Polysaccharides, Volume 5, Issue 2 (June 2024) – 8 articles

In times of increasing demand for resources, processing various waste materials is becoming more economically and ecologically viable. Red mud is a waste material that originates from the bauxite process, also known as the Bayer process. Red mud, due to its high alkalinity and heavy metal content, is often stored in landfills, which can lead to accidents such as those in Brazil or Hungary, especially if the storage takes place above ground. Red mud contains not only iron and aluminum residues but also other economically valuable metals such as manganese, titanium, cadmium, or cobalt. Currently, only 4 million tons of the annual production of 150 million tons are utilized in various industries, which is a relatively small amount. Typically, only the iron content is further processed, leaving other potential resources untapped. Chitin has a high binding capacity for various trivalent and divalent metal ions, making it a suitable material for separating red mud into its components. It has been demonstrated that chitin can effectively remove aluminum, barium, cadmium, cobalt, copper, manganese, iron, nickel, lead, strontium, and various lanthanides from a red mud-like sludge. The elements bound to chitin can be easily removed using wet chemistry. Biologically compatible substances are predominantly used in this process, with few exceptions. The removal of elements from red sludge or other mining wastewater using chitin is a viable alternative to traditional mining methods. Full article

Polysaccharide-based nanoformulations with tailored hydrophobic properties have become a frontier in nanomedicine applications. Herein, highly hydrophobicized hydroxyethyl starch (HES) conjugates were synthesized by grafting stearic acid (SA) with HES via a carbodiimide-mediated reaction. A detailed NMR characterization of HES and the conjugates was studied to obtain structural information. The grafting ratio of the stearate-HES (St-HES) conjugates was determined from ¹H NMR spectra as 29.4% (St-HES29.4) and 60.3% (St-HES60.3). Thermal analyses and X-ray diffractograms suggested an entire transition from amorphous HES to a semicrystalline (St-HES60.3) character upon increasing the degree of grafting. Both conjugates, St-HES29.4 and St-HES60.3, were able to form self-assembled particles with a diameter of 130.7 nm and 152.5 nm, respectively. SEM images showed that the self-aggregates were mostly spherical in shape. These conjugates can be employed to entrap highly hydrophobic drugs with an increased encapsulation efficiency and loading capacity. Full article

The development of active food packaging is desirable for food safety and to avoid food loss and waste. In this work, we developed antioxidant bilayer films combining extrusion and electrospinning techniques. These films consisted of a first layer of thermoplastic cornstarch (TPS), incorporated with microcrystalline cellulose (MCC). The second layer consisted of gallic acid (GA) encapsulated at different concentrations in 1:1 chitosan/poly(ethylene-co-vinyl alcohol) (CS/EVOH) nanofibers. This layer was directly electrospun onto the TPS/MCC film. The morphological, structural, wettability, permeability to oxygen, and antioxidant properties were investigated for the first layer and the bilayer films. Water contact angle measurements revealed the hydrophobic nature of the first layer (θ₀ = 100.6°). The oxygen permeability (OP) was accessed through the peroxide value (PV) of canola oil, kept in containers covered by the films. PV varied from 66.6 meq/kg for the TPS/MCC layer to 60.5 meq/kg for a bilayer film. Intermolecular hydrogen bonds, mediated by GA, contributed slightly to improving the mechanical strength of the bilayer films. The bilayer film incorporated with GA at 15.0% reached a radical scavenging activity against the DPPH radical of (903.8 ± 62.2) μmol.L⁻¹.Eq. Trolox.g⁻¹. This result proved the effectiveness of the GA nanoencapsulation strategy. Full article

Bead-free nanofibrous scaffolds composed of PVOH/keratin/chitosan were prepared using electrospinning after optimising the process parameters using a Box–Behnken experimental design. Two quadratic models were developed to optimise the fibre diameter and the diameter of fibre beads considering the voltage, flow rate, spinning distance, and amount of biopolymer as independent variables. All independent variables were found to be significant in determining responses, although not all interactions among these were significant. The models were highly effective in describing responses, with an R² of 98.58 and 99.67%. The optimum conditions were determined to be 15.82 kV voltage, 0.25 mL/h flow rate, 105 mm spinning distance, and 30% biopolymers. The accuracy of the models was verified and found to be within an acceptable range. The bead-free nanofibrous scaffold exhibited no cytotoxicity to Human Aneuploid Immortal Keratinocyte (HaCaT) and Normal Human Dermal Fibroblast (NHDF) cell lines, enabling cell adhesion and proliferation. Both cell lines remained attached with perfect cell morphology when co-cultured on the scaffold for 30 days, indicating the scaffold’s potential for biomedical applications. Full article

Hot spring (HS) waters manifest diverse positive effects on the skin due to their unique chemical compositions. Sodium hyaluronate acid (HA) comprises N-acetylglucosamine and D-glucuronic acid, and distinguishes itself with superior qualities in skin regeneration, providing moisturizing and anti-aging benefits. The combination of HA with HS water is widely applied across ophthalmology, pneumology, nutrition, and cosmetics. This study delved into the application of HA in cosmetology, with a focus on its interaction with HS water and its effects on moisture retention and promoting wound healing. In particular, with the alkaline pH levels of the Yumoto HS, HA molecules may undergo dissociation to be ionized resulting in a negatively charged polymer and interacting with positively charged ions in the HS water through electrostatic interactions. The shifted peaks in the FTIR result and zeta potential shifts to a less negative region in the case of HA-HS compared to HA-DI indicate an ionic interaction between HS water and HA. Moisture tests confirmed the sustained hydration when HA is dissolved in HS water, underscoring its potential to improve skin hydration at certain concentrations, specifically at 0.5% and 1%. Additionally, MTT assay results demonstrated that HS water stimulates the growth of fibroblast cells compared to distilled water, implying its potential beneficial effect in wound healing. These findings suggested the multifaceted benefits of HAHS in skincare, highlighting its role in enhancing skin hydration and potentially accelerating wound healing processes, thus presenting avenues for the development of advanced cosmeceutical formulations. Full article

Cellulose nanocrystals (CNCs) are bio-based materials able to be functionalized following different approaches, which expands their range of applications. One such approach is surface-initiated polymerization, which involves the attachment of an initiator to the CNC’s surface to initiate the growth of the polymer. This work reports the modification of CNCs using the described approach. First, a CNC-based film was prepared, on which an initiator (RAFT agent) was grafted, and then (trimethylaminoethyl methacrylate, a positively charged monomer, was polymerized using reversible addition–fragmentation chain-transfer (RAFT) polymerization. The CNC film was successfully modified and fully characterized. Different degrees of polymerization were targeted to emphasize the effect of the positively charged polymer and their chain length on the adsorption efficiency. The results showed that by increasing the chain length of the grafted polymer, up to 80% of both pollutants could be removed, with a faster adsorption of PFOS as compared to PFOA. Full article

In this study, chitosan-based surfactants were synthesized by epoxy–amine chemistry to stabilize concentrated O/W emulsions at pH7. Chitosan was first depolymerized by nitrous deamination to obtain chitooligosaccharides (COS) with degrees of polymerization of 10 (DP10) and 20 (DP20). Then, three different epoxidized fatty chains, i.e., octyl/decyl glycidyl ether (C9), hexadecyl glycidyl ether (C16) and epoxidized cardanol (card), were grafted onto the amine groups of chitosan to form six amphiphilic structures. NMR measurements revealed grafting efficiencies ranging from 1 to 30% while HLB values ranged from 13 to 20. The relationships between these surfactant structures and their adsorption properties were investigated by tensiometric measurements, highlighting the need for a short hydrophilic moiety and high grafting efficiency to obtain the best adsorption. Subsequently, concentrated O/W emulsions (66% of oil) at pH7 were produced using COS-based surfactants and the impact of stirring time and speed during the emulsification process was described through rheological, droplet size and microscopy measurements. Finally, emulsions were stored over 2 months in order to study the destabilization phenomenon into the mixture, i.e., coalescence and creaming, by using laser granulometry and Turbiscan. Results demonstrated that stability could be enhanced by increasing emulsion viscosity, reducing droplet size or optimizing the adsorption layer at the O/W interfaces. Full article