Physico-Chemically Distinct Nanomaterials Synthesized from Derivates of a Poly(Anhydride) Diversify the Spectrum of Loadable Antibiotics

Recent advances in the field of nanotechnology such as nanoencapsulation offer new biomedical applications, potentially increasing the scope and efficacy of therapeutic drug delivery. In addition, the discovery and development of novel biocompatible polymers increases the versatility of these encapsulating nanostructures, enabling chemical properties of the cargo and vehicle to be adapted to specific physiological requirements. Here, we evaluate the capacity of various polymeric nanostructures to encapsulate various antibiotics of different classes, with differing chemical structure. Polymers were sourced from two separate derivatives of poly(methyl vinyl ether-alt-maleic anhydride) (PMVE/MA): an acid (PMVE/MA-Ac) and a monoethyl ester (PMVE/MA-Es). Nanoencapsulation of antibiotics was attempted through electrospinning, and nanoparticle synthesis through solvent displacement, for both polymers. Solvent incompatibilities prevented the nanoencapsulation of amikacin, neomycin and ciprofloxacin in PMVE/MA-Es nanofibers. However, all compounds were successfully loaded into PMVE/MA-Es nanoparticles. Encapsulation efficiencies in nanofibers reached approximately 100% in all compatible systems; however, efficiencies varied substantially in nanoparticles systems, depending on the tested compound (14%–69%). Finally, it was confirmed that both these encapsulation processes did not alter the antimicrobial activity of any tested antibiotic against Staphylococcus aureus and Escherichia coli, supporting the viability of these approaches for nanoscale delivery of antibioticsThis research was funded by the Spanish Ministerio de Economía y Competitividad, grant numbers MAT-2017-86805-R and MAT-2014-53282-R,and Spanish Ministerio de Ciencia e Innovación (MCI)—Agencia Estatal de Investigación (AEI)/Fondo Europeo de Desarrollo Regional (FEDER), grant number RTI2018-101969-J-I0

Bioactive trans-resveratrol as dispersant of graphene in water. Molecular interactions

Currently, the preparation of high-quality graphene (G) dispersions is crucial due to the increasing demand for this nanomaterial in a wide range of industries. However, given the strong 7C-7C stacking tendency between G sheets, dispersant agents such as surfactants or polymers are required to attain stable and homogenous disper-sions in liquid media. In the present work, the effectiveness of resveratrol (RV), a fluorescent bioactive compound with antioxidant activity, as a dispersing agent for G in aqueous solutions was assessed. The interaction between G and RV was investigated via absorbance, fluorescence and Raman measurements. Dispersions were prepared via bath sonication, followed by probe ultrasonication and centrifugation, though the two last stages have little effect on the dispersion quality. The addition of G causes a quenching on RV fluorescence, and its magnitude raises with increasing G concentration, being the effect stronger up to 10 mg L-1. The change in the centrifugation speed and time have hardly influence on the RV fluorescence in the presence of G. The RV content remaining in the bulk solution after G dispersion, measured via UV-Vis absorption, decreases linearly with increasing G concentration. RV can effectively disperse all the G present in the sample up to 10 mg L-1; at higher concen-trations, the dispersing ability slightly decreases, and the G content is distributed between the bulk solution and the centrifuged residue. Besides, the fluorescence of RV dispersed in G is much higher in methanol than in an aqueous medium. TEM analysis confirms the good exfoliation of G upon ultrasonication in RV solutions and indicates that the layer thickness depends on the G/RV ratio. The results of this study could open new per-spectives for using natural products like resveratrol as biocompatible and efficient dispersing agents of G to be used in numerous applications, especially in biomedicine.Ministerio de Ciencia, Innovación y Universidade

Graphene-Based Sensors for the Detection of Bioactive Compounds: A Review

Over the last years, different nanomaterials have been investigated to design highly selective and sensitive sensors, reaching nano/picomolar concentrations of biomolecules, which is crucial for medical sciences and the healthcare industry in order to assess physiological and metabolic parameters. The discovery of graphene (G) has unexpectedly impulsed research on developing cost-effective electrode materials owed to its unique physical and chemical properties, including high specific surface area, elevated carrier mobility, exceptional electrical and thermal conductivity, strong stiffness and strength combined with flexibility and optical transparency. G and its derivatives, including graphene oxide (GO) and reduced graphene oxide (rGO), are becoming an important class of nanomaterials in the area of optical and electrochemical sensors. The presence of oxygenated functional groups makes GO nanosheets amphiphilic, facilitating chemical functionalization. G-based nanomaterials can be easily combined with different types of inorganic nanoparticles, including metals and metal oxides, quantum dots, organic polymers, and biomolecules, to yield a wide range of nanocomposites with enhanced sensitivity for sensor applications. This review provides an overview of recent research on G-based nanocomposites for the detection of bioactive compounds, providing insights on the unique advantages offered by G and its derivatives. Their synthesis process, functionalization routes, and main properties are summarized, and the main challenges are also discussed. The antioxidants selected for this review are melatonin, gallic acid, tannic acid, resveratrol, oleuropein, hydroxytyrosol, tocopherol, ascorbic acid, and curcumin. They were chosen owed to their beneficial properties for human health, including antibiotic, antiviral, cardiovascular protector, anticancer, anti-inflammatory, cytoprotective, neuroprotective, antiageing, antidegenerative, and antiallergic capacity. The sensitivity and selectivity of G-based electrochemical and fluorescent sensors are also examined. Finally, the future outlook for the development of G-based sensors for this type of biocompounds is outlined

Surface functionalization of graphene oxide with tannic acid: Covalent vs non-covalent approaches

Graphene oxide (GO) is gaining a lot of interest in material science, biomedicine and biotechnology due to its outstanding physical properties, combined with its surface functionalization capacity, processability in aqueous media and biocompatibility. However, van der Waals forces among GO layers result in aggre-gation, yet its dispersion, large-scale production, and reinforcing efficiency remain challenging. Herein, simple and environmentally friendly methods via covalent and non-covalent routes have been developed to exfoliate and prepare surface-functionalized GO nanosheets with tannic acid (TA), a biological macro-molecule with antioxidant activity. Four esterification strategies were tested: direct, carbodiimide acti-vated, oxalyl chloride acylation and via an acid-functionalized GO intermediate. The resulting samples have been extensively characterized to get knowledge on the GO-TA interactions and the degree of graft-ing, as well as their surface topography, level of hydrophilicity, solubility/dispersibility, thermal and antibacterial properties. The covalent grafting of TA renders the GO surface more hydrophobic, resulting in improved dispersion in organic solvents. Besides, TA acts as a crosslinker between the GO nanosheets, leading to higher thermal resistance. A synergistic effect of both GO and TA on inhibiting bacterial growth has also been found. The esterification via carbodiimide leads to the highest grafting degree, the best thermal stability and the most effective antibacterial activity. This work not only highlights the great potential of TA for both exfoliation and surface functionalization of GO, but also extends its applications in biomedicine and for the development of green nanocomposites. (c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Graphene Oxides Derivatives Prepared by an Electrochemical Approach: Correlation between Structure and Properties

Graphene oxide (GO) can be defined as a single monolayer of graphite with oxygen-containing functionalities such as epoxides, alcohols, and carboxylic acids. It is an interesting alternative to graphene for many applications due to its exceptional properties and feasibility of functionalization. In this study, electrochemically exfoliated graphene oxides (EGOs) with different amounts of surface groups, hence level of oxidation, were prepared by an electrochemical two-stage approach using graphite as raw material. A complete characterization of the EGOs was carried out in order to correlate their surface topography, interlayer spacing, defect content, and specific surface area (SSA) with their electrical, thermal, and mechanical properties. It has been found that the SSA has a direct relationship with the d-spacing. The EGOs electrical resistance decreases with increasing SSA while rises with increasing the D/G band intensity ratio in the Raman spectra, hence the defect content. Their thermal stability under both nitrogen and dry air atmospheres depends on both their oxidation level and defect content. Their macroscopic mechanical properties, namely the Young's modulus and tensile strength, are influenced by the defect content, while no correlation was found with their SSA or interlayer spacing. Young moduli values as high as 54 GPa have been measured, which corroborates that the developed method preserves the integrity of the graphene flakes. Understanding the structure-property relationships in these materials is useful for the design of modified GOs with controllable morphologies and properties for a wide range of applications in electrical/electronic devices

Tailorable synthesis of highly oxidized graphene oxides via an environmentally friendly electrochemical process

Graphene oxide (GO) is an attractive alternative to graphene for many applications due to its captivating optical, chemical, and electrical characteristics. In this work, GO powders with a different amount of surface groups were synthesized from graphite via an electrochemical two-stage process. Many synthesis conditions were tried to maximize the oxidation level, and comprehensive characterization of the resulting samples was carried out via elemental analysis, microscopies (TEM, SEM, AFM), X-ray diffraction, FT-IR and Raman spectroscopies as well as electrical resistance measurements. SEM and TEM images corroborate that the electrochemical process used herein preserves the integrity of the graphene flakes, enabling to obtain large, uniform and well exfoliated GO sheets. The GOs display a wide range of C/O ratios, determined by the voltage and time of each stage as well as the electrolyte concentration, and an unprecedented minimum C/O value was obtained for the optimal conditions. FT-IR evidences strong intermolecular interactions between neighbouring oxygenated groups. The intensity ratio of D/G bands in the Raman spectra is high for samples prepared using concentrated H2SO4 as an electrolyte, indicative of many defects. Furthermore, these GOs exhibit smaller interlayer spacing than that expected according to their oxygen content, which suggests predominant oxidation on the flake edges. Results point out that the electrical resistance is conditioned mostly by the interlayer distance and not simply by the C/O ratio. The tuning of the oxidation level is useful for the design of GOs with tailorable structural, electrical, optical, mechanical, and thermal properties.Ministerio de Ciencia, Innovacion y Universidade

Diagnóstico Territorial del Litoral de Cantabria. Volumen I: Informe.

Estudios de base para la redacción del Plan de Ordenación del Litoral (POL) de Cantabria.Este proyecto de investigación aplicada se ha realizado gracias al Convenio de Colaboración entre el Gobierno de Cantabria y la Universidad de Cantabria titulado “Diagnóstico Territorial del Litoral de Cantabria”

Análisis Socio-Urbanístico de Cantabria. Volumen II: Análisis del Planeamiento.

Estudios de base para la redacción de las Normas Urbanísticas Regionales (NUR) de Cantabria.Este proyecto de investigación aplicada se ha realizado gracias al Convenio de Colaboración entre el Gobierno de Cantabria y la Universidad de Cantabria titulado “Análisis Socio-Urbanístico de Cantabria”

Análisis Socio-Urbanístico de Cantabria. Volumen VI: Diagnóstico de Planeamiento y Organización del Territorio.

Estudios de base para la redacción de las Normas Urbanísticas Regionales (NUR) de Cantabria.Este proyecto de investigación aplicada se ha realizado gracias al Convenio de Colaboración entre el Gobierno de Cantabria y la Universidad de Cantabria titulado “Análisis Socio-Urbanístico de Cantabria”

Diagnóstico Territorial del Litoral de Cantabria. Volumen II: Cartografía de Unidades Territoriales y Red Viaria.

Estudios de base para la redacción del Plan de Ordenación del Litoral (POL) de Cantabria.Este proyecto de investigación aplicada se ha realizado gracias al Convenio de Colaboración entre el Gobierno de Cantabria y la Universidad de Cantabria titulado “Diagnóstico Territorial del Litoral de Cantabria”