Alginate/chitosan polyelectrolyte complexes: A comparative study of the influence of the drying step on physicochemical properties

Physical characterization, biocompatibility, and antimicrobial activity of polyvinyl alcohol/sodium alginate blend doped with TiO2 nanoparticles for wound dressing applications

The ability of wound dressing materials to tackle skin pathogens colonization that is associated with open wound infections is limited. Recently, green-synthesized metal oxide nanoparticles has received a lot of attention to overcome this limitation. However, titanium dioxide nanoparticles (TiO2-NPs) exhibit exceptional antibacterial properties. In this work, several concentrations (0, 1, 3, and 5 wt.%) of TiO2 NPs prepared using Aloe vera leaf extract were added to a blend of polyvinyl alcohol and sodium alginate (PVA:SA). This nanocomposite was designed to enhance the healing process of wounds. The interaction between the PVA:SA composite and the TiO2 NPs was confirmed by FTIR. The thermal behavior of the nanocomposite films was investigated using DSC and TGA. The experimental results indicate that the glass transition temperatures of the nanocomposites increased by increasing the added amount of TiO2 NPs to be 53.7 °C (1 wt.%), 55.8 °C (3 wt.%), and 60.6 °C (5 wt.%), which were consistently lower than the glass transition temperature of the matrix material (69.6 °C). The Dynamic Mechanical Analysis was examined. The nanocomposite doped with 5 wt.% of TiO2 NPs detected a high storage modulus (21.6 × 108). Based on swelling and degradation studies, the prepared PVA:SA:TiO2 nanocomposite films have an excellent swelling rate, and the inclusion of TiO2 NPs increases the stability of the polymeric matrix. The PVA:SA:TiO2 nanocomposite films exhibited a superior antibacterial efficacy against Gram-positive bacteria such as Bacillus cereus and Staphylococcus aureus, compared to their effectiveness against Gram-negative bacteria like Escherichia coli. Moreover, the nanocomposite films were biocompatible with Human Skin Fibroblast. Therefore, the developed PVA:SA:TiO2 nanocomposite films suit wound dressing applications.

3D printed polylactic acid-based nanocomposite scaffold stuffed with microporous simvastatin-loaded polyelectrolyte for craniofacial reconstruction

Critical sized craniofacial defects are among the most challenging bone defects to repair, due to the anatomical complexity and aesthetic importance. In this study, a polylactic acid/hardystonite-graphene oxide (PLA/HTGO) scaffold was fabricated through 3D printing. In order to upgrade the 3D printed scaffold to a highly porous scaffold, its channels were filled with pectin-quaternized chitosan (Pec-QCs) polyelectrolyte solution containing 0 or 20 mg/mL of simvastatin (Sim) and then freeze-dried. These scaffolds were named FD and FD-Sim, respectively. Also, similar PLA/HTGO scaffolds were prepared and dip coated with Pec-QCs solution containing 0 or 20 mg/mL of Sim and were named DC and DC-Sim, respectively. The formation of macro/microporous structure was confirmed by morphological investigations. The release of Sim from DC-Sim and FD-Sim scaffolds after 28 days was measured as 77.40 ± 5.25 and 86.02 ± 3.63 %, respectively. Cytocompatibility assessments showed that MG-63 cells had the highest proliferation, attachment and spread on the Sim containing scaffolds, especially FD-Sim. In vivo studies on a rat calvarial defect model revealed that an almost complete recovery occurred in the group treated with FD-Sim scaffold after 8 weeks and the defect was filled with newly formed bone. The results of this study acknowledge that the FD-Sim scaffold can be a perfect candidate for calvarial defect repair.

The effect of synthesis conditions and process parameters on aerogel properties

Aerogels are remarkable nanoporous materials with unique properties such as low density, high porosity, high specific surface area, and interconnected pore networks. In addition, their ability to be synthesized from various precursors such as inorganics, organics, or hybrid, and the tunability of their properties make them very attractive for many applications such as adsorption, thermal insulation, catalysts, tissue engineering, and drug delivery. The physical and chemical properties and pore structure of aerogels are crucial in determining their application areas. Moreover, it is possible to tailor the aerogel properties to meet the specific requirements of each application. This review presents a comprehensive review of synthesis conditions and process parameters in tailoring aerogel properties. The effective parameters from the dissolution of the precursor step to the supercritical drying step, including the carbonization process for carbon aerogels, are investigated from the studies reported in the literature.

Construction of TiO2/starch nanocomposite cryogel for ethylene removal and banana preservation

Perishability caused by natural plant hormone ethylene has attracted great attention in the field of fruit and vegetable (F&V) preservation. Various physical and chemical methods have been applied to remove ethylene, but the eco-unfriendliness and toxicity of these methods limit their application. Herein, a novel starch-based ethylene scavenger was developed by introducing TiO₂ nanoparticles into starch cryogel and applying ultrasonic treatment to further improve ethylene removal efficiency. As a porous carrier, the pore wall of cryogel provided dispersion space, which increased the area of TiO₂ exposed to UV light, thereby endowing starch cryogel with ethylene removal capacity. The photocatalytic performance of scavenger reached the maximum ethylene degradation efficiency of 89.60 % when the TiO₂ loading was 3 %. Ultrasonic treatment interrupted starch molecular chains and then promoted their rearrangement, increasing the material specific surface area from 54.6 m²/g to 225.15 m²/g and improving the ethylene degradation efficiency by 63.23 % compared with the non-sonicated cryogel. Furthermore, the scavenger exhibits good practicability for removing ethylene as a banana package. This work provides a new carbohydrate-based ethylene scavenger, utilizing as a non-food contact inner filler of F&V packaging in practical applications, which exhibits great potential in F&V preservation and broadens the application fields of starch.

Development of pH-Responsive Polypills via Semi-Solid Extrusion 3D Printing

The low bioavailability of orally administered drugs as a result of the instability in the gastrointestinal tract environment creates significant challenges to developing site-targeted drug delivery systems. This study proposes a novel hydrogel drug carrier using pH-responsive materials assisted with semi-solid extrusion 3D printing technology, enabling site-targeted drug release and customisation of temporal release profiles. The effects of material parameters on the pH-responsive behaviours of printed tablets were analysed thoroughly by investigating the swelling properties under both artificial gastric and intestinal fluids. It has been shown that high swelling rates at either acidic or alkaline conditions can be achieved by adjusting the mass ratio between sodium alginate and carboxymethyl chitosan, enabling site-targeted release. The drug release experiments reveal that gastric drug release can be achieved with a mass ratio of 1:3, whilst a ratio of 3:1 allows for intestinal release. Furthermore, controlled release is realised by tuning the infill density of the printing process. The method proposed in this study can not only significantly improve the bioavailability of oral drugs, but also offer the potential that each component of a compound drug tablet can be released in a controlled manner at a target location.

Fabrication and Evaluation of Polyvinyl Alcohol/Corn Starch/Patchouli Oil Hydrogel Films Loaded with Silver Nanoparticles Biosynthesized in Pogostemon cablin Benth Leaves' Extract

Research on the manufacture of hydrogel films from polyvinyl alcohol, corn starch, patchouli oil, and silver nanoparticles, (PVA/CS/PO/AgNPs, respectively) was completed. The silver nanoparticles used in this study resulted from green synthesis using local patchouli plants (Pogostemon cablin Benth). Aqueous patchouli leaf extract (APLE) and methanol patchouli leaf extract (MPLE) are used in the synthesis of phytochemicals (green synthesis), which are then blended in the production of PVA/CS/PO/AgNPs hydrogel films, which are then cross linked with glutaraldehyde. The results demonstrated that the hydrogel film was flexible, easy to fold, and free of holes and air bubbles. The presence of hydrogen bonds between the functional groups of PVA, CS, and PO was revealed using FTIR spectroscopy. SEM analysis revealed that the hydrogel film was slightly agglomerated and did not exhibit cracking or pinholes. The analysis of pH, spreadability, gel fraction, and swelling index showed that the resulting PVA/CS/PO/AgNP hydrogel films met expected standards except for the organoleptic properties of the resulting colors, which tended to be slightly darker in color. The formula with silver nanoparticles synthesized in methanolic of patchouli leaf extract (AgMENPs) had the highest thermal stability compared to hydrogel films with silver nanoparticles synthesized in aqueous of patchouli leaf extract (AgAENPs). The hydrogel films can be safely used up to 200 °C. The antibacterial studies revealed that the films inhibited the growth of both Staphylococcus aureus and Staphylococcus epidermis, as determined by the disc diffusion method, with the best antibacterial activity being against Staphylococcus aureus. In conclusion, the hydrogel film F₁, loaded with silver nanoparticles biosynthesized in aqueous of patchouli leave extract (AgAENPs) and light fraction of patchouli oil (LFoPO) performed the best activity against both Staphylococcus aureus and Staphylococcus epidermis.

Cell Immobilization Using Alginate-Based Beads as a Protective Technique against Stressful Conditions of Hydrolysates for 2G Ethanol Production

The development of biorefineries brings the necessity of an efficient consumption of all sugars released from biomasses, including xylose. In addition, the presence of inhibitors in biomass hydrolysates is one of the main challenges in bioprocess feasibility. In this study, the application of Ca-alginate hybrid gels in the immobilization of xylose-consuming recombinant yeast was explored with the aim of improving the tolerance of inhibitors. The recombinant yeast Saccharomyces cerevisiae GSE16-T18SI.1 (T18) was immobilized in Ca-alginate and Ca-alginate–chitosan hybrid beads, and its performance on xylose fermentation was evaluated in terms of tolerance to different acetic acid concentrations (0–12 g/L) and repeated batches of crude sugarcane bagasse hemicellulose hydrolysate. The use of the hybrid gel improved yeast performance in the presence of 12 g/L of acetic acid, achieving 1.13 g/L/h of productivity and reaching 75% of the theoretical ethanol yield, with an improvement of 32% in the xylose consumption rate (1:1 V_beads/V_medium, 35 °C, 150 rpm and pH 5.2). The use of hybrid alginate–chitosan gel also led to better yeast performance at crude hydrolysate, yielding one more batch than the pure-alginate beads. These results demonstrate the potential of a hybrid gel as an approach that could increase 2G ethanol productivity and allow cell recycling for a longer period.

Chitosan-Based Polyelectrolyte Complex Cryogels with Elasticity, Toughness and Delivery of Curcumin Engineered by Polyions Pair and Cryostructuration Steps

Chitosan (CS)-based drug delivery systems (DDSs) are often stabilized by chemical cross-linking. A much more friendly approach to deliver drugs in a controlled manner is represented by polyelectrolyte complexes (PECs) physically stabilized by spontaneous interactions between CS and natural or synthetic biocompatible polyanions. PECs with tunable structures, morphologies, and mechanical properties were fabricated in this paper by an innovative and sustainable strategy. Carboxymethyl cellulose (CMC) or poly(2-acrylamido-2-methylpropanesulfonate sodium salt) were used as aqueous solutions, while CS microparticles were evenly dispersed in the polyanion solution, at pH 6.5, where CS was not soluble. Cryostructuration of the dispersion in two steps (5 min at −196 °C, and 24 h at −18 °C), and freeze-drying at −55 °C, 48 h, conducted to pre-PEC cryogels. Next step was rearrangement of complementary polyions and the complex formation inside the pore walls of cryogels by exposure of the pre-PECs at a source of H⁺. PEC cryogels with impressive elasticity and toughness were engineered in this study by multiple-cryostructuration steps using CMC as polyanion with a molar mass of 250 kDa and an optimum concentration of polyanion and polycation. The performances of PEC cryogels in sustained delivery of anti-inflammatory drugs such as curcumin were demonstrated.

Natural Polymers Used in Edible Food Packaging—History, Function and Application Trends as a Sustainable Alternative to Synthetic Plastic

In this review, a historical perspective, functional and application trends of natural polymers used to the development of edible food packaging were presented and discussed. Polysaccharides and proteins, i.e., alginate; carrageenan; chitosan; starch; pea protein, were considered. These natural polymers are important materials obtained from renewable plant, algae and animal sources, as well as from agroindustrial residues. Historically, some of them have been widely used by ancient populations for food packaging until these were replaced by petroleum-based plastic materials after World War II. Nowadays, biobased materials for food packaging have attracted attention. Their use was boosted especially because of the environmental pollution caused by inappropriate disposal of plastic packaging. Biobased materials are welcome to the design of food packaging because they possess many advantages, such as biodegradability, biocompatibility and low toxicity. Depending on the formulation, certain biopolymer-based packaging may present good barrier properties, antimicrobial and antioxidant activities Thus, polysaccharides and proteins can be combined to form diverse composite films with improved mechanical and biological behaviors, making them suitable for packaging of different food products.

Preparation and Characterization of Chitosan/Bentonite Composites for Cr (VI) Removal from Aqueous Solutions

Chitosan/bentonite composites (CSBT) prepared by physical gelation were tested for the adsorption of Cr (VI) from aqueous solutions in this work. The composites were prepared at a mass ratio from 2 : 1 to 1 : 2, and a composite of 1 : 1 was found to be most suitable for efficient Cr (VI) removal. The influencing parameters, including temperature, adsorbent dose, and pH, were statistically optimized using response surface methodology (RSM) for the removal of Cr (VI). The pH was found to be the limiting factor during the adsorption process, and under the optimal conditions, namely, adsorbent dose of 400 mg/L, $\text{pH}=3$ , and temperature of 298 K, 87.61% Cr (VI) would be removed expectantly. The mechanism of Cr (VI) removal by CSBT was discussed, and the protonation of amino groups on chitosan followed by the combination of -NH3+ and anionic hexavalent chromium was the primary driving force. In addition, the removal of Cr (VI) onto CSBT was monolayer adsorption with a maximum adsorption capacity of 133.85 mg/g by the Langmuir isotherm. CSBT follows a pseudosecond-order kinetic model, and within 1.5 h, adsorption was observed to reach equilibrium. The calculated thermodynamic functions clarified that the adsorption process was exothermic and spontaneous below 312.60 K. CSBT could be regenerated after desorption by 0.5 mol/L NaOH solutions and exhibited superior reusability after six cycles. This study demonstrated composites of chitosan/bentonite as eco-friendly bioadsorbents for the removal of Cr (VI) from aqueous environments.

Simple ultrasonic-assisted approach to prepare polysaccharide-based aerogel for cell research and histocompatibility study

Salecan, a water-soluble microbial polysaccharide with attractive biocompatible characteristics, is very suitable for aerogel fabrication. However, the practical application of salecan-based aerogels for cell culture was limited by complicated preparation method, lack of cell anchorage signals, and the ability to modulate this properly. Here, a smart aerogel was designed by ultrasonic-assisted self-assembly of salecan and cationic starch (CAS) without any organic and toxic crosslinkers. The ultrasound waves generated a marked impact on self-assemble process by means of ultrasonic cavitation. Aerogel network was produced by strong electrostatic attractions between the polysaccharides. Especially, salecan/CAS ratio can be precisely modulated to tailor the hydrophilicity, mechanical stiffness, and morphologic property. The specific surface area of the aerogels gradually increased with the increase in salecan/CAS ratio. These aerogels were non-cytotoxic, and the incorporation of salecan into them promoted cell-matrix interactions by directionally supporting cell adhesion and proliferation. Most strikingly, in vivo experiment revealed that the histological features in the main organs of the mice were similar to those observed in the PBS-treated control group, and no sign of the histopathological abnormality or tissue destruction was observed, indicating the excellent histocompatibility of the aerogels. This study offered a new and powerful avenue to fabricate functional biomaterial.

Physicochemical features assessment of acemannan-based ternary blended films for biomedical purposes

The exploitation of natural origin macromolecules, as complex physical mixtures or drugs, increases in biomedical or tissue engineering (TE) solutions. Aloe Vera is a highly explored medicinal plant, from which the main polysaccharide is acemannan (ACE). The ACE combination with chitosan and alginate results in interactions that lead to mixed junction zones formation, predicting membrane functionality improvement. This work proposes the development and characterization of ACE-based blended films as a promising strategy to design a nature-derived bioactive platform. The results confirmed that stable complex polyelectrolyte structures were formed through different intermolecular interactions. The films present good dimensional stability, flexibility, an adequate swelling ability with mostly radial water uptake, and a sustainable ACE release to the medium. Positive biological performance of the ACE-based blended films with L929 cells also suggested that they can be applied in TE solutions, with the potential to act as bioactive topical platforms.

Polysaccharide-Based Aerogel Production for Biomedical Applications: A Comparative Review

A comparative analysis concerning bio-based gels production, to be used for tissue regeneration, has been performed in this review. These gels are generally applied as scaffolds in the biomedical field, thanks to their morphology, low cytotoxicity, and high biocompatibility. Focusing on the time interval 2015-2020, the production of 3D scaffolds of alginate, chitosan and agarose, for skin and bone regeneration, has mainly been investigated. Traditional techniques are critically reviewed to understand their limitations and how supercritical CO2-assisted processes could overcome these drawbacks. In particular, even if freeze-drying represents the most widespread drying technique used to produce polysaccharide-based cryogels, supercritical CO2-assisted drying effectively allows preservation of the nanoporous aerogel structure and removes the organic solvent used for gel preparation. These characteristics are essential for cell adhesion and proliferation.

Water-soluble poly(ethylene glycol) methyl ether-grafted chitosan/alginate polyelectrolyte complex hydrogels

This study aimed to fabricate polyelectrolyte complexes from water-soluble poly(ethylene glycol) methyl ether-grafted chitosan (mPEG-g-CTS) and alginate (ALG) in the absence of acetic acid. The complexes formed fibrous network macrogels when mPEG-g-CTS with short mPEG chains (mPEG750-g-CTS and mPEG2000-g-CTS) and mPEG-g-CTS:ALG weight ratios in the range from 1:0.14 to 1:1 were used. The macrogels at a weight ratio of mPEG-g-CTS:ALG of 1:1 possessed the highest elasticity with electrophoretic mobility close to 0 m²·V^-1·s^-1. Water uptake of the sponge-like lyophilized macrogels decreased with increasing ALG content, mPEG chain length, and degree of substitution of mPEG-g-CTS. In contrast, the polyelectrolyte complexes prepared using long mPEG chains of mPEG-g-CTS (mPEG5000-g-CTS) formed spherical nanoparticles (70-90 nm) and showed highly negative electrophoretic mobility (< -3.20 × 10⁸ m²·V^-1·s^-1). The obtained mPEG-g-CTS/ALG polyelectrolyte complex hydrogels and nanoparticles have the potential to be applied as carriers for functional food additives, drugs, and bioactive compounds.

Lyophilized Emulsions in the Form of 3D Porous Matrices as a Novel Material for Topical Application

Researchers are constantly searching for innovations that can be applied to the cosmetic industry. Production of porous materials stored in a lyophilized form and swollen directly before use may be beneficial considering their facilitated packaging, transport and storage. In this study, we propose porous materials based on sodium alginate, gelatin, glycerol and lipids (cottonseed oil and beeswax) obtained by freeze-drying and cross-linking. Material composition with the most promising properties was modified by the addition of PLA microparticles with Calendula officinalis flower extract. The structure and properties of obtained porous materials were analyzed. ATR-FTIR, mechanical properties, residual moisture content, porosity and density were assessed, as well as swelling properties and degradation after their cross-linking. The loading capacity and in vitro release of Calendula officinalis flower extract were performed for samples with incorporated PLA microparticles containing plant extract. The modification of the composition and fabrication method of materials significantly influenced their physicochemical properties. The selected plant extract was successfully incorporated into polymeric microparticles that were subsequently added into developed materials. Prepared materials may be considered during designing new cosmetic formulations.

Agarose, Alginate and Chitosan Nanostructured Aerogels for Pharmaceutical Applications: A Short Review

In this short review, drug delivery systems, formed by polysaccharide-based (i.e., agarose, alginate, and chitosan) aerogels, are analyzed. In particular, the main papers, published in the period 2011-2020 in this research field, have been investigated and critically discussed, in order to highlight strengths and weaknesses of the traditional production techniques (e.g., freeze-drying and air evaporation) of bio-aerogels with respect to supercritical CO₂ assisted drying. Supercritical CO₂ assisted drying demonstrated to be a promising technique to produce nanostructured bio-aerogels that maintain the starting gel volume and shape, when the solvent removal occurs at negligible surface tension. This characteristic, coupled with the possibility of removing also cross-linking agent residues from the aerogels, makes these advanced devices safe and suitable as carriers for controlled drug delivery applications.

Sequestration of Sulfate Anions from Groundwater by Biopolymer-Metal Composite Materials

Binary (Chitosan-Cu(II), CCu) and Ternary (Chitosan-Alginate-Cu(II), CACu) composite materials were synthesized at variable composition: CCu (1:1), CACu1 (1:1:1), CACu2 (1:2:1) and CACu3 (2:1:1). Characterization was carried out via spectroscopic (FTIR, solids C-13 NMR, XPS and Raman), thermal (differential scanning calorimetry (DSC) and TGA), XRD, point of zero charge and solvent swelling techniques. The materials' characterization confirmed the successful preparation of the polymer-based composites, along with their variable physico-chemical and adsorption properties. Sulfate anion (sodium sulfate) adsorption from aqueous solution was demonstrated using C and CACu1 at pH 6.8 and 295 K, where the monolayer adsorption capacity (Qm) values were 288.1 and 371.4 mg/g, respectively, where the Sips isotherm model provided the "best-fit" for the adsorption data. Single-point sorption study on three types of groundwater samples (wells 1, 2 and 3) with variable sulfate concentration and matrix composition in the presence of composite materials reveal that CACu3 exhibited greater uptake of sulfate (Qe = 81.5 mg/g; 11.5% removal) from Well-1 and CACu2 showed the lowest sulfate uptake (Qe of 15.7 mg/g; 0.865% removal) from Well-3. Generally, for all groundwater samples, the binary composite material (CCu) exhibited attenuated sorption and removal efficiency relative to the ternary composite materials (CACu).

Novel alginate-chitosan aerogel fibres for potential wound healing applications

Aerogels produced from marine polymers, such as chitosan and alginate, are of interest for wound healing applications due to their attractive properties. These properties can be the aerogel's high porosity along with the antimicrobial activity of chitosan or the capacity to provide a moist environment of alginate. The aim of this work was to develop a new route towards hybrid alginate-chitosan aerogel fibres and to evaluate their potential for wound healing applications. The influence of chitosan molecular weight and its content on the fibres characteristics was evaluated. To produce the fibres, the formation of polyelectrolyte complex hydrogels of both polymers was performed by the emulsion-gelation method. Hydrogels were converted in alcogels through a solvent exchange followed by drying with supercritical CO₂. Resulting aerogels were observed to be light-weight, fluffy mesoporous fibres with a specific surface area of 162-302 m²/g and specific pore volume of 1.41-2.49 cm³/g. Biocompatibility of the fibres was evaluated, and the result showed that they were non-cytotoxic. Bioactivity of the fibres regarding the ability to close a wound on an in vitro scale and antibacterial activity were also evaluated. Aerogel fibres presented percentages of recovered scratch area of about 75%, higher than the untreated control (~50%) and a clear antibacterial activity against Staphylococcus aureus and Klebsiella pneumoniae. The obtained results suggest that these alginate-chitosan aerogel fibres could be good candidates for wound healing applications.

The Innovation Comes from the Sea: Chitosan and Alginate Hybrid Gels and Films as Sustainable Materials for Wastewater Remediation

The growing utilization of renewable and residual biomasses for environmental preservation and remediation are important goals to be pursued to minimize the environmental impact of human activities. In this paper, sodium alginate (derived from brown algae) was crosslinked using chitosan (mainly derived from the exoskeleton of crustaceans) in the presence of biowaste-derived substances isolated from green compost (BBS-GC), to produce hydrogels and dried films. The obtained materials were tested as adsorbents for wastewater remediation. To this purpose, gels were characterized using a multi-analytical approach and used as active substrates for the removal of three differently-charged molecules, chosen as model pollutants: crystal violet, rhodamine B, and orange II. The effectiveness of the gel formulations was demonstrated and attributed to the variety of active functionalities introduced by the different precursors, the structural factors and the peculiar physicochemical properties of the resulting materials.

Bioplatform Fabrication Approaches Affecting Chitosan-Based Interpolymer Complex Properties and Performance as Wound Dressings

Chitosan can form interpolymer complexes (IPCs) with anionic polymers to form biomedical platforms (BMPs) for wound dressing/healing applications. This has resulted in its application in various BMPs such as gauze, nano/microparticles, hydrogels, scaffolds, and films. Notably, wound healing has been highlighted as a noteworthy application due to the remarkable physical, chemical, and mechanical properties enabled though the interaction of these polyelectrolytes. The interaction of chitosan and anionic polymers can improve the properties and performance of BMPs. To this end, the approaches employed in fabricating wound dressings was evaluated for their effect on the property-performance factors contributing to BMP suitability in wound dressing. The use of chitosan in wound dressing applications has had much attention due to its compatible biological properties. Recent advancement includes the control of the degree of crosslinking and incorporation of bioactives in an attempt to enhance the physicochemical and physicomechanical properties of wound dressing BMPs. A critical issue with polyelectrolyte-based BMPs is that their effective translation to wound dressing platforms has yet to be realised due to the unmet challenges faced when mimicking the complex and dynamic wound environment. Novel BMPs stemming from the IPCs of chitosan are discussed in this review to offer new insight into the tailoring of physical, chemical, and mechanical properties via fabrication approaches to develop effective wound dressing candidates. These BMPs may pave the way to new therapeutic developments for improved patient outcomes.

Effect of Sodium Alginate Type on Drug Release from Chitosan-Sodium Alginate-Based In Situ Film-Forming Tablets

Natural polymers are promising as the carrier of matrix-based sustained release tablets but limited by their diversity in source and structure properties. Our previous studies found that chitosan (CS)- and alginate (SA)-based tablets can form self-assembled polyelectrolyte complex (PEC) film on the surface, which controlled drug release with a novel mechanism. To elucidate whether PEC-based sustained drug delivery system could weaken the influence of single-matrix material diversity on drug release behavior, taking theophylline as a drug model, the effect of SA structure properties, including viscosity, G/M ratio, SA salt type, and degree of esterification on drug release profiles, swelling, and erosion of CS-SA composite system was investigated. The results showed that the viscosity, G content, salt type, and esterification degree of SA had a remarkable influence on drug release when SA alone was used as a matrix, but little effect of these parameters on drug release was observed in CS-SA combination system. SA of low viscosity is superior in controlling drug release from CS-SA combination system. Potassium, magnesium salt of SA, and esterified SA can help form PEC of higher thickness with different swelling and erosion extent. In conclusion, this study demonstrated that drug release diversity due to SA structure difference can be well eradicated by using CS-SA combination system, which is a promising strategy to manufacture natural polymer-based products with constant quality.

α-Mangostin Hydrogel Film Based Chitosan–Alginate for Recurrent Aphthous Stomatitis

Many antiseptic drugs, local anaesthetics, and corticosteroids have been used for effective therapy of recurrent aphthous stomatitis (RAS). However, these drugs have harmful side effects. α-mangostin (α-M), a main compound of mangosteen (Garcinia mangostana L.) peel, has been known as a wound healing agent. In addition, hydrogel film as dressings designed to separate mucosal lesions from the oral environment, and improve the effectiveness of RAS therapy. The purpose of this study was to develop α-M hydrogel film based chitosan–alginate (ChAlg/α-M HF) for RAS. The in silico study by Discovery studio visualizer and AutoDock confirmed that hydrogen bonding between Ch, Alg, and α-M occurred. The results of physicochemical characterizations by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) indicated that the ChAlg/α-M HF had a lower crystalline form compared to pure α-M. In addition, ChAlg/α-M HF significantly improved the swelling ratio and tensile strength compared to that of ChAlg HF. Moreover, the existence of Alg increased the degradability of Ch, and closely related to the release of α-M from ChAlg HF. The in vitro release study confirmed that the release of α-M from ChAlg/α-M HF was the Fickian diffusion model. Finally, the mucoadhesive study revealed that ChAlg/α-M HF had a good mucoadhesive property. These results suggest that hydrogel film-based chitosan–alginate have the potential as carriers of α-M for RAS therapy.

Electrospun Chitosan/Poly (Vinyl Alcohol)/Graphene Oxide Nanofibrous Membrane with Ciprofloxacin Antibiotic Drug for Potential WoundDressing Application

In this paper, nanofibrous membranes based on chitosan (CS), poly (vinyl alcohol) (PVA) and graphene oxide (GO) composites, loaded with antibiotic drugs, such as Ciprofloxacin (Cip) and Ciprofloxacin hydrochloride (CipHcl) were prepared via the electrospinning technique. The uniform and defect-free CS/PVA nanofibers were obtained and GO nanosheets, shaping spindle and spherical, were partially embedded into nanofibers. Besides, the antibiotic drugs were effectively loaded into the nanofibers and part of which were absorbed into GO nanosheets. Intriguingly, the release of the drug absorbed in GO nanosheets regulated the drug release profile trend, avoiding the "burst" release of drug at the release initial stage, and the addition of GO slightly improved the drug release ratio. Nanofibrous membranes showed the significantly enhanced antibacterial activity against Escherichia coli, Staphylococcus aureus and Bacillus subtilis after the addition of antibiotic drug. Moreover, the drug-loaded nanofibrous membranes exhibited excellent cytocompatibility with Melanoma cells, indicative to the great potential potential for applications in wound dressing.

Elaboration of a thermosensitive smart biomaterial: From synthesis to the ex vivo bioadhesion evaluation

Alginate and chitosan are polysaccharides that are widely used in the biomedical field, especially as wound dressings. Controlled bioadhesion is an advanced functionality that offers the potential to reduce injuries due to the stripping-off of the biomaterial. Herein, we report the efficient grafting of poly-N(isopropylacryamide) (PNIPAM), a thermosensitive polymer that exhibits a lower critical solution temperature (LCST) at 32 °C on the alginate/chitosan polyelectrolyte complex (PEC) surface. In vitro studies did not exhibit a cytotoxic effect, and cells adhered preferentially on the LCST on PNIPAM grafted surfaces, as reported in the literature. Ex vivo investigations revealed that the adhesive behavior of the biomaterials was not the same on the liver and pancreas. The effect of the temperature on the bioadhesion to organs was unexpected, as PNIPAM surfaces exhibited higher adhesion at low temperature. The PNIPAM was therefore able to confer PEC matrix thermosensitivity, but due to the application force, interactions between PNIPAM chains and their substrate could influence bioadhesion on tissues.

Characterization of hydroxyapatite-containing alginate-gelatin composite films as a potential wound dressing

In this study, hydroxyapatite (HA)-containing alginate-gelatin films were prepared by solution casting method by blending alginate (A) and gelatin (G) solutions, followed by crosslinking with calcium chloride. HA (1, 2, 5, 10, 20% w/w) was added to film solutions prepared at different ratios (A:G = 40:60, 50:50, and 60:40) and the swelling and degradation behavior, mechanical, antimicrobial and thermal properties, and morphologies of the obtained films were examined. The release of tetracycline hydrochloride (TH), selected as a model drug, from the prepared films was studied. It was observed that the swelling ratio and weight loss of the films decreased as the amounts of alginate and HA increased. Scanning electron microscopy analysis indicated that as the amount of HA in the films increased, the film surface becomes rougher. The mechanical properties of the films were affected by the amount of HA and the A:G ratio. Incorporation of HA increased the thermal stability of films. The amount of TH released from the films within 15 min decreased as the amounts of alginate and hydroxyapatite increased. It was found that films containing TH showed slightly higher antimicrobial activity against Staphylococcus aureus than Escherichia coli.

Coated electrospun alginate-containing fibers as novel delivery systems for regenerative purposes

Aim

The aim of the present work was to develop biodegradable alginate (ALG)-containing fibrous membranes intended for tissue repair, acting as both drug delivery systems and cell growth guidance.

Methods

Membranes were prepared by electrospinning. Since ALG can be electrospun only when blended with other spinnable polymers, dextran (DEX) and polyethylene oxide (PEO) were investigated as process adjuvants. ALG/DEX mixtures, characterized by different rheological and conductivity properties, were prepared in phosphate buffer or deionized water; surfactants were added to modulate polymer solution surface tension. The Design of Experiments (DoE) approach (full factorial design) was used to investigate the role of polymer solution features (rheological properties, surface tension, and conductivity) on electrospun fiber morphology. A high viscosity at 1,000 s^-1 (1.3-1.9 Pa.s) or a high pseudoplasticity index (≥1.7), combined with a low surface tension (30-32 mN/m) and a low conductivity (800-1,000 μS/cm), was responsible for the production of ALG/DEX homogeneous fibers. Such ranges were successfully employed for the preparation of ALG-containing fibers, using PEO, instead of DEX, as process adjuvant. ALG/DEX and ALG/PEO fibers were subsequently subjected to cross-linking/coating processes to make them slowly biodegradable in aqueous medium. In particular, ALG/PEO fibers were cross-linked and coated with CaCl₂/chitosan solutions in water/ethanol mixtures. Due to DEX high content, ALG/DEX fibers were soaked in a polylactide-co-glycolide (PLGA) solution in ethyl acetate.

Results

Both cross-linking and coating processes made fibers insoluble in physiological medium and produced an increase in their mechanical resistance, assessed by means of a tensile test. PLGA-coated ALG/DEX and chitosan-coated ALG/PEO fibers were biocompatible and able to support fibroblast adhesion.

Conclusion

The DoE approach allowed to draw up guidelines useful for the preparation of homogeneous fibers, starting from mixtures of ALG and non-ionic polymers. Such fibers, upon coating, resulted to be good cell substrates, allowing cell adhesion and growth.

Investigation of in vitro hydrophilic and hydrophobic dual drug release from polymeric films produced by sodium alginate-MaterBi® drying emulsions

Emulsions are known to be effective carriers of hydrophobic drugs, and particularly injectable emulsions have been successfully implemented for in vivo controlled drug release. Recently, high internal phase emulsions have also been used to produce porous polymeric templates for pharmaceutical applications. However, emulsions containing dissolved biopolymers both in the oil and water phases are very scarce. In this study, we demonstrate such an emulsion, in which the oil phase contains a hydrophobic biodegradable polymer, MaterBi®, and the water phase is aqueous sodium alginate dispersion. The two phases were emulsified simply by ultrasonic processing without any surfactants. The emulsions were stable for several days and were dried into composite solid films with varying MaterBi®/alginate fractions. The films were loaded with two model drugs, a hydrophilic eosin-based cutaneous antiseptic and the hydrophobic curcumin. Drug release capacity of the films was investigated in detail, and controlled release of each model drug was achieved either by tuning the polymer fraction in the films during emulsification or by crosslinking sodium alginate fraction of the films by calcium salt solution immersion. The emulsions can be formulated to carry either a single model drug or both drugs depending on the desired application. Films demonstrate excellent cell biocompatibility against human dermal fibroblast, adult cells.

The chitosan hydrogels: from structure to function

This review places an emphasis on chitosan intelligent hydrogels. The fabrication methods and mechanisms are introduced in this review and the interactions of the formation of hydrogels with both physical and chemical bonds are also introduced. The relationship between the structural characteristics and the corresponding functions of stimuli-responsive characteristics, self-healing functions and high mechanical strength properties of the chitosan hydrogels are discussed in detail.

Release Behavior and Antibacterial Activity of Chitosan/Alginate Blends with Aloe vera and Silver Nanoparticles

Aloe vera is a perennial plant employed for medical, pharmaceutical and cosmetic purposes that is rich in amino acids, enzymes, vitamins and polysaccharides, which are responsible for its therapeutic properties. Incorporating these properties into a biopolymer film obtained from alginate and chitosan allowed the development of a novel wound dressing with antibacterial capacity and healing effects to integrate the antibacterial capacity of silver nanoparticles with the healing and emollient properties of Aloe vera gel. Three alginate-chitosan matrices were obtained through blending methods using different proportions of alginate, chitosan, the Aloe vera (AV) gel and silver nanoparticles (AgNps), which were incorporated into the polymeric system through immersion methods. Physical, chemical and antibacterial characteristics were evaluated in each matrix. Interaction between alginate and chitosan was identified using the Fourier transform infrared spectroscopy technique (FTIR), porosity was studied using scanning electron microscopy (SEM), swelling degree was calculated by difference in weight, Aloe vera gel release capacity was estimated by applying a drug model (Peppas) and finally antibacterial capacity was evaluated against S. Aureus and P. aeruginosa. Results show that alginate-chitosan (A (1:3 Chit 1/Alg 1); B (1:3 Chit 1.5/Alg 1) and C (3:1 Chit 1/Alg 1/B12)) matrices with Aloe vera (AV) gel and silver nanoparticles (AgNps) described here displayed antibacterial properties and absorption and Aloe vera release capacity making it a potential wound dressing for minor injuries.