Photothermal microscopy: optical detection of small absorbers in scattering environments.

Photothermal microscopy enables detection of nanometer-sized objects solely based on their absorption. This technique allows efficient observation of various nano-objects in scattering media notably gold nanoparticles in cells. The extreme sensitivity of the method and the stability of the signals open numerous applications in spectroscopy, analytical chemistry and bioimaging. This review briefly describes the principle and the main characteristics of photothermal microscopy, with its major advantages and limitations, and exposes the principal applications that have been carried out since its first implementation.

CYP51 Mutations in the Fusarium solani Species Complex: First Clue to Understand the Low Susceptibility to Azoles of the Genus Fusarium.

Members of Fusarium solani species complex (FSSC) are cosmopolitan filamentous fungi responsible for invasive fungal infections in immunocompromised patients. Despite the treatment recommendations, many strains show reduced sensitivity to voriconazole. The objective of this work was to investigate the potential relationship between azole susceptibility and mutations in CYP51 protein sequences. Minimal inhibitory concentrations (MICs) for azole antifungals have been determined using the CLSI (Clinical and Laboratory Standards Institute) microdilution method on a panel of clinical and environmental strains. CYP51A, CYP51B and CYP51C genes for each strain have been sequenced using the Sanger method. Amino acid substitutions described in multiple azole-resistant Aspergillus fumigatus (mtrAf) strains have been sought and compared with other Fusarium complexes' strains. Our results show that FSSC exhibit point mutations similar to those described in mtrAf. Protein sequence alignments of CYP51A, CYP51B and CYP51C have highlighted different profiles based on sequence similarity. A link between voriconazole MICs and protein sequences was observed, suggesting that these mutations could be an explanation for the intrinsic azole resistance in the genus Fusarium. Thus, this innovative approach provided clues to understand low azole susceptibility in FSSC and may contribute to improving the treatment of FSSC infection.

Single-shot optical sectioning using two-color probes in HiLo fluorescence microscopy.

We describe a wide-field fluorescence microscope setup which combines HiLo microscopy technique with the use of a two-color fluorescent probe. It allows one-shot fluorescence optical sectioning of thick biological moving sample which is illuminated simultaneously with a flat and a structured pattern at two different wavelengths. Both homogenous and structured fluorescence images are spectrally separated at detection and combined similarly with the HiLo microscopy technique. We present optically sectioned full-field images of Xenopus laevis embryos acquired at 25 images/s frame rate.

Gravity measurements below 10-9 g with a transportable absolute quantum gravimeter.

Gravimetry is a well-established technique for the determination of sub-surface mass distribution needed in several fields of geoscience, and various types of gravimeters have been developed over the last 50 years. Among them, quantum gravimeters based on atom interferometry have shown top-level performance in terms of sensitivity, long-term stability and accuracy. Nevertheless, they have remained confined to laboratories due to their complex operation and high sensitivity to the external environment. Here we report on a novel, transportable, quantum gravimeter that can be operated under real world conditions by non-specialists, and measure the absolute gravitational acceleration continuously with a long-term stability below 10 nm.s-2 (1 µGal). It features several technological innovations that allow for high-precision gravity measurements, while keeping the instrument light and small enough for field measurements. The instrument was characterized in detail and its stability was evaluated during a month-long measurement campaign.

Compatibility of insulin over 24 hours in standard and bicarbonate-based peritoneal dialysis solutions contained in bags made of different materials.

BACKGROUND: The purpose of this study was to evaluate potency changes in insulin in different solutions and bag materials used for peritoneal dialysis (PD). One of the PD solutions (Physioneal) tested is available in two different solution containers, PVC and Clear-Flex. Four insulin concentrations (4 IU/L, 10 IU/L, 20 IU/L, and 40 IU/L) were evaluated. This range of concentrations was defined in accordance with standard medical practice. All PD solutions made by Baxter, Castlebar, Ireland. METHODS: Insulin determination was performed by immunoassay (ELISA). RESULTS: In Dianeal, more than 90% of the initial dose of insulin remained available up to 24 hours for all concentrations tested. In Physioneal, for the higher concentrations tested (10 IU/L, 20 IU/L, and 40 IU/L), more than 90% of the initial dose of insulin remained available up to 6 hours, and more than 80% up to 24 hours. For the Lowest concentration of insulin tested in Physioneal (4 IU/L), more than 90% of the initial dose of insulin remained available up to 3 hours, and more than 70% up to 24 hours. Also for the lowest concentration of insulin, recovery correlated with the pH of the tested solutions. This effect became apparent over the storage time. CONCLUSIONS: The data show that insulin adsorption is less than 10% during the first 3 hours for every PD solution tested. Insulin recovery tends to be stable or to decrease slightly over time for the lower insulin concentrations tested. The results for insulin recovery show a correlation with insulin concentration and with pH for the lowest insulin dose tested. From a solution-container interaction perspective, Clear-Flex is an equivalent alternative to standard PVC material.

Adaptive optics for fluorescence wide-field microscopy using spectrally independent guide star and markers.

We describe the implementation and use of an adaptive optics loop in the imaging path of a commercial wide field microscope. We show that it is possible to maintain the optical performances of the original microscope when imaging through aberrant biological samples. The sources used for illuminating the adaptive optics loop are spectrally independent, in excitation and emission, from the sample, so they do not appear in the final image, and their use does not contribute to the sample bleaching. Results are compared with equivalent images obtained with an identical microscope devoid of adaptive optics system.