Nanofibrils vs nanocrystals bio-nanocomposites based on sodium alginate matrix: An improved-performance study

Using celluloses to reinforce the optimized alginate film in wet state: Effect of cellulose types and cooking treatment

Alginate (Alg) as co-extruded casing is of interest to the meat industry as replacers for natural sausage casing. However, these studies on the mechanical reinforcement of Alg-based film are still limited in the wet state (e.g. co-extrusion process). In this work, Alg-D with the highest viscosity-average molecular weight (1.12 × 105) was selected from four types of alginates based on the results of the viscosity of Alg solutions and film strength. Next, three celluloses (cellulose nanocrystals (CNC), cellulose nanofibers (CNF) and microfibrillated fiber (MFC)) were added to the Alg-D matrix at different concentrations. SEM showed that the cross section of the Alg-based films became more compact and uniform when the size of celluloses decreased. The tensile test revealed that the strength (TS) of Alg-based films exhibited an initial increase followed by a subsequent drop as the cellulose content rose. The best mechanical strengthening effect was the Alg-CNC film (1.16 MPa), which increased by 93.33 % compared with that of pure Alg. Cooking treatment could further enhance this trend. The opacity increased gradually with the increase of cellulose content, while these films were still transparent enough for food packaging. These findings would have potential applications in food packaging, especially co-extruded sausage casings.

Nanocellulose extraction from acai bagasse through mixed acid hydrolysis and oxidative techniques

Exploring new biomass sources for nanocellulose (NC) extraction is crucial in elevating the economic value of readily available renewable resources. This study compares NC extracted from acai (Euterpe oleracea) bagasse using different methods: mixed acid hydrolysis, 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) mediation, and ammonium persulfate (APS) oxidations. A comprehensive analysis investigates the impact of each treatment on the physical-chemical properties of the nanoparticles, including chemical structure, crystallinity, morphology, and thermal and suspension stability. NCs obtained through mixed acid hydrolysis exhibit the highest crystallinity (62 %) and low sulfate groups on their surfaces. Consequently, they demonstrate excellent thermal stability but poor colloidal stability in water. Oxidized NCs undergo chemical modification, converting alcoholic groups into carboxyl, resulting in NCs with zeta potentials ranging between -25.30 ± 0.81 and - 27.49 ± 1.07 mV. APS oxidation produces nanoparticles with superior thermal stability compared to TEMPO oxidation. Atomic Force Microscopy (AFM) images reveal that all nanocelluloses share characteristics of nanofibers (CNFs). This comprehensive characterization highlights the potential of acai bagasse for yielding high-added-value bioproducts suitable for versatile applications.

Properties of sodium alginate-based nanocomposite films: Effects of aspect ratio and surface charge of cellulose nanocrystals

Three cellulose nanocrystals (CNCs) were prepared to reinforce sodium alginate (SA) films. This study investigated effects of aspect ratio (L/D) and surface charge of three CNCs (CCNC, MCNC, and WCNC) on the properties of films. At CNC concentrations ≤3 wt%, MCNC, with a medium L/D but the lowest surface charge density among the three CNCs, exhibited the highest efficiency in enhancing the Young's modulus and tensile strength of films. This indicated that, apart from L/D, CNC's surface charge density also affected its reinforcing effects in anionic SA-based films. Compared with other CNCs, MCNC with the lowest charge density exhibited weaker repulsion with SA, potentially contributing to stronger interfacial interactions between them. At concentrations >3 wt%, the reinforcing efficiency of MCNC was extremely close to that of WCNC, which had the highest L/D but medium charge density. This was possibly because, according to SEM results, MCNC with the lowest absolute value of zeta potential aggregated more severely than other CNCs. However, both MCNC and WCNC were consistently more efficient than CCNC. Moreover, FTIR results revealed that WCNC formed more hydrogen bonds with SA than other CNCs. Consequently, adding WCNC was more effective in reducing films' water vapor permeability and hydrophilicity.

Photocatalytic and Photothermal Antimicrobial Mussel-Inspired Nanocomposites for Biomedical Applications

Bacterial infection has traditionally been treated with antibiotics, but their overuse is leading to the development of antibiotic resistance. This may be mitigated by alternative approaches to prevent or treat bacterial infections without utilization of antibiotics. Among the alternatives is the use of photo-responsive antimicrobial nanoparticles and/or nanocomposites, which present unique properties activated by light. In this study, we explored the combined use of titanium oxide and polydopamine to create nanoparticles with photocatalytic and photothermal antibacterial properties triggered by visible or near-infrared light. Furthermore, as a proof-of-concept, these photo-responsive nanoparticles were combined with mussel-inspired catechol-modified hyaluronic acid hydrogels to form novel light-driven antibacterial nanocomposites. The materials were challenged with models of Gram-negative and Gram-positive bacteria. For visible light, the average percentage killed (PK) was 94.6 for E. coli and 92.3 for S. aureus. For near-infrared light, PK for E. coli reported 52.8 and 99.2 for S. aureus. These results confirm the exciting potential of these nanocomposites to prevent the development of antibiotic resistance and also to open the door for further studies to optimize their composition in order to increase their bactericidal efficacy for biomedical applications.

Preparation and functional characterization of the bio-composite film based on chitosan/polyvinyl alcohol blended with bacterial exopolysaccharide EPS MC-5 having antioxidant activities

In this study, the plate casting method was successfully used to prepare biocomposite films containing EPS from probiotic Enterococcus faecium MC-5 in combination with PVA and chitosan. The findings demonstrated that EPS was uniformly distributed in the film matrices and significantly improved the physicochemical properties of the resulting composite films. The development of intermolecular connections between the polymers was detected by high tensile strength and low water vapour transmission rate. EPS plays an important role in limiting the passage of UV- and visible light radiations through the films. FT-IR analysis was used to determine the molecular compatibility between the functional groups of the blended films made up of chitosan-EPS and PVA-EPS. The TGA results showed that composite films have a significant degree of thermal stability. The presence of amorphous peaks in the composite film was confirmed by XRD analysis. The EPS blended films displayed a greater antioxidant property than the PVA and chitosan films, as determined by DPPH and hydroxyl radical scavenging activities. Interestingly, the EPS-derived films showed enhanced metal chelation activity and strong antibacterial properties against Listeria monocytogenes and Staphylococcus aureus. EPS-based composite films performed better than chitosan and PVA films in terms of degradation rate. The overall functional characteristics of the EPS blended films suggested that they could be used as a packaging material to replace or reduce the use of conventional petroleum-based packaging materials.

Preparation and Evaluation of Undaria pinnatifida Nanocellulose in Fabricating Pickering Emulsions for Protection of Astaxanthin

Pickering emulsions stabilized from natural sources are often used to load unstable bio-active ingredients, such as astaxanthin (AXT), to improve their functionality. In this study, AXT-loaded Pickering emulsions were successfully prepared by 2,2,6,6-tetramethy-1-piperidine oxide (TEMPO)-oxidized cellulose nanofibers (TOCNFs) from Undaria pinnatifida. The morphology analysis showed that TOCNFs had a high aspect ratio and dispersibility, which could effectively prevent the aggregation of oil droplets. The stable emulsion was obtained after exploring the influence of different factors (ultrasonic intensity, TOCNFs concentration, pH, and ionic strength). As expected, AXT-loaded Pickering emulsions showed good stability at 50 °C and 14 days of storage. The results of simulated in vitro digestion showed that the emulsions exhibited higher release of free fatty acids (FFAs) and bioaccessibility of AXT than those in sunflower oil. Hence, our work brought new insights into the preparation of Pickering emulsions and their applications in protection and sustained, controlled release of AXT.

Critical comparison of the properties of cellulose nanofibers produced from softwood and hardwood through enzymatic, chemical and mechanical processes

Current knowledge on the properties of different types of cellulose nanofibers (CNFs) is fragmented. Properties variation is very extensive, depending on raw materials, effectiveness of the treatments to extract the cellulose fraction from the lignocellulosic biomass, pretreatments to facilitate cellulose fibrillation and final mechanical process to separate the microfibrils. Literature offers multiple parameters to characterize the CNFs prepared by different routes. However, there is a lack of an extensive guide to compare the CNFs. In this study, we perform a critical comparison of rheological, compositional, and morphological features of CNFs, produced from the most representative types of woody plants, hardwood and softwood, using different types and intensities of pretreatments, including enzymatic, chemical and mechanical ones, and varying the severity of mechanical treatment focusing on the relationship between macroscopic and microscopic parameters. This structured information will be exceedingly useful to select the most appropriate CNF for a certain application based on the most relevant parameters in each case.

Cellulose nanocrystals-based materials as hemostatic agents for wound dressings: a review

Wound dressings are devices used to stop bleeding and provide appropriate environmental conditions to accelerate wound healing. The effectiveness of wound dressing materials can be crucial to prevent deaths from excessive bleeding in surgeries and promote complete restoration of the injury. Some requirements for an ideal wound dressing are rapid hemostatic effect, high swelling capacity, antibacterial properties, biocompatibility, biodegradability, and mechanical strength. However, finding all these properties in a single material remains a challenge. In this context, nanocomposites have demonstrated an excellent capacity for this application because of their multifunctionality. One of the emerging materials used in nanocomposite manufacture is cellulose nanocrystals (CNCs), which are rod-like crystalline nanometric structures present on cellulose chains. These nanoparticles are attractive for wound healing applications because of their high aspect ratio, high mechanical properties, functionality and low density. Hence, this work aimed to present an overview of nanocomposites constituted by CNCs for wound healing applications. The review focuses on the most common materials used as matrices, the types of dressing, and their fabrication techniques. Novel wound dressings composites have improved hemostatic, swelling, and mechanical properties compared to other pure biopolymers while preserving their other biological properties. Films, nanofibers mats, sponges, and hydrogels have been prepared with CNCs nanocomposites, and in vitro and in vivo tests have proved their suitability for wound healing.

Development of novel collagen hydrolysate bio-nanocomposite films extracted from hide trimming wastes reinforced with chitosan nanoparticles

The wide availability of pollutant by-products from the leather industries has been a key factor in driving the research into converting these low-cost by-products into high value-added collagen-based products. In this study, collagen hydrolysate (CH) was extracted from hide trimming waste from the tanneries and used to prepare biodegradable films with chitosan nanoparticles (CNPs) with different concentrations to develop an alternative product to non-biodegradable plastics. The effects of CNPs concentration on the thickness, mechanical, water barrier, thermal, light transmittance, color properties, and opacity of CH-based films were investigated. The results clearly show that the tensile strength and elastic modulus values of CH/CNPs films increase significantly as the concentration of CNPs increases, while the elongation at break, water solubility, and water vapor permeability values decrease. In addition, scanning electron microscopy (SEM) showed uniform distributions of CNPs in the CH-based films. Based on the results obtained, the extraction of CH from hide trimming wastes and reuse in the production of biodegradable films will both prevent these valuable wastes from being dispose into the landfills and will be an alternative to fossil-derived plastics in the future.

Cellulose nanofibrils (CNFs) produced by different mechanical methods to improve mechanical properties of recycled paper

In current study, CNFs produced by different mechanical methods, were used to improve the mechanical properties of recycled paper. The result showed the morphology of CNFs had great impact on reinforced effect and the length of fibrils determined their contribution in recycled paper strength. For different CNFs with similar diameter, the higher aspect ratio resulted in better reinforced effect. The CNFs produced by microfluidic homogenization and suitable PFI milling conditions (RM-CNF1) got best reinforced effect which improved tensile index and burst index by 35.5 % and 49.4 % at 5.0 wt% addition, respectively, due to their high aspect ratio. Although the CNFs produced by ball milling and ultrasonication (BU-CNF2) still had many bundles that were not fibrillated completely, their reinforced effect just below RM-CNF1 due to their special morphology and high retention rate. This work aims to study the influence of CNFs on recycled fibers reinforcement.