Charged Pectin Research Articles

Rapid alkalinization factor 22 has a structural and signalling role in root hair cell wall assembly.

Pressurized cells with strong walls make up the hydrostatic skeleton of plants. Assembly and expansion of such stressed walls depend on a family of secreted RAPID ALKALINIZATION FACTOR (RALF) peptides, which bind both a membrane receptor complex and wall-localized LEUCINE-RICH REPEAT EXTENSIN (LRXs) in a mutually exclusive way. Here we show that, in root hairs, the RALF22 peptide has a dual structural and signalling role in cell expansion. Together with LRX1, it directs the compaction of charged pectin polymers at the root hair tip into periodic circumferential rings. Free RALF22 induces the formation of a complex with LORELEI-LIKE-GPI-ANCHORED PROTEIN 1 and FERONIA, triggering adaptive cellular responses. These findings show how a peptide simultaneously functions as a structural component organizing cell wall architecture and as a feedback signalling molecule that regulates this process depending on its interaction partners. This mechanism may also underlie wall assembly and expansion in other plant cell types.

ITC study on the interaction of some bile salts with tragacanth, Arabic, and guar gums with potential cholesterol-lowering ability.

The urge of designing new safe and natural functional foods to control blood lipids and dispensable without the need of physician supervision, has increased especially after the coming into effect of the recent EU Commission regulation 2022/860, that regulates the consumption of "red yeast rice," made by fermentation of rice with Monascus purpureus, and perceived as a natural functional food, due to a health risk for frail consumers. The results of the present work are a part of the systematic study we are carrying out of the binding ability of some soluble dietary fibers (SDF) from different natural sources toward selected bile salts (BS). Measurements were carried out by isothermal titration calorimetry (ITC) with the idea to shed light on the mechanism, if any, by which they show cholesterol-lowering activity. Epidemiological studies are sometimes conflicting and offer only hypothesis about the mechanism of action, the most accredited being the reduction of reabsorption of BS in the gut. Previous measurements done on negatively charged pectin and alginate, showed specific binding interaction with monomer NaDC for pectin and no interaction at all for alginate. Chitosan, positively charged and soluble only at low pH, in 100 mM acetate buffer at pH = 3 shows strong exothermic interactions with NaTC and NaTDC. Here we considered two plant exudates (Arabic gum and tragacanth gum) and guar gum, extracted from guar beans, and their interaction with the same bile salts. ITC measurements do not evidence specific interactions between gums and the studied BS, so that their cholesterol lowering ability, if any, is due to a different mechanism very probably bound to the viscosity increase. Moreover, the addition of NaC, the most abundant BS in the bile, at very low concentration (under the cmc) causes a structural change of the solution. The obtained results seem to corroborate the hypothesis that the cholesterol lowering activity is related to the increase in viscosity of guar solution favored by NaC, the major component of the bile.

Enzyme-responsive food packaging system based on pectin-coated poly (lactic acid) nanofiber films for controlled release of thymol

Foodborne diseases caused by foodborne pathogens lead to serious harm to food safety and human health. This work fabricated an enzyme-responsive packaging film based on porous poly (lactic acid) (PLA) nanofibers modified by positively charged polyethyleneimine (PEI) and further to adsorb negatively charged pectin coating, which loaded with thymol (THY) for protecting fruits from microbial infection. The porous PLA nanofibers were fabricated by combining “Breath Figure” principle and electrospinning technique. The XPS and FTIR characterizations showed that PLA nanofiber membrane was successfully modified by PEI. The prepared nanofiber membrane significantly inhibited the growth of E. coli, S. aureus and Bacillus subtilis (＞95%), especially showed excellent antifungal activity against Aspergillus niger. The release of THY from pectin-coated porous nanofiber membrane (THY@PLA-PEI-Pectin) was triggered by pectinase, which was secreted by microorganisms from food contamination. Besides, the biocompatible THY@PLA-PEI-Pectin nanofiber membrane prolonged the shelf life of citrus. Therefore, this pectinase-responsive nanofiber membrane has desirable application prospects in the development of active or smart packaging systems.

Release of 5-FU loaded pectin/Fe3O4 from porous PBSA matrix under magnetic and electric fields

In this work, the porous poly(butylene succinate co adipate) (PBSA) was used as the drug matrix for transdermal drug delivery system (TDDS). The porous PBSA matrices were fabricated via solvent casting and particulate leaching method using Tween20 as a pore generator, and the matrices were capable of absorbing the drug solution within 3 s prior to the release. The Fe3O4 magnetic nanoparticles were successfully synthesized via co-precipitation method and successfully coated with pectin through the electrostatic attraction. The 5-fluorouracil, the model drug, was successfully loaded onto the pectin coated Fe3O4 magnetic nanoparticles through the hydrogen bonding. Under magnetic fields, the drug diffusion coefficient increased by the factors of 2 and 5 by the 157 and 247 mT permanent magnets, respectively, whereas the drug release duration was reduced. This was due to the magnetic attraction between the magnetic particles and the magnets. Under the combined electric voltage of 3 V and the magnetic flux of 157 mT, the drug diffusion coefficient increased and the release duration was reduced further, due to the combined driving forces between the magnetic attraction, the electrostatic repulsion of the negative charged pectin layer, and the electro-osmosis. The present work demonstrates the potentials and benefits of the porous matrices along with the combined magnetic and electric fields in the transdermal drug delivery.

Amphiphilic Alkylated Pectin Hydrogels for Enhanced Topical Delivery of Fusidic Acid: Formulation and In Vitro Investigation

Hydrogels constructed of amphiphilically modified polysaccharides have attracted a lot of interest because of their potential to augment drug diffusion over the skin. This research describes the synthesis of amphiphilic alkylated pectin via glycidyl tert-butyl ether modification (alkylation degree 15.7%), which was characterized using spectroscopic and thermal analysis techniques and then formulated into hydrogels for the study of their potential in regulating fusidic acid diffusion topically. The hydrogels were formulated by the ionic interaction of negatively charged pectin and positively charged crosslinker CaCl2, with a reported fusidic acid loading degree of 93–95%. Hydrogels made of alkylated pectin showed a lower swelling percentage than that of native pectin, resulting in a slower fusidic acid release. The influence of pH on the swelling percentage and drug release was also investigated, with results revealing that greater pH enhanced swelling percentage and drug release. The in vitro interactions with HaCaT cells revealed negligible cytotoxicity under application-relevant settings. Utilizing Franz diffusion cells, the alkylated pectin hydrogels caused fusidic acid to penetrate the Strat-M® membrane at a 1.5-fold higher rate than the native pectin hydrogels. Overall, the in vitro results showed that alkylated pectin hydrogels have a lot of promise for topical distribution, which needs further investigation.

Quaternized curdlan/pectin polyelectrolyte complexes as biocompatible nanovehicles for curcumin

In this study, a positively charged quaternized curdlan (Qcurd) was used to fabricate polyelectrolyte complex nanoparticles (PEC NPs) with a negatively charged pectin via electrostatic complexation. Results showed that the Qcurd/pectin PEC NPs prepared with 0.5 mg/mL Qcurd and pectin solutions, 1:2 pectin/Qcurd mass ratio, and pH 4.0 in the absence of NaCl were characterized by a spherical morphology in nanoscale, an average particle size of 68 nm, and good dispersibility in aqueous solutions. Curcumin was encapsulated in the Qcurd/pectin PEC NPs through hydrogen bonding with an encapsulation efficiency of ∼82%, a loading content of 13%, and a pH-dependent controlled release. Curcumin-loaded PEC NPs exhibited a significantly enhanced water solubility, excellent free radical scavenging ability and antioxidant capacity in vitro as compared with those of free curcumin.

Structural and dynamical characterization of the pH-dependence of the pectin methylesterase–pectin methylesterase inhibitor complex

Pectin methylesterases (PMEs) catalyze the demethylesterification of pectin, one of the main polysaccharides in the plant cell wall, and are of critical importance in plant development. PME activity generates highly negatively charged pectin and mutates the physiochemical properties of the plant cell wall such that remodeling of the plant cell can occur. PMEs are therefore tightly regulated by proteinaceous inhibitors (PMEIs), some of which become active upon changes in cellular pH. Nevertheless, a detailed picture of how this pH-dependent inhibition of PME occurs at the molecular level is missing. Herein, using an interdisciplinary approach that included homology modeling, MD simulations, and biophysical and biochemical characterizations, we investigated the molecular basis of PME3 inhibition by PMEI7 in Arabidopsis thaliana Our complementary approach uncovered how changes in the protonation of amino acids at the complex interface shift the network of interacting residues between intermolecular and intramolecular. These shifts ultimately regulate the stability of the PME3-PMEI7 complex and the inhibition of the PME as a function of the pH. These findings suggest a general model of how pH-dependent proteinaceous inhibitors function. Moreover, they enhance our understanding of how PMEs may be regulated by pH and provide new insights into how this regulation may control the physical properties and structure of the plant cell wall.

Biocompatible Polyelectrolyte Complex Nanoparticles from Lactoferrin and Pectin as Potential Vehicles for Antioxidative Curcumin.

Polyelectrolyte complex nanoparticles (PEC NPs) were fabricated via electrostatic interactions between positively charged heat-denatured lactoferrin (LF) particles and negatively charged pectin. The obtained PEC NPs were then utilized as curcumin carriers. PEC NPs were prepared by mixing 1.0 mg/mL solutions of heat-denatured LF and pectin at a mass ratio of 1:1 (w/w) in the absence of NaCl at pH 4.50. PEC NPs that were prepared under optimized conditions were spherical in shape with a particle size of ∼208 nm and zeta potential of ∼-32 mV. Hydrophobic curcumin was successfully encapsulated into LF/pectin PEC NPs with high encapsulation efficiency (∼85.3%) and loading content (∼13.4%). The in vitro controlled release and prominent antioxidant activities of curcumin from LF/pectin PEC NPs were observed. The present work provides a facile and fast method to synthesize nanoscale food-grade delivery systems for the improved water solubility, controlled release, and antioxidant activity of hydrophobic curcumin.

The effect of polysaccharides on the ability of whey protein gels to either store or dissipate energy upon mechanical deformation

The addition of polysaccharides to proteins during gel formation can alter the mechanical and textural properties of the resultant gels. However, the effect of addition of different polymers on mechanical properties of whey protein (WP) gels including their ability to elastically store energy, often measured in terms of the recoverable energy (RE), or dissipate energy, has not been fully reported. In this paper heat-induced WP gels containing high (HM) or low (LM) methylated negatively charged pectin or the neutral pullulan were prepared to study how the addition of polysaccharides to WP affects the mechanical properties of the formed gels. These gels were subjected to uniaxial compression and mechanical properties, including RE, were evaluated. The addition of pullulan to WP did not enhance the RE, whereas an increase in LM pectin resulted in higher RE. For gels containing HM pectin, the presence of the polymer induced an initial decrease of the RE. Nevertheless, RE increased with further increase in pectin concentration. These findings indicate that the addition of polysaccharides to whey proteins during gel formation results in changes in the RE but to different extent for different polymers. The results from this study suggest that the addition of polysaccharides to WP can be used as a tool to modulate the ability of whey protein gels to elastically store energy upon mechanical deformation.

Influence of charge density and calcium salt on stiffness of polysaccharides multilayer film

Abstract Polysaccharide multilayer film consisting of negatively charged pectin (PEC) and positively charged chitosan (CHI) is built by electrostatic self-assembly onto ellipsoidal iron oxide particles. The thickness growth and electrical properties of the PEC/CHI multilayer film are followed using electric light scattering method and electrophoresis. The main focus is on how the PEC and CHI charge density and addition of divalent calcium salt affect the stiffness of the PEC/CHI multilayer film. We found an excess of positive charges within the PEC/CHI film when it is constructed from highly charged CHI and less charged PEC (at pH 4). The excess of positive charge within the film causes a decrease in the amplitude of the electro-optical effect at high electric fields, more expressive for the films ending in CHI. This is related to operation of an elasto-hydrodynamic effect (dominating at strong fields), which favors perpendicular orientation of “soft” particles with respect to the external electric field. Addition of Ca2+ ions to the films ending in PEC causes small increase in the amplitude of the electro-optical effect at high fields, corresponding to an increase in the film stiffness.

Pectin/lysozyme bilayers layer-by-layer deposited cellulose nanofibrous mats for antibacterial application.

Positively charged lysozyme (LZ) and negatively charged pectin, were alternately deposited on the surface of the cellulose nanofibrous mats by layer-by-layer (LBL) self-assembly technique. Scanning electron microscopy images showed that the nanofibers were orderly and compactly arrayed after LBL. Besides, as the number of LZ/pectin bilayers increased, the average diameter of nanofibers increased. LZ has assembled on the cellulose mats successfully, which was confirmed by X-ray photoelectron spectroscopy analysis. Thermal gravimetric analysis results showed that the thermal properties of LZ/pectin films coated mats was better than that of the unmodified cellulose mats. Importantly, the results of the bacterial inhibition test for LBL structured mats and cellulose mats indicated that the nanofibrous mats coated by 10.5 LZ/pectin bilayers (with LZ on the outmost layer) possessed the strongest inhibitory effect against both Escherichia coli and Staphylococcus aureus.

Physical characteristics of submicron emulsions upon partial displacement of whey protein by a small molecular weight surfactant and pectin addition

O/W emulsions (6wt.% olive oil) were prepared at pH3.3 using different WPI:Tween 20 weight ratios (1:0, 3:1, 1:1, 1:3, 0:1) at 1wt.% total concentration. The emulsion droplet size was found to decrease with an increase in Tween 20. A minimum droplet size of d3,2 300nm was found for Tween systems alone, similar to that found (360nm) for a 1:1 WPI:Tween 20 combination (p<0.05). This specific composition showed a value for the interfacial tension close to that of Tween 20 alone. However, the emulsions presented low stability regardless of the WPI:Tween 20 ratio. To increase their stability, pectin was added, in various concentrations (0.2, 0.4 and 0.6wt.%), using the Layer by Layer technique. In the presence of pectin, the ζ-potential of the oil droplets became negative; indicating that negatively charged pectin was absorbed onto the positively-charged droplet surface forming a secondary layer. The additional layer resulted in a wide range of emulsion stability. For all pectin concentrations, the 1:1 ratio of WPI:Tween 20 showed the highest stability. In most emulsions, extensive aggregation of oil droplets was observed, and their viscosity increased. Insufficient amounts of pectin to form the secondary layers led to bridging flocculation phenomena of oppositely charged pectin and proteins, leading to aggregation of the oil droplets. The higher the concentration of pectin, the greater the stability of the emulsion due to higher viscosity. All in all, the addition of a second layer consisting of pectin can be used to increase the stability of an emulsion containing emulsion droplets in the sub-micron range.

Friction properties of oral surface analogs and their interaction with polysaccharide/MCC particle dispersions

To optimize food products to better accommodate food product acceptance by end consumers and health or ecological regulations, it is necessary to gain a reliable view of the process that occurs during mastication of products in the oral cavity. The physical description of the mechanical responses due to oral processing is required for a more effective prediction in product (re)formulation. The aim of this work is to derive such an adequate and relevant methodology. For this purpose a tribological and rheological study of polysaccharide solutions was employed using a set of different rubbers that mimic different soft (oral) surfaces and to relate these measurements to material surface properties, as roughness, hydrophobicity and elasticity. The polysaccharides chosen, locust bean gum, pectin and xanthan, represent important components in food products.It is shown that the nature (hardness or roughness) of a surface under good lubrication conditions is not that important. Therefore, in developing new food products it may be of prime importance to control the lubrication properties rather than focus on adaptation to oral surface characteristics, like the consequences of human aging. Xanthan is more effective as lubricant than the negatively charged pectin, while locust bean gum is the worst lubricant that was tested. No clear relation with the apparent contact angle could be made between friction and the aqueous solutions tested.The presence of hard particles on friction is predominantly observed at relatively low entrainment speed (below about 50mm/s) and is most explicitly detectable when lubrication is poor (as for locust bean gum). The MCC particles used in this study may not fit in the surface asperities and thereby enhance surface roughness, which results in extended boundary regime of the Stribeck-curve. Tribology is shown to be useful to detect particles dispersed in a solution, but the better the lubricant the more difficult the detection of such particles will be. Alternatively, this work shows that food products characterized by low friction coefficient can be mixed with elongated particles without large influence on their lubrication properties. This insight might provide openings in reformulation-strategies not only in food but also in pharmacy applications.

Covalent TiO2/pectin microspheres with Fe3O4 nanoparticles for magnetic field-modulated drug delivery

Covalent TiO2-co-pectin microspheres containing Fe3O4 nanoparticles were developed through an ultrasound-induced crosslinking/polymerization reaction between the glycidyl methacrylate from vinyl groups in TiO2 and in pectin. ζ-potentials became less negative in the nanostructured microspheres, caused by the presence of both inorganic particles in the negatively charged pectin. The nanostructured pectin microspheres showed an amoxicillin release rate slower than that of pure pectin microspheres. The proposed microspheres were found to be a sustained release system of amoxicillin in the acid medium. Furthermore, the antibiotic release may be modulated by exposition of the microspheres to a remote magnetic field. In practical terms, the nanostructured microspheres could deliver a larger proportion of their initial load to specific site of action. The cytotoxic concentrations for 50% of VERO cells (CC50), calculated as the concentration required to reduce cell viability by 50% after 72h of incubation, for pectin-only microspheres and nanostructured pectin microspheres were 217.7±6.5 and 121.5±4.9μgmL−1, respectively. The obtained CC50 values indicated acceptable cytotoxic levels for an incubation period of 72h, showing that the pectin microspheres have a great pharmacological potential for uses in biological environments, even after the introduction of both Fe3O4 and TiO2.

Acid-induced gelation properties of heated whey protein−pectin soluble complex (Part II): Effect of charge density of pectin

As a direct continuation of the first part of our study, here we investigate the effect of charge density of pectin on acid-induced gelation properties of heated whey protein–pectin soluble complex which was formed by heating protein and pectin together at pH 7.0 and 85 °C for 30 min. The gelation properties of complex were also compared with polymer/pectin, where whey protein and pectin were heated separately and then mixed together before acid-induced gelation. Four different types of pectin with charge density ranging from low to high were chosen. For pectin with high charge density, complex gels showed enhanced gel strength and water holding capacity compared to polymer/pectin gels. For those with low charge density pectin, polymer/pectin could not form gel network at highest pectin concentrations, whereas complex still formed gel at high pectin concentrations and showed improved water holding capacity at low pectin concentrations. Confocal micrograph showed pronounced difference in gel microstructure between complex and polymer/pectin gels. An obvious increase in the coarsening of the protein network was observed as pectin concentration increased from 0.1% to 0.5% for polymer/pectin gels. Complex gels showed much smoother network with less phase separation. At 0.25% pectin a change from a homogeneous to a coarse strand, phase separated microstructure upon decreasing charge density of pectin was observed for polymer/pectin gels, while complex gels were homogeneous even with low charged pectin. Results from scanning electron microscopy confirmed that complex gels were composed of larger protein strands and higher interconnectivity between biopolymers due to higher degree of interaction between protein and pectin.

Effect of calcium ions and pH on the structure and rheology of carrot-derived suspensions

In the present work, the role of calcium ions (Ca2+) in the rheological behaviour of carrot-derived purées was investigated. Therefore, purées based on carrots containing pectin with different degree of methoxylation were prepared and the effects of Ca2+ addition in excess on the rheological properties of these purées were studied at different pH. More specifically, it was assessed if the purée stiffness and strength could be influenced by Ca2+ addition. Ion addition caused a decrease in both network stiffness and strength, in particular at pH values above 4.5. By separating the particle phase from the serum, and characterizing the rheology of both phases as a function of pectin degree of methoxylation, Ca2+ addition in excess and pH, it was concluded that the particle phase rather than the serum phase is affected by ion addition. Immunolabeling of the carrot-derived particles with anti-pectin antibodies showed the presence of non-methoxylated residues at the particle surfaces, which will be charged at specific pH. Hence, the calcium ions may compress the electrical double layer around the particles whereby they can approach each other more closely. The latter mechanism was confirmed by the relation between the phase volume and the rheological parameters. Rather than being involved in Ca2+ cross-link formation thus enhancing the pectin network in carrot-derived purées, it turned out that Ca2+ screens the negatively charged pectin at the surface of the particles whereby the rheological characteristics of these suspensions, such as the yield stress and storage modulus, are reduced and the flow is facilitated.

Pharmacokinetics and biodistribution of negatively charged pectin nanoparticles encapsulating paclitaxel.

Pectin, a naturally occurring biopolymer has been found to have increasing applications in the pharmaceutical and biotechnology industry. Sugars with their three-dimensional structures are important for many biological functions. We report preparation of negatively charged pectin nanoparticles encapsulating paclitaxel, a broad-spectrum anticancer drug for possible therapeutic applications. The mean diameter of the nanoparticles was ~300–350 nm with an encapsulation efficiency ~17 %. The TEM studies indicated that the particles were spherical in shape and their sizes are in unison with the DLS size spectra. The surface charge of pectin polymer was −5 mV and of nanoparticles were ~ −32 mV. The enhanced surface charge shows greater stability. The high electrophoretic mobility of ~3.5 to 1.5 μmcm/Vs confirmed the nano-size of particles. We compared the cytotoxic effect of paclitaxel (Pax) per se, pectin nanoparticles (PPN), and pectin chains on Hep G2, hepatic carcinoma cell line. Dose-dependent cytotoxicity was observed, wherein ~21.7 ± 3.2 % cytotoxicity was observed by PPN, but Pax per se showed ~55.6 ± 3.5 % cytotoxicity in a 72-h assay. The pharmacokinetics and biodistribution studies on Balb/c mice indicated that the nanoparticles had prolonged plasma retention of the drug with major accumulation in liver tissue after an i.v. tail vein injection of 20 mg/kg drug. The rank order of concentration are as follows, i.e., liver > kidney > lung > spleen for the PPN and spleen > liver > kidney ≥ lung for Pax per se. The in vitro studies clearly indicated that the efficacy of the drug was not compromised by encapsulation, making it a good candidate to deliver biopharmaceuticals. Nanoparticles produced free radicals in the free cell system and this ability caused oxidative stress, which may give rise to inflammation, cell destruction, and genotoxicity. Thus, the results obtained in this study holds great promise for pectin nanoparticles to be exploited for passive delivery of paclitaxel to tumor tissues, in particular, liver cancers.

Novel strategies for fabricating reduced fat foods: Heteroaggregation of lipid droplets with polysaccharides

This study describes the formation of emulsion-based materials with novel textural characteristics by controlled heteroaggregation of food-grade colloidal particles and polymers. Heteroaggregation was induced by mixing a suspension of colloidal particles (β-lactoglobulin-coated lipid droplets) with a solution of polymer molecules (pectin) under conditions where the particles and polymers had similar charges (pH 7) or opposite charges (pH 4). The mean particle size, microstructure, flow behavior, and shear modulus of the mixtures formed depended on particle-to-polymer ratio and solution pH. At pH 4, negatively charged pectin molecules were attracted to the surfaces of positively charged protein-coated droplets leading to particle aggregation, increased viscosity, and gel formation, which were attributed to bridging flocculation. At pH 7, pectin molecules were not attracted to the droplet surfaces, but there was still an increase in emulsion viscosity and gel strength above a critical pectin concentration due to depletion flocculation. Bridging flocculation (pH 4) led to more extensive particle aggregation, higher viscosities, and stronger gels than depletion flocculation (pH 7). The presence of pectin in the emulsions had little impact on their microstructure or lipid digestion rate in a simulated gastrointestinal model. This study has important implications for the creation of reduced fat foods, and the development of foods, cosmetics, personal care, and other products with novel properties.

Complexation of Ferric Oxide Particles with Pectins of Ordered and Random Distribution of Charged Units

Complexation between ferric oxide particles and pectins with degree of methylation 50% but having ordered or random arrangement of free carboxyl groups is investigated by electric light scattering and electrophoresis. The influence of charge distribution in pectin chain on the electrical properties of oppositely charged oxide particles and stability of their suspensions is examined as a function of pectin concentration. Although the difference in charge density of pectin samples is ~5%, we found small but measurable difference in the behavior of both oxide/pectin complexes. This is attributed to condensation of counterions near the chains of pectin with ordered distribution of charges, leading to a decrease in the effective charge density and to a corresponding decrease in the contour length of the adsorbing pectin chains. Two parameters are sensitive to the conformation of the adsorbed chains in suspensions, stabilized by pectin adsorption (at particle charge reversal). The electro-optical effect is higher for the complex with less charged pectin, which is explained with larger amount of chains, adsorbed in more coiled conformation than the chains of pectin with random distribution of free carboxyl groups. The addition of small amounts of CaCl(2) has no significant influence on the thickness of the layer from the less charged pectin, in agreement with a more compact conformation of the chains in this adsorbed layer. In contrast, the thickness of the layer from pectin with random distribution of charged groups decreases with increasing concentration of CaCl(2), indicating a more loose structure of this layer.

Gelatin–pectin composite films from polyion-complex hydrogels

Preparation and properties of composite films from gelatin and low-methoxyl pectin from simultaneous reversible and permanent polyion-complex hydrogels are presented. Ionic interactions between positively charged gelatin and negatively charged pectin produce reversible physical hydrogels with homogeneous molecular arrangement that improve both mechanical and water resistance but do not alter thermal stability relative to single polymer gels. Subsequent addition of 0.3 weight percent (wt.%) glutaraldehyde crosslinks gelatin heterogeneously, due to the presence of domains with non-uniform crosslinking, as revealed by the structural analysis. Resulting interspersed permanent chemical hydrogel showed a decreased swelling attitude by nearly 10 fold relative to films from gelatin alone and further improved mechanical performance (tensile strength and elongation at break). Results demonstrate that simultaneously exploiting the specific reactivity provided by the functional groups of both biopolymers can be used to create unique new structures with improved properties and offer potential for tailoring these to a wide range of targeted applications.