David García-Fresnadillo

Determination of DNA guanine sites forming photo-adducts with Ru(II)-labeled oligonucleotides; DNA polymerase inhibition by the resulting photo-crosslinking.

The influence of the distance between the anchoring site of the tethered [Ru(TAP)2dip]2+ complex (TAP=1,4,5,8-tetraazaphenanthrene; dip=4,7-diphenyl-1,10-phenanthroline) on a probe sequence and the guanines of the complementary target strand was studied by (1) the luminescence quenching of the complex (by electron transfer) and (2) the oligodeoxyribonucleotide adduct (ODN adduct) formation which results in photo-crosslinking of the two strands. Moving the guanine moieties away from the complex induces an important decrease of the efficiency of both processes, but clearly affects the ODN adduct formation more specifically than the quenching process. From these results, we determined the positions of the guanine bases in the duplex ODN that are able to form a photo-adduct with the tethered complex. We also examined the possible competition between a long-range hole migration in the duplex ODN and the formation of a photo-adduct by using a sequence labeled with the complex at the 5′-phosphate end. Such a hole migration appears to be inefficient as compared to the ODN adduct formation. Finally, we studied the influence of the photo-crosslinking on the function of two different DNA polymerases. A 17-mer Ru(II)-labeled ODN was hybridized to its complementary sequence located on the 5′-side of a 40-mer matrix. After illumination, the elongation of a 13-mer DNA primer hybridized to the 3′-extremity of the same matrix was stopped at a position corresponding to the formation of the ODN adduct.

Interaction of Sulfonated Ruthenium(II) Polypyridine Complexes with Surfactants Probed by Luminescence Spectroscopy

Novel anionic [RuL2L′]2− complexes, where L stands for (1,10-phenanthroline-4,7-diyl)bis(benzenesulfonate) (pbbs; 3a) or (2,2′-bipyridine)-4,4′-disulfonate (bpds; 3b), and L′ is N-(1,10-phenanthrolin-5-yl)tetradecanamide (pta; 2a) or N-(1,10-phenanthrolin-5-yl)acetamide (paa; 2b), were synthesized, and their interaction with the prototypical surfactants sodium dodecylsulfate (SDS), cetyl trimethyl ammonium bromide (CTAB), and Triton X-100 (TX-100) was investigated by electronic absorption, luminescence spectroscopy, emission-lifetime determinations, and O2-quenching measurements. [Ru(pbbs)2(pta)]2− (5a) displayed cooperative self-aggregation in aqueous medium at concentrations above 1.3 μM; the observed association was enhanced in the presence of either β-cyclodextrin or NaCl. This amphiphilic RuII compound showed the strongest interaction with all the detergents tested: nucleation of surfactant molecules around the luminescent probe was observed below their respective critical micellar concentrations. As much as a 12-fold increase of the emission intensity and a 3-fold rise in the lifetime were measured for 5a bound to TX-100 micelles; the other complexes showed smaller variations. The O2-quenching rate constants decreased up to 1/8 of their original value in H2O (e.g., for [Ru(bpds)2(pta)]2− (6a) bound to CTAB micelles). Luminescence-lifetime experiments in H2O/D2O allowed the determination of the metal-complex fraction exposed to solvent after binding to surfactant micelles. For instance, such exposure was as low as 25% for pta complexes⋅CTAB aggregates. The different behaviors observed were rationalized in terms of the RuII complex structure, the electrostatic/hydrophobic interactions, and the probe environment.

Oxygen-sensitive layers for optical fibre devices

The spectroscopic features and photoreactivity with oxygen of a novel, highly lipophilic, luminescent metal complex Ru(5-odap)32+ (where 5-odap stands for 5-octadecanamide-1,10-phenanthroline), are reported and compared to those of the well-known tris(1,10-phenanthroline) analogue. An array of silicone membranes, containing Ru(5-odap)32+ or Ru(φ2p)32+ (where φ2p stands for 4,7-diphenyl-1,10-phenanthroline) as solid-supported luminescent indicators, have been fabricated. Their (non-linear) response to oxygen was evaluated with fibre-optics as a function of their adsorbent nature (silica gel, glass, reverse-phase silica, styrene/divinyl benzene copolymer, or none), surface coverage by the deposited metal complex, and loading of dyed support into the sensitive layer. The largest oxygen sensitivity (I0/I ca. 6 for a partial pressure of 130 Torr) is achieved with the highest amount of silica gel- or glass-supported Ru(φ2p)32+ and the highest membrane loading. Ru(5-odap)32+ dissolved directly into silicone yields a linear dose/response plot, but with a small slope (I0/I ca. 1.4 for a partial pressure of 720 Torr). These results are discussed in terms of dynamic surface quenching between the co-adsorbed indicator and oxygen molecules.

Environmental and Industrial Optosensing with Tailored Luminescent Ru(II) Polypyridyl Complexes

The sensitivity, specificity and versatility of optical methods for chemical determinations have turned spectroscopy into one of the most popular techniques for environmental analysis and process control [1, 2]. In most cases, however, the very same attractive features have led (so far) to expensive instrumentation and/or complex methods compared to, for instance, the well-established electrochemical sensors. Fibre-optic chemical sensors (also known as „optodes“) are bound to overcome such limitations provided they use cost-effective optoelectronics and prove to be specific, sensitive and robust enough to fulfill their analytical tasks in air, water and soil quality monitoring as well as in the industrial environment.

A clean, well-defined solid system for photosensitized 1O2 production measurements.

Generation of singlet molecular oxygen ((1)O(2)) by photosensitization with methylene blue (MB) supported in Nafion-Na films has been quantified by integration of the (1)O(2) emission decay at 1270 nm. The quantum yield of (1)O(2) production (Phi(Delta)) in the air-equilibrated solid phase is 0.24 +/- 0.03. Information on the (1)O(2) generation environment has been gained from complementary techniques such as UV-Vis absorption and emission spectroscopy, as well as MB fluorescence and triplet-triplet absorption decay. Results are compared with the (1)O(2) generation by MB in methanol solution (Phi(Delta) = 0.51) and in methanol-swollen Nafion films (Phi(Delta) = 0.49 +/- 0.06). Differences and similarities are discussed in terms of the factors that influence Phi(Delta) in solution and in the solid media. The optical and mechanical features of Nafion, ease of dye loading, compatibility with most solvents, homogeneity, reproducibility and stability of the photosensitizing material makes it a convenient reference for (1)O(2) generation quantum yield measurements in transparent (micro)heterogeneous and homogeneous media.

The Interplay of Indicator, Support and Analyte in Optical Sensor Layers

It has been recognized since the pioneering times of fiber-optic sensing development that the best indicator dye is worth nothing without a (polymer) support fitted to both the determinand species and the indicator itself. However, the task of selecting an organic or inorganic polymer for manufacturing a sensitive head among the myriad of materials available nowadays may seem daunting to the researcher or technologist. Moreover, if we also incorporate a biological recognition element to develop an ultrasensitive or specific biosensor, the multifaceted problem appears even more puzzling. This chapters aims to guide the reader through the current world of both organic and inorganic materials and their effect on (bio)chemical sensing. Selected examples illustrate the diversity of solid supports and composites and their effect on the indicator response, photostability, interaction with the analyte, stability of the different biological elements, and ease of preparation, among other factors, shedding some light on the complex interaction between the key components of chemical sensors and biosensors.

Photochemical Oxidation of Thioketones by Singlet Molecular Oxygen Revisited: Insights into Photoproducts, Kinetics, and Reaction Mechanism

Photosensitized oxidation of trimethyl[2.2.1]bicycloheptane thioketones by (1)O2 can yield more photoproducts than exclusively ketones and sulfines. Moreover, the ketone/sulfine ratio can be reversed when protic conditions and high thioketone concentrations are used, conversely to earlier results reporting ketones as the main photoproducts. A new mechanistic proposal for sulfine formation is suggested following intermolecular oxygen transfer from a peroxythiocarbonyl intermediate to a second thioketone molecule. Reaction quantum yields (10(-5)-10(-2)) depend on the reaction conditions and time. Sulfine production reaches a maximum at short irradiation times, whereas decomposition to the corresponding ketone is observed at long reaction times. When the thioketone substrate has a hydrogen atom at the α position a peroxyvinylsulfenic acid intermediate can be formed by proton transfer. Reaction of this intermediate with another thioketone molecule can yield more sulfine and its tautomeric vinylsulfenic acid, which dimerizes in situ to the thiosulfinate. The hydroperoxyl group of the peroxyvinylsulfenic acid can also rearrange to the α position, and by reaction with the starting thioketone, α-hydroxy thioketone and additional sulfine can be formed, while dehydration yields the α-oxo thioketone. In situ [2 + 2] and [4 + 2] self-cycloaddition of the α-oxo thioketone yields significant amounts of the corresponding adducts at prolonged irradiation times.

Fibre-optic chemical sensors: From molecular engineering to environmental analytical chemistry in the field

Publisher Summary This chapter discusses fiber-optic chemical sensors or optodes, which is an attractive alternative to current electrochemical or electronic devices in terms of monitoring stability, electrical hazards, size, target analytes, versatility, simplicity, ruggedness, and cost. To show full potential, dedicated optoelectronic instrumentation and tailor-made optical indicators must be developed. This chapter also presents a combined effort between industry and university to carry out an R&D project that spans from molecular design of novel luminescent Ru(II) polypyridyl dyes, to the probe engineering, fabrication, characterization, validation and in situ monitoring with optical devices based on waveguides and active sensing heads, capable of continuously monitoring relevant parameters in waters. Two examples of how the fiber-optic analysis of dissolved oxygen and carbon dioxide has been tackled by a suitable design of the indicator molecules are also discussed. Results on oxygen monitoring with optodes in the biological treatment pool of a wastewater sanitation plant are presented as well.

Rhodanine-based dyes absorbing in the entire visible spectrum

A series of new broad-absorbing dyes based on rhodanine derivatives conjugated with triarylamines using a fluorene backbone was synthesized. Spectroscopic and electrochemical studies, along with density functional theory (DFT) calculations, provided clear insight into the electronic and optical properties of the dyes, which efficiently absorb in the entire visible spectrum.