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Chitosan (CS) derivatives with improved water solubility, antibacterial activity and adequate biocompatibility are attracting increasingly interest in medical application. Herein, we have successfully synthesized isocyanate terminated quaternary ammonium salt (IQAS) and sulfopropylbetaine (ISB) to be readily covalently bounded to CS skeleton by selective reaction with amino and hydroxyl groups. And their molecular structures and crystallinity were confirmed by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and X-ray diffraction. The effect of the substitution degree, carbon chain length, content ratio of IQAS/ISB on their water solubility, antibacterial activity and cytotoxicity were systematically investigated, which shows that those properties of the CS derivatives can be tailored by adjusting the grafted antibacterial agents and their additive amount. The structure-property relationship of these CS derivatives may provide a solid guidance on the development of CS derivatives for more efficient practical applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

Unidirectional liquid transport is critical in achieving high-performance moisture-management fabrics for medical care. However, realizing unidirectional liquid transport while simultaneously satisfying other requirements, such as antibacterial function, adhesiveness, low cytotoxicity, and adequate mechanical strength remains a challenge. In this study, Janus nanofibrous membranes exhibiting both unidirectional liquid transport and antibacterial activity were fabricated via electrospinning and a mild crosslinking procedure. This membrane provides continuous and spontaneous unidirectional water transport with a high one-way transport value (R) of 1483%. The membrane achieved antibacterial rates of 99.2% and 98.7% against E. coli and S. aureus, respectively, without leaching antibacterial agents. In addition, it has high elasticity and self-adhesive properties, which facilitates its use in a range of applications. The design of this versatile Janus nanofibrous membrane provides a new strategy for developing novel moisture-wicking systems, particularly in the field of medical dressings., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Hydrogel with good mechanical and biological properties has great potential and promise for biomedical applications. Here we fabricated a series of novel cytocompatible chitosan (CS) based double-network (DN) and triple-network (TN) hydrogels by physically-chemically crosslinking methods. Natural polysaccharide CS with abundant resources was chosen as the first network due to its good antimicrobial activity, biocompatibility and easy cross-linking reaction. Zwitterionic sulfopropylbetaine (PDMAPS) was chosen as the second network due its good biocompatibility, antimicrobial and antifouling properties. And nonionic poly(2-hydroxyethyl acrylate) (PHEA) was chosen as the final network due to its good biocompatibility, excellent nonfouling and mechanical properties. Cross-section SEM images showed that both CS/PHEA (DN 1 , the molar ratio of glutaraldehyde to structural unit of CS is 0.2/3.0) and CS/PDMAPS/PHEA (TN 1 , the molar ratio of glutaraldehyde to structural unit of CS is 0.2/3.0) hydrogels exhibited a smooth and uniformly dispersed porous microstructures with pore size distribution in the range of 20∼100 μm. The largest compressive stress and tensile stress of DN 1 hydrogels reached 84.7 MPa and 292 kPa, respectively, and largest compressive stress and tensile stress of TN 1 hydrogels could reach 81.9 MPa and 384 kPa, respectively. Moreover, the value of failure strain for TN 1 gels reached 1020%. Besides excellent mechanical properties, DN 1 and TN 1 gels exhibited good antimicrobial, cytocompatible and antifouling properties due to introduction of antimicrobial chitosan, cell anti-adhesive PDMAPS and PHEA. The combination of the excellent mechanical and biological properties of multiple network hydrogels can provide a potential pathway to develop biomedical hydrogels as promising bioapplications in wound dressing and other biomedical applications., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Eugenol is widely used in food industries where it encounters major concerns such as its poor solubility and stability. Herein, a novel eugenol-nanoemulsion was prepared by using ultrasonication as emulsification techniques, chitosan nanoparticle as carrier, and surfactant, as emulsifier. The results indicated that droplet size and encapsulation efficiency of the nanoemulsions was significantly affected by testing factors. The selected parameters for nanoemulsions were determined as chitosan-eugenol ratio of 1:1, Tween20 1 wt/v%, ultrasonic power 450 W and ultrasonic time 6 min. The nanoparticles were performed in regularly spherical shape distributed within 80-100 nm. Besides, the nanoemulsions showed great storage stability and thermal stability and the nanoeparticles performed excellent antioxidant capacity, antimicrobial activity as well as an initial burst of eugenol followed by plateau. Therefore, eugenol-chitosan nanoemulsions had great potential in food formulations for extending the shelf life., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Lysozyme was integrated into chitosan nanoparticles (CS-NPs) to improve the antibacterial activity. CS-NPs and chitosan-lysozyme nanoparticles (CS-Lys-NPs) were prepared according to the ionic gelation technique and then characterized by average size, zeta potential, polydispersity index (PDI), atomic force microscopy (AFM), fourier transform infrared (FT-IR), small-angle X-ray scattering (SAXS), circular dichroism (CD) and UV-visible spectroscopy. Antibacterial properties were investigated by transmission electron microscopy (TEM) based on observation of the inhibition zone and measurement of the minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) of CS-NPs and CS-Lys-NPs against E. coli and B. subtilis. The CS-NPs had particle sizes of 476.2-548.1nm, while an increase to ∼488.8 to 613.5nm was observed upon loading with lysozyme. The results suggested that the integration of lysozyme into CS-NPs enhanced the antibacterial activity against E. coli and B. subtilis, which may show great potential for use in the food industry and other applications in the form of direct addition or incorporation into packaging., (Copyright © 2016. Published by Elsevier Ltd.)

The chitosan gallates (CG) were obtained by free-radical-initiated grafting of gallic acid (GA) onto chitosan (CS) in this work. The chemical structures of the CG were corroborated by UV-vis, GPC and (1)H NMR analysis. The grafting reaction was accompanied with a degradation of the CS molecule. The shear-thinning flow behavior of CG film-forming solutions (CG FFS) decreased with the grafting amount of GA into CS chain, while the CG FFS grafted at a lower GA value behaved like a networks containing entangled or cross-linked polymer chains with a more elastic behavior. The increasing of GA grafting onto the CS chain led to a reduction of tensile strength, elongation at break and water resistance in the corresponding films, but increases in the antioxidant and antimicrobial activities were observed. The microstructure of the film was investigated using scanning electron and atomic force microscope, and the results were closely related to the observed film properties., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Chitosan (CS) has attracted much attention due to its good antibacterial activity and biocompatibility. However, CS is insoluble in neutral and alkaline aqueous solution, limiting its biomedical application to some extent. To circumvent this drawback, we have synthesized a novel N-quaternary ammonium-O-sulfobetaine-chitosan (Q3BCS) by introducing quaternary ammonium compound (QAC) and sulfobetaine, and its water-solubility, antibacterial activity and biocompatibility were evaluated compare to N-quaternary ammonium chitosan and native CS. The results showed that by introducing QAC, antibacterial activities and water-solubilities increase with degrees of substitution. The largest diameter zone of inhibition (DIZ) was improved from 0 (CS) to 15mm (N-Q3CS). And the water solution became completely transparent from pH 6.5 to pH 11; the maximal waters-solubility was improved from almost 0% (CS) to 113% at pH 7 (N-Q3CS). More importantly, by further introducing sulfobetaine, cell survival rate of Q3BCS increased from 30% (N-Q3CS) to 85% at 2000μg/ml, which is even greater than that of native CS. Furthermore, hemolysis of Q3BCS was dropped sharply from 4.07% (N-Q3CS) to 0.06%, while the water-solution and antibacterial activity were further improved significantly. This work proposes an efficient strategy to prepare CS derivatives with enhanced antibacterial activity, biocompatibility and water-solubility. Additionally, these properties can be finely tailored by changing the feed ratio of CS, glycidyl trimethylammonium chloride and NCO-sulfobetaine., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

To elucidate the structure-antioxidant activity relationships of chitosan gallate (CG), a series of CG derivatives with different degrees of substitution (DS's) and molecular weights (MWs) were synthesized from chitosan (CS) and gallic acid (GA) via a free radical graft reaction. A higher MW led to a lower DS of CG. The structures of CG were characterized by FT-IR and ¹H NMR, and results showed that GA was mainly conjugated to the C-2 and C-6 positions of the CS chain. The antioxidant activity (the DPPH radical scavenging activity and reducing power) were enhanced with an increased DS and a decreased MW of CG. A correlation between antioxidant activities and the DS and MW of CG was also established. In addition, a suitable concentration (0~250 μg/mL) of CG with different MWs (32.78~489.32 kDa) and DS's (0~92.89 mg·GAE/g CG) has no cytotoxicity. These results should provide a guideline to the application of CG derivatives in food or pharmacology industries.

Chitosan (CS) has been widely recognized as an important biomaterial due to its good antimicrobial activity, biocompatibility and biodegradability. However, CS is insoluble in water in neutral and alkaline aqueous solution due to the linear aggregation of chain molecules and the formation of crystallinity. This is one of the key factors that limit its practical applications. Therefore, improving the solubility of CS in neutral and alkaline aqueous solution is a primary research direction for biomedical applications. In this paper, a reactive antibacterial compound (4-(2,5-Dioxo-pyrrolidin-1-yloxycarbonyl)-benzyl)-triphenyl-phosphonium bromide (NHS-QPS) was synthesized for chemical modification of CS, and a series of novel polymeric antimicrobial agents, N-quaternary phosphonium chitosan derivatives (N-QPCSxy, x=1-2,y=1-4) were obtained. The water solubilities and antibacterial activities of N-QPCSxy against Escherichia coli and Staphylococcus aureus were evaluated compare to CS. The water solubility of N-QPCSxy was all better than that of CS at neutral pH aqueous solution, particularly, N-QPCS14 can be soluble in water over the pH range of 3 to 12. The antibacterial activities of CS derivatives were improved by introducing quaternary phosphonium salt, and antibacterial activity of N-QPCSxy increases with degree of substitution. Overall, N-QPCS14 represents a novel antibacterial polymer material with good antibacterial activity, waters solubility and low cytotoxicity., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The effect of chitosan (CS)-gallic acid (GA) conjugate (chitosan gallate, CS-g-GA) coating on the quality of silvery pomfret ( Pampus argenteus) during refrigerated storage at 4 °C for 15 days was investigated. The total mesophilic and psychrotrophic microbes in control and coated fish samples were counted periodically; physicochemical analyses to determine pH, total volatile basic nitrogen (TVB-N), peroxide value (POV), thiobarbituric acid-reactive substances (TBARS), K-value, and water-holding capacity (WHC) were carried out; and sensory attributes were evaluated. The results indicated that both CS + GA and CS-g-GA coatings effectively preserved the silvery pomfret quality during refrigerated storage. However, CS-g-GA had higher antimicrobial activity and a better ability to inhibit the formation of volatile bases (TVB-N) and lipid oxidation products (POV and TBARS) as well as the degradation of ATP and its breakdown products (K value) than CS + GA during the storage period. Furthermore, the CS-g-GA coating also helped to maintain a higher WHC and had better sensory properties for a longer period of time compared to the other treated samples, thus extending the shelf life and delaying the deterioration of fresh silvery pomfret by 3-6 days during refrigerated storage. These results suggest that a CS-g-GA coating could be employed as an active packaging material in the fish preservation industry. [ABSTRACT FROM AUTHOR]

To improve the antibacterial stability, a self-assembly method was applied. The typical antibiotic of nisin was loaded in chitosan nanoparticles (Nano-N) which was used as a carrier of antibiotics. The characteristics and formation mechanism of nano-scale antibiotic as well as its preservation properties on silvery pomfret were investigated. The results exhibited that the nano-scale antibiotics were nearly sphere-like with the mean size of 150 nm. The formation of nano-scale antibiotics was attributed to interactions among the functional groups of chitosan, sodium tripolyphosphate and nisin by hydrogen bonds and electrostatic interactions. Meanwhile, the preservation effects to silvery pomfret by the nano-scale antibiotic coatings were better than nisin or chitosan nanoparticle coating alone, which was ascribed to a more efficient prevented oxygen, microorganism as well as protein degradation from silvery pomfret by the self-assembled nano-scale antibiotic coating. Thus, it could extend the shelf life of fish by 3 d–9 d, suggesting that nano-nisin coating have great potential in the seafood preservation field. [ABSTRACT FROM AUTHOR]

Abstract: Citrus essential oils (CEOs) loaded in chitosan microcapsules ( CS-CEOs ) were prepared by 6 different emulsifiers (Tween 20, Tween 40, Tween 60, Tween 20/Span 801:1, Tween 20/SDBS1:1, Span 80) with emulsion-ionic gelation technique. Their rheological properties, embedding and release rate as well as microcapsules diameters were analyzed. The results indicated that emulsifier types significantly affected the size and embedding efficiency of microcapsules, obtaining sample groups of Tween 60, Span 80, Tween 20/Span 80 with typical diameters 289.3 nm, 3893.2 nm, 8843.2 nm, respectively. The structures and thermal properties of CEOs microcapsules were analyzed by using fourier transform infrared spectrophotometry (FT-IR), X-ray diffractometry and differential scanning calorimetry (DSC). Results demonstrated that CEOs oil were successfully embedded in the microcapsules and group of Tween 60 has the minimum particle size with the best embedding rate of 68.1%. The strength of the intermolecular interaction as well as exothermic peaks of microcapsules prepared with different emulsifiers were different, Tween 60 holds the lowest temperature value of exothermic peak for smallest internal energy is needed for melting, corresponds with its lowest particle size. Fourier transform infrared spectroscopy (FT-IR) provided profiles on the major functional groups of CS-CEOs. The results proved condition to prepare CS-CEOs microcapsules by using different emulsifiers. [ABSTRACT FROM AUTHOR]

Chitosan-nisin (CS-nisin) microcapsules were prepared and characterized. Its preservation properties (chemical stability, microbiological stability, color and sensory properties) were examined during the storage of small yellow croaker ( Pseudosciaena polyactis ). The results showed that CS-nisin microcapsules were spherical in shape with particle size greater than 1 μm. A significantly higher efficiency of CS-nisin microcapsules in inhibiting microorganism growth, lipid oxidation and protein degradation was observed, extending the shelf life of small yellow croaker during the storage by 6–9 days in comparision with CS, nisin treatment alone or the control according to the TVC assay, suggesting a better preservation effect of the microcapsules. [ABSTRACT FROM AUTHOR]

Nisin, a natural antimicrobial agent, was selected as the core material with chitosan (CS) as the wall material for micro-capsulation. Response surface methodology was used to optimize the process of preparing CS–nisin microcapsules. The predicted optimal condition was found to be CS concentration of 2.4 mg/ml, salt addition rate of 8 ml/min, CS: nisin by 3.8:1 (W/W) ratio, Na 2 SO 4 as the precipitant salt. In this condition, the embedding, release rate, Z-average size of the microcapsules were 68.7%, 54.6%, 1441.6 nm, respectively. According to the predicted model, the corresponding values were 66.9%, 50.8%, 1419 nm, respectively. Scanning electron microscope (SEM) revealed that CS-nisin microcapsules were spherical, and the size apparently increased compared with CS. Fourier transform infrared spectroscopy (FTIR) indicated that there was no significant chemical interaction between CS and nisin. Antimicrobial activity assay exhibited CS-nisin microcapsules with the concentration of 0.25% (W/V) showed confirmed inhibitory effect against Gram-positive bacteria Bacillus subtilis . Besides, 1% CS-nisin showed the maximum antibacterial activity at pH 5.0–6.0, when the value of pH was 7.4, it also exert antibacterial ability, indicating the enhanced antimicrobial activity of CS-nisin. [ABSTRACT FROM AUTHOR]