Recent Advances in Cellulose-Based Hydrogels Prepared by Ionic Liquid-Based Processes.

This review summarizes the recent advances in preparing cellulose hydrogels via ionic liquid-based processes and the applications of regenerated cellulose hydrogels/iongels in electrochemical materials, separation membranes, and 3D printing bioinks. Cellulose is the most abundant natural polymer, which has attracted great attention due to the demand for eco-friendly and sustainable materials. The sustainability of cellulose products also depends on the selection of the dissolution solvent. The current state of knowledge in cellulose preparation, performed by directly dissolving in ionic liquids and then regenerating in antisolvents, as described in this review, provides innovative ideas from the new findings presented in recent research papers and with the perspective of the current challenges.

Correction: Taokaew, S.; Kriangkrai, W. Chitinase-Assisted Bioconversion of Chitinous Waste for Development of Value-Added Chito-Oligosaccharides Products. Biology 2023, 12, 87.

In the original publication [...].

Recent Development of Functional Chitosan-Based Hydrogels for Pharmaceutical and Biomedical Applications.

Chitosan is a promising naturally derived polysaccharide to be used in hydrogel forms for pharmaceutical and biomedical applications. The multifunctional chitosan-based hydrogels have attractive properties such as the ability to encapsulate, carry, and release the drug, biocompatibility, biodegradability, and non-immunogenicity. In this review, the advanced functions of the chitosan-based hydrogels are summarized, with emphasis on fabrications and resultant properties reported in literature from the recent decade. The recent progress in the applications of drug delivery, tissue engineering, disease treatments, and biosensors are reviewed. Current challenges and future development direction of the chitosan-based hydrogels for pharmaceutical and biomedical applications are prospected.

Multifunctional Cellulosic Natural Rubber and Silver Nanoparticle Films with Superior Chemical Resistance and Antibacterial Properties.

Composite films of natural rubber/cellulose fiber/silver nanoparticle were synthesized in a green route via the latex solution process. Hybrid cellulose filler containing carboxymethyl cellulose and cellulose microfibers was used to facilitate facile and fast preparation and to improve mechanical strength to the composites, respectively. All the composites possessed a high tensile strength of ~120 MPa, a high heat resistance of nearly 300 °C, and more than 20% biodegradability in soil in two weeks. Chemical resistance and antibacterial activity of the composite was enhanced depending on sizes and concentrations of silver nanoparticles (AgNPs). The composites containing 0.033-0.1% w/w AgNPs retarded toluene uptake to less than 12% throughout 8 h, whereas the composite containing 0.067-0.1% w/w AgNPs exhibited excellent antibacterial activities against Escherichia coli and Staphylococcus aureus. In comparison, 50 nm-AgNPs presented higher antibacterial activities than 100 nm-AgNPs. In vitro cytotoxicity test assessed after incubation for 24 h and 48 h revealed that almost all AgNPs-composite films exhibited non/weak and moderate cytotoxicity, respectively, to HaCaT keratinocyte cells.

Chitinase-Assisted Bioconversion of Chitinous Waste for Development of Value-Added Chito-Oligosaccharides Products.

Chito-oligosaccharides (COSs) are the partially hydrolyzed products of chitin, which is abundant in the shells of crustaceans, the cuticles of insects, and the cell walls of fungi. These oligosaccharides have received immense interest in the last few decades due to their highly promising bioactivities, such as their anti-microbial, anti-tumor, and anti-inflammatory properties. Regarding environmental concerns, COSs are obtained by enzymatic hydrolysis by chitinase under milder conditions compared to the typical chemical degradation. This review provides updated information about research on new chitinase derived from various sources, including bacteria, fungi, plants, and animals, employed for the efficient production of COSs. The route to industrialization of these chitinases and COS products is also described.

Enhanced production of fibrous bacterial cellulose in Gluconacetobacter xylinus culture medium containing modified protein of okara waste.

In Gluconacetobacter xylinus cultivation for bacterial nanocellulose production, agro-industrial wastes, soybean residual okara, okara extracted protein, and modified okara protein, were used as a protein source. In comparison with homogenized raw okara and protein extracted from raw okara, acetic-acid modified protein provided the higher cellulose yield (2.8 g/l at 3 %w/v protein concentration) due to the improved protein solubility in the culture medium (89 %) and smaller particle size (0.2 µm) leading to facile uptake by the bacteria. Importantly, pH of the culture medium containing the modified protein measured before and after the cultivation was similar, suggesting the buffering capacity of the protein. Nanocellulose fibers were then produced densely in the network of hydrogels with high crystallinity nearly 90 %. Based on the results, economic constraints around nanocellulose production could be alleviated by valorization of okara waste, which provided enhanced sustainability.

Alginate as Dispersing Agent for Compounding Natural Rubber with High Loading Microfibrillated Cellulose.

Natural rubber (NR) reinforced with high loading of microfibrillated cellulose (MFC) was fabricated in the presence of sodium alginate as a thickening and dispersing agent in NR latex. The tensile strength and Young's moduli of the 50% wt. MFC loading-NR composites were 13.6 and 1085.7 MPa, which were about 11.3- and 329-times enhanced compared with those of the neat NR film. The maximum elongation at 313.3% was obtained from 30% MFC loading, which was a 3.3-fold increase of that of the NR film. The thermal stability of MFC-NR films was slightly reduced, while the glass transition temperature remained unchanged at -64 °C. The MFC-NR films exhibited high water adsorption ability, toluene resistance, and biodegradability.

Multifunctional cellulosic nanofiber film with enhanced antimicrobial and anticancer properties by incorporation of ethanolic extract of Garcinia mangostana peel.

Natural polymeric nanofibers-based materials for medical application is an intensive research area due to the unique features of natural polymeric nanofibers. Bacterial nanocellulose (BC) films containing various concentrations of mangosteen (Garcinia mangostana) peel extract were prepared and evaluated as a multifunctional nanofiber film. The extract was absorbed into BC hydrogel and air dried to entrap the extract into nanofiber network. The resulting films contained about 3, 35, and 294 mg of total phenolic compounds and 2, 24, and 250 mg of α-mangostin per cm3 of the dried films. The film containing the highest phenolic compounds and α-mangostin performed the inhibitory effect to Staphylococcus epidermidis, Propionibacterium acnes, and Staphylococcus aureus. High anticancer activity against B16F10 melanoma and MCF-7 breast cancer cells having viabilities of 10 and 5%, respectively after 48 h were detected after the treatments with the film. However, the film had a low toxicity against normal fibroblast and keratinocyte cells with 41 and 99% viability, respectively. The research suggested that the prepared films were a multifunctional nanofiber films with antimicrobial and anticancer properties.

Size Distribution and Characteristics of Chitin Microgels Prepared via Emulsified Reverse-Micelles.

Chitin was extracted from local snow crab shell waste and used as a raw material in the fabrication of porous spherical microgels. The chitin microgels were obtained using a batch process of emulsification and, afterward, gelation. The effects of chitin concentrations, oil and water phase ratios (O:W), surfactants, and gelation on the size distribution and morphology of the microgels were investigated. The extracted chitin possessed α-chitin with a degree of acetylation of ~60% and crystallinity of 70%, as confirmed by Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Powder Diffraction (XRD). In the reverse-micellar emulsification, different chitin concentrations in NaOH solution were used as aqueous phases, and n-hexane media containing Span 80-based surfactants were used as dispersion phases. Various HCl solutions were used as gelling agents. Microgels with sizes ranging from ~5-200 µm were obtained relying on these studied parameters. Under the condition of 3% w/w chitin solution using O:W of 15:1 at 5% w/w of Span 80 (hydrophilic-lipophilic balance; HLB of 4.3), the gelation in the emulsified reverse micelles was better controlled and capable of forming spherical microgel particles with a size of 7.1 ± 0.3 µm, when 800 µL of 1 M HCl was added. The prepared chitin microgel exhibited macro-pore morphology and swelling behavior sensitive to the acidic pH.

Modification of Bacterial Cellulose with Organosilanes to Improve Attachment and Spreading of Human Fibroblasts.

Bacterial Cellulose (BC) synthesized by Acetobacter xylinum has been a promising candidate for medical applications. Modifying BC to possess the properties needed for specific applications has been reported. In this study, BCs functionalized by organosilanes were hypothesized to improve the attachment and spreading of Normal Human Dermal Fibroblast (NHDF). The BC gels obtained from biosynthesis were dried by either ambient-air drying or freeze drying. The surfaces of those dried BCs were chemically modified by grafting methyl terminated octadecyltrichlorosilane (OTS) or amine terminated 3-aminopropyltriethoxysilane (APTES) to expectedly increase hydrophobic or electrostatic interactions with NHDF cells, respectively. NHDF cells improved their attachment and spreading on the majority of APTES-modified BCs (∼70-80% of area coverage by cells) with more rapid growth (∼2.6-2.8× after incubations from 24 to 48h) than on tissue culture polystyrene (∼2×); while the inverse results (< 5% of area coverage and stationary growth) were observed on the OTS-modified BCs. For organosilane modified BCs, the drying method had no effect on in vitro cell attachment/spreading behaviors.

Characteristics and anticancer properties of bacterial cellulose films containing ethanolic extract of mangosteen peel.

Bacterial cellulose (BC) films containing an ethanolic extract of mangosteen peel were prepared and their physical, chemical, and anticancer properties were characterized. The cumulative absorption and release profiles of bioactive compounds in the films were determined based on total phenolic and α-mangostin content. The BC films were filled with total phenolic compounds expressed as gallic acid equivalent varying from 4.72 to 275.91 mg/cm3 dried film, and α-mangostin varying from 2.06 to 248.20 mg/cm3 dried film. A Fourier transform infrared spectroscopy evaluation showed that there were weak interactions between the functional groups of the extract and the BC. Decreases in the water absorption capacity and water vapor transmission rate of the modified films were detected. Release studies were performed using Franz diffusion cells. In a non-transdermal system, the release of bioactive compounds from the films depended on concentration, immersion time, and the pH of the dissolution medium. A transdermal diffusion study showed that 59-62% of total phenolic compounds that were initially loaded were released from the films and more than 95% of bioactive compounds released from the films were adsorbed into pig skin. Only very small amount of the bioactive compounds penetrated through pig skin and into phosphate and acetate buffers. In studies of anticancer abilities, the release of 2.0 µg/ml α-mangostin from the BC films could suppress the growth of B16F10 melanoma (approximately 31% survival). With the release of α-mangostin at greater than 17.4-18.4 µg/ml, less than 15 and 5% survival of B16F10 melanoma and MCF-7 breast cancer cells, respectively, was observed.

In vitro behaviors of rat mesenchymal stem cells on bacterial celluloses with different moduli.

Compressive moduli of bacteria-synthesized cellulose (BC) were altered by two drying techniques: ambient-air drying and freeze drying. While no significant differences in dry weight were found, their cross-sectional structures and thickness varied greatly. Freeze dried BCs had loose cross-sectional structures and a thickness of ~4.7 mm, whereas air dried BCs had more compacted cross-sectional structures and a thickness of ~0.1mm. The compressive moduli of the rehydrated freeze dried and rehydrated air dried BCs were measured to be 21.06±0.22 kPa and 90.09±21.07 kPa, respectively. When rat mesenchymal stem cells (rMSCs) were seeded on these BCs, they maintained a round morphology in the first 3 days of cultivation. More spread-out morphology and considerable proliferation on freeze dried BCs were observed in 7 days, but not on air-dried BCs. The cells were further grown for 3 weeks in the absence and presence of differentiation agents. Without using any differentiation agents, no detectable differentiation was noticed for rMSCs further cultivated on both types of BC. With differentiation inducing agents, chondrogenic differentiation, visualized by histological staining, was observed in some area of the rehydrated freeze dried BCs; while osteogenic differentiation was noticed on the stiffer rehydrated air dried BCs.

Biosynthesis and Characterization of Nanocellulose-Gelatin Films.

A nanocellulose-gelatin (bacterial cellulose gelatin (BCG)) film was developed by a supplement of gelatin, at a concentration of 1%-10% w/v, in a coconut-water medium under the static cultivation of Acetobacter xylinum. The two polymers exhibited a certain degree of miscibility. The BCG film displayed dense and uniform homogeneous structures. The Fourier transform infrared spectroscopy (FTIR) results demonstrated interactions between the cellulose and gelatin. Incorporation of gelatin into a cellulose nanofiber network resulted in significantly improved optical transparency and water absorption capacity of the films. A significant drop in the mechanical strengths and a decrease in the porosity of the film were observed when the supplement of gelatin was more than 3% (w/v). The BCG films showed no cytotoxicity against Vero cells.