Changes in IR band areas and band shifts during water adsorption to lecithin and ceramide

Caseinate-coated zein nanoparticles as potential delivery vehicles for guavinoside B from guava: Molecular interactions and encapsulation properties

Guavinoside B (GUB) is a characteristic constituent from guava with strong antioxidant activity; however, its low water solubility limits its utilization. Herein, we investigated the interaction between GUB and zein, a prolamin with self-assembling property, using multiple spectroscopic methods and fabricated GUB-zein-NaCas nanoparticles (GUB-Z-N NPs) via the antisolvent coprecipitation approach. GUB caused fluorescence quenching to zein via the static quenching mechanism. Fourier-transform infrared spectroscopy and computational analysis revealed that GUB bound to zein via van der Waals interaction, hydrogen bond, and hydrophobic forces. The GUB-Z-N NPs were in the nanometric size range (< 200 nm) and exhibited promising encapsulation efficiency and redispersibility after freeze-drying. These particles remained stable for up to 31 days at 4 °C and great resistance to salt and pH variation, and displayed superior antioxidant activity to native GUB. The current study highlights the potential of zein-based nanoparticles as delivery vehicles for GUB in the food industry.

Nanomaterials Based on 2,7,12,17-Tetra-tert-butyl-5,10,15,20-tetraaza-21H,23H-porphine Exhibiting Bifunctional Sensitivity for Monitoring Chloramphenicol and Co2

Monitoring antibiotic retention in human body fluids after treatment and controlling heavy metal content in water are important requirements for a healthy society. Therefore, the approach proposed in this study is based on developing new optical sensors using porphyrin or its bifunctional hybrid materials made with AuNPs to accomplish the accurate detection of chloramphenicol and cobalt. To produce the new optical chloramphenicol sensors, 2,7,12,17-tetra-tert-butyl-5,10,15,20-tetraaza-21H,23H-porphine (TBAP) was used, both alone in an acid medium and as a hybrid material with AuNPs in a water-DMSO acidified environment. The same hybrid material in the unchanged water-DMSO medium was the sensing material used for Co2+ monitoring. The best results of the hybrid materials were explained by the synergistic effects between the TBAP azaporphyrin and AuNPs. Chloramphenicol was accurately detected in the range of concentrations between 3.58 × 10-6 M and 3.37 × 10-5 M, and the same hybrid material quantified Co2+ in the concentration range of 8.92 × 10-5 M-1.77 × 10-4 M. In addition, we proved that AuNPs can be used for the detection of azaporphyrin (from 2.66 × 10-5 M to 3.29 × 10-4 M), making them a useful tool to monitor porphyrin retention after cancer imaging procedures or in porphyria disease. In conclusion, we harnessed the multifunctionality of this azaporphyrin and of its newly obtained AuNP plasmonic hybrids to detect chloramphenicol and Co2+ quickly, simply, and with high precision.

Riboflavin mediated UV crosslinking of chitosan-gelatin cryogels for loading of hydrophobic bioactive compounds

Chitosan-gelatin cryogels with good loading capacity of hydrophobic compounds were successfully obtained by UV-induced crosslinking. Using riboflavin as photoinitiator was a suitable alternative to classical carbodiimide crosslinking in obtaining carrier matrices for bioactive hydrophobic compounds. Chitosan had a double role, acting both as a base polymer for the hydrogel network and as co-initiator in riboflavin photo-crosslinking. This co-initiator role of chitosan is due to its electron donor capacity, being well known as a Lewis base type macromolecule. The rheological behaviour of the chitosan-gelatin hydrogel precursor solutions was greatly influenced by riboflavin addition as well as by UV irradiation. As a consequence, the temperature of the sol-gel transition during cooling decreased to 25.5 °C. Compared with classical carbodiimide crosslinking, UV irradiation lead to gels with increased network stability, enhanced elastic behaviour, higher structural strength and almost total stress recovery yield (99 %), the latter indicating self-healing capacity. The cryogels manifested pH responsive swelling, this being highest at close to neutral pH of 7.4. Although hydrophilic in nature, the chitosan-gelatin cryogels crosslinked under the combined effect of riboflavin and UV exposure possess the necessary chemical functionality and morphology that allowed successful embedding of hydrophobic clove essential oil. This was loaded by immersion or fumigation and imparted antioxidant activity to the polymeric matrix.

Examining the Water-Polymer Interactions in Non-Isocyanate Polyurethane/Polyhedral Oligomeric Silsesquioxane Hybrid Hydrogels

Non-isocyanate polyurethane (NIPU) networks physically modified with octa(3-hydroxy-3-methylbutyldimethylsiloxy)POSS (8OHPOSS, 0-10 wt%) were conditioned in environments of different relative humidities (up to 97%) to study water-polymer interactions. The equilibrium sorption isotherms are of Brunauer type III in a water activity range of 0-0.97 and are discussed in terms of the Guggenheim (GAB) sorption model. The study shows that the introduction of 8OHPOSS, even in a large amount (10 wt%), does not hinder the water affinity of the NIPU network despite the hydrophobic nature of POSS; this is attributable to the homogenous dispersion of POSS in the polymer matrix. The shift in the urethane-derived carbonyl bands toward lower wavenumbers with a simultaneous shift in the urethane N-H bending bands toward higher wavenumbers exposes the breakage of polymer-polymer hydrogen bonds upon water uptake due to the formation of stronger water-polymer hydrogen bonds. Upon water absorption, a notable decrease in the glass transition temperature (Tg) is observed for all studied materials. The progressive reduction in Tg with water uptake is driven by plasticization and slaving mechanisms. POSS moieties are thought to impact slaving indirectly by slightly affecting water uptake at very high hydration levels.

New insight into the negative impact of imidazolium-based ionic liquid [C10mim]Cl on Hela cells: From membrane damage to biochemical alterations

As an alternative to volatile organic solvents, ionic liquids (ILs) are known as "green solvents", and widely used in industrial applications. However, due to their high solubility and stability, ILs have tendency to persist in the water environment, thus having potential negative impacts on the aquatic ecosystem. For assessing the environmental risks of ILs, a fundamental understanding of the toxic effects and mechanisms of ILs is needed. Here we evaluated the cytotoxicity of 1-methyl-3-decylimidazolium chloride ([C₁₀mim]Cl) and elucidated the main toxic mechanism of [C₁₀mim]Cl in human cervical carcinoma (Hela) cells. Microstructural analysis revealed that [C₁₀mim]Cl exposure caused the cell membrane breakage, swollen and vacuolated mitochondria, and spherical cytoskeletal structure. Cytotoxicity assays found that [C₁₀mim]Cl exposure increased ROS production, decreased mitochondrial membrane potential, induced cell apoptosis and cell cycle arrest. These results indicated that [C₁₀mim]Cl could induce damage to cellular membrane structure, affect the integrity of cell ultrastructure, cause the oxidative damage and ultimately lead to the inhibition of cell proliferation. Moreover, alterations of biochemical information including the increased ratios of unsaturated fatty acid and carbonyl groups to lipid, and lipid to protein, and the decreased ratios of Amide I to Amide II, and α-helix to β-sheet were observed in [C₁₀mim]Cl treated cells, suggesting that [C₁₀mim]Cl could affect the structure of membrane lipid alkyl chain and cell membrane fluidity, promote the lipid peroxidation and alter the protein secondary structure. The findings from this work demonstrated that membrane structure is the key target, and membrane damage is involved in [C₁₀mim]Cl induced cytotoxicity.

Water Adsorption to Leaves of Tall Cryptomeria japonica Tree Analyzed by Infrared Spectroscopy under Relative Humidity Control

Leaf water storage is a complex interaction between live tissue properties (anatomy and physiology) and physicochemical properties of biomolecules and water. How leaves adsorb water molecules based on interactions between biomolecules and water, including hydrogen bonding, challenges our understanding of hydraulic acclimation in tall trees where leaves are exposed to more water stress. Here, we used infrared (IR) microspectroscopy with changing relative humidity (RH) on leaves of tall Cryptomeria japonica trees. OH band areas correlating with water content were larger for treetop (52 m) than for lower-crown (19 m) leaves, regardless of relative humidity (RH). This high water adsorption in treetop leaves was not explained by polysaccharides such as Ca-bridged pectin, but could be attributed to the greater cross-sectional area of the transfusion tissue. In both treetop and lower-crown leaves, the band areas of long (free water: around 3550 cm⁻¹) and short (bound water: around 3200 cm⁻¹) hydrogen bonding OH components showed similar increases with increasing RH, while the band area of free water was larger at the treetop leaves regardless of RH. Free water molecules with longer H bonds were considered to be adsorbed loosely to hydrophobic CH surfaces of polysaccharides in the leaf-cross sections.

Interactions of Glycerol, Diglycerol, and Water Studied Using Attenuated Total Reflection Infrared Spectroscopy

In order to examine the mixing properties of glycerol-water and diglycerol-water solutions, these solutions were measured using attenuated total reflection infrared spectroscopy. The absorbance spectra corrected for 1 µm thickness were subtracted by pure polyols for obtaining water spectra, and by pure water for polyol spectra. Both asymmetric and symmetric CH₂ stretching vibration bands (around 2940, 2885 cm^-1) shifted about 10 cm^-1 to lower wavenumber side (redshifts) with increasing polyol concentrations, especially at higher concentrations. Redshifts of C-O-H rocking bands (around 1335 cm^-1) with increasing polyol concentrations are slightly larger for diglycerol-water (10 > 6 cm^-1) than glycerol-water solutions. C-O stretching bands of CHOH groups (1125 and 1112 cm^-1) shift slightly but in opposite sides for glycerol and diglycerol at highest polyol concentrations (90-100 wt%). These shifts of CH₂ stretching, COH rocking, and CO stretching of CHOH at higher polyol concentrations suggest interactions of outer CH₂ with inner CHOH groups of surrounding polyols. The normalized band area changes with polyol concentrations could be fitted by quadratic polynomials possibly due to mixtures of different interactions between water-water, polyol-water, and polyol-polyol molecules. The OH stretching band for diglycerol 90 wt% shows three humps indicating at least three OH components: long, medium, and short H bond water molecules. Short H bond water molecules are the major component possibly between inner CHOH and outer side CH₂OH groups, while the long H component might loosely bind to outer CH₂OH groups.