Lipid-Based Passivation in Nanofluidics

Stretching DNA in nanochannels is a useful tool for direct, visual studies of genomic DNA at the single molecule level. To facilitate the study of the interaction of linear DNA with proteins in nanochannels, we have implemented a highly effective passivation scheme based on lipid bilayers. We demonstrate virtually complete long-term passivation of nanochannel surfaces to a range of relevant reagents, including streptavidin-coated quantum dots, RecA proteins, and RecA-DNA complexes. We show that the performance of the lipid bilayer is significantly better than that of standard bovine serum albumin-based passivation. Finally, we show how the passivated devices allow us to monitor single DNA cleavage events during enzymatic degradation by DNase I. We expect that our approach will open up for detailed, systematic studies of a wide range of protein-DNA interactions with high spatial and temporal resolution

Evaporation and deposition of alkyl-capped silicon nanocrystals in ultrahigh vacuum

Nanocrystals are under active investigation because of their interesting size- dependent properties(1,2) and potential applications(3-5). Silicon nanocrystals have been studied for possible uses in optoelectronics(6), and may be relevant to the understanding of natural processes such as lightning strikes(7). Gas-phase methods can be used to prepare nanocrystals, and mass spectrometric techniques have been used to analyse Au-8,(9) and CdSe clusters(10). However, it is difficult to study nanocrystals by such methods unless they are synthesized in the gas phase(11). In particular, pre-prepared nanocrystals are generally difficult to sublime without decomposition. Here we report the observation that films of alkyl-capped silicon nanocrystals evaporate upon heating in ultrahigh vacuum at 200 degrees C, and the vapour of intact nanocrystals can be collected on a variety of solid substrates. This effect may be useful for the controlled preparation of new quantum-confined silicon structures and could facilitate their mass spectroscopic study and size- selection(12)

Preparation, Luminescent Properties and Bioimaging Application of Quantum Dots Based on Si and SiC

International audienceWell-known, the interest to the colloidal solution with quantum dots (QDs) lies in their fluorescence properties. Among the advantages of QDs are the high resistance to photooxidation, the size and composition variation allowing to obtain the narrow emission spectra with high quantum yield from the ultraviolet to the near infrared region. In this chapter we present the last achievements in forming and bio-medical applications of luminescent Si and SiC QDs. It is shown that a broad size distribution of Si QDs are obtained at electrochemical etching. The dimensions of the Si QDs undergone filtering in colloidal solution vary discretely with a radius quantum equal to 0.12 nm. Existing of this quantum may correspond to step-like increasing of Si QDs radius on one new shell at the surface of Si QDs. The formed QDs show intense luminescent in visual region. However, one of the major drawbacks of Si QDs for bio-medical application is instability over time in water or buffer solutions. To overcome this drawback the several methods of surface functionalization are discussed. The SiC QDs are stable in water solutions and do not require supplementary surface functionalisation for bioimaging. A strong fluorescence from the SiC QDs, which undoubtedly penetrate into the cell, has been observed. The studying of health and cancer cells using SiC QDs shows that simple modification of surface charge of QDs gives strong opportunity to target the same QDs in intracellular space with their preferential localisation inside or outside the cell nucleus