Targeted Dendrimer-Coated Magnetic Nanoparticles for Selective Delivery of Therapeutics in Living Cells.

Nanoparticles are widely used as theranostic agents for the treatment of various pathologies, including cancer. Among all, dendrimers-based nanoparticles represent a valid approach for drugs delivery, thanks to their controllable size and surface properties. Indeed, dendrimers can be easily loaded with different payloads and functionalized with targeting agents. Moreover, they can be used in combination with other materials such as metal nanoparticles for combinatorial therapies. Here, we present the formulation of an innovative nanostructured hybrid system composed by a metallic core and a dendrimers-based coating that is able to deliver doxorubicin specifically to cancer cells through a targeting agent. Its dual nature allows us to transport nanoparticles to our site of interest through the magnetic field and specifically increase internalization by exploiting the T7 targeting peptide. Our system can release the drug in a controlled pH-dependent way, causing more than 50% of cell death in a pancreatic cancer cell line. Finally, we show how the system was internalized inside cancer cells, highlighting a peculiar disassembly of the nanostructure at the cell surface. Indeed, only the dendrimeric portion is internalized, while the metal core remains outside. Thanks to these features, our nanosystem can be exploited for a multistage magnetic vector.

Design and characterization of antimicrobial usnic acid loaded-core/shell magnetic nanoparticles.

The application of magnetic nanoparticles (MNPs) in medicine is considered much promising especially because they can be handled and directed to specific body sites by external magnetic fields. MNPs have been investigated in magnetic resonance imaging, hyperthermia and drug targeting. In this study, properly functionalized core/shell MNPs with antimicrobial properties were developed to be used for the prevention and treatment of medical device-related infections. Particularly, surface-engineered manganese iron oxide MNPs, produced by a micro-emulsion method, were coated with two different polymers and loaded with usnic acid (UA), a dibenzofuran natural extract possessing antimicrobial activity. Between the two polymer coatings, the one based on an intrinsically antimicrobial cationic polyacrylamide (pAcDED) resulted to be able to provide MNPs with proper magnetic properties and basic groups for UA loading. Thanks to the establishment of acid-base interactions, pAcDED-coated MNPs were able to load and release significant drug amounts resulting in good antimicrobial properties versus Staphylococcus epidermidis (MIC = 0.1 mg/mL). The use of pAcDED having intrinsic antimicrobial activity as MNP coating in combination with UA likely contributed to obtain an enhanced antimicrobial effect. The developed drug-loaded MNPs could be injected in the patient soon after device implantation to prevent biofilm formation, or, later, in presence of signs of infection to treat the biofilm grown on the device surfaces.

Water-dispersible three-dimensional LC-nanoresonators.

Nanolithography techniques enable the fabrication of complex nanodevices that can be used for biosensing purposes. However, these devices are normally supported by a substrate and their use is limited to in vitro applications. Following a top-down procedure, we designed and fabricated composite inductance-capacitance (LC) nanoresonators that can be detached from their substrate and dispersed in water. The multimaterial composition of these resonators makes it possible to differentially functionalize different parts of the device to obtain stable aqueous suspensions and multi-sensing capabilities. For the first time, we demonstrate detection of these devices in an aqueous environment, and we show that they can be sensitized to their local environment and to chemical binding of specific molecular moieties. The possibility to optically probe the nanoresonator resonance in liquid dispersions paves the way to a variety of new applications, including injection into living organisms for in vivo sensing and imaging.

USPIO-loaded red blood cells as a biomimetic MR contrast agent: a relaxometric study.

Red blood cells (RBCs) loaded with iron oxide nanoparticles have been proposed as biomimetic constructs with long half-life (ca. 20 days) in the blood compartment and potentially interesting properties (such as relaxivity) as intravascular contrast agents for magnetic resonance imaging. However, the encapsulation of nanoparticles into RBCs might affect their magnetic properties and relaxivity, which may be significantly different from the native suspension. Here, we present a relaxometric study of P904, a novel ultra small iron oxide nanoparticle developed by Guerbet, enclosed in human RBCs. We measured longitudinal (r1 ) and transverse (r2 ) relaxivity over a wide range of Larmor frequencies (0.01-300 MHz) in samples of P904-loaded RBCs, and in control samples with P904 nanoparticles dispersed in blood. Internalization of P904 into RBCs resulted in smaller r1 , and in a very high r2 /r1 ratio (232) at the highest field. Moreover, a shift of the Curie peak to high fields was observed in P904-loaded RBCs, possibly the result of nanoparticle size selection caused by the internalization process. High r2 relaxivity together with a high r2 /r1 ratio and a very long blood half-life make P904-loaded RBCs a promising blood-pool negative contrast agent for MR diagnostic applications.

Surface functionalisation regulates polyamidoamine dendrimer toxicity on blood-brain barrier cells and the modulation of key inflammatory receptors on microglia.

Dendrimers are branched polymers with spherical morphology. Their tuneable chemistry and surface modification make them valuable nanomaterials for biomedical applications. In view of possible dendrimer uses as brain-aimed nanocarriers, the authors studied amine- and lipid-functionalised (G4) polyamidoamine (PAMAM) biocompatibility with cell population forming the blood-brain barrier (BBB). Both amine-PAMAM and lipid-PAMAM dendrimers were able to enter endothelial and primary neural cells. However, only amine-PAMAM damaged cell membranes in a dose-dependent manner. Transmission electron microscopy evidenced the ability of dendrimers to precipitate salts and serum components present in culture medium that slightly increased toxicity of the amine-PAMAM. Amine- and lipid-PAMAM were both able to cross the BBB and differently induced CD11b and CCR2 overexpression on primary CX3CR1-GFP murine microglia in vitro. These data emphasise the role of dendrimer surface functionalisation in toxicity and neural immune cell activation, raising concerns about possible neuroinflammatory reactions.

Gd-doped BNNTs as T2-weighted MRI contrast agents.

This work describes, for the first time, doping of boron nitride nanotubes (BNNTs) with gadolinium (Gd@BNNTs), a stable functionalization that permits non-invasive BNNT tracking via magnetic resonance imaging (MRI). We report the structure, Gd loading, and relaxometric properties in water suspension at 7 T of Gd@BNNTs, and show the behaviour of these nanostructures as promising T2-weighted contrast agents. Finally, we demonstrate their complete biocompatibility in vitro on human neuroblastoma cells, together with their ability to effectively label and affect contrast in MRI images at 7 T.

Water dispersal and functionalization of hydrophobic iron oxide nanoparticles with lipid-modified poly(amidoamine) dendrimers.

A novel and facile method for water dispersal of hydrophobic iron oxide nanoparticles based on the amphiphilic PAMAM-C12 dendrimer is described. Stable and highly concentrated water dispersions of multifunctional magnetic nanoparticles were obtained with this single-step approach, and showed interesting relaxometric properties for MRI applications. Importantly, this method does not require substitution of the native hydrophobic capping under nonmild reaction conditions, thus preserving the structural and magnetic properties of the nanoparticles, and extending the possibility of conjugation with thermally labile groups.

Cationic diiron and diruthenium µ-allenyl complexes: synthesis, X-ray structures and cyclization reactions with ethyldiazoacetate/amine affording unprecedented butenolide- and furaniminium-substituted bridging carbene ligands.

The novel cationic diiron µ-allenyl complexes [Fe(2)Cp(2)(CO)(2)(µ-CO){µ-η(1):η(2)(α,ß)-C(α)(H)=C(ß)=C(γ)(R)(2)}](+) (R = Me, 4a; R = Ph, 4b) have been obtained in good yields by a two-step reaction starting from [Fe(2)Cp(2)(CO)(4)]. The solid state structures of [4a][CF(3)SO(3)] and of the diruthenium analogues [Ru(2)Cp(2)(CO)(2)(µ-CO){µ-η(1):η(2)(α,ß)-C(α)(H)=C(ß)=C(γ)(R)(2)}][BPh(4)] (R = Me, [2a][BPh(4)]; R = Ph, [2c][BPh(4)]) have been ascertained by X-ray diffraction studies. The reactions of 2c and 4a with Brønsted bases result in formation of the µ-allenylidene compound [Ru(2)Cp(2)(CO)(2)(µ-CO){µ-η(1):η(1)-C(α)=C(ß)=C(γ)(Ph)(2)}] (5) and of the dimetallacyclopentenone [Fe(2)Cp(2)(CO)(µ-CO){µ-η(1):η(3)-C(α)(H)=C(ß)(C(γ)(Me)CH(2))C(=O)}] (6), respectively. The nitrile adducts [Ru(2)Cp(2)(CO)(NCMe)(µ-CO){µ-η(1):η(2)-C(α)(H)=C(ß)=C(γ)(R)(2)}](+) (R = Me, 7a; R = Ph, 7b), prepared by treatment of 2a,c with MeCN/Me(3)NO, react with N(2)CHCO(2)Et/NEt(3) at room temperature, affording the butenolide-substituted carbene complexes [Ru(2)Cp(2)(CO)(µ-CO){µ-η(1):η(3)-C(α)(H)[upper bond 1 start]C(ß)C(γ)(R)(2)OC(=O)C[upper bond 1 end](H)] (R = Me, 10a; R = Ph, 10b). The intermediate cationic compound [Ru(2)Cp(2)(CO)(µ-CO){µ-η(1):η(3)-C(α)(H)[upper bond 1 start]C(ß)C(γ)(Me)(2)OC(OEt)C[upper bond 1 end](H)](+) (9) has been detected in the course of the reaction leading to 10a. The addition of N(2)CHCO(2)Et/NHEt(2) to 7a gives the 2-furaniminium-carbene [Ru(2)Cp(2)(CO)(µ-CO){µ-η(1):η(3)-C(α)(H)[upper bond 1 start]C(ß)C(γ)(Me)(2)OC(OEt)C[upper bond 1 end](H)](+) (11). The X-ray structures of 10a, 10b and [11][BF(4)] have been determined. The reactions of 4a,b with MeCN/Me(3)NO result in prevalent decomposition to mononuclear iron species.