[Show abstract][Hide abstract]ABSTRACT: This contribution reports the design, preparation, and characterization of nanostructured hybrid films of silver nanoparticles (AgNPs) and a tailored nitric oxide (NO) photodonor. They were achieved by exploiting effective interfacial interactions between an amino-terminated NO photodonor spread onto water surface and naked AgNPs dissolved in the water subphase. The morphology, the spectroscopic features, and the interaction between the two components in the floating films at the air/water interface were inspected by Brewster Angle Microscopy, UV-Vis reflection, and polarization-modulation infrared reflection-absorption spectroscopy. AgNPs and the NO photodonor were successfully transferred onto hydrophobized quartz substrates by horizontal lifting deposition and the resulting multilayer films were characterized by UV-Vis absorption spectroscopy and transmission electron microscopy, respectively. The results obtained showed the presence of both isolated AgNPs and assemblies of AgNPs having nanodimensional character in the films. The photochemical properties of the NO photodonor were well preserved in the hybrid multilayers. In fact, they were able to release NO under visible light excitation, as unambiguously demonstrated by the direct and in real-time monitoring of this transient species using an ultrasensitive electrode, and the transfer of the released NO to a protein such as myoglobin.
Full-text Article · Feb 2012 · Journal of Colloid and Interface Science
[Show abstract][Hide abstract]ABSTRACT: We have developed a supramolecular nanoassembly capable of inducing remarkable levels of cancer cell mortality through a bimodal action based on the simultaneous photogeneration of nitric oxide (NO) and singlet oxygen ((1)O(2)). This was achieved through the appropriate incorporation of an anionic porphyrin (as (1)O(2) photosensitizer) and of a tailored NO photodonor in different compartments of biocompatible nanoparticles based on cationic amphiphilic cyclodextrins. The combination of steady-state and time-resolved spectroscopic techniques showed the absence of significant intra- and interchromophoric interaction between the two photoactive centers embedded in the nanoparticles, with consequent preservation of their photodynamic properties. Photodelivery of NO and (1)O(2) from the nanoassembly on visible light excitation was unambiguously demonstrated by direct and real-time monitoring of these transient species through amperometric and time-resolved infrared luminescence measurements, respectively. The typical red fluorescence of the porphyrin units was essentially unaffected in the bichromophoric nanoassembly, allowing its localization in living cells. The convergence of the dual therapeutic action and the imaging capacities in one single structure makes this supramolecular architecture an appealing, multifunctional candidate for applications in biomedical research.
Article · Feb 2012 · Chemistry - A European Journal
[Show abstract][Hide abstract]ABSTRACT: Control by light: Reversible switching between closed and open conformations of a calixarene-based receptor was conveniently controlled, at the supramolecular level, exclusively through light inputs by exploiting the photoisomerization of a tailor-made azobenzene guest.
[Show abstract][Hide abstract]ABSTRACT: The inside cover picture shows a molecular conjugate incorporating a nitric oxide (NO) photodispenser and a masked fluorescent unit within the same molecular skeleton. This conjugate causes photoregulated NO release leading to remarkable mortality in cancer cells and the generation of a strongly fluorescent coproduct that serves as an optical reporter for the NO concentration released. For more details, see the Communication by Salvatore Sortino et al. p. 1551 ff.
[Show abstract][Hide abstract]ABSTRACT: Prison break! A nitric oxide (NO) photocage incorporating a masked fluorescent unit within the same molecular skeleton allows the photoregulated release of NO within a cell, leading to cytotoxicity. Concomitant release of a strongly fluorescent co-product serves as an optical reporter for intracellular NO release.
[Show abstract][Hide abstract]ABSTRACT: In this contribution, we report the synthesis and photophysical characterization of a molecular conjugate, in which C60 is covalently attached to a triquinoxaline-based cavitand through a pyrrolidine ring. Comparative experiments performed by using suitable model compounds demonstrate negligible interactions between the quinoxalinechromophores and the fullerene centre in the ground state. On the other hand, fluorescence emission and excitation spectra provide evidence for the occurrence of efficient photoinduced singlet–singlet energy transfer from the quinoxaline moiety to the C60 core. Laser flash photolysis experiments show that such an intramolecular process precludes the population of the lowest triplet state of the quinoxaline. By way of contrast, the lowest triplet state of the fullerene is effectively populated and is capable of sensitizing the formation of singlet oxygen in high yield, as unambiguously demonstrated by its typical infrared phosphorescence, detected by using time-resolved luminescence apparatus. The fullerene-quinoxaline conjugate exhibits photoinduced DNA-cleaving activity, as confirmed by preliminary photocleavage experiments carried out with a pBR322 supercoiled plasmid.
Full-text Article · Dec 2010 · New Journal of Chemistry
[Show abstract][Hide abstract]ABSTRACT: A novel molecular conjugate (1) that combines radical scavenging properties to light-regulated release of nitric oxide (NO) has been designed and synthesized by a straightforward procedure. This compound integrates a catecholic unit and a suitable NO photodonor, separated by an alkyl spacer, into the same molecular skeleton. The radical scavenging properties of 1 were evaluated by investigating its reactivity toward hydrogen abstraction by tert-butoxy radical by using laser flash photolysis techniques. The catecholic function of 1 is transparent to visible light, which, in contrast, is exclusively absorbed by the NO photodonor, resulting in the photocontrolled release of this radical species, monitored by an ultrasensitive NO electrode. A comparison of the value of the hydrogen abstraction rate constant and the amount of NO photoreleased with those of reference models demonstrates the retention of the single properties into the new molecular entity. This characteristic together with its water solubility make 1 a potential model system in the perspective of “multitarget” compounds for biomedical research studies.
Article · Jan 2010 · European Journal of Organic Chemistry
[Show abstract][Hide abstract]ABSTRACT: The cover picture shows a novel molecular conjugate that merges radical scavenging properties with the ability to release nitric oxide (NO) under the control of visible light stimuli. This compound consistes of a catecholic unit, as an antioxidant centre, that is joined to a nitroaniline derivative, as a suitable NO photodonor, through an alkyl spacer. Suitable choice of the two independent units allows preservation of their single properties once merged into the same molecular skeleton, offering the possibility of joining two functional molecules in a single compound without loss of their effectiveness. Details are discussed in the article by E. Vittorino and S. Sortino on p. 421 ff.
Article · Jan 2010 · European Journal of Organic Chemistry
[Show abstract][Hide abstract]ABSTRACT: We have designed and synthesized a novel photoactivable molecular conjugate integrating three basic components in its molecular skeleton: a DNA intercalator, a viologen moiety and a nitric oxide (NO) photodonor. This compound is soluble in aqueous solution and binds to double strand DNA with an association constant of 1.1 x 10(4) M(-1). The fluorescence of the intercalator unit is strongly quenched due to an intramolecular electron transfer involving the adjacent viologen moiety. Laser flash photolysis measurements provide direct evidence that, in the presence of DNA, this process is followed by a second electron transfer from DNA to the oxidized intercalator, leading to nucleobase oxidation. Also, the light absorbed by the NO photodonor results in the simultaneous release of NO nearby DNA as confirmed by the direct monitoring of this transient species through an ultrasensitive NO electrode. In this view, this conjugate represents an intriguing model system for photoactivable "dual-function" compounds for biomedical research.
Article · Nov 2009 · Photochemical and Photobiological Sciences
[Show abstract][Hide abstract]ABSTRACT: In this contribution we report the design, preparation and characterization of bichromophoric Langmuir–Schäfer multilayer films incorporating a tailored nitric oxide (NO) photodonor (1) and an ethylene-bridged zinc porphyrin dimer (2). They are achieved by exploiting the coordination of a pyridine appendage of the NO photodonor to the metal centers of the porphyrin units. Quite uniform floating films at the water–air interface are obtained spreading a mixture of 1:2 in the molar ratio 20:1 as confirmed by Brewster angle microscopy. The floating films are successfully transferred onto quartz slides by horizontal lifting deposition and the resulting hybrid multilayers are characterized by steady-state UV-Vis absorption, fluorescence and laser flash photolysis. The high ratio between the two chromogenic centers prevents the porphyrin aggregation, leading to photoresponsive bichromophoric films able to generate NO and singlet oxygen, 1O2 (1Δg), under the exclusive control of visible light stimuli.
Article · Oct 2009 · Journal of Materials Chemistry
[Show abstract][Hide abstract]ABSTRACT: A dual function photocage able to associate the generation of an anthrylmethyl carbocation to the release of NO, under the control of a low energy single wavelength light, was reported. The O-alkylation of cupferron (CP) was accomplished by designing and synthesizing compound anthrylmethyl. The results show that the compound is easily synthesized in one step and its irradiation with low energy light excitation in a mixture phosphate buffer leads to a satisfactory photodegradation with a quantum yield of 0.05. It is also found that the compound is stable to the release of NO in the dark and that light irradiation induces constant generation of NO after brief initiation period. A 355 nm laser excitation of a solution of anthracene in the presence of CP 0.06 originates the typical transient absorption of the anthraene radical cation characterized by its diagnostic absorption maxima at 710 and 420 nm.
Article · Jul 2009 · Chemistry - A European Journal
[Show abstract][Hide abstract]ABSTRACT: Cyclopropanation reactions of 6-deoxyhex-5-enopyranosides by methylene-zinc-iodide complex, dichlorocarbene, and rhodium ethoxycarbonyl complex addition afford optimum yields of the corresponding spirocyclopropanes. Surprisingly, a stereospecific spirocyclopropane derivative with the two halogens on the upper face of the 4-hydroxy substituent is obtained. To get more insight on the dichlorocarbene cyclopropanation process a computational study, based on DFT quantomechanic calculation was conducted.Graphical abstract
[Show abstract][Hide abstract]ABSTRACT: Reactions of the simplest thiocarbonyl ylide with a variety of appropriate alkenes bearing electron-withdrawing substituents afforded the corresponding tetrahydrothiophenes, which could be easily elaborated into hydroxy and hydroxymethyl derivatives and then coupled with nucleobases to produce different 4′-thionucleosides. Particularly, α- and β-anomers of 1-[3,4-bis(hydroxymethyl)tetrahydro-2-thienyl]-thymine, -cytosine, -uracil and -fluorouracil were prepared with dimethyl fumarate and maleate, while 1-[4-(hydroxymethyl)tetrahydro-2-thienyl]- and 1-[4-(hydroxymethyl)tetrahydro-3-thienyl]-thymine, -cytosine, -uracil and -fluorouracil were prepared with a chiral α,β-unsaturated amide. These processes, simple in the experimental conditions and large availability of the starting materials, affording moderate to good yields of 4′-thionucleosides, represent an optimum alternative to those, already known, based on sugars, which often have the drawbacks of a higher number of steps and lower yields.
[Show abstract][Hide abstract]ABSTRACT: 2,6-di-O-benzyl- (9), 2-O-benzyl-3,4-O-isopropylidene- (19), and 2-O-benzyl-6-O-m-chlorobenzoyl-L-arabino-hexos-5-ulose (20) have been prepared using 4'-deoxy-4'-eno- and 6'-deoxy-5'-eno lactose dimethyl acetal derivatives 7 and 14 as key intermediates. The synthesis of enol ethers 7 and 14 has been performed with good yields by base-promoted elimination of acetone or p-toluenesulfonic acid from 2',6'-di-O-benzyl-, and 6'-O-p-toluenesulfonyl-2,3:5,6:3',4'-tri-O-isopropylidenelactose dimethyl acetal, respectively. The epoxidation with MCPBA of 7 and 14 in methanol or dichloromethane furnishes C-5'-methoxy and C-5'-m-chlorobenzoyloxy derivatives, easily transformed with good yields into L-arabino 5-ketoaldohexoses 9, 19 and 20.