Comparison of Anti-Dengue and Anti-Zika IgG on a Plasmonic Gold Platform with Neutralization Testing.

Antibody cross-reactivity confounds testing for dengue virus (DENV) and Zika virus (ZIKV). We evaluated anti-DENV and anti-ZIKV IgG detection using a multiplex serological platform (the pGOLD assay, Nirmidas, Palo Alto, CA) in patients from the Asunción metropolitan area in Paraguay, which experiences annual DENV outbreaks but has reported few autochthonous ZIKV infections. Acute-phase sera were tested from 77 patients who presented with a suspected arboviral illness from January to May 2018. Samples were tested for DENV and ZIKV RNA by real-time reverse transcription-PCR, and for DENV nonstructural protein 1 with a lateral-flow immunochromatographic test. Forty-one patients (51.2%) had acute dengue; no acute ZIKV infections were detected. Sixty-five patients (84.4%) had anti-DENV-neutralizing antibodies by focus reduction neutralization testing (FRNT50). Qualitative detection with the pGOLD assay demonstrated good agreement with FRNT50 (kappa = 0.74), and quantitative results were highly correlated between methods (P < 0.001). Only three patients had anti-ZIKV-neutralizing antibodies at titers of 1:55-1:80, and all three had corresponding DENV-neutralizing titers > 1:4,000. Hospitalized dengue cases had significantly higher anti-DENV IgG levels (P < 0.001). Anti-DENV IgG results from the pGOLD assay correlate well with FRNT, and quantitative results may inform patient risk stratification.

Targeted nanoparticle delivery of therapeutic antisense microRNAs presensitizes glioblastoma cells to lower effective doses of temozolomide in vitro and in a mouse model.

Temozolomide (TMZ) chemotherapy for glioblastoma (GBM) is generally well tolerated at standard doses but it can cause side effects. GBMs overexpress microRNA-21 and microRNA-10b, two known oncomiRs that promote cancer development, progression and resistance to drug treatment. We hypothesized that systemic injection of antisense microRNAs (antagomiR-21 and antagomiR-10b) encapsulated in cRGD-tagged PEG-PLGA nanoparticles would result in high cellular delivery of intact functional antagomiRs, with consequent efficient therapeutic response and increased sensitivity of GBM cells to lower doses of TMZ. We synthesized both targeted and non-targeted nanoparticles, and characterized them for size, surface charge and encapsulation efficiency of antagomiRs. When using targeted nanoparticles in U87MG and Ln229 GBM cells, we showed higher uptake-associated improvement in sensitivity of these cells to lower concentrations of TMZ in medium. Co-inhibition of microRNA-21 and microRNA-10b reduced the number of viable cells and increased cell cycle arrest at G2/M phase upon TMZ treatment. We found a significant increase in expression of key target genes for microRNA-21 and microRNA-10b upon using targeted versus non-targeted nanoparticles. There was also significant reduction in tumor volume when using TMZ after pre-treatment with loaded nanoparticles in human GBM cell xenografts in mice. In vivo targeted nanoparticles plus different doses of TMZ showed a significant therapeutic response even at the lowest dose of TMZ, indicating that preloading cells with antagomiR-21 and antagomiR-10b increases cellular chemosensitivity towards lower TMZ doses. Future clinical applications of this combination therapy may result in improved GBM response by using lower doses of TMZ and reducing nonspecific treatment side effects.

Diagnosis of Zika virus infection on a nanotechnology platform.

We developed a multiplexed assay on a plasmonic-gold platform for measuring IgG and IgA antibodies and IgG avidity against both Zika virus (ZIKV) and dengue virus (DENV) infections. In contrast to IgM cross-reactivity, IgG and IgA antibodies against ZIKV nonstructural protein 1 (NS1) antigen were specific to ZIKV infection, and IgG avidity revealed recent ZIKV infection and past DENV-2 infection in patients in dengue-endemic regions. This assay could enable specific diagnosis of ZIKV infection over other flaviviral infections.

Tailored Nanoparticle Codelivery of antimiR-21 and antimiR-10b Augments Glioblastoma Cell Kill by Temozolomide: Toward a "Personalized" Anti-microRNA Therapy.

Glioblastoma remains an aggressive brain malignancy with poor prognosis despite advances in multimodal therapy that include standard use of Temozolomide. MicroRNA-21 (miR-21) and microRNA-10b (miR-10b) are oncomiRs overexpressed in glioblastoma, promoting many aspects of cancer biology. We hypothesized that PLGA nanoparticles carrying antisense miR-21 (antimiR-21) and antisense miR-10b (antimiR-10b) might beneficially knockdown endogenous miR-21 and miR-10b function and reprogram cells prior to Temozolomide treatment. PLGA nanoparticles were effective in intracellular delivery of encapsulated oligonucleotides. Concentrations of delivered antimiR-21 and antimiR-10b were optimized and specifically tailored to copy numbers of intracellular endogenous microRNAs. Coinhibition of miR-21 and miR-10b significantly reduced the number of viable cells (by 24%; p < 0.01) and increased (2.9-fold) cell cycle arrest at G2/M phase upon Temozolomide treatment in U87 MG cells. Cell-tailored nanoparticle-assisted concurrent silencing of miR-21 and miR-10b prior to Temozolomide treatment is an effective molecular therapeutic strategy in cell culture, warranting the need for further studies prior to future in vivo "personalized" medicine applications.

Temozolomide-loaded PLGA nanoparticles to treat glioblastoma cells: a biophysical and cell culture evaluation.

OBJECTIVES: Current chemotherapies for brain glioblastoma do not achieve sufficient drug concentrations within tumors. Polymeric nanoparticles have useful physicochemical properties that make them promising as nanoparticle platforms for glioblastoma drug delivery. Poly[lactic-co-glycolic acid] (PLGA) nanoparticles encapsulating temozolomide (TMZ) could improve localized delivery and sustained drug release to glioblastomas. METHODS: We investigated three different procedures to encapsulate TMZ within PLGA nanoparticles. We studied the biophysical features of optimized nanocarriers, including their size, shape, surface properties, and release characteristics of TMZ. We evaluated the antiproliferative and cytotoxic effects of TMZ-loaded PLGA nanoparticles on U87 MG glioblastoma cells. RESULTS: A single emulsion technique using a TMZ saturated aqueous phase produced nanoparticles ≤200 nm in size allowing a maximal drug loading of 4.4% w/w of polymer. There was a bi-phasic drug release pattern, with 80% of TMZ released within the first 6 h. Nanoparticles accumulated in the cytoplasm after effective endocytosis. There was no significant difference in cytotoxic effect of TMZ encapsulated within PLGA nanoparticles and free TMZ. CONCLUSIONS: PLGA nanoparticles are not suitable as carriers of TMZ for glioblastoma drug delivery on account of the overall high IC50 values of glioblastoma cells to TMZ and poor loading and encapsulation efficiencies. Further biotechnological developments aimed at improving the loading of TMZ in PLGA nanoparticles or co-delivery of small molecule sensitizers to improve the response of human glioblastoma cells to TMZ are required for this approach to be considered and optimized for future clinical translation.

Folate Receptor-Targeted Polymeric Micellar Nanocarriers for Delivery of Orlistat as a Repurposed Drug against Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is a recalcitrant malignancy with no available targeted therapy. Off-target effects and poor bioavailability of the FDA-approved antiobesity drug orlistat hinder its clinical translation as a repurposed new drug against TNBC. Here, we demonstrate a newly engineered drug formulation for packaging orlistat tailored to TNBC treatment. We synthesized TNBC-specific folate receptor-targeted micellar nanoparticles (NP) carrying orlistat, which improved the solubility (70-80 µg/mL) of this water-insoluble drug. The targeted NPs also improved the delivery and bioavailability of orlistat to MDA-MB-231 cells in culture and to tumor xenografts in a nude mouse model. We prepared HEA-EHA copolymer micellar NPs by copolymerization of 2-hydroxyethylacrylate (HEA) and 2-ethylhexylacrylate (EHA), and functionalized them with folic acid and an imaging dye. Fluorescence-activated cell sorting (FACS) analysis of TNBC cells indicated a dose-dependent increase in apoptotic populations in cells treated with free orlistat, orlistat NPs, and folate-receptor-targeted Fol-HEA-EHA-orlistat NPs in which Fol-HEA-EHA-orlistat NPs showed significantly higher cytotoxicity than free orlistat. In vitro analysis data demonstrated significant apoptosis at nanomolar concentrations in cells activated through caspase-3 and PARP inhibition. In vivo analysis demonstrated significant antitumor effects in living mice after targeted treatment of tumors, and confirmed by fluorescence imaging. Moreover, folate receptor-targeted Fol-DyLight747-orlistat NP-treated mice exhibited significantly higher reduction in tumor volume compared to control group. Taken together, these results indicate that orlistat packaged in HEA-b-EHA micellar NPs is a highly promising new drug formulation for TNBC therapy. Mol Cancer Ther; 15(2); 221-31. ©2015 AACR.

Nanoparticle-Delivered Antisense MicroRNA-21 Enhances the Effects of Temozolomide on Glioblastoma Cells.

Glioblastoma (GBM) generally exhibits high IC50 values for its standard drug treatment, temozolomide (TMZ). MicroRNA-21 (miR-21) is an oncomiR overexpressed in GBM, thus controlling important aspects of glioma biology. We hypothesized that PLGA nanoparticles carrying antisense miR-21 to glioblastoma cells might beneficially knock down endogenous miR-21 prior to TMZ treatment. PLGA nanoparticles encapsulating antisense miR-21 were effective in intracellular delivery and sustained silencing (p < 0.01) of miR-21 function in U87 MG, LN229, and T98G cells. Prior antisense miR-21 delivery significantly reduced the number of viable cells (p < 0.001), and increased (1.6-fold) cell cycle arrest at G2/M phase upon TMZ treatment in U87 MG cells. There was overexpression of the miR-21 target genes PTEN (by 67%) and caspase-3 (by 15%) upon cotreatment. This promising PLGA nanoparticle-based platform for antisense miR-21 delivery to GBM is an effective cotherapeutic strategy in cell culture, warranting the need for further studies prior to future clinical translation.

Encapsulation of α-Particle-Emitting 225Ac3+ Ions Within Carbon Nanotubes.

UNLABELLED: (225)Ac(3+) is a generator of α-particle-emitting radionuclides with 4 net α-particle decays that can be used therapeutically. Targeting (225)Ac(3+) by use of ligands conjugated to traditional bifunctional chelates limits the amount of (225)Ac(3+) that can be delivered. Ultrashort, single-walled carbon nanotubes (US-tubes), previously demonstrated as sequestering agents of trivalent lanthanide ions and small molecules, also successfully incorporate (225)Ac(3+). METHODS: Aqueous loading of both (225)Ac(3+) ions and Gd(3+) ions via bath sonication was used to construct (225)Ac@gadonanotubes ((225)Ac@GNTs). The (225)Ac@GNTs were subsequently challenged with heat, time, and human serum. RESULTS: US-tubes internally loaded with both (225)Ac(3+) ions and Gd(3+) ions show 2 distinct populations of (225)Ac(3+) ions: one rapidly lost in human serum and one that remains bound to the US-tubes despite additional challenge with heat, time, and serum. The presence of the latter population depended on cosequestration of Gd(3+) and (225)Ac(3+) ions. CONCLUSION: US-tubes successfully sequester (225)Ac(3+) ions in the presence of Gd(3+) ions and retain them after a human serum challenge, rendering (225)Ac@GNTs candidates for radioimmunotherapy for delivery of (225)Ac(3+) ions at higher concentrations than is currently possible for traditional ligand carriers.

Gadolinium-conjugated gold nanoshells for multimodal diagnostic imaging and photothermal cancer therapy.

Multimodal imaging offers the potential to improve diagnosis and enhance the specificity of photothermal cancer therapy. Toward this goal, gadolinium-conjugated gold nanoshells are engineered and it is demonstrated that they enhance contrast for magnetic resonance imaging, X-ray, optical coherence tomography, reflectance confocal microscopy, and two-photon luminescence. Additionally, these particles effectively convert near-infrared light to heat, which can be used to ablate cancer cells. Ultimately, these studies demonstrate the potential of gadolinium-nanoshells for image-guided photothermal ablation.

Engineered magnetic hybrid nanoparticles with enhanced relaxivity for tumor imaging.

Clinically used contrast agents for magnetic resonance imaging (MRI) suffer by the lack of specificity; short circulation time; and insufficient relaxivity. Here, a one-step combinatorial approach is described for the synthesis of magnetic lipid-polymer (hybrid) nanoparticles (MHNPs) encapsulating 5 nm ultra-small super-paramagnetic iron oxide particles (USPIOs) and decorated with Gd(3+) ions. The MHNPs comprise a hydrophobic poly(lactic acid-co-glycolic acid) (PLGA) core, containing up to ~5% USPIOs (w/w), stabilized by lipid and polyethylene glycol (PEG). Gd(3+) ions are directly chelated to the external lipid monolayer. Three different nanoparticle configurations are presented including Gd(3+) chelates only (Gd-MHNPs); USPIOs only (Fe-MHNPs); and the combination thereof (MHNPs). All three MHNPs exhibit a hydrodynamic diameter of about 150 nm. The Gd-MHNPs present a longitudinal relaxivity (r1 = 12.95 ± 0.53 (mM s)(-1)) about four times larger than conventional Gd-based contrast agents (r1 = 3.4 (mM s)(-1)); MHNPs have a transversal relaxivity of r2 = 164.07 ± 7.0 (mM s)(-1), which is three to four times larger than most conventional systems (r2 ~ 50 (mM s)(-1)). In melanoma bearing mice, elemental analysis for Gd shows about 3% of the injected MHNPs accumulating in the tumor and 2% still circulating in the blood, at 24 h post-injection. In a clinical 3T MRI scanner, MHNPs provide significant contrast confirming the observed tumor deposition. This approach can also accommodate the co-loading of hydrophobic therapeutic compounds in the MHNP core, paving the way for theranostic systems.

Engineering discoidal polymeric nanoconstructs with enhanced magneto-optical properties for tumor imaging.

The in vivo performance of nanoparticles is affected by their size, shape and surface properties. Fabrication methods based on emulsification and nano-precipitation cannot control these features precisely and independently over multiple scales. Herein, discoidal polymeric nanoconstructs (DPNs) with a diameter of 1000 nm and a height of 500 nm are demonstrated via a modified hydrogel-template strategy. The DPNs are obtained by mixing in one synthesis step the constituent polymers - poly(lactic acid-co-glycolic acid) (PLGA) and polyethylene glycol (PEG) dimethacrylate - and the payload with magneto-optical properties - 5 nm ultra-small super-paramagnetic iron oxide nanoparticles (SPIOs) and Rhodamine B dye (RhB). The DPN geometrical features are characterized by multiple microscopy techniques. The release of the Rhodamine B dye is pH dependent and increases under acidic conditions by the enhanced hydrolysis of the polymeric matrix. Each DPN is loaded with ~100 fg of iron and can be efficiently dragged by static and external magnetic fields. Moreover, the USPIO confinement within the DPN porous structure is responsible for a significant enhancement in MRI relaxivity (r2 ~ 500 (mMs)(-1)), up to ~5 times larger than commercially available systems. These nanoconstructs suggest a general strategy to engineer theranostic systems for anti-angiogenic treatment and vascular imaging.

Enhanced MRI relaxivity of Gd(3+) -based contrast agents geometrically confined within porous nanoconstructs.

Gadolinium chelates, which are currently approved for clinical MRI use, provide relaxivities well below their theoretical limit, and they also lack tissue specificity. Recently, the geometrical confinement of Gd(3+) -based contrast agents (CAs) within porous structures has been proposed as a novel, alternative strategy to improve relaxivity without chemical modification of the CA. Here, we have characterized and optimized the performance of MRI nanoconstructs obtained by loading [Gd(DTPA)(H(2) O)](2-) (Magnevist®) into the pores of injectable mesoporous silicon particles. Nanoconstructs with three different pore sizes were studied, and at 60 MHz, they exhibited longitudinal relaxivities of ~24 m m(-1) s(-1) for 5-10 nm pores and ~10 m m(-1) s(-1) for 30 - 40 nm pores. No enhancement in relaxivity was observed for larger pores sizes. Using an outer-sphere compound, [GdTTHA](3-) , and mathematical modeling, it was demonstrated that the relaxivity enhancement is due to the increase in rotational correlation times (CA adsorbed on the pore walls) and diffusion correlation times (reduced mobility of the water molecules), as the pore sizes decreases. It was also observed that extensive CA adsorption on the outer surface of the silicon particles negates the advantages offered by nanoscale confinement. Upon incubation with HeLa cells, the nanoconstructs did not demonstrate significant cytotoxicity for up to 3 days post incubation, at different particle/cell ratios. In addition, the nanoconstructs showed complete degradation after 24 h of continuous agitation in phosphate-buffered saline. These data support and confirm the hypothesis that the geometrical confinement of Gd(3+) -chelate compounds into porous structures offers MRI nanoconstructs with enhanced relaxivity (up to 6 times for [Gd(DTPA)(H(2) O)](2-) , and 4 times for [GdTTHA](3-) ) and, potentially, improved stability, reduced toxicity and tissue specificity.

Cellular uptake and imaging studies of gadolinium-loaded single-walled carbon nanotubes as MRI contrast agents.

We quantify here, for the first time, the intracellular uptake (J774A.1 murine macrophage cells) of gadolinium-loaded ultra-short single-walled carbon nanotubes (gadonanotubes or GNTs) in a 3 T MRI scanner using R(2) and R(2)* mapping in vitro. GNT-labeled cells exhibited high and linear changes in net transverse relaxations (ΔR(2) and ΔR 2*) with increasing cell concentration. The measured ΔR(2)* were about three to four times greater than the respective ΔR(2) for each cell concentration. The intracellular uptake of GNTs was validated with inductively coupled plasma optical emission spectrometry (ICP-OES), indicating an average cellular uptake of 0.44 ± 0.09 pg Gd per cell or 1.69 × 10(9) Gd(3+) ions per cell. Cell proliferation MTS assays demonstrated that the cells were effectively labeled, without cytotoxicity, for GNTs concentrations ≤28 µM Gd. In vivo relaxometry of a subcutaneously-injected GNT-labeled cell pellet in a mouse was also demonstrated at 3 T. Finally, the pronounced R(2)* effect of GNT-labeled cells enabled successful in vitro visualization of labeled cells at 9.4 T.

In vivo magnetic resonance imaging of the distribution pattern of gadonanotubes released from a degrading poly(lactic-co-glycolic Acid) scaffold.

To improve the mechanical properties of polymers used in bone repair, it has been suggested to incorporate single-walled carbon nanotubes (CNTs). However, concern exists about the biosafety of the CNTs in vivo. Therefore, the aim of this study was to develop a magnetic resonance imaging technique to examine the distribution pattern of CNTs after release from a degrading poly(lactic-co-glycolic acid) (PLGA) scaffold in vivo. Five rats received a PLGA scaffold with incorporated gadolinium-labeled single-walled CNTs ("gadonanotubes") subcutaneously. The rats were analyzed up to 5 weeks, subsequently euthanized, followed by histological evaluation of the explanted scaffolds with their surrounding tissue. A significant increase in intensity of the scaffold surrounding tissue was shown in the time period around 3 weeks, as compared to internal control areas. The intensity declined soon thereafter. This is suggested to be caused by the release of gadonanotubes from the degrading scaffold into the surrounding tissue. Histological imaging showed encapsulation by connective fibrous tissue and some mild inflammation around the scaffolds. In conclusion, magnetic resonance imaging is an excellent technique to study the biological fate of gadonanotubes. However, to formulate solid conclusions on the distribution pattern of gadonanotubes in vivo the experimental setup requires further optimization.

Geometrical confinement of gadolinium-based contrast agents in nanoporous particles enhances T1 contrast.

Magnetic resonance imaging contrast agents are currently designed by modifying their structural and physiochemical properties to improve relaxivity and to enhance image contrast. Here, we show a general method for increasing relaxivity by confining contrast agents inside the nanoporous structure of silicon particles. Magnevist, gadofullerenes and gadonanotubes were loaded inside the pores of quasi-hemispherical and discoidal particles. For all combinations of nanoconstructs, a boost in longitudinal proton relaxivity r(1) was observed: Magnevist, r(1) ≈ 14 mM(-1) s(-1)/Gd(3+) ion (∼ 8.15 × 10(+7) mM(-1) s(-1)/construct); gadofullerenes, r(1) ≈ 200 mM(-1) s(-1)/Gd(3+) ion (∼ 7 × 10(+9) mM(-1) s(-1)/construct); gadonanotubes, r(1) ≈ 150 mM(-1) s(-1)/Gd(3+) ion (∼ 2 × 10(+9) mM(-1) s(-1)/construct). These relaxivity values are about 4 to 50 times larger than those of clinically available gadolinium-based agents (∼ 4 mM(-1) s(-1)/Gd(3+) ion). The enhancement in contrast is attributed to the geometrical confinement of the agents, which influences the paramagnetic behaviour of the Gd(3+) ions. Thus, nanoscale confinement offers a new and general strategy for enhancing the contrast of gadolinium-based contrast agents.

Three-dimensional tissue culture based on magnetic cell levitation.

Cell culture is an essential tool in drug discovery, tissue engineering and stem cell research. Conventional tissue culture produces two-dimensional cell growth with gene expression, signalling and morphology that can be different from those found in vivo, and this compromises its clinical relevance. Here, we report a three-dimensional tissue culture based on magnetic levitation of cells in the presence of a hydrogel consisting of gold, magnetic iron oxide nanoparticles and filamentous bacteriophage. By spatially controlling the magnetic field, the geometry of the cell mass can be manipulated, and multicellular clustering of different cell types in co-culture can be achieved. Magnetically levitated human glioblastoma cells showed similar protein expression profiles to those observed in human tumour xenografts. Taken together, these results indicate that levitated three-dimensional culture with magnetized phage-based hydrogels more closely recapitulates in vivo protein expression and may be more feasible for long-term multicellular studies.

In vivo behavior of large doses of ultrashort and full-length single-walled carbon nanotubes after oral and intraperitoneal administration to Swiss mice.

Carbon nanotube (CNT) materials are of special interest as potential tools for biomedical applications. However, available toxicological data concerning single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes (MWNTs) remain contradictory. Here, we compared the effects of SWNTs as a function of dose, length, and surface chemistry in Swiss mice. Transmission electron microscopy (TEM), Raman, near-infrared (NIR), and X-ray photoelectron spectroscopies have been used to characterize the tested materials. The dose of SWNT materials used in this study is considerably higher than that proposed for most biomedical applications, but it was deemed necessary to administer such large doses to accurately assess the toxicological impact of the materials. In an acute toxicity test, SWNTs were administered orally at a dose level of 1000 mg/kg bodyweight (b.w.). Neither death nor growth or behavioral troubles were observed. After intraperitoneal administration, SWNTs, irrespective of their length or dose (50-1000 mg/kg b.w.), can coalesce inside the body to form fiberlike structures. When structure lengths exceeded 10 mum, they irremediably induced granuloma formation. Smaller aggregates did not induce granuloma formation, but they persisted inside cells for up to 5 months after administration. Short (<300 nm) well-individualized SWNTs can escape the reticuloendothelial system to be excreted through the kidneys and bile ducts. These findings suggest that if the potential of SWNTs for medical applications is to be realized, they should be engineered into discrete, individual "molecule-like" species.

Serine-derivatized gadonanotubes as magnetic nanoprobes for intracellular labeling.

Gadonanotubes (GNTs), which are powerful new T(1)-weighted MRI contrast agents, were derivatized with serine amino acid substituents to produce water-soluble (2 mg ml(-1)) ser-gadonanotubes (ser-GNs) as magnetic nanoprobes for intracellular labeling. The ser-GNTs were used to efficiently label MCF-7 human breast cancer cells (1.5 x 10(9) Gd(3+) ions/cell) with no observable cytotoxicity. Cell pellets derived from the ser-GNT labeled cells give bright T(1)-weighted MR images, confirming that the ser-GNTs are a promising new nanoprobe technology for magnetic cell labeling and possibly for in vivo cellular trafficking.

Magnetic resonance imaging studies on gadonanotube-reinforced biodegradable polymer nanocomposites.

We report about the in vitro cytotoxicity and MRI studies of Gd(3+)ions-doped ultra-short single-walled carbon nanotube (gadonanotubes), gadonanotubes- reinforced poly(lactic-co-glycolic acid) (PLGA) polymer nanocomposites and in vivo small animal MRI studies using the gadonanotubes. These studies were performed to explore the suitability of gadonanotubes-reinforced PLGA polymer nanocomposite as a model scaffold for noninvasive magnetic resonance imaging (MRI) to evaluate nanotube release during the degradation process of the scaffold and their biodistribution upon release from the polymer matrix in vivo. The gadonanotubes at 1-100 ppm and the gadonanotubes/PLGA nanocomposites (2 wt % gadonanotubes) did not show any cytotoxicity in vitro as demonstrated using the LIVE/DEAD viability assay. For the first time, r(2) relaxivity measurements were obtained for the superparamagnetic gadonanotubes. In vitro 7T MRI of the superparamagnetic gadonanotubes ([Gd] = 0.15 mM) suspended in a biocompatible 1% Pluronic F127 solution, gave a r(2) value of 578 mM(-1) s(-1). Upon subcutaneous injection of the gadonanotubes suspension into the dorsal region of rats, the high r(2) value translated into excellent and prolonged negative contrast enhancement of in vivo T(2)weighted proton MRI images. The in vitro characterization of the nanocomposite discs and their degradation process by MRI, showed strong influence of the gadonanotube on water proton relaxations. These results indicate that the gadonanotubes/PLGA nanocomposites are suitable for further in vivo studies to track by MRI the biodegradation release and biodistribution of gadonanotubes.

Catalytic synthesis of amino acid and peptide derivatized gadonanotubes.

A new Rh(6)(CO)(16)-catalyzed functionalization of gadonanotube MRI probes offers the opportunity to prepare a number of amino acid and peptide derivatized gadonanotubes under RT conditions, containing, for example, the cyclic RGD peptide for the biological targeting of cancer.