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Several authors demonstrated that an oligonucleotide based pH-sensitive construct can act as a switch between an open and a closed state by changing the pH. To validate this process, specially designed fluorescence dye–quencher substituted oligonucleotide constructs were developed to probe the switching between these two states. This paper reports on bulk and single molecule fluorescence investigations of a duplex–triplex pH sensitive oligonucleotide switch. On the bulk level, only a partial quenching of the fluorescence is observed, similarly to what is observed for other published switches and is supposed to be due to intermolecular interactions between oligonucleotide strands. On the single molecule level, each DNA-based nanometric construct shows a complete switching. These observations suggest the tendency of the DNA construct to associate at high concentration. [ABSTRACT FROM AUTHOR]

Hybrid organic−inorganic nanocomposites were prepared starting from ,-triethoxysilane-terminated poly(d,l-lactic acid) (PDLLA) to be used as potential radiopaque biocompatible coatings for medical devices. The synthesis of the organic phase precursors of given chain length was achieved via anionic polymerization of d,l-lactide using a bifunctional initiator and subsequent triethoxysilane functionalization of the end groups. PDLLA-based ceramers (ceramic polymers) were then synthesized by the sol−gel process at room temperature (rt) in the presence of different amounts of tetraethoxysilane. The rt-synthesized hybrids were then cured (at 80 or 130 °C), and their thermal and viscoelastic properties were investigated. All obtained hybrids were optically transparent, due to the nanometric dimension of the silica particles, and yielded clearly contrasted radiographic images. [ABSTRACT FROM AUTHOR]