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PEGylation is regarded as a common antifouling strategy and the effect is normally linked with surface hydrophilicity of the coatings. Herein, the biopolymer chitosan (CS) was grafted by polyethylene glycol (PEG) of different chain lengths (molecular weight 200, 4 k and 100 k Da) to verify if the hydrophilicity of CS-PEG coatings is crucial in determining antifouling activities and if PEG chain length influences biofouling in marine environment. Properties of copolymers such as melting points and crystallinity are affected by grafting PEG. The water contact angle (WCA) of CS-PEG coatings increases with the chain length of grafted PEG, from 27° to 58°. Photocatalyst of zinc oxide-silver (ZnO/Ag) was also studied and its embedment (2 % to CS-PEG) renders the surface of CS-PEG coatings more hydrophobic with WCA increased from 52° to 86°. Antibacterial, anti-diatom, and anti-biofilm activities of the coatings were evaluated in natural sea water. The bacterial density on CS-PEG coatings was dramatically reduced to 4 × 10 4 compared to the control of 7 × 10 4 ind/mm 2 , and further to 2 × 10 4 for CS-PEG-ZnO/Ag coatings. CS-PEG coatings also strongly inhibit diatoms (120-200 ind/mm 2 ), but the inclusion of ZnO/Ag did not obviously enhance such effect (50-150 ind/mm 2 ). The findings provide useful insights for designing polymer-based antifouling coatings., 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 © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

In this study, a new chitosan Schiff base with surface modification using citric acid was synthesized for efficient removal of pernicious dyes, namely Bismarck Brown R (BBR) and Rhodamine B (RhB), from wastewater. The physicochemical properties of the modified chitosan Schiff base were comprehensively investigated. Adsorption studies demonstrated that BBR adsorption occurred through monolayer formation, while RhB adsorption proceeded via multilayer formation on the heterogeneous surface. The synthesized adsorbent exhibited exceptional dye removal efficiency, with a Langmuir saturation capacity of 348 ± 11.0 mg.g -1 for BBR and 145 ± 18.44 mg.g -1 for RhB. Isotherm data fitting revealed consistency with the Langmuir isotherm model for BBR and the Freundlich isotherm model for RhB. Notably, the modified chitosan Schiff base showcased enhanced antibacterial properties, effectively inhibiting both gram-positive and gram-negative bacteria. The study's findings underscore the potential of this novel chitosan-based Schiff base as an efficient adsorbent for the removal of various dyes from wastewater, emphasizing its versatility and practical applicability in water treatment processes., 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 © 2024 Elsevier B.V. All rights reserved.)

There is plenty of scope for modifying chitosan, an only polycationic natural polysaccharide, owing to its reactive functional groups, namely hydroxyl and amino groups. Although innumerable numbers of chitosan derivatives have been synthesized by modifying these groups and reported elsewhere, in this review article, an attempt has been exclusively made to demonstrate the syntheses of various chitosan-based Schiff bases (CSBs) simply by allowing the reactions of reactive amino groups of chitosan with different aldehydes/ketones of interest. Due to their very peculiar and unique characteristics, such as biodegradability, biocompatibility, metal-binding capability, etc., they are found to be very useful for diversified applications. Thus, we have also attempted to showcase their very specific biomedical fields, including tissue engineering, drug delivery, and wound healing, to name a few. In addition, we have also discussed the utilization of CSBs for industrial applications such as wastewater treatment, catalysis, corrosion inhibition, sensors, etc., 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 © 2023 Elsevier Ltd. All rights reserved.)

The incorporation of plant materials is an effective method to improve the stability of chitosan beads, as it further increases the adsorption of toxic dyes and metals from aqueous systems. In the present study, chitosan gels were impregnated with a novel type of powder as the groundnut hull powder in order to form composite beads by using a simple droplet-based microfluidic system. The beads were then characterised through various techniques such as SEM, TGA, FTIR, and XRD. Microscopic imaging revealed a change in the surface morphology of the composite beads, which became rough and wrinkled with more valley-like features and irregular cracks. FTIR data suggest that the impregnation of groundnut hull powder led to an increase in functional groups. The thermal analysis allowed for the assessment of composite bead hydration contents and indicated the presence of groundnut hull entrapped in the loaded beads, which was corroborated by vibrational spectroscopy. XRD analysis allows us to conclude that there is an involvement of groundnut hull in the chitosan gels, and the consequence of that is the formation of amorphous beads, which would make them suitable for the adsorption of toxic dyes and metals from water systems., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Benzophenone-3 grafted chitosan (CS-BP-3) was successfully synthesized and applied as an antibacterial coating for the first time. The grafting mechanism is based on the reaction between ketone and primary amine to form imine derivatives and the chemical structure of grafted chitosan was studied by Fourier transform infrared (FT-IR) spectroscopy. Water solubility of BP-3 is enhanced after covalently grafted on chitosan and consequently renders the chitosan coating with UV blocking property. Results of thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) further confirmed the thermal stability of BP-3 modified chitosan is enhanced. The CS-BP-3 coating was applied on a variety of substrates of glass, plastics, wood, and metal. The surface features of the coatings such as morphology, water contact angle (WCA), and surface roughness were investigated. The optical and thermal stabilities of the coatings under UV irradiation were studied for 16 h. Antibacterial activity of CS-BP-3 was evaluated against both Gram-negative and Gram-positive bacteria. And the results of bacterial inhibition by CS-BP-3 coating indicate its potential for future application in food packaging., Competing Interests: Declaration of competing interest The authors confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

In the present study, chitosan (C), walnut (W), and almond shell (A) powder adsorbent (in different combinations as almond shells:walnut:chitosan 2:1:1 (AWC), chitosan:almond shell:walnut 2:1:1 (CAW), and walnut:almond shells:chitosan 2:1:1 (WAC)) powder were combined in different ratios to produce low-cost composite adsorbent beads for the removal of antibiotics gatifloxacin (GAT) from synthetic wastewater. The beads were characterized by a scanning electron microscope, Fourier transform infrared spectrum spectrophotometer, and energy-dispersive X-ray spectroscopy. The batch adsorption approach was employed to remove the antibiotic from the water. Moreover, isotherm and kinetics were conducted to illustrate the adsorption mechanism. Parameters like the effect of the adsorbent's dosage, pH, initial concentration, and contact time on antibiotic adsorption were evaluated. Adsorption percentage increased slightly with the increase in adsorbent dosage. The optimum pH for GAT adsorption on beads was 5-7. In addition, adsorption increased with initial antibiotic concentration and time rise. The adsorption isotherm data were successfully fitted to Langmuir isotherm for AWC and CAW beads, while WAC beads followed the Freundlich isotherm. The highest adsorption was attained at pH 5 on CAW beads and pH 7 on AWC and WAC beads. The optimal contact time for equilibrium studies was 120 min for all types of beads. The adsorption isotherm data in AWC beads fit well with the Langmuir model and Freundlich adsorption for CAW and WAC beads. The rate of adsorption on beads follows Lagergren pseudo-second-order kinetics. The results indicate that prepared combination beads can be used to remove antibiotics from wastewater., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In this study, a series of chitosan-sepiolite (CS-SEP) nanocomposites films were prepared by using a conventional solution casting method. The effect of sepiolite on physicochemical and biological properties of the prepared nanocomposite films was studied by various techniques such as Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and x-ray diffraction (XRD) to name a few. In WCA measurements, the decrease of contact angle from 78.51° (CS) to 71.29° (CS7SEP3) reaffirms the water holding nature of sepiolite, which enables to create moist environment essentially required for wound healing. Further, addition of sepiolite tremendously increased WVTR, folding endurance, porosity, and blood clotting ability of the prepared nanocomposites. Furthermore, CS-SEP nanocomposite films exhibit better antibacterial activity than that of chitosan against gram positive (B. subtilis) and gram negative bacteria (E. coli). Moreover, the percentage of hemolysis and degradation study indicated that the prepared nanocomposite films were non-hemolytic in nature and decomposed nearly 40% in four weeks. In addition, cytotoxicity assay showed that the prepared nanocomposite film i.e. CS7SEP3 exhibited better cell viability and cell proliferation rate against L929 mouse fibroblast cells as compared to CS and hence, the prepared nanocomposite film can be used as a promising candidate for wound management., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Functional nanocomposites with biopolymers and zinc oxide (ZnO) nanoparticles is an emerging application of photocatalysis in antifouling coatings. The reduced chemical stability of ZnO in the acidic media in which chitosan is soluble affects the performance of chitosan nanocomposites in antifouling applications. In this study, a thin shell of amorphous tin dioxide (SnO x ) was grown on the surface of ZnO to form ZnO-SnO x core-shell nanoparticles that improved the chemical stability of the photocatalyst nanoparticles, as examined at pH 3 and 6. The photocatalytic activity of ZnO-SnO x in the degradation of methylene blue (MB) dye under visible light showed a higher efficiency than that of ZnO nanoparticles due to the passivation of electronic defects. Chitosan-based antifouling coatings with varying percentages of ZnO or ZnO-SnO x nanoparticles, with or without the glutaraldehyde (GA) crosslinking of chitosan, were developed and studied. The incorporation of photocatalysts into the chitosan matrix enhanced the thermal stability of the coatings. Through a mesocosm study using running natural seawater, it was found that chitosan/ZnO-SnO x /GA coatings enabled better inhibition of bacterial growth compared to chitosan coatings alone. This study demonstrates the antifouling potential of chitosan nanocomposite coatings containing core-shell nanoparticles as an effective solution for the prevention of biofouling.

A biopolymer coating on copper was prepared based on chitosan nanocomposite and its corrosion inhibition efficiency was investigated. Inclusion of silica nanoparticles substantially reduces swelling ratio of chitosan coating while enhancing its thermal stability. The corrosion resistance of chitosan-based coatings is improved by introducing 2-mercaptobenzothiazole and silica in the matrix. It is found that upon crosslinking the chitosan coatings, a higher corrosion resistance could be achieved and the highest inhibition efficiency for chitosan nanocomposite coatings is calculated as 85%. The corrosion mechanism is found closely related to mass transition and diffusion process, and also the polarization resistance contributes to the impedance. Calculated impedance using Kramers-Kronig transformation shows good agreement with experimental values, thus validating the impedance measurements. This study exhibits the enhanced efficiency of nanocomposite and potential of chitosan coatings in corrosion prevention for copper., Competing Interests: Declaration of competing interest The authors confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

The advent of liposome technology with its unique features has led researchers to work relentlessly on the successful development of novel drug delivery vehicles based on liposomes. But still there are some limitations of using liposomes for biomedical applications because of their poor stability that is primarily the cause of rapid leakage of drugs incorporated within the said matrices. Therefore, a considerable interest has been paid on modification of surface of liposomes by combining it with several compounds of interest. Although chitosan-liposome based systems are not yet well-documented. Hence, in this review, we exclusively focused on the discussion about the preparation of various chitosan-liposome based systems and their suitable biomedical applications as well., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In this present study, ternary nanocomposite films of chitosan/starch/halloysite nanotubes (ChSHT) were fabricated by solution casting process. The ternary nanocomposite films were characterized by using various techniques such as Fourier transform infrared (FTIR), X-ray Diffraction (XRD), water contact angle, water absorption capacity, water solubility, folding endurance, tensile strength, elongation at break, thickness, porosity, water vapour transmission rate (WVTR), and hemocompatibility. FTIR and XRD results confirmed the interaction of halloysite nanotubes with chitosan-starch (ChS) solution. Further, the ChSHT ternary nanocomposite films showed improved water absorption capacity, water solubility, and water vapour transmission rate (WVTR). Water contact angle measurements also showed that the nanocomposite films were hydrophilic in nature. The hemocompatibility results showed that all the prepared nanocomposite films were non-hemolytic in nature. Furthermore, microbial penetration test showed that all the prepared ternary nanocomposite films were impermeable to bacteria. Considering the above-mentioned results, it is concluded that the ChSHT nanocomposite films could be used as promising wound cover materials., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A series of novel chitosan-bentonite nanocomposite (CBN) films were prepared by using solvent casting method for wound healing application. The physicochemical properties namely thickness, folding endurance, water absorption capacity, and water vapour transmission rate (WVTR) of the films were studied. Fourier transform infrared spectroscopy (FTIR) was employed to ascertain the interaction between negatively charged bentonite and positively charged chitosan. The surface morphology of the prepared composite films was also studied by scanning electron microscopy (SEM). Results showed that WVTR, water absorption capacity, thickness, and folding endurance of the CBN films were 1093±20.5-1954±51gm -2 day -1 , 1232±14.58-1688±18.52, 17.50±5-42.50±9.75μm, and 145.25±2.21-289.50±0.57 respectively. Due to strong hydrophilic nature of bentonite, it greatly enhances the water absorption capacities of the prepared nanocomposite films. In addition, the presence of bentonite in the said films also increases the mechanical strength. Moreover, the antibacterial activity of the films was investigated against gram positive and gram negative. It was found that all CBN films showed good inhibitory activity against all the tested bacteria as compared to control. The above analysis suggested that the CBN films could be used as potential candidates for wound healing application., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Marine biofouling is a worldwide problem affecting maritime industries. Global concerns about the high toxicity of antifouling paints have highlighted the need to develop less toxic antifouling coatings. Chitosan is a natural polymer with antimicrobial, antifungal and antialgal properties that is obtained from partial deacetylation of crustacean waste. In the present study, nanocomposite chitosan-zinc oxide (chitosan-ZnO) nanoparticle hybrid coatings were developed and their antifouling activity was tested. Chitosan-ZnO nanoparticle coatings showed anti-diatom activity against Navicula sp. and antibacterial activity against the marine bacterium Pseudoalteromonas nigrifaciens. Additional antifouling properties of the coatings were investigated in a mesocosm study using tanks containing natural sea water under controlled laboratory conditions. Each week for four weeks, biofilm was removed and analysed by flow cytometry to estimate total bacterial densities on the coated substrates. Chitosan-ZnO hybrid coatings led to better inhibition of bacterial growth in comparison to chitosan coatings alone, as determined by flow cytometry. This study demonstrates the antifouling potential of chitosan-ZnO nanocomposite hybrid coatings, which can be used for the prevention of biofouling., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The main aim of this work was to prepare wound healing material with chitosan, poly vinyl pyrrolidone (PVP), silver oxide nanoparticles. The prepared chitosan, chitosan-PVP-nano silver oxide (CPS) films were characterized for their thermal behaviour, morphological properties, mechanical properties, antibacterial properties and wound healing properties. The CPS film found higher antibacterial activity because the materials both chitosan as well as silver oxide poses good antibacterial activity. L929 cell lines were for cytotoxicity study and Adult male albino rats (140-180 g) were used for wound healing study. The prepared film has more wound healing property than of cotton gauge, 100% chitosan and other reported chitosan based dressings., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In our present study, the blends of chitosan, poly(N-vinylpyrrolidone) (PVP) and titanium dioxide (TiO2) were investigated by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The size distribution of the TiO2 nanoparticles was measured using transmission electron microscope and scanning electron microscope. The studies on the mechanical properties of composite material indicate that the addition of TiO2 nanoparticles increases its strength. The prepared nanocomposite dressing has excellent antimicrobial efficacy and good biocompatibility against NIH3T3 and L929 fibroblast cells. Compared to conventional gauze, soframycin skin ointment and chitosan treated groups, the prepared nano dressing caused an accelerated healing of open excision type wounds in albino rat model. The synergistic effects of nanocomposite dressing material like good antibacterial ability, high swelling properties, high WVTR, excellent hydrophilic nature, biocompatibility, wound appearance and wound closure rate through in vivo test makes it a suitable candidate for wound healing applications., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

In our present investigation, a ternary nano dressing consists of titanium dioxide nano particle loaded chitosan-pectin was prepared to evaluate biocompatibility, antimicrobial and in vivo wound healing properties. The photoactive property of TiO₂ based materials makes it important candidate for numerous medical applications. Chitosan can be easily processed into membranes, gels, nanofibers, beads, nanoparticles, scaffolds, and sponge forms that can be used in wound healing applications. Pectin acts as a natural prophylactic substance against poisoning with toxic cations and its styptic and curing effects are well documented in healing ointments. The characterizations of prepared nano dressing were made by FTIR, TGA, DSC, SEM and TEM. The physicochemical parameters of nano dressing were evaluated by various techniques, namely, the Whole blood clotting test, haemolysis ratio measurement, cytotoxicity test using NIH3T3 and L929 fibroblast cells. The in vivo open excision-type wound healing efficiency of prepared nano dressing and its comparison with conventional gauze were evaluated by measuring wound contraction and histological examinations in adult male albino rats. The synergistic effects of nano dressing such as good antibacterial ability, high swelling properties, high water vapour transmission rate (WVTR), excellent hydrophilic nature, biocompatibility, wound appearance, wound closure rate and histological study through in vivo test makes it a suitable candidate for wound healing applications., (Copyright © 2013 Elsevier B.V. All rights reserved.)

In this study, hydrothermally prepared magnetic α-Fe2O3 nanoparticles were dispersed in chitosan (CH) solution to fabricate nanocomposite film. X-ray diffraction (XRD) patterns indicated that the α-Fe2O3 nanoparticles were pure α-Fe2O3 with rhombohedral structures, and the fabrication of CH did not result in a phase change. The scanning electron microscopy (SEM) and transmission electron microscope (TEM) results showed that the hexagonal and spherical monodispersed α-Fe2O3 nanoparticles were encapsulated into the spherical dumb shaped CH-α-Fe2O3 nanocomposite film with a mean diameter of ∼87 and ∼110 nm respectively. The α-Fe2O3 nanoparticles and CH-α-Fe2O3 nanocomposite film were also characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM). Magnetic measurements revealed that the saturated magnetization (Ms) and remanent magnetization (Mr) of the pure α-Fe2O3 nanoparticles reached 0.573 emu/g and 0.100 emu/g respectively and the nanoparticles showed the characteristics of weak ferromagnetic before and after coating with CH., (Copyright © 2010 Elsevier B.V. All rights reserved.)

The novel N-heterocyclic chitosan aerogel derivatives were prepared by reacting 79% deacetylated chitosan separately with 4-pyridinecarboxaldehyde and 2,6-pyridinedicarboxaldehyde followed by subsequent solvent exchange into acetone, filteration and lyophilization. The identity of the Schiff bases was confirmed by UV-vis absorption spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The N-heterocyclic chitosan derivatives were evaluated by X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), rheological studies and biological activity. Overall, the N-heterocyclic chitosan derivative based gels open new perspectives in biomedical applications.

• Heavy metal (HM) exposure causes ecological imbalance. • Chitosan is highly effective in the adsorption of HMs, both individually and synergistically. • Modification of chitosan through grafting crosslinking for enhanced adsorption of heavy metals from water. • Role of physiochemical parameters in regulating the adsorption efficiency of chitosan. • Limitations of chitosan nanoparticles for heavy metal adsorption. The advancement of industrialization has put the environment at risk of getting saturated with different contaminants. Heavy metals (HMs) emerging from industries, reaching the water bodies expose marine biota to these stressors, leading to negative effects on growth and development. Thus, it is imperative to detoxify the environment from these HM contaminants through degradation, and adsorption. Several mechanical and chemical methods have been developed and implied for the purpose of minimizing HM contamination, but they often give rise to certain by-products that are toxic in nature. Over the years, chitosan has emerged as a potent adsorption material for reducing HM contamination. Chitosan is obtained from multiple natural sources, and owing to its versatile nature, it shows significant capacity for adsorbing different HMs and HM ions. Chitosan is used in synergy with some of the agents to increase its adsorption efficiency. The preparation of graft, beads, functionalized chitosan, crosslinkers, nanoparticles, and nanotubes are some of the potential methods that have been used in modifying chitosan. This paper gives an overview of the ecotoxicological effects of HMs, besides mentioning the fundamental sources of chitosan. The individual role of chitosan and its synergistic role have been discussed in greater detail. Moreover, the limitations associated with chitosan as an HM adsorbent have been delineated. [ABSTRACT FROM AUTHOR]

Worldwide, millions of tons of crustaceans are produced every year and consumed as protein-rich seafood. However, the shells of the crustaceans and other non-edible parts constituting about half of the body mass are usually discarded as waste. These discarded crustacean shells are a prominent source of polysaccharide (chitin) and protein. Chitosan is a de-acetylated form of chitin obtained from the crustacean waste that has attracted attention for applications in food, biomedical, and paint industries due to its characteristic properties, like solubility in weak acids, film-forming ability, pH-sensitivity, biodegradability, and biocompatibility. We present an overview of the application of chitosan in composite coatings for applications in food, paint, and water treatment. In the context of food industries, the main focus is on fabrication and application of chitosan-based composite films and coatings for prolonging the post-harvest life of fruits and vegetables, whereas anti-corrosion and self-healing properties are the main properties considered for antifouling applications in paints in this review. [ABSTRACT FROM AUTHOR]

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Hydrogels have drawn great attention to researchers for its versatile kinds of properties, particularly in biomedical fields of research. The present hydrogels prepared by using chitosan as base material and acetic acid (aq) and propylene glycol as solvents for wound healing application. The durability of the hydrogels were lasted for prolong duration and its physico-chemical and biological properties were evaluated in a systematic manner. The microbiological screening has demonstrated the positive cellular mouse skin fibroblast activity against cell line (NIH 3T3). Viability was measured based on the esterase enzyme activity and plasma membrane integrity by FDA assay. The assays for cell proliferation and viability showed that prepared hydrogel was biocompatible. The studies of swelling and drug delivery were conducted with impressive results. Overall, this finding indicates the suitability of prepared hydrogel for wound healing application. [ABSTRACT FROM AUTHOR]

In this study, a ternary nanocomposite film based on chitosan/starch/bentonite (ChSB) was prepared by a simple and versatile solution casting and evaporation method. The physicochemical properties namely thickness, folding strength, water absorption capacity, water vapour transmission rate (WVTR), dressing pH, porosity, and nonenzymatic hydrolytic degradation rate of the nanocomposite film were studied in the laboratory. The addition of bentonite into the solution mixture of chitosan and starch greatly enhanced the mechanical strength, water absorption capacity, as well as WVTR of the nanocomposite film but on the other hand, it did not show any significant effect on porosity. The dressing pH of the nanocomposite film was also measured and it was in the acceptable range between 5.25 and 7.90, usually desired for any ideal wound dressings. The respective percentage hemolysis study and nonenzymatic degradation rate revealed that the ChSB nanocomposite film was hemocompatible and biodegradable in nature. Therefore, it can be concluded that the ChSB ternary nanocomposite film could potentially be used as a suitable dressing for wound healing application. [ABSTRACT FROM AUTHOR]

The use of oppositely charged colloidal nanoparticles to build multilayered structures is an approach in thin film science. In this work, uniform spherical nano-dispersions of gold (ca. 20 nm) and silica (ca. 30 nm) were synthesised with specific volume concentration to achieve colloidal stability. Exploiting the use of self-assembly, multilayers of these oppositely charged nanoparticles were built using alternate coating with chitosan. Gold nanoparticles have strong optical absorption in visible region of electromagnetic spectrum resulting from its surface plasmon resonance. Silica nanoparticles have low refractive index and absorb light mostly in the ultraviolet (UV) region. The optical absorption band of the fabricated thin films extends from UV to visible region of the electromagnetic spectrum. The spectral characteristics of these thin-film assemblies are a combination of thickness and the order of the layers in a stack. These films have potential applications as optical elements and in optoelectronics. © 2011 Canadian Society for Chemical Engineering [ABSTRACT FROM AUTHOR]

A novel fabrication method for optical thin film filters based on the self-organization of alternating layers of colloidal gold and silica nanoparticles (NP) is reported. The filter is designed to work in the deep-UV to visible spectral range. The spectral absorption peaks are tuned by three parameters: the organic capping ligand of the gold NPs (citrate, chitosan, poly (diallyl-dimethylammonium)-chloride or PDDA); the capping environment (bare, chitosan, or PDDA) of the silica NPs and the thickness of the film. Precise control of the transmission color (less than 1% color distance per layer), is achieved by changing the film thickness. Exploitation of the self-assembly process should lead to the facile production of highly reliable large area thin film optical filters at considerably lower costs. [ABSTRACT FROM AUTHOR]

In this article, we have described microwave assisted synthesis of 3-formyl-10H phenothiazine and preparation of chitosan-phenothiazine derivative film with potential for optical properties in biomedical applications, vis-a-vis it is also important to ensure that chemical processes used in converting biopolymer to useful material through green chemistry approach. From optical properties and biomedical application point of views, it is a benign technique. Chitosan-derivative film was prepared from hydrogel by solution casting method. The prepared chitosan-phenothiazine derivative was confirmed by Fourier transform infrared spectroscopy (FTIR). The film was evaluated by XRD, thermal analysis, surface morphology, photoluminescence (PL) spectrscopy and second harmonic generation (SHG) study. Overall, the chitosan-phenothiazine derivative film opens new perspectives to optical material for biomedical applications. [ABSTRACT FROM AUTHOR]

Chitin and chitosan are versatile polymers, where the interest in chitosan is due to the large variety of useful forms that are commercially available or can be made available. Chitin basically is obtained from prawn/crab shells; chemical treatment of chitin produces chitosan. This article surveys applications of chitin and chitosan in various industrial and biomedical fields. [ABSTRACT FROM AUTHOR]

Rapid postharvest losses and quality deteriorations in pineapple are major challenges to growers and handlers. Chitosan-based coatings on fruit surfaces have gained importance in recent years to enhance postharvest shelf life of the fruits. In this study, aloe vera gel was added as a natural antioxidant in chitosan-based composite coating containing ZnO nanoparticles. The developed formulation was applied on the surface of freshly harvested pineapple fruits. ZnO nanoparticles were used as an antimicrobial agent. Coated pineapple fruits were evaluated for weight loss, total soluble solids, titratable acidity, decay index, maturity index, and sensory attributes, including visual appearance, periodically at 5 day interval during storage. The results showed that the coating of the fruit reduced weight loss by about 5%, and also delayed ripening and oxidative decay compared to the uncoated fruit. Thus, the developed coating formulation is a promising sustainable solution to reduce postharvest losses and to extend shelf life of pineapples. [ABSTRACT FROM AUTHOR]

In the context of emerging global concerns with synthetic plastic packaging, alternative natural biodegradable packaging materials are gaining increasing attention for food packaging applications. In this study, chitosan and gelatin nanocomposite hybrid films containing green synthesized zinc oxide (ZnO) nanoparticles (NPs) were developed and microstructural properties were studied. Antimicrobial activity of the developed films was evaluated using both Gram negative (Escherichia coli) and Gram positive bacteria (Staphylococcus aureus). Green synthesis protocol was used for the precipitation of ZnO NPs using fruit extract of Cassia fistula. The as-synthesized polyhedral ZnO NPs were in the range of 20–40 nm (average size ≈29 nm). Reinforcement with ZnO NPs in the hybrid films lead to improved thermal stability, elongation-at-break (EAB), and compactness properties. The developed films with 2% and 4% ZnO NPs showed a smooth, compact, and heterogeneous surface morphology compared to the control (chitosan-gelatin hybrid) films. Disc diffusion assays showed that the nanocomposite film had significant antimicrobial activity against E. coli. The developed hybrid nanocomposite films have potential to be developed as biodegradable alternative for postharvest packaging of fresh fruits and vegetables. [ABSTRACT FROM AUTHOR]

Demand for healthy and safe food with minimal use of synthetic inputs (including synthetic preservatives) is increasing rapidly. Plastic polymers being hazardous to the environment, significant efforts have been devoted to evaluate various bio-based polymers as alternatives to synthetic plastic packaging. Chitin and its deacetylated derivative, chitosan, is primarily a by-product of crustacean, fish and seafood processing and handling. Chitosan possesses antimicrobial activities and film forming property, making them attractive biopolymers for food packaging and food preservation applications applied through spraying, dipping, coating, or wrapping by films. This comprehensive review of contemporary research focuses on applications of chitosan and chitosan based nanocomposites in the area of food packaging and preservation. It includes different properties and functionalities of chitosan, various blends and nanocomposites of chitosan, their fabrication techniques, and applications in shelf life extension of fruits, vegetables, meat and fish products. Chitosan is an attractive alternative to synthetic plastics polymers due to its biodegradability, antimicrobial activity, and film forming properties. Incorporation of nanomaterials into chitosan based food-packaging systems can prevent the growth of spoilage and pathogenic microorganisms, improve food quality and safety, and extend shelf-life of food. It has been reported that applications of chitosan-based films or coatings or treatments have resulted in shelf life extension of fresh produce, meat products, bread, and dairy products such as cheese which has been highlighted. • Consumers demand for healthy and safe food with minimal synthetic inputs. • Chitosan is an antimicrobial biopolymer derived from fish processing wastes. • Chitosan has been effectively used in food packaging applications. • Chitosan film or coating or treatment enhances shelf life of perishable food. • Chitosan nanocomposites are emerging antimicrobial food packaging alternatives. [ABSTRACT FROM AUTHOR]

Abstract: In this study, hydrothermally prepared magnetic α-Fe2O3 nanoparticles were dispersed in chitosan (CH) solution to fabricate nanocomposite film. X-ray diffraction (XRD) patterns indicated that the α-Fe2O3 nanoparticles were pure α-Fe2O3 with rhombohedral structures, and the fabrication of CH did not result in a phase change. The scanning electron microscopy (SEM) and transmission electron microscope (TEM) results showed that the hexagonal and spherical monodispersed α-Fe2O3 nanoparticles were encapsulated into the spherical dumb shaped CH-α-Fe2O3 nanocomposite film with a mean diameter of ∼87 and ∼110nm respectively. The α-Fe2O3 nanoparticles and CH-α-Fe2O3 nanocomposite film were also characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM). Magnetic measurements revealed that the saturated magnetization (Ms) and remanent magnetization (Mr) of the pure α-Fe2O3 nanoparticles reached 0.573emu/g and 0.100emu/g respectively and the nanoparticles showed the characteristics of weak ferromagnetic before and after coating with CH. [Copyright &y& Elsevier]

Chitosan (CS), an edible and non-toxic natural biopolymer, has been widely used in food preservation attributed to its intrinsic antimicrobial, biodegradable, and excellent film-forming properties. In this work, we report photocatalyst-loaded chitosan coating on commercial polyethylene (PE) film with enhanced antimicrobial properties for food packaging application. To improve the chemical stability of zinc oxide (ZnO) photocatalyst in acidic chitosan matrix, a thin layer (1–5 nm) of amorphous tin oxide (SnO x) was coated on ZnO nanoparticles. Consequently, the charge transfer efficiency of ZnO is improved and most of the surface defects are retained according to the studies of UV–Vis and fluorescence spectroscopy. The thin SnO x coating on ZnO was observed by high-resolution transmission electron microscopy (HRTEM) and its effects on crystallinity and particle size of ZnO were examined using X-ray diffraction (XRD) and particle sizer, respectively. The addition of ZnO@SnO x particles in chitosan coating increases water contact angle (WCA) and enhances thermal stability of chitosan coating. The antimicrobial activity of chitosan, ZnO-SnO x nanoparticles, and CS-ZnO@SnO x coated PE films were examined against both Gram-negative (E. coli , A. faecalis) and Gram-positive (S. aureus , B. subtilis) bacteria. Compared to the limited antimicrobial effects of chitosan, ZnO-SnO x demonstrates an improved inhibition effect on bacterial growth over 48 h period under light. For the CS-ZnO@SnO x nanocomposite coated PE films, no inhibition zone was observed due to the limitation of disc diffusion method. Meanwhile, there were no bacterial colonies found to develop on the film, rendering this CS nanocomposite coating a good candidate for food packaging applications. [Display omitted] • Chemical instability of ZnO is circumvented by a thin layer of SnO x coating. • Thermal stability and hydrophobicity of chitosan coating were enhanced by ZnO@SnO x. • Chitosan-ZnO@SnO x was spray-coated on polyethylene film. • No bacteria growth on chitosan-ZnO@SnO x -coated polyethylene film [ABSTRACT FROM AUTHOR]

Abstract: Recently, increasing attention has been paid to develop and test films with antimicrobial properties in order to improve food safety and shelf life. Active biomolecules such as chitosan and its derivatives have a significant role in food application area in view of recent outbreaks of contaminations associated with food products as well as growing concerns regarding the negative environmental impact of packaging materials currently in use. Chitosan has a great potential for a wide range of applications due to its biodegradability, biocompatibility, antimicrobial activity, non-toxicity and versatile chemical and physical properties. Thus, chitosan based films have proven to be very effective in food preservation. The presence of amino group in C2 position of chitosan provides major functionality towards biotechnological needs, particularly, in food applications. Chitosan based polymeric materials can be formed into fibers, films, gels, sponges, beads or even nanoparticles. Chitosan films have shown potential to be used as a packaging material for the quality preservation of a variety of food. Besides, chitosan has widely been used in antimicrobial films to provide edible protective coating, in dipping and spraying for the food products due to its antimicrobial properties. Chitosan has exhibited high antimicrobial activity against a wide variety of pathogenic and spoilage microorganisms, including fungi, and Gram-positive and Gram-negative bacteria. The present review aims to highlight various preparative methods and antimicrobial activity including the mechanism of the antimicrobial action of chitosan based films. The optimisation of the biocidic properties of these so called biocomposites films and role of biocatalysts in improvement of quality and shelf life of foods has been discussed. [Copyright &y& Elsevier]

To reduce undesired iron leaching in Fenton reaction and to realize reusability of catalyst, chitosan-coated activated carbon cloth support loaded with nano zero-valent iron (ACC–CH–nZVI) was applied as a heterogeneous Fenton catalyst to treat melanoidin wastewater. Chitosan coating on ACC by chemical crosslinking results in 6% chitosan on ACC subsequently loading 3.5% iron. At optimum conditions, ACC–CH–nZVI leads to 88.4% and 76.2% of color and chemical oxygen demand (COD) removal, respectively, upon treating synthetic melanoidin wastewater of 8000 mg/l COD. The corresponding weight ratio of consumed H 2 O 2 to COD is 1.02, far below the stoichiometric ratio 2.125, indicating the economic value of this catalyst. Reusability of ACC–CH–nZVI is demonstrated for five cycles of treatment with minimal iron leaching (<2%). The high removal efficiency and very low levels of iron leaching suggests that ACC–CH–nZVI is a highly efficient and cost-effective catalyst for Fenton-like oxidation of non-biodegradable organic wastes in water. Image 1 • Activated carbon cloth (ACC) and chitosan (CH) supported nano zero-valent iron (nZVI). • ACC–CH–nZVI catalyst leads to high color and COD removal from melanoidin wastewater. • The highest removal efficiency was obtained at pH 3 with low consumption of H 2 O 2. • ACC–CH–nZVI catalyst exhibits excellent reusability. • Very low (<2%) iron leaching for ACC–CH–nZVI catalyst in five cycles of treatment. [ABSTRACT FROM AUTHOR]