Synthesis and multidisciplinary characterization of polyelectrolyte multilayer-coated nanogold with improved stability toward aggregation

An interesting nanodrug delivery system is polyelectrolyte multilayer-coated nanogold. For better understanding of the binding of polycations or the counter-indicative deposition of polyanions on the citrate-stabilized gold nanoparticles, we used a surface-enhanced Raman spectroscopy to characterize the orientation of the polyions towards the gold surface. It was found that poly-allylamine replaces citrate molecules while the polyanion, poly-styrene sulfonate, intercalates in the citrate shell. One of the major obstacles for polyelectrolyte-coated nanogold is its tendency to agglomerate in the presence of high ion concentration as present, e.g., in blood. A novel encapsulation protocol for polyelectrolyte multilayer coating of gold nanoparticles was developed to successfully overcome this drawback. Moreover, electrostatic functionalization of the polyelectrolyte shell with a model target molecule for cancer, folic acid, induced a significant increase in the particle uptake in folate-receptor over-expressing breast cancer cell lines, VP 229 and MDA MB 231, compared to non-targeted particles or cells (non-activated macrophages) not expressing the folate receptor.     

Synthesis and photophysical properties of novel succinimidyl benzazole derivatives, evaluated by Candida albicans ATCC 10231 fluorescent staining

New fluorescent succinimidyl benzazole derivatives were synthesised and successfully used to stain Candida albicans ATCC 10231 cells. The dyes were characterised by means of infrared, ¹³C and ¹H NMR spectroscopies and elemental analysis. UV-Vis and steady-state fluorescence in solution were also applied to characterise their photophysical behaviour. The novel dyes were fluorescent in the yellow-green region by a phototautomerism in the excited state (ESIPT) with a large Stokes shift (9065-10962 cm⁻¹). Dual fluorescence could also be observed depending on the solvent polarity. The present dyes were used as new probes by means of culture methodology or direct staining to study the micromorphology of Candida albicans.     

A tri-block copolymer templated synthesis of gold nanostructures

Stable ultra-small gold nanoparticles have been synthesized in aqueous phase by using a tri-block copolymer (BMB) as a templating agent consisting of two PEG-methylacrylate chains (B blocks) anchored to a poly(methacrylic) moiety containing a trithiocarbonate unit (M block). The effect of the BMB/Au molar ratios on the final particle size, shape and monodispersity has been investigated. The synthesized nanosols have been characterized by means of Visible Absorption, Small Angle X-ray Scattering (SAXS), and Transmission Electron Microscopy (TEM). Results clearly indicate that the polymer plays a key role in determining the size and shape of gold particles, from fractal-like structures to monodisperse spherical particles with a mean diameter of about 3 nm. The aggregation behavior of these nanostructures has been characterized both in solution (SAXS) as well as on mica substrate (AFM) and has been proven to be driven by the polymer to gold concentration ratio.     

Geographical Discrimination of Bell Pepper (Capsicum annuum) Spices by (HS)-SPME/GC-MS Aroma Profiling and Chemometrics

Dried and ground red pepper is a spice used as seasoning in various traditional dishes all over the world; nevertheless, the pedoclimatic conditions of the diverse cultivation areas provide different chemical characteristics, and, consequently, diverse organoleptic properties to this product. In the present study, the volatile profiles of 96 samples of two different ground bell peppers harvested in diverse Italian geographical areas, Altino (Abruzzo) and Senise (Lucania), and a commercial sweet paprika, have been studied by means of headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). The investigation of their volatile profile has led to the identification of 59 analytes. Eventually, a discriminant classifier, Partial Least Squares Discriminant Analysis (PLS-DA), was exploited to discriminate samples according to their geographical origin. The model provided very accurate results in external validation; in fact, it correctly classified all the 30 test samples, achieving 100% correct classification (on the validation set). Furthermore, in order to understand which volatiles contribute the most at differentiating the bell peppers from the different origins, a variable selection approach, Variable Importance in Projection (VIP), was used. This strategy led to the selection of sixteen diverse compounds which characterize the different bell pepper spices.     

In Silico Insights into the Mechanism of Action of Epoxy-α-Lapachone and Epoxymethyl-Lawsone in Leishmania spp.

Epoxy-α-lapachone (Lap) and Epoxymethyl-lawsone (Law) are oxiranes derived from Lapachol and have been shown to be promising drugs for Leishmaniases treatment. Although, it is known the action spectrum of both compounds affect the Leishmania spp. multiplication, there are gaps in the molecular binding details of target enzymes related to the parasite’s physiology. Molecular docking assays simulations were performed using DockThor server to predict the preferred orientation of both compounds to form stable complexes with key enzymes of metabolic pathway, electron transport chain, and lipids metabolism of Leishmania spp. This study showed the hit rates of both compounds interacting with lanosterol C-14 demethylase (−8.4 kcal/mol to −7.4 kcal/mol), cytochrome c (−10.2 kcal/mol to −8.8 kcal/mol), and glyceraldehyde-3-phosphate dehydrogenase (−8.5 kcal/mol to −7.5 kcal/mol) according to Leishmania spp. and assessed compounds. The set of molecular evidence reinforces the potential of both compounds as multi-target drugs for interrupt the network interactions between parasite enzymes, which can lead to a better efficacy of drugs for the treatment of leishmaniases.     

Immobilization and nanoscale film structure of bacterial reaction centers on gold

Photosynthetic bacterial reaction centers (BRC) have shown great potential for bioengineering applications. In the present work we demonstrate their preferentially oriented immobilization on top of a mercaptopropionic acid (MPA) self assembled monolayer (SAM) formed on gold screen printed electrodes (Au-SPE). The AFM of the self assembled biofilm reveals formation of nanohole features with the depths of 2.2–2.5 nm, consistent with the thickness of the BRC (~ 3 nm). Thus, BRCs organize into a sub-monolayer film on top of the MPA SAM layer. The square-wave voltammogram of the BRC films exhibits features due to the redox reactions for the bacteriochlorophyll dimer (the strongest), bacteriopheophytin, and the quinones (weak), indicating that the BRCs are more likely immobilized with the dimer side towards the electrode surface. Non-saturating illumination of the BRC film at open circuit conditions leads to a sharp spike of negative current which could be due to the electron acceptance by the oxidized dimer.     

Red antenna states of photosystem I from cyanobacteria Synechocystis PCC 6803 and Thermosynechococcus elongatus: single-complex spectroscopy and spectral hole-burning study

Hole-burning and single photosynthetic complex spectroscopy were used to study the excitonic structure and excitation energy-transfer processes of cyanobacterial trimeric Photosystem I (PS I) complexes from Synechocystis PCC 6803 and Thermosynechococcus elongatus at low temperatures. It was shown that individual PS I complexes of Synechocystis PCC 6803 (which have two red antenna states, i.e., C706 and C714) reveal only a broad structureless fluorescence band with a maximum near 720 nm, indicating strong electron-phonon coupling for the lowest energy C714 red state. The absence of zero-phonon lines (ZPLs) belonging to the C706 red state in the emission spectra of individual PS I complexes from Synechocystis PCC 6803 suggests that the C706 and C714 red antenna states of Synechocystis PCC 6803 are connected by efficient energy transfer with a characteristic transfer time of approximately 5 ps. This finding is in agreement with spectral hole-burning data obtained for bulk samples of Synechocystis PCC 6803. The importance of comparing the results of ensemble (spectral hole burning) and single-complex measurements was demonstrated. The presence of narrow ZPLs near 710 nm in addition to the broad fluorescence band at approximately 730 nm in Thermosynechococcus elongatus (Jelezko et al. J. Phys. Chem. B 2000, 104, 8093-8096) has been confirmed. We also demonstrate that high-quality samples obtained by dissolving crystals of PS I of Thermosynechococcus elongatus exhibit stronger absorption in the red antenna region than any samples studied so far by us and other groups.     

Optical and electrochemical properties of poly(o-toluidine) multiwalled carbon nanotubes composite Langmuir-Schaefer films

Conducting poly(o-toluidine) (POT) with multiwalled carbon nanotubes (MWNTs) nanocomposite (POT-MWNTs) was synthesized by oxidative polymerization. Chloroform solutions of the material were used for the optical characterizations by means of UV-visible spectroscopy and for the fabrication of Langmuir-Schaefer (LS) films. LS films were fabricated at the air-liquid interface by using 0.1 M HCl aqueous solution as the subphase to study the electrochemical properties of the nanocomposite by means of cyclic voltammetry and photoelectrochemical techniques. The optical characterizations gave proof that the presence of MWNTs inside the polymeric matrix produced no change in the (pi-pi*) transition of POT structure, indicating that the polymeric chains were simply wrapped around and not doped by MWNTs. The electrochemical investigations highlighted significant changes in the redox properties of POT-MWNTs LS films with respect to pure POT. The cyclic voltammetric study also revealed high electrochemical stability, confirmed by the estimation of the diffusion coefficient and the photoelectrochemical response of the nanocomposite LS films. This characteristic turned out to be more evident than that obtained in our earlier studied poly(o-anisidine)-MWNTs (POAS-MWNTs) system.     

The effect of irradiation in the preservation of pink pepper (Schinus terebinthifolius Raddi)

Pink peppers, also known as “pimenta-rosa” and “poivre rose”, are the fruit of Schinus terebinthifolius Raddi, a species of pepper cultivated in Brazil, and have great potential for the exploration of uses. In efforts to lengthen the shelf life of this pepper, the purpose of this study was to evaluate the effect of different doses of radiation on its physical composition and color. The pink pepper samples were irradiated with doses of 0, 0.2, 0.4, 0.8 and 1.6 kGy, and the moisture, ash and lipid contents, pH and color were analyzed. The moisture content, lipid content and pH analysis indicated effects due to the irradiation (p>0.05) in which the higher doses resulted in decreases in the attribute. In contrast, there were no significant differences for the ash analysis (p<0.05) among the studied doses. The color of the pink peppers were affected by the irradiation: the parameters a^? and b^? were the most affected by the intermediate doses (0.2 and 0.8 kGy), which induced their elevation, enhancing the reddish and yellowish colors. Based on the presented data, irradiation is as an alternative preservation process for pink peppers.