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International audience; An ideal diagnostic fluorescent nanoprobe should comprise a nanocrystal with the highest possible fluorescencebrightness and a highly specific capture molecule, which should be as small as possible. Furthermore, all capture molecules linked to the nanocrystal should be so oriented that their antigen-binding centers be accessible for antigens and not blocked by the nanocrystal surface.The brightness of fluorescence nanocrystals, so-called QDs, is more than an order of magnitude higher than that of thebest organic fluorophores; QDs are thousands of times more photostable; and fluorescence of QDs of different colors can be excited by light of the same wavelength. The monomeric single-domain antibodies (sdAbs), the smallest known antigenrecognizing molecules, which are derived from immunoglobulins of camelids and sharks, are 12 times smaller than full-size antibodies while preserving about the same affinity for antigens. They are also extremely stable and capable of refolding.We have obtained oriented conjugates of sdAbs with water-soluble QDs. The desirable orientation of sdAbs relativeto the nanocrystal surface was ensured by adding an amino acid residue to the C-end of the antibody peptide chainand subsequently linking the antibody to the nanocrystal through this residue.

International audience; Semiconductor quantum dots (QDs) are characterized by high extinction coefficients adjustable by varying the nanoparticle size and a high quantum yield of charge generation. QDs have the advantage of efficient charge transfer from them to organic semiconductors. We have developed hybrid materials based on semiconductor organic semiconductors polyimide (PI) or poly(2-methoxy-5(2'-ethyl) hexoxy-phenylenevinylene) (MEH-PPV) and CdSe QDs. The photovoltaic efficiency of optimized PI- QDs structures approaches that of the best performing systems based on the MEH-PPV. Incorporation of QDs in MEH-PPV has been demonstrated to increase the photovoltaic efficiency of the system by 50 %, thus allowing the development of novel QD-based inorganic/organic hybrid materials with considerably improved photovoltaic properties.

Expression of the P-glycoprotein (Pgp) is proved to be one of the main reasons for the development of the multidrug resistance (MDR) phenotype by cancer cells. The effect of Pgp on the properties of lipid monolayers was studied using membrane fractions of sensitive and Pgp over-expressing multidrug resistance cancer cells containing 11, 24 or 32% of Pgp relative to the total content of membrane proteins. The effect of the Pgp membrane concentration on the properties of monolayers prepared from the membrane fractions was analyzed by the Langmuir-Blodgett method. The subphase composition was found to play a critical role in the stability of monolayers at any Pgp concentration. The optimal subphase comprised 10 mM tris-HCl buffer, pH 6.5, which made it possible to create very stable monolayer films with the pressure of collapse of about 30-40 mN/m. Monolayers prepared from membrane fractions of sensitive cells and cells containing the maximum (32%) amount of Pgp were found to be much more stable compared with fractions comprising 11 or 24% of Pgp. The analysis of monolayer compression dynamics revealed three distinct stages: (1) the self-organization of lipid molecules, which is characterized by an abrupt change of surface potential; (2) the compression of Pgp molecules at the constant potential of monolayers; and (3) the compression of lipid molecules, which is characterized by a quasilinear increase of both pressure and surface potential. It was shown that the specific surface areas of monolayers formed from sensitive and Pgp-enriched membranes containing 11 or 24% of Pgp are very similar, whereas the surface area of the monolayer formed from membranes containing 32% of Pgp is nearly 1.5-fold greater. This fact may reflect the effect of the threshold rearrangement of the structure of lipid molecules or cooperative modifications of lipid-Pgp interactions induced by the increase in the Pgp content from 24 to 32%. The effect of verapamil, a well-known Pgp modulator, on the properties of monolayers was studied. It was show that verapamil is able to induce changes of the surface of Pgp-containing monolayers, and these modifications are maximal at the Pgp:verapamil 1:1 molar ratio. The data present the first experimental evidence for the possible intervention of Pgp modulator into the processes of lipid-lipid or lipid-Pgp cooperative interactions within Pgp-enriched membranes.