Sugar Alcohol-Based Deep Eutectic Solvents as Potato Starch Plasticizers

Deep Eutectic Solvent Eutectogels for Delivery of Broad-Spectrum Antimicrobials

Gel-based wound dressings have gained popularity within the healthcare industry for the prevention and treatment of bacterial and fungal infections. Gels based on deep eutectic solvents (DESs), known as eutectogels, provide a promising alternative to hydrogels as they are non-volatile and highly tunable and can solubilize therapeutic agents, including those insoluble in hydrogels. A choline chloride:glycerol-cellulose eutectogel was loaded with numerous antimicrobial agents including silver nanoparticles, black phosphorus nanoflakes, and commercially available pharmaceuticals (octenidine dihydrochloride, tetracycline hydrochloride, and fluconazole). The eutectogels caused >97% growth reduction in Gram-positive methicillin-resistant Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa bacteria and the fungal species Candida albicans.

Co-Plasticization of Starch with Glycerol and Isosorbide: Effect on Retrogradation in Thermo-Plastic Cassava Starch Films

Thermoplastic starch (TPS) has emerged as an essential alternative to produce environmentally friendly packaging; however, retrogradation is a disadvantage that affects its shelf life. This study analyzed the co-plasticizing effect of isosorbide on the mechanical, thermal, physicochemical, and microstructural properties and the retrogradation of films obtained by blown film extrusion from thermoplasticized starch with mixtures of glycerol and isosorbide in different ratios (3:0, 2:1, 1:2, and 0:3, respectively). The results showed that the higher concentration of isosorbide significantly increased the tensile strength; however, it reduced the elongation. Retrogradation modeled using the Avrami equation showed that the presence of isosorbide reduced the retrogradation rate (k) and modified the recrystallization mechanism (n). The relative crystallinity in the plasticized TPS films was reduced to 89%, and the adsorption significantly decreased. Isosorbide was very important in reducing the retrogradation of TPS. The best performance was obtained with the 2:1 ratio of glycerol/isosorbide due to the synergistic effect between the plasticizers. The results would allow tuning the properties of TPS films by combining glycerol/isosorbide in different ratios, which enables the design of materials tailored to potential application requirements.

Study on Physicochemical Properties of Biocomposite Films with Spent Coffee Grounds as a Filler and Their Influence on Physiological State of Growing Plants

The aim of the study was to plasticize corn starch with two selected urea (U)-rich plasticizers: choline chloride (CC):U or betaine (B):U eutectic mixtures at a molar ratio of 1:5 with a presence of spent coffee grounds as a filler. The biomaterials were prepared via a solventless one-step extrusion method and then extrudates were thermoformed using compression molding into sheets. The materials were characterized using mechanical and sorption tests, TGA, DMTA and FTIR. Additionally, a study on the biodegradation and remaining nitrogen content in soil was conducted. For the first time, an influence on physiological state of growing plants of the materials presence in soil was investigated. The addition of the coffee filler slightly increased the mechanical properties and decreased the swelling degree of the materials. The DMTA results indicated that biocomposites were easily thermoformable and the high filler addition (20 pph per polymer matrix) did not affect the processability. According to the biodegradation test results, the materials disappeared in soil within ca. 70 days. The results from this study on the physiological state of growing plants revealed that the materials, especially plasticized with CCU, did not exhibit any toxic effect on the yellow dwarf bean. The percentage of total nitrogen in the soil substrate in comparison with the control increased indicating an effective release of nitrogen from the TPS materials into the substrate.

Design and application of self-healable polymeric films and coatings for smart food packaging

Smart packaging materials enable active control of parameters that potentially influence the quality of a packaged food product. One type of these that have attracted extensive interest is self-healable films and coatings, which show the elegant, autonomous crack repairing ability upon the presence of appropriate stimuli. They exhibit increased durability and effectively lengthen the usage lifespan of the package. Over the years, extensive efforts have been paid to the design and development of polymeric materials that show self-healing properties; however, till now most of the discussions focus on the design of self-healable hydrogels. Efforts devoted to delineating related advances in the context of polymeric films and coatings are scant, not to mention works reviewing the use of self-healable polymeric materials for smart food packaging. This article fills this gap by offering a review of not only the major strategies for fabrication of self-healable polymeric films and coatings but also the mechanisms of the self-healing process. It is hoped that this article cannot only provide a snapshot of the recent development of self-healable food packaging materials, but insights into the optimization and design of new polymeric films and coatings with self-healing properties can also be gained for future research.

Potato thermoplastic starch nanocomposite films reinforced with nanocellulose

Potato is a widely available feedstock with biocompatibility and biodegradability properties, making it a strong candidate for producing thermoplastic starch. The application of thermoplastic starch to replace petroleum-based plastic as a sustainable and environmentally friendly approach led to its further improvement through various techniques such as modification and filler reinforcement. Numerous studies have been done addressing the properties enhancement of potato thermoplastic starch through filler reinforcement including nanocellulose. This review focus on the recent and future potential of potato-based starch as one of the feedstocks for producing potato thermoplastic starch composites reinforced with nanocellulose.

Research on deep eutectic solvents for the construction of humidity-responsive cellulose nanocrystal composite films

Photonic crystal materials based on cellulose nanocrystals (CNC), which are environmentally responsive and green, have attracted widespread attention. To overcome the brittleness of CNC films, many researchers have explored functional additives to improve their performance. In this study, a new green deep eutectic solvents (DESs) and an amino acid-based natural deep eutectic solvents (NADESs) were introduced into CNC suspensions for the first time, and hydroxyl-rich small molecules (glycerol, sorbitol) and polymers (polyvinyl alcohol, polyethylene glycol) were coassembled with the DESs and NADESs to form three-component composite films. The CNC/G/NADESs-Arg three-component film reversibly changed color from blue to crimson as the relative humidity rose from 35 % to 100 %; additionally, the elongation at break increased to 3.05 %, and the Young's modulus decreased to 4.52 GPa. The hydrogen bond network structure provided by trace amounts of the DESs or NADESs not only improved the mechanical properties of the composite films but also increased their water absorption capacities without destroying their optical activities. This allows for the development of more stable CNC films and creates potential for biological applications in the future.

Advances in green solvents for production of polysaccharide-based packaging films: Insights of ionic liquids and deep eutectic solvents

The problems with plastic materials and the good film-forming properties of polysaccharides motivated research in the development of polysaccharide-based films. In the last 5 years, there has been an explosion of publications on using green solvents, including ionic liquids (ILs), and deep eutectic solvents (DESs) as candidates to substitute the conventional solvents/plasticizers for preparations of desired polysaccharide-based films. This review summarizes related properties and recovery of ILs and DESs, a series of green preparation strategies (including pretreatment solvents/reaction media, ILs/DESs as components, extraction solvents of bioactive compounds added into films), and inherent properties of polysaccharide-based films with/without ILs and DESs. Major reported advantages of these new solvents are high dissolving capacity of certain ILs/DESs for polysaccharides (i.e., up to 30 wt% for cellulose) and better plasticizing ability than traditional plasticizers. In addition, they frequently display intrinsic antioxidant and antibacterial activities that facilitate ILs/DESs applications in the processing of polysaccharide-based films (especially active food packaging films). ILs/DESs in the film could also be further recycled by water or ethanol/methanol treatment followed by drying/evaporation. One particularly promising approach is to use bioactive cholinium-based ILs and DESs with good safety and plasticizing ability to improve the functional properties of prepared films. Whole extracts by ILs/DESs from various byproducts can also be directly used in films without separation/polishing of compounds from the extracting agents. Scaling-up, including costs and environmental footprint, as well as the safety and applications in real foods of polysaccharide-based film with ILs/DESs (extracts) deserves more studies.

Characterization of Thermoplastic Starch Plasticized with Ternary Urea-Polyols Deep Eutectic Solvent with Two Selected Fillers: Microcrystalline Cellulose and Montmorillonite

The aim of the study was to prepare and characterize composite materials based on thermoplastic starch (TPS)/deep eutectic solvent (DES). Potato starch was plasticized with ternary DES: urea:glycerol:sorbitol and modified with the selected fillers: microcrystalline cellulose and sodium montmorillonite. Films were prepared via twin-screw extrusion and thermocompression of the extrudates. Then, the physicochemical properties of the TPS films were examined. The ternary DES effectively plasticized the polysaccharide leading to a highly amorphous structure of the TPS (confirmed via mechanical tests, DMTA and XRD analyses). An investigation of the behavior in water (swelling and dissolution degree) and water vapor transmission rate of the films was determined. The introduction of the two types of fillers resulted in higher tensile strength and better barrier properties of the composite TPS films. However, montmorillonite addition exhibited a higher impact than microcrystalline cellulose. Moreover, a cone calorimetry analysis of the TPS materials revealed that they showed better fire-retardant properties than TPS plasticized with a conventional plasticizer (glycerol).

Deep Eutectic Solvents for Biotechnology Applications

Deep eutectic solvents (DESs) are an alternative to traditional organic solvents and ionic liquids and meet the requirements of "green" chemistry. They are easy to prepare using low-cost constituents, are non-toxic and biodegradable. The review analyzes literature on the use of DES in various fields of biotechnology, provides data on the types of DESs, methods for their preparation, and properties. The main areas of using DESs in biotechnology include extraction of physiologically active substances from natural resources, pretreatment of lignocellulosic biomass to improve enzymatic hydrolysis of cellulose, production of bioplastics, as well as a reaction medium for biocatalytic reactions. The aim of this review is to summarize available information on the use of new solvents for biotechnological purposes.

Deep Eutectic Solvents for Starch Treatment

In this review, the application of deep eutectic solvents (DESs) as starch solvents, plasticizers and for other treatment has been described. Starch, as one of the most abundant biopolymers, is considered for forming new biodegradable materials. This new approach, referring to applying deep eutectic solvents for dissolving starch, its plasticization and other modifications, was presented. A DES could be a good alternative for common starch plasticizers (e.g., glycerol, urea) as well as recently considered ionic liquids. The high variety of DES component combinations makes it possible to obtain materials with the properties specific for given applications.

Starch as a reinforcement agent for poly(ionic liquid) hydrogels from deep eutectic solvent via frontal polymerization

For the first time, conductive starch/poly(ionic liquid) hydrogels from a polymerizable deep eutectic solvent (DES) by frontal polymerization (FP) were reported. The solubility and dispersibility for starch granules in the polymerizable DES was investigated. The effects of starch content on FP behaviors, mechanical properties and electrical conductivity of composite hydrogels were studied. Results showed that starch could be partially dissolved and dispersed in the DES. Comparing with the pure poly(ionic liquid) hydrogel from DES (the tensile strength was 41 K Pa), the tensile strength of composite hydrogel could increased by 3.07 times and reached 126 K Pa. When the fixed strain was 80 %, its compressive strength could increase by 6 times and reaches 16.8 MPa. The main reason was that there was a strong interfacial interaction between starch and the polymer hydrogel network. The starch/poly(ionic liquid) composite hydrogels also had good electrical conductivity. Absorption of water could increase the conductivity of the composite hydrogel significantly.

Non-volatile conductive gels made from deep eutectic solvents and oxidised cellulose nanofibrils

Ionogels offer huge potential for a number of applications including wearable electronics and soft sensors. However, their synthesis has been limited and often relies on non-renewable or non-biocompatible components. Here we present a novel two-component ionogel made using just deep eutectic solvents (DESs) and cellulose. DESs offer a non-volatile alternative to hydrogels with highly tuneable properties including conductivity and solvation of compounds with widely varying hydrophobicity. DESs can be easily made from cheap, biodegradable and biocompatible components. This research presents the characterisation of a series of soft conductive gels made from deep eutectic solvents (DESs), specifically choline chloride-urea and choline chloride-glycerol, with the sole addition of TEMPO-oxidised cellulose nanofibrils (OCNF). A more liquid-like rather than gel-like conductive material could be made by using the DES betaine-glycerol. OCNF are prepared from sustainable sources, and are non-toxic, and mild on the skin, forming gels without the need for surfactants or other gelling agents. These DES-OCNF gels are shear thinning with conductivities up to 1.7 mS cm^-1 at ∼26 °C. Given the thousands of possible DESs, this system offers unmatched tunability and customisation for properties such as viscosity, conductivity, and yield behaviour.

Deep eutectic solvents based on urea, polyols and sugars for starch treatment

Deep eutectic solvents (DES) based on urea (U), polyols (glycerol -G, sorbitol - S) and monosugars (glucose - Glu, fructose - Fru) were obtained, thermally characterized and used for potato starch treatment: dissolution and plasticization. The polysaccharide was dissolved in U/glycerol mixtures forming transparent, non-retrograded gels. The dissolution process was confirmed by microscopic observations and DSC analysis. Plasticizing efficiency of DES in thermoplasticized starch (TPS) via compression molding was investigated using mechanical tests, DMTA, XRD, TGA and FTIR analysis. Although all studied DES were able to plasticize starch effectively, the most flexible films were with urea/glycerol mixture: the highest elongation at break exceed 200%. XRD analysis confirmed high amorphization of starch with the urea-based DES after thermocompression. Moreover, introduction of urea as DES inhibited its recrystallization in the polysaccharide matrix.