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Nitric oxide (NO) is a key signaling molecule in biological systems. New tools are required to therapeutically modulate NO levels with confined precision. This study explores the photoactivatable properties of an NO releasing compound (CPA), based on cupferron O-alkylated with an anthracene derivative. Upon light stimulation, CPA uncages two species: cupferron, which liberates NO, and an anthrylmethyl carbocation, which evolves into a fluorescent reporter. Proof-of-principle is demonstrated using one- and two-photon excitation (1PE and 2PE) in a cellular system (A431 cells). It was found that 1PE induces cell toxicity, while 2PE does not. Since 1PE using UV light is more likely to generate cellular photodamage, the cell toxicity observed using 1PE is most likely a combinatory effect of NO release and other UV-induced damage, which should be subject to further investigation. On the other hand, absence of phototoxicity using 2PE suggests that NO alone is not cytotoxic. This leads to the conclusion that the concept of 2PE photorelease of NO from CPA enable opportunities for biological studies of NO signaling with confined precision of NO release with minimal cytotoxicity.

In the search of innovative agents able to combat the antibiotic resistance phenomenon which is a serious threat for public health in the world, nitric oxide (NO) and singlet oxygen (1O2) radicals are very interesting "non-conventional" drugs. They elicit a significant broad spectrum toxicity against virus, bacteria, fungi, yeast, and protozoa by oxidation of cell components as proteins, lipids, and DNA. A growing interest there is for new compounds generating NO and 1O2 in a controlled fashion due to the high cytotoxicity, short half-life and diffusion in the cellular environment over short distances of these radicals. Light is a biofriendly stimulus that offers advantages in terms of precise spatiotemporal control and powerful trigger, it is does not affect physiological parameters such as temperature, pH, and ionic strength. Therefore, among the variety of NO and 1O2 generators, photochemical compounds are particularly appealing to confine the cytotoxic action in the area of interest sparing healthy cells. In this contribute, we exploited the calix[4]arene macrocycle to realize new nanoconstructs for photodisinfection and antibacterial phototherapy by using both a covalent and non-covalent approach. In the first case, multiple units of a NO photodonor have been clustered and spatially organized onto a polycationic calix[4]arene scaffold; in the second case multiple units of insoluble or scarcely water soluble NO and 1O2 photodonors have been entrapped into a polycationic calix[4]arene spontaneously self-assembling in micellar nanoaggregates. The calixarene-based nanoconstructs as nanocontainers and nanocarriers enhanced solubility and local concentration of the photodonors and as a nanoreactor increased the release of NO under the exclusive control of visible light inputs. The light-stimulated bactericidal effect was successfully tested on Gram positive and Gram negative bacteria.

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-Scha¨fer deposition. The resulting multilayers exhibit a good response to light excitation as proven by fluorescence emission, triplet- triplet absorption and singlet oxygen photogeneration.

The peroxidation of g-terpinene (TH) initiated by tert-butoxyl radicals has been investigated by means of nanosecond laser flash photolysis techniques in acetonitrile at room temperature. The absolute rate constants for the reactions implicated in the peroxidation process have been determined and the main short-lived intermediates, terpenyl and terpenylperoxyl radicals, have been detected. The rate constant for H-atom abstraction from TH by tert-butoxyl radicals, k3 , has been found to be 1.4x10^8 M-1 s-1 while the values for the self-quenching of T radicals, 2k4 , and the addition of O2 to T, k9 , are, respectively, 1.2x10^10M-1 s-1 and 1.3x10^9 M-1 s-1. The overall results strongly substantiate the peroxidation mechanism recently proposed by Foti and Ingold, J. Agric. Food Chem., 2003, 51, 2758, and provide a solid basis for a better understanding of the unusual antioxidant activity exhibited by this hydrocarbon.

Recently some interest was focused on the photobehavior of CD-drug inclusion complexes in relation to the problem of the biological photosensitization by drugs. This review is dedicated to the illustration of the mechanistic aspects of the photoprocesses occurring in some non steroidal anti-inflammatory drugs (NSAIDs), with photosensitising side effects, within CD cavities. It is shown how the photobehavior of the CD-drug associates can help to model the photoreactivity of the drugs in biological sites. The limitations for the use of CDs as protective systems for the clinical administration of photosensitising drugs is also evidenced.

Several in vitro and in vivo studies have suggested that carnosine can act as a scavenger of reactive oxygen species and intracellular proton buffer. On the other hand, carnosinase is a specific peptidase able to destroy the biological active dipeptide. To overcome this constraint, -cyclodextrin ( -CD) was functionalized with carnosine to give the following new compounds: 6A-[(3-{[(1S)-1-carboxy-2-(1H-imidazol-4-yl)ethyl]amino}-3- oxopropyl)amino]-6A-deoxy- -cyclodextrin (1), 6A-[( -alanyl-L-histidyl) amino]- -cyclodextrin (2), and (2AS,3AR)-3A-[(3-{[(1S)-1-carboxy-2-(1H- imidazol-4-yl)ethyl]amino}-3-oxopropyl)amino]-3A-deoxy- -cyclodextrin (3). Pulse-radiolysis investigation showed that the -CD derivatives 1-3 are excellent scavengers of OH. radicals. Their activity is not only due to the formation of the stable imidazole-centered radical, but also to the scavenger ability of the glucose moieties of the macrocycle. This effect is independent of the disposition of the imidazole ring. In fact, the quenching constant values are similar for the three compounds.