Time-gated luminescence bioimaging with new luminescent nanocolloids based on [Mo6I8(C2F5COO)6]2- metal atom clusters.

Bioimaging and cell labeling using red or near infrared phosphors emitting in the "therapeutic window" of biological tissues have recently become some of the most active research fields in modern medical diagnostics. However, because organic and inorganic autofluorophores are omnipresent in nature, very often the background signal from fluorochromes other than targeted probes has to be eliminated. This discrimination could be available using a time-gated luminescence microscopy (TGLM) technique associated with long lifetime phosphorescent nanocomposites. Here, we report new SiO2 nanostructured particle (50 nm in diameter) embedded luminescent nanosized [Mo6I8(C2F5COO)6]2- metal atom clusters (1 nm in diameter), successfully prepared by the microemulsion technique. This combination provides new physical insight and displays red emission in biological based solution under UV-Vis excitation with long lifetimes of around 17 and 84 µs. Moreover, the nanoparticles can be internalized by cancer cells after surface functionalization by transferrin protein and clearly imaged by TGLM under excitation at 365 nm. The nanocomposites have been mainly characterized by scanning and transmission electron microscopies (SEM and HAADF-STEM), UV-Vis and photoluminescence (PL) spectroscopies.

Inhalation of acidic nanoparticles prevents doxorubicin cardiotoxicity through improvement of lysosomal function.

Doxorubicin (Dox) is an effective anticancer molecule, but its clinical efficacy is limited by strong cardiotoxic side effects. Lysosomal dysfunction has recently been proposed as a new mechanism of Dox-induced cardiomyopathy. However, to date, there is a paucity of therapeutic approaches capable of restoring lysosomal acidification and function in the heart. Methods: We designed novel poly(lactic-co-glycolic acid) (PLGA)-grafted silica nanoparticles (NPs) and investigated their therapeutic potential in the primary prevention of Dox cardiotoxicity in cardiomyocytes and mice. Results: We showed that NPs-PLGA internalized rapidly in cardiomyocytes and accumulated inside the lysosomes. Mechanistically, NPs-PLGA restored lysosomal acidification in the presence of doxorubicin or bafilomycin A1, thereby improving lysosomal function and autophagic flux. Importantly, NPs-PLGA mitigated Dox-related mitochondrial dysfunction and oxidative stress, two main mechanisms of cardiotoxicity. In vivo, inhalation of NPs-PLGA led to effective and rapid targeting of the myocardium, which prevented Dox-induced adverse remodeling and cardiac dysfunction in mice. Conclusion: Our findings demonstrate a pivotal role for lysosomal dysfunction in Dox-induced cardiomyopathy and highlight for the first time that pulmonary-driven NPs-PLGA administration is a promising strategy against anthracycline cardiotoxicity.

APTES-modified RE2O3:Eu3+ luminescent beads: structure and properties.

Europium-doped lanthanide oxide RE(2)O(3):Eu(3+) (RE = Y or Gd) luminescent beads, with a spherical shape and a diameter of 150 ± 15 nm, have been modified by reaction with 3-aminopropyltriethoxysilane (APTES), in order to introduce reactive amine groups at their surfaces. The direct silanation has resulted in the formation of a nanometric layer at the surface of the beads, with an optimum grafting rate of 0.055 ± 0.005 mol APTES/mol RE(2)O(3). Fourier transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies confirmed the condensation of an organosilane layer, made of cross-linked -O-Si-O-Si- and of groups -O-Si-R (with R = (CH(2))(3)NH(2) or O-Et). Titration of the accessible amine groups has been performed by simultaneously measuring the luminescence of grafted fluorescein isothiocyanate and that of core particles: there are about 2.3 × 10(4) (2.8 × 10(4)) -NH(2) per Y(2)O(3):Eu(3+) (Gd(2)O(3):Eu(3+)) bead. The isoelectronic point was shifted by one pH unit after APTES modification. The surface modification by APTES at least preserved (for Gd(2)O(3):Eu(3+)) or improved (for Y(2)O(3):Eu(3+)) the red emission of the beads.

Multimodal gadolinium oxysulfide nanoparticles for bioimaging: A comprehensive biodistribution, elimination and toxicological study.

For some years now, gadolinium oxysulfide nanoparticles (NPs) appear as strong candidates for very efficient multimodal in vivo imaging by: 1) Magnetic Resonance (MRI), 2) X-ray Computed Tomography (CT) and 3) photoluminescence imaging. In this paper, we present a selection of results centered on the evaluation of physico-chemical stability, toxicity, bio-distribution and excretion mechanisms of Gd2O2S:Ln3+ nanoparticles intravenously injected in rats. Two formulations are here tested with a common matrix and different dopants: Gd2O2S:Eu3+5% and Gd2O2S:Yb3+4%/Tm3+0.1%. The NPs appear to be almost insoluble in pure water and human plasma but corrosion/degradation phenomenon appears in acidic conditions classically encountered in cell lysosomes. Whole body in vivo distribution, excretion and toxicity evaluation revealed a high tolerance of nanoparticles with a long-lasting imaging signal associated with a slow hepatobiliary clearance and very weak urinary excretion. The results show that the majority of the injected product (>60%) has been excreted through the feces after five months. Experiments have evidenced that the NPs mainly accumulate in macrophage-rich organs, that is mainly liver and spleen and to a lesser extent lungs and bones (mainly marrow). No significant amounts have been detected in other organs such as heart, kidneys, brain, intestine and skin. Gd2O2S:Ln3+ NPs appeared to be very well tolerated up to 400 mg/kg when administered intravenously. STATEMENT OF SIGNIFICANCE: Since 2011, we have focused our work on Gd2O2S nanoparticles (NPs) for multimodal bioimaging using fluorescence, Magnetic Resonance Imaging (MRI) and Computed Tomography with very efficient results already published. However, since the European Medicines Agency has concluded its review of gadolinium contrast agents, confirming recommendations to restrict the use of some linear gadolinium agents used in MRI, a particular attention must be paid to any new contrast media containing gadolinium. Therefore, we present in this paper a compilation of studies about toxicity, bio-distribution and excretion mechanisms of Gd2O2S:Ln3+ NPs intravenously injected into rats. We also present an in vitro kinetic study of NPs degradation in aqueous and biological media to provide some information on chemical and biological stability.

Increasing Uptake of Silica Nanoparticles with Electroporation: From Cellular Characterization to Potential Applications.

In the fields of biology and medicine, nanoproducts such as nanoparticles (NPs) are specifically interesting as theranostic tools, since they offer the double capacity to locally deliver active drugs and to image exactly where the product is delivered. Among the many described possibilities, silica nanoparticles (SiNPs) represent a good choice because of their ease of synthesis, the possibility of their vast functionalization, and their good biocompatibility. However, SiNPs' passive cell internalization by endocytosis only distributes NPs into the cell cytoplasm and is unable to target the nucleus if SiNPs are larger than a few nanometers. In this study, we demonstrate that the cell penetration of SiNPs of 28⁻30 nm in diameter can be strongly enhanced using a physical method, called electroporation or electropermeabilization (EP). The uptake of fluorescently labelled silica nanoparticles was improved in two different cancer cell lines, namely, HCT-116 (human colon cancer) cells and RL (B-lymphoma) cells. First, we studied cells' capability for the regular passive uptake of SiNPs in vitro. Then, we set EP parameters in order to induce a more efficient and rapid cell loading, also comprising the nuclear compartment, while preserving the cell viability. In the final approach, we performed in vivo experiments, and evidenced that the labeling was long-lasting, as confirmed by fluorescence imaging of labeled tumors, which enabled a 30-day follow-up. This kind of SiNPs delivery, achieved by EP, could be employed to load extensive amounts of active ingredients into the cell nucleus, and concomitantly allow the monitoring of the long-term fate of nanoparticles.

Multimodal gadolinium oxysulfide nanoparticles: a versatile contrast agent for mesenchymal stem cell labeling.

Despite a clear development of innovative therapies based on stem cell manipulation, the availability of new tools to better understand and follow stem cell behavior and improve their biomedical applications is not adequate. Indeed, an ideal tracking device must have good ability to label stem cells as well as complete neutrality relative to their biology. Furthermore, preclinical studies imply in vitro and in vivo approaches that often require several kinds of labeling and/or detection procedures. Consequently, the multimodality concept presented in this work may present a solution to this problem as it has the potential to combine complementary imaging techniques. Spherical europium-doped gadolinium oxysulfide (Gd2O2S:Eu3+) nanoparticles are presented as a candidate as they are detectable by (1) magnetic resonance (MRI), (2) X-ray and (3) photoluminescence imaging. Whole body in vivo distribution, elimination and toxicity evaluation revealed a high tolerance of nanoparticles with a long-lasting MRI signal and slow hepatobiliary and renal clearance. In vitro labeling of a wide variety of cells unveils the nanoparticle potential for efficient and universal cell tracking. Emphasis on mesenchymal stromal cells (MSCs) leads to the definition of optimal conditions for labeling and tracking in the context of cell therapy: concentrations below 50 µg mL-1 and diameters between 170 and 300 nm. Viability, proliferation, migration and differentiation towards mesodermal lineages are preserved under these conditions, and cell labeling appears to be persistent and without any leakage. Ex vivo detection of as few as five thousand Gd2O2S:Eu3+-labeled MSCs by MRI combined with in vitro examination with fluorescence microscopy highlights the feasibility of cell tracking in cell therapy using this new nanoplatform.

Silica-Based Nanoparticles as Bifunctional and Bimodal Imaging Contrast Agents.

New bifunctional and bimodal nanoparticles (NPs) have been elaborated and characterised. They are based on silica NPs that incorporate a silylated ruthenium tris-bipyridine complex. The resulting suspension of amine-modified NPs with diameters of 20 nm was post-functionalised with a stable gadolinium ion complex. Interest in these NPs lies mainly in the confinement of optical and magnetic imaging agents (Ru and Gd complexes, respectively) within the NP volume. Their potential use as a bimodal probe (luminescence/magnetic resonance imaging) and theranostic agent (photodynamic therapy/imaging) is described. The biological potential of these NPs has been studied on HCT-116 cells and microscopy and cytotoxicity results are given.

Practical implementation, characterization and applications of a multi-colour time-gated luminescence microscope.

Time-gated luminescence microscopy using long-lifetime molecular probes can effectively eliminate autofluorescence to enable high contrast imaging. Here we investigate a new strategy of time-gated imaging for simultaneous visualisation of multiple species of microorganisms stained with long-lived complexes under low-background conditions. This is realized by imaging two pathogenic organisms (Giardia lamblia stained with a red europium probe and Cryptosporidium parvum with a green terbium probe) at UV wavelengths (320-400 nm) through synchronization of a flash lamp with high repetition rate (1 kHz) to a robust time-gating detection unit. This approach provides four times enhancement in signal-to-background ratio over non-time-gated imaging, while the average signal intensity also increases six-fold compared with that under UV LED excitation. The high sensitivity is further confirmed by imaging the single europium-doped Y2O2S nanocrystals (150 nm). We report technical details regarding the time-gating detection unit and demonstrate its compatibility with commercial epi-fluorescence microscopes, providing a valuable and convenient addition to standard laboratory equipment.

Gadolinium oxysulfide nanoparticles as multimodal imaging agents for T2-weighted MR, X-ray tomography and photoluminescence.

We have synthesized gadolinium oxysulfide nanoparticles (NPs) doped with other lanthanides (Eu(3+), Er(3+), Yb(3+)) via a hydroxycarbonate precursor precipitation route followed by a sulfuration process under a H2S-Ar atmosphere at 750 °C in order to propose new multimodal nanoplatforms for Magnetic Resonance (MR), X-ray and photoluminescence imaging. Gd2O2S:Eu(3+) NPs strongly absorb near UV (≈ 300-400 nm) and re-emit strong red light (624 nm). They can be easily internalized by cancer cells, and imaged by epifluorescence microscopy under excitation in the NUV (365 nm). They are not cytotoxic for living cells up to 100 µg mL(-1). Consequently, they are well adapted for in vitro imaging on cell cultures. Gd2O2S:Eu(3+) NPs also show strong transverse relaxivity and strong X-ray absorption allowing their use as contrast agents for T2-weighted MRI and X-ray tomography. Our study shows that Gd2O2S:Eu(3+) NPs are considerably better than commercial Ferumoxtran-10 NPs as negative contrast agents for MRI. Upconversion emission of Gd2O2S:Er; Yb (1; 8%) NPs under infrared excitation (λ(ex) = 980 nm) shows mainly red emission (≈ 650-680 nm). Consequently, they are more specifically designed for in vivo deep fluorescence imaging, because both excitation and emission are located inside the "transparency window" of biological tissues (650-1200 nm). Magnetic relaxivity and X-ray absorption behaviors of Gd2O2S:Er; Yb NPs are almost similar to Gd2O2S:Eu(3+) NPs.

Alteration of enzyme activity and enantioselectivity by biomimetic encapsulation in silica particles.

Direct encapsulation of esterase or lipase fused with the silica-precipitating R5 peptide from Cylindrotheca fusiformis in silica particles afforded high yields of active entrapped protein. The hydrolytic activity of both enzymes against p-nitrophenyl butyrate was similarly affected by encapsulation and the enantioselectivity of the esterase was both improved and inverted.