pH Effects on solubility, zeta potential, and correlation between antibacterial activity and molecular weight of chitosan

Synthesis and antibacterial analysis of C-6 amino-functionalised chitosan derivatives

Synthesis of 6-O-(3-alkylamino-2-hydroxypropyl) derivatives of chitosan was achieved using a four-step strategy of N-protection, O-epoxide addition, epoxide ring opening using an amine and N-deprotection. Benzaldehyde and phthalic anhydride were used for the N-protection step, producing N-benzylidene and N-phthaloyl protected derivatives, respectively, resulting in two corresponding final 6-O-(3-alkylamino-2-hydroxypropyl) derivative series, BD1-BD6 and PD1-PD14. All the compounds were characterized using FTIR, XPS and PXRD studies and tested for antibacterial efficacy. The phthalimide protection strategy was found to be easier to apply and effective in terms of the synthetic process and improvement in antibacterial activity. Amongst the newly synthesized compounds, PD13 (6-O-(3-(2-(N,N-dimethylamino)ethylamino)-2-hydroxypropyl)chitosan) was the most active with eight times greater activity compared to the unmodified chitosan and, PD7 6-O-(3-(3-(N-(3-aminopropyl)propane-1,3-diamino)propylamino)-2-hydroxypropyl)chitosan) having a four-fold activity than chitosan, was found to be the second most potent derivative. This work has produced new chitosan derivatives those are more potent than chitosan itself and show promise in antimicrobial applications.

Molar-mass-dependent antibacterial activity of cationic dextran derivatives against resistant nosocomial pathogens

The rise of various multidrug-resistant bacteria has created a need for new biocompatible and biodegradable antibacterial compounds. Cationic polysaccharides are promising candidates for this role. Therefore, cationic derivatives of commercial dextrans with molar masses of 11 kDa, 76 kDa, 411 kDa, and 1500-2500 kDa and various degrees of substitution (DS_Q 0.34-0.52) were prepared and their antimicrobial properties against four gram-negative nosocomial bacteria were tested. As expected, a higher DS_Q led to higher efficiency. The best antimicrobial properties were found for derivatives of 411 kDa, followed by 76 kDa and 1500-2000 kDa dextrans. This indicates that there is a certain optimum molar mass with the best antimicrobial properties. However, as molar mass increased, the biocompatibility of cationic dextran steadily decreased, with increased hemagglutination and toxicity being seen for human cells. The derivatives of 76 kDa dextran with higher DS_Q (0.40-0.52) were the best antimicrobial agents suitable for further clinical testing.

Structural characterization, stability, and cytocompatibility study of chitosan BaTiO3@ZnO:Er heterostructures

New imaging agents are required in cancer diagnosis to enhance the diagnostic accuracy, classification, and therapeutic management of tumors. Nanomaterials have emerged as a promising alternative to developing new nanostructures with imaging applications. In this study, a heterostructure based on barium titanate (BT), zinc oxide (ZnO), and erbium (Er) was prepared and coated with Chitosan (CS) to investigate their stability and compatibility with biological systems. The structure, particle morphology, luminescence properties, stability, and cytotoxicity of different nanoparticles (NPs) were assessed. The results demonstrated the formation of a [BT@ZnO:Er]-CS heterostructure, which is consistent with the relative intensities and positions of peaks in the X-ray diffraction (XRD) with an average crystallite size of ~76 nm. The electrokinetic measurement results indicate that the coated NPs are the most stable and have an average size close to 200 nm when the pH is between 3 and 5. Finally, we presented a cytotoxicity study of naked and CS-coated NPs. The results indicate that naked NPs exhibit varying cellular toxicity, as indicated by decreased cell viability, morphological changes, and an increase in an apoptotic marker. The CS-coated NPs prevented the cytotoxic effect of the naked NPs, demonstrating the significance of CS as a stabilizing agent.

Synthesis and characterization of thiazolium chitosan derivative with enhanced antimicrobial properties and its use as component of chitosan based films

In this work, chemical modification of chitosan using cationic thiazolium groups was investigated with the aim to improve water solubility and antimicrobial properties of chitosan. Enzymatic synthesis and ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) chemistry were employed to synthesize and attach to chitosan through the amine groups the molecule bearing thiazolium moieties, quaternized 4-(2-(4-methylthiazol-5-yl) ethoxy)-4-oxobutanoic acid (MTBAQ). On the basis of Fourier transform infrared spectroscopy (FTIR), elemental analysis and solid state nuclear magnetic resonance (ssNMR), around 95 % of the available amine groups of chitosan (of 25 % degree of acetylation) reacted. The resulting derivative was water soluble at physiological pH and exhibit excellent antimicrobial activity against Listeria innocua, Staphylococcus epidermidis, Staphylococcus aureus and Methicillin Resistant S. aureus Gram-positive bacteria (MIC = 8-32 μg/ mL), whereas its efficiency decreases against fungi Candida albicans and Eschericia coli Gram-negative bacterium. Subsequently, the thiazolium chitosan derivative was employed as antimicrobial component (up to 7 wt%) of chitosan/glycerol based films. The incorporation of the chitosan derivative does not modify significantly the characteristics of the film in terms of thermal and mechanical properties, while enhances considerably the antimicrobial activity.

Complexation of oligochitosan with sodium caseinate in alkalescent and weakly acidic media

Сomplexation of oligochitosan (OCHI) having the degree of acetylation (DA 26 %) with sodium caseinate (SC) at pH 5.8 and 7.2 is described and compared with the complexation of OCHI (DA 2 %) at pH 5.8. In the alkalescent medium, the complexation of OCHI (DA 26 %) is weaker and dualistic depending on SC concentration in the system. In the diluted alkalescent system, the formation of only soluble complexes is observed at OCHI/SC ratio ≤0.9. In the semi diluted one, the complexation results in the formation of insoluble complexes those composition changes symbatically with the OCHI/SC ratio in the system. At pH 5.8, OCHI/SC ratio in insoluble complexes remains the same regardless of OCHI/SC ratio in the solution. At pH 5.8, the electrostatic complexation weakens with an increase in DA and is completely suppressed at a high ionic strength. These results can be promising for construction of biodegradable protein/chitosan drug delivery systems.

Development of Computational In Silico Model for Nano Lipid Carrier Formulation of Curcumin

The oral delivery system is very important and plays a significant role in increasing the solubility of drugs, which eventually will increase their absorption by the digestive system and enhance the drug bioactivity. This study was conducted to synthesize a novel curcumin nano lipid carrier (NLC) and use it as a drug carrier with the help of computational molecular docking to investigate its solubility in different solid and liquid lipids to choose the optimum lipids candidate for the NLCs formulation and avoid the ordinary methods that consume more time, materials, cost, and efforts during laboratory experiments. The antiviral activity of the formed curcumin-NLC against SARS-CoV-2 (COVID-19) was assessed through a molecular docking study of curcumin's affinity towards the host cell receptors. The novel curcumin drug carrier was synthesized as NLC using a hot and high-pressure homogenization method. Twenty different compositions of the drug carrier (curcumin nano lipid) were synthesized and characterized using different physicochemical techniques such as UV-Vis, FTIR, DSC, XRD, particle size, the zeta potential, and AFM. The in vitro and ex vivo studies were also conducted to test the solubility and the permeability of the 20 curcumin-NLC formulations. The NLC as a drug carrier shows an enormous enhancement in the solubility and permeability of the drug.

Nanochitin and Nanochitosan: Chitin Nanostructure Engineering with Multiscale Properties for Biomedical and Environmental Applications

Nanochitin and nanochitosan (with random-copolymer-based multiscale architectures of glucosamine and N-acetylglucosamine units) have recently attracted immense attention for the development of green, sustainable, and advanced functional materials. Nanochitin and nanochitosan are multiscale materials from small oligomers, rod-shaped nanocrystals, longer nanofibers, to hierarchical assemblies of nanofibers. Various physical properties of chitin and chitosan depend on their molecular- and nanostructures; translational research has utilized them for a wide range of applications (biomedical, industrial, environmental, and so on). Instead of reviewing the entire extensive literature on chitin and chitosan, here, recent developments in multiscale-dependent material properties and their applications are highlighted; immune, medical, reinforcing, adhesive, green electrochemical materials, biological scaffolds, and sustainable food packaging are discussed considering the size, shape, and assembly of chitin nanostructures. In summary, new perspectives for the development of sustainable advanced functional materials based on nanochitin and nanochitosan by understanding and engineering their multiscale properties are described.

Chitin and its derivatives: Functional biopolymers for developing bioproducts for sustainable agriculture-A reality?

Chitinous materials (chitin and its derivatives) are obtained from renewable sources, mainly shellfish waste, having a great potential for the development of bioproducts as alternatives to synthetic agrochemicals. Recent studies have provided evidence that the use of these biopolymers can help control postharvest diseases, increase the content of nutrients available to plants, and elicit positive metabolic changes that lead to higher plant resistance against pathogens. However, agrochemicals are still widely and intensively used in agriculture. This perspective addresses the gap in knowledge and innovation to make bioproducts based on chitinous materials more competitive in the market. It also provides the readers with background to understand why these products are scarcely used and the aspects that need to be considered to increase their use. Finally, information on the development and commercialization of agricultural bioproducts containing chitin or its derivatives in the Chilean market is also provided.

Design and optimization of an innovative lanthanum/chitosan bead for efficient phosphate removal and study of process performance and mechanisms

Presence of excessive phosphorus in surface waters is the main cause for eutrophication. In this study, a lanthanum/chitosan (La/CS) bead was prepared so as to provide a cost-effective solution to the problem. The optimization of bead for the treatment was conducted, leading to the optimal condition: 30 wt% La/CS bead at a dosage of 30 g L^-1 (wet weight). A higher phosphate removal around 90% was obtained in pH 4.0-10.0. Most of uptake occurred in the first 2 h and the equilibrium was reached in about 6 h. Coexisting ions of Cl^-, [Formula: see text] , [Formula: see text] , and [Formula: see text] had negligible effects on the treatment, while the presence of F^- reduced the uptake by 10.39%. The maximum adsorption capacity of 261.1 mg-PO₄·g^-1 (dried weight) at pH 5.0 was achieved, which is much better than many reported La-based adsorbents. The adsorbed phosphate can be effectively recovered with an alkaline solution. A multi-cycle regeneration-reuse study illustrated that the treated water still met the phosphorus discharge standard. The characterization results demonstrated the disappearance of La(OH)₃ and La₂(CO₃)₃ on the bead and the formation of NH₃⁺ … P and La-P groups after the adsorption, indicating the significant roles of ion exchange and electrostatic attraction on the uptake. The excellent performance found in this study clearly indicates that the optimized La/CS bead is promising in the treatment of phosphate and perhaps its recovery for industrial use.

Preparation, physicochemical properties and antimicrobial activity of chitosan from fly pupae

As an alternative chitosan source, edible insects have been proposed as an unconventional but viable option. Taking fly pupae as an example, this work performed chitosan extraction through a traditional chemical method with some modifications, and investigated its physicochemical properties and antimicrobial activity. The results showed that adding 0.5% sodium sulfite (Na2SO3, w/w, Na2SO3/fly pupae) synergized with sodium hydroxide (NaOH) for deproteinization was more effective than lye alone. Acid leaching was applied for desalination, and the optimal concentration of hydrochloric acid (HCl) was determined as 2 mol/L by ash content. For decoloration, the optimal decolorization oxidant was sodium hypochlorite (NaClO) with a concentration of 1.0%. For the deacetylation of chitin to chitosan, both the yield and degree of deacetylation (DD) using segmented treatment with alkali-NaOH were higher than those of traditional one-time deacetylation. The established physicochemical properties corresponded with the typical characteristics of chitosan. The determination of antimicrobial activity of chitosan by the turbidimetric method showed that chitosan exhibited notable activity in the order of Staphylococcus aureus > Escherichia coli > Saccharomyces cerevisiae, and this effect decreased with the increase in viscosity-average molecular weight (Mη). These results proved the viability of our improved method for the preparation of chitosan, a valuable antimicrobial agent, using an alternative natural source.

Recent Advances in PLA-Based Antibacterial Food Packaging and Its Applications

In order to reduce environmental pollution and resource waste, food packaging materials should not only have good biodegradable ability but also effective antibacterial properties. Poly(lactic acid) (PLA) is the most commonly used biopolymer for food packaging applications. PLA has good physical properties, mechanical properties, biodegradability, and cell compatibility but does not have inherent antibacterial properties. Therefore, antibacterial packaging materials based on PLA need to add antibacterial agents to the polymer matrix. Natural antibacterial agents are widely used in food packaging materials due to their low toxicity. The high volatility of natural antibacterial agents restricts their application in food packaging materials. Therefore, appropriate processing methods are particularly important. This review introduces PLA-based natural antibacterial food packaging, and the composition and application of natural antibacterial agents are discussed. The properties of natural antibacterial agents, the technology of binding with the matrix, and the effect of inhibiting various bacteria are summarized.

Synthesis, physicochemical characterization, antibacterial activity, and biocompatibility of quaternized hawthorn pectin

Quaternized polysaccharides are considered as potential antimicrobial materials due to their antimicrobial activity, biodegradability, biocompatibility, and water solubility. In this work, hawthorn pectin (HP) was obtained by ultrasound‑sodium citrate assisted extraction, quaternized hawthorn pectin (QHP) derivatives (namely: QHP-1, QHP-2, QHP-3, and QHP-4) with different degree of substitution were produced using (3-Chloro-2-hydroxypropyl) trimethylammonium chloride under alkaline conditions. The structure, properties, and morphology of HP and QHP were characterized by FTIR, XRD, ¹H NMR, high-performance gel permeation chromatography (HPGPC), thermal analysis, and SEM. The results of FTIR and ¹H NMR demonstrated that the quaternary ammonium modification was successful, and the degree of substitution (DS) of derivatives was calculated through elemental analysis. The determination of the minimum inhibitory concentrations and biofilm inhibition assay exhibited that QHP has a certain inhibitory effect on Escherichia coli and Staphylococcus aureus. Acceptable values of QHP were obtained in cytotoxicity assay on human keratinocytes.

LMWP (S3-3) from the Larvae of Musca domestica Alleviate D-IBS by Adjusting the Gut Microbiota

Diarrhea-based Irritable Bowel Syndrome (D-IBS) and diarrhea are both associated with ecological imbalance of the gut microbiota. Low Molecular Weight Peptides (LMWP) from the larvae of Musca domestica have been shown to be effective in the treatment of diarrhea and regulation of gut microbiota. Meanwhile, the single polypeptide S3-3 was successfully isolated and identified from LMWP in our previous studies. It remains unclear exactly whether and how LMWP (S3-3) alleviate D-IBS through regulating gut microbiota. We evaluated the gut microbiota and pharmacology to determine the regulation of gut microbiota structure and the alleviating effect on D-IBS through LMWP (S3-3). The rates of loose stools, abdominal withdrawal reflex (AWR) and intestinal tract motility results revealed that LMWP (S3-3) from the larvae of Musca domestica had a regulating effect against diarrhea, visceral hypersensitivity and gastrointestinal (GI) dysfunction in D-IBS model mice. Additionally, 16S rRNA gene sequencing was utilized to examine the gut microbiota, which suggests that LMWP induce structural changes in the gut microbiota and alter the levels of the following gut microbiota: Bacteroidetes, Proteobacteria and Verrucomicrobia. LMWP putatively functioned through regulating 5-HT, SERT, 5-HT2AR, 5-HT3AR and 5-HT4R according to the results of ELISA, qRT-PCR and IHC. The findings of this study will contribute to further understanding how LMWP (S3-3) attenuate the effects of D-IBS on diarrhea, visceral hypersensitivity and GI dysfunction.

Peculiarities of the interaction of sodium dodecyl sulfate with chitosan in acidic and alkaline media

In this work, the interaction between the negatively charged surfactant sodium dodecyl sulfate (SDS) and partially N-reacetylated chitosan (RA-CHI), which is soluble at pH range up to pH 12, is studied in a wide pH range including alkaline media by light scattering (LS) and isothermic titration calorimetry (ITC). It is shown that in the weakly alkaline medium (pH 7.4), RA-CHI/SDS interaction is exothermic and cooperative. This interaction is found to be coupled with proton transfer from the buffer substance to chitosan as it is revealed by the dependence of the measured heat release on the ionization enthalpy of the buffer. At higher pH values (pH > 8), another mechanism of interaction is observed that include SDS micellization induced by hydrophobic interactions with polymer segments, so that no phase separation occurred in these mixtures. The results obtained can contribute to expand the knowledge about application of chitosan for preparation of pharmaceutical and cosmetic compositions containing anionic surfactants.

Dual encapsulation of β-carotene by β-cyclodextrin and chitosan for 3D printing application

Dual encapsulation of β-carotene (CAT) by β-cyclodextrin (CCLD) and chitosan (CS) are prepared via self-assembly process by special addition order and concentration. CCLD and CS alone could not effectively stabilize CAT, while CAT could be encapsulated in cavity of CCLD and the inclusion complex could be further strengthened by CS, due to hydrogen-bonding between CCLD and CS via groups including NH₂ and OH. The dispersion system based on dual encapsulation of CAT had outstanding shear-thinning behavior, proper pseudoplastic properties, satisfactory yield stress, excellent thermal stability and great thixotropy, illustrating high potential for 3D printing. 3D printing of CAT-encapsulated system with high-content CS on paper and bread proves its excellent extrudability and printability, with possible potential in nutrition personalization. The designed host encapsulation structure by CCLD and CS plays a guiding role in incorporating functional materials including bioactives, probiotics, enzymes, vitamins, etc., and provides a reference in innovative food technology.

Effect of pH on the Surface Layer of Molecular Crystals at the Solid-Liquid Interface

Dissolution of solid matter into aqueous solution is one of the most challenging physicochemical aspects related to drug development. While influenced by several parameters, the effect of pH remains the most important one to be fully understood. The dissolution process is essentially controlled by activity at the surface of the molecular crystals, which is difficult to characterize experimentally. To address this, a combination of in situ atomic force microscopy (AFM) with molecular dynamics (MD) simulation is reported. AFM allows for direct visualization of the crystal surface of basic and acidic model compounds (carvedilol and ibuprofen) in contact with an aqueous medium with varying pH. A dramatic increase in surface mobility in the solid-liquid interface could be observed experimentally as a function of pH. The in situ AFM approach opens up for a more detailed understanding of the behavior of particulate matter in solution with importance at different levels, ranging from engineering aspects related to crystallization, and biological considerations related to bioavailability of the final drug product.

Application of chitosan nanoparticles in skin wound healing

The rising prevalence of impaired wound healing and the consequential healthcare burdens have gained increased attention over recent years. This has prompted research into the development of novel wound dressings with augmented wound healing functions. Nanoparticle (NP)-based delivery systems have become attractive candidates in constructing such wound dressings due to their various favourable attributes. The non-toxicity, biocompatibility and bioactivity of chitosan (CS)-based NPs make them ideal candidates for wound applications. This review focusses on the application of CS-based NP systems for use in wound treatment. An overview of the wound healing process was presented, followed by discussion on the properties and suitability of CS and its NPs in wound healing. The wound healing mechanisms exerted by CS-based NPs were then critically analysed and discussed in sections, namely haemostasis, infection prevention, inflammatory response, oxidative stress, angiogenesis, collagen deposition, and wound closure time. The results of the studies were thoroughly reviewed, and contradicting findings were identified and discussed. Based on the literature, the gap in research and future prospects in this research area were identified and highlighted. Current evidence shows that CS-based NPs possess superior wound healing effects either used on their own, or as drug delivery vehicles to encapsulate wound healing agents. It is concluded that great opportunities and potentials exist surrounding the use of CSNPs in wound healing.

Difference in the adhesion of Bifidobacterium breve to lotus seed resistant starch is attributable to its structural performance conferred by the preparation method

Resistant starch (RS) is a kind of important carbon source for colonic microorganisms. Its structure-function relationship is helpful to understand the mechanism of dietary nutrition in the body. In this paper, lotus seed resistant starches (LRS) prepared by microwave-power method (MP-LRS3-1 and MP-LRS3-2) and water-bath method (WB-LRS3-1 and WB-LRS3-2) were used to determine the structural changes and establish their nutritional interactions with Bifidobacterium breve. The results showed that four types all formed scale- and gully-like surface microstructures, B-type crystal structures, and lightly variable double helix structures. However, greater diffraction peak intensity was observed of MP-LRS3 at 18° and 19° compared with WB-LRS3, and higher crystallinity and tighter double helix were detected in MP-LRS3-1 than others. Meanwhile, MP-LRS3-1 showed the most effective proliferation promoting capability and highest adhesion value to B. breve. It might be related to specific surface microstructure and crystallinity differences of LRS caused by different preparing methods. There was also a positive correlation between the adhesion and the ability to promote proliferation, and it could be speculated this structural difference makes MP-LRS3-1 having highest adhesion ability and the most proliferative effect. This result can provide theoretical bases for improving the metabolism and probiotic action of RS.

Design and evaluation of nanostructured lipid carriers loaded with Salvia officinalis extract for Alzheimer's disease treatment

Considering the potential of Salvia officinalis in prevention and treatment of Alzheimer's disease (AD), as well as the ability of nanostructured lipid carriers (NLC) to successfully deliver drug molecules across blood-brain barrier (BBB), the objective of this study was design, development, optimization and characterization of freeze-dried salvia officinalis extract (FSE) loaded NLC intended for intranasal administration. NLC were prepared by solvent evaporation method and the optimization was carried out using central composite design (CCD) of experiments. Further, the optimized formulation (NLCo) was coated either with chitosan (NLCc) or poloxamer (NLCp). Surface characterization of the particles demonstrated a spherical shape with smooth exterior. Particle size of optimal formulations after 0.45 μm pore size filtration ranged from 127 ± 0.68 nm to 140 ± 0.74 nm. The zeta potential was -25.6 ± 0.404 mV; 22.4 ± 1.106 mV and - 6.74 ± 0.609 mV for NLCo, NLCc, and NLCp, respectively. Differential scanning calorimetry (DSC) confirmed the formation of NLC whereas Fourier-transform infrared spectroscopy confirmed the FSE encapsulation into particles. All formulations showcased relatively high drug loading (>86.74 mcg FSE/mg solid lipid) and were characterized by prolonged and controlled release that followed Peppas-Sahlin in vitro release kinetic model. Protein adsorption studies revealed the lowest adsorption of the proteins onto NLCp (43.53 ± 0.07%) and highest protein adsorption onto NLCc (55.97 ± 0.75%) surface. The modified ORAC assay demonstrated higher antioxidative activity for NLCo (95.31 ± 1.86%) and NLCc (97.76 ± 4.00%) as compared to FSE (90.30 ± 1.53%). Results obtained from cell cultures tests pointed to the potential of prepared NLCs for FSE brain targeting and controlled release.

Polyphenols from Grape Pomace: Functionalization of Chitosan-Coated Hydroxyapatite for Modulated Swelling and Release of Polyphenols

Chitosan is known for its specific antibacterial mechanism and biodegradability, while polyphenols are known for their antioxidant and anti-inflammatory properties: coupling these properties on a surface for bone contact, such as hydroxyapatite, is of great interest. The system developed here allows the combination of hydroxyapatite, chitosan, and polyphenol properties in the same multifunctional biomaterial in order to modulate the host response after implantation. Crosslinked chitosan is used in this research to create a stable coating on hydroxyapatite, and then it is functionalized for a smart release of the polyphenols. The release is higher in inflammatory conditions and lower in physiological conditions. The properties of the coated and functionalized samples are characterized on the as-prepared samples and after the samples are immersed (for 24 h) in solutions, which simulate the inflammatory and physiological conditions. Characterization is performed in order to confirm the presence of polyphenols grafted within the chitosan coating, the stability of grafting as a function of pH, the morphology of the coating and distribution of polyphenols on the surface, and the redox reactivity and radical scavenging activity of the functionalized coating. All the results are in line with previous results, which show a successful coating with chitosan and functionalization with polyphenols. Moreover, the polyphenols have a different release kinetics that is faster in a simulated inflammatory environment compared to that in the physiological environment. Even after the release tests, a fraction of polyphenols are still bound on the surface, maintaining the antioxidant and radical scavenging activity for a longer time. An electrostatic bond occurs between the negative-charged polar groups of polyphenols (carboxyls and/or phenols) and the positive amide groups of the chitosan coating, and the substitution of the crosslinker by the polyphenols occurs during the functionalization process.

Chemically Grafted Nanozyme Composite Cryogels to Enhance Antibacterial and Biocompatible Performance for Bioliquid Regulation and Adaptive Bacteria Trapping

Excessive biofluid and infection around wounds hinder wound healing. However, conventionally antibacterial wound dressings cannot simultaneously achieve effective biofluid control and intelligent infection treatment, tending to overhydrate wounds and develop drug-resistant bacteria due to the limitations of antibacterial components and material structures. The design of a nanozyme composite cryogel with interconnected macroporous structures, excellent designability, and lower chance of drug-resistance is greatly needed. Herein, Fe-MIL-88NH₂ nanozyme is grafted to glycidyl methacrylate functionalized dialdehyde chitosan via Schiff base reaction, and acryloyl Pluronic 127 (PF127-DA) is used as a cross-linking agent to fabricate nanozyme composite cryogels (CSG-M_X) as a wound dressing to enhance antibacterial and biocompatible performance for biofluid management and wound infection therapy. CSG-M_X has great hydrophilicity, acid-enhanced positive charge, pH-responsive release, rebinding of nanozymes, and excellent peroxidase and oxidase mimicry activity (generation of ^•OH and O₂^•- radicals). Notably, due to the negative potential of bacteria, the impact of infection on pH value, and the enzyme-like activity as well as the reversible release of nanozymes influenced by pH, CSG-M_X can achieve intelligently adaptive trapping and killing of bacteria. CSG-M_X has enormous potential to be a next-generation wound dressing for biofluid management and bacterial infection treatment in the clinic.

Current trends in chitosan based nanopharmaceuticals for topical vaginal therapies

Large surface area, rich vascularisation, well defined mucous membrane, balanced pH and relatively low enzymatic activity makes vagina a suitable site for drugs associated with women's health issues like Urinary tract infection (UTI) and vaginal infections. Therapeutic performance of intravaginal dosage forms largely depends on the properties of polymers and drugs. Chitosan (CS) because of its unique physical, chemical, pharmaceutical and biopharmaceutical properties have received a great deal of attention as an essential component in vaginal drug delivery systems. Further the presence of free amino and hydroxyl groups on the chitosan skeleton allows easy derivatization under mild conditions to meet specific application requirements. Moreover, CS-based nanopharmaceuticals like nanoparticles, nanofiber, nanogel, nanofilm, liposomes and micelles are widely studied to improve therapeutic performance of vaginal formulations. However, susceptibility of CS to the acidic pH of vagina, poor loading of hydrophobic drugs, rapid mucosal turn over are the key issues need to be addressed for successful outcomes. In this review, we have discussed the application of CS and CS derivatives in vaginal drug delivery and also highlight the recent progress in chitosan based nanocarrier platforms in terms of their limitations and potentials.

Polysaccharide-Based Hydrogels for Microencapsulation of Stem Cells in Regenerative Medicine

Stem cell-based therapy appears as a promising strategy to induce regeneration of damaged and diseased tissues. However, low survival, poor engraftment and a lack of site-specificity are major drawbacks. Polysaccharide hydrogels can address these issues and offer several advantages as cell delivery vehicles. They have become very popular due to their unique properties such as high-water content, biocompatibility, biodegradability and flexibility. Polysaccharide polymers can be physically or chemically crosslinked to construct biomimetic hydrogels. Their resemblance to living tissues mimics the native three-dimensional extracellular matrix and supports stem cell survival, proliferation and differentiation. Given the intricate nature of communication between hydrogels and stem cells, understanding their interaction is crucial. Cells are incorporated with polysaccharide hydrogels using various microencapsulation techniques, allowing generation of more relevant models and further enhancement of stem cell therapies. This paper provides a comprehensive review of human stem cells and polysaccharide hydrogels most used in regenerative medicine. The recent and advanced stem cell microencapsulation techniques, which include extrusion, emulsion, lithography, microfluidics, superhydrophobic surfaces and bioprinting, are described. This review also discusses current progress in clinical translation of stem-cell encapsulated polysaccharide hydrogels for cell delivery and disease modeling (drug testing and discovery) with focuses on musculoskeletal, nervous, cardiac and cancerous tissues.

Graphene oxide-chitosan hydrogel for adsorptive removal of diclofenac from aqueous solution: preparation, characterization, kinetic and thermodynamic modelling

This work aimed at developing a natural compound-based hydrogel adsorbent to remove diclofenac as a model pharmaceutical from water. First, graphene oxide-chitosan (GO-CTS) and amine graphene oxide-chitosan (AGO-CTS) hydrogel adsorbents were synthesized via a facile mechanical mixing method. The synthesized materials were characterized through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning and transmission electron microscopy (SEM and TEM), Raman spectroscopy, and thermogravimetric analysis (TGA) techniques. In the second stage, adsorption experiments were conducted to determine the best GO to CTS ratio and find the optimized adsorption parameters, including the initial drug concentration, adsorbent dosage, pH, and temperature. The results showed that the optimal GO to CTS mass ratio is 2 : 5 and thus the same ratio was selected as the AGO to CTS mass ratio to understand the effect of amine-functionalization on removal efficiency. The optimal adsorption parameters were determined to be pH of 5, C _i of 100 ppm and dosage of 1.5 g L^-1, where 90.42% and 97.06% removal was achieved for optimal GO-CTS and AGO-CTS hydrogel adsorbents, respectively. Langmuir and Freundlich isotherms models were employed to investigate the adsorption behavior of diclofenac onto the synthesized hydrogels. The results revealed that the adsorption tends to be of the monolayer type and homogeneous, as the results were in better accordance with the Langmuir model than the Freundlich model. The thermodynamics of adsorption demonstrated that the adsorption is exothermic, exhibiting higher removal efficiency at lower temperatures. Furthermore, Gibb's free energy change of adsorption (ΔG) suggested that the adsorption is spontaneous, being more spontaneous for AGO-CTS than GO-CTS hydrogels. Finally, the regeneration ability of the hydrogel adsorbents was studied in five consecutive cycles. The adsorbent maintained its efficiency at a relatively high level for three cycles but a considerable decrease was observed between the third and the fourth cycle, indicating that the hydrogels were recoverable for three cycles.

Antiseptic chitosan bandage for preventing topical skin infections

Infections on the wound surface are the major problem in restricting the healing process. To reduce the transmission and treat the infection, we have developed 0.05% and 0.1% octenidine dihydrochloride (Ocd) incorporated chitosan (Cs) based flexible bandages. Ocd is extensively used skin antiseptic for its mode of action over a broad spectrum of antimicrobial activity. The prepared antiseptic Cs-Ocd bandage was characterized using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). In addition, swelling, degradation, cytocompability, antibacterial, and anti-biofilm property of the developed bandages were studied. This highly porous nature of Cs-Ocd bandage showed enhanced swelling property, slow degradation profile and controlled release of Ocd. The prepared antiseptic bandage exhibited synergistic effect showing good hemostatic potential with Cs, excellent antimicrobial and anti-biofilm activity with Ocd against Staphylococcus aureus (S. aureus) and Candida auris (C. auris). Thus, the developed Cs-Ocd bandage can be used as potential antiseptic bandage for skin infections.

Sclerotium oryzae biocontrol in flooded rice fields with floating microcarrier technology: The effect of chitosan molecular weight

BACKGROUND

Biocontrol strategies are of significant concern for their application in crops. Various green practices have been designed, but almost all of them had delivery constraints. In particular, to design biocontrol strategies against Sclerotium oryzae in flooded rice fields, the active agent should be retained on the plant leaves by spreading application, nevertheless the direct application onto the water produces the biocontrol agent dilution. An effective delivery model was needed. This work aimed to evaluate the effects of chitosan molecular weight on the formation of positively charged Pseudomonas fluorescens-chitosan complex as a floating microcarrier against Sclerotium oryzae. To this end, three different sizes of chitosan [molecular weights (MWs) 20 000, 250 000, and 1 250 000 g mol^-1 ] at different pH values (4, 6, and 7) were tested. The electrostatic interaction was analyzed through ζ-potential measurement. An adjustment of the experimental values was carried out for making predictions. The bacteria antifungal activity into the carrier with different chitosan MWs was analyzed.

RESULTS

Our results suggest that it is possible to form a bacteria-chitosan complex with a net positive charge under condition that improve bacteria incorporation to the microcarrier technology without harming bacteria viability and antifungal activity. Thus, high chitosan MW (1 250 000 g mol^-1 ) at pH 6 is preferable for microcarrier technology.

CONCLUSION

Our findings provide relevant information about bacteria-chitosan interaction and may be useful in biocontrol programs that involved these two components as well as situations in which bacteria adsorption to an anionic carrier or anionic surface is desirable.

Antimicrobial Activities of Chitosan Derivatives

Considering the challenge created by the development of bacterial and fungal strains resistant to multiple therapeutic variants, new molecules and materials with specific properties against these microorganisms can be synthesized, like those synthesized from biopolymers such as chitosan with improved antimicrobial activities. Antimicrobial activities of seven obtained materials were tested on four reference strains belonging to American Type Culture Collection. The best antimicrobial activity was obtained by functionalization by impregnation of chitosan with quaternary ammonium salts, followed by that obtained by functionalization of chitosan with phosphonium. The lowest antibacterial and antifungal effects were expressed by Ch-THIO and Ch-MBT, but new materials obtained with these extractants may be precursors with a significant role in the direct control of active molecules, such as cell growth factors or cell signaling molecules.

Chitosan: An Overview of Its Properties and Applications

Chitosan has garnered much interest due to its properties and possible applications. Every year the number of publications and patents based on this polymer increase. Chitosan exhibits poor solubility in neutral and basic media, limiting its use in such conditions. Another serious obstacle is directly related to its natural origin. Chitosan is not a single polymer with a defined structure but a family of molecules with differences in their composition, size, and monomer distribution. These properties have a fundamental effect on the biological and technological performance of the polymer. Moreover, some of the biological properties claimed are discrete. In this review, we discuss how chitosan chemistry can solve the problems related to its poor solubility and can boost the polymer properties. We focus on some of the main biological properties of chitosan and the relationship with the physicochemical properties of the polymer. Then, we review two polymer applications related to green processes: the use of chitosan in the green synthesis of metallic nanoparticles and its use as support for biocatalysts. Finally, we briefly describe how making use of the technological properties of chitosan makes it possible to develop a variety of systems for drug delivery.

Desalination of duck egg white by biocoagulation to obtain peptide-ferrous chelate as iron delivery system: Preparation, characterization, and Fe2+ release evaluation in vitro

The annual output of salted duck egg white (SDEW) is estimated to be over 1.5 million tons in China, most of which is discarded due to high salt content. This has led to serious waste and environmental impact. Therefore, we developed an eco-friendly biocoagulation separation technology by combining chitosan and sodium alginate in order to produce a novel iron-binding peptide (DPs-Fe2+) from SDEW. The structure of DPs-Fe2+ was characterized by ultraviolet-visible spectroscopy, fluorescence spectroscopy, and Fourier transform infrared spectroscopy, followed by measuring DPs-Fe2+ response in a simulated digestion/Caco-2 cell model. Results showed that chitosan and sodium alginate complex could remove 91.21% of salt from SDEW, and the protein recovery rate reached 95.50%. Characterization results indicated that DPs bonded with Fe2+ to form a soluble chelate. Moreover, Caco-2 cell monolayer model indicated that the transport rate of Fe2+ was as high as 10.02% at 0.1 mg/ml concentration of digested chelates. The results demonstrate the potential application of DPs as a novel carrier for enhancing iron absorption. This research contributes to the development of an effective industrial desalination method and highlights an opportunity for recycling an otherwise discarded processing byproduct. PRACTICAL APPLICATION: Salted duck egg whites (SDEW) are the primary byproduct of salted egg yolk production, most of which is discarded due to high salt content. Hence, efficient utilization of the high-value proteins in SDEW is an urgent problem that must be resolved. Herein, we developed an effective industrial desalination method by combining chitosan and sodium alginate, which achieved excellent SDEW desalination and protein recovery. Furthermore, we produced a novel iron-binding peptide (DPs-Fe2+), which enhanced the transportation and absorption of Fe2+ in Caco-2 cell model, suggesting its potential as an iron supplement.

Production of Low Molecular Weight Chitosan and Chitooligosaccharides (COS): A Review

Chitosan is a biopolymer with high added value, and its properties are related to its molecular weight. Thus, high molecular weight values provide low solubility of chitosan, presenting limitations in its use. Based on this, several studies have developed different hydrolysis methods to reduce the molecular weight of chitosan. Acid hydrolysis is still the most used method to obtain low molecular weight chitosan and chitooligosaccharides. However, the use of acids can generate environmental impacts. When different methods are combined, gamma radiation and microwave power intensity are the variables that most influence acid hydrolysis. Otherwise, in oxidative hydrolysis with hydrogen peroxide, a long time is the limiting factor. Thus, it was observed that the most efficient method is the association between the different hydrolysis methods mentioned. However, this alternative can increase the cost of the process. Enzymatic hydrolysis is the most studied method due to its environmental advantages and high specificity. However, hydrolysis time and process cost are factors that still limit industrial application. In addition, the enzymatic method has a limited association with other hydrolysis methods due to the sensitivity of the enzymes. Therefore, this article seeks to extensively review the variables that influence the main methods of hydrolysis: acid concentration, radiation intensity, potency, time, temperature, pH, and enzyme/substrate ratio, observing their influence on molecular weight, yield, and characteristic of the product.

Graphene-Based Materials Immobilized within Chitosan: Applications as Adsorbents for the Removal of Aquatic Pollutants

Graphene and its derivatives, especially graphene oxide (GO), are attracting considerable interest in the fabrication of new adsorbents that have the potential to remove various pollutants that have escaped into the aquatic environment. Herein, the development of GO/chitosan (GO/CS) composites as adsorbent materials is described and reviewed. This combination is interesting as the addition of graphene to chitosan enhances its mechanical properties, while the chitosan hydrogel serves as an immobilization matrix for graphene. Following a brief description of both graphene and chitosan as independent adsorbent materials, the emerging GO/CS composites are introduced. The additional materials that have been added to the GO/CS composites, including magnetic iron oxides, chelating agents, cyclodextrins, additional adsorbents and polymeric blends, are then described and discussed. The performance of these materials in the removal of heavy metal ions, dyes and other organic molecules are discussed followed by the introduction of strategies employed in the regeneration of the GO/CS adsorbents. It is clear that, while some challenges exist, including cost, regeneration and selectivity in the adsorption process, the GO/CS composites are emerging as promising adsorbent materials.

Molecular features of the interaction and antimicrobial activity of chitosan in a solution containing sodium dodecyl sulfate

Molecular interaction of chitosan with sodium dodecyl sulfate (SDS) is a more complicated process than it has been imagined so far. For the first time it has been shown that the shorter chitosan chains are, the more preferably they interact with the SDS and the larger-in-size microparticles they form. The influence of ionic strength, urea and temperature on microparticles formation allows interpreting the mechanism of microparticles formation as a cooperative electrostatic interaction between SDS and chitosan with simultaneous decrease in the surface charge of the complexes initiating the aggregation of microparticles. It is shown that hydrogen bonding is mainly responsible for the aggregation while hydrophobic interaction has a lesser effect. Chitosan demonstrates a high bacteriostatic activity in the presence of SDS in solution and can be promising for preparation of microbiologically stable pharmaceutical hydrocolloids, cosmetic products and chitosan-based Pickering emulsions containing strong anionic surfactants.

Selective adsorption and fluorescence sensing of tetracycline by Zn-mediated chitosan non-woven fabric

Nowadays, numerous studies have focused on the newly developed technologies for the thorough removal of tetracyclines (TCs). The efficient removal of trace-amount pollutants requires the development of improved materials with higher adsorption capacity and increased adsorption selectivity. Zn(II)-mediated chitosan nonwoven fabric (Zn-CSNW) adsorbent with coordination capability was explored for the effective and selective removal of TC. The adsorption of TC to Zn-CSNW could reach equilibrium in about 30 min with a maximum adsorption capacity of 195.9 mg/g. It exhibited high anti-interference performance for TC adsorption at low concentrations, with good regeneration and effective reuse. Except for citrate, organic materials similar in structure to TC or common ions in aqueous solutions did not show obvious competition for the adsorption of low concentrations of TC. Additionally, the inherent fluorescence of chitosan and the fluorescence sensitization effect of Zn²⁺ for TC enabled function of Zn-CSNW as an indicator of the adsorption of TC by changes in fluorescence color and intensity under UV light (365 nm). It can indicate the saturation state of the Zn-CSNW, which will bring convenience to the use of the adsorbent. The Zn(II)-mediated coordination interaction plays a vital role in both the selective recognition of TC and the fluorescence sensing of adsorption amount, demonstrating an affordable and effective strategy for the treatment of water containing low amounts of antibiotics.

Development of Antimicrobial Laser-Induced Photodynamic Therapy Based on Ethylcellulose/Chitosan Nanocomposite with 5,10,15,20-Tetrakis(m-Hydroxyphenyl)porphyrin

The development of new antimicrobial strategies that act more efficiently than traditional antibiotics is becoming a necessity to combat multidrug-resistant pathogens. Here we report the efficacy of laser-light-irradiated 5,10,15,20-tetrakis(m-hydroxyphenyl)porphyrin (mTHPP) loaded onto an ethylcellulose (EC)/chitosan (Chs) nanocomposite in eradicating multi-drug resistant Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans. Surface loading of the ethylcelllose/chitosan composite with mTHPP was carried out and the resulting nanocomposite was fully characterized. The results indicate that the prepared nanocomposite incorporates mTHPP inside, and that the composite acquired an overall positive charge. The incorporation of mTHPP into the nanocomposite enhanced the photo- and thermal stability. Different laser wavelengths (458; 476; 488; 515; 635 nm), powers (5-70 mW), and exposure times (15-45 min) were investigated in the antimicrobial photodynamic therapy (aPDT) experiments, with the best inhibition observed using 635 nm with the mTHPP EC/Chs nanocomposite for C. albicans (59 ± 0.21%), P. aeruginosa (71.7 ± 1.72%), and S. aureus (74.2 ± 1.26%) with illumination of only 15 min. Utilization of higher doses (70 mW) for longer periods achieved more eradication of microbial growth.

Incorporation of gelatin improves toughness of collagen films with a homo-hierarchical structure

In this study, gelatin (type A and type B) with/without transglutaminase (TGase) were added to collagen fiber films to form hierarchical structure and its effects on the film were investigated. The analysis of mechanical properties indicate that gelatin significantly increased the toughness of the collagen film, where the 10 wt% type A gelatin -contained films had highest tensile strength, elongation at break and work of fracture. However, TGase crosslinking compromised the benefits of type A gelatin greatly, while type B gelatin showed a slight improvement, due to the difference in crosslinking activity between them. In the meantime, the hydrogen bonds were formed between the collagen and gelatin according to the results of the Fourier transformation infrared. In general, it is expected that the hierarchical structure formed in the collagen/gelatin films can be used as an effective strategy to enhance the collagen matrix films' mechanical properties.

Oregano (Origanum vulgar subsp. viride) Essential Oil: Extraction, Preparation, Characterization, and Encapsulation by Chitosan-Carbomer Nanoparticles for Biomedical Application

Background: Plant essential oils (EOs) as natural agents have broad activities, including antibacterial, antifungal, antiviral, insecticidal, and repel activities because of their chemical compositions. Objectives: The objective of this study was to increase the stability of Origanum vulgar subsp. viride EOs by encapsulation in chitosan-carbomer nanoparticles by ionic gelation method. Methods: The EOs from dried leaves of O. vulgar subsp. viride were extracted by hydro-distillation method, and EO components were determined by gas chromatography-mass spectrometry (GC-MS). Besides, OEO-loaded chitosan (CS) nano-capsules were prepared using the ionic gelation method. The molecular structure and morphology of nanoparticles were characterized by Fourier Transform-Infrared (FTIR) and scanning electron microscopy (SEM), respectively. The encapsulation efficiency (EE), loading capacity (LC) of the OEO-loaded CS nanoparticles, and their release profiles were determined using UV/Vis spectrophotometry. Results: The major components of OEO were thymol (20.53%), 4-terpinenol (20.28%), and γ-terpinene (12.22%). The percentages of EE and LC of OEO ranged from 99.25 ± 0.74 to 93.84 ± 0.71 and 38.02 ± 0.18 to 66.73 ± 0.51, respectively, with increasing the OEO to chitosan ratio from 1:0.01 to 1:0.04 W/V. The nanoparticles were regular, uniform, and spherical in shape with an average size of 134 to 181 nm, which were dispersed throughout the solution. The zeta potential values for blank chitosan nanoparticles (CSNPs) and OEO-loaded CSNPs were +23.4 and +38.5 mV, respectively. Conclusions: The results confirmed the suitability of the CS-carbomer complex for OEO- CSNPs formation. It is recommended to evaluate the antimicrobial, insecticidal and insect repel activities of developed OEO nanoparticles in laboratory and field studies.