Controlled assembly of metal colloids on dye-doped silica particles to tune the photophysical properties of organic molecules.

The use of plasmonic nanomaterials is a challenging strategy to control radiation and radiation-induced processes at a nanometric scale. The localized surface plasmons of metal nanoparticles have been shown to affect the efficiency of a variety of radiative and non-radiative processes occurring in organic molecules. In this contribution, we present an overview of the results obtained through an original approach based on the hierarchical assembly of plasmonic gold colloids on silica templates, covalently doped with organic dyes. The detailed morphological characterization demonstrates the disposition of gold colloids on silica achieved through the tight control of the synthetic conditions. The studies carried out while gradually increasing the concentration of gold nanoparticles allow the detailed investigation of the effects of the progressive addition of plasmonic particles on the photophysical behaviour of organic molecules. In particular, the fluorescence behaviour of three dyes with different spectral properties, namely fluorescein, rhodamine B and 9-aminoacridine, are investigated in the presence of increasing concentrations of gold nanoparticles. In order to fix the distance between the dye and the gold nanoparticles, the dyes are anchored to silica nanoparticles, and the metal colloids are chemically adsorbed on the silica surface. The steady state and time-resolved data are analysed to evaluate the impact of plasmonic nanoparticles on the radiative and non-radiative processes of the dyes; the data provide evidence that the modulation of the fluorescence intensity (enhancement or quenching) can be achieved by changing the concentration of gold colloids. The plasmonic nanostructures can be employed to favour one deactivation process over the others. For example, we demonstrate that the photoinduced formation of reactive oxygen species (ROS) can be enhanced upon the plasmonic engineering of a photosensitizing agent (Protoporphyrin IX, PpIX). The Vis-excitation of silica-PpIX samples in the presence of gold nanoparticles results in a faster and more efficient photoinduced formation of ROS species either in solution or in a hydrogel. The ROS efficiency data and the fluorescence behaviour of PpIX in the presence of gold colloids suggest that the enhancement of the excitation field occurs through a plasmonic effect. For the application of the assembled hybrid materials, further advantages come from the development of photosensitizer-containing hydrogel films that are able to efficiently produce ROS upon visible excitation. Our preliminary results are herein reported and discussed.

A triplet-triplet annihilation based up-conversion process investigated in homogeneous solutions and oil-in-water microemulsions of a surfactant.

The triplet-triplet annihilation based up-conversion process, involving a platinum octaethyl-porphyrin (PtOEP) as a sensitizer and tetraphenyl-pyrene (TPPy) as an emitter, has been investigated in homogeneous solutions of toluene, bromobenzene and anisole, and oil-in-water microemulsions of the TX-100 surfactant, where toluene constitutes the non-polar phase. In homogeneous solutions, the highest up-conversion quantum yield (of the order of 20%) has been achieved in toluene, being the solvent that has the lowest viscosity among those explored. The up-conversion emission from the PtOEP-TPPy pair has been then investigated in a toluene based oil-in-water microemulsion at three different concentrations of the solutes, showing quantum yields up to the order of 1%, under the same irradiation conditions, but different deoxygenating procedures. The results herein reported might represent a good starting point for a future investigation in microheterogeneous systems. An optimization of the microemulsion composition, in terms of surfactant, co-surfactant and toluene concentrations, could allow us to increase the sensitizer and emitter concentrations and set up the best operative conditions to obtain even higher up-conversion efficiencies.

cDNA cloning and differential expression patterns of ascorbate peroxidase during post-harvest in Brassica rapa L.

Ascorbate is an antioxidant and a cofactor of many dioxygenases in plant and animal cell metabolism. A well-recognized enzyme consuming ascorbate is ascorbate peroxidase (APX), which catalyses the reduction of hydrogen peroxide to water with the simultaneous oxidation of ascorbate with a high specificity. The isolation and characterisation of new Apx cDNAs, could provide new insights about the physiological roles and regulation of these enzymes. In this work chloroplastic (Br-chlApx) and cytosolic (Br-cApx) isoform transcripts were isolated by RT-PCR in Brassica rapa and expression changes were analysed by semi-quantitative RT-PCR performed in different tissues (layer, stalk and florets) at different days (0, 4 and 14 day). The result showed that BrApx isoforms were differentially expressed and the Br-chlApx, in particular in the layer, had the highest expression level and remained unchanged also after 14 day after harvest. In addition, expression changes were compared with total BrAPX activity and the results showed that the activity decreased in all tissues at 14 day after harvest, independently of transcripts. Finally, additional solutes as the substrate of APX ascorbate and its oxidized form, dehydroascorbate, as well as α-tocopherol, the major vitamin E compound that prevents the propagation of lipid peroxidation in thylakoid membranes, were followed. The changes in the BrApx expression, BrAPX activity and metabolites can provide further evidence of the close relationships that exist between antioxidants which compensate for each other and suggest that there are multiple sites of reciprocal control.

Exhaled Carbon Monoxide Levels in Forty Resistant to Cessation Male Smokers after Six Months of Full Switch to Electronic Cigarettes (e-Cigs) or to A Tobacco Heating Systems (THS).

Cigarette smoke releases several toxic chemicals and carcinogens including carbon monoxide (CO). This study examined the levels of exhaled CO in smokers switching to electronic cigarettes (e-Cigs) or a tobacco heating system (THS) and their level of compliance six months after switching. On the basis of their own preferences, 40 male smokers unwilling or unable to stop smoking were switched to e-Cigs or THSs for six months (20 subjects in each group). Nicotine addiction and levels of carbon monoxide in the exhaled breath (eCO) were measured at baseline (the latter also at six months). The Shapiro Wilk test, graphical methods, Student T test or Mann-Whitney test were used to assess the normal distribution of variables and differences between the two groups after six months. The two groups showed no difference at baseline, but a significant higher addiction score in smokers choosing THS. E-Cig and THS showed significant reduced levels of eCO (both %COHb and COppm) after six months, which were within the range of non-smoker status. Reduced levels of %COHb did not significantly differ between the two groups, whilst the THS group had a significantly lower reduction in levels of COppm vs the e-Cig group (p < 0.05). Both e-Cigs and THSs are capable of significantly reducing eCO at least in the medium term, hence constituting a viable tobacco harm reduction approach in smokers who are unwilling or unable to stop smoking.

Fluorimetric Studies of a Transmembrane Protein and Its Interactions with Differently Functionalized Silver Nanoparticles.

Transmembrane proteins play important roles in intercellular signaling to regulate interactions among the adjacent cells and influence cell fate. The study of interactions between membrane proteins and nanomaterials is paramount for the design of nanomaterial-based therapies. In the present work, the fluorescence properties of the transmembrane receptor Notch2 have been investigated. In particular, the steady-state and time-resolved fluorescence methods have been used to characterize the emission of tryptophan residues of Notch2 and then this emission is used to monitor the effect of silver colloids on protein behavior. To this aim, silver colloids are prepared with two different methods to make sure that they bear hydrophilic (citrate ions, C-AgNPs) or hydrophobic (dodecanethiol molecules, D-AgNPs) capping agents. The preparation procedures are tightly controlled to obtain metal cores with similar size distributions (7.4 ± 2.5 and 5.0 ± 0.8 nm, respectively), thus, making the comparison of the results easier. The occurrence of strong interactions between Notch2 and D-AgNPs is suggested by the efficient and statistically relevant quenching of the stationary protein emission already at low nanoparticle (NP) concentrations (ca. 12% quenching with [D-AgNPs] = 0.6 nM). The quenching becomes even more pronounced (ca. 60%) when [D-AgNPs] is raised to 8.72 nM. On the other hand, the addition of increasing concentrations of C-AgNPs to Notch2 does not affect the protein fluorescence (intensity variations below 5%) indicating that negligible interactions are taking place. The fluorescence data, recorded in the presence of increasing concentrations of silver nanoparticles, are then analyzed through the Stern-Volmer equation and the sphere of action model to discuss the nature of interactions. The effect of D-AgNPs on the fluorescence decay times of Notch2 is also investigated and a decrease in the average decay time is observed (from 4.64 to 3.42 ns). The observed variations of the stationary and time-resolved fluorescence behavior of the protein are discussed in terms of static and collisional interactions. These results document that the capping shell is able to drive the protein-particle interactions, which likely have a hydrophobic nature.

The Influence of Modified Silica Nanomaterials on Adult Stem Cell Culture.

The preparation of tailored nanomaterials able to support cell growth and viability is mandatory for tissue engineering applications. In the present work, silica nanoparticles were prepared by a sol-gel procedure and were then functionalized by condensation of amino groups and by adsorption of silver nanoparticles. Transmission electron microscopy (TEM) imaging was used to establish the morphology and the average dimensions of about 130 nm, which were not affected by the functionalization. The three silica samples were deposited (1 mg/mL) on cover glasses, which were used as a substrate to culture adult human bone marrow-mesenchymal stem cells (hBM-MSCs) and human adipose-derived stem cells (hASCs). The good cell viability over the different silica surfaces was evaluated by monitoring the mitochondrial dehydrogenase activity. The analysis of the morphological parameters (aspect ratio, cell length, and nuclear shape Index) yielded information about the interactions of stem cells with the surface of three different nanoparticles. The data are discussed in terms of chemical properties of the surface of silica nanoparticles.

Successful Nicotine Intake in Medical Assisted Use of E-Cigarettes: A Pilot Study.

The electronic cigarette (e-cig) has gained popularity as an aid in smoking cessation programs mainly because it maintains the gestures and rituals of tobacco smoking. However, it has been shown in inexperienced e-cig users that ineffective nicotine delivery can cause tobacco craving that could be responsible for unsuccessful smoking reduction/cessation. Moreover, the incorrect use of an e-cig could also led to potential nicotine overdosage and intoxication. Medically assisted training on the proper use of an e-cig plus behavioral support for tobacco dependence could be a pivotal step in avoiding both issues. We performed an eight-month pilot study of adult smokers who started e-cig use after receiving a multi-component medically assisted training program with monitoring of nicotine intake as a biomarker of correct e-cig use. Participants were tested during follow-up for breath carbon monoxide (CO), plasma cotinine and trans-3'-hydroxycotinine, and number of tobacco cigarettes smoked. At the end of the first, fourth, and eighth month of follow-up, 91.1, 73.5, and 76.5% of participants respectively were e-cig users ('only e-cig' and 'dual users'). They showed no significant variation in plasma cotinine and trans-3'-hydroxycotinine with respect to the start of the study when they smoked only tobacco cigarettes, but a significant reduction in breath CO. The proposed medically assisted training program of e-cig use led to a successful nicotine intake, lack of typical cigarette craving and overdosage symptoms and a significant decrease in the biomarker of cigarette combustion products.

Salt-induced accumulation of glycine betaine is inhibited by high light in durum wheat.

In this study, we determined the effects of both salinity and high light on the metabolism of durum wheat (Triticum durum Desf. cv. Ofanto) seedlings, with a special emphasis on the potential role of glycine betaine in their protection. Unexpectedly, it appears that high light treatment inhibits the synthesis of glycine betaine, even in the presence of salt stress. Additional solutes such as sugars and especially amino acids could partially compensate for the decrease in its synthesis upon exposure to high light levels. In particular, tyrosine content was strongly increased by high light, this effect being enhanced by salt treatment. Interestingly, a large range of well-known detoxifying molecules were also not induced by salt treatment in high light conditions. Taken together, our results question the role of glycine betaine in salinity tolerance under light conditions close to those encountered by durum wheat seedlings in their natural environment and suggest the importance of other mechanisms, such as the accumulation of minor amino acids.