Force measurements between emulsion droplets-ssDNA conjugates: a new tool for medical diagnostics.

We describe here a new system involving direct force measurements between biomolecules that could be used in biomedical diagnostics. The method consists in the use of magnetic emulsion droplets bearing immobilized single stranded DNA fragments (ssDNA, Deoxyribo Nucleic Acid). The immobilized ssDNA fragments are able to recognize complementary DNA molecules via specific hydrogen binding (hybridization process). The ssDNA used in this study are 32 bases oligonucleotides functionalized at their 5' extremity with biotin and then immobilized onto the magnetic nanodroplets via interactions with streptavidin previously chemically grafted onto the nanomagnetic support. The aim of this work is to evaluate the possible detection of captured nucleic acid targets via single force measurements as an alternative to classical ELOSA (Enzyme Linked Oligo Sorbent Assay). The obtained results are discussed mainly in terms of electrostatic interactions.

The quantification of single cell adhesion on functionalized surfaces for cell sheet engineering.

The use of force spectroscopy to measure and quantify the forces involved in the adhesion of 3T3 fibroblasts to different chemically functionalized surfaces has been investigated. Cells were grown on glass surfaces as well as on surfaces used for cell sheet engineering: surfaces coated with polyelectrolyte multilayers (poly-L-lysine and hyaluronic acid) and thermally-responsive poly(N-isopropylacrylamide) (PNIPAM) brushes. Individual adherent cells were detached from their culture substrate using an AFM cantilever coated with fibronectin. The maximum forces of detachment of each cell were measured and taken as characteristic of the cellular adhesion. Large differences in cellular adhesion were observed on polyelectrolyte coatings depending on the number of polyelectrolyte layers. On PNIPAM-grafted surfaces, changes of more than an order of magnitude were observed in cell adhesion above and below the lower critical solution temperature. Glass surfaces patterned with periodic PNIPAM microdomains were also investigated, and it was shown that cellular adhesion could be reduced while keeping cellular morphology unchanged.

[Gastric leiomyosarcoma. Contribution of imaging to the diagnosis. Report of 2 cases]. / Les léiomyosarcomes gastriques. Apport de l'imagerie au diagnostic. A propos de deux cas.

Leiomyosarcomas, are rare gastric tumors with a tendency for extraluminal growth. In relation to two new cases, the authors report the various features and show the predominant value of computed tomography for the diagnosis.