Sebastian Schwung

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.

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.

Deep UV generation and direct DNA photo-interaction by harmonic nanoparticles in labelled samples

A novel bio-photonics approach based on the nonlinear optical process of second harmonic generation by non-centrosymmetric nanoparticles is presented and demonstrated on malignant human cell lines. The proposed method allows to directly interact with DNA in absence of photosensitizing molecules, to enable independent imaging and therapeutic modalities switching between the two modes of operation by simply tuning the excitation laser wavelength, and to avoid any risk of spontaneous activation by any natural or artificial light source. ∗To whom correspondence should be addressed †Institute of Chemical Sciences and Engineering, EPFL, CH-1015, Lausanne, Switzerland ‡GAP-Biophotonics, Université de Genève, 22 chemin de Pinchat, CH-1211 Genève 4, Switzerland ¶FEE Gmbh, Struthstrasse 2, 55743 Idar-Oberstein, Germany §SYMME, Université de Savoie, BP 80439, 74944, Annecy Le Vieux Cedex, France ‖Contributed equally to this work. 1 ar X iv :1 30 6. 64 87 v1 [ ph ys ic s. bi oph ] 2 7 Ju n 20 13 We demonstrate here a novel diagnostic and therapeutic (theranostic) protocol based on the nonlinear optical process of non phase-matched second harmonic (SH) generation by non-centrosymmetric nanoparticles, referred to in the following as harmonic nanoparticles (HNPs).1,2 To date, the capability of these recently introduced nanometric probes of doubling any incoming frequency has not been employed for therapeutic use, although it presents several straightforward advantages, including i) the possibility to directly interact with DNA of malignant cells in absence of photosensitizing molecules, ii) fully independent access to imaging and therapeutic modalities, and iii) complete absence of risk of spontaneous activation by natural or artificial light sources other than pulsed femtosecond lasers. Given the unconstrained tunability of the HNPs nonlinear conversion process, this approach can be extended to selectively photo-activate molecules at the surface or in the vicinity of HNPs to further diversify the prospective therapeutic action.3 Here we show that by tuning the frequency of ultrashort laser pulses from infrared (IR) to visible (both harmless), SH generation leads respectively to diagnostics (imaging) and therapy (phototoxicity). Specifically, we report in situ generation of deep ultraviolet (DUV) radiation (270 nm) in human-derived lung cancer cells treated with bismuth ferrite (BiFeO3, BFO) HNPs upon pulsed laser irradiation in the visible spectrum, at 540 nm. We observe and quantify the appearance of double-strand breaks (DSBs) in the DNA and cell apoptosis, in the area of the laser beam. We show that DNA damages are dependent on irradiation-time, laser intensity, and NP concentration. We observe that apoptosis and genotoxic effects are only observed when visible light excitation is employed, being completely absent when IR excitation is used for imaging. HNPs, a family of NPs specifically conceived for multi-photon imaging, were introduced in 2005 for complementing fluorescence imaging labels.1,4,5 Although comparatively less bright than quantum dots, HNPs possess a series of advantageous optical properties, including complete absence of bleaching and blinking,1,6 spectrally narrow emission bands, fully coherent response,7–9 ,and UV to IR excitation wavelength tunability.10,11 These unique characteristics have been recently exploited in demanding bio-imaging applications12 including regenerative research.13 The possibility of working with long wavelengths presents clear advantages in terms of tissue pene-A biophotonics approach based on the nonlinear optical process of second harmonic generation is presented and demonstrated on malignant human cell lines labelled by harmonic nanoparticles. The method enables independent imaging and therapeutic action, selecting each modality by simply tuning the excitation laser wavelength from infrared to visible. In particular, the generation of deep ultraviolet radiation at 270 nm allows direct interaction with nuclear DNA in the absence of photosensitizing molecules.

Harmonic nanoparticles for nonlinar bio-imaging and detection

In this contribution we present the motivations underlying the introduction of harmonic nanoparticles, i.e. second harmonic contrast agents for nonlinear microscopy. Their properties will be discussed in the light of various biological applications including imaging of stem cells and rare event detection in physiological media.