Chitin and chitosan nanofibers: electrospinning of chitin and deacetylation of chitin nanofibers

Chitosan coatings with modulated surface roughness for the inhibition of marine macrofouling

Surface roughness is known to influence biofouling in marine environments. Different from the conventional antifouling coatings based on hydrophobic polymeric materials such as epoxy and polydimethylsiloxane (PDMS), in this study, naturally occurring compound benzophenone-3 (BP-3) modified chitosan (CS) biopolymer coatings with varied surface roughness were prepared and studied for their antifouling effect for the first time. By regulating the competitive reactions between the reactants, different condensation products can be obtained which result in varied root mean square (RMS) roughness of CS-BP-3 coatings from 7.6 nm to 270.0 nm. It is found that the reaction time influences more than the reaction temperature while defining the surface roughness of CS-BP-3 coatings. Specifically, the coatings of CS-BP-3 prepared from a 2-h reaction led to RMS roughness between 7.6 and 55.18 nm, whereas after 12-h reaction roughness between 82.6 and 270.0 nm were measured. Subsequent antifouling experiments indicate that rougher coatings have a more pronounced effect of preventing the settlement of plantigrade mollusk mimicking the lotus effect. This work demonstrates that bio-inspired materials can be designed to achieve desired functions for practical applications.

Chitin nanofibers: recent advances in preparation and applications in biomedical and beyond

Chitin and chitosan-based nanofibers (ChNFs), derived from renewable sources, have emerged as promising biomaterials due to their unique properties such as high surface area, porosity, biocompatibility, and biodegradability. This review provides a comprehensive overview of ChNF extraction and synthesis, focusing on both top-down and bottom-up approaches. A comparative analysis of these methods is presented, highlighting the challenges, opportunities, environmental impact, cost-effectiveness, and quality consistency associated with each. The advantages of ChNFs over similar nanomaterials are elucidated, emphasizing their diverse applications in biomedical and environmental fields. Biomedical applications include drug delivery, tissue engineering, cancer treatment, wound healing, and biosensing. Environmental applications encompass water treatment, air filtration, agriculture, and biodegradable packaging. Despite their potential, challenges remain, including low solubility, unstable mechanical properties, and inconsistent quality, which limit their widespread use. This review also examines recent advancements in ChNF research, aiming to guide the development of efficient and environmentally friendly synthesis methods. By encouraging innovation in ChNF-based nanotechnologies, this research contributes to a more sustainable future.

Eumelanin-Enhanced Photothermal Disinfection of Contact Lenses Using a Sustainable Marine Nanoplatform Engineered with Electrospun Nanofibers

Bacterial keratitis (BK) is a severe eye infection commonly associated with Staphylococcus aureus (S. aureus), posing a significant risk to vision, especially among contact lens wearers. This research introduces a novel smart nanoplatform (deMS@cNF), developed from demineralized mussel shells (deMS) and reinforced with chitin (CT) nanofibrils, specifically designed for portable photothermal disinfection of contact lenses. The nanoplatform leverages the photothermal properties of eumelanin in mussel shells (MS), which, when activated by a simple bike flashlight, rapidly heats to temperatures up to 95 °C, effectively destroying bacterial contamination. In vitro tests demonstrate that the nanoplatform is biocompatible and non-toxic, making it suitable for medical applications. This study highlights an innovative approach to converting marine biowaste into a safe, effective, and low-cost portable method for disinfecting contact lenses, showcasing the potential of the deMS@cNF platform for broader antimicrobial applications.

A review on chitin dissolution as preparation for electrospinning application

Electrospinning has been acknowledged as an efficient technique for the fabrication of continuous nanofibers from polymeric based materials such as polyvinyl alcohol (PVA), cellulose acetate (CA), chitin nanocrystals and others. These nanofibers exhibit chemical and mechanical stability, high porosity, functionality, high surface area and one-dimensional orientation which make it extremely beneficial in industrial application. In recent years, research on chitin - a biopolymer derived from crustacean and fungal cell wall - had gained interest due to its unique structural arrangement, excellent physical and chemical properties, in which make it biodegradable, non-toxic and biocompatible. Chitin has been widely utilized in various applications such as wound dressings, drug delivery, tissue engineering, membranes, food packaging and others. However, chitin is insoluble in most solvents due to its highly crystalline structure. An appropriate solvent system is required for dissolving chitin to maximize its application and produce a fine and smooth electrospun nanofiber. This review focuses on the preparation of chitin polymer solution through dissolution process using different types of solvent system for electrospinning process. The effect of processing parameters also discussed by highlighting some representative examples. Finally, the perspectives are presented regarding the current application of electrospun chitin nanofibers in selected fields.

Nanochitin for sustainable and advanced manufacturing

Presently, the rapid depletion of resources and drastic climate change highlight the importance of sustainable development. In this case, nanochitin derived from chitin, the second most abundant renewable polymer in the world, possesses numerous advantages, including toughness, easy processability and biodegradability. Furthermore, it exhibits better dispersibility in various solvents and higher reactivity than chitin owing to its increased surface area to volume ratio. Additionally, it is the only natural polysaccharide that contains nitrogen. Therefore, it is valuable to further develop this innovative technology. This review summarizes the recent developments in nanochitin and specifically identifies sustainable strategies for its preparation. Additionally, the different biomass sources that can be exploited for the extraction of nanochitin are highlighted. More importantly, the life cycle assessment of nanochitin preparation is discussed, followed by its applications in advanced manufacturing and perspectives on the valorization of chitin waste.

Hydrogels based on seafood chitin: From extraction to the development

Chitin is extensively applied in vast applications due to its excellent biological properties, such as biodegradable and non-toxic. About 50 % of waste generated during seafood processing is chitin. Conventionally, chitin is extracted via chemical method. However, it has many shortcomings. Many novel extraction methods have emerged, including enzymatic hydrolysis, microbial fermentation, ultrasonic or microwave-assisted, ionic liquids, and deep eutectic solvents. Chitin and its derivatives-based hydrogels have attracted much attention due to their excellent properties. Nevertheless, they all have many limitations. Therefore, the preparation and application of chitin and its derivatives-based hydrogels are still facing great challenges. This review focuses on the challenges and prospects for sustainable chitin extraction from seafood waste and the preparation and application of chitin and its derivatives-based hydrogels. First section summarizes the mechanism and application of several methods of extracting chitin. The different extraction methods were evaluated from the aspects of yield, degree of acetylation, and protein and mineral residuals. The shortcomings of the extraction methods are also discussed. Next section summarizes the preparation and application of chitin and its derivatives-based hydrogels. Overall, we hope this mini-review can provide a practical reference for selecting chitin extraction methods from seafood and applying chitin and its derivatives-based hydrogels.

Fabrication of affinity-based drug delivery systems based on electrospun chitosan sulfate/poly(vinyl alcohol) nanofibrous mats

Benign electrospinning of chitosan in aqueous medium is an open challenge mainly due to its insolubility in neutral pH and inter- and intramolecular hydrogen bonding interactions. Here, we developed a simple and widely-used methodology to improve the chitosan electrospinnability through the sulfation of chitosan and its further mixing with poly(vinyl alcohol) for the first time. The FTIR, 1H NMR and elemental analyses showed the successful sulfation of chitosan. Furthermore, the viscosity and electrical conductivity measurements revealed the high solubility of chitosan sulfate (CS) in aqueous media. In the next step, a uniform electrospun nanofibrous mat of CS/PVA was fabricated with a fiber diameter ranging from 90 to 340 nm. The crosslinked CS/PVA (50/50) nanofibrous mat as the optimum sample showed a swelling ratio of 290 ± 4 % and a high Young's modulus of 3.75 ± 0.10 GPa. Finally, malachite green (MG) as a cationic drug model was loaded into different samples of chitosan film, CS film, and CS/PVA (50/50) nanofibrous mat and its release behavior was studied. The results of these analyses revealed that the CS/PVA (50/50) nanofibrous mat can successfully load higher contents of the MG and also release it in a sustained manner.

Biowaste-derived Ni/NiO decorated-2D biochar for adsorption of methyl orange

Eco-friendly carbothermal techniques were used to synthesize nanocomposites of biowaste-derived Ni/NiO decorated-2D biochar. The use of chitosan and NiCl2 in the carbothermal reduction technique was a novelty to synthesize the Ni/NiO decorated-2D biochar composite. Potassium persulfate (PS) was found to be activated by Ni/NiO decorated-2D biochar, which is thought to oxidize organic pollutants through an electron pathway designed by the reactive complexes formed between PS and the Ni/NiO biochar surface. This activation led to the efficient oxidation of methyl orange and organic pollutants. Analyzing Ni/NiO decorated-2D biochar composite before and after the methyl orange adsorption and degradation procedure allowed us to report on the process of its elimination. The Ni/NiO biochar with PS activation showed higher efficiency than Ni/NiO decorated-2D biochar composite as this material was able to degrade over 99% of the methyl orange dye. The effects of initial methyl orange concentration, dosages effect, solution pH, equilibrium studies, kinetics, thermodynamic studies, and reusability were examined and evaluated on Ni/NiO biochar.

Nano-chitin reinforced agarose hydrogels: Effects of nano-chitin addition and acidic gas-phase coagulation

Hydrogels based on natural polymers such as agarose usually show low applicability due to their weak mechanical properties. In this work, we developed a dual cross-linked agarose hydrogel by adding different amounts of TEMPO-oxidized nano-chitin (0-0.2 %) to agarose hydrogel matrices and then physically cross-linked under acidic gas-phase coagulation. The prepared hydrogels were characterized by FTIR, XRD, TGA, and SEM. The effects of nano-chitin addition and acidic gas-phase coagulation on the properties of agarose hydrogels, such as gel strength, swelling degree, rheological properties, and methylene blue (MB) adsorption capacity, were also studied. Structural characterizations confirmed that nano-chitin was successfully introduced into agarose hydrogels. The gel strength, storage modulus, and MB adsorption capacity of agarose hydrogels gradually increased with the increasing nano-chitin addition, whereas the swelling degree decreased. After acidic gas-phase coagulation, agarose/nano-chitin nanocomposite hydrogels exhibited improved gel strength and storage modulus, while the swelling degree and MB adsorption capacity were slightly reduced. The combination of oxidized nano-chitin and acidic gas-phase coagulation is expected to be an effective way to improve the properties of natural polymer hydrogels.

Chitin/deacetylated chitin nanocomposite film for effective adsorption of organic pollutant from aqueous solution

Cross-linked chitin/deacetylated chitin nanocomposite films can be considered as a potential industrial adsorbent for the removal of organic pollutants for water purification. Chitin (C) and deacetylated chitin (dC) nanofibers were extracted from raw chitin and characterized using FTIR, XRD and TGA techniques. The TEM image confirmed the formation of chitin nanofibers with a diameter range of 10-45 nm. The deacetylated chitin nanofibers (DDA-46 %) having 30 nm diameter was evidenced using FESEM. Further, the C/dC nanofibers were prepared at different ratios (80/20, 70/30, 60/40 & 50/50 ratios) and cross-linked. The highest tensile strength of 40 MPa and Young's modulus of 3872 MPa was exhibited by 50/50C/dC. The DMA studies revealed that the storage modulus enhanced by 86 % for 50/50C/dC (9.06 GPa) in comparison to 80/20C/dC nanocomposite. Further, the 50/50C/dC exhibited a maximum adsorption capacity of 30.8 mg/g at pH = 4 in 30 mg/L of Methyl Orange (MO) dye within 120 min. The experimental data agreed with pseudo-second-order model indicating chemisorption process. The adsorption isotherm data was best described by Freundlich model. The nanocomposite film is an effective adsorbent can be regenerated and recycled for five adsorption-desorption cycle.

Nano-chitin: Preparation strategies and food biopolymer film reinforcement and applications

Current trends in food packaging systems are toward biodegradable polymer materials, especially the food biopolymer films made from polysaccharides and proteins, but they are limited by mechanical strength and barrier properties. Nano-chitin has great economic value as a highly efficient functional and reinforcing material. The combination of nano-chitin and food biopolymers offers good opportunities to prepare biodegradable packaging films with enhanced physicochemical and functional properties. This review aims to give the latest advances in nano-chitin preparation strategies and its uses in food biopolymer film reinforcement and applications. The first part systematically introduces various preparation methods for nano-chitin, including chitin nanofibers (ChNFs) and chitin nanocrystals (ChNCs). The nano-chitin reinforced biodegradable films based on food biopolymers, such as polysaccharides and proteins, are described in the second part. The last part provides an overview of the current applications of nano-chitin reinforced food biopolymer films in the food industry.

Biodegradable Electrospun Scaffolds as an Emerging Tool for Skin Wound Regeneration: A Comprehensive Review

Skin is designed to protect various tissues, and because it is the largest and first human bodily organ to sustain damage, it has an incredible ability to regenerate. On account of extreme injuries or extensive surface loss, the normal injury recuperating interaction might be inadequate or deficient, bringing about risky and disagreeable circumstances that request the utilization of fixed adjuvants and tissue substitutes. Due to their remarkable biocompatibility, biodegradability, and bioactive abilities, such as antibacterial, immunomodulatory, cell proliferative, and wound mending properties, biodegradable polymers, both synthetic and natural, are experiencing remarkable progress. Furthermore, the ability to convert these polymers into submicrometric filaments has further enhanced their potential (e.g., by means of electrospinning) to impersonate the stringy extracellular grid and permit neo-tissue creation, which is a basic component for delivering a mending milieu. Together with natural biomaterial, synthetic polymers are used to solve stability problems and make scaffolds that can dramatically improve wound healing. Biodegradable polymers, commonly referred to as biopolymers, are increasingly used in other industrial sectors to reduce the environmental impact of material and energy usage as they are fabricated using renewable biological sources. Electrospinning is one of the best ways to fabricate nanofibers and membranes that are very thin and one of the best ways to fabricate continuous nanomaterials with a wide range of biological, chemical, and physical properties. This review paper concludes with a summary of the electrospinning (applied electric field, needle-to-collector distance, and flow rate), solution (solvent, polymer concentration, viscosity, and solution conductivity), and environmental (humidity and temperature) factors that affect the production of nanofibers and the use of bio-based natural and synthetic electrospun scaffolds in wound healing.

Photocrosslinked Fish Collagen Peptide/Chitin Nanofiber Composite Hydrogels from Marine Resources: Preparation, Mechanical Properties, and an In Vitro Study

Fish collagen peptide (FCP) is a water-soluble polymer with easy accessibility, bioactivity, and reactivity due to its solubility. The gelation of FCP can be carried out by chemical crosslinking, but the mechanical strength of FCP hydrogel is very low because of its intrinsically low molecular weight. Therefore, the mechanical properties of FCP gel should be improved for its wider application as a biomaterial. In this study, we investigated the mechanical properties of M-FCP gel in the context of understanding the influence of chitin nanofibers (CHNFs) on FCP hydrogels. FCP with a number average molecular weight (M_n) of ca. 5000 was reacted with glycidyl methacrylate (GMA) and used for the preparation of photocrosslinked hydrogels. Subsequently, composite hydrogels of methacrylate-modified FCP (M-FCP) and CHNF were prepared by the photoirradiation of a solution of M-FCP containing dispersed CHNF at an intensity of ~60 mW/cm² for 450 s in the presence of 2-hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone (Irgacure 2959) as a photoinitiator. Compression and tensile tests of the FCP hydrogels were carried out using a universal tester. The compression and tensile strength of the hydrogel increased 10-fold and 4-fold, respectively, by the addition of 0.6% CHNF (20% M-FCP), and Young's modulus increased 2.5-fold (20% M-FCP). The highest compression strength of the M-FCP/CHNF hydrogel was ~300 kPa. Cell proliferation tests using fibroblast cells revealed that the hydrogel with CHNF showed good cell compatibility. The cells showed good adhesion on the M-FCP gel with CHNF, and the growth of fibroblast cells after 7 days was higher on the M-FCP/CHNF gel than on the M-FCP gel without CHNF. In conclusion, we found that CHNF improved the mechanical properties as well as the fibroblast cell compatibility, indicating that M-FCP hydrogels reinforced with CHNF are useful as scaffolds and wound-dressing materials.

Biodegradable Electrospun Nanofiber Membranes as Promising Candidates for the Development of Face Masks

Aerosol particles, such as the widespread COVID-19 recently, have posed a great threat to humans. Combat experience has proven that masks can protect against viruses; however, the epidemic in recent years has caused serious environmental pollution from plastic medical supplies, especially masks. Degradable filters are promising candidates to alleviate this problem. Degradable nanofiber filters, which are developed by the electrospinning technique, can achieve superior filtration performance. This review focuses on the basic introduction to air filtration, the general aspects of face masks, and nanofibers. Furthermore, the progress of the state of art degradable electrospun nanofiber filters have been summarized, such as silk fibroin (SF), polylactic acid (PLA), chitosan, cellulose, and zein. Finally, the challenges and future development are highlighted.

Masterbatch of Chitosan Nanowhiskers for Preparation of Nylon 6,10 Nanocomposite by Melt Blending

Composite materials have been extensively studied to optimize properties such as lightness and strength, which are the advantages of plastics. We prepared a highly concentrated (30 wt %) nylon/chitosan nanowhisker (CSW) masterbatch by blending nylon 6,10 and CSW by solvent casting to achieve high dispersion efficiency while considering an industrial setting. Subsequently, 0.3 wt % nylon/CSW nanocomposites were prepared with a large quantity of nylon 6,10 via melt blending. During preparation, the materials were stirred in the presence of formic acid at different times to investigate the effect of stirring time on the structure of the CSW and the physical properties of the composite. The formation of nanocomposites by the interactions between nylon and CSW was confirmed by observing the change in hydrogen bonding using FT-IR spectroscopy and the rise in melting temperature and melting enthalpy through differential scanning calorimetry. The results demonstrated increases in complex viscosity and shear thinning. The rheological properties of the composites changed due to interactions between CSW and nylon, as indicated by the loss factor. The mechanical properties produced by the nanocomposite stirred for 1.5 h were superior, suggesting that formic acid caused minimal structural damage, thus verifying the suitability of the stirring condition.

Preparation of CO2 -based Cationic Polycarbonate/Polyacrylonitrile Nanofibers with an Optimal Fibrous Microstructure for Antibacterial Applications

Utilizing CO₂ as one of the monomer resource, poly(vinylcyclohexene carbonates) (PVCHCs) are used as the precursor for preparing cationic PVCHCs (CPVCHCs) via thiol-ene click functionalization. Through the functionalization, CPVCHC-43 with a tertiary amine density of 43% relative to the backbone is able to display a significantly antibacterial ability against Staphylococcus aureus (S. aureus). Blending CPVCHC-43 with polyacrylonitrile (PAN), CPVCHC/PAN nanofiber meshes (NFMs) have been successfully prepared by electrospinning. More importantly, two crucial fibrous structural factors including CPVCHC/PAN weight ratio and fiber diameter have been systematically investigated for the effects on the antibacterial performance of the NFMs. Sequentially, a quaternization treatment has been employed on the NFMs with an optimal fibrous structure to enhance the antibacterial ability. The resulting quaternized NFMs have demonstrated the great biocidal effects against Gram-positive and Gram-negative bacteria. Moreover, the excellent biocompatibility of the quaternized NFMs have also been thoroughly evaluated and verified. This article is protected by copyright. All rights reserved.

Biomimetic generation of the strongest known biomaterial found in limpet tooth

The biomaterial with the highest known tensile strength is a unique composite of chitin and goethite (α-FeO(OH)) present in teeth from the Common Limpet (Patella vulgata). A biomimetic based on limpet tooth, with corresponding high-performance mechanical properties is highly desirable. Here we report on the replication of limpet tooth developmental processes ex vivo, where isolated limpet tissue and cells in culture generate new biomimetic structures. Transcriptomic analysis of each developmental stage of the radula, the organ from which limpet teeth originate, identifies sequential changes in expression of genes related to chitin and iron processing. We quantify iron and chitin metabolic processes in the radula and grow isolated radula cells in vitro. Bioinspired material can be developed with electrospun chitin mineralised by conditioned media from cultured radula cells. Our results inform molecular processes behind the generation of limpet tooth and establish a platform for development of a novel biomimetic with comparable properties.

The highest tensile strength biomaterial known exists in limpet teeth and replicating this material is of interest. Here, the authors report on the ex vivo growth of teeth and use of isolated limpet tissue and cells providing foundations for the development of this high-tensile biomaterial.

Red carbon dot directed biocrystalline alignment for piezoelectric energy harvesting

Herein, using chitin-derived chitosan, we first demonstrate the luminous carbon dot-directed large-scale biocrystalline piezo-phase alignment. This further significantly facilitates the piezo-energy harvesting of Earth-abundant natural biopolymers. A very small, yet moderate, number of red-emission carbon quantum dots (R-CQDs) allow a highly preferential macroscopic alignment of chitosan based, electrospun hybrid nanofibers and a highly preferential microscopic alignment of internal chitosan piezo-phase crystalline lamellae. Meanwhile, R-CQD hybridized bionanofibers maintain the long-wavelength photoluminescence excitation/emission of encapsulated, monodisperse R-CQDs. The piezoelectric voltage output and piezoelectric current output of hybrid bionanofibers reach up to 125 V cm^-3 and 1.5 μA cm^-3, respectively. They are more than 5 and 6 times higher than those of the state-of-the-art pristine ones, respectively. Moreover, the proof-of-concept red-emission bionanofibrous piezoelectric nanogenerator shows a highly durable, highly stable, and highly reproducible piezoresponse in over 10 000 continuous load cycles. As a reliable renewable energy source, it demonstrates the fast charging of external capacitors and the direct operation of commercial electronics. In particular, as a self-powered wearable tactile healthcare sensor, it attains ultrahigh mechanosensitivity in sensing a broad range of human biophysiological pressures and strains.

Hyaluronic acid and chitosan-based electrospun wound dressings: Problems and solutions

To date, available review papers related to the electrospinning of biopolymers including polysaccharides for wound healing were focused on summarizing the process conditions for two candidates, namely chitosan and hyaluronic acid. However, most reviews lack the discussion of problems of hyaluronan and chitosan electrospun nanofibers for wound dressing applications. For this reason, it is required to update information by providing a comprehensive overview of all factors which may play a role in the electrospinning of hyaluronic acid and chitosan for applications of wound dressings. This review summarizes the fabricated chitosan and hyaluronic acid electrospun nanofibers as wound dressings in the last years, including methods of preparations of nanofibers and challenges for the electrospinning of both pure chitosan and hyaluronic acid and strategies how to overcome the existing difficulties. Moreover, in this review the biological roles and mechanisms of chitosan and hyaluronic acid in the wound healing process are explained including the advantages of nanofibers for ideal wound management using the common solvents, copolymers enhancing spinning process, and the most biologically active incorporated substances thereby providing drug delivery in wound healing.

Production of Fungal Nanochitosan Using High-Pressure Water Jet System for Biomedical Applications

In this present work, fungal nanochitosans, with very interesting particle size distribution of 22 µm, were efficiently generated in high-yield production using a high-pressure water jet system (Star Burst System, Sugino, Japan) after 10 passes of mechanical treatment under high pressure. The specific characterization of fungal chitosan nanofibers suspensions in water revealed a high viscosity of 1450 mPa.s and an estimated transparency of 43.5% after 10 passes of fibrillation mechanical treatment. The mechanical characterization of fungal nanochitosan (NC) film are very interesting for medical applications with a Young’s modulus (E), a tensile strength (TS), and elongation at break (e%) estimated at 2950 MPa, 50.5 MPa, and 5.5%, respectively. Furthermore, we exhibited that the fungal nanochitosan (NC) film presented very good long-term antioxidant effect (reached 82.4% after 96 h of contact with DPPH radical solution) and very interesting antimicrobial activity when the nanochitosan (NC) fibers are mainly activated as NC-NH3+ form at the surface of the film with 45% reduction and 75% reduction observed for S. aureus (Gram-positive) and E. coli (Gram-negative), respectively, after 6 h of treatment. These promising antimicrobial and antioxidant activities indicated the high potential of valorization toward biomedical applications.

Preparation, Characterization and Gelation of a Fungal Nano Chitin Derived from Hericium erinaceus Residue

Nano chitin is a promising biocompatible material with wide applications. In this work, a fungal-derived nano chitin was prepared from Hericium erinaceus residue via mineral/protein purification and subsequent TEMPO-mediated oxidation. The structure, dispersity, and gelation ability of the prepared fungal nano chitin were studied. The results showed that the average length and width of the prepared fungal nano chitin were 336.6 nm and 6.4 nm, respectively, and the aspect ratio exceeded 50:1. The nano chitin retained the basic structure of chitin, while the crystallization index was improved. In addition, the dispersity of the nano chitin in aqueous media was evaluated by the effective diameter, and the polydispersion index was mainly affected by pH and ionic strength. Under acetic acid "gas phase coagulation", the prepared nano chitin dispersions with mass concentrations of 0.2, 0.4, 0.6, and 0.8% were converted into gels by enhanced hydrogen bond crosslinking between nano chitins.

Nanoparticle-containing electrospun nanofibrous scaffolds for sustained release of SDF-1α

Chemokines such as stromal cell-derived factor-1α (SDF-1α) regulate the migration of cancer cells that can spread from their primary tumor site by migrating up an SDF-1α concentration gradient, facilitating their local invasion and metastasis. Therefore, the implantation of SDF-1α-releasing scaffolds can be a useful strategy to trap cancer cells expressing the CXCR4 receptor. In this work, SDF-1α was encapsulated into poly(lactic-co-glycolic acid) (PLGA)-based nanoparticles and subsequently electrospun with chitosan to produce nanofibrous scaffolds of average fiber diameter of 261 ± 45 nm, intended for trapping glioblastoma (GBM) cells. The encapsulated SDF-1α maintained its biological activity after the electrospinning process as assessed by its capacity to induce the migration of cancer cells. The scaffolds could also provide sustained release of SDF-1α for at least 5 weeks. Using NIH3T3 mouse fibroblasts, human Thp-1 macrophages, and rat primary astrocytes we showed that the scaffolds possessed high cytocompatibility in vitro. Furthermore, a 7-day follow-up of Fischer rats bearing implanted scaffolds demonstrated the absence of adverse effects in vivo. In addition, the nanofibrous structure of the scaffolds provided excellent anchoring sites to support the adhesion of human GBM cells by extension of their pseudopodia. The scaffolds also demonstrated slow degradation kinetics, which may be useful in maximizing the time window for trapping GBM cells. As surgical resection does not permit a complete removal of GBM tumors, our results support the future implantation of these scaffolds into the walls of the resection cavity to evaluate their capacity to attract and trap the residual GBM cells in the brain.

Green electrospinning of chitin propionate to manufacture nanofiber mats

Chitin is the second most abundant biopolymer after cellulose in nature, and it is currently under-utilized partially because of its insolubility in common solvents. Herein, chitin was propionylated to improve its dissolution in green solvents, i.e., ethanol and water, and manufactured nanofibers and nonwoven mats via electrospinning with poly(ethylene oxide) (PEO) as a co-spinning aid. Polymer solution viscosity, electrospun CP/PEO fiber morphology, mechanical, thermal, dynamic thermal, and surface contact angle of nanofiber mats were evaluated. Results showed that fibers with CP content up to 97% could be produced. The electrospun CP/PEO nanofiber mats exhibited good mechanical strength, thermal stability, and hydrophobicity with water contact angles up to 133°. Filtration test of separating carbon nanofibers and carbon nanotubes from water demonstrated the potential use of the CP/PEO nanofiber mats in fluid filtration of fibrous pollutants.

Innovative High-Pressure Fabrication Processes for Porous Biomaterials-A Review

Biomaterials and their clinical application have become well known in recent years and progress in their manufacturing processes are essential steps in their technological advancement. Great advances have been made in the field of biomaterials, including ceramics, glasses, polymers, composites, glass-ceramics and metal alloys. Dense and porous ceramics have been widely used for various biomedical applications. Current applications of bioceramics include bone grafts, spinal fusion, bone repairs, bone fillers, maxillofacial reconstruction, etc. One of the common impediments in the bioceramics and metallic porous implants for biomedical applications are their lack of mechanical strength. High-pressure processing can be a viable solution in obtaining porous biomaterials. Many properties such as mechanical properties, non-toxicity, surface modification, degradation rate, biocompatibility, corrosion rate and scaffold design are taken into consideration. The current review focuses on different manufacturing processes used for bioceramics, polymers and metals and their alloys in porous forms. Recent advances in the manufacturing technologies of porous ceramics by freeze isostatic pressure and hydrothermal processing are discussed in detail. Pressure as a parameter can be helpful in obtaining porous forms for biomaterials with increased mechanical strength.

Recent applications of electrical, centrifugal, and pressurised emerging technologies for fibrous structure engineering in drug delivery, regenerative medicine and theranostics

Advancements in technology and material development in recent years has led to significant breakthroughs in the remit of fiber engineering. Conventional methods such as wet spinning, melt spinning, phase separation and template synthesis have been reported to develop fibrous structures for an array of applications. However, these methods have limitations with respect to processing conditions (e.g. high processing temperatures, shear stresses) and production (e.g. non-continuous fibers). The materials that can be processed using these methods are also limited, deterring their use in practical applications. Producing fibrous structures on a nanometer scale, in sync with the advancements in nanotechnology is another challenge met by these conventional methods. In this review we aim to present a brief overview of conventional methods of fiber fabrication and focus on the emerging fiber engineering techniques namely electrospinning, centrifugal spinning and pressurised gyration. This review will discuss the fundamental principles and factors governing each fabrication method and converge on the applications of the resulting spun fibers; specifically, in the drug delivery remit and in regenerative medicine.

Electrospun Nanofibrous Membranes for Tissue Engineering and Cell Growth

In biotechnology, the field of cell cultivation is highly relevant. Cultivated cells can be used, for example, for the development of biopharmaceuticals and in tissue engineering. Commonly, mammalian cells are grown in bioreactors, T-flasks, well plates, etc., without a specific substrate. Nanofibrous mats, however, have been reported to promote cell growth, adhesion, and proliferation. Here, we give an overview of the different attempts at cultivating mammalian cells on electrospun nanofiber mats for biotechnological and biomedical purposes. Starting with a brief overview of the different electrospinning methods, resulting in random or defined fiber orientations in the nanofiber mats, we describe the typical materials used in cell growth applications in biotechnology and tissue engineering. The influence of using different surface morphologies and polymers or polymer blends on the possible application of such nanofiber mats for tissue engineering and other biotechnological applications is discussed. Polymer blends, in particular, can often be used to reach the required combination of mechanical and biological properties, making such nanofiber mats highly suitable for tissue engineering and other biotechnological or biomedical cell growth applications.

Preparation of Magnetic-Luminescent Bifunctional Rapeseed Pod-Like Drug Delivery System for Sequential Release of Dual Drugs

Drug delivery systems (DDSs) limited to a single function or single-drug loading are struggling to meet the requirements of clinical medical applications. It is of great significance to fabricate DDSs with multiple functions such as magnetic targeting or fluorescent labeling, as well as with multiple-drug loading for enhancing drug efficacy and accelerating actions. In this study, inspired by the dual-chamber structure of rapeseed pods, biomimetic magnetic–luminescent bifunctional drug delivery carriers (DDCs) of 1.9 ± 0.3 μm diameter and 19.6 ± 4.4 μm length for dual drug release were fabricated via double-needle electrospraying. Morphological images showed that the rapeseed pod-like DDCs had a rod-like morphology and Janus dual-chamber structure. Magnetic nanoparticles and luminescent materials were elaborately designed to be dispersed in two different chambers to endow the DDCs with excellent magnetic and luminescent properties. Synchronously, the Janus structure of DDCs promoted the luminescent intensity by at least threefold compared to single-chamber DDCs. The results of the hemolysis experiment and cytotoxicity assay suggested the great blood and cell compatibilities of DDCs. Further inspired by the core–shell structure of rapeseeds containing oil wrapped in rapeseed pods, DDCs were fabricated to carry benzimidazole molecules and doxorubicin@chitosan nanoparticles in different chambers, realizing the sequential release of benzimidazole within 12 h and of doxorubicin from day 3 to day 18. These rapeseed pod-like DDSs with excellent magnetic and luminescent properties and sequential release of dual drugs have potential for biomedical applications such as targeted drug delivery, bioimaging, and sustained treatment of diseases.

Electrosprayed Shrimp and Mushroom Nanochitins on Cellulose Tissue for Skin Contact Application

Cosmetics has recently focused on biobased skin-compatible materials. Materials from natural sources can be used to produce more sustainable skin contact products with enhanced bioactivity. Surface functionalization using natural-based nano/microparticles is thus a subject of study, aimed at better understanding the skin compatibility of many biopolymers also deriving from biowaste. This research investigated electrospray as a method for surface modification of cellulose tissues with chitin nanofibrils (CNs) using two different sources-namely, vegetable (i.e., from fungi), and animal (from crustaceans)-and different solvent systems to obtain a biobased and skin-compatible product. The surface of cellulose tissues was uniformly decorated with electrosprayed CNs. Biological analysis revealed that all treated samples were suitable for skin applications since human dermal keratinocytes (i.e., HaCaT cells) successfully adhered to the processed tissues and were viable after being in contact with released substances in culture media. These results indicate that the use of solvents did not affect the final cytocompatibility due to their effective evaporation during the electrospray process. Such treatments did not also affect the characteristics of cellulose; in addition, they showed promising anti-inflammatory and indirect antimicrobial activity toward dermal keratinocytes in vitro. Specifically, cellulosic substrates decorated with nanochitins from shrimp showed strong immunomodulatory activity by first upregulating then downregulating the pro-inflammatory cytokines, whereas nanochitins from mushrooms displayed an overall anti-inflammatory activity via a slight decrement of the pro-inflammatory cytokines and increment of the anti-inflammatory marker. Electrospray could represent a green method for surface modification of sustainable and biofunctional skincare products.

Silver/Copper Nanoparticle-Modified Polymer Chitosan/PVA Blend Fibers

In this study, chitosan (CS)/poly(vinyl alcohol) (PVA) (CS/PVA) blend nanofibers with varying weight ratios and silver (Ag)/copper (Cu)/CS/PVA composite fibers have been prepared successfully by the electrospinning process. The tip-to-collector distance was kept at 15 cm, and the applied voltage was varied from 15 to 25 kV. The effects of the weight ratios and applied voltage on the morphology and diameter of the fibers were investigated. The resultant fibers were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The SEM results showed that increasing the amount of chitosan in the CS/PVA blend resulted in a decrease in the fiber diameter from 162 to 89 nm while an increase in the voltage from 15 to 25 kV led to a decrease in the fiber diameters. Furthermore, the SEM results indicated that an increase in the fiber diameter from 161 to 257 nm was observed while morphological changes were also observed upon the Ag/Cu addition. The latter changes are perceived to be a result of increased conductivity and higher charge density.

Chitin and chitosan on the nanoscale

In a matter of decades, nanomaterials from biomass, exemplified by nanocellulose, have rapidly transitioned from once being a subject of curiosity to an area of fervent research and development, now reaching the stages of commercialization and industrial relevance. Nanoscale chitin and chitosan, on the other hand, have only recently begun to raise interest. Attractive features such as excellent biocompatibility, antibacterial activity, immunogenicity, as well as the tuneable handles of their acetylamide (chitin) or primary amino (chitosan) functionalities indeed display promise in areas such as biomedical devices, catalysis, therapeutics, and more. Herein, we review recent progress in the fabrication and development of these bio-nanomaterials, describe in detail their properties, and discuss the initial successes in their applications. Comparisons are made to the dominant nanocelluose to highlight some of the inherent advantages that nanochitin and nanochitosan may possess in similar application.

Chitin Nanofiber-Reinforced Waterborne Polyurethane Nanocomposite Films with Enhanced Thermal and Mechanical Performance

To attain eco-friendly polyurethane composites with enhanced thermal and mechanical properties, in this study, a series of cationic waterborne polyurethane (cWPU) nanocomposite films reinforced with 1-50 wt% chitin nanofiber (ChNF) loadings was fabricated by a facile aqueous dispersion casting. The microstructure, thermal and mechanical properties of the nanocomposite films were investigated by considering the loading content and the interfacial interaction of ChNF in the cWPU matrix. For the purpose, a hard/soft segmented cWPU with an average particle size of ∼151 nm in aqueous dispersion was synthesized by using poly(tetramethylene glycol), isophorone diisocyanate, N-methyldiethanolamine, and 1,4-butanediol. The FT-IR spectra confirmed the existence of specific hydrogen-bonding interactions between hydroxyl/acetyl amine/ammonium groups of ChNFs and urethane/protonated amine groups of cWPU hard segments. Accordingly, the thermal decomposition temperatures of cWPU/ChNF nanocomposite films increased with increasing the ChNF content. In addition, the storage moduli of cWPU/ChNF nanocomposite films increased significantly with the increment of ChNF content up to ∼7 wt%, which stems from the restricted chain mobility of cWPU backbones composed of semicrystalline soft segments and hard segments interacting with ChNFs via multiple hydrogen-bonding interactions.

Preparation of a novel double crosslinked chitin aerogel via etherification with high strength

In this study, we introduced a novel double crosslinked chitin aerogel via etherification with EGDE for mechanical reinforcement. Samples with different EGDE: chitin weight ratios from 0 to 1.5:1 were fabricated through chitin dissolution in KOH/urea aqueous solution, ethanol neutralization and washing, and supercritical CO₂ drying. Both the physical and chemical crosslinking maintained the high porosity and light weight of chitin aerogels. The morphology under SEM has shown the close-ended and denser fibrils alignment for EGDE crosslinked aerogels and the mesoporous and macroporous structure induced by emulsion effect from excessive EGDE. FTIR characterization was conducted for chemical structure analysis. Compressive testing showed an increase of 247 % compressive strength at 10 % strain and 243 % modulus could be achieved at 1.0 EGDE samples. TGA results revealed a delayed thermal degradation for the chemically crosslinked samples. This study demonstrates EGDE an effective chemical crosslinker for reinforced chitin aerogels.

Electrospun Biomaterials from Chitosan Blends Applied as Scaffold for Tissue Regeneration

Our objective in this work was to summarize the main results obtained in processing pure chitosan and chitosan/hyaluronan complex in view of biomedical applications, taking advantage of their original properties. In addition, an electrospinning technique was selected to prepare nanofiber mats well adapted for tissue engineering in relation to the large porosity of the materials, allowing an exchange with the environment. The optimum conditions for preparation of purified and stable nanofibers in aqueous solution and phosphate buffer pH = 7.4 are described. Their mechanical properties and degree of swelling are given. Then, the prepared biomaterials are investigated to test their advantage for chondrocyte development after comparison of nanofiber mats and uniform films. For that purpose, the adhesion of cells is studied by atomic force microscopy (AFM) using single-cell force spectroscopy, showing the good adhesion of chondrocytes on chitosan. At the end, adhesion and proliferation of chondrocytes in vitro are examined and clearly show the interest of chitosan nanofiber mats compared to chitosan film for potential application in tissue engineering.

Biopolymer Nanofibers for Nanogenerator Development

The development of nanogenerators (NGs) with optimal performances and functionalities requires more novel materials. Over the past decade, biopolymer nanofibers (BPNFs) have become critical sustainable building blocks in energy-related fields because they have distinctive nanostructures and properties and can be obtained from abundant and renewable resources. This review summarizes recent advances in the use of BPNFs for NG development. We will begin by introducing various strategies for fabricating BPNFs with diverse structures and performances. Then, we will systematically present the utilization of polysaccharide and protein nanofibers for NGs. We will mainly focus on the use of BPNFs to generate bulk materials with tailored structures and properties for assembling of triboelectric and piezoelectric NGs. The use of BPNFs to construct NGs for the generation of electricity from moisture and osmosis is also discussed. Finally, we illustrate our personal perspectives on several issues that require special attention with regard to future developments in this active field.

Curdlan-Chitosan Electrospun Fibers as Potential Scaffolds for Bone Regeneration

Polysaccharides have received a lot of attention in biomedical research for their high potential as scaffolds owing to their unique biological properties. Fibrillar scaffolds made of chitosan demonstrated high promise in tissue engineering, especially for skin. As far as bone regeneration is concerned, curdlan (1,3-β-glucan) is particularly interesting as it enhances bone growth by helping mesenchymal stem cell adhesion, by favoring their differentiation into osteoblasts and by limiting the osteoclastic activity. Therefore, we aim to combine both chitosan and curdlan polysaccharides in a new scaffold for bone regeneration. For that purpose, curdlan was electrospun as a blend with chitosan into a fibrillar scaffold. We show that this novel scaffold is biodegradable (8% at two weeks), exhibits a good swelling behavior (350%) and is non-cytotoxic in vitro. In addition, the benefit of incorporating curdlan in the scaffold was demonstrated in a scratch assay that evidences the ability of curdlan to express its immunomodulatory properties by enhancing cell migration. Thus, these innovative electrospun curdlan–chitosan scaffolds show great potential for bone tissue engineering.

Bio-Based Electrospun Fibers for Wound Healing

Being designated to protect other tissues, skin is the first and largest human body organ to be injured and for this reason, it is accredited with a high capacity for self-repairing. However, in the case of profound lesions or large surface loss, the natural wound healing process may be ineffective or insufficient, leading to detrimental and painful conditions that require repair adjuvants and tissue substitutes. In addition to the conventional wound care options, biodegradable polymers, both synthetic and biologic origin, are gaining increased importance for their high biocompatibility, biodegradation, and bioactive properties, such as antimicrobial, immunomodulatory, cell proliferative, and angiogenic. To create a microenvironment suitable for the healing process, a key property is the ability of a polymer to be spun into submicrometric fibers (e.g., via electrospinning), since they mimic the fibrous extracellular matrix and can support neo- tissue growth. A number of biodegradable polymers used in the biomedical sector comply with the definition of bio-based polymers (known also as biopolymers), which are recently being used in other industrial sectors for reducing the material and energy impact on the environment, as they are derived from renewable biological resources. In this review, after a description of the fundamental concepts of wound healing, with emphasis on advanced wound dressings, the recent developments of bio-based natural and synthetic electrospun structures for efficient wound healing applications are highlighted and discussed. This review aims to improve awareness on the use of bio-based polymers in medical devices.

Electrospun Nano-Fibers for Biomedical and Tissue Engineering Applications: A Comprehensive Review

Pharmaceutical nano-fibers have attracted widespread attention from researchers for reasons such as adaptability of the electro-spinning process and ease of production. As a flexible method for fabricating nano-fibers, electro-spinning is extensively used. An electro-spinning unit is composed of a pump or syringe, a high voltage current supplier, a metal plate collector and a spinneret. Optimization of the attained nano-fibers is undertaken through manipulation of the variables of the process and formulation, including concentration, viscosity, molecular mass, and physical phenomenon, as well as the environmental parameters including temperature and humidity. The nano-fibers achieved by electro-spinning can be utilized for drug loading. The mixing of two or more medicines can be performed via electro-spinning. Facilitation or inhibition of the burst release of a drug can be achieved by the use of the electro-spinning approach. This potential is anticipated to facilitate progression in applications of drug release modification and tissue engineering (TE). The present review aims to focus on electro-spinning, optimization parameters, pharmacological applications, biological characteristics, and in vivo analyses of the electro-spun nano-fibers. Furthermore, current developments and upcoming investigation directions are outlined for the advancement of electro-spun nano-fibers for TE. Moreover, the possible applications, complications and future developments of these nano-fibers are summarized in detail.