Chitin and chitosan polymers: Chemistry, solubility and fiber formation

Chitosan coating silver nanoparticles as a promising feed additive in broilers chicken

The present study aimed to evaluate the potential of chitosan coating silver nanoparticles to enhance the growth performance and immune status of broilers without inducing oxidative stress-related pathological lesions in any organs or leaving residues of silver in the edible parts. Five clusters of Cobb one-day-old chicks (n = 10/group in each replication) were given oral therapy, once a week for 36 days as follows: (1) distilled water, (2, 3) 0.5- and 5 ppm silver nanoparticles (AgNPs), respectively, (4, 5) 0.5- and 5 ppm chitosan/silver nanoconjugates (CS/Ag-NCs), respectively. The results demonstrated a marked elevation in the body weight gain with a decline in the food conversion ratio and marked improvement in feeding and drinking behavior of all nanoparticles treated groups, but higher in CS/Ag-NCs groups than AgNPs groups and control group. In contrast to the 0.5 ppm AgNPs receiving group, the group receiving 5 ppm AgNPs noticed remarkable histological changes in some organs, including the liver, kidneys, spleen, and heart. Moreover, the administration of CS/Ag-NCs at two dosage levels didn't influence any histological changes. The AgNPs groups' antibody titers against the ND and AI viruses were almost identical to those of the control group. Otherwise, CS/Ag-NCs groups recorded the highest antibody titers. Additionally, there was a significant increase in silver content in most edible organs of AgNPs groups at a dosage level of 5 ppm. Otherwise, the coating of AgNPs by CSNPs could decrease the aggregation of silver in the biological organs. Thus, we recommend utilizing 0.5 ppm CS/Ag-NCs in broiler farms to promote their growth performance and strengthen their immune defense.

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.

Application of electrospun chitosan-based nanofibers as immobilization matrix for biomolecules

Nanofiber meshes from electrospun chitosan, highly modified with biotin and arylazides, are well-suited for application as enzyme immobilization matrices. To test this, catalytically active biomolecules were immobilized onto photocrosslinked nanofibrous nonwovens consisting mainly of biotinylated fungal chitosan and a small amount (10 w%) of poly ethylene oxide. In this study, we show that over 10 μg eugenol oxidase per milligram dry polymer matrix can be loaded on UV-crosslinked chitosan nanofibers. We further demonstrate that bound enzyme activity can be fully retained for over 7 days of storage at ambient conditions in aqueous buffer. Samples loaded at maximum enzyme carrying capacity were tested in a custom-made plug-flow reactor system with online UV-VIS spectroscopy for activity determination. High wettability and durability of the hydrophilic chitosan support matrix enabled continuous oxidation of model substrate vanillyl alcohol into vanillin with constant turnover at flow rates of up to 0.24 L/h for over 6 h. This proves the above hypothesis and enables further application of the fibers as stacked microfluidic membranes, biosensors, or structural starting points for affinity crosslinked enzyme gels. KEY POINTS: • Biotinylated chitosan-based nanofibers retain enzymes via mild affinity interactions • Immobilized eugenol oxidase shows high activity and resists continuous washing • Nanofiber matrix material tolerated high flow rates in a continuous-flow setup.

Instantaneous and reversible flocculation of Scenedesmus via Chitosan and Xanthan Gum complexation

An instantaneous and reversible flocculation method for Scenedesmus harvesting was developed, based on the complexation of Chitosan (CTS) and Xanthan Gum (XG). Under rapid stirring, Scenedesmus cells formed centimeter-sized flocs within 20 s using binary flocculants of 4 mg/L CTS and 16 mg/L XG. These flocs exhibited a remarkable harvest efficiency exceeding 95 % when filtered through 500-μm-pore-sized sieves. Furthermore, the flocs could be completely disintegrated by using alkaline or NaCl solutions (pH > 11 or NaCl concentration > 1.5 mol/L). Adjusting pH allowed recovery of 50 % CTS and 75 % XG, resulting in microalgae biomass with lower flocculant content and reducing reagent costs. Electrostatic interaction of -COO- of XG and -NH3+ of CTS deduced the formation of polyelectrolyte complexes (PECs), which shrink and wrap the coexisting algal cells to form the flocs under stirring. CTS and XG complexation was instantaneous and reversible, explaining quick flocculation and disintegration.

The source, activity influencing factors and biological activities for future development of chitin deacetylase

Chitin deacetylase (CDA), a prominent member of the carbohydrate esterase enzyme family 4 (CE4), is found ubiquitously in bacteria, fungi, insects, and crustaceans. This metalloenzyme plays a pivotal role in recognizing and selectively removing acetyl groups from chitin, thus offering an environmentally friendly and biologically-driven preparation method for chitosan with immense industrial potential. Due to its diverse origins, CDAs sourced from different organisms exhibit unique functions, optimal pH ranges, and temperature preferences. Furthermore, certain organic reagents can induce structural changes in CDAs, influencing their catalytic activity. Leveraging CDA's capabilities extends beyond chitosan biocatalysis, as it demonstrates promising application value in agricultural pest control. In this paper, the source, reaction mechanism, influencing factors, the fermentation methods and applications of CDA are reviewed, which provides theoretical help for the research and application of CDA.

Chitosan from Marine Amphipods Inhibits the Wilt Banana Pathogen Fusarium oxysporum f. sp. Cubense Tropical Race 4

In this work, we extracted chitosan from marine amphipods associated with aquaculture facilities and tested its use in crop protection. The obtained chitosan was 2.5 ± 0.3% of initial ground amphipod dry weight. The chemical nature of chitosan from amphipod extracts was confirmed via Raman scattering spectroscopy and Fourier transform infrared spectroscopy (FTIR). This chitosan showed an 85.7-84.3% deacetylation degree. Chitosan from biofouling amphipods at 1 mg·mL-1 virtually arrested conidia germination (ca. sixfold reduction from controls) of the banana wilt pathogenic fungus Fusarium oxysporum f. sp cubense Tropical Race 4 (FocTR4). This concentration reduced (ca. twofold) the conidia germination of the biocontrol fungus Pochonia chlamydosporia (Pc123). Chitosan from amphipods at low concentrations (0.01 mg·mL-1) still reduced FocTR4 germination but did not affect Pc123. This is the first time that chitosan is obtained from biofouling amphipods. This new chitosan valorizes aquaculture residues and has potential for biomanaging the diseases of food security crops such as bananas.

Strategies for the Preparation of Chitosan Derivatives for Antimicrobial, Drug Delivery, and Agricultural Applications: A Review

Chitosan has received much attention for its role in designing and developing novel derivatives as well as its applications across a broad spectrum of biological and physiological activities, owing to its desirable characteristics such as being biodegradable, being a biopolymer, and its overall eco-friendliness. The main objective of this review is to explore the recent chemical modifications of chitosan that have been achieved through various synthetic methods. These chitosan derivatives are categorized based on their synthetic pathways or the presence of common functional groups, which include alkylated, acylated, Schiff base, quaternary ammonia, guanidine, and heterocyclic rings. We have also described the recent applications of chitosan and its derivatives, along with nanomaterials, their mechanisms, and prospective challenges, especially in areas such as antimicrobial activities, targeted drug delivery for various diseases, and plant agricultural domains. The accumulation of these recent findings has the potential to offer insight not only into innovative approaches for the preparation of chitosan derivatives but also into their diverse applications. These insights may spark novel ideas for drug development or drug carriers, particularly in the antimicrobial, medicinal, and plant agricultural fields.

Synthesis of Thermoplastic Mixed Chitin Esters

Mixed chitin esters, that is, chitin benzoate stearates, exhibiting thermoplasticity, were synthesized by the acylation of chitin using benzoyl and stearoyl chlorides in the presence of pyridine and N,N-dimethyl-4-aminopyridine for 1 h + 24 h at 100 °C in an ionic liquid, 1-allyl-3-methylimidazolium bromide. IR and 1H NMR spectroscopic analyses confirmed the formation of the desired chitin benzoate stearates. Powder X-ray diffraction analysis of the products indicated that the crystalline structures of the chitin main-chains and stearoyl side-chains were strongly affected by the benzoyl/stearoyl substituent ratios. Introducing a small number of benzoyl groups, in addition to a large ratio of stearoyl groups, contributed to disrupting the intrinsic chitin crystals and enabling the chitin main chains and stearoyl side chains to form regularly controlled layered and parallel arrays, respectively. The resulting products exhibited meting points, associated with regular stearoyl packings, and formed melt-pressed films during the melt-pressing process. These results suggest that chitin benzoate stearates with appropriate benzoyl/stearoyl substituent ratios exhibit thermoplasticity.

Complex Evaluation of Nanocomposite-Based Hydroxyapatite for Biomedical Applications

A magnesium-doped hydroxyapatite in chitosan matrix (MgHApC) sample was developed as a potential platform for numerous applications in the pharmaceutical, medical, and food industries. Magnesium-doped hydroxyapatite suspensions in the chitosan matrix were obtained by the coprecipitation technique. The surface shape and morphological features were determined by scanning electron microscopy (SEM). The hydrodynamic diameter of the suspended particles was determined by Dynamic light scattering (DLS) measurements. The stability of MgHApC suspensions was evaluated by ultrasonic measurements. The hydrodynamic diameter of the MgHApC particles in suspension was 29.5 nm. The diameter of MgHApC particles calculated from SEM was 12.5 ± 2 nm. Following the SEM observations, it was seen that the MgHApC particles have a spherical shape. The Fourier-transform infrared spectroscopy (FTIR) studies conducted on MgHApC proved the presence of chitosan and hydroxyapatite in the studied specimens. In vitro antimicrobial assays were performed on Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231 microbial strains. The antimicrobial experiments showed that MgHApC exhibited very good antimicrobial properties against all the tested microorganisms. More than that, the results of the in vitro studies revealed that the antimicrobial properties of the samples depend on the incubation time. The evaluation of the sample's cytotoxicity was performed using the human colon cancer (HCT-8) cell line. Our results suggested the great potential of MgHApC to be used in future applications in the field of biomedical applications (e.g., dentistry, orthopedics, etc.).

Natural bone inspired core-shell triple-layered gel/PCL/gel 3D printed scaffolds for bone tissue engineering

Despite technological advancements in bone tissue engineering, it is still a challenge to fabricate a scaffold with high bioactivity as well as high mechanical strength that can promote osteogenesis as well as bear load. Here we developed a 3D printed gel-polymer multi-layered hybrid scaffold. The innermost layer is porous gel-based framework made of gelatin/carboxymethyl-chitin/nano-hydroxyapatite and is cryogenically 3D printed. Further, the second and middle layer of micro-engineered polycaprolactone (PCL) is infused in the gel with controlled penetration and tuneable coating thickness. The PCL surface is further coated with a third and final thin layer of gel matrix used for the first layer. This triple-layered structure demonstrates compression strength and modulus of 13.07 ± 1.15 MPa and 21.8 ± 0.82 MPa, respectively, post 8 weeks degradation which is >3000% and >700% than gel scaffold. It also shows degradation of 6.84 ± 0.70% (83% reduction than gel scaffold) after 12 weeks and swelling of 69.09 ± 6.83% (81% reduction) as compared to gel scaffolds. Further, nearly 300%, 250%, 50%, and 440% increase in cellular attachment, proliferation, protein generation, and mineralization, respectively are achieved as compared to only PCL scaffolds. Thus, these hybrid scaffolds offer high mechanical strength, slow degradation rate, high bioactivity, and high osteoconductivity. These multifunctional scaffolds have potential for reconstructing non-load-bearing bone defects like sinus lift, jaw cysts, and moderate load-bearing like reconstructing hard palate, orbital palate, and other craniomaxillofacial bone defects.

Evaluation of Gelation Properties of Salt-Soluble Proteins Extracted from Protaetia brevitarsis Larvae and Tenebrio molitor Larvae and Application to Pork Myofibrillar Protein Gel System

The purpose of this study was to investigate the functional properties of salt-soluble proteins obtained from Protaetia brevitarsis (PB) and Tenebrio molitor (TM) larvae, the interaction between these proteins and pork myofibrillar protein (MP) in a gel system. The gel properties of salt-soluble protein extracts showed that the PB had a higher viscosity than the TM protein. However, the TM protein had higher gel strength compared with the PB protein. The gelation characteristics of the pork MP gel systems added with lyophilized insect salt-soluble protein powder showed to decrease slightly viscosity compared with MP alone. Adding the TM or PB protein powder did not affect the pork MP's hydrophobicity and sulfhydryl group levels. Furthermore, the protein bands of the MP did not change with the type or amount of insect salt-soluble protein. The cooking yields of the pork MP gels containing PB or TM protein powder were higher than those without insect protein. Regardless of the type of insect salt-soluble protein added, the pork MP's gel strength decreased. Furthermore, as the level of insect powder increased, the surface protein structure became rough and porous. The results demonstrated that proteins extracted from PB and TM larvae interfered with the gelation of pork MP in a gel system.

Chitin, chitosan and chitooligosaccharides as potential growth promoters and immunostimulants in aquaculture: A comprehensive review

There is a stable growth in aquaculture production to avoid seafood scarcity. The usage of eco-friendly feed additives is not only associated with aquatic animal health but also reduces the risk of deleterious effects to the environment and consumers. Aquaculture researchers are seeking dietary solutions to improve the growth performance and yield of target organisms. A wide range of naturally derived compounds such as probiotics, prebiotics, synbiotics, complex carbohydrates, nutritional factors, herbs, hormones, vitamins, and cytokines was utilized as immunostimulants in aquaculture. The use of polysaccharides derived from natural resources, such as alginate, agar, laminarin, carrageenan, fucoidan, chitin, and chitosan, as supplementary feed in aquaculture species has been reported. Polysaccharides are prebiotic substances which are enhancing the immunity, disease resistance and growth of aquatic animals. Further, chitin (CT), chitosan (CTS) and chitooligosaccharides (COS) were recognized for their biodegradable properties and unique biological functions. The dietary effects of CT, CTS and COS at different inclusion levels on growth performance, immune response and gut microbiota in aquaculture species has been reviewed. The safety regulations, challenges and future outlooks of CT, CTS and COS in aquatic animals have been discussed in this review.

MXene-Mediated Cellulose Conductive Hydrogel with Ultrastretchability and Self-Healing Ability

Constructing natural polymers such as cellulose, chitin, and chitosan into hydrogels with excellent stretchability and self-healing properties can greatly expand their applications but remains very challenging. Generally, the polysaccharide-based hydrogels have suffered from the trade-off between stiffness of the polysaccharide and stretchability due to the inherent nature. Thus, polysaccharide-based hydrogels (polysaccharides act as the matrix) with self-healing properties and excellent stretchability are scarcely reported. Here, a solvent-assisted strategy was developed to construct MXene-mediated cellulose conductive hydrogels with excellent stretchability (∼5300%) and self-healability. MXene (an emerging two-dimensional nanomaterial) was introduced as emerging noncovalent cross-linking sites between the solvated cellulose chains in a benzyltrimethylammonium hydroxide aqueous solution. The electrostatic interaction between the cellulose chains and terminal functional groups (O, OH, F) of MXene led to cross-linking of the cellulose chains by MXene to form a hydrogel. Due to the excellent properties of the cellulose-MXene conductive hydrogel, the work not only enabled their strong potential in both fields of electronic skins and energy storage but provided fresh ideas for some other stubborn polymers such as chitin to prepare hydrogels with excellent properties.

A review on heavy metal biosorption utilizing modified chitosan

Heavy metal pollution in water bodies is a global concern. The prominent source of metal contamination in aqueous streams and groundwater is wastewater containing heavy metal ions. Elevated concentrations of heavy metals in water bodies can have a negative impact on water quality and public health. The most effective way to remove metal contaminants from drinking water is thought to be adsorption. A deacetylated derivative of chitin, chitosan, has a wide range of commercial uses since it is biocompatible, nontoxic, and biodegradable. Due to its exceptional adsorption behavior toward numerous hazardous heavy metals from aqueous solutions, chitosan and its modifications have drawn a lot of interest in recent years. Due to its remarkable adsorption behavior toward a range of dangerous heavy metals, chitosan is a possible agent for eliminating metals from aqueous solutions. The review has focused on the ideas of biosorption, its kinds, architectures, and characteristics, as well as using modified (physically and chemically modified) chitosan, blends, and composites to remove heavy metals from water. The main objective of the review is to describe the most important aspects of chitosan-based adsorbents that might be beneficial for enhancing the adsorption capabilities of modified chitosan and promoting the usage of this material in the removal of heavy metal pollutants.

Untapped Potential of Deep Eutectic Solvents for the Synthesis of Bioinspired Inorganic-Organic Materials

Since the discovery of deep eutectic solvents (DESs) in 2003, significant progress has been made in the field, specifically advancing aspects of their preparation and physicochemical characterization. Their low-cost and unique tailored properties are reasons for their growing importance as a sustainable medium for the resource-efficient processing and synthesis of advanced materials. In this paper, the significance of these designer solvents and their beneficial features, in particular with respect to biomimetic materials chemistry, is discussed. Finally, this article explores the unrealized potential and advantageous aspects of DESs, focusing on the development of biomineralization-inspired hybrid materials. It is anticipated that this article can stimulate new concepts and advances providing a reference for breaking down the multidisciplinary borders in the field of bioinspired materials chemistry, especially at the nexus of computation and experiment, and to develop a rigorous materials-by-design paradigm.

Effect of deacetylation of chitosan on the physicochemical, antioxidant and antibacterial properties activities of chitosan-mannose derivatives

BACKGROUND

The present study investigates the physical, chemical, and antibacterial properties of water-soluble chitosan derivatives. Preparation of the water-soluble chitosan derivatives was performed by the Maillard reaction (MR) between chitosan [with the degree of deacetylation (DD) being 50%, 70%, and 90%] and mannose. No organic reagent was used in the process. Systematic evaluations of the effects of chitosan DD on the reaction extent, the structure, the composition, as well as the physicochemical properties, antioxidant properties, and bacterial inhibitory properties of the finished chitosan-mannose MR products (Mc-mrps), were carried out.

RESULTS

Based on the experimental data obtained from Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, Pyrolysis-gas chromatography-mass spectrometry analysis, and 1 H-NMR, the Mc-mrps formed from chitosan with different DDs had different structures and components. An increase in the DD of chitosan led to a significant increase in the degree of reaction, color difference (△E), and solubility (P < 0.05). The zeta potential and particle size of the Mc-mrps were also influenced by the DD of chitosan. Additionally, the antimicrobial action against Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative bacteria (Escherichia coli and Salmonella typhimurium), as well as antioxidant activity, were enhanced by the incorporation of mannose. This was also achieved by the increase of the DD of chitosan.

CONCLUSION

The results of the present study suggest that chitosan was derived with mannose to yield a novel, water-soluble polysaccharide with better antioxidant and antimicrobial activities. The DD of chitosan had a significant effect on the properties of the Mc-mrp, which can serve as a reference point for the subsequent preparation and application of such derivatives. © 2023 Society of Chemical Industry.

Rapidly in situ forming an injectable Chitosan/PEG hydrogel for intervertebral disc repair

Intervertebral disc (IVD) degeneration occurred with the increasing age or accidents has puzzled peoples in daily life. To seal IVD defect by injectable hydrogels is a promising method for slowing down IVD degeneration. Herein, we reported a rapidly in situ forming injectable chitosan/PEG hydrogel (CSMA-PEGDA-L) through integrating photo-crosslink of methacrylate chitosan (CSMA) with Schiff base reaction between CSMA and aldehyde polyethylene glycol (PEGDA). The CSMA-PEGDA-L possessed a stronger compressive strength than the photo-crosslinked CSMA-L hydrogel and Schiff-base-crosslinked CSMA-PEGDA hydrogel. This chitosan/PEG hydrogel showed low cytotoxicity from incubation experiments of nucleus pulpous cells. When implanted on the punctured IVD of rat's tail, the CSMA-PEGDA-L hydrogel could well retard the progression of IVD degeneration through physical plugging, powerfully proven by radiological and histological evaluations. This work demonstrated the strategy of in situ injectable glue may be a potential solution for prevention of IVD degeneration.

The Effect of Chitosan on Physicochemical Properties of Whey Protein Isolate Scaffolds for Tissue Engineering Applications

New scaffolds, based on whey protein isolate (WPI) and chitosan (CS), have been proposed and investigated as possible materials for use in osteochondral tissue repair. Two types of WPI-based hydrogels modified by CS were prepared: CS powder was incorporated into WPI in either dissolved or suspended powder form. The optimal chemical composition of the resulting WPI/CS hydrogels was chosen based on the morphology, structural properties, chemical stability, swelling ratio, wettability, mechanical properties, bioactivity, and cytotoxicity evaluation. The hydrogels with CS incorporated in powder form exhibited superior mechanical properties and higher porosity, whereas those with CS incorporated after dissolution showed enhanced wettability, which decreased with increasing CS content. The introduction of CS powder into the WPI matrix promoted apatite formation, as confirmed by energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) analyses. In vitro cytotoxicity results confirmed the cytocompatibility of CS powder modified WPI hydrogels, suggesting their suitability as cell scaffolds. These findings demonstrate the promising potential of WPI/CS scaffolds for osteochondral tissue repair.

Advancements in Chitosan-Based Nanoparticles for Pulmonary Drug Delivery

The evolution of respiratory diseases represents a considerable public health challenge, as they are among the leading causes of death worldwide. In this sense, in addition to the high prevalence of diseases such as asthma, chronic obstructive pulmonary disease, pneumonia, cystic fibrosis, and lung cancer, emerging respiratory diseases, particularly those caused by members of the coronavirus family, have contributed to a significant number of deaths on a global scale over the last two decades. Therefore, several studies have been conducted to optimize the efficacy of treatments against these diseases, focusing on pulmonary drug delivery using nanomedicine. Thus, the development of nanocarriers has emerged as a promising alternative to overcome the limitations of conventional therapy, by increasing drug bioavailability at the target site and reducing unwanted side effects. In this context, nanoparticles composed of chitosan (CS) show advantages over other nanocarriers because chitosan possesses intrinsic biological properties, such as anti-inflammatory, antimicrobial, and mucoadhesive capacity. Moreover, CS nanoparticles have the potential to enhance drug stability, prolong the duration of action, improve drug targeting, control drug release, optimize dissolution of poorly soluble drugs, and increase cell membrane permeability of hydrophobic drugs. These properties could optimize the performance of the drug after its pulmonary administration. Therefore, this review aims to discuss the potential of chitosan nanoparticles for pulmonary drug delivery, highlighting how their biological properties can improve the treatment of pulmonary diseases, including their synergistic action with the encapsulated drug.

Advances, challenges, and prospects for surgical suture materials

As one of the long-established and necessary medical devices, surgical sutures play an essentially important role in the closing and healing of damaged tissues and organs postoperatively. The recent advances in multiple disciplines, like materials science, engineering technology, and biomedicine, have facilitated the generation of various innovative surgical sutures with humanization and multi-functionalization. For instance, the application of numerous absorbable materials is assuredly a marvelous progression in terms of surgical sutures. Moreover, some fantastic results from recent laboratory research cannot be ignored either, ranging from the fiber generation to the suture structure, as well as the suture modification, functionalization, and even intellectualization. In this review, the suture materials, including natural or synthetic polymers, absorbable or non-absorbable polymers, and metal materials, were first introduced, and then their advantages and disadvantages were summarized. Then we introduced and discussed various fiber fabrication strategies for the production of surgical sutures. Noticeably, advanced nanofiber generation strategies were highlighted. This review further summarized a wide and diverse variety of suture structures and further discussed their different features. After that, we covered the advanced design and development of surgical sutures with multiple functionalizations, which mainly included surface coating technologies and direct drug-loading technologies. Meanwhile, the review highlighted some smart and intelligent sutures that can monitor the wound status in a real-time manner and provide on-demand therapies accordingly. Furthermore, some representative commercial sutures were also introduced and summarized. At the end of this review, we discussed the challenges and future prospects in the field of surgical sutures in depth. This review aims to provide a meaningful reference and guidance for the future design and fabrication of innovative surgical sutures. STATEMENT OF SIGNIFICANCE: This review article introduces the recent advances of surgical sutures, including material selection, fiber morphology, suture structure and construction, as well as suture modification, functionalization, and even intellectualization. Importantly, some innovative strategies for the construction of multifunctional sutures with predetermined biological properties are highlighted. Moreover, some important commercial suture products are systematically summarized and compared. This review also discusses the challenges and future prospects of advanced sutures in a deep manner. In all, this review is expected to arouse great interest from a broad group of readers in the fields of multifunctional biomaterials and regenerative medicine.

Facile fabrication of chitosan Schiff bases from giant tiger prawn shells (Penaeus monodon) via solvent-free mechanochemical grafting

Fabrication of chitosan Schiff bases (ChSB) from giant tiger prawn shells (Penaeus monodon) using an environmentally friendly method has been conducted successfully. Transformation of Prawn Shells (PS) as raw material into chitin then chitosan was executed under ambient temperature. Later, three Ch Schiff bases (ChSB-A, ChSB-S, and ChSB-V) were successfully synthesized for the first time via solvent-free mechanochemical grafting with 2-hydroxy benzaldehyde, 4-methoxy benzaldehyde, and 3-methoxy-4-hydroxy benzaldehyde, respectively. Synthesis was carried out with Shaker Mill-Ultimate Gravity equipped with a Teflon jar with zirconia balls; then the product was characterized. FTIR analysis proved the conversion of free amine to imine groups. The degree of substitution (DS) and crystallinity index (CrI) were determined by elemental analysis and X-ray diffraction. The DS values obtained were about 0.343, 0.795, and 0.055 for ChSB-A, ChSB-S, and ChSB-V, respectively. The CrI of ChSB-A, ChSB-S, and ChSB-V was 53.3, 51.7, and 46.9 %, respectively. The thermal gravimetric analysis showed that the mechanochemical grafting of Ch improves the thermal stability of ChSB. This developed method provides a novel potential technique to convert PS into ChSB products by solvent-free mechanochemical grafting.

Active Cellulose Acetate/Chitosan Composite Films Prepared Using Solution Blow Spinning: Structure and Electrokinetic Properties

Cellulose acetate (CA), a very promising derivative of cellulose, has come into the focus of research due to its highly desired good film-forming ability for food packaging applications. Frequently, this derivative is used in combination with other compounds (polymers, nanoparticles) in order to obtain active materials. Here, we report the preparation of thin films made of cellulose acetate loaded with chitosan (CS) using the solution blow spinning (SBS) method. Films are prepared by SBS processing of the polymers mixture solution, considering the following variables: (i) the concentration of cellulose acetate and chitosan in the solution and (ii) the solvent system consisting of acetic or formic acid. The prepared materials are characterized in terms of physical properties, roughness (optical profilometer), porosity, wettability (contact angle measurements), chemical structure (Fourier transform infrared spectrometry), and electrokinetic properties (zeta potential). SBS enables the preparation of CA/CS films with high water vapor permeability, high porosity, and also higher water contact angle compared with pure CA films. The electrokinetic properties of composites are influenced by the inclusion of chitosan, which causes a shift of the isoelectric point (IEP) towards higher pH values, but the magnitude of the shift is not in correlation with chitosan concentration. Adsorption kinetic studies using bovine serum albumin (BSA) as a model protein reveal that chitosan modified cellulose acetate films manifest low affinity towards proteins that suggests prevention of biofilm formation on its surface.

Polymeric surfactants as ideal substitutes for sustainable corrosion protection: A perspective on colloidal and interface properties

Surfactants are well known for their colloidal and corrosion inhibition potential (CIP) due to their strong propensity to interact with metallic surfaces. However, because of their small molecular size and the fact that they are only effective at relatively high concentrations, their application in aqueous phase corrosion inhibition is often restricted. Polymeric surfactants, a unique class of corrosion inhibitors, hold the potential to eradicate the challenges associated with using surfactants in corrosion inhibition. They strongly bond with the metallic surface and offer superior CIP because of their macromolecular polymeric structure and abundance of polar functional groups. In contrast to conventional polymeric corrosion inhibitors, the inclusion of polar functional groups also aids in their solubilization in the majority of popular industry-based electrolytes. Some of the major functional groups present in polymeric surfactants used in corrosion mitigation include O (ether), glycidyl (cyclic ether), -CONH2 (amide), -COOR (ester), -SO3H (sulfonic acid), -COOH (carboxyl), -NH2 (amino), - + NR3/- + NHR2/- + NH2R/- + NH3 (quaternary ammonium), -OH (hydroxyl), -CH2OH (hydroxymethyl), etc. The current viewpoint offers state-of-the-art information on polymer surfactants as newly developing ideal alternatives for conventional corrosion inhibitors. The industrial scale-up, colloidal, coordination, adsorption properties, and structural requirements of polymer surfactants have also been established based on the knowledge obtained from the literature. Finally, the challenges, drawbacks, and potential benefits of using polymer surfactants have also been discussed.

Commercialization of Ionic Liquids in Pursuit of Green Chemistry: Must we Each Become an Entrepreneur?

There will be common challenges to scaling-up any ionic liquids separations technologies which require very large volumes of ionic liquid. Some of these challenges are illustrated in this personal account which chronicles the extraction of chitin from shrimp shell from discovery to current commercialization efforts. The road being taken from discovery in an academic laboratory, through attempts to navigate the scaling-up to commercial scale using the vehicle of a faculty startup company is rewarding, but fraught with roadblocks, detours, and unexpected challenges. The differences in 'technically feasible' and 'commercially viable' are not always evident from the beginning of the journey, however, one wonders what achievements we miss as a Society because it was assumed to not be commercially viable.

Chitosan-Based Films Containing Rutin for Potential Cosmetic Applications

Chitosan is a polysaccharide with film-forming properties. Such properties are widely used for the preparation of beauty masks and wound-healing materials. In this work, chitosan-based films containing hyaluronic acid and rutin have been researched for potential cosmetic applications. Rutin was added to a chitosan solution in lactic acid, and then thin films were fabricated. The structure of the films was studied using FTIR spectroscopy. Surface properties were studied using an AFM microscope. The release of rutin from chitosan-based film was researched by the HPLC method. The properties of the skin, such as elasticity and moisturization, were studied using the Aramo TS 2 apparatus. It was found that the addition of rutin did not have an influence on the chitosan structure but affected its thermal stability. The roughness of the films was bigger after the addition of rutin to chitosan-based films. Skin elasticity and skin moisturization were somewhat improved after the topical application of the proposed chitosan-rutin mask. The maximum release of rutin was found after 20 min at pH 5.5, related to the pH of normal human skin. The average percentage of release from chitosan-based film containing hyaluronic acid was smaller than from chitosan-based films.

Biocompatible Chitosan Films Containing Acetic Acid Manifested Potent Antiviral Activity against Enveloped and Non-Enveloped Viruses

Chitosan films were prepared by solvent casting using an acetic acid-based solution. The films that were developed contained 15.49% of acetic acid solution (10% v/v) and showed biocompatibility in vitro in human keratinocyte HaCaT cells and potent antiviral activity against both enveloped and non-enveloped viruses. The results showed up to 99.98% and 99.92% viral inactivation against the phi 6 enveloped bacteriophage and MS2 non-enveloped bacteriophage, respectively, suggesting that this chitosan/acetic acid film is a promising material for biomedical applications that require biodegradable broad-spectrum antiviral materials.

Chitin nanofiber-coated biodegradable polymer microparticles via one-pot aqueous process

Tailoring the surface of biodegradable microparticles is important for various applications in the fields of cosmetics, biotechnology, and drug delivery. Chitin nanofibers (ChNFs) are one of the promising materials for surface tailoring owing to its functionality, such as biocompatibility and antibiotic properties. Here, we show biodegradable polymer microparticles densely coated with ChNFs. Cellulose acetate (CA) was used as the core material in this study, and ChNF coating was successfully carried out via a one-pot aqueous process. The average particle size of the ChNF-coated CA microparticles was approximately 6 μm, and the coating procedure had little effect on the size or shape of the original CA microparticles. The ChNF-coated CA microparticles comprised 0.2-0.4 wt% of the thin surface ChNF layers. Owing to the surface cationic ChNFs, the ζ-potential value of the ChNF-coated microparticles was +27.4 mV. The surface ChNF layer efficiently adsorbed anionic dye molecules, and repeatable adsorption/desorption behavior was exhibited owing to the coating stability of the surface ChNFs. The ChNF coating in this study was a facile aqueous process and was applicable to CA-based materials of various sizes and shapes. This versatility will open new possibilities for future biodegradable polymer materials that satisfy the increasing demand for sustainable development.

Effective assessment of biopolymer-based multifunctional sorbents for the remediation of environmentally hazardous contaminants from aqueous solutions

Persistent contaminants in wastewater effluent pose a significant threat to aquatic life and are one of the most significant environmental concerns of our time. Although there are a variety of traditional methods available in wastewater treatment, including adsorption, coagulation, flocculation, ion exchange, membrane filtration, co-precipitation and solvent extraction, none of these have been found to be significantly cost-effective in removing toxic pollutants from the water environment. The upfront costs of these treatment methods are extremely high, and they require the use of harmful synthetic chemicals. For this reason, the development of new technologies for the treatment and recycling of wastewater is an absolute necessity. Our way of life can be made more sustainable by the synthesis of adsorbents based on biomass, making the process less harmful to the environment. Biopolymers offer a sustainable alternative to synthetic polymers, which are manufactured by joining monomer units through covalent bonding. This review presents a detailed classification of biopolymers such as pectin, alginate, chitosan, lignin, cellulose, chitin, carrageen, certain proteins, and other microbial biomass compounds and composites, with a focus on their sources, methods of synthesis, and prospective applications in wastewater treatment. A concise summary of the extensive body of knowledge on the fate of biopolymers after adsorption is also provided. Finally, consideration is given to open questions about future developments leading to environmentally friendly and economically beneficial applications of biopolymers.

High-tensile chitin films regenerated from cryogenic aqueous phosphoric acid

The abuse of non-renewable fossil resources and the resulting plastic pollution have posed a great burden on the environment. Fortunately, renewable bio-macromolecules have shown great potential to replace synthetic plastics in fields ranging from biomedical applications, and energy storage to flexible electronics. However, the potential of recalcitrant polysaccharides, such as chitin, in the above-mentioned fields have not been fully exploited because of its poor processability, which is ultimately due to the lack of suitable, economical, and environmentally friendly solvent for it. Herein, we demonstrate an efficient and stable strategy for the fabrication of high-strength chitin films from concentrated chitin solutions in cryogenic 85 wt% aqueous phosphoric acid (aq. H₃PO₄). The regeneration conditions, including the nature of the coagulation bath and its temperature are important variables affecting the reassembly of chitin molecules and hence the structure and micromorphology of the films. Uniaxial orientation of the chitin molecules by applying tension to the RCh hydrogels further endows the films with enhanced mechanical properties of up to 235 MPa and 6.7 GPa in tensile strength and Young's modulus, respectively.

Photothermal Superhydrophobic Chitosan-Based Cotton Fabric for Rapid Deicing and Oil/Water Separation

Superhydrophobic cotton fabrics have a lot of potential for use in practical settings. The majority of superhydrophobic cotton fabrics, however, only serve one purpose and are made from fluoride or silane chemicals. Therefore, it remains a challenge to develop multifunctional superhydrophobic cotton fabrics using environmentally friendly raw materials. In this study, chitosan (CS), amino carbon nanotubes (ACNTs), and octadecylamine (ODA) were used as raw materials to create CS-ACNTs-ODA photothermal superhydrophobic cotton fabrics. The cotton fabric that was created showed a remarkable superhydrophobic property with a water contact angle of 160.3°. The surface temperature of CS-ACNTs-ODA cotton fabric can rise by up to 70 °C when exposed to simulated sunlight, demonstrating the fabric's remarkable photothermal capabilities. Additionally, the coated cotton fabric is capable of quick deicing. Ice particles (10 μL) melted and began to roll down in 180 s under the light of "1 sun". The cotton fabric exhibits good durability and adaptability in terms of mechanical qualities and washing tests. Moreover, the CS-ACNTs-ODA cotton fabric displays a separation efficacy of more than 91% when used to treat various oil and water mixtures. We also impregnate the coating on polyurethane sponges, which can quickly absorb and separate oil and water mixtures.

Exploring the Blends' Miscibility of a Novel Chitosan Derivative with Enhanced Antioxidant Properties; Prospects for 3D Printing Biomedical Applications

Chitosan is a polysaccharide vastly examined in polymer science for its unique structure. In the present study, CS was derivatized with 2-methoxy-4vinylphenol (MVP) in four different ratios through a free radical reaction. The CS-MVP derivatives were characterized through FTIR, 1H-NMR, XRD, swelling, and solubility measurements. Owing to the enhanced antioxidant character of the MVP monomer, the antioxidant activity of the CS-MVP derivatives was assessed. In the optimum CS-MVP ratio, blends between CS and CS-MVP were prepared in ratios of 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, and 10:90 w/w, and their miscibility was examined by scanning electron microscopy (SEM) and viscosity measurements. In the optimum ratios, highly concentrated inks were prepared, and their viscosity measurements revealed the successful formation of highly viscous gels with shear thinning behavior. These inks could be appropriate candidates for biomedical and drug delivery applications.

Development of chitosan-based hydrogels for healthcare: A review

Chitosan-based hydrogels (CSH) are promising materials for healthcare. Based on the relationship among structure, property and application, researches reported within last decade are chosen to elucidate the developing approaches and potential applications of target CSH. The applications of CSH are classified into the conventional biomedical fields, such as drug controlled release, tissue repair and monitoring, and the essential ones including food safety, water purification and air cleaning. The approaches focused on in this article are the reversible chemical and physical ones. Apart from describing the current status of the development, suggestions are presented as well.

Oral insulin delivery: Barriers, strategies, and formulation approaches: A comprehensive review

Diabetes Mellitus is characterized by a hyperglycemic condition which can either be caused by the destruction of the beta cells or by the resistance developed against insulin in the cells. Insulin is a peptide hormone that regulates the metabolism of carbohydrates, proteins, and fats. Type 1 Diabetes Mellitus needs the use of Insulin for efficient management. However invasive methods of administration may lead to reduced adherence by the patients. Hence there is a need for a non-invasive method of administration. Oral Insulin has several merits over the conventional method including patient compliance, and reduced cost, and it also mimics endogenous insulin and hence reaches the liver by the portal vein at a higher concentration and thereby showing improved efficiency. However oral Insulin must pass through several barriers in the gastrointestinal tract. Some strategies that could be utilized to bypass these barriers include the use of permeation enhancers, absorption enhancers, use of suitable polymers, use of suitable carriers, and other agents. Several formulation types have been explored for the oral delivery of Insulin like hydrogels, capsules, tablets, and patches which have been described briefly by the article. A lot of attempts have been made for developing oral insulin delivery however none of them have been commercialized due to numerous shortcomings. Currently, there are several formulations from the companies that are still in the clinical phase, the success or failure of some is yet to be seen in the future.

How to Develop Drug Delivery System Based on Carbohydrate Nanoparticles Targeted to Brain Tumors

Brain tumors are the most difficult to treat, not only because of the variety of their forms and the small number of effective chemotherapeutic agents capable of suppressing tumor cells, but also limited by poor drug transport across the blood-brain barrier (BBB). Nanoparticles are promising drug delivery solutions promoted by the expansion of nanotechnology, emerging in the creation and practical use of materials in the range from 1 to 500 nm. Carbohydrate-based nanoparticles is a unique platform for active molecular transport and targeted drug delivery, providing biocompatibility, biodegradability, and a reduction in toxic side effects. However, the design and fabrication of biopolymer colloidal nanomaterials have been and remain highly challenging to date. Our review is devoted to the description of carbohydrate nanoparticle synthesis and modification, with a brief overview of the biological and promising clinical outcomes. We also expect this manuscript to highlight the great potential of carbohydrate nanocarriers for drug delivery and targeted treatment of gliomas of various grades and glioblastomas, as the most aggressive of brain tumors.

Chitosan oligomers (COS) trigger a coordinated biochemical response of lemongrass (Cymbopogon flexuosus) plants to palliate salinity-induced oxidative stress

Plant susceptibility to salt depends on several factors from its genetic makeup to modifiable physiological and biochemical status. We used lemongrass (Cymbopogon flexuosus) plants as a relevant medicinal and aromatic cash crop to assess the potential benefits of chitosan oligomers (COS) on plant growth and essential oil productivity during salinity stress (160 and 240 mM NaCl). Five foliar sprays of 120 mg L^-1 of COS were applied weekly. Several aspects of photosynthesis, gas exchange, cellular defence, and essential oil productivity of lemongrass were traced. The obtained data indicated that 120 mg L^-1 COS alleviated photosynthetic constraints and raised the enzymatic antioxidant defence including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities that minimised salt-induced oxidative damage. Further, stomatal conductance (g_s) and photosynthetic CO₂ assimilation (A) were improved to support overall plant development. The same treatment increased geraniol dehydrogenase (GeDH) activity and lemongrass essential oil production. COS-induced salt resilience suggests that COS could become a useful biotechnological tool in reclaiming saline soil for improved crop productivity, especially when such soil is unfit for leading food crops. Considering its additional economic value in the essential oil industry, we propose COS-treated lemongrass as an excellent alternative crop for saline lands.

Hydrogelation from Self-Assembled and Scaled-Down Chitin Nanofibers by the Modification of Highly Polar Substituents

Chitin nanofibers (ChNFs) with a bundle structure were fabricated via regenerative self-assembly at the nanoscale from a chitin ion gel with an ionic liquid using methanol. Furthermore, the bundles were disentangled by partial deacetylation under alkaline conditions, followed by cationization and electrostatic repulsion in aqueous acetic acid to obtain thinner nanofibers called scaled-down ChNFs. This review presents a method for hydrogelation from self-assembled and scaled-down ChNFs by modifying the highly polar substituents on ChNFs. The modification was carried out by the reaction of amino groups on ChNFs, which were generated by partial deacetylation, with reactive substituent candidates such as poly(2-oxazoline)s with electrophilic living propagating ends and mono- and oligosaccharides with hemiacetallic reducing ends. The substituents contributed to the formation of network structures from ChNFs in highly polar dispersed media, such as water, to produce hydrogels. Moreover, after the modification of the maltooligosaccharide primers on ChNFs, glucan phosphorylase-catalyzed enzymatic polymerization was performed from the primer chain ends to elongate the amylosic graft chains on ChNFs. The amylosic graft chains formed double helices between ChNFs, which acted as physical crosslinking points to construct network structures, giving rise to hydrogels.

An all-biopolymer self-assembling hydrogel film consisting of chitosan and carboxymethyl guar gum: A novel bio-based composite adsorbent for Cu2+ adsorption from aqueous solution

A novel bio-based composite adsorbent, all biopolymer self-assembled hydrogel film has been prepared by eco-friendly amalgamating chitosan (CS) and carboxymethyl guar gum (CMGG) biopolymers in water without needing small molecules for cross-linking. Various analysis demonstrated the electrostatic interactions and hydrogen bondings within the network structure are responsible for gelling, crosslinking, and forming a 3D structure. Various experimental parameters were optimized to evaluate the CS/CMGG's potential for removing Cu²⁺ ions from aqueous solution, including pH, dosage, Cu(II) initial concentration, contact time, and temperature. The pseudo-second-order kinetic and Langmuir isotherm models are highly correlated with the kinetic and equilibrium isotherm data, respectively. Using the Langmuir isotherm model for an initial metal concentration of 50 mg/L at pH 6.0 and 25 °C, the maximum adsorption of Cu(II) was calculated to be 155.51 mg/g. A combination of adsorption-complexation and ion exchange must be involved in Cu(II) adsorption on the CS/CMGG. Five cycles of the loaded CS/CMGG hydrogel regeneration and reuse were successfully achieved without an appreciable difference in Cu(II) removal percentage. Thermodynamic analysis indicated that copper adsorption occurred spontaneously (ΔG°: -2.85 J/mol, 298 K) and exothermically (ΔH°: -27.58 J/mol). A reusable bio-adsorbent for removing heavy metal ions was developed that is eco-friendly, sustainable, and efficient.

Highly stretchable, tough and conductive chitin nanofiber composite hydrogel as a wearable sensor

To meet the requirements of eco-friendly and sustainability in the 21st century, hydrogels based on biopolymer with conductivity and stretchable property have attained increasing attention for strain sensor. However, the as-prepared of hydrogel sensor with excellent mechanical property and high strain sensitivity is still a challenge. In this study, chitin nanofiber (ChNF) reinforced composite hydrogels of PACF are fabricated via a facile one-pot method. The obtained PACF composite hydrogel exhibits good transparency (80.6 % at 800 nm)and excellent mechanical properties (tensile strength, 261.2 kPa; tensile strain as high as 550.3 %). Moreover, the composite hydrogels also demonstrate excellent anti-compression performance. The composite hydrogels own good conductivity (1.20 S/m) and strain sensitivity. Most importantly, the hydrogel can be assembled as a strain/pressure sensor for detecting large-scale and small-scale human motion. Therefore, flexible conductive hydrogel strain sensors will have broad application prospects in artificial intelligence, electronic skin, and personal health.

Effects of the Degree of Deacetylation on the Single-Molecule Mechanics of Chitosans

Chitosan is one of the most prevalent biomass materials, and its physicochemical and biological characteristics, such as solubility, crystallinity, flocculation ability, biodegradability, and amino-related chemical processes, are directly connected to the degree of deacetylation (DD). However, the specifics about the effects of the DD on the characteristics of chitosan are still unclear up to now. In this work, atomic force microscopy-based single-molecule force spectroscopy was used to study the role of the DD in the single-molecule mechanics of chitosan. Even though the DD varies largely (17% ≤ DD ≤ 95%), the experimental results demonstrate that the chitosans exhibit the same natural (in nonane) and backbone (in dimethyl sulfoxide (DMSO)) single-chain elasticity. This suggests that chitosans have the same intra-chain hydrogen bond (H-bond) state in nonane and to which these H-bonds can be eliminated in DMSO. However, when the experiments are carried out in ethylene glycol (EG) and water, the single-chain mechanics are increased with the increases of the DD. The energy consumed to stretch chitosans in water is larger than that in EG, indicating that amino can form a strong interaction with water and induce the formation of the binding water around the sugar rings. The strong interaction between water and amino may be the key factor for the well solubility and chemical activity of chitosan. The results of this work are anticipated to provide fresh light on the significant role played by the DD and water in the structures and functions of chitosan at the single molecular level.

Development of a novel chitosan-based two-photon fluorescent nanoprobe with enhanced stability for the specific detection of endogenous H2O2

Hydrogen peroxide (H₂O₂) acts as an important reactive oxygen species (ROS) and maintains the redox equilibrium in organisms. Imbalance of H₂O₂ concentration is associated with the development of many diseases. Traditional small molecular based fluorescent probes often show drawbacks of cytotoxicity and easily metabolic clearance. Herein, a chitosan-based two-photon fluorescent nanoprobe (DC-BI) was constructed and applied for H₂O₂ detection in live organisms. DC-BI was composed by chitosan nanoparticles and a two-photon fluorophore of naphthalimide analogues (BI) with H₂O₂-responsive property. The structure of DC-BI was characterized by NMR, FTIR, XPS, XRD, DLS and MLS analyses. As study shown, the nanoprobe DC-BI exhibited improved distribution stability and smaller cytotoxicity. In the presence of H₂O₂, both the absorption and emission spectra show dramatic changes, the fluorescence intensity at 580 nm obviously enhanced. Furthermore, fluorescence imaging results indicate that DC-BI is capable of imaging endogenous H₂O₂ in cells and zebrafish. The design and development of chitosan-based nanoprobe DC-BI has provided a general example of nanoprobe construction with excellent distribution stability, two-photon property, and biocompatibility.

Strain-induced 3D-oriented crystallites in natural rubber/chitin nanofiber composites

Natural rubber (NR) composites containing bio-based chitin nanofibers (ChNFs) exhibit a wide range of mechanical properties - from rubber to plastic behavior - with increasing chitin contents. A constrained 3-dimensional network can be formed by mixing natural rubber latex and a modified zwitterionic rigid chitin counterpart. By inclusion of highly anisotropic chitin nanofibers (30 wt%), strain-induced NR crystallization occurs at a much lower strain of 50%. More intriguingly, 2D-WAXD results reveal that the strain-induced crystallization of NR/ChNFs composites show 3-dimensionally oriented crystallite formation behaving similar to "3D-single crystals orientation" when the content of ChNFs is over 5 wt%. It is suggested that not only c-axis (NR chains) orients along the stretching direction, but also the a- and b-axes deliberately arrange along the normal direction and transverse direction, respectively. Structure and morphology in 3-dimensional spaces after strain-induced crystallization of the NR/ChNFs30 composite are investigated in detail. Therefore, this study might pave a new way to enhance mechanical properties by incorporation of ChNFs, obtaining 3-dimensionally oriented crystallites of novel multifunctional NR/ChNFs composite with shape memory ability.

Temporary Anti-Corrosive Double Layer on Zinc Substrate Based on Chitosan Hydrogel and Epoxy Resin

In practice, metal structures are frequently transported or stored before being used. Even in such circumstances, the corrosion process caused by environmental factors (moisture, salty air, etc.) can occur quite easily. To avoid this, metal surfaces can be protected with temporary coatings. The objective of this research was to develop coatings that exhibit effective protective characteristics while also allowing for easy removal, if required. Novel, chitosan/epoxy double layers were prepared on zinc by dip-coating to obtain temporary tailor-made and peelable-on-demand, anti-corrosive coatings. Chitosan hydrogel fulfills the role of a primer that acts as an intermediary between the zinc substrate and the epoxy film to obtain better adhesion and specialization. The resulting coatings were characterized using electrochemical impedance spectroscopy, contact angle measurements, Raman spectroscopy, and scanning electron microscopy. The impedance of the bare zinc was increased by three orders of magnitude when the protective coatings were applied, proving efficient anti-corrosive protection. The chitosan sublayer improved the adhesion of the protective epoxy coating. The structural integrity and absolute impedance of the protective layers were conserved in both basic and neutral environments. However, after fulfilling its lifespan, the chitosan/epoxy double-layered coating could be removed after treatment with a mild acid without damaging the substrate. This was because of the hydrophilic properties of the epoxy layer, as well as the tendency of chitosan to swell in acidic conditions.

Chitosan: A Potential Biopolymer in Drug Delivery and Biomedical Applications

Chitosan, a biocompatible and biodegradable polysaccharide derived from chitin, has surfaced as a material of promise for drug delivery and biomedical applications. Different chitin and chitosan extraction techniques can produce materials with unique properties, which can be further modified to enhance their bioactivities. Chitosan-based drug delivery systems have been developed for various routes of administration, including oral, ophthalmic, transdermal, nasal, and vaginal, allowing for targeted and sustained release of drugs. Additionally, chitosan has been used in numerous biomedical applications, such as bone regeneration, cartilage tissue regeneration, cardiac tissue regeneration, corneal regeneration, periodontal tissue regeneration, and wound healing. Moreover, chitosan has also been utilized in gene delivery, bioimaging, vaccination, and cosmeceutical applications. Modified chitosan derivatives have been developed to improve their biocompatibility and enhance their properties, resulting in innovative materials with promising potentials in various biomedical applications. This article summarizes the recent findings on chitosan and its application in drug delivery and biomedical science.

A Chitosan-Based Flocculation Method for Efficient Recovery of High-Purity B-Phycoerythrin from a Low Concentration of Phycobilin in Wastewater

Increasing the yield and purity of B-phycoerythrin (B-PE) can improve the economic state of microalgae industrial processing. One method of cost reduction involves the recovery of remaining B-PE from wastewater. In this study, we developed a chitosan (CS)-based flocculation technique for the efficient recovery of B-PE from a low concentration of phycobilin in wastewater. We investigated the effects of the molecular weight of chitosan, B-PE/CS mass ratio, and solution pH on the flocculation efficiency of CS and the effects of phosphate buffer concentration and pH on the recovery rate of B-PE. The maximum flocculation efficiency of CS, recovery rate, and purity index of B-PE were 97.19% ± 0.59%, 72.07% ± 1.37%, and 3.20 ± 0.025 (drug grade), respectively. The structural stability and activity of B-PE were maintained during the recovery process. Economic evaluation revealed that our CS-based flocculation method is more economical than the ammonium sulfate precipitation method is. Furthermore, the bridging effect and electrostatic interaction play important roles in B-PE/CS complex flocculation process. Hence, our study provides an efficient and economical method to recover high-purity B-PE from a low concentration of phycobilin in wastewater, which promoted the application of B-PE as a natural pigment protein in food and chemical applications.

Water-resistant free-standing DNA-complexed films with antioxidant and H2O2-responsive activity

Water-insoluble DNA complexes are suitable for producing free-standing DNA films due to their low water sensitivity, which prevents their rapid degradation in aqueous environments. Here, we proposed two types of free-standing films that exhibit low dissolution rates in water: low molecular weight chitosan (LCS)-DNA films and phosphatidylcholine (PC)-cetyltrimethylammonium (CTMA)-DNA films. The structure and binding characteristics of the LCS-DNA and PC-CTMA-DNA complexes were investigated with UV-Vis spectroscopy and via the fluorescent characteristics of daunorubicin bound to them. A simple drop-casting method was then adopted for both complexes to fabricate free-standing films. An increase in antioxidant activity and water-resistance of the LCS-DNA DNA film was observed when the molar ratio of LCS to DNA was increased, but the dissolution rate of the LCS-DNA film was also dependent on the ionic strength of the dissolving solution. Fourteen days were required to dissolve the LCS-DNA film in deionized water, whereas immediate dissolution was observed in 1× phosphate-buffered saline (PBS). Deformation of the PC-CTMA-DNA film was accelerated by H₂O₂, such that the PC-CTMA-DNA film was degraded after 21 days of immersion in 1× PBS with H₂O₂. Due to the low dissolution rate in water and antioxidant activity, the free-standing LCS-DNA film should be able to store and protect embedded clinical materials, such as proteins and intercalating drugs, from moisture and enable localized delivery of treatments to designated sites. Also, the free-standing PC-CTMA-DNA film could be a biocompatible candidate for use as a membrane or sensor for detecting the levels of reactive oxygen species.

Influence of Ionic Strength and Specific Ion Effects on Polyelectrolyte Multilayer Films with pH-Responsive Behavior

Layer-by-layer assembled multilayer films have shown great potential for different applications owing to their responsive behavior. Herein, we systematically investigated the effects of composition, salt concentration, and ion specificity on the pH responsiveness of covalently crosslinked chitosan and alginate dialdehyde multilayer films. The changes in film swelling were measured using ellipsometry from low (0.01 mM) to high (3 M) salt (NaCl or NaSCN) concentrations at pH 3, 6, and 9. The swelling responses to increasing ionic strength matched the swelling responses observed for polyzwitterionic and weak monocomponent polyelectrolyte films and depended on the multilayer composition, pH, and ion specificity. Finally, we used the ellipsometric data to demonstrate that the pH responsiveness of such multilayer films, as measured using a quartz crystal microbalance with dissipation monitoring, strongly depends on the ionic condition under which the responses were measured. We thus show that erroneous conclusions about the pH responsiveness of polyelectrolyte multilayer films can be easily obtained if the ionic environment of the application does not closely resemble the ionic condition under which the pH responsiveness is tested.

Cleanup of oils and organic solvents from contaminated water by biomass-based aerogel with adjustable compression elasticity

Leakage of oils and organic solvents poses a significant threat to aquatic environments. Here, low-temperature carbonized aerogels with highly porous and anisotropic structures obtained only from biomass-derived materials were proposed to absorb polymorphic oils from contaminated water. Specifically, carbonized aerogels prepared at temperatures of 300 °C and 350 °C exhibited ultra-high absorption capacities (40‒125 g g^-1) and oil-water separation efficiencies (> 99%) even in harsh environments, which were attributed to their exceptional properties, including high porosity, abundant macropores, excellent thermal stability, and hydrophobicity. Through citric acid crosslinking and low-temperature carbonization, the aerogels exhibited superior compression elasticity and could be cyclically utilized through simple extrusion while realizing the recovery of oils. Moreover, the outstanding photothermal conversion properties obtained through carbonization contributed to the high temperature and fluidity of the oils surrounding the aerogels, which is crucial for improving the absorption performance of high-viscosity oils. Such absorbent materials are used to separate crude oil from oil-water mixtures, which can achieve maximum absorption of 56 g g^-1 and increase the absorption rate (from several days to 10 min) in a low-temperature (4 °C) seawater environment.

Double-Network Chitosan-Based Hydrogels with Improved Mechanical, Conductive, Antimicrobial, and Antibiofouling Properties

In recent years, the antimicrobial activity of chitosan-based hydrogels has been at the forefront of research in wound healing and the prevention of medical device contamination. Anti-infective therapy is a serious challenge given the increasing prevalence of bacterial resistance to antibiotics as well as their ability to form biofilms. Unfortunately, hydrogel resistance and biocompatibility do not always meet the demands of biomedical applications. As a result, the development of double-network hydrogels could be a solution to these issues. This review discusses the most recent techniques for creating double-network chitosan-based hydrogels with improved structural and functional properties. The applications of these hydrogels are also discussed in terms of tissue recovery after injuries, wound infection prevention, and biofouling of medical devices and surfaces for pharmaceutical and medical applications.