Yannick Mugnier

Harmonic nanocrystals for biolabeling: a survey of optical properties and biocompatibility.

Nonlinear optical nanocrystals have been recently introduced as a promising alternative to fluorescent probes for multiphoton microscopy. We present for the first time a complete survey of the properties of five nanomaterials (KNbO(3), LiNbO(3), BaTiO(3), KTP, and ZnO), describing their preparation and stabilization and providing quantitative estimations of their nonlinear optical response. In the light of their prospective use as biological and clinical markers, we assess their biocompatibility on human healthy and cancerous cell lines. Finally, we demonstrate the great potential for cell imaging of these inherently nonlinear probes in terms of optical contrast, wavelength flexibility, and signal photostability.

Individual inorganic nanoparticles: preparation, functionalization and in vitro biomedical diagnostic applications

Inorganic nanoparticles have become the focus of modern materials science due to their potential technological importance, particularly in bionanotechnology, which stems from their unique physical properties including size-dependent optical, magnetic, electronic, and catalytic properties. The present article provides an overview on the currently used individual inorganic nanoparticles for in vitro biomedical domains. These inorganic nanoparticles include iron oxides, gold, silver, silica, quantum dots (QDs) and second harmonic generation (SHG) particles. For each of these interesting nanoparticles, the main issues starting from preparation up to bio-related applications are presented.

Nanodoublers as deep imaging markers for multi-photon microscopy

We demonstrate the possibility to excite second-harmonic (SH) active Fe(IO(3))(3) nanocrystals with two distinct laser sources at 800 and 1550 nm, and we show, by a complementary experimental and numerical study, how the wavelength flexibility inherent to non-phase-matched SH nanoparticles can be efficiently exploited to increase imaging penetration depth of markers embedded in biological samples.

Polymer encapsulation of inorganic nanoparticles for biomedical applications

Hybrid inorganic colloidal particles have attracted a great attention in the last years, and they have been largely used in various applications and more particularly in biomedical nanotechnology. Recently, they are used as carriers for biomolecules, and exploited for use in microsystems, microfluidics and in lab-on-a chip based bionanotechnology. Various kinds of hybrid particles can be listed starting from classical inorganic nanoparticles such as silica, gold, silver, iron oxide and those exhibiting intrinsic properties such as semiconducting nanoparticles (e.g. quantum dots). As a general tendency, to be conveniently used in biomedical applications, the encapsulation of the inorganic nanoparticles in a polymer matrix is incontestably needed. Consequently, various chemistry-based encapsulation processes have been developed and showed promising results as compared to the encapsulation using preformed polymers.

Nano-FROG: Frequency Resolved Optical Gating by a nanometric object

We present a technique to characterize ultrashort pulses at the focal plane of a high numerical aperture objective with unprecedented spatial resolution, by performing a FROG measurement with a single nanocrystal as nonlinear medium. This approach can be extended to develop novel phase-sensitive techniques in laser scanning microscopy, probing the microscopic environment by monitoring phase and amplitude distortions of femtosecond laser pulses.

Characterization of the nonlinear optical properties of nanocrystals by Hyper Rayleigh Scattering

BackgroundHarmonic Nanoparticles are a new family of exogenous markers for multiphoton imaging exerting optical contrast by second harmonic (SH) generation. In this tutorial, we present the application of Hyper-Rayleigh Scattering (HRS) for a quantitative assessment of the nonlinear optical properties of these particles and discuss the underlying theory and some crucial experimental aspects.MethodsThe second harmonic properties of BaTiO3, KNbO3, KiTiOPO4 (KTP), LiNbO3 and ZnO nanocrystals (NCs) are investigated by HRS measurements after careful preparation and characterization of colloidal suspensions.ResultsA detailed analysis of the experimental results is presented with emphasis on the theoretical background and on the influence of some experimental parameters including the accurate determination of the nanocrystal size and concentration. The SH generation efficiency and averaged nonlinear optical coefficients are then derived and compared for six different types of NCs.ConclusionsAfter preparation of colloidal NC suspensions and careful examination of their size, concentration and possible aggregation state, HRS appears as a valuable tool to quantitatively assess the SH efficiency of noncentrosymmetric NCs. All the investigated nanomaterials show high SH conversion efficiencies, demonstrating a good potential for bio-labelling applications.

High‐Speed Tracking of Murine Cardiac Stem Cells by Harmonic Nanodoublers

Potassium niobate nonlinear nanoparticles are used for the first time to monitor the evolution of embryonic stem cells (ESC) by second harmonic microscopy. These particles feature the complete absence of photo-bleaching and unlimited excitation wavelength flexibility. The potential of this approach is made evident for tissue-regeneration studies and applications, by capturing a high-speed movie of ESC-derived cardiomyocytes autonomously beating within a cluster. Time-resolved data are analyzed to retrieve 3D information of the contraction pattern at the cellular level.

Harmonic nanoparticles: noncentrosymmetric metal oxides for nonlinear optics

response, often referred to as harmonicnanoparticles (HNPs). HNPs feature a series of properties which distinguish them from otherphotonics nanoprobes (quantum dots, up-conversion nanoparticles, noble metal particles). HNPsemission is inherently nonlinear and based on the efficient generation of harmonics as opposed tofluorescence or surface plasmon scattering. In addition, the fully coherent signal emitted byHNPs together with their polarization sensitive response and absence of resonant interactionmake them appealing for several applications ranging from multi-photon (infrared) microscopyand holography, to cell tracking and sensing.Keywords: multiphoton microscopy, second harmonic generation, third harmonic generation,nonlinear optics, nanophotonics, perovskites(Some figures may appear in colour only in the online journal)1. IntroductionSince the advent of ultrafast lasers in the early nineties andrelated availability of high peak power pulses at compara-tively low energies, the investigation of nonlinear opticalresponse have become a widespread activity resulting ininnovative applications. In particular, in the field of imagingthis has led to the introduction of multi-photon microscopy byW Webb [1]. This technique, as compared to one-photonexcited fluorescence microscopy, features increased imagingdepth, no out-of-focus bleaching, and spatial resolutioncomparable to confocal techniques without compromise insensitivity. The latest technological advancements in this fieldare related to its extension towards longer wavelengths,facilitated by the timely introduction of novel tunable sourcesin the 0.7–1.3 μm spectral range and new optical componentswith optimized performances in this region (microscopeobjectives, acousto-optic modulators, ...). Although these newinfrared tunable devices are supposedly more adapted forimaging through thick (living) samples because of reducedscattering [2–4], the available choice of imaging targets(fluorescent molecules, dyes) with two-photon absorptionbands >1200nm is very limited.Nanoparticle-based labelling, which is sometimes pre-ferred over other approaches for its superior photo-stability,brightness, and chemical selectivity usually requires two-photon interactions in the 700–900nm range, with a fewnotable exceptions [5]. However most optically active labelsmay suffer from bleaching and blinking and their use inbiological research might be prevented because of low bio-compatibility. For these reasons, since 2006, several researchgroups worldwide have proposed a complementary approach,

Nonlinear optical and magnetic properties of BiFeO3 harmonic nanoparticles

Second Harmonic Generation (SHG) from BiFeO3 nanocrystals is investigated for the first time to determine their potential as biomarkers for multiphoton imaging. Nanocrystals are produced by an auto-combustion method with 2-amino-2-hydroxymethyl-propane-1,3-diol as a fuel. Stable colloidal suspensions with mean particle diameters in the range 100–120 nm are then obtained after wet-milling and sonication steps. SHG properties are determined using two complementary experimental techniques, Hyper Rayleigh Scattering and nonlinear polarization microscopy. BiFeO3 shows a very high second harmonic efficiency with an averaged 〈d〉 coefficient of 79 ± 12 pm/V. From the nonlinear polarization response of individual nanocrystals, relative values of the independent dij coefficients are also determined and compared with recent theoretical and experimental studies. Additionally, the particles show a moderate magnetic response, which is attributed to γ-Fe2O3 impurities. A combination of high nonlinear optical efficiency and magnetic response within the same particle is of great interest for future bio-imaging and diagnostic applications.

Cellular uptake and biocompatibility of bismuth ferrite harmonic advanced nanoparticles

UNLABELLED Bismuth Ferrite (BFO) nanoparticles (BFO-NP) display interesting optical (nonlinear response) and magnetic properties which make them amenable for bio-oriented diagnostic applications as intra- and extra membrane contrast agents. Due to the relatively recent availability of this material in well dispersed nanometric form, its biocompatibility was not known to date. In this study, we present a thorough assessment of the effects of in vitro exposure of human adenocarcinoma (A549), lung squamous carcinoma (NCI-H520), and acute monocytic leukemia (THP-1) cell lines to uncoated and poly(ethylene glycol)-coated BFO-NP in the form of cytotoxicity, haemolytic response and biocompatibility. Our results support the attractiveness of the functional-BFO towards biomedical applications focused on advanced diagnostic imaging. FROM THE CLINICAL EDITOR Bismuth Ferrite nanoparticles (BFO-NP) have been recently successfully introduced as photodynamic tools and imaging probes. However, how these nanoparticles interact with various cells at the cellular level remains poorly understood. In this study, the authors performed in vitro experiments to assess the effects of uncoated and PEG-coated BFO-NP in the form of cytotoxicity, haemolytic response and biocompatibility.