Ice-Templated and Cross-Linked Xanthan-Based Hydrogels: Towards Tailor-Made Properties.

The use of polysaccharides with good film-forming properties in food packaging systems is a promising area of research. Xanthan gum (XG), an extracellular polysaccharide, has many industrial uses, including as a common food additive (E415). It is an effective thickening agent, emulsifier, and stabilizer that prevents ingredients from separating. Nevertheless, XG-based polymer films have some disadvantages, such as poor mechanical properties and high hydrophilic features, which reduce their stability when exposed to moisture and create difficulties in processing and handling. Thus, the objective of this work was to stabilize a XG matrix by cross-linking it with glycerol diglycidyl ether, 1,4-butanediol diglycidyl ether, or epichlorohydrin below the freezing point of the reaction mixture. Cryogelation is an ecological, friendly, and versatile method of preparing biomaterials with improved physicochemical properties. Using this technique, XG-based cryogels were successfully prepared in the form of microspheres, monoliths, and films. The XG-based cryogels were characterized by FTIR, SEM, AFM, swelling kinetics, and compressive tests. A heterogeneous morphology with interconnected pores, with an average pore size depending on both the nature of the cross-linker and the cross-linking ratio, was found. The use of a larger amount of cross-linker led to both a much more compact structure of the pore walls and to a significant decrease in the average pore size. The uniaxial compression tests indicated that the XG-based cryogels cross-linked with 1,4-butanediol diglycidyl ether exhibited the best elasticity, sustaining maximum deformations of 97.67%, 90.10%, and 81.80%, respectively.

Correlation between Mechanical and Morphological Properties of Polyphenol-Laden Xanthan Gum/Poly(vinyl alcohol) Composite Cryogels.

This study aimed to evaluate the effect of the synthesis parameters and the incorporation of natural polyphenolic extract within hydrogel networks on the mechanical and morphological properties of physically cross-linked xanthan gum/poly(vinyl alcohol) (XG/PVA) composite hydrogels prepared by multiple cryo-structuration steps. In this context, the toughness, compressive strength, and viscoelasticity of polyphenol-loaded XG/PVA composite hydrogels in comparison with those of the neat polymer networks were investigated by uniaxial compression tests and steady and oscillatory measurements under small deformation conditions. The swelling behavior, the contact angle values, and the morphological features revealed by SEM and AFM analyses were well correlated with the uniaxial compression and rheological results. The compressive tests revealed an enhancement of the network rigidity by increasing the number of cryogenic cycles. On the other hand, tough and flexible polyphenol-loaded composite films were obtained for a weight ratio between XG and PVA of 1:1 and 10 v/v% polyphenol. The gel behavior was confirmed for all composite hydrogels, as the elastic modulus (G') was significantly greater than the viscous modulus (G″) for the entire frequency range.

New Quaternary Ammonium Derivatives Based on Citrus Pectin.

New citrus pectin derivatives carrying pendant N,N-dimethyl-N-alkyl-N-(2-hydroxy propyl) ammonium chloride groups were achieved via polysaccharide derivatization with a mixture of N,N-dimethyl-N-alkyl amine (alkyl = ethyl, butyl, benzyl, octyl, dodecyl) and epichlorohydrin in aqueous solution. The structural characteristics of the polymers were examined via elemental analysis, conductometric titration, Fourier Transform Infrared spectroscopy (FTIR) and 1D (1H and 13C) nuclear magnetic resonance (NMR). Capillary viscosity measurements allowed for the study of viscometric behavior as well as the determination of viscosity-average molar mass for pristine polysaccharide and intrinsic viscosity ([η]) values for pectin and its derivatives. Dynamic light scattering measurements (DLS) showed that pectin-based polymers formed aggregates in aqueous solution with a unimodal distribution. Critical aggregation concentration (cac) for the hydrophobic pectin derivatives were determined using fluorescence spectroscopy. Atom force microscopy (AFM) images allowed for the investigation of the morphology of polymeric populations obtained in aqueous solution, consisting of flocs and aggregates for crude pectin and its hydrophilic derivatives and well-organized aggregates for lipophilic pectin derivatives. Antimicrobial activity, examined using the disc diffusion method, proved that all polymers were active against Staphylococcus aureus bacterium and Candida albicans yeast.

Cu and Zn Interactions with Peptides Revealed by High-Resolution Mass Spectrometry.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by abnormal extracellular amyloid-beta (Aß) peptide depositions in the brain. Among amorphous aggregates, altered metal homeostasis is considered a common risk factor for neurodegeneration known to accelerate plaque formation. Recently, peptide-based drugs capable of inhibiting amyloid aggregation have achieved unprecedented scientific and pharmaceutical interest. In response to metal ions binding to Aß peptide, metal chelation was also proposed as a therapy in AD. The present study analyzes the interactions formed between NAP octapeptide, derived from activity-dependent neuroprotective protein (ADNP), amyloid Aß(9-16) fragment and divalent metal ions such as Cu and Zn. The binding affinity studies for Cu and Zn ions of synthetic NAP peptide and Aß(9-16) fragment were investigated by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), electrospray ion trap mass spectrometry (ESI-MS) and atomic force microscopy (AFM). Both mass spectrometric methods confirmed the formation of metal-peptide complexes while the AFM technique provided morphological and topographic information regarding the influence of metal ions upon peptide crystallization. Our findings showed that due to a rich histidine center, the Aß(9-16) fragment is capable of binding metal ions, thus becoming stiff and promoting aggregation of the entire amyloid peptide. Apart from this, the protective effect of the NAP peptide was found to rely on the ability of this octapeptide to generate both chelating properties with metals and interactions with Aß peptide, thus stopping its folding process.

A Proteomic Approach to Identify Zein Proteins upon Eco-Friendly Ultrasound-Based Extraction.

Zein is a type of prolamin storage protein that has a variety of biomedical and industrial applications. Due to the considerable genetic variability and polyploidity of the starting material, as well as the extraction methods used, the characterization of the protein composition of zein requires a combination of different analytical processes. Therefore, we combined modern analytical methods such as mass spectrometry (MS), Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), atomic force microscopy (AFM), or Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) for a better characterization of the extracted zein. In this study, we present an enhanced eco-friendly extraction method, including grinding and sieving corn seeds, for prolamins proteins using an ultrasonic extraction methodology. The use of an ultrasonic homogenizer, 65% ethanol extraction buffer, and 710 µm maize granulation yielded the highest protein extraction from all experimental conditions we employed. An SDS PAGE analysis of the extracted zein protein mainly revealed two intense bands of approximatively 20 and 23 kDa, suggesting that the extracted zein was mostly α-zein monomer. Additionally, MS analysis revealed as a main component the α-zein PMS2 (Uniprot accession no. P24450) type protein in the maize flour extract. Moreover, AFM studies show that extracting zein with a 65% ethanol and a 710 µm granulation yields a homogeneous content that could allow these proteins to be employed in future medical applications. This research leads to a better understanding of zeins content critical for developing new applications of zein in food and pharmaceutical industries, such as biocompatible medical vehicles based on polyplexes complex nanoparticles of zein with antimicrobial or drug delivery properties.

Antioxidant/Antibacterial Electrospun Nanocoatings Applied onto PLA Films.

Polylactic acid (PLA) films were coated by coaxial electrospinning with essential and vegetable oils (clove and argan oils) and encapsulated into chitosan, in order to combine the biodegradability and mechanical properties of PLA substrates with the antimicrobial and antioxidant properties of the chitosan⁻oil nanocoatings. It has been established that the morphology of the electrospun nanocoatings mainly depend on the average molecular weight (MW) of chitosan. Oil beads, encapsulated into the main chitosan nanofibers, were obtained using high-MW chitosan (Chit-H). Oil encapsulated in chitosan naoparticles resulted when low-MW chitosan (Chit-L) was used. The coating layer, with a thickness of 100 ± 20 nm, had greater roughness for the samples containing Chit-H compared with the samples containing Chit-L. The coated PLA films had higher antibacterial activity when the nanocoating contained clove oil rather than when argan oil was used, for both types of chitosan. Nanocoatings containing Chit-H had higher antibacterial activity compared with those containing Chit-L, for both types of oil tested, due to the larger surface area of the rougher nanoscaled morphology of the coating layer that contained Chit-L. The chitosan⁻clove oil combination had higher antioxidant activity compared to the simple chitosan nanocoating, which confirmed their synergistic activities. The low activity of systems containing argan oil was explained by big differences between their chemical composition and viscosity.

Hybrid Nanostructures Containing Sulfadiazine Modified Chitosan as Antimicrobial Drug Carriers.

Chitosan (CH) nanofibrous structures containing sulfadiazine (SDZ) or sulfadiazine modified chitosan (SCH) in the form of functional nanoparticles attached to nanofibers (hybrid nanostructures) were obtained by mono-axial and coaxial electrospinning. The mono-axial design consisted of a SDZ/CH mixture solution fed through a single nozzle while the coaxial design consisted of SCH and CH solutions separately supplied to the inner and outer nozzle (or in reverse order). The CH ability to form nanofibers assured the formation of a nanofiber mesh, while SDZ and SCH, both in form of suspensions in the electrospun solution, assured the formation of active nanoparticles which remained attached to the CH nanofiber mesh after the electrospinning process. The obtained nanostructures were morphologically characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SDZ release profiles and kinetics were analyzed. The SDZ or SCH nanoparticles loosely attached at the surface of the nanofibers, provide a burst release in the first 20 min, which is important to stop the possible initial infection in a wound, while the SDZ and SCH from the nanoparticles which are better confined (or even encapsulated) into the CH nanofibers would be slowly released with the erosion/disruption of the CH nanofiber mesh.

Effect of the lignin type on the morphology and thermal properties of the xanthan/lignin hydrogels.

This paper reports the morphological and thermal characterization of xanthan/lignin hydrogels. It has been emphasized the effect of the lignin type on the hydrogel properties. The hydrogels described here were obtained by chemical crosslinking, in the presence of epichlorohydrine as a cross-linker agent. The obtained materials were analyzed by AFM, TG/DTG, DSC, and FT-IR spectroscopy. It has been established that hydrogels have a porous morphology. The lignin type influences the hydrogel morphology which is either fibrilar as in case of hydrogel containing aspen wood lignin (which has the highest content of COOH groups and lowest content of phenolic OH groups) or smooth surface for other hydrogels. The specific intermolecular interactions are stronger in the case of 70 xanthan (X)/30 aspen wood lignin (AWL) hydrogel. The thermal properties of the hydrogels also depend on lignin type, the lowest thermal stability being found for the hydrogel containing lignin with the highest content of functional groups (AWL).