Advances on alginate use for spherification to encapsulate biomolecules

Novel pH- and thermal-responsive oleogel capsules: Featuring an oleogel core and ultrathin calcium-alginate shell

Oleogels have been explored as a new lipid-based delivery system, however, their insolubility and unsuitable shape severely limit their application in food systems. Herein, core-shell oleogel capsules with high monodispersity (coefficient variation (CV) < 5%)) were prepared via gravity-assisted co-flowing microfluidic device and simply air-drying. The oleogel capsules with oleogel core and ultrathin calcium-alginate shell were prepared. Oleogel capsules maintained their original shape at pH = 2.0 but swelled rapidly at pH = 6.8 and 7.4. The swelling ratio of shell can be adjusted by inner fluid flow rate (Qin). Notably, the core with beeswax (BW) crystal network, effectively improved the stability performances and also could provide thermal response. Finally, the oleogel capsules demonstrated excellent sustained release and UV protection of lipophilic bioactives. This work sheds light on development of novel oleogel capsules, making them ideal candidates for smart food encapsulation applications.

Biomedical potentials of alginate via physical, chemical, and biological modifications

Alginate is a linear polysaccharide with a modifiable structure and abundant functional groups, offers immense potential for tailoring diverse alginate-based materials to meet the demands of biomedical applications. Given the advancements in modification techniques, it is significant to analyze and summarize the modification of alginate by physical, chemical and biological methods. These approaches provide plentiful information on the preparation, characterization and application of alginate-based materials. Physical modification generally involves blending and physical crosslinking, while chemical modification relies on chemical reactions, mainly including acylation, sulfation, phosphorylation, carbodiimide coupling, nucleophilic substitution, graft copolymerization, terminal modification, and degradation. Chemical modified alginate contains chemically crosslinked alginate, grafted alginate and oligo-alginate. Biological modification associated with various enzymes to realize the hydrolysis or grafting. These diverse modifications hold great promise in fully harnessing the potential of alginate for its burgeoning biomedical applications in the future. In summary, this review provides a comprehensive discussion and summary of different modification methods applied to improve the properties of alginate while expanding its biomedical potentials.

Enhanced antibacterial activity of starch-alginate beads by a synergistic effect between Cu2+ and Zn2+ ions with a potential wound dressing application

The synthesis and characterization of starch/alginate composite beads, crosslinked with Cu2+, Zn2+, and Cu:Zn mixtures were investigated, focusing on their potential application in exudative wound dressings. Hydrogel beads were prepared using the external gelation method and then dried via freeze-drying to create cryogels and air-drying to create xerogels. Microstructural characterization was performed using SEM and EDS, showing the typical porous structure with a homogeneous distribution of cations across the beads. Unimetallic beads exhibited higher equilibrium water uptake compared to Cu:Zn bimetallic beads (500 % vs. 300 %). After the swelling study, the total amount of Cu2+ released was significantly below the maximum allowed level as a safeguard against copper toxicity. All beads demonstrated excellent antimicrobial activity against E. coli, S. aureus, and P. aeruginosa. Bimetallic materials, particularly cryogels with equal or greater amount of zinc relative to copper, were particularly effective against P. aeruginosa. Hence, the synthesized bimetallic starch-alginate materials presented superior water absorption capacity and significantly enhanced antibacterial response compared to unimetallic beads, due to the synergistic effect between Cu2+ and Zn2+ ions, making then suitable for use in exudative wound dressings.

Alginate Capsules: Versatile Applications and Production Techniques

Alginate is a natural polysaccharide commonly obtained from brown algae and is usually used in the food industry as an additive, specifically as a thickening, gelling, and emulsifying agent. Due to its polyanionic nature, it can crosslink in the presence of divalent or trivalent cations. This crosslinking process involves the formation of chemical bonds between the carboxylic groups of parallel chains, resulting in a solid structure. In this way, compounds of interest can be enclosed in a capsule or a bead. Thanks to this ability, possible applications of alginate capsules are countless: it is possible to range from the pharmaceutical to the nutritional fields, from the agri-food industry to the textile or cosmetic sectors. These capsules can protect the encapsulated ingredients, promote their delivery or controlled release, or be imagined as small-scale reactors. The present review describes the main techniques used to produce alginate capsules, and several examples of possible application fields are shown.

Probing of New Polymer-Based Microcapsules for Islet Cell Immunoisolation

Islet allotransplantation offers a promising cell therapy for type 1 diabetes, but challenges such as limited donor availability and immunosuppression persist. Microencapsulation of islets in polymer-coated alginate microcapsules is a favored strategy for immune protection and maintaining islet viability. This study introduces Poly [2-(methacryloyloxy)ethyl]trimethylammonium chloride (PMETAC) as an innovative coating material for microcapsules. PMETAC enhances biocompatibility and durability, marking a significant advancement in islet encapsulation. Our approach combines alginate with PMETAC to create Langerhans islet microcapsules, simplifying material composition and preparation and ultimately lowering costs and increasing clinical applicability. Our comprehensive evaluation of the stability (including osmotic stability, thermal stability, and culture condition stability) and cytotoxicity of a novel microencapsulation system based on alginate-PMETAC-alginate offers insights into its potential application in islet immunoisolation strategies. Microcapsules with PMETAC content ranging from 0.01 to 1% are explored in the current work. The results indicate that the coatings made with 0.4% PMETAC show the most promising outcomes, remaining stable in the mentioned tests and exhibiting the required permeability. It was shown that the islets encapsulated in this manner retain viability and functional activity. Thus, alginate microcapsules coated with 0.4% PMETAC are suitable for further animal trials. While our findings are promising, further studies, including animal testing, will be necessary to evaluate the clinical applicability of our encapsulation method.

Alginate beads loaded with rambutan extract: characterization and stability during in vitro gastrointestinal digestion

BACKGROUND

Fallen young rambutan fruit is an underrated agricultural waste which may contain several bioactive compounds. In this study, fallen young rambutan fruit was assessed regarding its phenolic contents and antioxidant activities. In order to expand its utilization, rambutan extract-loaded hydrogel beads were developed by a basic spherification technique using sodium alginate. The effect of ratios of polymer and extract and different calcium sources were evaluated. The recovery of bioactive compounds from the hydrogel beads was determined using in vitro gastrointestinal digestion models.

RESULTS

Use of 50% (v/v) ethanol yielded rambutan extract with good chemical properties. The production of hydrogel beads using a ratio of 1:3 with calcium lactate provided the highest production yield of 122.94%. The hydrogel beads developed using the ratio of 1:3 with a combination of calcium lactate and calcium chloride showed high recovery of phenolic compounds and antioxidant activity after simulated intestinal digestion, which were greater compared to unencapsulated extract.

CONCLUSION

The findings demonstrate that the ratio of wall material to rambutan extract and the calcium source influence the physical properties, chemical properties and in vitro gastrointestinal digestion stability of alginate beads. The obtained hydrogel beads may have potential for application in the food or pharmaceutical industries. © 2024 Society of Chemical Industry.

Alginate-Based UV Sensor: A Simple and Inexpensive Tool for Educational Purposes

This document presents a simple yet highly effective demonstration for creating UV radiation sensors using alginate molecules. This demonstration can easily be aligned with the Next Generation Science Standards (NGSS) for classroom use. Moreover, the demonstration requires only a few easily obtainable materials, and the process involved is straightforward. When exposed to UV light or sunlight, the spheres' color changes, offering a fascinating observation that is sure to capture the imagination of students of all ages. This encourages curiosity and inspires further exploration of the scientific world. It is easily understandable and suitable for people of all ages. This experiment represents a valuable addition to the scientific community's educational tools, and its potential to inspire a new generation of scientists is truly limitless.

Postbiotics-peptidoglycan, lipoteichoic acid, exopolysaccharides, surface layer protein and pili proteins-Structure, activity in wounds and their delivery systems

Chronic wound healing is a pressing global public health concern. Abuse and drug resistance of antibiotics are the key problems in the treatment of chronic wounds at present. Postbiotics are a novel promising strategy. Previous studies have reported that postbiotics have a wide range of biological activities including antimicrobial, immunomodulatory, antioxidant and anti-inflammatory abilities. However, several aspects related to these postbiotic activities remain unexplored or poorly known. Therefore, this work aims to outline general aspects and emerging trends in the use of postbiotics for wound healing, such as the production, characterization, biological activities and delivery strategies of postbiotics. In this review, a comprehensive overview of the physiological activities and structures of postbiotic biomolecules that contribute to wound healing is provided, such as peptidoglycan, lipoteichoic acid, bacteriocins, exopolysaccharides, surface layer proteins, pili proteins, and secretory proteins (p40 and p75 proteins). Considering the presence of readily degradable components in postbiotics, potential natural polymer delivery materials and delivery systems are emphasized, followed by the potential applications and commercialization prospects of postbiotics. These findings suggest that the treatment of chronic wounds with postbiotic ingredients will help provide new insights into wound healing and better guidance for the development of postbiotic products.

Transforming the Stability, Encapsulation, and Sustained Release Properties of Calcium Alginate Beads through Gel-Confined Coacervation

Calcium alginate (Ca2+/alginate) gel beads find use in diverse applications, ranging from drug delivery and tissue engineering to bioprocessing, food formulation, and agriculture. Unless modified, however, these gels have limited stability in alkaline media (including phosphate buffers), and their high solute permeability limits their ability to efficiently encapsulate and slowly release water-soluble small molecules. Here, we show how these limitations can be addressed by mixing the alginate solutions used in the bead preparation with the nontoxic anionic polymer polyphosphate (PP). Upon complexing Ca2+ ions, PP undergoes complex coacervation (i.e., liquid/liquid phase separation into a Ca2+/PP-rich coacervate phase and a dilute supernatant phase). At lower PP concentrations, the Ca2+/PP coacervate appears to simply remain dispersed within the beads. Though its presence makes the beads more stable in alkaline media (phosphate-buffered saline and seawater), it has little impact on the bead stiffness, morphology, and (at least in the absence of substantial payload/coacervate association) encapsulation and release properties. When the PP concentrations exceed a critical value, however, Ca2+/PP coacervation within the gelling Ca2+/alginate beads collapses the resulting beads into more compact, interpenetrating polymer networks. Besides their enhanced stability to alkaline environments, these hybrid beads exhibit irregular morphologies with wrinkled and dimpled surface structures and macroscopic (closed) internal pores, and their collapse into these polymer-rich networks also makes them significantly stiffer than their PP-free counterparts. Crucially, these beads also exhibit a much lower solute permeability, which enables highly efficient encapsulation and multiday release of water-soluble small molecules (with the beads encapsulating >90% of the added model payload and sustaining its release over 3-5 d). Collectively, these findings provide a mild and simple (single-step) pathway to generating ionically cross-linked alginate beads with significantly enhanced stability, encapsulation efficiency, and sustained release.

Encapsulation in Alginates Hydrogels and Controlled Release: An Overview

This review aims to gather the current state of the art on the encapsulation methods using alginate as the main polymeric material in order to produce hydrogels ranging from the microscopic to macroscopic sizes. The use of alginates as an encapsulation material is of growing interest, as it is fully bio-based, bio-compatible and bio-degradable. The field of application of alginate encapsulation is also extremely broad, and there is no doubt it will become even broader in the near future considering the societal demand for sustainable materials in technological applications. In this review, alginate's main properties and gelification mechanisms, as well as some factors influencing this mechanism, such as the nature of the reticulation cations, are first investigated. Then, the capacity of alginate gels to release matter in a controlled way, from small molecules to micrometric compounds, is reported and discussed. The existing techniques used to produce alginates beads, from the laboratory scale to the industrial one, are further described, with a consideration of the pros and cons with each techniques. Finally, two examples of applications of alginate materials are highlighted as representative case studies.

Insights from Syzygium aromaticum Essential Oil: Encapsulation, Characterization, and Antioxidant Activity

Alginate encapsulates loaded with clove essential oil (CEO) were prepared by ionic gelation, with subsequent freeze-drying. The objective of the present work was to develop a product with the ability to protect CEO against its easy volatility and oxidation. The following techniques were used to characterize the formulations: eugenol release, degree of swelling, GC/MS, TGA/DSC, and SEM. The alginate solution (1.0%) containing different concentrations of CEO (LF1: 1.0%; LF2: 0.5%; LF3: 0.1%) was dropped into a 3.0% CaCl2 solution. After lyophilization, the encapsulated samples were wrinkled and rigid, with high encapsulation power (LF3: 76.9% ± 0.5). Three chemical components were identified: eugenol (the major one), caryophyllene, and humulene. The antioxidant power (LF1: DPPH IC50 18.1 µg mL-1) was consistent with the phenol content (LF1: 172.2 mg GAE g-1). The encapsulated ones were thermally stable, as shown by analysis of FTIR peaks, eugenol molecular structure was kept unaltered. The degree of swelling was 19.2% (PBS). The release of eugenol (92.5%) in the PBS solution was faster than in the acidic medium. It was concluded that the low-cost technology used allows the maintenance of the content and characteristics of CEO in the three concentrations tested, offering a basis for further research with essential oil encapsulates.

Microbeads as carriers for Bacillus pumilus: a biofertilizer focus on auxin production

The study aimed to develop a solid biofertilizer using Bacillus pumilus, focusing on auxin production to enhance plant drought tolerance. Methods involved immobilising B. pumilus in alginate-starch beads, focusing on microbial concentration, biopolymer types, and environmental conditions. The optimal formulation showed a diameter of 3.58 mm ± 0.18, a uniform size distribution after 15 h of drying at 30 °C, a stable bacterial concentration (1.99 × 109 CFU g-1 ± 1.03 × 109 over 180 days at room temperature), a high auxin production (748.8 µg g-1 ± 10.3 of IAA in 7 days), and a water retention capacity of 37% ± 4.07. In conclusion, this new formulation of alginate + starch + L-tryptophan + B. pumilus has the potential for use in crops due to its compelling water retention, high viability in storage at room temperature, and high auxin production, which provides commercial advantages.

Physicochemical and Functional Properties of Citrullus mucosospermus, Citroides, and Moringa oleifera Seeds' Hydrocolloids

Hydrocolloids form gel-like structures when dispersed in water and have garnered significant attention for their diverse applications in food, pharmaceuticals, and other industries. The extraction of hydrocolloids from natural sources, such as seeds, presents an intriguing avenue due to the potential diversity in composition and functionality. Utilising seeds from Citrullus lanatus mucosospermus, lanatus citroides, and Moringa aligns with the growing demand for natural and sustainable ingredients in various industries. This research investigated hydrocolloids extracted from Citrullus mucosospermus (CMS), lanatus citroides, and Moringa oleifera seeds, highlighting their versatile physicochemical and functional attributes. Hydrocolloids were extracted from the seeds and subjected to analysis of their proximate composition, particle size distribution, and interfacial tension using the hot water extraction method. Protein content variation was observed among the raw oilseed (CMS, Citroides, and Moringa oleifera) flours. The protein content of the hydrocolloids surpassed that of raw oilseeds, significantly enhancing the amino acid profile. Furthermore, the hydrocolloid ash contents ranged from 4.09% to 6.52% w/w dry weight, coupled with low fat levels. The particle size distribution revealed predominantly fine particles with a narrow size distribution. All three hydrocolloids demonstrated remarkable oil- and water-holding capacities, highlighting their suitability for efficient stabilisation and emulsification in food formulations. These findings suggest the potential utilisation of these hydrocolloids as valuable ingredients across a spectrum of applications, encompassing food, pharmaceuticals, and industry, thus contributing to the development of sustainable and functional products. The unique attributes presented herein mark a noteworthy advancement in the understanding and application of novel hydrocolloids from CMS, Citroides, and Moringa oleifera.

Magnetic core-shell cellulose system for the oriented immobilization of a recombinant β-galactosidase with a protein tag

The objective of this study was to immobilize a recombinant β-galactosidase (Gal) tagged with a cellulose-binding domain (CBD) onto a magnetic core-shell (CS) cellulose system. After 30 min of reaction, 4 U/capsule were immobilized (CS@Gal), resulting in levels of yield and efficiency exceeding 80 %. The optimal temperature for β-galactosidase-CBD activity increased from 40 to 50 °C following oriented immobilization. The inhibitory effect of galactose decreased in the enzyme reactions catalyzed by CS@Gal, and Mg2+ increased the immobilized enzyme activity by 40 % in the magnetic CS cellulose system. The relative enzyme activity of the CS@Gal was 20 % higher than that of the soluble enzyme activity after 20 min at 50 °C. The CS support and CS@Gal capsules exhibited an average size of 8 ± 1 mm, with the structure of the shell (alginate-pectin-cellulose) enveloping and isolating the magnetic core. The immobilized β-galactosidase-CBD within the magnetic CS cellulose system retained ∼80 % of its capacity to hydrolyze lactose from skim milk after 10 reuse cycles. This study unveils a novel and promising support for the oriented immobilization of recombinant β-galactosidase using a magnetic CS system and a CBD tag. This support facilitates β-galactosidase reuse and efficient separation, consequently enhancing the catalytic properties of the enzyme.

Advances in polysaccharides for probiotic delivery: Properties, methods, and applications

Probiotics are essential to improve the health of the host, whereas maintaining the viability of probiotics in harsh environments remains a challenge. Polysaccharides have non-toxicity, excellent biocompatibility, and outstanding biodegradability, which can protect probiotics by forming a physical barrier and show a promising prospect for probiotic delivery. In this review, we summarize polysaccharides commonly used for probiotic microencapsulation and introduce the microencapsulation technologies, including extrusion, emulsion, spray drying, freeze drying, and electrohydrodynamics. We discuss strategies for better protection of probiotics and introduce the applications of polysaccharides-encapsulated probiotics in functional food, oral formulation, and animal feed. Finally, we propose the challenges of polysaccharides-based delivery systems in industrial production and application. This review will help provide insight into the advances and challenges of polysaccharides in probiotic delivery.

Construction and functional evaluation of oral long-acting insulin hydrogel microparticles based on physical and chemical double crosslinking

The objective of this study was to enhance the convenience and effectiveness of diabetes treatment by developing hydrogel microparticles as an oral insulin delivery system, aiming to reduce the necessity for frequent treatments. The hydrogel microparticles were prepared with polysaccharides through a combination of physical and chemical crosslinking method, they achieved good results in insulin loading efficiency (70 %), insulin release efficiency (98 %) and sustained release time (>20 h). The effective transmembrane transport was validated using an intestinal epithelial cell model, which demonstrated a continuous hypoglycemic effect lasting from 6 to 26 h in a type 2 diabetes mouse model. Additionally, the relative bioavailability of insulin reached 30.14 ± 2.62 %, representing a significant breakthrough in the field of oral insulin delivery carriers. Furthermore, oral insulin hydrogel exhibited a substantial improvement in insulin resistance, organ damage, and diabetes-related complications stemming from hyperglycemia. These compelling findings underscore the potential of hydrogel microparticles as a cost-effective and valuable strategy for oral drug delivery in diabetes treatment.

Fabrication and study on dually modified starch embedded in alginate hydrogel as an encapsulation system for Satureja essential oil

This study aimed to investigate how the types and order of modifications influence the structure and physicochemical characteristics of modified porous starch. The work focuses on the encapsulation of essential oil in hydrophobic microcapsules embedded in sodium alginate hydrogels. FTIR spectra indicated successful esterification of starch with OSA. 1047:1022 cm-1 and 1022:995 cm-1 band ratios of FTIR spectra revealed increased crystallinity due to enzymatic modification, supported by XRD patterns. Porous-OSA (PO) starch had 1.5 times higher degree of substitution (DS) than OSA-porous (OP) starch, confirmed by the intense peak at 0.85 ppm in 1H NMR spectra. SEM images displayed larger particles and smaller pore diameter in OP compared to PO and porous starch, indicating amylolytic enzyme inhibition by OSA. Loading efficiency (LE) showed no significant difference between OP and PO microcapsules (≈70 %), both significantly higher other starch microcapsules. OP and PO microcapsules exhibited sustained release, with enhanced antibacterial activity. Alginate hydrogels preserved about 60 % antioxidant and 90 % antibacterial activities of SEO against 2 h of UV radiation. These findings suggest that the order of modification could not affect the functional properties of final microcapsules. Additionally, the importance of alginate hydrogels as the protective and second wall material was disclosed.

Alginate-based composites as novel soil conditioners for sustainable applications in agriculture: A critical review

The development of alginate-based composites in agriculture to combat nutrient loss and drought for sustainable development has drawn increasing attention in the scientific community. Existing studies are however scattered, and the retention and slow-release mechanisms of alginate-based composites are not well understood. This paper systematically reviews the current literature on the preparation, characterization, and agricultural applications of various alginate-based composites. The synthesis methods of alginate-based composites are firstly summarized, followed by a review of available analytical techniques to characterize alginate-based composites for the attainment of their desired performance. Secondly, the performance and controlling factors for agricultural applications of alginate-based composites are discussed, including aquasorb, slow-release fertilizer, soil amendment, microbial inoculants, and controlled release of pesticides for pest management. Finally, suggestions and future perspectives are proposed to expand the applications of alginate-based composites for sustainable agriculture.

Effect of slow-release urea on intake, ingestive behavior, digestibility, nitrogen metabolism, microbial protein production, blood and ruminal parameters of sheep

We conducted two experiments. The first aimed to obtain and characterize microparticles of slow-release urea (SRU) using calcium alginate as the encapsulating agent. The second experiment evaluated their inclusion in sheep diets. In the first experiment, four treatments from a completely randomized design were employed to develop an SRU through the ionic gelification technique testing two drying methods (oven and lyophilizer) and addition or no of sulfur (S): SRU oven-dried with sulfur (MUSO) and without sulfur (MUO), SRU freeze-dried/lyophilized with (MUSL), and without sulfur (MUL). MUO exhibited better yield and encapsulation efficiency among these formulations than the others. Therefore, the second experiment was conducted to compare free urea (U) as control and three proportions (1%, 1.5%, and 2% of total dry matter) of MUO in the diet of sheep. Twenty-four non-castrated male Santa Ines lambs, with an average body weight of 22 ± 3.0 kg, were used and distributed in a completely randomized design with four treatments and six replications. The inclusion of 1% alginate-encapsulated urea (MUO1%) resulted in higher dry matter (DM) intake than free urea (p ≤ 0.05). MUO2% inclusion promoted higher NDF digestibility than U and MUO1%. MUO1% showed higher DM than MUO2% and higher NFC digestibility than U and MUO2% (p ≤ 0.05). Sheep fed MUO1.5% and MUO2% exhibited similar nutrient intake and digestibility. Sheep receiving MUO1% had higher N-intake, N-urinary, N-excretion total, N-digested, and N-retained compared to U. Sheep fed MUO1% showed greater N-retained (as % ingested and digested), microbial protein production, and efficiency when compared to other treatments (p ≤ 0.05). MUO2% addition (SRU) promoted the lowest microbial protein production and efficiency in sheep. MUO dietary inclusion increased feeding time and reduced idleness time compared to U, regardless of the MUO level (p ≤ 0.05). Adding MUO1% improved the intake efficiency of DM and NDF and resulted in more feed boli than the other MUO levels (p ≤ 0.05). Sheep receiving U had (4 h after fending) higher NH3-N, pH, and blood urea nitrogen (BUN) and lower TGL serum compared to sheep fed MUO (p ≤ 0.05), without significant difference among MUO levels (p > 0.05), except NH3-N was higher in MUO1.5% and MUO2% compared to MUO1.0%. The external ionic gelation technique proved suitable for urea microencapsulation in calcium alginate (3%), demonstrating high quality, efficiency, and yield. MUO represents a promising slow-release urea for ruminants and is recommended for sheep diets at an inclusion level of 1.0%. This inclusion level improves intake efficiency and nutrient digestibility, increases rumen nitrogen retention, and reduces BUN without compromising sheep health.

An efficient method for improving the stability of Monascus pigments using ionic gelation

BACKGROUND

Monascus pigments (Mps) are easily impacted by heating, pH and light, resulting in degradation. In this study, Mps were encapsulated by the ionic gelation method with sodium alginate (SA) and sodium caseinate (SC), as well as CaCl2 as a crosslinker. The encapsulated Mps SA/SC in four proportions (SA/SC: 1/4, 2/3, 3/2, 4/1, w/w). Then, the encapsulation efficiency and particle size of the SA/SC-Mps system were evaluated to obtain the optimal embedding conditions. Finally, the effects of heating, pH, light and storage on the stability of non-capsulated Mps and encapsulated Mps were assessed.

RESULTS

SA/SC = 2/3 (AC2) had higher encapsulation efficiency (74.30%) of Mps and relatively small particle size (2.02 mm). The AC2 gel beads were chosen for further investigating the stability of encapsulated Mps to heating, pH, light and storage. Heat stability experiments showed that the degradation of Mps followed first-order kinetics, and the encapsulated Mps had lower degradation rates than non-capsulated Mps. Encapsulation could reduce the effect of pH on Mps. The effects of ultraviolet light on the stability of Mps were considered, and showed that the retention efficiency of encapsulated Mps was 22.01% higher than that of non-capsulated Mps on the seventh day. Finally, storage stability was also evaluated under dark refrigerated conditions for 30 days, and the results indicated that encapsulation could reduce the degradation of Mps.

CONCLUSION

This study has proved that AC2 gel beads can improve the stability of Mps. Thus, the ionic gelation method is a promising encapsulation method to improve the stability of Mps. © 2023 Society of Chemical Industry.

Materials Engineering to Help Pest Control: A Narrative Overview of Biopolymer-Based Entomopathogenic Fungi Formulations

Biopolymer-based formulations show great promise in enhancing the effectiveness of entomopathogenic fungi as bioinsecticides. Chitosan and starch, among other biopolymers, have been utilized to improve spore delivery, persistence, and adherence to target insects. These formulations offer advantages such as target specificity, eco-friendliness, and sustainability. However, challenges related to production costs, stability, and shelf life need to be addressed. Recently, biomimetic lure and kill approaches based on biopolymers offer cost-effective solutions by leveraging natural attractants. Further research is needed to optimize these formulations and overcome challenges. Biopolymer-based formulations have the potential to revolutionize pest control practices, providing environmentally friendly and sustainable solutions for agriculture.

Protective Effect of Alginate Microcapsules with Different Rheological Behavior on Lactiplantibacillus plantarum 299v

Alginate encapsulation is a well-known technique used to protect microorganisms from adverse conditions. However, it is also known that the viscosity of the alginate is dependent on its composition and degree of polymerization and that thermal treatments, such as pasteurization and sterilization, can affect the structure of the polymer and decrease its protection efficiency. The goal of this study was to evaluate the protective effect of encapsulation, using alginates of different viscosities treated at different temperatures, on Lactiplantibacillus plantarum 299v under in vitro gastrointestinal conditions and cold storage at 4 °C and -15 °C, respectively. Steady- and dynamic-shear rheological tests were used to characterize the polymers. Thermal treatments profoundly affected the rheological characteristics of alginates with high and low viscosity. However, the solutions and gels of the low-viscosity alginate were more affected at a temperature of 117 °C. The capsules elaborated with high-viscosity alginate solution and pasteurized at 63 °C for 30 min provided better protection to the cells of L. plantarum 299v under simulated gastrointestinal and cold storage conditions.

Alginate microbeads incorporated with anthocyanins from purple corn (Zea mays L.) using electrostatic extrusion: Microencapsulation optimization, characterization, and stability studies

Microencapsulation of purple corn anthocyanins was carried out via an electrostatic extruder using alginate as a wall material. The influence of alginate concentration (1-2 %), extract concentration (20-30 %), and extrusion voltage (3-5 kV) on encapsulation efficiency and mean particle size was evaluated using response surface methodology. Optimal conditions were obtained to produce two different extract-loaded microbeads. Microbeads with the highest encapsulation efficiency (EE) and minimum particle size were achieved at 1 % alginate, 20 % extract, and 5 kV extrusion voltage (EEC3G = 70.26 %, EETPC = 91.59 %, particle size = 1.29 mm). In comparison, the microbeads with the efficient entrapment and maximum particle size were obtained at 1 % alginate, 26 % extract, and 3 kV (EEC3G = 81.15 %, EETPC = 91.01 %, particle size = 1.87 mm). Brunauer-Emmett-Teller (BET) surface area, pore size, and pore volume decreased after the inclusion of extract, with the lowest values reported for the smallest microbeads containing the extract. Scanning electron microscopy confirmed the results obtained by BET method and demonstrated fewer cracks and lower shrinkage of encapsulated samples. Fourier-transform infrared results proved the presence of anthocyanins and further possible interactions between phenolics and alginate. Stability studies revealed the color maintenance of anthocyanins-loaded microbeads during 4 weeks of storage at 4 °C and 8 °C. Moreover, the small and large particles showed a 7.6 and 3.4-fold reduction in degradation rate at 4 °C compared to their unencapsulated counterparts. Anthocyanins-loaded alginate microbeads retained over 80 % of cyanidin-3-glucoside at 4 °C and 8 °C, suggesting a promising potential of optimized microbeads for intelligent packaging applications.

Comparison of Immobilized and Free Amyloglucosidase Process in Glucose SyrupsProduction from White Sorghum Starch

Optimum conditions for glucose syrups production from white sorghum were studied through sequential liquefaction and saccharification processes. In the liquefaction process, a maximum dextrose equivalent (DE) of 10.98 % was achieved using 30 % (w/v) of starch and Termamyl ɑ-amylase from Bacillus licheniformis. Saccharification was performed by free and immobilized amyloglucosidase from Rhizopus mold at 1 % (w/v). DE values of 88.32 % and 79.95 % were obtained from 30 % (w/v) of starch with, respectively, free and immobilized enzyme. The immobilized Amyloglucosidase in calcium alginate beads showed reusable capacity for up to 6 cycles with 46 % of the original activity retained. The kinetic behaviour of immobilized and free enzyme gives Km value of 22.13 and 16.55 mg mL-1 and Vmax of 0.69 and 1.61 mg mL-1  min-1 , respectively. The hydrolysis yield using immobilized amyloglucosidase were lower than that of the free one. However, it is relevant to reuse enzyme without losing activity in order to trim down the overall costs of enzymatic bioprocesses as starch transformation into required products in industrial manufacturing. Hydrolysis of sorghum starch using immobilized amyloglucosidase represents a promising alternative towards the development of the glucose syrups production process and its utilization in various industries.

Physiologically Aggregated LacZ Applied in Trehalose Galactosylation in a Recycled Batch Mode

Galactooligosaccharides obtained via β-galactosidase transgalactosylation have health-promoting properties and are widely recognized as effective prebiotics. Trehalose-based galactooligosaccharides could be introduced into food and pharmaceutical industries similarly to trehalose. In light of this, new technological approaches are needed. Recently, in vivo enzyme immobilizations for recombinant proteins have been introduced, and physiological aggregation into active inclusion bodies (aIBs) has emerged as one such method of in vivo immobilization. To prepare LacZ β-galactosidase in the form of aIBs, we used a short 10 amino acid aggregation-prone tag. These native protein particles were simply washed from the cell lysate and applied in trehalose galactosylation in a recycled batch mode. In this study, aIBs entrapped in alginate beads, encapsulated in alginate/cellulose sulfate/poly(methylene-co-guanidine) capsules and magnetized were compared with free aIBs. Alginate/cellulose sulfate/PMCG capsules showed more suitable properties and applicability for biotransformation of trehalose at its high concentration (25%, w/v) and elevated temperature (50 °C).

Tween emulsifiers improved alginate-based dispersions and ionic crosslinked milli-sized capsules

The blending of surfactants might change the properties of alginate-based oil encapsulation preparations. Herein, the effects of Tween series (Tween 20, 40, 60, and 80) blending on the fish oil-encapsulated sodium alginate dispersions and calcium alginate capsules were studied. The results suggested Tween 80 showed better emulsifying properties than Span 80 for the alginate/surfactant emulsions. All the Tween series induced higher creaming stability than the sodium alginate-stabilized dispersion. Tween series blending did not change the sizes, decreased the water contents, and induced similar particle-like protrusions of calcium alginate capsules. Loading capacity and encapsulation efficiency of fish oil were dependent on the hydrophilic heads and fatty acid moieties of the Tween series. Tween series blending could increase the fish oil oxidative stability of the capsules. In the in vitro digestion process, Tween with saturated fatty acid moieties increased the free fatty acid release percentages. This work provided potential innovative processing technologies for improving the biological potency of fish oil.

Binary Alginate-Whey Protein Hydrogels for Antioxidant Encapsulation

Encapsulation of antioxidants in hydrogels, i.e., three-dimensional networks that retain a significant fraction of water, is a strategy to increase their stability and bioaccessibility. In fact, low oxygen diffusivity in the viscous gelled phase decreases the rate of oxidation. Moreover, some hydrocolloids such as alginate and whey proteins provide a pH-dependent dissolution mechanism, allowing the retention of encapsulated compounds in the gastric environment and their release in the intestine, where they can be absorbed. This paper reviews the information on alginate-whey protein interactions and on the strategies to use binary mixtures of these polymers for antioxidant encapsulation. Results showed that alginate and whey proteins strongly interact, forming hydrogels that can be modulated by alginate molecular mass, mannuronic acid: guluronic acid ratio, pH, Ca2+ or transglutaminase addition. Hydrogels of alginate and whey proteins, in the forms of beads, microparticles, microcapsules, and nanocapsules, generally provide better encapsulation efficiency and release properties for antioxidants with respect to the hydrogel of alginate alone. The main challenges for future studies are to extend knowledge on the interactions among three components, namely alginate, whey proteins, and the encapsulated bioactive compounds, and to investigate the stability of these structures under food processing conditions. This knowledge will represent the rationale basis for the development of structures that can be tailored to specific food applications.

Polysaccharides-Naturally Occurring Immune Modulators

The prevention of disease and infection requires immune systems that operate effectively. This is accomplished by the elimination of infections and abnormal cells. Immune or biological therapy treats disease by either stimulating or inhibiting the immune system, dependent upon the circumstances. In plants, animals, and microbes, polysaccharides are abundant biomacromolecules. Due to the intricacy of their structure, polysaccharides may interact with and impact the immune response; hence, they play a crucial role in the treatment of several human illnesses. There is an urgent need for the identification of natural biomolecules that may prevent infection and treat chronic disease. This article addresses some of the naturally occurring polysaccharides of known therapeutic potential that have already been identified. This article also discusses extraction methods and immunological modulatory capabilities.

Diversity of Bioinspired Hydrogels: From Structure to Applications

Hydrogels are three-dimensional networks with a variety of structures and functions that have a remarkable ability to absorb huge amounts of water or biological fluids. They can incorporate active compounds and release them in a controlled manner. Hydrogels can also be designed to be sensitive to external stimuli: temperature, pH, ionic strength, electrical or magnetic stimuli, specific molecules, etc. Alternative methods for the development of various hydrogels have been outlined in the literature over time. Some hydrogels are toxic and therefore are avoided when obtaining biomaterials, pharmaceuticals, or therapeutic products. Nature is a permanent source of inspiration for new structures and new functionalities of more and more competitive materials. Natural compounds present a series of physico-chemical and biological characteristics suitable for biomaterials, such as biocompatibility, antimicrobial properties, biodegradability, and nontoxicity. Thus, they can generate microenvironments comparable to the intracellular or extracellular matrices in the human body. This paper discusses the main advantages of the presence of biomolecules (polysaccharides, proteins, and polypeptides) in hydrogels. Structural aspects induced by natural compounds and their specific properties are emphasized. The most suitable applications will be highlighted, including drug delivery, self-healing materials for regenerative medicine, cell culture, wound dressings, 3D bioprinting, foods, etc.

Multifunctional Platform for Covalent Titanium Coatings: Micro-FTIR, XPS, and NEXAFS Characterizations

This work aims at preparing and characterizing a versatile multifunctional platform enabling the immobilization of macromolecules on a titanium surface by robust covalent grafting. Functionalized titanium is widely used in the biomedical field to improve its properties. Despite its high biocompatibility and osteointegrability, titanium implants are not very stable in the long term due to the onset of inflammation and bacterial infections. The proposed method allows the superficial insertion of three different organic linkers to be used as anchors for the attachment of biopolymers or bioactive molecules. This strategy used green solvents and is a good alternative to the proposed classic methods that employ organic solvents. The uniformly modified surfaces were characterized by micro-Fourier transform infrared spectroscopy (micro-FTIR), X-ray Photoelectron spectroscopy (XPS) and Near-Edge X-ray Absorption Fine Structure (NEXAFS). The latter made it possible to assess the orientation of the linker molecules with respect to the titanium surface. To test the efficiency of the linkers, two polymers (alginate and 2-(dimethylamino)-ethyl methacrylate (PDMAEMA)), with the potential ability to increase biocompatibility, were covalently attached to the titanium surfaces. The obtained results are a good starting point for the realization of stable polymeric coatings permanently bonded to the surface that could be used to extend the life of biomedical implants.

Encapsulation of Carvacrol-Loaded Nanoemulsion Obtained Using Phase Inversion Composition Method in Alginate Beads and Polysaccharide-Coated Alginate Beads

Nanoemulsions have been widely studied as lipophilic compound loading systems. A low-energy emulsification method, phase inversion composition (PIC), was used to prepare oil-in-water nanoemulsions in a carvacrol-coconut oil/Tween 80^®-(linoleic acid-potassium linoleate)/water system. The phase behaviour of several emulsification paths was studied and related to the composition range in which small-sized stable nanoemulsions could be obtained. An experimental design was carried out to determine the best formulation in terms of size and stability. Nanoemulsions with a very small mean droplet diameter (16-20 nm) were obtained and successfully encapsulated to add carvacrol to foods as a natural antimicrobial and antioxidant agent. They were encapsulated into alginate beads by external gelation. In order to improve the carvacrol kinetics release, the beads were coated with two different biopolymers: chitosan and pullulan. All formulations were analysed with scanning electron microscopy to investigate the surface morphology. The release patterns at different pHs were evaluated. Different kinetics release models were fitted in order to study the release mechanisms affecting each formulation. Chitosan-coated beads avoided the initial release burst effect, improving the beads' structure and producing a Fickian release. At basic pH, the chitosan-coated beads collapsed and the pullulan-coated beads moderately improved the release pattern of the alginate beads. For acid and neutral pHs, the chitosan-coated beads presented more sustained release patterns.

Alginate Based Core-Shell Capsules Production through Coextrusion Methods: Recent Applications

Encapsulation is used in various industries to protect active molecules and control the release of the encapsulated materials. One of the structures that can be obtained using coextrusion encapsulation methods is the core-shell capsule. This review focuses on coextrusion encapsulation applications for the preservation of oils and essential oils, probiotics, and other bioactives. This technology isolates actives from the external environment, enhances their stability, and allows their controlled release. Coextrusion offers a valuable means of preserving active molecules by reducing oxidation processes, limiting the evaporation of volatile compounds, isolating some nutrients or drugs with undesired taste, or stabilizing probiotics to increase their shelf life. Being environmentally friendly, coextrusion offers significant application opportunities for the pharmaceutical, food, and agriculture sectors.

Alginate Core-Shell Capsules Production through Coextrusion Methods: Principles and Technologies

This paper provides an overview of coextrusion methods for encapsulation. Encapsulation involves the coating or entrapment of a core material such as food ingredients, enzymes, cells, or bioactives. Encapsulation can help compounds add to other matrices, stabilize compounds during storage, or enable controlled delivery. This review explores the principal l coextrusion methods available that can be used to produce core-shell capsules through the use of coaxial nozzles. Four methods for encapsulation by coextrusion are examined in detail, including dripping, jet cutting, centrifugal, and electrohydrodynamic systems. The targeted capsule size determines the appropriate parameters for each method. Coextrusion technology is a promising encapsulation technique able to generate core-shell capsules in a controlled manner, which can be applied to cosmetic, food, pharmaceutical, agriculture, and textile industries. Coextrusion is an excellent way to preserve active molecules and present a significant economic interest.

Antioxidant and Antiradical Activities of Hibiscus sabdariffa L. Extracts Encapsulated in Calcium Alginate Spheres

The interest in natural sources with high antioxidant powder has recently increased in several sectors. Ionic gelation methods could be used to protect bioactive substances to control the kinetics and release of these ingredients to the food matrix. This study dealt with the evaluation of the antioxidant capacity and scavenging activity of extracts of Hibiscus Sabdariffa L. (HSL) (with 50% ethanol) encapsulated in calcium alginate spheres as a new source for preserving food against oxidative damage. Their antioxidant activity was measured in different o/w emulsions in which HSL spheres reduced the formation of hydroperoxides (~80%) and thiobarbituric-acid-reactive substance products (~20%). The scavenging activity of HSL extracts was measured in different food simulants (water, water acidified with 3% acetic acid, ethanol at 50%, and pure ethanol), and corresponded to 0.20–0.43, 0.31–0.62, and 11.13–23.82 mmol Trolox/mL extract for Trolox equivalent antioxidant capacity (TEAC), 2,2-diphenylpicrylhydrazyl (DPPH), and oxygen radical absorbance capacity (ORAC) assays, respectively. In general, the best antiradical activity was observed in the ethanolic and acidified mediums, in which the highest concentration of released polyphenols ranged from 0.068 to 0.079 mg GAE/mL. This work indicates the potential of alginate spheres for encapsulating antioxidant compounds as an innovative strategy for several industrial applications.

Environmentally friendly starch/alginate aerogels for copper adsorption from aqueous media. A microstructural and kinetic study

This work investigated the synthesis and characterization of alginate/starch porous materials and their application as copper ions adsorbents from aqueous media. Initially, pregel aqueous solutions with different biopolymer concentrations (1, 3, and 5% w/w) and alginate contents (25, 50, and 75% w/w) were prepared. Hydrogel formation was performed by internal and external gelation methods. Finally, the drying step was done via CO2sc leading to aerogels and via freeze-drying leading to cryogels. Process parameters influence on the final properties of materials was evaluated by BET isotherms, SEM, EDS, and TGA. Regardless the gelation method applied, interesting materials with meso- and macro-pore structure were prepared from pregel mixtures with 3% w/w biopolymer concentration and an alginate content of only 25% w/w. Low alginate content reduces the final cost of the materials. Concerning copper removal, the adsorption data were well fitted to the pseudo-second order kinetic model for aerogels and cryogels, showing aerogels the highest adsorption capacity (40 mg/g) and removal efficiency (∼ 92%). Materials demonstrated excellent reusability throughout five consecutive adsorption/desorption cycles. Hence, environmentally friendly materials with a high practical value as low-cost bioadsorbents were synthesized, having great performance in the removal of copper ions from aqueous solution.

Effect of gelation technique on lipid digestibility of emulsion-loaded alginate microparticles: a systematic review and meta-analysis

Alginate microparticles fabricated via calcium gelation or layer-by-layer assembly are commonly used for encapsulating emulsions. In this study, the impact of these two gelation methods on the lipid digestibility of emulsions was reviewed through a systematic screening of relevant studies. From the literature search (Scopus, PubMed, and Web of Science databases), 604 records were screened and 25 articles were included in the analysis. The fold change of free fatty acid release rate at the end of in vitro digestion process between alginate-encapsulated emulsion and emulsions not encapsulated by alginate was calculated for calcium gelation (weighted mean of response ratio 0.64, 95% CI 0.54-0.75) and layer-by-layer assembly (weighted mean of response ratio 0.89, 95% CI 0.81-0.98). Alginate-calcium hydrogels showed stronger inhibition of the extent of lipid digestion than alginate-coated multilayer emulsions. The structural and particle size differences between alginate microparticles acquired using different techniques may contribute to this phenomenon.

Enhanced Functionality and Bio-Accessibility of Composite Pomegranate Peel Extract-Enriched "Boba Balls"

“Boba balls” or pearls have recently gained popularity for beverages or food toppings. “Boba balls” could be developed into functional foods by the encapsulation of bioactive compounds. In this study, gelatin/sodium alginate composite “Boba balls” enriched with pomegranate peel extract (PPE) at different concentrations (0, 1, 2, and 3%) were prepared. They were characterized in terms of physical, rheological, textural, morphological, and sensory properties, as well as in vitro digestion, bio-accessibility, and release kinetic of PPE. Adding PPE improved the “Boba” mix’s viscoelasticity and decreased the “Boba balls”’ hardness. The increasing PPE ratio significantly (p < 0.05) increased the antioxidant capacity and total phenolic content. The addition of PPE preserved the spherical shape of the “Boba balls”, and as the PPE ratio increased, new junction zones were observed in SEM images. The in vitro digestibility of PPE was significantly (p < 0.05) improved by preserving PPE from the mouth and gastric medium, and “Boba balls” showed the highest release and bio-accessibility in the intestinal medium. Consequently, PPE as a by-product could be successfully used at 2% concentration for enhancing the functionality and bio-accessibility of “Boba balls” without affecting sensory properties.

Self-floating capsule of algicidal bacteria Bacillus sp. HL and its performance in the dissolution of Microcystis aeruginosa

Algicidal bacteria is considered as an efficient and environmentally friendly approach to suppress Microcystis aeruginosa (M. aeruginosa). However, algicidal bacteria in natural water is limited during the practical application due to the interference of external factors and the low reuse capability. In this study, a bio-degradation capsule for M. aeruginosa is prepared by bio-compatible sodium alginate (SA) compositing with eco-friendly ethyl cellulose (EC) to improve the property and reuse capability of algicidal bacteria. Bacterial strain HL was well immobilized and the capsule was obtained with 2% of SA, 3% of calcium chloride (CaCl₂) and 3% of EC. It has been proved that capsules immobilizing bacteria HL shows considerable advantage over traditional bio-treatment systems (free-living bacteria) and good reusable performance. A better algicidal rate of 77.67% ± 1.14% at 7th day was obtained with the use of capsule embedding 50 mL of algicidal bacteria, enhanced by 11.05% comparing with same amount of free-living bacteria. Moreover, the algicidal rate of M. aeruginosa still reached 68.57% ± 2.88% after three times repetitive use. The effect of capsules on the fluorescence and antioxidant system of M. aeruginosa indicated that the photosystems were irreversibly damaged and the antioxidant response of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were significantly induced. Overall, capsules prepared in this study can provide a desirable environment for algicidal bacteria HL and ensure algicidal bacteria to in-situ work well in inhibiting booms of algae.

Sodium Alginate—Natural Microencapsulation Material of Polymeric Microparticles

From the multitude of materials currently available on the market that can be used in the development of microparticles, sodium alginate has become one of the most studied natural anionic polymers that can be included in controlled-release pharmaceutical systems alongside other polymers due to its low cost, low toxicity, biocompatibility, biodegradability and gelatinous die-forming capacity in the presence of Ca²⁺ ions. In this review, we have shown that through coacervation, the particulate systems for the dispensing of drugs consisting of natural polymers are nontoxic, allowing the repeated administration of medicinal substances and the protection of better the medicinal substances from degradation, which can increase the capture capacity of the drug and extend its release from the pharmaceutical form.

Exploiting Polymeric Films as a Multipurpose Drug Delivery System: a Review

Polymeric films are drug delivery systems that maintain contact with the delivery tissue and sustain a controlled release of therapeutic molecules. These systems allow a longer time of drug contact with the target site in the case of topical treatments and allow the controlled administration of drugs. They can be manufactured by various methods such as solvent casting, hot melt extrusion, electrospinning, and 3D bioprinting. Furthermore, they can employ various polymers, for example PVP, PVA, cellulose derivatives, chitosan, gelling gum, pectin, and alginate. Its versatility is also applicable to different routes of administration, as it can be administered to the skin, oral mucosa, vaginal canal, and eyeballs. All these factors allow numerous combinations to obtain a better treatment. This review focuses on exploring some possible ways to develop them and some particularities and advantages/disadvantages in each case. It also aims to show the versatility of these systems and the advantages and disadvantages in each case, as they bring the opportunity to develop different medicines to facilitate therapies for the most diverse purposes .

Effects of Span surfactants on the preparation and properties of fish oil-loaded sodium alginate-stabilized emulsions and calcium alginate-stabilized capsules

Encapsulation is an efficient protection method for oil in both liquid (e.g., emulsion) and solid (e.g., capsule) forms. In this work, we mainly explored the effect of different Span surfactants (Span 20, Span 40, Span 60, and Span 80) on the properties of fish oil-loaded sodium alginate/Span-stabilized emulsions and calcium alginate/Span capsules. For emulsions, different Span surfactants induced different initial droplet sizes and emulsion creaming stability. The emulsifying stability of Span surfactants for sodium alginate/Span-stabilized emulsions was: Span 40 < Span 20 < Span 80 < Span 60. For capsules, a Span addition could decrease the water content and change the particle morphologies. Compared with the calcium alginate capsule (12.2 %), the Span 60 addition increased the fish oil loading ratio (20.2 %). Moreover, the addition of Span 20, Span 60, and Span 80 decreased the production of primary lipid hydroperoxides of the capsules. Span surfactants had different effects on the free fatty acid release of calcium alginate capsules in the gastrointestinal digestion process, such that: Span 40 > Span 80 > control > Span 20 > Span 60. This work suggests that Span surfactants are capable of adjusting and optimizing the properties of emulsions and capsules for potential food applications.

Multitasking smart hydrogels based on the combination of alginate and poly(3,4-ethylenedioxythiophene) properties: A review

Poly(3,4-ethylenedioxythiophene) (PEDOT), a very stable and biocompatible conducting polymer, and alginate (Alg), a natural water-soluble polysaccharide mainly found in the cell wall of various species of brown algae, exhibit very different but at the same complementary properties. In the last few years, the remarkable capacity of Alg to form hydrogels and the electro-responsive properties of PEDOT have been combined to form not only layered composites (PEDOT-Alg) but also interpenetrated multi-responsive PEDOT/Alg hydrogels. These materials have been found to display outstanding properties, such as electrical conductivity, piezoelectricity, biocompatibility, self-healing and re-usability properties, pH and thermoelectric responsiveness, among others. Consequently, a wide number of applications are being proposed for PEDOT-Alg composites and, especially, PEDOT/Alg hydrogels, which should be considered as a new kind of hybrid material because of the very different chemical nature of the two polymeric components. This review summarizes the applications of PEDOT-Alg and PEDOT/Alg in tissue interfaces and regeneration, drug delivery, sensors, microfluidics, energy storage and evaporators for desalination. Special attention has been given to the discussion of multi-tasking applications, while the new challenges to be tackled based on aspects not yet considered in either of the two polymers have also been highlighted.

Quaternized Sodium Alginate-g-Ethyl-Oxazoline Copolymer Brushes and Their Supramolecular Networks via Hydrogen Bonding

Novel copolymer brushes of quaternized sodium alginate-g-(2-ethyl-2-oxazoline)_n are achieved by the grafting reaction of 2-ethyl-2-oxazoline (EOX) from benzyl bromide groups in quaternized sodium alginate (QSA). The average number of (EOX)_n structural units is mediated from 1 to 5 by changing the molar ratio of the EOX monomer to benzyl bromide side groups. There exists obvious microphase separation between the QSA backbone and (EOX)_n segments in the copolymer brushes due to their thermodynamic incompatibility. The strong hydrogen-bonding interaction between -OH groups in the backbone and N─C═O groups in (EOX)_n segments is helpful for the construction of reversible supramolecular networks. The copolymer brushes show low cytotoxicity for HeLa cells and good antibacterial properties for Escherichia coli and Staphylococcus aureus for the contribution of hydrophilic (EOX)_n segments and antibacterial activity of the quaternary ammonium. The antiprotein behavior of polymer surfaces is improved after rearrangement of (EOX)_n segments by tetrahydrofuran (THF) vapor induction. These copolymer brushes have good prospects for biomedical applications.