In this work free-standing gels formed from gellan gum (GG) by solvent evaporation are coated with polysaccharide-based polyelectrolyte multilayers, using the layer-by-layer approach. We show that ...PEMs composed of iota-carrageenan (CAR) and three different natural polycationic polymers have composition-dependent antimicrobial properties, and support mammalian cell growth. Cationic polymers (chitosan (CHT), N,N,N-trimethyl chitosan (TMC), and an amino-functionalized tannin derivative (TN)) are individually assembled with the anionic iota-carrageenan (CAR) at pH 5.0. PEMs (15-layers) are alternately deposited on the GG film. The GG film and coated GG films with PEMs are characterized by infrared spectroscopy with attenuated total reflectance (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and water contact angle (WCA) measurements. The TN/CAR coating provides a hydrophobic (WCA = 127°) and rough surface (Rq = 243 ± 48 nm), and the TMC/CAR coating provides a hydrophilic surface (WCA = 78°) with the lowest roughness (Rq = 97 ± 12 nm). Polymer coatings promote stability and durability of the GG film, and introduce antimicrobial properties against Gram-negative (Salmonella enteritidis) and Gram-positive (Staphylococcus aureus) bacteria. The films are also cytocompatible. Therefore, they have properties that can be further developed as wound dressings and food packaging.
•A commercial gellan gum is characterized, supporting stable films due to the metallic ions presence in its composition.•The solvent evaporation method provides a stiffer gellan gum film.•The film is coated with polyelectrolyte multilayers due to the carboxylate moieties on the gellan gum.•Chitosan/iota-carrageenan and N,N,N-trimethyl chitosan/iota-carrageenan coatings support antimicrobial activities.•The coated films can be applied in the food and biomedical fields.
Physical kappa-carrageenan-based hydrogels are often prepared from dilute aqueous kappa-carrageenan (κ-carrageenan) solutions at the presence of metallic ions or by mixing these solutions with ...proteins and other polysaccharides. The κ-carrageenan hydrogels have been used for technological purposes; however, there are no reports about the properties of a commercial GENUGEL® κ-carrageenan produced by the CP Kelco. The flame atomic absorption spectrometry shows that the commercial κ-carrageenan comprises a high content of metallic ions (K+ = 216.1 g kg−1, Na+ = 6.3 g kg−1 and Ca2+ = 12.5 g kg−1). The X-ray photoelectron spectroscopy (XPS) indicates the presence of sodium, calcium, and potassium atoms on the as-received κ-carrageenan and its physical hydrogel surfaces. XPS supports the occurrence of a low protein content onto the sample surfaces, as well. The metallic level (especially for K+) in the commercial κ-carrageenan plays an essential role in the preparation of durable hydrogels. These materials are prepared by cooling aqueous κ-carrageenan solutions at 4.0 and 5.0 wt%. The gelation temperature is determined by measuring G′ &G″ as a function of the temperature. The gelation behavior depends on the κ-carrageenan concentration, as well as the metallic content in the commercial sample. Scanning electron microscopy shows that hydrogels have porous and smooth surfaces. The dried materials swell from 2400 to 3100%, while the disintegration/dissolution test confirms that the samples present high stability in distilled water throughout 14 days. These hydrogels are superabsorbent materials and can be applied in agriculture as soil conditioners.
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•Commercial κ-carrageenan solutions produce durable hydrogels.•FAAS shows that the commercial κ-carrageenan comprises a high content of metallic ions.•Potassium, calcium, and sodium ions crosslink the commercial κ-carrageenan.•The gelation temperature depends on both polymer and metallic ion contents.•Superabsorbent materials are prepared by cooling aqueous solutions (4.0 and 5.0 wt%).
Given the environmental issues caused by the extensive use of conventional petroleum-based packaging, this work proposes functional films based on commercial κ-carrageenan (κc), poly(vinyl alcohol) ...(PVA), and gallic acid (GA) prepared by the “casting” method. Metallic ions in the κc composition stabilized the films, supporting processability and suitable mechanical properties. However, the incorporated GA amount (6.25 and 10 wt%) in the films created from an aqueous κc solution at 3.0 % wt/v (κc3) prevented crystalline domains in the resulting materials. The κc3/GA6.25 and κc3/GA10 films had less tensile strength (8.50 ± 0.61 and 10.28 ± 0.65 MPa) and high elongation at break (2.36 ± 0.16 and 1.19 ± 0.17 %) compared to the other samples, respectively. Low κc contents (κc2.5/GA6.25 and κc2.5/GA10) promoted stiff films and less permeability to water vapor (5.36 ± 0.51 and 3.76 ± 0.02 ×10−12 g(Pa × m × s)−1, respectively. The κc/GA weight ratio also influenced the film wettability, indicating water contact angles (WCAs) between 55 and 74°. The surface wettability implies a low oil permeability and high water swelling capacity of up to 1600 %. The κc/GA also played an essential role in the film's antimicrobial action against Staphylococcus aureus and Escherichia coli. Thus, the κc3/GA10 film showed suitable physical, chemical, and biological properties, having the potential to be applied as food coatings.
Gelatin (GE) and chondroitin sulfate (CS) polyelectrolyte multilayers (PEMs) with or without ionic liquids (ILs) are assembled on oxidized poly(ethylene terephthalate) (PET), using the layer-by-layer ...(LbL) approach. The ILs associated with the PEMs include 1-n-hexadecyl-3-methylimidazolium chloride (C16MImCl), 1-n-hexadecyl-3-methylimidazolium methanesulfonate (C16MImMeS), and 1-n-hexadecyl pyridinium chloride monohydrate (C16PyrCl.H2O). The ILs are associated with PEMs for the first time. The ILs are dissolved in an aqueous GE solution and then associated with CS by the layer-by-layer approach. The alternating deposition of GE or GE/ILs and CS multilayers on the oxidized PET results in durable surface coatings. The oxidized PET and PEMs are characterized by atomic force microscopy (AFM), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), spectroscopic ellipsometry, and water contact angle (WCA) measurements. The GE/CS IL PEM coatings reveal higher wettability (WCA between 41 and 45°) and roughness (root mean square, Rq, values between 74.5 and 89.1 nm) than the unmodified PET (WCA of 90.9° and surface roughness of 26.9 nm). The PEMs are homogeneous surface coatings with durability after exposure to phosphate-buffered saline (pH 7.4) for 24 h. The ILs impart low minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) against Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). The MIC and MBC are lower than 0.625 μg/mL against P. aeruginosa. The CS and GE and the GE/CS PEM do not provide any antimicrobial effect. However, the GE/CS IL PEMs show high antimicrobial capacity, preventing the attachment and growth of microbial cells. The GE/CS IL PEMs are durable, bactericidal, and anti-adhesive surfaces for PET.
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•Poly(ethylene terephthalate) is associated with polyelectrolyte multilayers.•Ionic liquids are associated with the polyelectrolyte multilayers by layer-by-layer.•The ionic liquids increase the surface roughness of the surface coatings.•The surface coatings are stable in buffer solutions (pH 5.0 and 7.4) at 37 °C.•The ionic liquids support outstanding antimicrobial surface coatings.
To obtain pectin-based films is challenging due to the aqueous instability of polyelectrolyte mixtures. We overcome this issue by blending chitosan to pectin of high O-methoxylation degree (56%), ...followed by solvent evaporation. A durable film containing 74 wt% pectin content was produced and used as an adsorbent material toward Cu(II) ions. Kinetic and adsorption equilibrium studies showed that the pseudo-second-order and Sips isotherm models adjusted well to the experimental data, respectively. Langmuir isotherm indicated a maximum adsorption capacity (qm) for Cu(II) removal of 29.20 mg g−1. Differential scanning calorimetry, contact angle measurements, and X-ray photoelectron spectroscopy confirm the adsorption. The chemisorption plays an essential role in the process; thereby, the film reusability is low. After adsorption, the cytocompatible film/Cu(II) pair prevents the proliferation of Escherichia coli.
•A physically crosslinked film contains high pectin content (74 wt%).•The film presents sorption capacity for Cu(II) ions of 29.20 mg g−1.•The chemisorption plays an essential role in the Cu(II) adsorption.•After adsorption, the film/Cu(II) has cytocompatibility for mammalian cells.•The film/Cu(II) prevents the spreading of E. coli on its surface.
We present chitosan (CHT)/heparin (HP) polyelectrolyte complexes (PECs) that quickly adsorb citrate-capped silver nanoparticles (AgNPs). CHT/HP blends in ionic liquid (HMImHSO4) form durable PECs ...after precipitation in water. CHT/HP PECs have positive Zeta potentials (higher than +20 mV). They adsorb citrate-capped AgNPs (Zeta potential of - 12.25 mV) synthesized from Turkevich's method. PEC/AgNPs composites are characterized by spectroscopic, thermal, and microscopy analyses. AgNPs on the PEC surfaces are confirmed by transmission electron microscopy. PECs adsorb AgNPs from aqueous suspensions, achieving ≈ 95% of removal (17.18 μg of AgNPs per milligram of PEC) after only 10 min. The pseudo-second-order kinetic model adjusted well to the experimental data. The PECs release approximately 11.80 μg/mg Ag+ (66%) compared to the initial adsorbed AgNPs content (17.18 μg/mg) after 7200 min at pH 2.0. The PECs present low swelling degrees (between 130 and 150%), supporting high stability in water. PEC/AgNPs composites promote significant bactericidal activity toward Staphylococcus aureus and Escherichia coli between 0.25 and 0.5 mg/mL. This study shows a new strategy to create hybrid polysaccharide/AgNPs composites. PECs can stabilize the AgNPs and release Ag+ ions, supporting antimicrobial materials.
•Polyelectrolyte complexes (PECs) were synthesized using a green solvent.•95% of the citrate-capped silver nanoparticles were adsorbed on PECs' surface.•Citrate-capped silver nanoparticles are visible on PECs.•Hybrid materials present low heparin release at simulated fluids.•The Citrate-capped silver nanoparticles sorption is faster than the Ag+ ion release.
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•A new stable product based on the reaction of DPPH radical and ferulic acid.•Elucidation of the reaction mechanism by efficient method (UHPLC-ESI-Q-TOF-MS/MS).•The main reaction path ...between ferulic acid and DPPH is by hydrogen atom transfer.•The ferulic acid has a similar power antioxidant to Trolox.
The chemical reaction involving phenolic antioxidants from plant´ extracts have not been adequately studied. In this study, we investigate a quick, accurate, and innovative strategy to elucidate the ferulic acid reaction employing a conclusive analytical tool (ultra-high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry, UHPLC-ESI-Q-TOF-MS/MS) used in pharmaceutical, cosmetic, food, and biomedical applications. The ferulic acid- DPPH(2,2-diphenyl-1-picrylhydrazyl) reaction presented three chromatographic peaks with retention times at 5.95, 8.69, and 9.04 min. The peak at 385.0928 mass/charge (m/z) is assigned to the ferulic acid-ferulic acid dimer, while the m/z 586.1193 signal indicates the adduct presence. This statement is confirmed by the fragmentation step, which supports characteristics peaks ascribed to the original DPPH at m/z 195.9986 and m/z 225.9972. The peak m/z 778.1605 is attributed to the formation of a new compound (called radimerSB) that has never identified before. According to the reaction mechanism, the ferulic acid may provide antioxidant activity mainly by hydrogen-atom transfer reaction. Furthermore, we compare the antimicrobial action of ferulic acid and Trolox. We show that against ferulic acid prevents the crop growth of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The ferulic acid biological activities can be useful to develop new bio-based materials for technological applications (e.g., medical purposes). It is essential to understand the reaction mechanism between DPPH and antioxidants. The DPPH can quantify the concentration of antioxidants in plant extracts. The biological activities (antimicrobial, cytotoxicity, and others) of these extracts depend on the type and concentration of antioxidants and their reaction products.
Phenolic compounds have a great diversity of substances, ranging from simple molecules to complex polymers. Therefore, it has been a great challenge to relate the behavior these substances, which may ...cause variations in the results obtained. For this, the objective of this work was to evaluate the behavior of phenolic compounds belonging of different classes (hydroxybenzoic; hydroxycinnamic acids; flavonols; flavonols (catechins) and synthetic compounds) employing a new approach of analytical methods through sensitivity for each method. Results were statistically evaluated using principal component analysis (
PCA
) and
Tukey’s test
methodologies. The compounds sensitivity was obtained from the inclination of the standard curves constructed for each standard phenolic compound. Limits of detection (
LOD
) and quantification (
LOQ
) were calculated for each compound through the relation between uncertainty of the intercept (
Sa
) and slope (
b
), they presented different behavior comparing the methodologies, even compounds belonging to the same class. Moreover, 4-hydroxybenzoic acid compound did not show sensitivity to the methods 2,2-Diphenyl-1-picrylhydrazyl (DPPH
˙
) and
Ferric Reducing Ability Power (
FRAP
)
. Limits of detection and quantification also varied according to the compound and method investigated. The results interpretation was better examined applying the principal component analysis,
PCA
, rearranging the data in new coordinates. Hence, this study indicated that in general the
ORAC
methodology provides the best results in relation to the analysis of these different phenolic compounds and was indicated to evaluate the antioxidant capacity of most of the compounds analyzed. This correlation can be investigated in future studies, applying in real samples, indicating which methodology will be the most appropriate depending on the antioxidant composition in food.
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•Gelatin/polyphenolic tannin blends are prepared in deionized water.•Gelatin/tannin assemblies are prepared cooling blends.•We avoid the use of toxic chemistries (acids, bases, and ...crosslinking agents).•Porous, pH- and thermo-responsive assemblies are created, tuning the gelatin/tannin content.•The antimicrobial activity depends on the gelatin/tannin content in the blend.
We applied an amino-functionalized polyphenolic tannin derivative (TN), commercially called Tanfloc, to stabilize gelatin (GE) chains and provide physical assemblies. Zeta potential measurements showed that the TN presents an isoelectric point of 4.45. Hydrolyzed tannins comprise the TN structure, supporting negative Zeta potentials at pHs higher than 4.45. Aqueous GE (1.0, 2.0, 3.0, and 4.0 % wt/vol) and polyphenolic tannin derivative (TN, 4.6 g⋅L―1) mixtures in distilled water (pH 5.5, at 50 °C) provided physical assemblies after cooling at 4 °C. The thermosensitive hydrogels often showed gelation temperatures between 41 and 45 °C. A durable, porous, and organized structure with solid-liquid phase transition (gelation) higher than 60 °C was obtained at 4.0 % wt/vol GE and 50/50 GE/TN volume ratio at GE + TN equal to 134.0 mg. Viscoelastic materials were created by blending GE (4.0 % wt/vol) and TN (4.6 g⋅L―1) aliquots at GE/TN volume ratios equal to 90/10 vol/vol (assembly 4-90/10 at GE + TN equal to 212.3 mg) and 50/50 vol/vol (assembly 4/50/50 at GE + TN = 134.0 mg). A pure GE material showed the highest porosity (89 %). The TN presence reduced the material porosity to 65 % (assembly 4-90/10) and 63 % (assembly 4-50/50). The assembly 4-90/10 showed aqueous instability because the polymer blend had no enough TN to stabilize the GE chains. However, the assembly 4-90/10 had antimicrobial activities against Escherichia coli (E. coli) with minimal inhibitory and minimum bactericidal concentrations of 500 μg⋅ mL―1. The disk diffusion method showed that the assembly 4-90/10 provided an inhibition halo of 11 mm toward E. coli after 24 h of exposure at pH 6.0. GE/TN assemblies can provide physical hydrogels for biomedical applications (wound dressings).
