International audienceUnder nano- to femtosecond pulsed illumination at their plasmonic resonance wavelength, metalnanoparticles efficiently absorb the incident light energy that is subsequently converted into heat. In aliquid environment, with sufficiently high pulse fluences (light energy per unit area), this heat generationmay result in the local formation of a transient nanobubble. This phenomenon has been the subjectof a decade of investigations and is at the basis of numerous applications from cancer therapy to photoacouticimaging. The aim of this article is to clarify the question of the fluence threshold requiredfor bubble formation. Using a Runge-Kutta-4 numerical algorithm modeling the heat diffusion arounda spherical gold nanoparticle, we numerically investigate the influence of the nanoparticle diameter,pulse duration (from the femto- to the nanosecond range), wavelength and Kapitza resistivity in orderto explain the observations reported in the literature

Exhibiting a red-shifted absorption/scattering feature compared to conventional plasmonic metals, titanium nitride nanoparticles (TiN NPs) look as very promising candidates for biomedical applications, but these applications are still underexplored despite the presence of extensive data for conventional plasmonic counterparts. Here, we report the fabrication of ultrapure, size-tunable TiN NPs by methods of femtosecond laser ablation in liquids and their biological testing. We show that TiN NPs demonstrate strong and broad plasmonic peak around 640–700 nm with a significant tail over 800 nm even for small NPs sizes (<7 nm). In vitro tests of laser-synthesized TiN NPs on cellular models evidence their low cytotoxicity and excellent cell uptake. We finally demonstrate a strong photothermal therapy effect on U87–MG cancer cell cultures using TiN NPs as sensitizers of local hyperthermia under near-infrared laser excitation. Based on absorption band in the region of relative tissue transparency and acceptable biocompatibility, laser-synthesized TiN NPs promise the advancement of biomedical modalities employing plasmonic effects, including absorption/scattering contrast imaging, photothermal therapy, photoacoustic imaging and SERS.

International audienceThis article introduces the concept of photothermal isosbesticity in plasmonics. In analogy with absorbance spectroscopy, this concept designates nanostructures that feature an invariance of their temperature increase upon varying the illumination polarization angle. We show that nontrivial (i.e., non-centrosymmetric) isosbestic nanostructures exist and prove valuable when the optical near-field intensity remains, on the contrary, highly dependent on the illumination polarization. The concept is introduced with the case of a sphere-dimer, where the conditions for isosbesticity can be derived analytically. The cases of a spheroid and a disc-dimer are also studied in order to draw a general theory and explain how isosbesticity conditions can be obtained from the visible to the infrared range. Nontrivial isosbestic plasmonic nanostructures represent powerful systems to elucidate the origin (thermal or optical) of mechanisms involved in plasmonics-assisted nanochemistry, liquid–gas phase transition, or heat-assisted magnetic recording

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In this paper, a near-field tomographic solution is introduced to solve the imaging problem of fluid objects assumed to be weakly heterogeneous (Born approximation) and excited by spherical waves. The solution to the forward problem is based on the Huygens-Fresnel principle which describes the scattered field as the result of the interference scheme of all the secondary spherical waves. From the derivation of the scattered field, a new Fourier transform that has been called the elliptical Fourier transform is defined: It differs from the standard Fourier transform in that instead of a plane wave decomposition, a harmonic ellipsoidal wave decomposition is obtained. Based on this spectral analysis, a near-field Radon transform is designed that complements the "far-field tools" published in diffraction tomography literature. Then, assuming that the measuring distance is greater than one wavelength, the feasibility of reconstructing either the impedance or the velocity maps of an acoustical (perfect fluid) model is demonstrated. Numerical simulations were performed which confirmed the validity of the theory presented here; a theory which has many potential applications in future wave theory research.

The anticoccidial effect of C. papaya and V. amygdalina crude juice was tested on 100 Eimeria tenella experimentally infected day-old Isa-brown male chicks in a completely randomized design, as an alternative coccidiosis control measure. Each chick received 3 x 10 4 E. tenella oocysts doses. The first and the second groups were orally treated with papaya and vernonia juice, for consecutive 5 days. The third and the fourth groups were medicated (sulfadimidine) and unmedicated controls. The papaya treatment improved the survivability by 20% compared with the unmedicated control group. Neither death nor bloody feces were found in the medicated control chick group. Similar body weight gains were observed in all groups at the end of the second week post inoculation. However, the papaya and vernonia effect represents only 59.31 and 40.78% of the medicated control efficacy, respectively, in terms of oocysts excretion reduction. Carica papaya did demonstrate in this first herein preliminary study an anticoccidial effect, however, the active substance need to be extracted and its dose and toxicity threshold to be further investigated.

Gene therapy represents a powerful therapeutic tool to treat diseased tissues and provide a durable and effective correction. The central nervous system (CNS) is the target of many gene therapy protocols, but its high complexity makes it one of the most difficult organs to reach, in part due to the blood-brain barrier that protects it from external threats. Focused ultrasound (FUS) coupled with microbubbles appears as a technological breakthrough to deliver therapeutic agents into the CNS. While most studies focus on a specific targeted area of the brain, the present work proposes to permeabilize the entire brain for gene therapy in several pathologies. Our results show that, after i.v. administration and FUS sonication in a raster scan manner, a self-complementary AAV9-CMV-GFP vector strongly and safely infected the whole brain of mice. An increase in vector DNA (19.8 times), GFP mRNA (16.4 times), and GFP protein levels (17.4 times) was measured in whole brain extracts of FUS-treated GFP injected mice compared to non-FUS GFP injected mice. In addition to this increase in GFP levels, on average, a 7.3-fold increase of infected cells in the cortex, hippocampus, and striatum was observed. No side effects were detected in the brain of treated mice. The combining of FUS and AAV-based gene delivery represents a significant improvement in the treatment of neurological genetic diseases.

Ultrasound tomography has considerable potential as a means of breast cancer detection because it reduces the operator-dependency observed in echography. A half-ring transducer array was designed based on breast anatomy, to obtain reflectivity images of the ductolobular structures using tomographic reconstruction procedures. The 3-MHz transducer array comprises 1024 elements set in a 190-degree circular arc with a radius of 100 mm. The front-end electronics incorporate 32 independent parallel transmit/receive channels and a 32-to-1024 multiplexer unit. The transmit and receive circuitries have a variable sampling frequency of up to 80 MHz and 12-bit precision. Arbitrary waveforms are synthesized to improve the signal-to-noise ratio and to increase the spatial resolution when working with low-contrast objects. The setup was calibrated with academic objects and a needle hydrophone to develop the data correction tools and specify the properties of the system. The backscattering field was recorded using a restricted aperture, and tomographic acquisitions were performed with a pair of 0.08-mm-diameter steel wires, a low-contrast 2-D breast phantom, and a breast-shaped phantom containing inclusions. Data were processed with dedicated correction tools and a pulse compression technique. Objects were reconstructed using the elliptical back-projection algorithm.