Biological activities of chitosan and chitooligosaccharides

Potential Medical Applications of Chitooligosaccharides

Chitooligosaccharides, also known as chitosan oligomers or chitooligomers, are made up of chitosan with a degree of polymerization (DP) that is less than 20 and an average molecular weight (MW) that is lower than 3.9 kDa. COS can be produced through enzymatic conversions using chitinases, physical and chemical applications, or a combination of these strategies. COS is of significant interest for pharmacological and medical applications due to its increased water solubility and non-toxicity, with a wide range of bioactivities, including antibacterial, anti-inflammatory, anti-obesity, neuroprotective, anticancer, and antioxidant effects. This review aims to outline the recent advances and potential applications of COS in various diseases and conditions based on the available literature, mainly from preclinical research. The prospects of further in vivo studies and translational research on COS in the medical field are highlighted.

Potential synbiotic effects of a Bacillus mixture and chitosan on growth, immune responses and VP(AHPND) resistance in Pacific white shrimp (Litopenaeus vannamei, Boone, 1931)

The potential synbiotic effects of a Bacillus mixture and chitosan on growth, immune responses and disease resistance against Vibrio parahaemolyticus, the causative agent of acute hepatopancreatic necrosis disease (AHPND) in Pacific white shrimp, were intensively investigated. Three effective strains of Bacillus amyloliquefaciens (A), Bacillus pumilus (P) and Bacillus subtilis (S) were mixed in pairs at a ratio of 5 × 10⁸:5 × 10⁸ CFU/kg diet and coated with the prebiotic chitosan (C) at a concentration of 20 mL/kg diet. Five different feed treatments were used to feed experimental shrimp for 5 weeks: control (control, no synbiotics), chitosan (coat, C) and the synbiotic treatments PAC, PSC and ASC. At week 5, the final length, final weight gain, weight gain, length, average daily gain, specific growth rate and feed conversion ratio, measured as growth parameters, were significantly upregulated in the PSC and ASC groups compared with the control and coat groups (P < 0.05). This result was consistent with the expression analysis of two growth-related genes (Rap-2a and GF-II) in the hepatopancreas and intestines of treated shrimp, as determined using qRT-PCR. The prebiotic chitosan and synbiotics PAC, PSC and ASC strongly induced significant differences in the expression of the Rap-2a and GF-II genes in the target organs compared with the expression in the control group at various time points (P < 0.05). Additionally, application of the synbiotic treatments also significantly enhanced the hepatopancreas characteristics and epithelial and intestinal wall thicknesses of the shrimp compared with the control. Interestingly, all the synbiotic treatments elevated phagocytic activity significantly at weeks 3 and 5 compared with that in the other groups. qRT-PCR analysis of immune-related genes also indicated that the prebiotic group and all synbiotic groups showed strong expression of anti-lipopolysaccharide (ALF) and prophenoloxidase (proPO) genes in the intestine. Finally, the synbiotic groups PAC, PSC and ASC exhibited stronger VP_AHPND resistance at 120 h after exposure than the chitosan coat and control groups, with survival rates of 41.7 ± 11.55, 41.7 ± 0.00, 52.8 ± 5.77, 30.6 ± 15.28 and 22.2 ± 5.77%, respectively (P < 0.05). Based on the obtained information, all synbiotics were recommended for improved growth and immune responses, while ASC was the best for disease resistance against VP_AHPND in Pacific white shrimp.

Dietary Fructooligosaccharides Effectively Facilitate the Production of High-Quality Eggs via Improving the Physiological Status of Laying Hens

The focus of this study was to investigate the influence of prebiotics, such as fructooligosaccharides (FOS), on laying performance, egg quality, apparent fecal amino acid digestibility, jejunal morphology, hematological indices, immunological response, and antioxidant capacity in laying hens. A total of 216 healthy Hy-Line Brown laying hens aged 30 weeks were randomly assigned to one of three dietary treatments: basal diet, basal diet supplemented with 0.3 percent FOS, or 0.6 percent FOS. For 84 days, each treatment was fed the corresponding experimental diet. According to the findings, dietary supplementation with FOS enhanced laying performance and egg mass while lowering mortality rate. Albumen height, thick albumen content, Haugh unit, and eggshell thickness were also improved by the prebiotics. Prebiotics also boosted antioxidant status by increasing the activity of antioxidant enzymes, improved morphological development of the jejunum as demonstrated by significant increases in villi height, villi width, ratio of villi height to crypt depth, and reduced crypt depth. The prebiotics group showed a considerable increase in immunoglobulin M, G, and A (IgM, IgG, and IgA) levels, as well as a similar effect on complement proteins (C3). Furthermore, the apparent fecal amino acid digestibility of most essential amino acids was significantly enhanced. Conclusively, fructooligosaccharides at inclusion level of 0.6% efficiently enhanced laying performance and production of high-quality eggs while positively modulating amino acid digestibility, jejunal morphology, antioxidant status, and immune functions of the laying hens.

Oxidative stability of Pickering emulsions

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Oxidative stability of O/W Pickering emulsions depends on their interfacial layer.

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Solid particles can reduce Pickering emulsion oxidation by creating a thick interface.

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Manipulating the charge of the interface can control Pickering emulsion oxidation.

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Adding antioxidants to solid particles can reduce oxidation in Pickering emulsions.

In recent years, Pickering emulsions have been the focus of growing interest because of their possible role as alternatives to conventional emulsions. Some reviews have investigated the physical stability of Pickering emulsions, but the oxidative stability of these emulsions remains largely unexplored. In this review, the oxidation mechanism and factors affecting lipid oxidation rates in Pickering emulsions are discussed. Then, different food-grade solid particles are evaluated for their ability to stabilize Pickering emulsions. Finally, several strategies are reviewed for improving the oxidative stability of Pickering emulsions. These strategies are based on efforts to manipulate the physical and chemical properties of the interfacial layer, increase the concentration of antioxidants at the interfacial layer through incorporating them into solid particles, cause oil droplets to crowd at high packing fractions, trap oil droplets in a gel network and increase the viscosity of the continuous phase.

Transcriptomic and Metabolomic Analysis Reveal Possible Molecular Mechanisms Regulating Tea Plant Growth Elicited by Chitosan Oligosaccharide

Chitosan oligosaccharide (COS) plays an important role in the growth and development of tea plants. However, responses in tea plants trigged by COS have not been thoroughly investigated. In this study, we integrated transcriptomics and metabolomics analysis to understand the mechanisms of chitosan-induced tea quality improvement and growth promotion. The combined analysis revealed an obvious link between the flourishing development of the tea plant and the presence of COS. It obviously regulated the growth and development of the tea and the metabolomic process. The chlorophyll, soluble sugar, and amino acid content in the tea leaves was increased. The phytohormones, carbohydrates, and amino acid levels were zoomed-in in both transcript and metabolomics analyses compared to the control. The expression of the genes related to phytohormones transduction, carbon fixation, and amino acid metabolism during the growth and development of tea plants were significantly upregulated. Our findings indicated that alerted transcriptomic and metabolic responses occurring with the application of COS could cause efficiency in substrates in pivotal pathways and hence, elicited plant growth.

Chitosan: A review of molecular structure, bioactivities and interactions with the human body and micro-organisms

Chitosan has many desirable attributes e.g. antimicrobial properties and promoting wound healing, and is used in various applications. This article first discusses how degree of deacetylation (DD) and molecular weight (MW) impacts on what level of bioactivities chitosan manifests, then introduces the "molecular chain configuration" model to explain various possible mechanisms of antimicrobial interactions between chitosan with different MW and different types of bacteria. Similarly, the possible pathways of how chitosan reacts with cancer and the body's immune system to demonstrate immune and antitumor effects are also discussed by using this model. Moreover, the possible mechanisms of how chitosan enhances coagulation and wound healing are also discussed. With these beneficial bioactivities in mind, the application of chitosan in surgery, tissue engineering and oncology is outlined. This review concludes that as chitosan demonstrates many beneficial bioactivities via multiple mechanisms, it is an important polymer with a promising future in medicine.

Dietary fiber in bakery products: Source, processing, and function

Bakery products are prevalently consumed foods in the world, and they have been regarded as convenient dietary vehicles for delivering nutritive ingredients into people's diet, of which, dietary fiber (DF) is one of the most popular items. The food industry attempts to produce fiber-enriched bakery products with both increasing nutritional value and appealing palatability. As many new sources of DFs become available, and consumers are moving towards healthier diets, studies of using these DFs as functional ingredients in baked goods are becoming vast. Besides, the nutrition value of DF is commonly accepted, and many investigations have also revealed the health benefits of fiber-enriched bakery products. Thus, this chapter presents an overview of (1) trends in supplementation of DF from various sources, (2) impact of DF on dough processing, quality and physiological functionality of bakery products, and (3) technologies used to improve the compatibility of DF in bakery products.

Replacing Dietary Fish Meal with Defatted Black Soldier Fly (Hermetia illucens) Larvae Meal Affected Growth, Digestive Physiology and Muscle Quality of Tongue Sole (Cynoglossus semilaevis)

For solving the global shortage of fish meal (FM) supplies from fisheries, the black soldier fly (Hermetia illucens) has become a new protein alternative in aquatic feeds. The present study investigated the effects of dietary inclusion of defatted H. illucens larvae meal (DBLM) on growth, serum biochemical parameters, digestive function, and muscle quality of tongue sole (Cynoglossus semilaevis). The feeding experiment consisted of five experimental diets: a control diet based on FM protein (H0) and four DBLM diets, substituting 25% (H25), 50% (H50), 75% (H75), and 100% (H100) of FM. C. semilaevis (initial weight 563.48 ± 22.81 g) were randomly allocated over five treatments in quadruplicate. After 65 days of feeding, the weight gain rate (WGR), specific growth rate (SGR), and protein efficiency ratio (PER) were significantly higher in H0 and H25 groups with less feed conversion ratio (FCR) and feed intake (FI). The concentrations of serum ALT, TG, T-CHO, ALB, and GLO and their ratio (i.e., A/G) in the H25 group were also significantly higher than those in the other DBLM diet-feeding groups. The digestive enzyme activities first increased (from 25% to 75%) and then decreased (from 75%) with the increased level of DBLM in diets. Meanwhile, there were significant improvements in the thickness of the intestinal longitudinal muscle (LM), circular muscle (CM), columnar epithelium (CE), and lamina propria (LP) in H25 C. semilaevis compared to the control group (p < 0.05). The fish from the other DBLM diets groups presented significant reductions in the thicknesses of LM, CM, CE, and LP, as well as the length of microvilli (ML) in a dose-dependent manner (p < 0.05). However, the substitution of FM increased up to 50% would result in intestinal structural damage. Moreover, the proximate compositions, antioxidant and water holding capacity, and muscular structures of C. semilaevis fillets were all significantly affected after substituting 25% FM with DBLM (p < 0.05). Except for the dry matter, moisture, ash, crude fat, and protein contents were significantly higher in H25 C. semilaevis muscles. The SOD activity in the H0 group was significantly lower than that in the H25 group. The CAT activity in C. semilaevis muscles prominently reduced along with the increase in DBLM content in feeding diets (p < 0.05). The water holding capacity of C. semilaevis fillets was best in the H25 group. In summary, the optimum proportion of DBLM with FM for feeding C. semilaevis may be around 25%.

Repurposing of Marine Raw Materials in the Formulation of Innovative Plant Protection Products

Over the years, the growth of the world population has caused a huge agricultural production to support the population's needs. Since plant protection products are essential to preserve agricultural crops and to optimize vital plant processes, it is crucial to use more sustainable, biodegradable, and biocompatible raw materials, without harming the environment and human health. Although the development of new plant protection products is a costly process, the environmental benefits should be considered. In this context, marine raw materials obtained as byproducts of fishing industries, possessing a wide variety of physicochemical and biological properties, can serve as a promising source of such materials. They have a high potential for developing alternative and safe formulations for agricultural applications, not only as biocompatible excipients but also as effective and selective, or even both. It is also possible to promote a synergistic effect between an active substance and the biological activity of the marine polymer used in the formulation, enabling plant protection products with lower concentrations of the active substances. Thus, this review addresses the repurposing of marine raw materials for the development of innovative plant protection products, focusing on micro- and nanoparticulate formulations, to protect the environment through more ecological and sustainable strategies.

Synthesis of Bioactive Materials by In Situ One-Step Direct Loading of Syzygium aromaticum Essential Oil into Chitosan-Based Hydrogels

Hydrogel conjugates based on chitosan and an essential oil were synthetized by an ultrasound-assisted emulsification approach. Rheology studies revealed a gel-type structure with pronounced compactness and flexibility while SEM showed the formation of a two-level ordered network with highly interconnected pores. The swelling studies indicated a pH-dependent behavior with a significant overshooting effect. The synergistic effects of the components in clove essential oil led to a strong antioxidant character and an enhanced antimicrobial activity of the conjugate hydrogels. The bioactivity was maintained for 6 months, despite a slight decrease in the antimicrobial effect. Hydrogel conjugates were found to be very stable even after two months immersed in acidic solutions that would otherwise dissolve the chitosan matrix. Ultrasound emulsification was proved as an efficient one-step loading method of hydrophobic clove essential oil into hydrophilic chitosan matrix. It was found that clove oil and its components have a double role. Besides providing bioactivity, they also behave as gelation-inducing agents, acting as an alternative to the classical chemical cross-linkers to ensure the good physical and chemical stabilization of chitosan.

Full-fat field cricket (Gryllus bimaculatus) as a substitute for fish meal and soybean meal for weaning piglets: effects on growth performance, intestinal health, and redox status

Full-fat field cricket meal (FCP) is an alternative protein ingredient in livestock production; however, the effects of replacing conventional protein sources with FCP in nursery diets have not been determined. In this study, the effects of the partial replacement of either fish meal or soybean meal with FCP on weaning pigs were evaluated, including the analyses of growth performance, nutrient utilization, intestinal morphology, 
immunity, oxidative stress, and fecal microbial counts. A total of 100 crossbred weaning pigs [(Landrace × Large White) × Duroc] were allotted to one of the following five treatments with five replicates (four pigs/pen) and fed for 28 d postweaning. Treatments were 1) a corn-soybean meal (SBM)-based diet with 5% fish meal (Positive control; PC), 2) a corn-SBM-based diet without fish meal (Negative control; NC), 3) field crickets replacing fishmeal on a total Lys basis (FCP1), 4) field crickets replacing fishmeal on a kg/kg basis (FCP2), and 5) field crickets replacing fish meal and soybean meal (FCP3). The piglets on FCP1 had a higher body weight on days 14 and 28, and an increased average daily gain over the experimental period than NC (P < 0.05); FCP2 and FCP3 were similar to the FCP1 treatment. The incidence of diarrhea was lower under an FCP-supplemented diet than under the NC diet throughout the study (P < 0.05). Pigs fed FCP1 and FCP2 had a higher digestibility of crude 
protein (P = 0.041), and all FCP groups increased crude fat digestibility (P = 0.024). FCP1 and FCP2 also increased jejunal villus height 
(P = 0.009), whereas the increase in jejunal villus-to-crypt ratios (P = 0.019) was greater in pigs fed the FCP2 diet than those fed the NC diet. Furthermore, FCP2 supplementation increased serum immunoglobulin A levels on days 14 and 28, including reduced serum interleukin-6 and tumor necrosis factor alpha levels (P < 0.05). Pigs fed an FCP2 diet had reduced malondialdehyde levels than those fed a PC diet, while pigs fed an FCP2 diet had higher superoxide dismutase and glutathione peroxidase levels, and more fecal Lactobacillus spp. than those fed an NC diet (P < 0.05). These results support the use of FCP as an alternative protein ingredient with beneficial effects on growth performance, intestinal morphology, antioxidant capacity, and intestinal microbiota. In particular, FCP can be used as a partial substitute for fish meal and soybean meal without detrimental effects on weaning pigs.

Chitin derivatives ameliorate DSS-induced ulcerative colitis by changing gut microbiota and restoring intestinal barrier function

Chitin derivatives (CDs), including chitosan (CS), chitooligosaccharides (COS), and glucosamine (GlcN), were administrated in dextran sodium sulfate (DSS)-induced ulcerative colitis (UC) mice. UC symptoms such as body weight loss, reduced food intake, and increased disease activity index were relieved (except GlcNL group). CDs (except GlcNL) exerted a strong protective effect on colon length and colonic structure. Treatment with CDs (except GlcNL) increased IL-10 level, reduced levels of IL-1β, IL-6, TNF-α, myeloperoxidase, and inducible nitric oxide synthase, and enhanced expression of tight junction proteins significantly. CDs (except GlcNL) significantly upregulated IκB-α level, and downregulated p65 and p38 phosphory lation and TLR-4 mRNA transcription level, indicating inhibition of TRL-4/NF-κB/MAPK signaling pathway activity. CD treatments increased relative abundance of gut microbiota, modulated its composition, and increased the concentrations of SCFAs. Our findings indicate that CDs exert an ameliorative effect on UC by change of gut microbiota composition and restoration of intestinal barrier function.

A Novel Chitosanase from Penicillium oxalicum M2 for Chitooligosaccharide Production: Purification, Identification and Characterization

This study discovered a novel chitosanase from Penicillium oxalicum M2 based on a new screening strategy. An extracellular chitosanase was isolated and purified from the fermentation broth of Penicillium oxalicum M2. A 19.34-fold purification was achieved on a cation exchange column. Using sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, chitosanase was determined at approximately 42 kDa without any subunits. The sequence of peptide in the protein was identified as SALNKNYITNFSTLR by MALTI-TOF/TOF MS. The maximum catalytic activity of the purified enzyme was 60.45 U/mg at the optimum pH and temperature of 5.5 and 60 °C. The enzyme activity held stability in the range of 35-50 °C and pH 3-4.5. Ca²⁺, Mn²⁺, non-ionic surfactants (Tween 20/40/60/80 and Trition X-100) and some common reducing agents (DTT and β-ME) could significantly activate chitosanase. The purified enzyme showed rigorous specificity to chitosan as a substrate. The hydrolysate in the final stage of hydrolysis consisted of chitooligosaccharides with a degree of polymerization ranging from 2 to 5 and without glucosamine or acetylglucosamine. The monomeric enzyme obtained by one-step purification reveal applications potential in sugar industry, and expanded our understanding of the GH75 family chitosanases simultaneously.

Biomedyczne właściwości chitozanu – zastosowanie w inżynierii tkankowej Biomedical properties of chitosan: Application in tissue engineering

Inżynieria tkankowa to interdyscyplinarna dziedzina badań, która stosuje zasady inżynierii i nauk przyrodniczych do opracowywania substytutów biologicznych, przywracania, utrzymywania lub poprawy funkcji tkanek. Łączy medycy-nę kliniczną, inżynierię mechaniczną, materiałoznawstwo i biologię molekularną. Chitozan jest związkiem, który może być stosowany na szeroką skalę w biomedycynie, m.in. jako nośnik leków, nici chirurgiczne, materiały opatrunkowe przeznaczone do przyspieszonego gojenia ran oraz rusztowania komórkowe w inżynierii tkankowej. Chitozon spełnia najważniejsze kryteria dla biomateriałów, m.in. kompatybilność, odpowiednie właściwości mechaniczne, morfologia i porowatość, nietoksyczność i biodegradowalność. Rusztowania chitozanowe mogą sprzyjać adhezji, różnicowaniu i proliferacji na powierzchni komórek. Z chitozanu można tworzyć różne formy funkcjonalne w zależności od potrzeb i wymagań, w tym: hydrożele 3D, gąbki 3D, folie i membrany oraz nanowłókna. Ze względu na unikalne właściwości fizykochemiczne biopolimer ten może być również wykorzystany do oczyszczania białek terapeutycznych z endotoksyn bakteryjnych, co jest dziś istotnym problemem w oczyszczaniu produktu końcowego w zastosowaniach medycznych. Obecnie terapie oparte na białkach rekombinowanych znajdują szerokie zastosowanie w terapiach celowanych, inżynierii tkankowej oraz szeroko pojętej medycynie regeneracyjnej. Dlatego tak ważny jest współistniejący, dobrze zapro-jektowany system oczyszczania produktu białkowego, który nie zmieni swoich zasadniczych właściwości. Artykuł jest przeglądem aktualnych badań nad zastosowaniem materiałów bioaktywnych na bazie chitozanu w medycynie regene-racyjnej różnych tkanek i narządów (m.in. tkanki chrzęstnej i kostnej, tkanki skórnej czy tkanki nerwowej).

Combinatorial pathway engineering of Bacillus subtilis for production of structurally defined and homogeneous chitooligosaccharides

Chitooligosaccharides (COSs) have a widespread range of biological functions and an incredible potential for various pharmaceutical and agricultural applications. Although several physical, chemical, and biological techniques have been reported for COSs production, it is still a challenge to obtain structurally defined COSs with defined polymerization (DP) and acetylation patterns, which hampers the specific characterization and application of COSs. Herein, we achieved the de novo production of structurally defined COSs using combinatorial pathway engineering in Bacillus subtilis. Specifically, the COSs synthase NodC from Azorhizobium caulinodans was overexpressed in B. subtilis, leading to 30 ± 0.86 mg/L of chitin oligosaccharides (CTOSs), the homo-oligomers of N-acetylglucosamine (GlcNAc) with a well-defined DP lower than 6. Then introduction of a GlcNAc synthesis module to promote the supply of the sugar acceptor GlcNAc, reduced CTOSs production, which suggested that the activity of COSs synthase NodC and the supply of sugar donor UDP-GlcNAc may be the limiting steps for CTOSs synthesis. Therefore, 6 exogenous COSs synthase candidates were examined, and the nodCM from Mesorhizobium loti yielded the highest CTOSs titer of 560 ± 16 mg/L. Finally, both the de novo pathway and the salvage pathway of UDP-GlcNAc were engineered to further promote the biosynthesis of CTOSs. The titer of CTOSs in 3-L fed-batch bioreactor reached 4.82 ± 0.11 g/L (85.6% CTOS5, 7.5% CTOS4, 5.3% CTOS3 and 1.6% CTOS2), which was the highest ever reported. This is the first report proving the feasibility of the de novo production of structurally defined CTOSs by synthetic biology, and provides a good starting point for further engineering to achieve the commercial production.

Collagen/Chitosan Gels Cross-Linked with Genipin for Wound Healing in Mice with Induced Diabetes

Diabetes mellitus continues to be one of the most common diseases often associated with diabetic ulcers. Chitosan is an attractive biopolymer for wound healing due to its biodegradability, biocompatibility, mucoadhesiveness, low toxicity, and hemostatic effect. A panel of hydrogels based on chitosan, collagen, and silver nanoparticels were produced to treat diabetic wounds. The antibacterial activity, cytotoxicity, swelling, rheological properties, and longitudinal sections of hydrogels were studied. The ability of the gels for wound healing was studied in CD1 mice with alloxan-induced diabetes. Application of the gels resulted in an increase in VEGF, TGF-b1, IL-1b, and TIMP1 gene expression and earlier wound closure in a comparison with control untreated wounds. All gels increased collagen deposition, hair follicle repair, and sebaceous glands formation. The results of these tests show that the obtained hydrogels have good mechanical properties and biological activity and have potential applications in the field of wound healing. However, clinical studies are required to compare the efficacy of the gels as animal models do not reproduce full diabetes pathology.

How Does Chitosan Affect Methane Production in Anaerobic Digestion?

The expanding use of chitosan in sewage and sludge treatment processes raises concerns about its potential environmental impacts. However, investigations of the impacts of chitosan on sewage sludge anaerobic digestion where chitosan is present at substantial levels are sparse. This study therefore aims to fill this knowledge gap through both long-term and batch tests. The results showed that 4 g/kg total suspended solid (TSS) chitosan had no acute effects on methane production, but chitosan at 8-32 g/kg TSS inhibited methane production by 7.2-30.3%. Mass balance and metabolism of organic analyses indicated that chitosan restrained the transfer of organic substrates from solid phase to liquid phase, macromolecules to micromolecules, and finally to methane. Further exploration revealed that chitosan suppressed the secretion of extracellular polymeric substances of anaerobes by occupying the connection sites of indigenous carbohydrates and increased the mass transfer resistance between anaerobes and substrates, which thereby lowered the metabolic activities of anaerobes. Although chitosan could be partly degraded by anaerobes, it is much more persistent to be degraded compared with indigenous organics in sludge. Microbial community and key enzyme encoding gene analyses further revealed that the inhibition of chitosan to CO₂-dependent methanogenesis was much severer than that to acetate-dependent methanogenesis.

Advanced approaches for improving bioavailability and controlled release of anthocyanins

Anthocyanins are a group of phytochemicals responsible for the purple or red color of plants. Additionally, they are recognized to have health promoting functions including anti-cardiovascular, anti-thrombotic, anti-diabetic, antimicrobial, neuroprotective, and visual protective effect as well as anti-cancer activities. Thus, consumption of anthocyanin supplement or anthocyanin-rich foods has been recommended to prevent the risk of development of chronic diseases. However, the low stability and bioavailability of anthocyanins limit the efficacy and distribution of anthocyanins in human body. Thus, strategies to achieve target site-local delivery with good bioavailability and controlled release rate are necessary. This review introduced and discussed the latest advanced techniques of designing lipid-based, polysaccharide-based and protein-based complexes, nano-encapsulation and exosome to overcome the limitation of anthocyanins. The improved bioavailability and controlled release of anthocyanins have great significance for gastrointestinal tract absorption, transepithelial transportation and cellular uptake. The techniques of applying different biocompatible materials and modifying the solubility of anthocyanins complex could achieve target site-local delivery with negligible degradation and good bioavailability in human body.

Chitosan as an Underrated Polymer in Modern Tissue Engineering

Chitosan is one of the most well-known and characterized materials applied in tissue engineering. Due to its unique chemical, biological and physical properties chitosan is frequently used as the main component in a variety of biomaterials such as membranes, scaffolds, drug carriers, hydrogels and, lastly, as a component of bio-ink dedicated to medical applications. Chitosan's chemical structure and presence of active chemical groups allow for modification for tailoring material to meet specific requirements according to intended use such as adequate endurance, mechanical properties or biodegradability time. Chitosan can be blended with natural (gelatin, hyaluronic acid, collagen, silk, alginate, agarose, starch, cellulose, carbon nanotubes, natural rubber latex, κ-carrageenan) and synthetic (PVA, PEO, PVP, PNIPPAm PCL, PLA, PLLA, PAA) polymers as well as with other promising materials such as aloe vera, silica, MMt and many more. Chitosan has several derivates: carboxymethylated, acylated, quaternary ammonium, thiolated, and grafted chitosan. Its versatility and comprehensiveness are confirming by further chitosan utilization as a leading constituent of innovative bio-inks applied for tissue engineering. This review examines all the aspects described above, as well as is focusing on a novel application of chitosan and its modifications, including the 3D bioprinting technique which shows great potential among other techniques applied to biomaterials fabrication.

Self-Assembly of Phycoerythrin with Oligochitosan by Electrostatic Interaction for Stabilization of Phycoerythrin

Phycoerythrin (PE) is a natural water-soluble pigment protein with characteristic phycobilins and is sensitive to thermal and light environmental changes. In this study, PE was extracted from Porphyra haitanensis and PE-oligochitosan complexes (POC) were fabricated by a self-assembly approach. The effects of cationic oligochitosan on the binding interaction, structure, size distribution, and color stability of PE were evaluated. The stoichiometric number n was calculated to be 21.67 ± 2.65 (oligochitosan/PE) and the binding constant K was (6.47 ± 0.48) × 10⁵ M^-1. Cationic oligochitosan could electrostatically interact with PE and affect the PE structure by increasing the α-helix content. In addition, high concentrations of oligochitosan led to the formation of dense phycoerythrin protein granules. Moreover, at a reaction ratio of 20.0:1 (oligochitosan/PE), being approximately the predicted stoichiometric number n, the thermal stability (40-80 °C), natural light stability, and ultraviolet light irradiation (254 nm) stability of the POC were improved. This study provides an approach to reduce the susceptibility of PE upon environmental changes by forming a stable self-assembly complex, which will promote the application of PE as a natural pigment protein in food and chemical applications.

Chitosan nanoparticles alleviated endocrine disruption, oxidative damage, and genotoxicity of Bisphenol-A- intoxicated female African catfish

Bisphenol-A (BPA) is widely used in production of plastic products. It can reach the ecosystems affecting aquatic organisms most likely fishes. The purpose of this study was to study the toxic effects of BPA on the biochemical variables and oxidative stress in female African catfish, Clarias gariepinus and to estimate the protective role of chitosan nanoparticles (CSNPs) against BPA toxicity. Five groups in triplicates of fish were divided as follows: group I was control, group II was treated with CSNPs (0.66 ml/L), group III was exposed to BPA (1.43 μg/L), group IV was treated with BPA (1.43 μg/L) plus CSNPs (0.33 ml/L), and group V was treated with BPA (1.43 μg/L) plus CSNPs (0.66 ml/L) for 30 days. Blood and liver tissue samples were collected at the end of experiment for the biochemical and oxidative stress biomarkers analyses. Results exhibited that serum Follicle Stimulating Hormone (FSH) and 17-β Estradiol (E2) were significantly decreased in female catfish. While, serum Testosterone (T.) and Luteinizing Hormone (LH) were increased after exposure to BPA. Marked increment in superoxide dismutase (SOD) and malondialdehyde (MDA) levels of hepatic tissue of catfish exposed to BPA. Furthermore, significant reduction in hepatic catalase (CAT), glutathione peroxidase (GSH-px), total antioxidant capacity (TAC), reduced glutathione (GSH), and glutathione S-transferase (GST) levels were decreased significantly in BPA-exposed catfish compared to the control group. However, administration of female C. gariepinus with the low and high doses (0.33 ml/L and 0.66 ml/L) of CNPs restored the biochemical parameters to be close to the normal values of the control group and also, reduced oxidative stress induced by BPA toxicity. This improvement was evident in fish administrated with the high CSNPs dose (0.66 ml/L) compared to catfish exposed to BPA in group (III). Furthermore, the percentage of hepatic DNA damage was detected in group III exposed to BPA alone. However, it was declined after co- administration with both the low and high doses of CSNPs. The study has revealed that treatment with CSNPs has antagonistic functions against the toxicity of BPA in female African catfish.

From Farm to Fork: Crickets as Alternative Source of Protein, Minerals, and Vitamins

Globally, there is growing interest to integrate cricket-based ingredients (flour) into food products to combat food and nutrition insecurity. However, there is lack of information on in-depth nutrient profile of the two cricket species (Scapsipedus icipe and Gryllus bimaculatus), which are the most widely consumed in Africa. Here we determined the nutrient composition of two cricket species and compared them with published records of key animal and plant sources. Our results revealed that the crude protein contents of S. icipe and G. bimaculatus were similar (56.8 and 56.9%, respectively) and comparable to those of animal protein sources. Both cricket species had balanced amino acid profiles that are superior to that of animal and plant sources, except for histidine and cysteine. The protein digestibility of S. icipe and G. bimaculatus ranged between 80 and 88%, which is comparable to that of common plant foods but slightly lower than that of animal proteins. The iron, Zinc, and potassium contents were considerably higher in both cricket species compared to that of plant and animal sources. The calcium contents of both crickets (S. icipe and G. bimaculatus) was superior to that of plant and animal origin except for kidney beans and eggs, respectively. Riboflavin, thiamine, and folic acid concentrations of S. icipe and G. bimaculatus were superior to that of the conventional sources. Vitamin A levels were significantly higher in S. icipe compared to G. bimaculatus. This implies that S. icipe and G. bimaculatus can adequately contribute to our daily required nutrient intake. Thus, integrating cricket flours into ready-to-eat food products would address some of the most pressing nutritional deficiency challenges that many developing countries have to grapple with, particularly high risk to serious health problems such as anemia, poor pregnancy outcomes, hypertension, increased risk of morbidity and mortality, stunted growth and impaired physical and cognitive development. We conclude that edible crickets present unique opportunities for improving food and nutritional insecurity status of both resource-poor and Western populations.

Evaluation of Adhesive Bond Strength, and the Sustained Release of Fluoride by Chitosan-infused Resin-modified Glass Ionomer Cement: An In Vitro Study

Aim and objective

To evaluate the adhesive bond strength, and sustained release of fluoride in chitosan (CH)-infused RMGIC.

Materials and methods

Twenty caries-free human permanent premolar teeth, extracted for orthodontic purposes, were cleaned and stored in thymol solution. The crown of each tooth was cut into two halves and RMGIC (n = 10) and CH-infused RMGIC (n = 10) was placed between the two halves of the crown. The tooth was then stored in 10 mL of artificial saliva for a period of 30 days. The fluoride levels of the saliva were checked on the 15th- and the 30th-day using ion chromatography. The adhesive bond strength was checked on the 30th day using a universal testing machine.

Results

This study has shown that the bond strength of RMGIC was not affected by the inclusion of CH in it. Whereas, the sustained fluoride release of CH-modified RMGIC indicated that the fluoride release of CH-RMGIC was 8.47% >RMGIC at the end of 15 days, and, 39.68% >RMGIC at the end of 30 days.

Conclusion

The inclusion of CH in RMGIC does not alter its bond strength, while it does cause a greater release of fluoride.

Clinical significance

In progression with these results, the inclusion of CH in RMGIC could provide desirable properties like mechanical reinforcement effects and catalytic effects on the fluoride release and growth factors.

How to cite this article

Patel A, Dhupar JKMS, Jajoo SS, et al. Evaluation of Adhesive Bond Strength, and the Sustained Release of Fluoride by Chitosan-infused Resin-modified Glass Ionomer Cement: An In Vitro Study. Int J Clin Pediatr Dent 2021;14(2):254–257.

Fluorescence/photoacoustic imaging-guided nanomaterials for highly efficient cancer theragnostic agent

Imaging modalities combined with a multimodal nanocomposite contrast agent hold great potential for significant contributions in the biomedical field. Among modern imaging techniques, photoacoustic (PA) and fluorescence (FL) imaging gained much attention due to their non-invasive feature and the mutually supportive characteristic in terms of spatial resolution, penetration depth, imaging sensitivity, and speed. In this present study, we synthesized IR783 conjugated chitosan-polypyrrole nanocomposites (IR-CS-PPy NCs) as a theragnostic agent used for FL/PA dual-modal imaging. A customized FL and photoacoustic imaging system was constructed to perform required imaging experiments and create high-contrast images. The proposed nanocomposites were confirmed to have great biosafety, essentially a near-infrared (NIR) absorbance property with enhanced photostability. The in vitro photothermal results indicate the high-efficiency MDA-MB-231 breast cancer cell ablation ability of IR-CS-PPy NCs under 808 nm NIR laser irradiation. The in vivo PTT study revealed the complete destruction of the tumor tissues with IR-CS-PPy NCs without further recurrence. The in vitro and in vivo results suggest that the demonstrated nanocomposites, together with the proposed imaging systems could be an effective theragnostic agent for imaging-guided cancer treatment.

Improve thermostability of Bacillus sp. TS chitosanase through structure-based alignment

Chitosanases can catalyze the release of chitooligosaccharides which have a number of medical applications. Therefore, Chitosanases are good candidates for large-scale enzymatic synthesis due to their favorable thermostability properties and high catalytic efficiency. To further improve the thermostability of a chitosanase from Bacillus sp. TS, which has a half-life of 5.32 min, we mutated specific serine residues that we identified as potentially relevant through structure comparison with thermophilic CelA from Clostridium thermocellum. Out of a total of 15 mutants, three, namely S265G, S276A, and S347G, show higher thermostability. Their half-lives at 60 °C were calculated as 34.57 min, 36.79 min and 7.2 min. The K_m values of S265G, S276A and S347G mutants show substrate binding ability comparable to that of the wild-type enzyme, while the S265G mutant displays a significant decrease of enzymatic activities. Additionally, we studied the synergistic effects of combined mutations, observing that all double mutants and the triple mutant are more stable than the wild-type enzyme and single mutants. Finally, we investigated the mechanisms which might give a reasonable explanation for the improved thermostability via comparative analysis of the resulting 3D structures.

Mannose Receptor Mediates the Activation of Chitooligosaccharides on Blunt Snout Bream (Megalobrama amblycephala) Macrophages

Chitooligosaccharide (COS) is an important immune enhancer and has been proven to have a variety of biological activities. Our previous research has established an M1 polarization mode by COS in blunt snout bream (Megalobrama amblycephala) macrophages, but the mechanism of COS activation of blunt snout bream macrophages remains unclear. In this study, we further explored the internalization mechanism and signal transduction pathway of chitooligosaccharide hexamer (COS6) in blunt snout bream macrophages. The results showed that mannose receptor C-type lectin-like domain 4-8 of M. amblycephala (MaMR CTLD4-8) could recognize and bind to COS6 and mediate COS6 into macrophages by both clathrin-dependent and caveolin-dependent pathways. In the inflammatory response of macrophages activated by COS6, the gene expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and nitric oxide synthase 2 (NOS2) was significantly inhibited after MaMR CTLD4-8-specific antibody blockade. However, even if it was blocked, the expression of these inflammation-related genes was still relatively upregulated, which suggested that there are other receptors involved in immune regulation. Further studies indicated that MaMR CTLD4-8 and Toll-like receptor 4 (TLR4) cooperated to regulate the pro-inflammatory response of macrophages caused by COS6. Taken together, these results revealed that mannose receptor (MR) CTLD4-8 is indispensable in the process of recognition, binding, internalization, and immunoregulation of COS in macrophages of blunt snout bream.

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

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

Fabrication and characterization of novel antibacterial chitosan/dialdehyde guar gum hydrogels containing pomegranate peel extract for active food packaging application

This study aimed to investigate synthesis and structural characteristics of the chitosan (CS) - modified dialdehyde guar gum (DAGG) hydrogel through the Schiff base reaction. The highest swelling capacity was achieved as about 12,000% of dry weight of the freeze-dried powder at CS: DAGG hydrogel with the mixing ratio of 30:70. The swelling ratio was not affected by changes in pH, which could be considered as an important property in the control of moisture in absorbent pad. The FTIR results indicated that the new amide groups have been formed at 1680 cm^-1, which can be attributed to the covalent bond between the amide groups of CS and the aldehyde groups of GG. Based on a SEM image, the prepared hydrogel showed the porous structure so it verified the crosslinking formation between the two polymers. Rheological analyses confirmed that formation compact and porous structure led to some noteworthy improvements in the strength of hydrogel prepared with a high ratio of DAGG. The hydrogel loaded with 5% pomegranate peel extract (PPE) showed both good antioxidant (81.13%) and antimicrobial activities. The hydrogel was observed to have a good potential to be used as an antibacterial pad.

A review on chitosan and chitosan-based bionanocomposites: Promising material for combatting global issues and its applications

Over the last few years, several attempts have been made to replace petrochemical products with renewable and biodegradable components. The most challenging part of this approach is to obtain bio-based materials with properties and functions equivalent to those of synthetic products. Various naturally occurring polymers such as starch, collagen, alginate, cellulose, and chitin represent attractive candidates as they could reduce dependence on synthetic products and consequently positively impact the environment. Chitosan is also a unique bio-based polymer with excellent intrinsic properties. It is known for its anti-bacterial and film-forming properties, has high mechanical strength and good thermal stability. Nanotechnology has also applied chitosan-based materials in its most recent achievements. Therefore, numerous chitosan-based bionanocomposites with improved physical and chemical characteristics have been developed in an eco-friendly and cost-effective approach. This review discusses various sources of chitosan, its properties and methods of modification. Also, this work focuses on diverse preparation techniques of chitosan-based bionanocomposites and their emerging application in various sectors. Additionally, this review sheds light on future research scope with some drawbacks and challenges to motivate the researchers for future outstanding research works.

Fundamental and Practical Aspects in the Formulation of Colloidal Polyelectrolyte Complexes of Chitosan and siRNA

The formation of electrostatic interactions between polyanionic siRNA and polycations gives an easy access to the formation of colloidal particles capable of delivering siRNA in vitro or in vivo. Among the polycations used for siRNA delivery, chitosan occupies a special place due to its unique physicochemical and biological properties. In this chapter we describe the fundamental and practical aspects of the formation of colloidal complexes between chitosan and siRNA. The basis of the electrostatic complexation between oppositely charged polyelectrolytes is first introduced with a focus on the specific conditions to obtain stable colloid complex particles. Subsequent, the properties that make chitosan so special are described. In a third part, the main parameters influencing the colloidal properties and stability of siRNA/chitosan complexes are reviewed with emphasis on some practical aspects to consider in the preparation of complexes.

Fabrication of a multi-level drug release platform with liposomes, chitooligosaccharides, phospholipids and injectable chitosan hydrogel to enhance anti-tumor effectiveness

Some anti-cancer drugs have poor solubility and availability, and are easily eliminated by rapid metabolism in vivo. To fix the drugs at the administration site and delay their release, a release platform with multi-level and multi-function was designed. The results showed that the curcumin (Cur) loaded liposomes (Cur@Lip) were coated sequentially with positive Chitooligosaccharides (Cur@Lip-Cos) and negative phospholipids (Cur@Lip-Cos-PC), to enhance water solubility, encapsulation efficiency, and delayed the release of the Cur, stability and cell intake of the liposomes, and the bioactivity of the system. The Cur@Lip-Cos could significantly enhance the inhibitory effect of MCF-7, better than the Cur@Lip-Cos-PC. The Lips were then fixed in an injectable thiolated chitosan hydrogel for local immobilization and sustained release which can effectively delay the release of Cur to inhibit MCF-7 growth. In summary, the innovative and biomimetic liposomal hydrogels are expected to provide more ideas for the design of drug carriers.

Quantum mechanical study on physisorption of dissolved metal ions in seawater using cellulose, chitosan and chitin

Density Functional Theory (DFT) calculations were performed to investigate the adsorption of alkali and alkaline earth metal ions, Na⁺, K⁺, Mg²⁺, and Ca²⁺ present in seawater by biopolymers, cellulose, chitosan, and chitin. Analysis of the optimized geometries of the complexes formed by physisorption of metal ions on biopolymers reveals that monomer of chitin is the best biopolymer for adsorption of Mg²⁺ ion. Water as a solvent reduces the reactivity of complexes formed, playing a significant role in complex stability, which further proved the effective use of cellulose, chitosan and chitin for real-time applications. Natural Bond Orbital (NBO) analysis and quantum reactivity descriptors of the optimized geometries indicate that the electronic charge transfer between the biopolymer and metal ions acts as a driving force for the complex formation. This study also highlights the significant role of water in physisorption of metal ions on biopolymer.

Sustainable Agriculture Systems in Vegetable Production Using Chitin and Chitosan as Plant Biostimulants

Chitin and chitosan are natural compounds that are biodegradable and nontoxic and have gained noticeable attention due to their effective contribution to increased yield and agro-environmental sustainability. Several effects have been reported for chitosan application in plants. Particularly, it can be used in plant defense systems against biological and environmental stress conditions and as a plant growth promoter—it can increase stomatal conductance and reduce transpiration or be applied as a coating material in seeds. Moreover, it can be effective in promoting chitinolytic microorganisms and prolonging storage life through post-harvest treatments, or benefit nutrient delivery to plants since it may prevent leaching and improve slow release of nutrients in fertilizers. Finally, it can remediate polluted soils through the removal of cationic and anionic heavy metals and the improvement of soil properties. On the other hand, chitin also has many beneficial effects such as plant growth promotion, improved plant nutrition and ability to modulate and improve plants’ resistance to abiotic and biotic stressors. The present review presents a literature overview regarding the effects of chitin, chitosan and derivatives on horticultural crops, highlighting their important role in modern sustainable crop production; the main limitations as well as the future prospects of applications of this particular biostimulant category are also presented.

Chitosan as a Coating for Biocontrol in Postharvest Products: A Bibliometric Review

The aim of this work was to carry out a systematic literature review focused on the scientific production, trends, and characteristics of a knowledge domain of high worldwide importance, namely, the use of chitosan as a coating for postharvest disease biocontrol in fruits and vegetables, which are generated mainly by fungi and bacteria such as Aspergillus niger, Rhizopus stolonifera, and Botrytis cinerea. For this, the analysis of 875 published documents in the Scopus database was performed for the years 2011 to 2021. The information of the keywords' co-occurrence was visualized and studied using the free access VOSviewer software to show the trend of the topic in general. The study showed a research increase of the chitosan and nanoparticle chitosan coating applications to diminish the postharvest damage by microorganisms (fungi and bacteria), as well as the improvement of the shelf life and quality of the products.

Physicochemical Properties of Chitosan from Two Commonly Reared Edible Cricket Species, and Its Application as a Hypolipidemic and Antimicrobial Agent

Insect-derived chitin and chitosan have gained interest as alternative sources to that derived from crustaceans; however, little information is available on chitin from the house cricket (Acheta domesticus) and tropical banded cricket (Gryllodes sigillatus), two cricket species commonly reared in the United States for human consumption. In this study, chitin was successfully isolated and purified from these two cricket species; using FTIR, chitins were found to be in alpha-crystalline form. Cricket chitosan was produced from both species with varying degrees of deacetylation (DDA) by varying alkaline conversion duration. G. sigillatus chitosan was larger (524 kDa) than A. domesticus chitosan (344 kDa). Both cricket chitosans showed similar (p > 0.05) lipid-binding capacity to that of shrimp chitosan. Both chitosans were as effective at inhibiting microbial growth of surrogate foodborne pathogens as the commercial shrimp chitosan. At a concentration of 0.50 mg/mL cricket chitosan, approximately 100% of Listeria innocua growth was inhibited, due to a contribution of both chitosan and the solvent-acetic acid. At the same concentration, growth of Escherichia coli was inhibited 90% by both cricket chitosan samples with ~80% DDA, where a decrease in the DDA led to decreased antimicrobial activity. However, varying the DDA had no effect on chitosan’s lipid-binding capacity. As more edible insects become a normalized protein source in our diet, the use of by-products, such as chitin and chitosan, derived from insect protein processing, show promising applications for the pharmaceutical and food industries.

Hierarchical Core-Shell Fe₃O₄@mSiO₂@Chitosan Nanoparticles for pH-Responsive Drug Delivery

Hierarchical nanoparticles are of great interest because they possess unique physicochemical properties and multiple functionalities, providing a wealth of possibilities for various applications. In this work, we have developed a well-designed method to prepare hierarchical magnetic nanoparticles Fe₃O₄@mSiO₂@CS by integrating a solvothermal method for synthesizing the Fe₃O₄ core, a dualtemplating micelle system for preparing a layer of mesoporous silica (mSiO₂) shell, and a silane coupling method via γ-glycidoxypropyltrimethoxysilane for binding a chitosan (CS) layer on the silica surface. The porous hierarchical nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic light scattering nanoparticle size analyzer, and specific surface area and pore size analyzer. The loading capacity and the release behavior of the as-prepared nanoparticles for doxorubicin hydrochloride were studied, and it was found that the drug release rate was faster at pH 6.0 than at pH 7.4, revealing the pH-responsive property of the nanoparticles.

The impact of chitooligosaccharides and their derivatives on the in vitro and in vivo antitumor activity: A comprehensive review

Chitooligosaccharides (COS) are the degraded products of chitin or chitosan. COS is water-soluble, non-cytotoxic to organisms, readily absorbed through the intestine, and eliminated primarily through the kidneys. COS possess a wide range of biological activities, including immunomodulation, cholesterol-lowering, and antitumor activity. Although work on COS goes back at least forty years, several aspects remain unclear. This review narrates the recent developments in COS antitumor activities, while paying considerable attention to the impacts of physicochemical properties (such as molecular weight and degrees of deacetylation) and chemical modifications both in vitro and in vivo. COS derivatives not only improve some physicochemical properties, but also expand the range of applications in drug and gene delivery. COS (itself or as a drug carrier) can inhibit tumor cell proliferation and metastasis, which might be attributed to its ability to stimulate the immune response along with its anti-angiogenic activity. Further, an attempt has been made to report limitations and future research. The potential health benefits of COS and its derivatives against cancer may offer a new insight on their applications in food and medical fields.

Insight on Solution Plasma in Aqueous Solution and Their Application in Modification of Chitin and Chitosan

Sustainability and environmental concerns have persuaded researchers to explore renewable materials, such as nature-derived polysaccharides, and add value by changing chemical structures with the aim to possess specific properties, like biological properties. Meanwhile, finding methods and strategies that can lower hazardous chemicals, simplify production steps, reduce time consumption, and acquire high-purified products is an important task that requires attention. To break through these issues, electrical discharging in aqueous solutions at atmospheric pressure and room temperature, referred to as the "solution plasma process", has been introduced as a novel process for modification of nature-derived polysaccharides like chitin and chitosan. This review reveals insight into the electrical discharge in aqueous solutions and scientific progress on their application in a modification of chitin and chitosan, including degradation and deacetylation. The influencing parameters in the plasma process are intensively explained in order to provide a guideline for the modification of not only chitin and chitosan but also other nature-derived polysaccharides, aiming to address economic aspects and environmental concerns.

Alginate gels crosslinked with chitosan oligomers - a systematic investigation into alginate block structure and chitosan oligomer interaction

Three alginates with fundamentally different block structures, poly-M, poly-G, and poly-MG, have been investigated upon ionic crosslinking with chitosan oligosaccharides (CHOS), using circular dichroism (CD), rheology, and computer simulations, supporting the previously proposed gelling principle of poly-M forming zipper-like junction zones with chitosan (match in charge distance along the two polyelectrolytes) and revealing a unique high gel strength poly-MG chitosan gelling system. CD spectroscopy revealed an increased chiroptical activity exclusively for the poly-M chitosan gelling system, indicative of induced conformational changes and higher ordered structures. Rheological measurement revealed gel strengths (G' < 900 Pa) for poly-MG (1%) CHOS (0.3%) hydrogels, magnitudes of order greater than displayed by its poly-M analogue. Furthermore, the ionically crosslinked poly-MG chitosan hydrogel increased in gel strength upon the addition of salt (G' < 1600 at 50 mM NaCl), suggesting a stabilization of the junction zones through hydrophobic interactions and/or a phase separation. Molecular dynamics simulations have been used to further investigate these findings, comparing interaction energies, charge distances and chain alignments. These alginates are displaying high gel strengths, are known to be fully biocompatible and have revealed a broad range of tolerance to salt concentrations present in biological systems, proving high relevance for biomedical applications.