Preparation, characterization and antioxidant activity of silk peptides grafted carboxymethyl chitosan

Asterias Rolleston starfish gonad lipids: A novel source of Omega-3 fatty acids - assessment of major components and their antioxidant activities

The major lipids and antioxidant activities of Asterias rolleston gonad lipids were evaluated systematically. Major lipids of A. Rolleston gonad lipids were triacylglycerols (TAGs) and phospholipids (PLs). Total lipids were composed of 15.62% of polyunsaturated fatty acids (PUFAs), and 40.81% of monounsaturated fatty acids (MUFAs). The most abundant PUFA were C20:5n-3 (EPA) (6.28%) and C22:6n-3 (DHA) (5.80%). Predominantly composed of phosphatidylcholine (PC) and phosphatidylethanolamine (PE), polar lipids were rich in PUFAs and could contain up to 34.59% EPA and DHA, and PE and PI (phosphatidylinositol) were also found to be the main carriers of EPA and ARA (arachidonic acid) in polar lipids. The MUFA and PUFA of Sn-2 in TAG are 39.72% and 30.37%, respectively. A total of 64 TAG species were identified, with Eo-P-M, Eo-Eo-M, and M-M-Eo being the main TAGs components. Moreover, A. rollestoni gonad lipids exhibited potent radical scavenging activities and reducing power in a dose-dependent manner.

Hierarchical Porous Aerogels With Multiple Adsorptive Interactions for Dye Wastewater Purification

Aerogels present a huge potential for removing organic dyes from printing and dyeing wastewater (PDW). However, the preparation of aerogels with multiple dye adsorption capabilities remains a challenge, as many existing aerogels are limited to adsorbing only a single type of dye. Herein, a composite aerogel (CG/T-rGO) with the addition of carboxymethyl chitosan, gelatin and tannic acid reduced graphene oxide (T-rGO) was synthesized by freeze-drying technology. The electrostatic interactions between dye molecular and GEL/CMCS (CG) networks, as well as the supramolecular interactions (H-bonds, electrostatic interactions and π-π stacks) between T-rGO, have endowed the aerogel with the ability to adsorb multiple types of dye, such as methylene blue (MB) and methyl orange (MO). Results exhibited that the prepared CG/T-rGO aerogel possessed strong mechanical strength and a porous 3D network structure with a porosity of 96.33 %. Using MB and MO as adsorbates, the adsorption capacity (88.2 mg/g and 66.6 mg/g, respectively) and the mechanism of the CG/T-rGO aerogel were investigated. The adsorption processes of aerogel for MB and MO were shown to follow the pseudo-second-order kinetic model and Langmuir isotherm model, indicating the chemical adsorption of a monolayer. The proposed aerogel in this work has promising prospects for dye removal from PDW.

Use of Chitosan as a Precursor for Multiple Applications in Medicinal Chemistry: Recent Significant Contributions

Chitosan (CS) is a polymer made up of mainly deacetylated β-1,4 D-glucosamine units, which is part of a large group of D-glucosamine oligomers known as chitooligosaccharides, which can be obtained from chitin, most abundant natural polymer after cellulose and central component of the shrimp exoskeleton. It is known that it can be used for the development of materials, among which its use stands out in wastewater treatment (removal of metal ions, dyes, and as a membrane in purification processes), food industry (anti-cholesterol and fat, packaging material, preservative, and food additive), agriculture (seed and fertilizer coating, controlled release agrochemicals), pulp and paper industry (surface treatment, adhesive paper), cosmetics (body creams, lotions, etc.), in the engineering of tissues, wound healing, as excipients for drug administration, gels, membranes, nanofibers, beads, microparticles, nanoparticles, scaffolds, sponges, and diverse biological ones, specifically antibacterial and antifungal activities. This article reviews the main contributions published in the last ten years regarding the use and application of CS in medical chemistry. The applications exposed here involve regenerative medicine in the design of bioprocesses and tissue engineering, Pharmaceutical sciences to obtain biomaterials, polymers, biomedicine, and the use of nanomaterials and nanotechnology, toxicology, and Clinical Pharmaceuticals, emphasizing the perspectives and the direction that can take research in this area.

Enhanced biological activities of coumarin-functionalized polysaccharide derivatives: Chemical modification and activity assessment

Natural polysaccharides are abundant and renewable resource, but their applications are hampered by limited biological activity. Chemical modification can overcome these drawbacks by altering their structure. Three series of polysaccharide derivatives with coumarins were synthesized to obtain polysaccharide derivatives with enhanced biological activity. The biological activities were tested, including antioxidant property, antifungal property, and antibacterial property. Based on the results, the inhibitory properties of the coumarin-polysaccharide derivatives were significantly improved over the raw polysaccharide. The IC50 of the inhibition of DPPH, ABTS•+, and superoxide (O2•-) radical-scavenging was 0.06-0.15 mg/mL, 2.3-15.9 μg/mL, and 0.03-0.25 mg/mL, respectively. Compared with the raw polysaccharides, coumarin- polysaccharide derivatives exhibited higher efficacy in inhibiting the growth of tested phytopathogens, showing inhibitory indices of 60.0-93.6 % at 1.0 mg/mL. Chitosan derivatives with methyl and chlorine (Compound 10B and 10C) exhibited significant antibacterial activity against S. aureus (MIC = 31.2 μg/mL), E. coli (MIC = 7.8 μg/mL), and V. harveyi (MIC = 15.6 μg/mL), respectively. The results of the cytotoxicity assay showed no observed cytotoxicity when the RAW 264.7 cells were incubated with the synthesized polysaccharide derivatives at the tested concentrations.

Exploring the potential of Rhizopus oryzae AUMC14899 as a novel endophytic fungus for the production of L-tyrosine and its biomedical applications

BACKGROUND

A significant threat to the public's health is the rise in antimicrobial resistance among numerous nosocomial bacterial infections. This may be a detriment to present initiatives to enhance the health of immune-compromised patients. Consequently, attention has been devoted to exploring new bioactive compounds in the field of drug discovery from endophytes. Therefore, this study is the first on the production of L-tyrosine (LT) as a promising bio-therapeutic agent from endophytic fungi.

RESULTS

A new endophytic fungal isolate has been identified for the first time as Rhizopus oryzae AUMC14899 from Opuntia ficus-indica (L.) and submitted to GenBank under the accession number MZ025968. Separation of amino acids in the crude extract of this fungal isolate was carried out, giving a higher content of LT, which is then characterized and purified. LT exhibited strong antibacterial and anti-biofilm activities against multidrug-resistant Gram-negative and Gram-positive bacteria. The recorded minimum inhibitory concentration (MIC) values ranged from 6 to 20 µg/ml. In addition, LT caused a strong reduction in biofilm formation and disrupted the preformed biofilm. Moreover, results indicated that LT supported cell viability, evidencing hemocompatibility and no cytotoxicity.

CONCLUSION

Our findings suggest that LT has potential as a therapeutic agent due to its potential antibacterial, anti-biofilm, hemocompatibility, and lack of cytotoxic activities, which may also increase the range of therapy options for skin burn infections, leading to the development of a novel fungal-based drug.

Multifunctional role of chitosan in farm animals: a comprehensive review

The deacetylation of chitin results in chitosan, a fibrous-like material. It may be produced in large quantities since the raw material (chitin) is plentiful in nature as a component of crustacean (shrimps and crabs) and insect hard outer skeletons, as well as the cell walls of some fungi. Chitosan is a nontoxic, biodegradable, and biocompatible polygluchitosanamine that contains two essential reactive functional groups, including amino and hydroxyl groups. This unique chemical structure confers chitosan with many biological functions and activities such as antimicrobial, anti-inflammatory, antioxidative, antitumor, immunostimulatory and hypocholesterolemic, when used as a feed additive for farm animals. Studies have indicated the beneficial effects of chitosan on animal health and performance, aside from its safer use as an antibiotic alternative. This review aimed to highlight the effects of chitosan on animal health and performance when used as a promising feed additive.

Preparation, biocompatibility, and wound healing effects of O-carboxymethyl chitosan nonwoven fabrics in partial-thickness burn model

This study was aimed at preparing O-carboxymethyl chitosan (CM-CTS) fabrics, and examining the wound healing effects on partial-thickness burn. The functional polysaccharides were produced from chitosan needle-punched nonwovens reacted with chloroacetic acid. Then the biocompatibility and biological functions were evaluated through fibroblast L-929 and SD rats. CM-CTS fabrics were obtained with elongation at break more than 42%, tensile strength reaching 0.65 N/mm², and water vapor transmission rate about 2600 g/m²∙24 h. Moreover, CM-CTS fabrics could effectively promote the mouse L-929 migration in vitro. CM-CTS fabrics yielded satisfactory results in angiogenesis, collagen deposition, interleukin-6 content, transforming growth factor level and healing rate, which were superior to the positive control and model groups after rats suffering with partial-thickness burn. In conclusion, CM-CTS fabrics possessed proper mechanical properties, air permeability, favorable biocompatibility, acceleration on fibroblasts migration and healing capacity for partial-thickness burn injury, and owned good potential as high-quality wound dressing.

Sources, chemical synthesis, functional improvement and applications of food-derived protein/peptide-saccharide covalent conjugates: a review

Proteins/peptides and saccharides are two kinds of bioactive substances in nature. Recently, increasing attention has been paid in understanding and utilizing covalent interactions between proteins/peptides and saccharides. The products obtained through covalent conjugation of proteins/peptides to saccharides are shown to have enhanced functional attributes, such as better gelling property, thermostability, and water-holding capacity. Additionally, food-derived protein/peptide-saccharide covalent conjugates (PSCCs) also have biological activities, such as antibacterial, antidiabetic, anti-osteoporosis, anti-inflammatory, anti-cancer, immune regulatory, and other activities that are widely used in the functional food industry. Moreover, PSCCs can be used as packaging or delivery materials to improve the bioavailability of bioactive substances, which expands the development of food-derived protein and saccharide resources. Thus, this review was aimed to first summarize the current status of sources, classification structures of natural PSCCs. Second, the methods of chemical synthesis, reaction conditions, characterization and reagent formulations that improve the desired functional characteristics of food-derived PSCCs were introduced. Third, functional properties such as emulsion, edible films/coatings, and delivery of active substance, bio-activities such as antioxidant, anti-osteoporosis, antidiabetic, antimicrobial of food-derived PSCCs were extensively discussed.

Effects of citronellol grafted chitosan oligosaccharide derivatives on regulating anti-inflammatory activity

In order to improve the anti-inflammatory activity of chitosan oligosaccharide (COS), chitosan oligosaccharide graft citronellol derivatives (COS-g-Cit1-3) were successfully synthesized via grafting citronellol (Cit) onto COS backbone. The degrees of substitution (DS) of COS-g-Cit1-3 were 0.165, 0.199 and 0.182, respectively. The structure of COS-g-Cit1-3 was confirmed by UV-vis, FT-IR, ¹H NMR and elemental analysis. The in vivo anti-inflammatory activity evaluation results displayed that COS-g-Cit1-3 drastically reduced the paw swelling, and the oedema inhibitions were 22.58 %, 29.03 % and 25.81 %, respectively. The results indicated that the anti-inflammatory effects of COS-g-Cit1-3 were significantly higher than COS and COS-g-Cit2 exhibited the highest anti-inflammatory ability. The results also presented that COS-g-Cit1-3 reduced the expression levels of TNF-α by promoting the secretion of IL-4 and IL-10. Moreover, western blot analysis data proved that COS-g-Cit1-3 inactivated the NF-κB signaling pathway via inhibiting the phosphorylation of p65, IKBα and IKKβ.

Development of Chitosan/Peptide Films: Physical, Antibacterial and Antioxidant Properties

Chitosan/peptide films were prepared by incorporating peptides (0.4%, w/v) from soy, corn and caseins into chitosan films. The presence of peptides significantly affected the physical, antibacterial and antioxidative properties of chitosan films. Among these films, those containing corn peptide showed the best water vapor barrier properties, and the tensile strength and elongation at break increased to 24.80 Mpa and 23.94%, respectively. Characterization of surface hydrophobicity and thermal stability suggested the strongest intermolecular interactions between corn peptides and chitosan. Moreover, films containing casein peptides showed the highest antibacterial activity and radical scavenging activity. The DPPH scavenging rate of films containing casein peptides reached 46.11%, and ABTS scavenging rate reached 66.79%. These results indicate the chitosan/peptide films may be promising food packaging materials.

Chitosan oligosaccharide-g-linalool polymer as inhibitor of hyaluronidase and collagenase activity

In this study, chitosan oligosaccharide (COS) was modified by grafting Linalool (Lin) on its backbone to improve its anti-inflammatory activity. By changing the molar ratios of COS to Lin, three different degrees of substitution COS-g-Lin1-3 were prepared. The degrees of substitution of derivatives were 0.65, 0.80 and 1.14 respectively. The structure of COS-g-Lin1-3 were characterized by UV-vis, FT-IR, ¹H NMR and elemental analysis in order to show the COS-g-Lin1-3 successfully synthesized. Besides, the thermal stability, solubility, pH stability as well as crystallinity were also investigated. The results revealed that the derivatives exhibited higher thermal stability and more remarkable anti-inflammatory property against hyaluronidase and collagenase than that of COS. The good biocompatibility made this novel material a promising and effective compound for anti-inflammatory applications.

A novel "hot spring"-mimetic hydrogel with excellent angiogenic properties for chronic wound healing

The treatment of chronic wounds is a major challenge in regenerative medicine, and angiogenesis is known to be critical for chronic wound healing. Hot springs with temperature in the range of 30-45 °C can promote blood circulation, and some hot spring elements including iron and silicon are also known to be active in promoting angiogenesis. Inspired by the hot spring function, we designed a novel bioactive photothermal hydrogel with "hot spring effect" based on fayalite (FA) and N, O-carboxymethyl chitosan (NOCS), which releases bioactive ions and has heating function to create hot ion environment in wound area. The hot spring-mimetic hydrogel showed significant enhancement of angiogenesis and chronic wound healing in vivo due to the in situ heating through photothermal effect combined with the bioactive ions (Fe²⁺ and SiO₄^4-) released from the hydrogel. It is further confirmed that the synergetic effect of the mild heating and bioactive ions on angiogenesis was mainly because of the activation of different angiogenic factors and signaling pathways. Our study suggests that the hot spring-mimetic approach may be an effective strategy to design bioactive materials for promoting angiogenesis and tissue regeneration.

Effects of carboxymethyl chitosan oligosaccharide on regulating immunologic function and inhibiting tumor growth

Herein, the effects of carboxymethyl chitosan oligosaccharide (CM-COS) on regulating immunologic function and inhibiting hepatocellular tumor growth were evaluated. Results showed that CM-COS caused dramatic viability loss of hepatocellular carcinoma BEL-7402 with non-toxicity towards normal liver L-02 cells. CM-COS repressed tumor growth of hepatoma-22, and elevated the spleen index and thymus index of tumor-bearing mice. Contents of VEGF and MMP-9 were significantly down-regulated by CM-COS. Histological analyses revealed that CM-COS promoted tumor cell necrosis and produced no significant toxicity to spleen tissues. Moreover, expressions of Caspase-3 in tumor tissues and IL-2 in spleen tissues were significantly activated by CM-COS. Additionally, in vitro cell viability, phagocytic capability and NO production of mouse peritoneal macrophages exposed to CM-COS were significantly higher. CM-COS remarkably increased the in vivo phagocytosing capacity of peritoneal macrophages of Kunming mice. Taken together, our findings suggested that CM-COS might be potentially effective and non-toxic candidate as anti-hepatoma agents.

Synthesis and characterization of L-tyrosine-conjugated quaternary ammonium salt chitosan and their cytocompatibility as a potential tissue engineering scaffold

A novel amino acid-modified biomacromolecule was designed and synthesized as the quaternary ammonium salt chitosan grafted-tyrosine (CA-g-Tyr) suitable for biomedical applications. L-tyrosine was grafted onto the quaternary ammonium salt chitosan (CA) by N-(3-dimethylaminopropy)-N-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The chemical structure of CA-g-Tyr was confirmed by Fourier transform infrared (FTIR) spectroscopy and ¹³C-NMR. The change in the crystalline structure after the graft was characterized by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). The surface wettability and moisturizing performance of the CA-g-Tyr were also characterized. The CA-g-Tyr film possessed good hydrophilicity, and the mechanical tensile experiments showed that the introduction of tyrosine gave CA mechanical properties more suitable for blood vessel. Cell experiments showed that the endothelial cells can adhere and proliferate better on the surface of a CA-g-Tyr film than CA. The results confirm the favorable properties and biocompatibility of CA-g-Tyr with potential applications as scaffolds for tissue engineering.

Significantly enhanced antioxidant activity of chitosan through chemical modification with coumarins

A new class of chitosan derivatives possessing coumarins was synthesized to improve the antioxidant activity of chitosan.

Radical Scavenging Activities of Novel Cationic Inulin Derivatives

Many saccharides are attractive targets for biomaterial applications, due to their abundance, biocompatibility, and biodegradability. In this article, a synthesis process of 6-N-substituted cationic inulin derivatives, including 6-pyridyl-6-deoxyinulin bromide (PIL), 6-(2-amino-pyridyl)-6-deoxyinulin bromide (2APIL), 6-(3-amino-pyridyl)-6-deoxyinulin bromide (3APIL), 6-(4-amino-pyridyl)-6-deoxyinulin bromide (4APIL), 6-(2,3-diamino-pyridyl)-6-deoxyinulin bromide (2,3DAPIL), 6-(3,4-diamino-pyridyl)-6-deoxyinulin bromide (3,4DAPIL), and 6-(2,6-diamino-pyridyl)-6-deoxyinulin bromide (2,6DAPIL) was described. The C₆-OH of inulin was first activated by PPh₃/N-bromosuccinimide (NBS) bromination. Then, pyridine and different kinds of amino-pyridine groups (different position and different numbers of amino) were grafted onto inulin, respectively, via nucleophilic substitution. Then, we confirmed their structure by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. After this, their radical scavenging activities against hydroxyl radical and diphenylpicryl phenylhydrazine (DPPH) radical were tested in vitro. Each derivative showed a distinct improvement in radical scavenging activity when compared to inulin. The hydroxyl-radical scavenging effect decreased in the following order: 3APIL > PIL > 3,4DAPIL > 4APIL > 2,3DAPIL > 2,6DAPIL > 2APIL. Amongst them, 3APIL revealed the most powerful scavenging effect on hydroxyl radicals, as well as DPPH radicals. At 1.6 mg/mL, it could completely eliminate hydroxyl radicals and could clear 65% of DPPH radicals. The results also showed that the steric hindrance effect and the substitute position of the amino group had an effect on the radical scavenging activity. Moreover, the application prospects of inulin derivatives as natural antioxidant biomaterials are scientifically proven in this paper.

Pharmaceutical Potential of a Novel Chitosan Derivative Schiff Base with Special Reference to Antibacterial, Anti-Biofilm, Antioxidant, Anti-Inflammatory, Hemocompatibility and Cytotoxic Activities

PURPOSE

Chitosan and its derivatives possess several unique properties relevant in the field of pharmaceutics and medicinal chemistry. This study aimed to evaluate the pharmaceutical performance of an innovative chitosan derivative, methyl acrylate chitosan bearing p-nitrobenzaldehyde (MA*CS*pNBA) Schiff base.

METHODS

The antibacterial activity of MA*CS*pNBA was tested against multi-drug resistant (MDR) Gram-negative and Gram-positive bacteria using agar-well diffusion method. Anti-biofilm formation was analyzed using a microtitre plate. Antioxidant assays were performed to assess the scavenging activity of MA*CS*pNBA using DPPH, hydrogen peroxide, superoxide together with its reducing power activity. Anti-inflammatory activity was evaluated by albumin denaturation, membrane stabilization, and proteinase inhibition methods. MA*CS*pNBA was tested for its hemolytic efficiency on human erythrocytes. Cytotoxicity of MA*CS*pNBA was evaluated by MTT assay.

RESULTS

MA*CS*pNBA showed a significant performance as an antibacterial candidate against MDR bacteria, anti-biofilm, antioxidant and anti-inflammatory biomaterial, evidencing hemocompatibility and no cytotoxicity. It exhibited a significant negative correlation with biofilm formation by the MDR-PA-09 strain. Biological activities were found to be significantly concentration-dependent.

CONCLUSIONS

the newly chitosan derivative MA*CS*pNBA showed to be promising for pharmaceutical applications, expanding the treatment ways toward skin burn infections since it allied excellent antibacterial, anti-biofilm, antioxidant, anti-inflammatory, hemocompatibility and absence of cytotoxic activities.

Biocatalytic synthesis of acylated derivatives of troxerutin: their bioavailability and antioxidant properties in vitro

Background

Flavonoid glycosides have many beneficial effects on health, but these bioactivities tend to decrease after oral administration owing to their poor lipophilicity. In this study, a facile whole-cell-based method was developed for selective preparation of monoester or diester of troxerutin, a flavonoid derivative. In addition, the bioavailabilities and antioxidant properties of troxerutin and its acylated derivatives were also investigated in cells.

Results

Pseudomonas aeruginosa and Pseudomonas stutzeri cells showed high catalytic efficiency (substrate conversion > 90%) and different preferences for troxerutin, resulting in the production of its monoester (TME) and diester (TDE), respectively. The logP values of troxerutin, TME, and TDE were − 2.04 ± 0.10, − 0.75 ± 0.08, and 1.51 ± 0.05 and their P_app values were 0.34 × 10⁻⁶ ± 0.05, 0.99 × 10⁻⁶ ± 0.12, and 1.54 × 10⁻⁶ ± 0.17 cm/s, respectively. The results of hydroxyl radical, ABTS, and ORAC assays indicated that the antiradical activities of acylated derivatives did not exceed that of troxerutin, but showed higher inhibition effects upon 2,2′-azobis(2-amidinopropane) dihydrochloride-induced erythrocyte hemolysis than that of troxerutin (P < 0.05).

Conclusion

A facile and efficient whole-cell biocatalysis method was developed to synthesize troxerutin-acylated derivatives, markedly enhancing the bioavailability and antioxidant activities of troxerutin in cells. Additionally, the mechanism underlying the observed difference in the antioxidant activities of troxerutin and its esters was ascribed to both their free radical scavenging abilities and distribution on the cell membrane surface.

Electronic supplementary material

The online version of this article (10.1186/s12934-018-0976-x) contains supplementary material, which is available to authorized users.

Synthesis and antioxidant action of chitosan derivatives with amino-containing groups via azide-alkyne click reaction and N-methylation

Amino functionality has been paid growing attention in chemical modification of polysaccharides due to their potential biomedical applications. Here, the preparation of novel antioxidant materials based on chitosan derivatives bearing amino-containing groups equipped with 1,2,3-triazole and 1,2,3-triazolium by Cuprous-catalyzed azide-alkyne cycloaddition and N-methylation was described for the first time. The structural characteristics of the synthesized derivatives were examined by FTIR, ¹H NMR, and elemental analysis. The antioxidant activities of the chitosan derivatives were assessed in vitro. The results indicated that chitosan derivatives bearing 1,2,3-triazoles displayed superior antioxidant activity over pristine chitosan, especially against superoxide anion radical. Moreover, antioxidant efficiency of chitosan derivatives further enhanced after N-methylation of 1,2,3-triazole moieties with iodomethane, which is comparative to that of ascorbic acid. Notably, of all chitosan derivatives bearing 1,2,3-triazole or 1,2,3-triazolium moieties, acylhydrazine-functionalized and amino-functionalized chitosan showed the stronger antioxidant capacity than hydroxyl-modified chitosan at the test concentration. Besides, the cytotoxicities of them were also evaluated in vitro on HaCaT cells. These results suggested that amino and acylhydrazine-functionalized chitosan derivatives with 1,2,3-triazolium could be used as novel antioxidant biomaterials.

Synthesis, characterization, and the antioxidant activity of N,N,N-trimethyl chitosan salts

Chitosan, possessing excellent properties, has been drawing broad attention. For the further utilization of chitosan, chemical modification is performed in improving its water solubility and the bioactivities. In the current study, four N,N,N-trimethyl chitosan salts, including N,N,N-trimethyl chitosan citrate (TMCSCi), N,N,N-trimethyl chitosan acetylsalicylate (TMCSAc), N,N,N-trimethyl chitosan ascorbate (TMCSAs), and N,N,N-trimethyl chitosan gallate (TMCSGa), were prepared via N,N,N-trimethyl chitosan iodide (TMCSI). The as-prepared products were characterized by FT-IR and ¹H NMR. Meanwhile, the degrees of substitution were calculated by elemental analysis results. Furthermore, scavenging activities (against DPPH radicals and superoxide radicals) test and reducing power test were selected to evaluate the antioxidant property of N,N,N-trimethyl chitosan salts in vitro. The results indicated that TMCSAs and TMCSGa displayed excellent activity, probably due to the enhancement of ascorbate and gallate in antioxidant activity. However, because of the weak antioxidant property of citrate and acetylsalicylate, the activity was lower for TMCSCi and TMCSAc. For example, in the DPPH radicals scavenging assay, the scavenging rates of chitosan, TMCSI, TMCSCi, TMCSAc, TMCSAs, and TMCSGa were 25.22, 84.11, 6.90, 2.70, 94.92, and 96.75% at 0.4 mg/mL, respectively. Generally, TMCSAs and TMCSGa could be regarded as a potential source of antioxidants.

Novel Water Soluble Chitosan Derivatives with 1,2,3-Triazolium and Their Free Radical-Scavenging Activity

Chitosan is an abundant and renewable polysaccharide, which exhibits attractive bioactivities and natural properties. Improvement such as chemical modification of chitosan is often performed for its potential of providing high bioactivity and good water solubility. A new class of chitosan derivatives possessing 1,2,3-triazolium charged units by associating “click reaction” with efficient 1,2,3-triazole quaternization were designed and synthesized. Their free radical-scavenging activity against three free radicals was tested. The inhibitory property and water solubility of the synthesized chitosan derivatives exhibited a remarkable improvement over chitosan. It is hypothesized that triazole or triazolium groups enable the synthesized chitosan to possess obviously better radical-scavenging activity. Moreover, the scavenging activity against superoxide radical of chitosan derivatives with triazolium (IC₅₀ < 0.01 mg mL⁻¹) was more efficient than that of derivatives with triazole and Vitamin C. In the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radical-scavenging assay, the same pattern were observed, which should be related to the triazolium grafted at the periphery of molecular chains.

In situ biomineralization by silkworm feeding with ion precursors for the improved mechanical properties of silk fiber

Possessing excellent biocompatibility, biodegradability and good reactive activity, silk fiber has been attracting great attention in biomedicine including surgical suture, drug delivery and tissue engineering. So far, several protocols have been developed to further improve the mechanical properties of the silk fiber. In current study, a novel in suit biomineralization strategy was developed to produce nano-hydroxyapatite (HA) strengthened silk fiber based on the natural alkaline condition in the body of silkworm by feeding the silkworm with ion precursors of Ca²⁺ and PO₄^3- ions. Our observation proved that nanocomposite silk fiber contained more α-helix and random coil structures and fewer β-sheets. Tensile test showed that such obtained silk fiber has superior mechanical properties compared to normal silk fiber. To the best of our knowledge, no attempts have been made to fabricate the nanocomposite SF by in situ biomineralization and such protocol established in the current study may shed light on the investigation of nanoparticles reinforced silk fiber organisms of Bombyx mori.