Unveiling the role of surface, size, shape and defects of iron oxide nanoparticles for theranostic applications.

Iron oxide nanoparticles (IONPs) are well-known contrast agents for MRI for a wide range of sizes and shapes. Their use as theranostic agents requires a better understanding of their magnetic hyperthermia properties and also the design of a biocompatible coating ensuring their stealth and a good biodistribution to allow targeting of specific diseases. Here, biocompatible IONPs of two different shapes (spherical and octopod) were designed and tested in vitro and in vivo to evaluate their abilities as high-end theranostic agents. IONPs featured a dendron coating that was shown to provide anti-fouling properties and a small hydrodynamic size favoring an in vivo circulation of the dendronized IONPs. While dendronized nanospheres of about 22 nm size revealed good combined theranostic properties (r2 = 303 mM s-1, SAR = 395 W gFe-1), octopods with a mean size of 18 nm displayed unprecedented characteristics to simultaneously act as MRI contrast agents and magnetic hyperthermia agents (r2 = 405 mM s-1, SAR = 950 W gFe-1). The extensive structural and magnetic characterization of the two dendronized IONPs reveals clear shape, surface and defect effects explaining their high performance. The octopods seem to induce unusual surface effects evidenced by different characterization techniques while the nanospheres show high internal defects favoring Néel relaxation for magnetic hyperthermia. The study of octopods with different sizes showed that Néel relaxation dominates at sizes below 20 nm while the Brownian one occurs at higher sizes. In vitro experiments demonstrated that the magnetic heating capability of octopods occurs especially at low frequencies. The coupling of a small amount of glucose on dendronized octopods succeeded in internalizing them and showing an effect of MH on tumor growth. All measurements evidenced a particular signature of octopods, which is attributed to higher anisotropy, surface effects and/or magnetic field inhomogeneity induced by tips. This approach aiming at an analysis of the structure-property relationships is important to design efficient theranostic nanoparticles.

Assessing the parameters modulating optical losses of iron oxide nanoparticles under near infrared irradiation.

Heating mediated by iron oxide nanoparticles subjected to near infrared irradiation has recently gained lots of interest. The high optical loss values reported in combination with the optical technologies already existing in current clinical practices, have made optical heating mediated by iron oxide nanoparticles an attractive choice for treating internal or skin tumors. However, the identification of the relevant parameters and the influence of methodologies for quantifying the optical losses released by iron oxide nanoparticles are not fully clear. Here, we report on a systematic study of different intrinsic (size, shape, crystallinity, and iron oxidation state) and extrinsic (aggregation, concentration, intracellular environment and irradiation conditions) parameters involved in the photothermal conversion of iron oxide nanoparticles under near infrared irradiation. We have probed the temperature increments to determine the specific loss power of iron oxide nanoparticles with different sizes and shapes dispersed in colloidal suspensions or inside live breast cancer cells. Our results underline the relevance of crystal surface defects, aggregation, concentration, magnetite abundance, excitation wavelength and density power on the modulation of the photothermal conversion. Contrary to plasmonic or magnetic losses, no significant influence of nanoparticle size nor shape was observed on the optical losses released by the studied iron oxide nanoparticles. Interestingly, no significant differences of measured temperature increments and specific loss power values were either observed when nanoparticles were inside live cells or in colloidal dispersion. Our findings highlight the advantages of optical heat losses released by iron oxide nanoparticles for therapeutic applications.

Dendronized oligoethylene glycols with phosphonate tweezers for cell-repellent coating of oxide surfaces: coarse-scale and nanoscopic interfacial forces.

Dendronized oligoethylene glycols (dendron OEGs) with two phosphonate groups (phosphonate tweezers) have been drawing significant attention as a new class of coating materials for superparamagnetic iron oxide surfaces. However, despite dendron OEGs showing outstanding stability in physiological fluids in previous studies, little is understood about their structure and mechanical properties. Herein we report the surface and internal structures and mechanical properties of dendron OEGs, and quantitatively determine their ability to avoid non-specific adhesion of blood platelets. To gain insight into the interfacial force interactions, we measured the coarse-scale surface force acting on cell-sized particles and mapped the nanoscopic pinning centers by fast force mapping.

Use of nanoparticles in skeletal tissue regeneration and engineering.

Bone and osteochondral defects represent one of the major causes of disabilities in the world. Derived from traumas and degenerative pathologies, these lesions cause severe pain, joint deformity, and loss of joint motion. The standard treatments in clinical practice present several limitations. By producing functional substitutes for damaged tissues, tissue engineering has emerged as an alternative in the treatment of defects in the skeletal system. Despite promising preliminary clinical outcomes, several limitations remain. Nanotechnologies could offer new solutions to overcome those limitations, generating materials more closely mimicking the structures present in naturally occurring systems. Nanostructures comparable in size to those appearing in natural bone and cartilage have thus become relevant in skeletal tissue engineering. In particular, nanoparticles allow for a unique combination of approaches (e.g. cell labelling, scaffold modification or drug and gene delivery) inside single integrated systems for optimized tissue regeneration. In the present review, the main types of nanoparticles and the current strategies for their application to skeletal tissue engineering are described. The collection of studies herein considered confirms that advanced nanomaterials will be determinant in the design of regenerative therapeutic protocols for skeletal lesions in the future.

Metronidazole-functionalized iron oxide nanoparticles for molecular detection of hypoxic tissues.

Being crucial under several pathological conditions, tumors, and tissue engineering, the MRI tracing of hypoxia within cells and tissues would be improved by the use of nanosystems allowing for direct recognition of low oxygenation and further treatment-oriented development. In the present study, we functionalized dendron-coated iron oxide nanoparticles (dendronized IONPs) with a bioreductive compound, a metronidazole-based ligand, to specifically detect the hypoxic tissues. Spherical IONPs with an average size of 10 nm were obtained and then decorated with the new metronidazole-conjugated dendron. The resulting nanoparticles (metro-NPs) displayed negligible effects on cell viability, proliferation, and metabolism, in both monolayer and 3D cell culture models, and a good colloidal stability in bio-mimicking media, as shown by DLS. Overtime quantitative monitoring of the IONP cell content revealed an enhanced intracellular retention of metro-NPs under anoxic conditions, confirmed by the in vitro MRI of cell pellets where a stronger negative contrast generation was observed in hypoxic primary stem cells and tumor cells after labeling with metro-NPs. Overall, these results suggest desirable properties in terms of interactions with the biological environment and capability of selective accumulation into the hypoxic tissue, and indicate that metro-NPs have considerable potential for the development of new nano-platforms especially in the field of anoxia-related diseases and tissue engineered models.

Interfacial Behavior of Oligo(Ethylene Glycol) Dendrons Spread Alone and in Combination with a Phospholipid as Langmuir Monolayers at the Air/Water Interface.

Dendrons consisting of two phosphonate functions and three oligo(ethylene glycol) (OEG) chains grafted on a central phenoxyethylcarbamoylphenoxy group were synthesized and investigated as Langmuir monolayers at the surface of water. The OEG chain in the para position was grafted with a t-Bu end-group, a hydrocarbon chain, or a partially fluorinated chain. These dendrons are models of structurally related OEG dendrons that were found to significantly improve the stability of aqueous dispersions of iron oxide nanoparticles when grafted on their surface. Compression isotherms showed that all OEG dendrons formed liquid-expanded Langmuir monolayers at large molecular areas. Further compression led to a transition ascribed to the solubilization of the OEG chains in the aqueous phase. Brewster angle microscopy (BAM) provided evidence that the dendrons fitted with hydrocarbon chains formed liquid-expanded monolayers throughout compression, whilst those fitted with fluorinated end-groups formed crystalline-like domains, even at large molecular areas. Dimyristoylphosphatidylcholine and dendron molecules were partially miscible in monolayers. The deviations to ideality were larger for the dendrons fitted with a fluorocarbon end-group chain than for those fitted with a hydrocarbon chain. Brewster angle microscopy and atomic force microscopy supported the view that the dendrons were ejected from the phospholipid monolayer during the OEG conformational transition and formed crystalline domains on the surface of the monolayer.

Microbubbles decorated with dendronized magnetic nanoparticles for biomedical imaging: effective stabilization via fluorous interactions.

Dendrons fitted with three oligo(ethylene glycol) (OEG) chains, one of which contains a fluorinated or hydrogenated end group and bears a bisphosphonate polar head (C n X2 n +1OEG8Den, X = F or H; n = 2 or 4), were synthesized and grafted on the surface of iron oxide nanoparticles (IONPs) for microbubble-mediated imaging and therapeutic purposes. The size and stability of the dendronized IONPs (IONP@C n X2 n +1OEG8Den) in aqueous dispersions were monitored by dynamic light scattering. The investigation of the spontaneous adsorption of IONP@C n X2 n +1OEG8Den at the interface between air or air saturated with perfluorohexane and an aqueous phase establishes that exposure to the fluorocarbon gas markedly increases the rate of adsorption of the dendronized IONPs to the gas/water interface and decreases the equilibrium interfacial tension. This suggests that fluorous interactions are at play between the supernatant fluorocarbon gas and the fluorinated end groups of the dendrons. Furthermore, small perfluorohexane-stabilized microbubbles (MBs) with a dipalmitoylphosphatidylcholine (DPPC) shell that incorporates IONP@C n X2 n +1OEG8Den (DPPC/Fe molar ratio 28:1) were prepared and subsequently characterized using both optical microscopy and an acoustical method of size determination. The dendrons fitted with fluorinated end groups lead to smaller and more stable MBs than those fitted with hydrogenated groups. The most effective result is already obtained with C2F5, for which MBs of ≈1.0 µm in radius reach a half-life of ≈6.0 h. An atomic force microscopy investigation of spin-coated mixed films of DPPC/IONP@C2X5OEG8Den combinations (molar ratio 28:1) shows that the IONPs grafted with the fluorinated dendrons are located within the phospholipid film, while those grafted with the hydrocarbon dendrons are located at the surface of the phospholipid film.

Macrophage functionality and homeostasis in response to oligoethyleneglycol-coated IONPs: Impact of a dendritic architecture.

The engineering of iron oxide nanoparticles (IONPs) for biomedical use has received great interest over the past decade. In the present study we investigated the biocompatibility of IONPs grafted with linear (2P) or generation 1 (2PG1) or 2 (2PG2) dendronized oligoethyleneglycol units in THP-1-derived macrophages. To evaluate IONP effects on cell functionality and homeostasis, mitochondrial function (MTT assay), membrane permeability (LDH release), inflammation (IL-8), oxidative stress (reduced glutathione, GSH), NLRP3 inflammasome activation (IL-1ß) and nanoparticle cellular uptake (intracellular iron content) were quantified after a 4-h or 24-h cell exposure to increasing IONP concentrations (0-300 µg Fe/mL). IONPs coated with a linear molecule, NP10COP@2P, were highly taken up by cells and induced significant dose-dependent IL-8 release, oxidative stress and NLRP3 inflammasome activation. In comparison, IONPs coated with dendrons of generation 1 (NP10COP@2PG1) and 2 (NP10COP@2PG2) exhibited better biocompatibility. Effect of the dendritic architecture of the surface coating was investigated in a kinetic experiment involving cell short-term exposure (30 min or 1 h 30) to the two dendronized IONPs. NP10COP@2PG2 disrupted cellular homeostasis (LDH release, IL-1ß and IL-8 secretion) to a greater extend than NP10COP@2PG1, which makes this last IONP the best candidate as MRI contrast or theranostic agent.

Umbelliferone Decreases Intracellular pH and Sensitizes Melanoma Cell Line A375 to Dacarbazin. Comparison with Acetazolamide.

BACKGROUND AND OBJECTIVE: The high degree of malignancy of tumour cells is linked to alterations of many physiological parameters like the intracellular pH (pHi). The pHi in cancer cell line is regulated by the carbonic anhydrase IX (CA IX). The main enzymatic function of the CA IX protein is to catalyze the hydration of carbon dioxide into bicarbonate ions and protons. CA IX expression in a broad variety of human tumor tissues is associated with resistance to therapy. One promising approach is to target the mechanism regulating pH homeostasis with carbonic anhydrase inhibitors like sulfamides and coumarins families. METHODS: In this work we have evaluated effects of umbelliferone and acetazolamide in a high resistant melanoma cell line (A375) over expressing CA IX. Impact of effective doses of CA IX inhibitors on apoptosis, intracellular pH (pHi), CA IX protein expression and functionality have been investigated. Determination of effective doses of CA IX inhibitors was performed with MTT tests. We also evaluated sensitization effect of CA inhibitors to conventional therapy as dacarbazin. RESULTS: We have used 10 µM Umbelliferone and 100 µM Acetazolamide as effective doses for 24h. These doses did not induce any apoptosis. Umbelliferone induced a more important pHi decrease than Acetalozamide from 7.3 to 7.08 and to 7.12 respectively, and a more important decrease in s-CA IX fraction showing a decrease in CA IX function. We have demonstrated that pre-treatment with umbelliferone or acetazolamide allows a better dacarbazin efficacy. CONCLUSION: We have demonstrated that inhibitors modify intracellular pH and CAIX functionality and sensitize cells to Dacarbazin. These original results complete the knowledge on Sulfamide CA IX inhibitors, bring new insights about Coumarin compounds and offer new possibilities in high grade melanoma therapies.

Effect of the Functionalization Process on the Colloidal, Magnetic Resonance Imaging, and Bioelimination Properties of Mono- or Bisphosphonate-Anchored Dendronized Iron Oxide Nanoparticles.

The functionalization process of iron oxide nanoparticles (NPs) is a major step and has to ensure a small particle size distribution (below 100 nm) and to preserve good magnetic properties suitable for in vivo applications. Two functionalization processes are here compared to coat iron oxide NPs, synthesized by thermal decomposition, with dendron molecules bearing either a mono- or a bisphosphonate anchoring group. The two processes are direct ligand exchange and the simultaneous ligand exchange and phase transfer process. The latter process led to a larger size distribution than the former. The phosphonate group is confirmed to be a strong anchoring agent from X-ray photoelectron spectroscopy (XPS) and IR characterizations whatever the grafting process and the number of phosphonate groups, it also confirms the preservation of the NPs' magnetic properties. All dendronized NPs display good in vitro MRI properties and those obtained by direct exchange showed no cell internalization, an efficient in vivo MRI contrast enhancement, and elimination by both urinary and hepato-biliary ways.

Design of iron oxide-based nanoparticles for MRI and magnetic hyperthermia.

Iron oxide nanoparticles are widely used for biological applications thanks to their outstanding balance between magnetic properties, surface-to-volume ratio suitable for efficient functionalization and proven biocompatibility. Their development for MRI or magnetic particle hyperthermia concentrates much of the attention as these nanomaterials are already used within the health system as contrast agents and heating mediators. As such, the constant improvement and development for better and more reliable materials is of key importance. On this basis, this review aims to cover the rational design of iron oxide nanoparticles to be used as MRI contrast agents or heating mediators in magnetic hyperthermia, and reviews the state of the art of their use as nanomedicine tools.

Preparation of core/shell NaYF4:Yb,Tm@dendrons nanoparticles with enhanced upconversion luminescence for in vivo imaging.

Upconverting nanoparticles (UCNPs) were successfully dendronized for fluorescence medical imaging applications. The structural and morphological characterizations of resulting core/shell NaYF4:Yb,Tm@dendrons nanoparticles were performed by means of X-ray diffraction, infrared spectroscopy and transmission electron microscopy. In vitro cytotoxicity assays have evidenced their low toxicity. In vivo fluorescence imaging study was performed in mice upon IR excitation, showing promising imaging capacities at low concentrations (0.5mg/mL) and low power (50mW/cm2).

Exohedral M-C60 and M2-C60 (M = Pt, Pd) systems as tunable-gap building blocks for nanoarchitecture and nanocatalysis.

Transition metal-fullerenes complexes with metal atoms bound on the external surface of C60 are promising building blocks for next-generation fuel cells and catalysts. Yet, at variance with endohedral M@C60, they have received a limited attention. By resorting to first principles simulations, we elucidate structural and electronic properties for the Pd-C60, Pt-C60, PtPd-C60, Pd2-C60, and Pt2-C60 complexes. The most stable structures feature the metal atom located above a high electron density site, namely, the π bond between two adjacent hexagons (π-66 bond). When two metal atoms are added, the most stable configuration is those in which metal atoms still stand on π-66 bonds but tends to clusterize. The electronic structure, rationalized in terms of localized Wannier functions, provides a clear picture of the underlying interactions responsible for the stability or instability of the complexes, showing a strict relationship between structure and electronic gap.

Selective Nanotrench Filling by One-Pot Electroclick Self-Constructed Nanoparticle Films.

Integration of nanoparticles (NPs) into nanodevices is a challenge for enhanced sensor development. Using NPs as building blocks, a bottom-up approach based on one-pot morphogen-driven electroclick chemistry is reported to self-construct dense and robust conductive Fe3O4 NP films. Deposited covalent NP assemblies establish an electrical connection between two gold electrodes separated by a 100 nm-wide nanotrench.

Dendrimer-nanoparticle conjugates in nanomedicine.

Nanomedicine can take advantage of the recent developments in nanobiotechnology research areas for the creation of platforms with superior drug carrier capabilities, selective responsiveness to the environment, unique contrast enhancement profiles and improved accumulation at the disease site. Colloidal inorganic nanoparticles (NPs) have been attracting considerable interest in biomedicine, from drug and gene delivery to imaging, sensing and diagnostics. It is essential to modify the NPs surface to have enhanced biocompatibility and reach multifunctional systems for the in vitro and in vivo applications, especially in delivering drugs locally and recognizing overexpressed biomolecules. This paper describes the rational design for dendrimer-nanoparticle conjugates elaboration and reviews their state-of-the-art uses as efficient nanomedicine tools.

Radiolabeled dendritic probes as tools for high in vivo tumor targeting: application to melanoma.

In bioimaging, targeting allows refining the diagnosis by improving the sensitivity and especially the specificity for an earlier diagnosis. Two 111In-radiolabeled dendritic nanoprobes (DPs) (111In-2, 111In-3) and their model counterparts (111In-1, 111In-4) are designed and assessed for in vitro and in vivo tumor targeting efficiency in a murine melanoma models. Tumor uptake is correlated to dendrimer multivalency and reaches values as high as 12.7 ± 1.6% ID g-1 at 4 h post intravenous injection for 111In-3vs. 1.5 ± 0.5% ID g-1 for the unfunctionalized DP, and over 11% ID g-1 for any tumor weight whatsoever.

A strongly emitting liquid-crystalline derivative of Y(3)N@C(80): bright and long-lived near-IR luminescence from a charge transfer state.

Great balls of fire: C60 and Y3 N@C80 were connected to the same oligo(phenyleneethynylene) unit to investigate their structural and photophysical properties. NMR investigations revealed a fulleroid structure for the Y3 N@C80 derivative, and both dyads gave rise to columnar phases with core-shell cylinders. The black and gray spheres represent the fullerene core units of the Y3 N@C80 derivative, which is an ideal candidate to be involved in energy and electron transfer processes.

A bisphosphonate tweezers and clickable PEGylated PAMAM dendrons for the preparation of functional iron oxide nanoparticles displaying renal and hepatobiliary elimination.

The functionalization of superparamagnetic iron oxide nanoparticles (SPION) with PEGylated PAMAM dendrons through a bisphosphonate tweezers yielded 15 and 30 nm dendritic nano-objects stable in physiological media and showing both renal and hepatobiliary elimination.

Endowing carbon nanotubes with superparamagnetic properties: applications for cell labeling, MRI cell tracking and magnetic manipulations.

Coating of carbon nanotubes (CNTs) with magnetic nanoparticles (NPs) imparts novel magnetic, optical, and thermal properties with potential applications in the biomedical domain. Multi-walled CNTs have been decorated with iron oxide superparamagnetic NPs. Two different approaches have been investigated based on ligand exchange or "click chemistry". The presence of the NPs on the nanotube surface allows conferring magnetic properties to CNTs. We have evaluated the potential of the NP/CNT hybrids as a contrast agent for magnetic resonance imaging (MRI) and their interactions with cells. The capacity of the hybrids to magnetically monitor and manipulate cells has also been investigated. The NP/CNTs can be manipulated by a remote magnetic field with enhanced contrast in MRI. They are internalized into tumor cells without showing cytotoxicity. The labeled cells can be magnetically manipulated as they display magnetic mobility and are detected at a single cell level through high resolution MRI.

Effect of the nanoparticle synthesis method on dendronized iron oxides as MRI contrast agents.

Aqueous suspensions of dendronized iron oxide nanoparticles (NPs) have been obtained after functionalization, with two types of dendrons, of NPs synthesized either by coprecipitation (leading to naked NPs in water) or by thermal decomposition (NPs in situ coated by oleic acid in an organic solvent). Different grafting strategies have been optimized depending on the NPs synthetic method. The size distribution, the colloidal stability in isoosmolar media, the surface complex nature as well as the preliminary biokinetic studies performed with optical imaging, and the contrast enhancement properties evaluated through in vitro and in vivo MRI experiments, have been compared as a function of the nature of both dendrons and NPs. All functionalized NPs displayed good colloidal stability in water, however the ones bearing a peripheral carboxylic acid function gave the best results in isoosmolar media. Whereas the grafting rates were similar, the nature of the surface complex depended on the NPs synthetic method. The in vitro contrast enhancement properties were better than commercial products, with a better performance of the NPs synthesized by coprecipitation. On the other hand, the NPs synthesized by thermal decomposition were more efficient in vivo. Furthermore, they both displayed good biodistribution with renal and hepatobiliary elimination pathways and no consistent RES uptake.