HIV Drug-resistant Strains as Epidemiologic Sentinels

The decrease in the proportion of drug resistance among newly infected HIV-1 patients may signal a worsening of the epidemic

Rigid and high-numerical-aperture two-photon fluorescence endoscope

We present a rigid miniaturized optical system block fiber-optic two-photon endoscope based on a compact two-axis piezo scanner system and a miniature high (0.65) NA GRIN lens objective. The optical system is scanned as a whole by a piezo scanner allowing always an on-axis beam irradiation of the optical system. A photonic crystal fiber is used for excitation and ultrashort laser pulses can be delivered with typical power up to 100 mW at 800 run. Two-photon fluorescence signal is collected by the use of a multimode fiber. Lateral resolution values for the system were experimentally measured to be 0.67 mu m vertically and 1.08 mu m horizontally. Axial resolution was found to be 5.8 mu m. The endoscope is highly flexible and controllable in terms of time acquisition, resolution, and magnification. Fluorescence images were acquired over a 420 mu m x 420 mu m field of view. Results presented here demonstrate the ability of the system to resolve subcellular details and the potential of the technology for in vivo applications

Large-area, uniform, high-spatial-frequency ripples generated on silicon using a nanojoule-femtosecond laser at high repetition rate

Large-area high-spatial-frequency patterns (HSFLs) of /6 periodicity have been generated by a nanojoule-femtosecond laser scanning technique (80MHz, 170 fs, 700-950nm) at the silicon-air interface. The excellent large-area uniformity allowed reproducible and accurate measurements of the periodicity. Variation of experimental parameters as illumination geometry, and pulse energy and number showed no influence on the ripple spacing. A wavelength dependence was observed and compared to current models of HSFL formation. A particular second- armonic model was found to match the results best but needs to take into account transient changes in the refractive index under laser exposure. A second-harmonic mechanism is further supported by direct spectroscopic observation

Nanoparticle-loaded bioactive hydrogels

Laser-induced sub 100 nm structures were prepared on silicon, thoroughly characterized, and the process of their formation was elucidated. They were used as substrates for a controlled deposition of calcium phosphate nanoparticles by electrophoretic deposition. Calcium phosphate nanoparticles are used as carriers for biomolecules such as nucleic acid for transfection or gene silencing in the context of gene therapy. It is important to apply only a defined quantity of nanoparticles and nucleic acids to a given cell culture or tissue. A defined number of nanoparticles were deposited onto a ripple structured silicon surface by electrophoretic deposition Alginate beads were then rolled on this surface allowing the nanoparticles to adsorb onto the surface of the alginate bead. This resulted in alginate beads with a defined quantity of particles and biomolecules on their surface. The effect of calcium phosphate nanoparticle-coated alginate beads on cells was studied by the hanging drop method