Quantum state tomography of dissociating molecules

Using tomographic reconstruction we determine the complete internuclear quantum state, represented by the Wigner function, of a dissociating I2 molecule based on femtosecond time resolved position and momentum distributions of the atomic fragments. The experimental data are recorded by timed ionization of the photofragments with an intense 20 fs laser pulse. Our reconstruction method, which relies on Jaynes' maximum entropy principle, will also be applicable to time resolved position or momentum data obtained with other experimental techniques

Detection of miRNA cancer biomarkers using light activated Molecular Beacons

Early detection of cancer biomarkers can reduce cancer mortality rate. miRNAs are small non-coding RNAs whose expression changes upon the onset of various types of cancer. Biosensors that specifically detect such biomarkers can be engineered and integrated into point-of-care devices (POC) using label-free detection, high sensibility and compactness. In this paper, a new engineered Molecular Beacon (MB) construct used to detect miRNAs is presented. Such a construct is immobilized onto biosensor surfaces in a covalent and spatially oriented way using the photonic technology Light Assisted Molecular Immobilization (LAMI). The construct consists of a Cy3 labelled MB covalently attached to a light-switchable peptide. One MB construct contains a poly-A sequence in its loop region while the other contains a sequence complementary to the cancer biomarker miRNA-21. The constructs have been characterized by UV-Vis spectroscopy, mass spectrometry and HPLC. LAMI led to the successful immobilization of the engineered constructs onto thiol functionalized optically flat quartz slides and Silicon on Insulator (SOI) sensor surfaces. The immobilized Cy3 labelled MB construct has been imaged using confocal fluorescence microscopy (CFM). The bioavailability of the immobilized engineered MB biosensors was confirmed through specific hybridization with the Cy5 labelled complementary sequence and imaged by CFM and FRET. Hybridization kinetics have been monitored using steady state fluorescence spectroscopy. The label-free detection of miRNA-21 was also achieved by using integrated photonic sensing structures. The engineered light sensitive constructs can be immobilized onto thiol reactive surfaces and are currently being integrated in a POC device for the detection of cancer biomarkers

Engineering 3D Multi-Branched Nanostructures for Ultra- Sensing Applications

The fabrication of plasmonic nanostructures with sub-10 nm gaps supporting extremely large electric field enhancement (hot-spot) has attained great interest over the past years, especially in ultra-sensing applications. The “hot-spot” concept has been successfully implemented in surface-enhanced Raman spectroscopy (SERS) through the extensive exploitation of localized surface plasmon resonances. However, the detection of analyte molecules at ultra-low concentrations, i.e., down to the single/few molecule level, still remains an open challenge due to the poor localization of analyte molecules onto the hot-spot region. On the other hand, three-dimensional nanostructures with multiple branches have been recently introduced, demonstrating breakthrough performances in hot-spot-mediated ultra-sensitive detection. Multi-branched nanostructures support high hot-spot densities with large electromagnetic (EM) fields at the interparticle separations and sharp edges, and exhibit excellent uniformity and morphological homogeneity, thus allowing for unprecedented reproducibility in the SERS signals. 3D multi-branched nanostructures with various configurations are engineered for high hot-spot density SERS substrates, showing an enhancement factor of 1011 with a low detection limit of 1 fM. In this view, multi-branched nanostructures assume enormous importance in analyte detection at ultra-low concentrations, where the superior hot-spot density can promote the identification of probe molecules with increased contrast and spatial resolution