[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.
Journal of Colloid and Interface Science 02/2012; 368(1):191-6. · 3.17 Impact Factor
[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.
[Show abstract][Hide abstract] ABSTRACT: Hybrid gold nanoclusters exhibiting photoregulated release of nitric oxide are obtained by appropriate self-assembling of a suitable host, a photoactivable guest and Au nanoparticles. The excitation of the core, the shell or both components of the nanoclusters with visible light, together with their dark stability and water solubility, make these nanoarchitectures intriguing candidates to be tested in biomedical research studies.
New Journal of Chemistry 11/2010; 35(1):52. · 2.97 Impact Factor
[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.
New Journal of Chemistry 01/2010; · 2.97 Impact Factor
[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.
Annalen der Chemie und Pharmacie 12/2009; 2010(3):421 - 426. · 3.10 Impact Factor
[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.
Photochemical and Photobiological Sciences 11/2009; 8(11):1534-8. · 2.92 Impact Factor
[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.
Journal of Materials Chemistry 01/2009; 19(43). · 5.97 Impact Factor