Chlorophyll fluorescence in sentinel plants for the surveillance of chemical risk.

This research aimed to develop natural plant systems to serve as biological sentinels for the detection of organophosphate pesticides in the environment. The working hypothesis was that the presence of the pesticide in the environment caused changes in the content of pigments and in the photosynthetic functioning of the plant, which could be evaluated non-destructively through the analysis of reflected light and emitted fluorescence. The objective of the research was to furnish in vivo indicators derived from spectroscopic parameters, serving as early alert signals for the presence of organophosphates in the environment. In this context, the effects of two pesticides, Chlorpyrifos and Dimethoate, on the spectroscopic properties of aquatic plants (Vallisneria nana and Spathyfillum wallisii) were studied. Chlorophyll-a variable fluorescence allowed monitoring both pesticides' presence before any damage was observed at the naked eye, with the analysis of the fast transient (OJIP curve) proving more responsive than Kautsky kinetics, steady-state fluorescence, or reflectance measurements. Pesticides produced a decrease in the maximum quantum yield of PSII photochemistry, in the proportion of PSII photochemical deexcitation relative to PSII non photochemical decay and in the probability that trapped excitons moved electrons into the photosynthetic transport chain beyond QA-. Additionally, an increase in the proportion of absorbed energy being dissipated as heat rather than being utilized in the photosynthetic process, was notorious. The pesticides induced a higher deactivation of chlorophyll excited states by photophysical pathways (including fluorescence) with a decrease in the quantum yields of photosystem II and heat dissipation by non-photochemical quenching. The investigated aquatic plants served as sentinels for the presence of pesticides in the environment, with the alert signal starting within the first milliseconds of electronic transport in the photosynthetic chain. Organophosphates damage animals' central nervous systems similarly to certain compounds found in chemical weapons, thus raising the possibility that sentinel plants could potentially signal the presence of such weapons.

Improved photosynthetic performance induced by Fe3O4 nanoparticles.

Interaction between 11 nm-sized magnetite nanoparticles and Cichorium intybus plants was studied in this work. In particular, the effect of these nanoparticles on the photosynthesis electron chain was carefully analysed. Magnetite nanoparticles were synthesised and physically characterised by Transmission electron microscopy (TEM), Scanning electron microscopy (SEM)), Energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), Magnetic hysteresis cycles and UV-visible spectroscopy. Suspensions of the obtained magnetite nanoparticles with different concentrations (10-1000 ppm) were sprayed over chicory leaves and their photosynthetic activity was evaluated using chlorophyll fluorescence techniques. The study was complemented with the determination of pigment concentration and spectral reflectance indices. The whole set of results was compared to those obtained for control (non-treated) plants. Magnetite nanoparticles caused an increment in the content of Chlorophyll a (up to 36%) and Chlorophyll b (up to 41%). The ratio Chlorophyll/ Carotenoids significantly increased (up to 29%) and the quotient Chlorophyll a/b remained relatively constant, except for a sharp increase (19%) at 100 ppm. The reflectance index that best manifested the improvement in chlorophyll content was the modified Normalised Difference Vegetation Index (mNDI), with a maximum increase of about 35%. Electronic transport fluxes were favoured and the photosynthetic parameters derived from Kautsky's kinetics were improved. An optimal concentration of nanoparticles (100 ppm) for the most beneficial effects on photosynthesis was identified. For this dose, the probability by which a trapped electron in PSII was transferred up to PSI acceptors (ΦRE0) was doubled and the parameter that quantifies the energy conservation of photons absorbed by PSII up to the reduction of PSI acceptors ([Formula: see text]), augmented five times. The fraction of absorbed energy used for photosynthesis increased to 86% and the energy lost as heat by the non-photochemical quenching mechanism was reduced to 31%. Beyond 100 ppm, photosynthetic parameters declined but remained above the values of the control.

An ion imprinted magnetic organosilica nanocomposite for the selective determination of traces of Cd(II) in a minicolumn flow-through preconcentration system coupled with graphite furnace atomic absorption spectroscopy.

In this paper we present the determination of ultratraces of cadmium ions in water by means of a minicolumn (MC) flow-through preconcentration system coupled with graphite furnace atomic absorption spectrometry. The core of the system is a lab-made ion imprinted magnetic organosilica nanocomposite which is employed as filler of the MC for the selective retention of the analyte. In this case superparamagnetic magnetite nanoparticles were coated with an amine-functionalized shell and ion imprinted with Cd(II) by a simple sol-gel co-condensation method. The setup was completed with the inclusion of a magnet fixed around the packed MC. This assembly - which is studied with an MII material for the first time here - allowed a homogeneous distribution of the solid on the walls of the MC, leaving a hole in the center and enabling the absence of material bleeding or obstructions to the free movement of fluids. Ion imprinted (MII) and non-imprinted (MNI) materials were studied for comparison purposes. Both were characterized and compared by DRX, FTIR, and SEM and their magnetic behavior by magnetization curves. Batch experiments showed an equilibration time of less than 10 minutes and a maximum adsorption pH of around 7 for both solids. The maximum capacity for MII was greater than that of MNI (200 mg g-1 and 30 mg g-1 respectively) and thus, the former was chosen for analytical purposes. Under MC dynamic conditions, sample and elution flow rates, volumes of the sample and eluant, and type and concentration of the most suitable eluant have been thoroughly investigated and optimized. Under the optimal experimental conditions, the MII filler showed a preconcentration factor of 200, a limit of detection of 0.64 ng L-1, a linear range of 2.5-100 ng L-1, RSD% of 1.9 (n = 6; 10 ng L-1) and a lifetime of more than 800 cycles of concentration-elution with no loss of sensitivity or need for refilling. The effect of potentially interfering ions on the percent recovery of cadmium was also studied. The proposed method was successfully applied to the determination of traces of Cd(II) in osmosis and tap water with recoveries of 98.0-101.3%. A comparison with similar methods is also provided.

Reactivity of inorganic sulfide species towards a pentacoordinated heme model system.

The reactivity of inorganic sulfide towards ferric bis(N-acetyl)- microperoxidase 11 in sodium dodecyl sulfate has been explored by means of visible absorption and resonance Raman spectroscopies. The reaction has been previously studied in buffered solutions at neutral pH and in the presence of excess sulfide, revealing the formation of a moderately stable hexacoordinated low spin ferric sulfide complex that yields the ferrous form in the hour's timescale. In the surfactant solution, instead, the ferrous form is rapidly formed. The spectroscopic characterization of the heme structure in the surfactant milieu revealed the stabilization of a major ferric mono-histidyl high spin heme, which may be ascribed to out of plane distortions prompting the detachment of the axially ligated water molecule, thus leading to a differential reactivity. The ferric bis(N-acetyl)- microperoxidase 11 in sodium dodecyl sulfate provides a model for pentacoordinated heme platforms with an imidazole-based ligand.

Effects of gold nanoparticles on the photophysical and photosynthetic parameters of leaves and chloroplasts.

Effects of gold nanoparticles (average diameter: 10-14 nm) on leaves and chloroplasts have been studied. Gold nanoparticles (AuNPs) quenched significantly chlorophyll fluorescence when introduced both in intact leaves and isolated chloroplasts. Additionally, the fluorescence spectra corrected for light re-absorption processes showed a net decrease in the fluorescence ratio calculated as the quotient between the maximum fluorescence at 680 and 735 nm. This fact gave evidence for a reduction in the fluorescence emission of the PSII relative to that of the PSI. Strikingly, the photosynthetic parameters derived from the analysis of the slow phase of Kautsky's kinetics, the rate of oxygen evolution and the rate of photo-reduction of 2,6-dichlorophenolindophenol were increased in the presence of AuNPs indicating an apparent greater photosynthetic capacity. The observed results were consistent with an electron transfer process from the excited PSII, which was thermodynamically possible, and which competed with both the electron transport process that initiated photosynthesis and the deactivation of the excited PSII by fluorescence emission. Additionally, it is here explained, in terms of a completely rational kinetic scheme and their corresponding algebraic expressions, why the photosynthetic parameters and the variable and non-variable fluorescence of chlorophyll are modified in a photosynthetic tissue containing gold nanoparticles.

N-acetylcysteine reduces markers of differentiation in 3T3-L1 adipocytes.

Oxidative stress plays a critical role in the pathogenesis of diabetes, hypertension and atherosclerosis. Some authors reported that fat accumulation correlates to systemic oxidative stress in humans and mice, but the relationship of lipid production and oxidative metabolism is still unclear. In our laboratory we used 3T3-L1 preadipocytes, which are able to differentiate into mature adipocytes and accumulate lipids, as obesity model. We showed that intracellular reactive oxygen species (ROS) and antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities increased in parallel with fat accumulation. Meanwhile N-acetylcysteine (NAC), a well known antioxidant and Glutathione (GSH) precursor, inhibited ROS levels as well as fat accumulation in a concentration-dependent manner. NAC also inhibited both adipogenic transcription factors CCAAT/enhancer binding protein beta (C/EBP ß) and peroxisomal proliferator activated receptor gamma (PPAR γ) expression; we suggested that intracellular GSH content could be responsible for these effects.

Photophysics of zinc (II) phthalocyanine polymer and gel formulation.

The photophysical properties of lipophilic phthalocyanines encapsulated into a polymer and two different gels were studied in order to predict their photosensitizing efficacy in vivo. Photophysical techniques for solid phase were adapted for light dispersing samples. Gel formulation of two tetrasubstituted phthalocyanines, tetra-t-butylphthalocyaninato zinc(II) (1), tetrakis(1,1-dimethyl-2-phthalimido)ethylphtalocyaninatozinc(II) (2) and two octasubstituted phthalocyanines, 2,3,9,10,16,17,23,24-octakis(decyloxy)phthalocyaninatozinc(II) (3) and 2,3,9,10,16,17,23,24-octakis[(N,N-dimethylamino)ethylsulfanyl]phthalocyaninatozinc(II) (4) were investigated for their possible use in photodynamic therapy for topical purposes. Supporting the fact that gel formulation improves the photophysical properties of phthalocyanines, singlet molecular oxygen quantum yield (Phi(Delta)) values for 1-4 zinc(II) phthalocyaninates in Lutrol F 127-Cremophor RH 40 were 0.60, 0.60, 0.20 and 0.26, respectively. Permeation studies showed that no release of phthalocyanines occurs, thus indicating there should be no risk of generalized skin photosensitivity in areas other than the dye-deposition site.

Detection and discrimination of phenol and primary alcohols in water using electronic noses.

Electronic nose methodology was used for discriminating between samples of n-primary alcohols and phenol in water. An electronic nose device developed at our laboratory was applied to detect the vapors from the samples. The device consists of 10 nonspecific gas sensors based on tin-dioxide, whose electrical conductivity change when exposed to the vapors. The whole set of responses constitutes a fingerprint associated with the sample for the particular array of sensors. Using this method, we could differentiate among n-primary alcohols, pure phenol, and aqueous dilutions of phenol. Dilutions of primary alcohols and phenol of 1, 3, 5, and 10% (v/v) were assayed. The fingerprints of the dilutions are similar to that of the respective pure (not diluted) alcohol, but with lower signal intensities. Principal component analysis and cluster analysis were performed in order to explore the feasibility of discriminating among the samples. Dilutions of phenol were successfully discriminated from those of primary alcohols. Discrimination of n-octanol and n-decanol from the other alcohols, including phenol, was also achieved. The results suggest that it is possible to discriminate among dilutions of phenol in water and to give an approximate gross estimation of phenol concentration in water.