strategies of hybrid metallic nanoparticles for theragnostic applications.

Metallic nanoparticles (MNPs) such as iron oxide and gold nanoparticles are interesting platforms to build theragnostic nanocarriers which combine both therapeutic and diagnostic functions within a single nanostructure. Nevertheless, their surface must be functionalized to be suitable for in vivo applications. Surface functionalization also provides binding sites for targeting ligands, and for drug loading. This review focuses on the materials and surface chemistry used to build hybrid nanocarriers that are inorganic cores functionalized with organic materials. The surface state of the MNPs largely depends on their synthesis routes, and dictates the strategies used for functionalization. Two main strategies can be found in the literature: the design of core-shell nanosystems, or embedding nanoparticles in organic materials. Emerging tendencies such as the use of clusters or alternative coating materials are also described. To present both hydrophilic and lipophilic nanosystems, we chose the doxorubicin anticancer agent as an example, as the molecule presents an affinity for both types of materials.

Pegylated magnetic nanocarriers for doxorubicin delivery: a quantitative determination of stealthiness in vitro and in vivo.

The aim of this work was to elucidate the impact of polyethylene glycol (PEG) polymeric coating on the in vitro and in vivo stealthiness of magnetic nanocarriers loaded or not with the anticancer drug doxorubicin. The comparison was made between aqueous suspensions of superparamagnetic iron oxide nanoparticles (SPIONs) stabilized by either citrate ions (C-SPIONs) or PEG(5000) (P-SPIONs), the latter being loaded or not with doxorubicin via the formation of a DOX-Fe(2+) complex (DLP-SPIONs). After determination of their relevant physico-chemical properties (size and surface charge), nanoparticle (NP) stealthiness was studied in vitro (ability to activate the complement system and uptake by monocytes and macrophage-like cells) and in vivo in mice (blood half-life; t(1/2), and biodistribution in main clearance organs). These aspects were quantitatively assessed by atomic absorption spectrometry (AAS). Complement activation dramatically decreased for sterically stabilized P-SPIONs and DLP-SPIONs in comparison with C-SPIONs stabilized by charge repulsion. Monocyte and macrophage uptake was also largely reduced for pegylated formulations loaded or not with doxorubicin. The t(1/2) in blood for P-SPIONs was estimated to be 76 ± 6 min, with an elimination mainly directed to liver and spleen. Thanks to their small size (<80 nm) and a neutral hydrophilic polymer-extended surface, P-SPIONs exhibit prolonged blood circulation and thus potentially an increased level in tumor delivery suitable for magnetic drug targeting applications.