Mechanochemically Synthetized PAN-Based Co-N-Doped Carbon Materials as Electrocatalyst for Oxygen Evolution Reaction.

We report a new class of polyacrylonitrile (PAN)-based Co-N-doped carbon materials that can act as suitable catalyst for oxygen evolution reactions (OER). Different Co loadings were mechanochemically added into post-consumed PAN fibers. Subsequently, the samples were treated at 300 °C under air (PAN-A) or nitrogen (PAN-N) atmosphere to promote simultaneously the Co3O4 species and PAN cyclization. The resulting electrocatalysts were fully characterized and analyzed by X-ray diffraction (XRD) and photoelectron spectroscopy (XPS), transmission (TEM) and scanning electron (SEM) microscopies, as well as nitrogen porosimetry. The catalytic performance of the Co-N-doped carbon nanomaterials were tested for OER in alkaline environments. Cobalt-doped PAN-A samples showed worse OER electrocatalytic performance than their homologous PAN-N ones. The PAN-N/3% Co catalyst exhibited the lowest OER overpotential (460 mV) among all the Co-N-doped carbon nanocomposites, reaching 10 mA/cm2. This work provides in-depth insights on the electrocatalytic performance of metal-doped carbon nanomaterials for OER.

Multifunctional green supramolecular solvents for cost-effective production of highly stable astaxanthin-rich formulations from Haematococcus pluvialis.

The interest of food industry to merchandise natural astaxanthin is growing up. However, it confronts scientific and technological challenges mainly related to its poor water solubility and chemical instability. Here, we present a new quick and efficient green process to simultaneously extract, encapsulate and stabilize astaxanthin from Haematococcus pluvialis. The process is based on the hitherto unexplored combination of supramolecular solvents (SUPRAS), nanostructured liquids generated from amphiphiles through sequential self-assembly and coacervation, and nanostructured lipid carriers (NLCs). These novel nanosystems were characterized by means of dynamic light scattering, AFM and cryoSEM, revealing spherical particles of ∼100 nm. Their antioxidant activity was measured by ORAC (20.6 ±â€¯3.9 µM TE) and α-TEAC (2.92 ±â€¯0.58 µM α-TE) assays and their in vitro capacity to inhibit ROS by DHE probe. Results showed that the SUPRAS-NLCs proposed yield high extraction and encapsulation efficiencies (71 ±â€¯4%) in combination with a remarkable time stability (180 d, 4 °C).

A high thermally stable oligomer-based supramolecular solvent for universal headspace Gas Chromatography: Proof-of-principle determination of residual solvents in drugs.

Supramolecular solvent (SUPRAS) extraction is gaining attraction as a sample treatment technique because of its great performance in terms of effectiveness, versatility, sample clean-up, quickness, cost and sustainability. However, the nature of SUPRASs, being formed by amphiphile molecules, results in poor compatibility with Gas Chromatography (GC). Here, we show the hitherto unexplored development of a SUPRAS with high thermal stability (HTS) suitable for subsequent direct analysis by Headspace (HS)-GC. This novel HTS-SUPRAS, based on poly-undecylenic acid -an oligomeric surfactant-, tetraglyme -a polar aprotic solvent with excellent chemical and thermal stability- and water, was fully characterized in terms of composition and physical properties such as thermal stability. Subsequently, the HTS-SUPRAS developed was further successfully applied, as a proof-of-principle, to the extraction and determination of residual solvents in pharmaceutical drugs, including several solvents (class 2C) whose analysis by HS-GC has been shown to be highly complex. Analytical performance was demonstrated as mandated by the International Council for Harmonisation of technical requirements for pharmaceuticals for human use (ICH). Furthermore, excellent recoveries (70-120%) and high precisions (<20%, expressed as relative standard deviations) were obtained for the analysis of several different drug formulations spiked with the analyzed 37 residual solvents at their respective maximum residue levels.

Astaxanthin-Loaded Nanostructured Lipid Carriers for Preservation of Antioxidant Activity.

Astaxanthin is a xanthophyll carotenoid showing efficient scavenging ability and represents an interesting candidate in the development of new therapies for preventing and treating oxidative stress-related pathologies. However, its high lipophilicity and thermolability often limits its antioxidant efficacy in human applications. Here, we developed a formulation of lipid carriers to protect astaxanthin's antioxidant activity. The synthesis of natural astaxanthin-loaded nanostructured lipid carriers using a green process with sunflower oil as liquid lipid is presented. Their antioxidant activity was measured by α-Tocopherol Equivalent Antioxidant Capacity assay and was compared to those of both natural astaxanthin and α-tocopherol. Characterizations by dynamic light scattering, atomic force microscopy, and scattering electron microscopy techniques were carried out and showed spherical and surface negative charged particles with z-average and polydispersity values of ~60 nm and ~0.3, respectively. Astaxanthin loading was also investigated showing an astaxanthin recovery of more than 90% after synthesis of nanostructured lipid carriers. These results demonstrate the capability of the formulation to stabilize astaxanthin molecule and preserve and enhance the antioxidant activity.

The use of a restricted access volatile supramolecular solvent for the LC/MS-MS assay of bisphenol A in urine with a significant reduction of phospholipid-based matrix effects.

Restricted access-volatile supramolecular solvents (RAM-VOL-SUPRAS) are here proposed as a new strategy for the quick removal of protein and phospholipids and efficient analyte extraction in LC-MS bioanalysis. Quantification of bisphenol A in urine was selected to prove the suitability of this approach for the intended purpose. RAM-VOL-SUPRAS were spontaneously synthesized in urine by addition of hexanol (83 µL) dissolved in THF (150 µL). SUPRAS composition was environment-dependent and an equation for prediction of SUPRAS volume under given experimental conditions was proposed. Urinary proteins were removed by flocculation by the combined action of THF and hexanol. Phospholipids were extracted in the SUPRAS by the formation of mixed aggregates with hexanol and precipitated as the SUPRAS extract (75 µL) was evaporated to dryness. BPA, re-extracted from the residue, was analysed by LC-(ESI)-MS/MS. Removal of phospholipids by precipitation was proved by monitoring them in both evaporated and unevaporated urine SUPRAS extracts by LC-MS. This removal led to significant reduction in matrix-effects in the determination of BPA. The method quantification limit in urine was 0.025 ng mL-1 and the repeatability for 0.4 ng mL-1 of BPA, expressed as relative standard deviation, was 4.5%. Concentrations of BPA in the urine samples analysed were in the range 0.357-1.58 ng mL-1. Recoveries were within the range 96-107%. This new approach for sample treatment in bioanalysis, based on the simplicity of dual precipitation of proteins and phospholipids, allows obtaining much cleaner extracts than conventional procedures.