Hybrid polymer aerogels containing porphyrins as catalysts for efficient photodegradation of pharmaceuticals in water.

Polymer aerogels of poly(acrylic acid)/poly(vinyl alcohol) (labeled as CPA) were prepared and tested as support materials for different cationic porphyrin organocatalysts (denoted as TMPyP, TMPyPZn, or TMPyPMn). The hybrid aerogels were characterized by various techniques, while their catalytic activity was investigated towards the photodegradation of amoxicillin (AMX), caffeine (CAF), and naproxen (NPX) under artificial visible light. Photodegradation experiments revealed that the CPA-TMPyPMn aerogel shows superior catalytic potential when compared to the others aerogels or the "free" TMPyPMn porphyrin. All pharmaceuticals were quickly degraded (before 60 min) and high COD removal rates (greater than95%) were achieved at pH 7.0 and room temperature. The CG-MS data confirm the complete degradation of all tested pharmaceuticals catalyzed by CPA-TMPyPMn. Recycling experiments revealed that this hybrid aerogel keeps its photocatalytic efficiency for at least 15 reuse runs. In short, this original photocatalytic system is promising to mediate the removal of pharmaceutical contaminants from the aqueous medium.

Detection of singlet oxygen by EPR: The instability of the nitroxyl radicals.

The use of spin traps and redox probes coupled with electron paramagnetic resonance (EPR) is a method frequently applied in the evaluation of the efficiency of photosensitizers and photocatalysts in phototherapeutic and photocatalytic processes that involve reactive oxygen species. In this way, the method helps to clarify the mechanism behind photo-induced reactions. Hydroxy-TEMP is a very specific redox probe for selectively identifying and quantifying singlet oxygen (1O2). In this work, the kinetics of radical generated by the oxidation products of the Hydroxy-TEMP redox probe was analyzed from EPR spectra in aqueous solutions of several water-soluble porphyrins ([H2T4MPyP](OTs)4, Na4[H2T4SPP], [H2T2MPyP](OTs)4, [ZnT4MyPyP](OTs)4, [MnT4MyPyP](OTs)5, H2T4CPP, and [H2T4TriMAPP](OTs)4) under white light illumination. Different factors such as the concentration of the redox probe, pH of the medium, and photostability of the porphyrins were evaluated. A systematic study was carried out to reveal the factors associated with stable radical degradation (TEMPOL) by illumination in the visible spectral region in systems containing photosensitizer (porphyrin) and redox probe (Hydroxy-TEMP). With the aid of EPR and gas chromatography coupled with mass spectroscopy (GC-MS) techniques, the mechanism of the radical degradation and the photobleaching of porphyrins were investigated. After successive interactions with the porphyrin in its excited state, in alkaline aqueous solution (pH > 10), the free radical TEMPOL is transformed into TEMPONE until the final diamagnetic product Phorone. A protocol was elaborated to identify and quantify the generation of 1O2 by Hydroxy-TEMP reliably, to avoid possible errors in the interpretation of efficiency of photosensitizers.

Photophysical, photodynamical, redox properties and BSA interactions of novel isomeric tetracationic peripheral palladium(II)-bipyridyl porphyrins.

New isomeric tetra-cationic porphyrins containing peripheral [Pd(bpy)Cl]+ units attached to pyridyl substituents were synthesized and fully characterized. The porphyrins present an intense Soret band located in the blue spectral region and an additional four weaker red-shifted Q bands in the visible spectral region (about 500-700 nm). The obtained Strickler-Berg parameters indicate fully spin and symmetry allowed transitions for all the observed absorption bands. Both porphyrins present two fluorescence emission bands, an intense one located around 650 nm and an additional weak red-shifted emission at ∼710 nm. Fluorescence decay time profiles were obtained showing bi-exponential decay. The interaction of the porphyrins with bovine serum albumin (BSA) was studied in detail by a fluorescence quenching method and molecular docking analysis. In addition, the photodynamical activity of the porphyrins in the photooxidation of BSA was determined and compared with the light-induced formation of reactive oxygen species (ROS) by electron paramagnetic resonance (EPR) allied with the spin trapping method. The results show that the Pd(ii)-bypyridyl tetra-cationic porphyrins are promising candidates for the photooxidation of biological substrates used in photodynamic therapy (PDT).

Efficient antibacterial nanosponges based on ZnO nanoparticles and doxycycline.

Bacterial soft rot is responsible for the loss of about 25% of worldwide production in vegetables and fruits. Efforts have been made to develop an effective nanosponge with the capacity to load and release antibacterial drugs to protect plants. Based on the potential of the ZnO nanoparticles (ZnO-NPs) to achieve this goal, this study synthesized NP via the sol-gel and hydrothermal methods by controlling native defects, such as oxygen vacancies, using thermal treatments and reduced atmospheres. To characterize the ZnO NPs, X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), optical spectroscopy, electron paramagnetic resonance (EPR), Zeta Potential measurements and surface area with the Brunauer-Emmett-Teller (BET) method were used. The photophysical and photochemical properties via spin trapping method aligned with EPR using UVA light showed a greater formation of electron-hole pairs and hydroxyl radicals for the reduced ZnO NPs when compared with the oxidized ones. Additionally, we found that reduced ZnO-NPs have high effectively against Escherichia coli, Erwinia carotovora and Pantoea sp. bacteria using the photocatalytic effect in the UV range. Moreover, ZnO-NPs loaded with DOX release profile enables the release of DOX within 46days, where 25% was released during the first 10h followed by a second delivery phase with an interesting short-term efficacy (<1day) against E. carotovora and Pantoea sp. Bacteria. For the first time, it was demonstrated that ZnO-NPs and ZnO-NPs loaded with DOX have efficient UV photocatalytic activities against bacterial soft rot infections.

Hybrid systems based on gold nanostructures and porphyrins as promising photosensitizers for photodynamic therapy.

Gold nanostructures of two different shapes (spheres and rods) were synthesized to form a colloidal hybrid system with 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin tosylate salt (H2TM4PyP(OTs)4) (POR) for applications in photodynamic therapy (PDT) using light in the visible spectral range. Electron paramagnetic resonance (EPR) experiments in combination with spin trapping were used for the detection of reactive oxygen species (ROS) and evaluation of the efficiency of these novel hybrid systems as photosensitizers. It is shown that the hybrid system consisting of gold nanorods (AuNR) and porphyrin (POR) is by far more efficient than its isolated components. This enhanced efficiency is explained by a synergetic effect between the AuNR and the porphyrin, wherein a rapid energy transfer from the former to the latter produces a large amount of singlet oxygen followed by its conversion into hydroxyl radicals. The mechanism was investigated using different spin traps and different ROS inhibitors. On the other hand, spherical gold nanoparticles (AuNP) do not show this synergetic effect. The synergetic effect for gold nanorods/POR hybrid is attributed to a larger field enhancement close to the gold nanorod surface in addition to the electrostatic attraction between the components of the hybrid system.

Unravelling the mechanisms of reactive oxygen species formation in nanohybrid systems of porphyrins and enriched (6,5) single-walled carbon nanotubes for photosensitization.

Nanohybrids of enriched (6,5) single-walled semiconducting carbon nanotubes (E-SWCNTs) and porphyrin can be used synergistically as photodynamic therapy (PDT) agents. The efficiency of different porphyrins within the nanohybrids was investigated and compared with results obtained from porphyrins in previous studies. Reactive oxygen species singlet oxygen (1)O2 and for the first time hydroxyl radical ˙OH generation by the nanohybrids under illumination were detected by electron paramagnetic resonance using spin trapping molecules TEMP and PBN. Based on the analysis, we improve the modelling of charge transport within the nanohybrids, which is also detected by Raman scattering. It is shown that the 5,10,15,20-tetrakis(4-trimethylammoniumphenyl)porphyrin [H2TTMAPP(OTs)4] and E-SWCNT form very efficient nanohybrids for PDT applications in the visible spectral range.

Resveratrol treatment has neuroprotective effects and prevents cognitive impairment after chronic cerebral hypoperfusion.

OBJECTIVE: The present study investigated the neuroprotective effects of Resveratrol (RSV) in rats submitted to chronic cerebral hypoperfusion (CCH) in a model of permanent two-vessel occlusion (2VO). METHODS: For this purpose, adult Wistar rats received daily i.p. injections of RSV (20 mg/kg) for 7 days, starting 1 hour after the 2VO procedure. Behavioral testing was run between the 30th and 45th days after the 2VO surgery. Accordingly, spatial working memory function in the Morris water maze was evaluated. At the end of the behavioral assessment (45th day post-surgery) part of experimental animals underwent transcardiac perfusion for histological analysis. Another group was euthanized on the 3rd, 14th, and 45th days post-surgery for nerve growth factor (NGF) evaluation. RESULTS: Resveratrol treatment along 7 days after CCH significantly attenuated pyramidal cell death in the CA1 hippocampal subfield and prevented both spatial working and reference memory impairments. Our results revealed an enhancement of NGF expression 3 days after CCH in all ischemic animals. A late increase in hippocampal NGF levels was detected after 45 days only in CCH-RSV treated animals. CONCLUSIONS: Results presented here show morphological and functional neuroprotective actions of RSV treatment for CCH, as well as support the inducing effects of RSV on the expression of NGF and its possible association to the neuroprotective action in this rodent model of vascular dementia.