Biomedical subjects

Antonio Virgilio Failla

Publications and source records attributed to Antonio Virgilio Failla.

5 recordsLinked to original sources

PubMed2006

Orientational imaging of subwavelength Au particles with higher order laser modes.

We present a new method for the imaging of single metallic nanoparticles that provides information about their shape and orientation. Using confocal microscopy in combination with higher order laser modes, scattering images of individual particles are recorded. Gold nanospheres and nonorods render characteristic patterns reflecting the different particle geometries. In the case of nanorods, the scattering patterns also reveal the orientation of the particles. This novel technique provides a promising tool for the visualization of nonbleaching labels in the biosciences.

Gold↗

PubMed2005

Microcavity-controlled single-molecule fluorescence.

We present for the first time cavity-controlled fluorescence spectra and decay curves of single dipole emitters interacting at room temperature with the first longitudinal mode of a Fabry-Perot microcavity offering a lambda/2-spacing between its silver mirrors. The spontaneous emission rate of individual dye molecules was found to be enhanced by the Purcell effect by up to three times compared to the rate in free space, in agreement with theoretical predictions. Moreover, our new microcavity design was found to provide long-term stability and single-molecule sensitivity under ambient conditions for several months without noticeable reduction of the cavity-Q value. We consider this as a significant advance for single-photon sources operating at room temperature.

Journal Article↗

PubMed2004

Measuring the size of biological nanostructures with spatially modulated illumination microscopy.

Spatially modulated illumination fluorescence microscopy can in theory measure the sizes of objects with a diameter ranging between 10 and 200 nm and has allowed accurate size measurement of subresolution fluorescent beads ( approximately 40-100 nm). Biological structures in this size range have so far been measured by electron microscopy. Here, we have labeled sites containing the active, hyperphosphorylated form of RNA polymerase II in the nucleus of HeLa cells by using the antibody H5. The spatially modulated illumination-microscope was compared with confocal laser scanning and electron microscopes and found to be suitable for measuring the size of cellular nanostructures in a biological setting. The hyperphosphorylated form of polymerase II was found in structures with a diameter of approximately 70 nm, well below the 200-nm resolution limit of standard fluorescence microscopes.

Cell Nucleus↗

PubMed2002

Subwavelength size determination by spatially modulated illumination virtual microscopy.

A new approach for determining the sizes of individual, small fluorescent objects with diameters considerably below the optical resolution limit is described in which spatially modulated illumination (SMI) microscopy and 360-647-nm excitation wavelengths are used. The results of SMI virtual microscopy computer simulations indicate that, in this wavelength range, reliable measurements of sizes as small as approximately 20 nm are feasible if the low numbers of fluorescence photons that are usually detected from such small objects are taken into account. This method is based on the well-known fact that the modulation of the diffraction image in a SMI microscope is disturbed by the size of the object. Using appropriately calculated calibration functions, one can use this disturbance of the modulation to determine the size of the original object.

Journal Article↗

PubMed2002

Spatially modulated illumination microscopy allows axial distance resolution in the nanometer range.

For an improved understanding of the structural basis of cellular mechanisms, it is highly desirable to develop methods for a detailed topological analysis of biological nanostructures and their dynamics in the interior of three-dimensionally conserved cells. We present a method of far-field laser fluorescence microscopy to measure relative axial positions of pointlike fluorescent targets and the distance between each target in the range of a few nanometers. The physical principle behind this approach can be extended to the determination of three-dimensional (3D) positions and 3D distances between any number of objects that can be discriminated owing to their spectral signature, thus allowing topological measurements so far regarded to be beyond the capabilities of light microscopy.

Algorithms↗