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Chitosan ultrapure silicon nanoparticles produced by femtosecond laser ablation exhibited an ideal biodistribution profile within tumor microenvironment promising their application in the nano-oncology field as tumor targeting system.

International audience; Owing to strong plasmonic absorption and excellent biocompatibility, gold nanostructures are among best candidates for photoacoustic bioimaging and photothermal therapy, but such applications require ultrapure Au-based nanoformulations of complex geometry (core-shells, nanorods) in order to shift the absorption band toward the region of relative tissue transparency (650–1000 nm). Here, we present a methodology for the fabrication of Si@Au core-satellite nanostructures, comprising of a Si core covered with small Au nanoparticles (NP), based on laser ablative synthesis of Si and Au NPs in water/ethanol solutions, followed by a chemical modification of the Si NPs by 3-aminopropyltrimethoxysilane (APTMS) and their subsequent decoration by the Au NPs. We show that the formed core-satellites have a red-shifted plasmonic absorption feature compared to that of pure Au NPs (520 nm), with the position of the peak depending on APTMS amount, water−ethanol solvent percentage and Si−Au volume ratio. As an example, even relatively small 40-nm core-satellites (34 nm Si core + 4 nm Au shell) provided a much red shifted peak centered around 610 nm and having a large tail over 700 nm. The generation of the plasmonic peak is confirmed by modeling of Si@Au core-shells of relevant parameters via Mie theory. Being relatively small and exempt of any toxic impurity due to ultraclean laser synthesis, the Si@Au core-satellites promise a major advancement of imaging and phototherapy modalities based on plasmonic properties of nanomaterials.

International audience; Driven by flexibility, precision, repeatability and eco-friendliness, laser-based technologies have attracted great interest to engineer or to analyze materials in various fields including energy, environment, biology and medicine. A major advantage of laser processing relies on the ability to directly structure matter at different scales and to prepare novel materials with unique physical and chemical properties. It is also a contact-free approach that makes it possible to work in inert or reactive liquid or gaseous environment. This leads today to a unique opportunity for designing, fabricating and even analyzing novel complex bio-systems. To illustrate this potential, in this paper, we gather our recent research on four types of laser-based methods relevant for nano-/micro-scale applications. First, we present and discuss pulsed laser ablation in liquid, exploited today for synthetizing ultraclean “bare” nanoparticles attractive for medicine and tissue engineering applications. Second, we discuss robust methods for rapid surface and bulk machining (subtractive manufacturing) at different scales by laser ablation. Among them, the microsphere-assisted laser surface engineering is detailed for its appropriateness to design structured substrates with hierarchically periodic patterns at nano-/micro-scale without chemical treatments. Third, we address the laser-induced forward transfer, a technology based on direct laser printing, to transfer and assemble a multitude of materials (additive structuring), including biological moiety without alteration of functionality. Finally, the fourth method is about chemical analysis: we present the potential of laser-induced breakdown spectroscopy, providing a unique tool for contact-free and space-resolved elemental analysis of organic materials. Overall, we present and discuss the prospect and complementarity of emerging reliable laser technologies, to address challenges in materials’ preparation relevant for the development of innovative multi-scale and multi-material platforms for bio-applications.

Driven by their distinctive physiological activities, biological properties and unique theranostic modalities, silicon nanoparticles (SiNPs) are one of the promising materials for the development of novel multifunctional nanoplatforms for biomedical applications. In this work, we assessed the possibility to use laser-synthesized Si NPs as photosensitizers in two-photon excited photodynamic therapy (TPE-PDT) modality. Herein, we used an easy strategy to synthesize ultraclean and monodispersed SiNPs using laser ablation and fragmentation sequences of silicon wafer in aqueous solution, which prevent any specific purification step. Structural analysis revealed the spherical shape of the nanoparticles with a narrow size distribution centered at the mean size diameter of 62 nm &plusmn, 0.42 nm, while the negative surface charge of &minus, 40 &plusmn, 0.3 mV ensured a great stability without sedimentation over a long period of time. In vitro studies on human cancer cell lines (breast and liver) and healthy cells revealed their low cytotoxicity without any light stimulus and their therapeutic potential under TPE-PDT mode at 900 nm with a promising cell death of 45% in case of MCF-7 breast cancer cells, as a consequence of intracellular reactive oxygen species release. Their luminescence emission inside the cells was clearly observed at UV-Vis region. Compared to Si nanoparticles synthesized via chemical routes, which are often linked to additional modules with photochemical and photobiological properties to boost photodynamic effect, laser-synthesized SiNPs exhibit promising intrinsic therapeutic and imaging properties to develop advanced strategy in nanomedicine field.

We describe a laser-assisted methodology for the fabrication of Si@Au core-satellite nanostructures for photothermal therapy applications. The methodology consists in laser ablative synthesis of Si and Au NPs in water/ethanol solutions, followed by a chemical modification of the Si NPs by APTMS and their subsequent decoration by the Au NPs. We show that despite a relatively small size (< 40 nm) the formed core-satellites exhibit a strong plasmonic absorption peak centred around 610 nm and having a large tail over 700 nm overlapping with the first optical window of relative tissue transparency. Being relatively small and exempt of any toxic impurity due to ultraclean laser synthesis, the fabricated nanoparticles promise a major advancement of imaging and phototherapy modalities based on plasmonic properties of nanomatererials.

Capable of generating plasmonic and other effects, gold nanostructures can offer a variety of diagnostic and therapy functionalities for biomedical applications, but conventional chemically-synthesized Au nanomaterials cannot always match stringent requirements for toxicity levels and surface conditioning. Laser-synthesized Au nanoparticles (AuNP) present a viable alternative to chemical counterparts and can offer exceptional purity (no trace of contaminants) and unusual surface chemistry making possible direct conjugation with biocompatible polymers (dextran, polyethylene glycol). This work presents the first pharmacokinetics, biodistribution and safety study of laser-ablated dextran-coated AuNP (AuNPd) under intravenous administration in small animal model. Our data show that AuNPd are rapidly eliminated from the blood circulation and accumulated preferentially in liver and spleen, without inducing liver or kidney toxicity, as confirmed by the plasmatic ALAT and ASAT activities, and creatininemia values. Despite certain residual accumulation in tissues, we did not detect any sign of histological damage or inflammation in tissues, while IL-6 level confirmed the absence of any chronic inflammation. The safety of AuNPd was confirmed by healthy behavior of animals and the absence of acute and chronic toxicities in liver, spleen and kidneys. Our results demonstrate that laser-synthesized AuNP are safe for biological systems, which promises their successful biomedical applications.

We report a methodology for the fabrication of neutralized chitosan-based nanofiber matrices decorated with bare Au nanoparticles, which demonstrate stable characteristics even after prolonged contact with a biological environment. The methodology consists of electrospinning of a mixture of bare (ligand-free) laser-synthesized Au nanoparticles (AuNPs) and solutions of chitosan/polyethylene oxide (ratio 1/3) containing chitosan of a relatively high molecular weight (200 kDa) and concentration of 3% (w/v). Our studies reveal a continuous morphology of hybrid nanofibers with the mean fiber diameter of 189 nm &plusmn, 86 nm, which demonstrate a high thermal stability. Finally, we describe a protocol for the neutralization of nanofibers, which enabled us to achieve their structural stability in phosphate-buffered saline (PBS) for more than six months, as confirmed by microscopy and FTIR measurements. The formed hybrid nanofibers exhibit unique physicochemical properties essential for the development of future tissue engineering platforms.

International audience

International audience; In situ temperature monitoring with photoacoustic measurements is introduced in an integrated setup, specifically designed for photothermotherapy treatmentof the glioblastoma, aided by nanoparticles and HIFU blood-brain barrier opening.

In food industry, detection of spoilage yeasts such as W. anomalus and B. bruxellensis and pathogens such as certain Listeria and E. coli species can be laborious and time-consuming. In the present study, a simple and repeatable technique was developed for rapid yeast detection using a combination of patterned gold coated polymer SERS substrates and gold nanoparticles [1−4]. For the first time, a state-of-the-art time-gated Raman detection approach was used as a complementary technique to show the possibility of using 532-nm pulsed laser excitation and avoid the destructive influence of induced fluorescence [3]. Conventional nanoparticles synthesized by colloidal chemistry are typically contaminated by non-biocompatible by-products (surfactants, anions), which can have negative impacts on many live objects under examination (cells, bacteria) and thus decrease the precision of bioidentification. Here, we explore novel ultrapure laser-synthesized Au-based nanomaterials, including Au NPs and Au Si hybrid nanostructures, as mobile SERS probes in tasks of bacteria detection [3]. We demonstrate successful identification of two types of bacteria (L. innocua and E. coli) and yeast (W. anomalus and B. bruxellensis). They showed several differing characteristic peaks making the discrimination of these yeasts possible without the need for chemometric analysis [2]. The use of composite gold-silicon laser-ablated nanoparticles in combination with the SERS substrate gave distinctive spectra for all the detected species. The detection limit of the studied species varied within 104-107 CFU/ml. The obtained results open up opportunities for non-disturbing investigation of biological systems by profiting from excellent non-disturbing nature of laser-synthesized nanomaterials in combination with outstanding optical detection technologies [2, 3]. [1] Uusitalo et al. 2016, http://pubs.rsc.org/en/content/articlehtml/2016/ra/c6ra08313g [2] Uusitalo et al. 2017a, https://www.sciencedirect.com/science/article/pii/S0260877417302054 [3] Kogler et al. 2018, https://onlinelibrary.wiley.com/doi/abs/10.1002/jbio.201700225 [4] Uusitalo et al. 2017b, https://www.spiedigitallibrary.org/journalArticle/Download?fullDOI=10.1117/1.OE.56.3.037102

The presentation will overview our on-going activities on laser ablative synthesis of plasmonic colloidal nanomaterials and their biomedical applications. Our approach is based on ultra-short (fs) laser ablation from a solid target or already formed water-suspended colloids, which makes possible the fabrication of ultrapure bare (ligand-free) nanoparticles having controlled mean size and low size dispersion. The presentation will describe different approaches to achieve appropriate characteristics of nanomaterials (Au-based nanomaterials and alternative structures) and overview their biomedical applications. In particular, we show that Au nanoparticles can efficiently enhance Raman signals from different biological objects. Profiting from the observed enhancement and purity of laser-synthesized nanomaterials, we demonstrate successful identification of 2 types of bacteria (Listeria innocua and Escherichia coli). We also show that bare metal nanoparticles synthesized by laser ablation can provide an order of magnitude better response in glucose oxidation tasks, which promises their use as elecrocatalysts in bioimplantable therapeutic devices. Finally, we overview applications of bare plasmonic nanomaterials in phototherapy and tissue engineering tasks

Biomimetic nanocrystalline apatites are analogous to bone mineral. They can be exploited not only for bone regeneration applications, but it is also possible to take advantage of their biomimetic features to explore novel domains of research such as in nanomedicine, if the nanoparticles are stabilized as a colloidal formulation. In this contribution, we concentrate on AEP/HMP-stabilized colloidal apatite nanoparticles (NPs) and on their interaction with different types of cells so as to get experimental evidence on their low cytotoxicity, non-proinflammatory potential, and good compatibility with Red Blood Cells. We then started to explore their interaction with an artificial free-standing phospholipid bilayer, as a simplified model for cell membranes: results indicate, for the first time, that these colloidal apatite NPs can modulate phospholipid bilayer membrane properties, and may even favor the permeation of small molecules (illustrated here with luminescent FITC), which could ultimately be exploited for nanomedicine applications in view of enhancing intracellular drug delivery.

Hybrid nanofibers are emerging as one of the solutions to unite two modalities (organic and in-organic) widely found in nature, rarely engineered at small length scale; due to restrictions like wide array of physical, chemical properties, range of processing environments; these modalities feature seldom in applications. Hybrid nanofibers enables overcoming these restrictions by combining many dissimilar modalities thereby, incorporating functionalities of those dissimilar modalities into a single structure. Therefore, efficiently fabricating a multifunctional hybrid system with applications not limited by processing environments or range of properties. Additionally, multifunctionality, porosity, high surface to volume ratio provide hybrid nanofibers as an alternative for wide biomedical as well as other applications like filtration, tissue engineering among others. Electrospinning enables fabrication of nonwoven nanofibers ranging from few hundred nanometers to microns. Functional modalities like nanoparticles, dendrimers, proteins could be fabricated in polymer matrix. One such process being used here employs Poly (ethylene oxide), chitosan as matrix with gold nanoparticles as functional elements. The gold nanoparticles have been synthesized by laser ablation and by Turkevich's method [1]. With continuation to previous study the fibers have been prepared and analyzed with higher concentration of chitosan and then electrospun to produce nanofibers averaging 300 nm. With potential such as high contrast for biological imaging, induced hyperthermia and drug loading modalities. The fibers were then characterized to distinguish them from pristine fibers. Various techniques used includes TGA, DSC, FTIR.

International audience; The ability of noble metal-based nanoparti-cles (NPs) (Au, Ag) to drastically enhance Raman scattering from molecules placed near metal surface, termed as surface-enhanced Raman scattering (SERS), is widely used for identification of trace amounts of biological materials in biomedical, food safety and security applications. However, conventional NPs synthesized by colloi-dal chemistry are typically contaminated by nonbiocompatible by-products (surfac-tants, anions), which can have negative impacts on many live objects under examination (cells, bacteria) and thus decrease the precision of bioidentification. In this article, we explore novel ultrapure laser-synthesized Au-based nanomaterials, including Au NPs and AuSi hybrid nanostructures, as mobile SERS probes in tasks of bacteria detection. We show that these Au-based nanomaterials can efficiently enhance Raman signals from model R6G molecules, while the enhancement factor depends on the content of Au in NP composition. Profiting from the observed enhancement and purity of laser-synthesized nanomaterials, we demonstrate successful identification of 2 types of bacteria (Listeria innocua and Escherichia coli). The obtained results promise less disturbing studies of biological systems based on good biocompatibility of contamination-free laser-synthesized nanomaterials. K E Y W O R D S bacteria detection, laser ablation in liquids, Raman spectroscopy, SERS, ultrapure laser-synthesized Au nanoparticles Martin Kögler and Yury V. Ryabchikov contributed equally to this study.

International audience; Driven by surface cleanness and unique physical, optical and chemical properties, bare (ligand-free) laser-synthesized nanoparticles (NPs) are now in the focus of interest as promising materials for the development of advanced biomedical platforms related to biosensing, bioimaging and therapeutic drug delivery. We recently achieved significant progress in the synthesis of bare gold (Au) and silicon (Si) NPs and their testing in biomedical tasks, including cancer imaging and therapy, biofuel cells, etc. We also showed that these nanomaterials can be excellent candidates for tissue engineering applications. This review is aimed at the description of our recent progress in laser synthesis of bare Si and Au NPs and their testing as functional modules (additives) in innovative scaffold platforms intended for tissue engineering tasks.

Methods of femtosecond laser ablation were used to fabricate bare (ligand-free) silicon (Si) nanoparticles in deionized water. The nanoparticles were round in shape, crystalline, free of any impurities, and water-dissolvable, while the dissolution rate depended on the concentration of oxygen defects in their composition. The nanoparticles were then eletrospun with chitosan to form nanoparticle decorated nanofibrous matrices. We found that the functionalization of nanofibers by the nanoparticles can affect the morphology and physico-chemical characteristics of resulting nanostructures. In particular, the presence of Si nanoparticles led to the reduction of fibers thickness, suggesting a potential improvement of fiber’s surface reactivity. We also observed the improvement of thermal stability of hybrid nanofibers. We believe that the incorporated Si nanoparticles can serve as functional elements to improve characteristics of chitosan-based matrices for cellular growth, as well as to enable novel imaging or therapeutic functionalities for tissue engineering applications.

In order to assess the possible risks of applications containing engineered nanomaterials, it is essential to generate more data about their release and exposure, so far largely overlooked areas of research. The aim of this work was to study the characterization of the materials released from paint containing nano-SiO2 during weathering and exposure to water. Panels coated with nano-SiO2 containing paint and a nano-free reference paint were exposed to accelerated weathering cycles in a climate chamber. The total release of 89 six-hour cycles of UV-illumination and precipitation was 2.3% of the total SiO2 contained in the paint. Additional tests with powdered and aged paint showed that the majority of the released Si was present in dissolved form and that only a small percentage was present in particulate and nano-particulate form. TEM imaging of the leachates indicated that the majority of the particulate Si was contained in composites together with Ca, representing the paint matrix, and only few single dispersed SiO2-NPs were detected. The results suggest that toxicological and ecotoxicological studies need to consider that the released particles may have been transformed or are embedded in a matrix.

Femtosecond laser fragmentation from preliminarily prepared water-dispersed Si microcolloids was used to synthesize bare (ligand-free) spherical silicon nanoparticles (Si-NPs) with low size dispersion and controllable mean size from a few nm to several tens of nm. In order to control the oxidation state of Si-NPs, the fragmentation was performed in normal oxygen-saturated water (oxygen-rich conditions) or in water disoxygenated by pumping with noble gases (Ag, He) before and during the experiment (oxygen-free conditions). XPS and TEM studies revealed that Si-NPs were composed of Si nanocrystals with inclusions of silicon oxide species, covered by SiOx (1 < x < 2) shell, while the total oxide content depended whether Si-NPs were prepared in oxygen-rich or oxygen-free conditions. When placed into a dialysis box, waterdispersed Si-NPs rapidly dissolved, which was evidenced by TEM data. In this case, NPs prepared under oxygen-rich conditions demonstrated much faster dissolution kinetics and their complete disappearance after 7-10 days, while the dissolution process of less oxidized counterparts could last much longer (25-30 days). Much fast dissolution kinetics of more oxidized Si-NPs was attributed to more friable structure of nanoparticle core due to the presence of numerous oxidation-induced defects. Laser-synthesized Si-NPs are of paramount importance for biomedical applications.

In the assessment of the fate and effects of engineered nanomaterials (ENM), the current focus is on studying the pristine, unaltered materials. However, ENM are incorporated into products and are released over the whole product life cycle, though mainly during the use and disposal phases. So far, released ENMs have only been characterized to a limited extent and almost nothing is known about the behavior of these materials under natural conditions. In this work we obtained material that was released from aged paint containing nano-TiO2, characterized the particulate materials, and studied their colloidal stability in media with different pH and ionic composition. A stable suspension was obtained from aged paint powder by gentle shaking in water, producing a dilute suspension of 580 μg/L TiO2 with an average particle size of 200-300 nm. Most particles in this suspension were small pieces of paint matrix that also contained nano-TiO2. Some free nano-TiO2 particles were observed by electron microscopy, but the majority was enclosed by the organic paint binder. The pristine nano-TiO2 showed the expected colloidal behavior with increasing stability with increasing pH and strong agglomeration above the isoelectric point and settling in the presence of Ca. The released TiO2 showed very small variations in particle size, ζ potential, and colloidal stability, even in the presence of 3 mM Ca. The results show that the behavior of released ENM may not necessarily be predicted by studying the pristine materials. Additionally, effect studies need to focus more on the particles that are actually released as we can expect that the toxic effect will also be markedly different between pristine and product released materials.

The setup of colloidal hybrid nanosystems based on biomimetic calcium phosphate apatites doped with europium ions has recently raised great interest in the pharmacological community, especially due to their bio-inspired character. This is especially relevant in relation with medical imaging for cancer diagnosis. Questions however remain in relation to a number of applicability aspects, some of which have been examined in this contribution. In a first part of this work, we explored further the luminescence properties of such colloidal nanoparticles. We pointed out, upon excitation of europium, the existence of some non-radiative de-excitation via the vibration of O-H oscillators located at the vicinity of the Eu3+ luminescent centers. The replacement of Eu3+ by Tb3+ ions, less prone to non-radiative de-excitation, was then tested in a preliminary way and can be seen as a promising alternative. In a second part of this work, we inspected the possibility to store these colloids in a dry state while retaining a re-suspension ability preserving the nanometer size of the initial nanoparticles, and we propose a functional protocol involving the addition of glucose prior to freeze-drying. We finally showed for the first time, based on titrations of intracellular Ca2+ and Eu3+ ions, that folic acid-functionalized biomimetic apatite nanoparticles were able to target cancer cells that overexpress folate receptors on their membrane, which we point out here in the case of T-47-D breast carcinoma cells, as opposed to ZR-75-1 cells that do not express folate receptors. This contribution thus opens new exciting perspectives in the field of targeted cancer diagnosis, thus confirming the promise of biomimetic apatites-based colloidal formulations.

International audience; Continuous wave (CW) radiation from a Yb-fiber laser (central wavelength 1064 nm, power 1–200 W) was used to initiate ablation of a gold target in deionized water and to synthesize bare (unprotected) gold nanoparticles. We show that the formed nanoparticles present a single low-size-dispersed population with a mean size of the order of 10 nm, which contrasts with previously reported data on dual populations of nanoparticles formed during pulsed laser ablation in liquids. The lack of a second population of nanoparticles is explained by the absence of cavitation-related mechanism of material ablation, which typically takes place under pulsed laser action on a solid target in liquid ambience, and this supposition is confirmed by plume visualization tests. We also observe a gradual growth of mean nanoparticle size from 8–10 nm to 20–25 nm under the increase of laser power for 532 nm pumping wavelength, whereas for 1064 nm pumping wavelength the mean size 8–10 nm is independent of radiation power. The growth of the nanoparticles observed for 532 nm wavelength is attributed to the enhanced target melting and splashing followed by additional heating due to an efficient excitation of plasmons over gold nanoparticles. Bare, low-size-dispersed gold nanoparticles are of importance for a variety of applications, including biomedicine, catalysis, and photovoltaics. The use of CW radiation for nanomaterial production promises to improve the cost efficiency of this technology.

International audience; Gold nanoparticles (Au NPs) attract particular attention because of their unique size-dependent chemical, physicochemical and optical properties and, hence, their potential applications in catalysis, nanoelectronics, photovoltaics and medicine. In particular, laser-produced colloidal nanoparticles are not only biocompatible, but also reveal unique chemical properties. Different laser systems can be used for synthesis of these colloids, varying from continuous wave (CW) to ultra-short femtosecond lasers. The choice of an optimum laser system is still a challenge in application development. To bring more light at this issue, we investigate an influence of laser parameters on nanoparticle formation from a gold target immersed in deionized water. First, an optical diagnostics of laser-induced hydrodynamic processes taking place near the gold surface is performed. Then, gold nanoparticle colloids with average particle sizes smaller than 10 nm and a very narrow dispersion are shown to be formed by CW laser ablation. The obtained results are compared with the ones obtained by using the second harmonics and with previous results obtained by using femtosecond laser systems. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Intracellular drug delivery using colloidal biomimetic calcium phosphate apatites as nanocarriers is a seducing concept. However, the colloid preparation to an industrial scale requires the use of easily handled raw materials as well as the possibility to tailor the nanoparticles size. In this work, the stabilization of the colloids was investigated with various biocompatible agents. Most interestingly, nanoscale colloids were obtained without the need for toxic and/or hazardous raw materials. Physico-chemical characteristics were investigated by chemical analyses, dynamic light scattering, FTIR/Raman spectroscopies, XRD, and electron microscopy. A particularly promising colloidal system associates biomimetic apatite stabilized with a natural phospholipid moiety (AEP(r), 2-aminoethylphosphoric acid). Complementary data described such colloids as apatite nanocrystals covered with surface Ca(2+)(AEP(r)(-))(2) complexes involving "supernumerary" Ca(2+) ions. The effects of the concentration in AEPr, synthesis temperature, duration of aging in solution, pH, and sonication were followed, showing that it is possible to modulate the mean size of the nanoparticles, typically in the range 30-100 nm. The perfect biocompatibility of such colloids allied to the possibility to prepare them from innocuous compounds shows great promise for intracellular drug delivery.

Si/SiOx nanoparticles (NPs) produced by laser ablation in deionized water or aqueous biocompatible solutions present a novel extremely promising object for biomedical applications, but the interaction of these NPs with biological systems has not yet been systematically examined. Here, we present the first comprehensive study of biodistribution, biodegradability and toxicity of laser-synthesized Si-SiOx nanoparticles using a small animal model. Despite a relatively high dose of Si-NPs (20 mg/kg) administered intravenously in mice, all controlled parameters (serum, enzymatic, histological etc.) were found to be within safe limits 3 h, 24 h, 48 h and 7 days after the administration. We also determined that the nanoparticles are rapidly sequestered by the liver and spleen, then further biodegraded and directly eliminated in urine without any toxicity effects. Finally, we found that intracellular accumulation of Si-NPs does not induce any oxidative stress damage. Our results evidence a huge potential in using these safe and biodegradable NPs in biomedical applications, in particular as vectors, contrast agents and sensitizers in cancer therapy and diagnostics (theranostics).

Conference on Synthesis and Photonics of Nanoscale Materials XIII, San Francisco, CA, FEB 15-17, 2016; International audience; We review our recently obtained data on the employment of Si nanoparticles as sensitizers of radiofrequency (RF) induced hyperthermia for mild cancer therapy tasks. Such an approach makes possible the heating of aqueous suspensions of Si nanoparticles by tens of degrees Celsius under relatively low intensities (1-5 W/cm2) of 27 MHz RF radiation. The heating effect is demonstrated for nanoparticles synthesized by laser ablation in water and mechanical grinding of porous silicon, while laser-ablated nanoparticles demonstrate a remarkably higher heating rate than porous silicon-based ones for the whole range of the used concentrations. The observed RF heating effect can be explained in the frame of a model considering the polarization of Si NPs and electrolyte in the external oscillating electromagnetic field and the corresponding release of heat by electric currents around the nanoparticles. Our tests evidence relative safety of Si nanostructures and their efficient dissolution in physiological solutions, suggesting potential clearance of nanoparticles from a living organism without any side effects. Profiting from Si nanoparticle-based heating, we finally demonstrate an efficient treatment of Lewis Lung carcinoma in vivo. The obtained data promise a breakthrough in the development of mild, non-invasive methods for cancer therapy.

We employ a method of femtosecond laser fragmentation of preliminarily prepared water-dispersed microcolloids to fabricate aqueous solutions of ultrapure bare Si-based nanoparticles (Si-NPs) and assess their potential for biomedical applications. The nanoparticles appear spherical in shape, with low size dispersion and a controllable mean size, from a few nm to several tens of nm, while a negative surface charge (−35 mV ± 0.10 according to z-potential data) provides good electrostatic stabilization of colloidal Si-NP solutions. Structural analysis shows that the Si-NPs are composed of Si nanocrystals with inclusions of silicon oxide species, covered by a SiOx (1 < x < 2) shell, while the total oxide content depends on whether the fragmentation is performed in normal oxygen-saturated water (oxygen-rich conditions) or in water deoxygenated by pumping with noble gases (Ag or He) before and during the experiment (oxygen-free conditions). Our dissolution tests show the excellent water-solubility of all the NPs, while more oxidized NPs demonstrate much faster dissolution kinetics, which is explained by oxidation-induced defects in the core of the Si-NPs. Finally, by examining the interaction of the NPs with human cells after 72 h of incubation at different concentrations, we report the absence of any adverse effects of the NPs up to high concentrations (50 μg mL−1) and a good internalization of NPs via a classical endocytosis mechanism. Possessing far superior purity compared to their chemically synthesized counterparts and enabling a variety of imaging and therapeutic functionalities, the laser-synthesized Si-NPs are promising for safe and efficient applications in nanomedicine.

International audience; Biomimetic calcium phosphate apatites, analogous to bone mineral, may now be produced synthetically. Their intrinsic biocompatibility and the nanometer dimensions of their constitutive crystals not only allow one to envision applications in bone tissue regeneration, but also in other medical fields such as nanomedicine, and in particular in view of cell diagnosis. In this mini-review, we look back at 10 years of our dedicated research, and summarize the main advances made in terms of preparation, physical-chemical characterizations and biological evaluations of colloidal formulations of biomimetic apatite-based nanoparticles, which we illustrate here with the angle of cancer diagnosis. The confirmed exceptional biocompatibility of these engineered nanoparticles, associated to the possibility to confer them luminescence properties by way of controlled lanthanide doping, and their capacity to be internalized by cells, including with cancer cell addressing abilities (shown here as a proof of concept), underline that biomimetic apatite-based colloidal nanoparticles are particularly promising for nanomedicine applications, for example related to diseased cells diagnosis. Multidisciplinary research on these functional nanoparticles, initiated as described here, has now generated emulation in the scientific community where the concept of apatite nanoparticles for nanomedicine is being, gratifyingly, appropriated.

International audience; Nanobiotechnologies have lately attracted much attention, both from therapeutic and diagnosis perspectives. In this view, the development of colloidal formulations of biocompatible nanoparticles capable of interacting with selected cells or tissues raises a particular interest, especially in linkwith cell-based pathologies such as cancer. In this context, the follow-up of colloidal stability and other physico-chemical features is of foremost relevance. In this contribution, we have focused our study on hybrid colloids based on biomimetic nanocrystalline apatites (analogous to those found in bone mineral) stabilized by adsorption of 2 aminoethylphosphate (AEP) molecules; these nanoparticles being intended to interact with cancer cells either for medical imaging (by conferring luminescence features to the apatite phase) or for therapeutic purposes. We show that various physico-chemical characteristics of the suspensions vary with time, including viscosity and mean particle size, suggesting a progressive structuration of the suspensions. Similar modifications were also noticed during the purification by dialysis. Finally,we report on preliminary experiments aimed at drying the colloids while retaining their capacity to recover their initial state after re-immersion in aqueous medium; so as to enable extended storage periods for the nanoparticles in their dry state while allowing their re-suspension at the time of use. On this matter, the addition of glucose prior to freeze-drying was found to be an effective way to avoid the formation of aggregates during drying. This contribution thus confers additional information relative to the stability of AEP-stabilized biomimetic.

International audience; Lanthanides “Ln” (rare earths) are critical elements found in natural minerals such as calcium phosphate apatites, in sedimentary and igneous settings as well as in skeletal diagenesis. From a medical point of view, nanoparticles of lanthanide-doped apatites can be produced for conferring luminescence properties of interest in cancer cells detection. However, the impact of the substitution of Ln for Ca on the stability and solubility of related apatite phases is still essentially unknown. To investigate the thermochemical effects of such lanthanide substitution for calcium in apatite, we prepared and analyzed four series of apatites with up to 10% lanthanide substitution for calcium. After thorough physicochemical characterization via complementary techniques (XRD, FTIR, TG/DSC, and IPC-AES), high-temperature oxide melt solution calorimetry in molten sodium molybdate at 973 K was performed to determine their enthalpies of formation from constituent oxides and from the elements, at 298 K. Our results indicate that although enthalpies of formation are strongly exothermic in all cases, Ln-doping has a destabilizing effect, which increases with dopant concentration and with the size of the incorporated Ln3+ ion. After estimating standard entropies, Gibbs free energies of formation and equilibrium constants for Ca2+/Ln3+ exchange reactions in apatite were then evaluated, for the first time allowing access to quantitative thermodynamic data that may be used in various fields for stability calculations or partitioning estimates between fluids and solids.

International audience; Nanocrystalline calcium phosphate apatites constitute the mineral part of hard tissues, and the synthesis of biomimetic analogs is now wellmastered at the labscale. Recent advances in the fine physicochemical characterization of these phases enable one to envision original applications in the medical field along with a better understanding of the underlying chemistry and related pharmacological features. In this contribution, we specifically focused on applications of biomimetic apatites in the field of cancer diagnosis or treatment. We first report on the production and first biological evaluations (cytotoxicity, proinflammatory potential, internalization by ZR751 breast cancer cells) of individualized luminescent nanoparticles based on Eudoped apatites, eventually associated with folic acid, for medical imaging purposes. We then detail, in a first approach, the preparation of tridimensional constructs associating nanocrystalline apatite aqueous gels and drugloaded pectin microspheres. Sustained releases of a fluorescein analog (erythrosin) used as model molecule were obtained over 7 days, in comparison with the ceramic or microsphere reference compounds. Such systems could constitute original bonefilling materials for in situ delivery of anticancer drugs.

The analysis of engineered nanomaterials (ENMs), especially engineered nanoparticles (ENPs), is a fast growing analytical research field. New trends in plasma spectrometry such as direct single particle inductively coupled plasma mass spectrometry (spICPMS) or the coupling of asymmetric flow field flow fractionation to ICPMS (A4F-ICPMS) allow direct analysis of ENPs by getting not only chemical but also size information simultaneously. However, sample handling of nanoparticles could be challenging and change the ENP properties. For most of the analysing techniques, dilution of ENP samples is needed as minimum sample preparation. The colloidal stability and the agglomeration behaviour depend on the ENP-type, the coating or functionalization agent and on the surrounding media. The stability of charge stabilized ENPs is especially sensitive to changes of pH or ionic strength, and sometimes even to dilution. Although the stability of sterically stabilized ENPs is typically less affected by the above-mentioned factors, agglomeration can still occur in certain environments. Thus, storage, handling and sample preparation are big challenges in ENP analysis. Kinetic studies of different ENPs, representative of typical nanoparticle types and coatings, point out that the behaviour is dependent on various influencing factors pertaining to the chemical environment (pH, ionic strength, dilution). In this study polyvinyl alcohol (Ag@PVA) and citrate (Ag@citrate) stabilized silver nanoparticles, as well as titanium oxide ENPs functionalized with poly-acrylate (TiO2@PA) have been studied. A simple analytical approach using batch dynamic light scattering (DLS) is proposed for a fast assessment of samples containing unknown ENP types or structures. Besides aspects of sample handling, unwanted particle–membrane interactions, which often lead to inappropriate recovery rates in A4F fractionation, are investigated here. These interactions are caused by the electrostatic charges carried by different membrane materials and the resulting interaction with the ENPs' charge. This is critically discussed for membrane materials typical for A4F analysis: polyethersulfone (PES), regenerated cellulose (RC), and polyvinylidene difluoride (PVDF).

The field of nanobiotechnology has lately attracted much attention both from therapeutic and diagnosis viewpoints. Of particular relevance is the development of colloidal formulations of biocompatible nanoparticles capable of interacting with selected cells or tissues. In this context, the purification of such nanoparticle suspensions appears as a critical step as residues of unreacted species may jeopardize biological and medical outcomes, and sample purity is thus increasingly taken into account by regulatory committees. In the present work, we have investigated from a physico-chemical point of view the purification by dialysis of recently developed hybrid colloids based on biomimetic nanocrystalline apatites intended for interacting with cells. Both Eu-doped (2 mol.% relative to Ca) and Eu-free suspensions were studied. The follow-up of the dialysis process was carried out by way of FTIR, TEM, XRD, pH and conductivity measurements. Mathematical modelling of conductivity data was reported. The effects of a change in temperature (25 and 45 °C), dialysis medium, and starting colloid composition were evaluated and discussed. We show that the dialysis method is a well-adapted and cheap technique to purify such mineral–organic hybrid suspensions in view of biomedical applications, and we point out some of the characterization techniques that may prove helpful for following the evolution of the purification process with time.

International audience; Biomimetic calcium phosphate apatites are particularly adapted to bio-medical applications due to their biocompatibility and high surface reactivity. In this contribution we report three selected examples dealing with mineral/organic interactions devoted to convey new functionalities to apatite materials, either in the form of dry bioceramics or of aqueous colloids. We first studied the adsorption of risedronate (bisphosphonate) molecules, which present potential therapeutic properties for the treatment of osteoporosis. We then addressed the preparation of luminescent Eu-doped apatites for exploring apatite/collagen interfaces through the FRET technique, in view of preparing "advanced" biocomposites exhibiting close spatial interaction between apatite crystals and collagen fibers. Finally, we showed the possibility to obtain nanometer-scaled apatite-based colloids, with particle size tailorable in the range 30-100 nm by controlling the agglomeration state of apatite nanocrystals by way of surface functionalization with a phospholipid moiety. This paper is aimed at illustrating some of the numerous potentialities of calcium phosphate apatites in the bio-medical field, allowing one to foresee perspectives lying well beyond bone-related applications.

International audience; Luminescent colloidal nanosystems based on europium-doped biomimetic apatite were prepared and investigated. The colloids were synthesized by soft chemistry in the presence of a phospholipid moiety, 2-aminoethylphosphoric acid (AEP), with varying europium doping rates. Physicochemical features, including compositional, structural, morphological, and luminescence properties, were examined. Experimental evidence showed that suspensions prepared from an initial Eu/(Eu+Ca) molar ratio up to 2% consisted of single-phased biomimetic apatite nanocrystals covered with AEP molecules. The mean particle size was found to depend closely on the AEP content, enabling the production of apatite colloids with a controlled size down to ca. 30 nm. The colloids showed luminescence properties typical of europium-doped systems with narrow emission bands and long luminescence lifetimes of the order to the millisecond, and the data suggested the location of Eu3+ ions in a common crystallographic environment for all the colloids. These systems, stable over time and capable of being excited in close-to-visible or visible light domains, may raise interest in the future in the field of medical imaging.

The release of nanomaterials from products and applications that are used by industry and consumers has only been studied to a very limited extent. The amount and the characteristics of the released particles determine the potential environmental exposure. In this work we investigated the release of Ti from paints containing pigment-TiO2 and nano-TiO2. Panels covered with paint with and without nano-TiO2 were exposed to simulated weathering by sunlight and rain in climate chambers. The same paints were also studied in small-scale leaching tests to elucidate the influence of various parameters on the release such as composition of water, type of support and UV-light. Under all conditions we only observed a very low release close to background values, less than 1.5 μg l(-1) in the climate chamber over 113 irrigations per drying cycle and between 0.5 and 14 μg l(-1) in the leaching tests, with the highest concentrations observed after prolonged UV-exposure. The actual release of Ti over the 113 weathering cycles was only 0.007% of the total Ti, indicating that TiO2 was strongly bound in the paint. Extraction of UV-exposed and then milled paint resulted in about 100-times larger release of Ti from the nano-TiO2 containing paint whereas the paint with only pigment-TiO2 did not show this increase. This indicated that the release of Ti from the paints is an effect of the addition of nano-TiO2, either by photocatalytic degradation of the organic paint matrix (observed by electron microscopic imaging of the paint surface) or by direct release of nano-TiO2. Our work suggests that paints containing nano-TiO2 may release only very limited amounts of materials into the environment, at least over the time-scales investigated in this work.