A miniaturized silicon based device for nucleic acids electrochemical detection

In this paper we describe a novel portable system for nucleic acids electrochemical detection. The core of the system is a miniaturized silicon chip composed by planar microelectrodes. The chip is embedded on PCB board for the electrical driving and reading. The counter, reference and work microelectrodes are manufactured using the VLSI technology, the material is gold for reference and counter electrodes and platinum for working electrode. The device contains also a resistor to control and measuring the temperature for PCR thermal cycling. The reaction chamber has a total volume of 20 μL. It is made in hybrid silicon–plastic technology. Each device contains four independent electrochemical cells.Results show HBV Hepatitis-B virus detection using an unspecific DNA intercalating redox probe based on metal–organic compounds. The recognition event is sensitively detected by square wave voltammetry monitoring the redox signals of the intercalator that strongly binds to the double-stranded DNA. Two approaches were here evaluated: (a) intercalation of electrochemical unspecific probe on ds-DNA on homogeneous solution (homogeneous phase); (b) grafting of DNA probes on electrode surface (solid phase).The system and the method here reported offer better advantages in term of analytical performances compared to the standard commercial optical-based real-time PCR systems, with the additional incomes of being potentially cheaper and easier to integrate in a miniaturized device. Keywords: Electrochemical detection, Real time PCR, Unspecific DNA intercalato

Mechanistic Insights into Light-Activated Catalysis for Water Oxidation

The development of catalysts for water oxidation to oxygen has been the subject of intense investigation in the last decade. In parallel to the search for high catalytic performance, many works have focused on the mechanistic analysis of the process. In this perspective, the oxidation of water through light-assisted cycles composed of an electron acceptor (EA), a photosensitizer (PS), and a water oxidation catalyst (WOC) can provide insightful and complementary information with respect to the use of chemical oxidants or to electrochemical techniques. In this minireview, we discuss the mechanistic aspects of the EA/PS/WOC photoactivated cycles, and in particular: (i) the general elementary steps; (ii) the required features and the nature of the PS employed; (iii) the electron transfer processes and kinetics from the WOC to PS+ (hole scavenging); (iv) the detrimental quenching of the PS by the WOC and the alternative mechanistic routes; (v) the identification of WOC intermediates and, finally, (vi) the transposition of the above processes into a dye-sensitized photoanode embedding a WOC

Hybrid complexes: Pt(II)-terpyridine linked to various acetylide-bodipy subunits

By tailoring the chemistry of the 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (bodipy) core in order to change its spectroscopic properties, we linked some modified bodipy dyes to Pt(ii)-terpyridine centers thereby preparing three novel hybrid complexes. In one of such species, two pyrene subunits are also present. The absorption spectra and luminescence properties (both at room temperature in acetonitrile solution and at 77 K in butyronitrile rigid matrix) of the new hybrid complexes and of their bodipy parent species have been investigated, and compared with those of previously studied compounds. Absorption spectra showed that the different chromophoric subunits roughly keep their own features in the multicomponent systems, indicating the supramolecular nature of the compounds. Efficient photoinduced intercomponent energy transfer takes place in the various hybrid Pt(ii)-terpyridine-bodipy compounds, by taking advantage of different mechanisms: at room temperature in fluid solution very efficient energy transfer from the (3)MLCT state(s) of the Pt residue to the lowest-lying (3)bodipy is mediated by a charge transfer state via a two-step electron transfer process. Direct energy transfer from (3)MLCT state(s) to the (3)bodipy states takes place at 77 K, most likely via the Dexter mechanism. When two pyrene fragments are grafted to the boron, cascade energy transfer from the pyrene to the (1)bodipy also occurs by the Förster mechanism. For one of the new compounds, (3)bodipy emission with a maximum at 738 nm is also observed at cryogenic temperature

Ru(II)-Dppz Derivatives and Their Interactions with DNA: Thirty Years and Counting

Transition metal complexes with dppz-type ligands (dppz = dipyrido[3,2-a:2′,3′-c]phenazine) are extensively studied and attract a considerable amount of attention, becoming, from the very beginning and increasingly over time, a powerful tool for investigating the structure of the DNA helix. In particular, [Ru(bpy)2(dppz)]2+ and [Ru(phen)2(dppz)]2+ and their derivatives were extensively investigated as DNA light-switches. The purpose of this mini-review, which is not and could not be exhaustive, was to first introduce DNA and its importance at a biological level and research in the field of small molecules that are capable of interacting with it, in all its forms. A brief overview is given of the results obtained on the Ru-dppz complexes that bind to DNA. The mechanism of the light-switch active in this type of species is also briefly introduced along with its effects on structural modifications on both the dppz ligand and the ancillary ligands. Finally, a brief mention is made of biological applications and the developments obtained due to new spectroscopic techniques, both for understanding the mechanism of action and for cellular imaging applications

Synthesis, photophysical and redox behaviour of unsymmetrical binuclear Ru(II) complexes based on tris(1-pyrazolyl)methane

Six new unsymmetrical achiral complexes of RuII containing the tripodal ligand tris(1-pyrazolyl)methan (tpm) on both metal centers have been prepared and fully characterized. Their general formula is [CLa(tpm)Ru(μBL)Ru(tpm)CLb]4+, were CLa and CLb represent two different chelating ligands (2,2′-bipyridine (bpy), 1,10-phenanthroline (phen) or 2,2′-biquinoline (biq)); BL can be 4,4′-bipyridine (4,4′-bpy) or pirazine (pz). The structures of the new species have been elucidated by 1H NMR, COSY and NOESY spectroscopy. Electrochemical, UV–Vis spectroscopical, luminescence, and spectroelectrochemical properties have been investigated for all the binuclear complexes. For two representative species DFT calculations were carried out. The experimental data have been thoroughly interpreted in terms of the role played by each constituent subunit within the assemblies. These results add comparative pieces of information to the knowledge of the properties of the RuII-based complexes

Luminescent excited-state intramolecular proton-transfer (ESIPT) dyes based on 4-alkyne-functionalized [2,2'-bipyridine]-3,3'-diol dyes.

International audienceFunctionalized 6,6'-dimethyl-3,3'-dihydroxy-2,2'-bipyridine dyes (BP(OH)(2)) exhibit relatively intense fluorescence from the relaxed excited state formed by excited-state intramolecular proton transfer (ESIPT). Bromo functionalization of (BP(OH)(2)) species followed by palladium(0)-catalyzed reactions allows the connection (via alkyne tethers) of functional groups, such as the singlet-emitter diazaboraindacene (bodipy) group or a chelating module (terpyridine; terpy). The X-ray structure of the terpy-based compound confirms the planarity of the 3,3'-dihydroxy-bipyridine unit. The new dyes exhibit relatively intense emission on the nanosecond timescale when in fluid solution, in the solid state at 298 K, and in rigid glasses at 77 K. In some cases, the excitation wavelength luminescence was observed and attributed to 1) inefficiency of the ESIPT process in particular compounds when not enough vibrational energy is introduced in the Franck-Condon state, which is populated by direct light excitation or 2) the presence of an additional excited state that deactivates to the ground state without undergoing the ESIPT process. For some selected species, the effect of the addition of zinc salts on the absorption and luminescence spectra was investigated. In particular, significant fluorescence changes were observed as a consequence of probable consecutive formation of a 1:1 and 1:2 molecular ratio of ligand/zinc adducts owing to coordination of Zn(II) ions by the bipyridyldiol moieties, except when an additional terpyridine subunit is present. In fact, this latter species preferentially coordinates to the Zn(II) ion in a 1:1 molecular ratio and further inhibits Zn(II) interaction. In the hybrid Bodipy/BP(OH)(2) species, complete energy transfer from the BP(OH)(2) to the bodipy fluorophore occurs, leading to exclusive emission from the lowest-lying bodipy subunit