Sabrina Conoci

Tetrametallic Reduction of Dinitrogen: Formation of a Tetranuclear Samarium Dinitrogen Complex.

The cooperative attack of four (dipyrromethanyl)Sm(II) units on dinitrogen resulted in a novel tetranuclear samarium dinitrogen complex (shown schematically). The presence of halogen atoms inhibited reactivity with dinitrogen through the assembly of divalent samarium clusters. dipyrr=diphenylmethyldipyrrolide dianion.

Integrated PCR amplification and detection processes on a Lab-on-Chip platform: a new advanced solution for molecular diagnostics.

Abstract Background: Several microdevices have been developed to perform only a single step of a genotyping process, such as PCR or detection by probe hybridization. Here, we describe a Lab-on-Chip (LoC) platform integrating a PCR amplification microreactor with a customable microarray for the detection of sequence variations on human genomic DNA. Methods: Preliminary work was focused on developing the single analytical steps including PCR and labeling strategies of the amplified product by conventional reference systems. The optimized protocols included a 1:4 forward:reverse primer ratio for asymmetric PCR, and Cy5-dCTP multiple incorporation for the generation of a labeled PCR product to be hybridized to complementary probes bound to the chip surface. Results: Final conditions were applied to the fully integrated LoC platform for the detection of the IVSI-110 G>A mutation in the human β-globin (HBB) gene associated with β-thalassemia, used as a model of genetic application, allowing for correct genotyping of 25 samples that were heterozygous, homozygous or wild-type for this mutation. Conclusions: The overall results show that the present platform is very promising for rapid identification of DNA sequence variations in an integrated, cost effective and convenient silicon chip format. Clin Chem Lab Med 2010;48:329–36.

Monitoring photoswitching of azobenzene-based self-assembled monolayers on ultrathin platinum films by UV/Vis spectroscopy in the transmission modeElectronic supplementary information (ESI) available: synthesis and characterization of 1 and its photoisomerization in solution. See http://www.rsc.org/suppdata/jm/b3/b314710j/

The reversible trans ↔ cis photoisomerization of azobenzene-based self-assembled monolayers on ultrathin platinum films has been monitored for the first time by UV-Vis transmission spectroscopy with a conventional spectrophotometer.

Light-triggered DNA release by dynamic monolayer films

We illustrate a simple strategy to immobilize single and double strand DNA on a two-dimensional surface and to trigger their release under physiological conditions, under the exclusive control of light stimuli. A tailored azobenzene derivative has been self-assembled on transparent platinum electrodes to form cationic-terminated monolayer films. These monolayers encourage the binding of DNA with the metal surface through effective electrostatic interactions with the negatively charged polynucleotide backbone. Irradiation of the film with UVA light induces trans to cisisomerization of the photoresponsive azobenzene units leading to significant changes of surface hydrophilicity and decreasing the binding affinity for DNA, which is consequently released into the solution. It is shown that the amount of DNA released can be precisely tuned by controlling the illumination conditions and is strictly related to the photoinduced structural modifications at the film surface. After the release of DNA the functional monolayers can be recycled through illumination with visible light which causes the cis form of the azo-chromophore to revert to the trans form, restoring the initial conditions. Given the non-specific nature of the Coulombic interactions the approach presented herein may, in principle, also be extended from polynucleotides to other negatively charged biomolecules, making these dynamic monolayers appealing model systems from the perspective of nanoscaled devices for biomedical applications where spatiotemporal control of biological material is required.

Photoresponsive multilayer films by assembling cationic amphiphilic cyclodextrins and anionic porphyrins at the air/water interface

Densely packed hybrid monolayers of amphiphilic cyclodextrins incorporating hydrophilic porphyrins are formed at the air/water interface through electrostatic interaction and can be transferred onto quartz substrates by Langmuir–Schafer deposition. The resulting multilayers exhibit a good response to light excitation as proven by fluorescence emission, triplet–triplet absorption and singlet oxygen photogeneration.

Syn–anti conformation switching of a bis-porphyrin derivative at the air–water interface and in the solid state as an effective tool for chemical sensing

A Langmuir film of bis(zinc octaethylporphyrin) (ZnPP) was characterised at the air–water interface and its syn–anti conformation switching induced upon addition of aromatic amines was studied by infrared and UV–vis reflection spectroscopic methods. The highly specific interaction of ZnPP with aromatic amines was maintained even after the floating film was transferred onto solid supports by the Langmuir–Schaefer (LS) technique, enabling us to selectively sense aromatic amines at concentrations as low as 20 ppb. Furthermore, LS ZnPP active layer selectivity was evaluated in the presence of aliphatic amines.

Self-assembling and electrochromic films of bipyridinium building blocks

A bipyridinium bisthiol adsorbs spontaneously on the surface of optically-transparent platinum electrodes to form electrochromic multilayers.

Stickstoffixierung: Reduktion von N2 durch vier Metallfragmente unter Bildung eines vierkernigen Samarium-Distickstoffkomplexes

Der kooperative Angriff von vier (Dipyrromethanyl)SmII-Einheiten auf ein Stickstoffmolekul fuhrte zu einem vierkernigen Samarium-Distickstoffkomplex (schematisch gezeigt). Halogenatome verhindern die Reaktion mit Stickstoff, indem sie die zweiwertigen Samariumcluster abfangen. dipyrr=Diphenylmethyldipyrrolid-Dianion.

Single-step label-free hepatitis B virus detection by a piezoelectric biosensor

In this paper we describe a single step and label free method to selectively detect the HVB genome based on hybridization with simple linear ssDNA probes immobilized on the Au surfaces of a QCM resonator. It has been proved that selective sensing ability is obtained for a large DNA target, constituted by an HBV clone of 7 kbps through a proper optimization of the probe density. Actually, with a probe density of ∼4.0 × 1012 molecules per cm2 we were able to detect fmol cm−2 of HBV target, without using any amplification steps or labelling method. The results presented herein pave the way to the development of an easy to use and portable PoC sensor device for direct and fast HBV detection.

Electrochemical and Spectroscopic Behavior of Iron(III) Porphyrazines in Langmuir−Schäfer Films

Thin films of a newly synthesized iron(III) porphyrazine, LFeOESPz ( L = ClEtO, OESPz = ethylsulfanylporphyrazine), have been deposited by the Langmuir-Schafer (LS) technique (horizontal lifting) on ITO or gold substrates. Before deposition, the floating films have been investigated at the air-water interface by pressure/area per molecule (pi/ A) experiments, Brewster angle microscopy (BAM) and UV-vis reflection spectroscopy (RefSpec). The complex reacts with water subphase (pH 6.2) forming the mu-oxo dimer, which becomes the predominant component of the LS films ( LS-Fe) as indicated by optical, IR, XPS, and electrochemical data. LS-Fe multilayers exhibit, between open circuit potential (OCP) and +0.90 V (vs SCE), two independent peak pairs with formal potentials, E surf (I) and E surf(II) of +0.56 V and +0.78 V, respectively. According to dynamic voltammetric and coulometric experiments the peak pair at +0.56 V is attributed to one-electron process at the iron(III) centers on the monomer, while the peak pair at +0.78 V is associated to a four-electron process involving mu-oxo-dimer oligomers. LS-Fe films prove to be quite stable electrochemically between OCP and +0.90 V. The electrochemical stability decreases, however, when the potential range is extended both anodically and cathodically outside these limits, due to formation of new species. Upon incubation with TCA solutions, LS-Fe films show remarkable changes in the UV-vis spectra, which are consistent with a significant mu-oxo dimer --> monomer conversion. Addition of TCA to the electrochemical cell using a LS-Fe film as working electrode, results in a linear increase of a cathodic current peak near -0.40 V as the TCA concentration varies in the 0.1-2.0 mM range. This behavior is interpreted in terms of TCA inducing a progressive change in the composition of the LS-Fe films in favor of the monomeric iron(III) porphyrazine, which is responsible for the observed increase in the cathodic current near -0.40 V.