Biological activities of carbohydrate-branched chitosan derivatives

Chitosan as excellent bio-macromolecule with myriad of anti-activities in biomedical applications - A review

The aim of the study is to explore the myriad of anti-activities of chitosan - deacylated derivative of chitin in biomedical applications. Chitosan consists of reactive residual amino groups, which can be modified chemically to obtain wide range of derivatives. These derivatives exhibit the controlled physicochemical characteristics, which in turn improve its functional properties. Such derivatives find numerous applications in the field of biomedical science, agriculture, tissue engineering, bone regeneration and environmental science. This study presents a comprehensive overview of the multifarious anti-activities of chitosan and its derivatives in the field of biomedical science including anti-microbial, antioxidant, anti-tumor, anti-HIV, anti-fungal, anti- inflammatory, anti-Alzheimer's, anti-hypertensive and anti-diabetic activity. It briefly details these anti-activities with respect to its mode of action, pharmacological effects and potential applications. It also presents the overview of current research exploring novel derivatives of chitosan and its anti- activities in the recent past. Finally, the review projects the prospective potential of chitosan and its derivatives and expects to encourage the readers to develop new drug delivery systems based on such chitosan derivatives and explore its applications in biomedical science for benefit of mankind.

Bio-Inspired Homogeneous Conductive Hydrogel with Flexibility and Adhesiveness for Information Transmission and Sign Language Recognition

The wearable electronic technique is increasingly becoming an effective approach to overcoming the communication obstacles between signers and non-signers. However, the efficacy of conducting hydrogels currently proposed as flexible sensor devices is hindered by their poor processability and matrix mismatch, which frequently results in adhesion failure at the combined interfaces and deterioration of mechanical and electrochemical performance. Herein, we propose a hydrogel composed of a rigid matrix in which the hydrophobic and aggregated polyaniline was homogeneously embedded, while quaternate-functionalized nucleobase moieties endowed the flexible network with adhesiveness. Accordingly, the resulting hydrogel with chitosan-graft-polyaniline (chi-g-PANI) copolymers exhibited a promising conductivity (4.8 S·m^-1) because of the uniformly dispersed polyaniline components and a high strain strength (0.84 MPa) because of the chain entanglement of chitosan after soaking. In addition, the modified adenine molecules not only realized synchronization in improving the stretchability (up to 1303%) and exhibiting a skin-like elastic modulus (≈184 kPa), but also provided a durable interfacial contact with various materials. The hydrogel was further fabricated into a strain-monitoring sensor for information encryption and sign language transmission based on its sensing stability and strain sensitivity of up to 2.77. The developed wearable sign language interpreting system provides an innovative strategy to assist auditory or speech-impaired people in communicating with non-signers using visual-gestural patterns including body movements and facial expressions.

Novel Chitosan Derivatives and Their Multifaceted Biological Applications

Chitosan is a rather attractive material, especially because of its bio-origins as well as generation from exoskeletal waste. As the mantle has been effectively transferred from chitin to chitosan, so has it been extrapolated to in-house synthesized novel chitosan derivatives. This review comprehensively lists the available novel chitosan derivatives (ChDs) and summarizes their biological applications. The fact that chitosan derivatives do comprise multifaceted biological applications is attested by the voluminous reports on their varied contributions. However, this review points out to the fact that there has been selective focus on bio functions such as antifungal, antioxidant, antibacterial, whereas other biomedical applications and antiviral applications remain relatively less explored. With their current functionality record, there is definitely no doubt that the plethora of synthesized ChDs will have a profound impact on the unexplored biological aspects. This review points out this lacuna as room for future exploration.

Recent advances of emerging green chitosan-based biomaterials with potential biomedical applications: A review

Chitosan is the most abundant natural biopolymer, after cellulose. It is mainly derived from the fungi, shrimp's shells, and exoskeleton of crustaceans, through the deacetylation of chitin. The ecological sustainability associated with its exercise and the flexibility of chitosan owing to its active functional hydroxyl and amino groups makes it a promising candidate for a wide range of applications through a variety of modifications. The biodegradability and biocompatibility of chitosan and its derivatives along with their various chemical functionalities make them promising carriers for pharmaceutical, nutritional, medicinal, environmental, agriculture, drug delivery, and biotechnology applications. The present work aims to provide a detailed and organized description of modified chitosan and its derivatives-based nanomaterials for biomedical applications. We addressed the biological and physicochemical benefits of nanocomposite materials made up of chitosan and its derivatives in various formulations, including improved physicochemical stability and cells/tissue interaction, controlled drug release, and increased bioavailability and efficacy in clinical practice. Moreover, several modification techniques and their effective utilization are also reviewed and collected in this review.

A review on chitosan and its development as pulmonary particulate anti-infective and anti-cancer drug carriers

Chitosan, as a biodegradable and biocompatible polymer, is characterized by anti-microbial and anti-cancer properties. It lately has received a widespread interest for use as the pulmonary particulate backbone materials of drug carrier for the treatment of infectious disease and cancer. The success of chitosan as pulmonary particulate drug carrier is a critical interplay of their mucoadhesive, permeation enhancement and site/cell-specific attributes. In the case of nanocarriers, various microencapsulation and micro-nano blending systems have been devised to equip them with an appropriate aerodynamic character to enable efficient pulmonary aerosolization and inhalation. The late COVID-19 infection is met with acute respiratory distress syndrome and cancer. Chitosan and its derivatives are found useful in combating HCoV and cancer as a function of their molecular weight, substituent type and its degree of substitution. The interest in chitosan is expected to rise in the next decade from the perspectives of drug delivery in combination with its therapeutic performance.

Antibacterial activities of microwave-assisted synthesized polypyrrole/chitosan and poly (pyrrole-N-(1-naphthyl) ethylenediamine) stimulated by C-dots

Polypyrrole grafted with chitosan (PPy-g-CS) and poly (pyrrole-N-(1-naphthyl) ethylenediamine, a copolymer, (COP) have been synthesized by a one-step microwave procedure with carbon dots(C-Dots) as initiators. The electrostatic interaction between the positively charged polymers and negatively charged microbial cell membranes is widely anticipated to be responsible for cellular lysis. However, Escherichia coli exposed to PPy-g-CS (zeta potential = +46.9 mV) was completely perished after 3 h while COP (zeta potential = +64.1 mV) exhibited no antimicrobial effect. The two polymers were capable of eradicating Staphylococcus aureus, implying the charged effect is the main mechanism of cell death. The two polymers could also chelate calcium and other nutrients as well as form an external barrier to suppress the penetration of essential nutrients to support microbial survival and proliferation. In particular, pyrrole grafted chitosan was reasoned to stack onto the bacterial surface to impede the mass transfer and suppress the bacterial metabolic activity. The binding of chitosan to teichoic acids, essential acids of Gram-positive bacteria, would provoke a sequence of events and lead to bacterial death.

Functional Chitosan-based Materials for Biological Applications

Background:

Bio-based materials, as the plentiful and renewable resources for natural constituents which are essential for biomedical and pharmaceutical applications, have not been exploited adequately yet. Chitosan is a naturally occurring polysaccharide obtained from chitin, which has recently attracted widespread attention owing to its excellent activity. This review shows the methods of extraction and modification of chitosan and provides recent progress of synthesis and use of chitosan-based materials in biological applications.

Methods:

By consulting the research literature of the last decade, the recent progresses of functional chitosan-based materials for biological applications were summarized and divided into the methods of extraction chitosan, the chemical modification of chitosan, chitosan-based materials for biological applications were described and discussed.

Results:

Chemical modification of chitosan broadens its applications, leading to developing numerous forms of chitosan-based materials with excellent properties. The excellent bioactivity of chitosan-based material enables it serves potential applications in biomedical fields.

Conclusion:

Chitosan-based materials not only exhibit the excellent activities of chitosan but also show other appealing performance of combined materials, even give the good synergistic properties of chitosan and its composite materials. Further studies are needed to define the ideal physicochemical properties of chitosan for each type of biomedical applications. The development of various functional chitosan-based materials for biological applications will be an important field of research, and this kind of material has important commercial value.

Development of Mucoadhesive Chitosan Derivatives for Use as Submucosal Injections

Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) have been used for surgical treatment of early gastric cancer. These endoscopic techniques require proper submucosal injections beneath the tumor to provide a sufficiently high submucosal fluid cushion (SFC) to facilitate clean dissection and resection of the tumor. Until now, the submucosal injection materials developed for endoscopic techniques such as EMR and ESD of tumors have been composed of macromolecules, proteins, or polysaccharides. We have been investigating the use of chitosan, a product that is obtained by the alkaline deacetylation of chitin, the second-most abundant natural polysaccharide. Specifically, we have been studying a photocrosslinked chitosan hydrogel (PCH) and solubilized chitosan derivatives for use as novel submucosal injections for endoscopic techniques. Notably, chitosan derivatives with lactose moieties linked to the amino groups of its glucosamine units can specifically interact with acidic mucopolysaccharides and mucins in submucosa without the need for the incorporation of harmful photoreactive groups nor potentially mutagenic ultraviolet irradiation.

Anvillea garcinii extract inhibits the oxidative burst of primary human neutrophils

BACKGROUND

Anvillea garcinii Coss. & Durieu (Anv) plant is used as a traditional North African medicine against several diseases associated with inflammation. At inflammatory sites, reactive oxygen species (ROS) produced in excess by activated phagocyte NADPH oxidase (NOX2) can accentuate inflammatory responses. Thus, we investigated if Anv-water soluble polysaccharides could modulate primary human neutrophil oxidative burst in vitro.

METHODS

Human neutrophils were isolated from fresh whole blood and O₂^.- generation was measured by cytochrome c reduction assays. Western blots were used to analyse the translocation of PKC, p47^phox (a key component of NOX2 activity) to neutrophil plasma membrane. Also, myeloperoxidase (MPO) release in the extracellular medium was studied by western blots. Flow cytometric analysis was used to detect CD11b membrane expression.

RESULTS

Water soluble polysaccharides from Anv dose-dependently inhibited N-formyl-methionyl-leucyl-phenylalanine (fMLF)- and phorbol myristate acetate (PMA)-induced O₂^.- generation by human neutrophils. Moreover, Anv-polysaccharides strongly inhibited PMA-induced PKCβ and p47^phox translocation to membranes and p47^phox phosphorylation on Ser328, a main PKC target. In contrast, polysaccharides extract from Zygophyllum gaetulum plant, which is also used as a traditional North African medicine against inflammatory diseases, was ineffective on this PKCβ-p47phox pathway. Further, Anv inhibited important neutrophil degranulation markers corresponding to myeloperoxidase (MPO) release and CD11b membrane expression.

CONCLUSION

The process of down-regulating NADPH oxidase by polysaccharides extracts from Anv provides new insights into the mechanism of Anv's anti-inflammatory actions.

In situ synthesised TiO2-chitosan-chondroitin 4-sulphate nanocomposites for bone implant applications

The artificial materials for bone implant applications are gaining more importance in the recent years. The series titania-chitosan-chondroitin 4-sulphate nanocomposites of three different concentrations (2:1:x, where x- 0.125, 0.25, 0.5) have been synthesised by in situ sol-gel method and characterised by various techniques. The particle size of the nanocomposites ranges from 30-50 nm. The bioactivity, swelling nature, and the antimicrobial nature of the nanocomposites were investigated. The swelling ability and bioactivity of the composites is significantly greater and they possess high zone of inhibition against the microorganisms such as Staphylococcus aureus and Escherichia coli. The cell viability of the nanocomposites were evaluated by using MG-63 and observed the composites possess high cell viability at low concentration. The excellent bioactivity and biocompatibility makes these nanocomposites a promising biomaterial for bone implant applications.

Biologically Active Polymers: Modification and Anti-microbial Activity of Chitosan Derivatives

The principal derivative of chitin is chitosan, which is obtained by deacetylation of chitin. Chemical modification of synthetic and natural polymers is a convenient way to obtain materials with unique chemical and physical properties. Chitosan has an amino group at C-2 which is important because amino groups are nucleophilic and readily react with electrophilic reagents. Chitosan modified under mild conditions often results in regioselectivity for the C-2 amino group.

In the present work, this reactivity was exploited to attach biologically active moieties into the amino groups of chitosan to yield anti-microbial chitosans. Specifically, vanillin, p-hydroxybenzaldehyde, p-chlorobenzaldehyde, anisaldehyde, methyl 4-hydroxybenzoate, methyl 2,4-dihydroxybenzoate, propyl 3,4,5-trihydroxybenzoate and 2-hydroxymethylbenzoate were attached. The anti-microbial activity of these modified chitosans was explored against fungi such as Candida albicans SC5314, Aspergillus flavus and Fusarium oxysporium. Also, they were tested against bacteria such as Bacillus subtilis, Escherichia coli and Staphylococcus aureus. These modified chitosans were found to be highly active toward fungi species more than bacterial species.

Phthaloylchitosan-Based Gel Polymer Electrolytes for Efficient Dye-Sensitized Solar Cells

Phthaloylchitosan-based gel polymer electrolytes were prepared with tetrapropylammonium iodide, Pr4NI, as the salt and optimized for conductivity. The electrolyte with the composition of 15.7 wt.% phthaloylchitosan, 31.7 wt.% ethylene carbonate (EC), 3.17 wt.% propylene carbonate (PC), 19.0 wt.% of Pr4NI, and 1.9 wt.% iodine exhibits the highest room temperature ionic conductivity of 5.27 × 10−3 S cm−1. The dye-sensitized solar cell (DSSC) fabricated with this electrolyte exhibits an efficiency of 3.5% withJSCof 7.38 mA cm−2,VOCof 0.72 V, and fill factor of 0.66. When various amounts of lithium iodide (LiI) were added to the optimized gel electrolyte, the overall conductivity is observed to decrease. However, the efficiency of the DSSC increases to a maximum value of 3.71% when salt ratio of Pr4NI : LiI is 2 : 1. This cell hasJSC,VOCand fill factor of 7.25 mA cm−2, 0.77 V and 0.67, respectively.

Utilization of carboxymethyl chitosan in cosmetics

Carboxymethyl chitosan is a chitosan derivative of the most intensively investigated due to its water solubility in wider pH range compared with the parent compound, thus extended its use in various applications. In this review, different preparation conditions, which resulting in the N- and O-carboxylated chitosan, diverse degree of substitution and water solubility are recapitulated. Five important features of carboxymethyl chitosan from recent studies, which are moisture absorption-retention, anti-microbial properties, antioxidant capacities, delivery system and emulsion stabilization, have been centred and emphasized for cosmetic utilization. Additionally, cytotoxicity information has been inclusively incorporated to ensure its safety in application.

Biocomposite scaffolds containing chitosan/alginate/nano-silica for bone tissue engineering

Bone tissue engineering is a promising alternative method for treating bone loss by a combination of biomaterials and cells. In this study, we fabricated biocomposite scaffolds by blending chitosan (CS), alginate (Alg) and nano-silica (nSiO2), followed by freeze drying. The prepared scaffolds (CS/Alg, CS/Alg/nSiO2) were characterized by SEM, FT-IR and XRD analyses. In vitro studies such as swelling, biodegradation, biomineralization, protein adsorption and cytotoxicity were also carried out. The scaffolds possessed a well-defined porous architecture with pore sizes varying from 20 to 100 μm suitable for cell infiltration. The presence of nSiO2 in the scaffolds facilitated increased protein adsorption and controlled swelling ability. The scaffolds were biodegradable and the addition of nSiO2 improved apatite deposition on these scaffolds. There was no significant cytotoxicity effect of these CS/Alg/nSiO2 scaffolds towards osteolineage cells. Thus, these results indicate that CS/Alg/nSiO2 scaffolds may have potential applications for bone tissue engineering.

Specific association of lectin LecB with the surface of Pseudomonas aeruginosa: role of outer membrane protein OprF

The fucose binding lectin LecB affects biofilm formation and is involved in pathogenicity of Pseudomonas aeruginosa. LecB resides in the outer membrane and can be released specifically by treatment of an outer membrane fraction with fucose suggesting that it binds to specific ligands. Here, we report that LecB binds to the outer membrane protein OprF. In an OprF-deficient P. aeruginosa mutant, LecB is no longer detectable in the membrane but instead in the culture supernatant indicating a specific interaction between LecB and OprF.

Synthesis of organosoluble chitosan derivatives with polyphenolic side chains

A one-pot synthesis was used to produce chitosan derivatives with polyphenolic side chains via a regioselective phenolic coupling reaction. Under Mannich reaction conditions, treatment of chitosan with formaldehyde and methyl 2,4-dihydroxybenzoate gave N-(2,6-dihydroxy-3-methoxycarbonylphenyl)methylated chitosan in good yield (87%). Formation of a CC bond occurred regioselectively at the C(3) position of methyl 2,4-dihydroxybenzoate. Chitosan derivatives having various phenolic compounds as a side chain were easily synthesized in a similar manner. The chitosan derivatives showed good biodegradability and improved their solubility in methanol (9.8mg mL(-1)) and 2-methoxyethanol (> 10mg mL(-1)). The UV protection provided by the derivatives with phenolic benzophenone side chain was evaluated using UV spectra of polyethylene terephthalate and poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) films coated with the derivatives and the derivatives absorbed effectively in the UV-A region (<60%). Self-aggregation of the chitosan derivatives with the phenolic side chain was observed by using a fluorescent probe in aqueous solution.

A collagen–chitosan hydrogel for endothelial differentiation and angiogenesis

Cell therapy for the treatment of cardiovascular disease has been hindered by low cell engraftment, poor survival, and inadequate phenotype and function. In this study, we added chitosan to a previously developed injectable collagen matrix, with the aim of improving its properties for cell therapy and neovascularization. Different ratios of collagen and chitosan were mixed and chemically crosslinked to produce hydrogels. Swell and degradation assays showed that chitosan improved the stability of the collagen hydrogel. In culture, endothelial cells formed significantly more vascular-like structures on collagen–chitosan than collagen-only matrix. While the differentiation of circulating progenitor cells to CD31+ cells was equal on all matrices, vascular endothelial-cadherin expression was increased on the collagen–chitosan matrix, suggesting greater maturation of the endothelial cells. In addition, the collagen–chitosan matrix supported a significantly greater number of CD133+ progenitor cells than the collagen-only matrix. In vivo, subcutaneously implanted collagen–chitosan matrices stimulated greater vascular growth and recruited more von Willebrand factor (vWF+) and CXCR4+ endothelial/angiogenic cells than the collagen-only matrix. These results indicate that the addition of chitosan can improve the physical properties of collagen matrices, and enhance their ability to support endothelial cells and angiogenesis for use in cardiovascular tissue engineering applications.

Norcantharidin-associated galactosylated chitosan nanoparticles for hepatocyte-targeted delivery

In this study a new chitosan (CS) derivative, galactosylated chitosan (GC), was synthesized and used to prepare norcantharidin-associated GC nanoparticles (NCTD-GC NPs) by taking advantage of the ionic cross-linkage between the molecules of the anti-hepatocarcinoma medicine NCTD and of the GC as carrier. NCTD-GC NPs were obtained with average particle size of 118.68 +/- 3.37 nm, entrapment efficiency of 57.92 +/- 0.40%, and drug-loading amount of 10.38 +/- 0.06%. Several important factors influencing the entrapment efficiency, drug-loading amount, and particle size of NCTD-GC NPs were studied. The characteristics of sustained and pH-sensitive release of NCTD from NCTD-GC NPs in vitro were studied. In addition, in vitro cellular uptake and cytotoxicity of nanoparticles to hepatoma cell lines SMMC-7721 and HepG2 were also investigated. In vitro, and compared to CS-based NCTD-CS NPs, NCTD-GC NPs demonstrated satisfactory compatibility with hepatoma cells and strong cytotoxicity against hepatocellular carcinoma cells. In vivo antitumor activity of NCTD-GC NPs was evaluated in mice bearing H22 liver tumors. NCTD-GC NPs displayed tumor inhibition effect in mice, better than either the free NCTD or the NCTD-CS NPs. As a hepatocyte-targeting carrier, GC NPs are potentially promising for clinical applications.

FROM THE CLINICAL EDITOR

In this paper, a galactosylated chitosan (GC), was synthesized and norcantharidin (NCTD)-associated galactosylated chitosan nanoparticles (NCTDGC NPs) were generated by coupling NCTD--an anti-hepatocarcinoma drug--and GC as carrier. Compared to chitosan nanoparticles, NCTD-GC-NPs demonstrated satisfactory compatibility with hepatoma cells and strong cytotoxicity against the cells.

Chitosan and its antimicrobial potential--a critical literature survey

Chitosan, an aminopolysaccharide biopolymer, has a unique chemical structure as a linear polycation with a high charge density, reactive hydroxyl and amino groups as well as extensive hydrogen bonding. It displays excellent biocompatibility, physical stability and processability. The term 'chitosan' describes a heterogeneous group of polymers combining a group of physicochemical and biological characteristics, which allow for a wide scope of applications that are both fascinating and as yet uncharted. The increased awareness of the potentials and industrial value of this biopolymer lead to its utilization in many applications of technical interest, and increasingly in the biomedical arena. Although not primarily used as an antimicrobial agent, its utility as an ingredient in both food and pharmaceutical formulations lately gained more interest, when a scientific understanding of at least some of the pharmacological activities of this versatile carbohydrate began to evolve. However, understanding the various factors that affect its antimicrobial activity has become a key issue for a better usage and a more efficient optimization of chitosan formulations. Moreover, the use of chitosan in antimicrobial systems should be based on sufficient knowledge of the complex mechanisms of its antimicrobial mode of action, which in turn would help to arrive at an appreciation of its entire antimicrobial potential.

One-step preparation of glycopeptide microspheres based on alpha-amino acid-N-carboxyanhydride polymerization using interfacial protocols

A type of polysaccharide-polypeptide hybrid material, chitin derivative with polypeptide side chains was prepared by the graft copolymerization of L-leucine N-carboxyanhydride triggered by water-soluble chitin (WSC). The studies on surface tension and aggregation demonstrated surface activity of WSC. Using this extraordinary property, the microspheres were synchronously obtained via interfacial polymerization. The method employed here to form the microspheres was in direct contrast to previous syntheses that used either templating method or oil-in-water emulsion. The study provided a facile approach for synthesizing microspheres with a variety of distinct polypeptide and regulated graft length, which had mimetic structure of glycoconjugation in extracellular matrix. Furthermore, the swelling capability of the microsphere in both acidic aqueous and organic solvents would give promising application in drug delivery.

In situ preparation of glycoconjugate hollow microspheres mimics the extracellular matrix via interfacial polymerization

A novel chitin-graft-polyleucine microsphere with hollow construction was prepared via ring-opening polymerization initiated with chitin based on interfacial protocol. The FT-IR and (1)H NMR analysis demonstrated the conjugation with regulated graft length. The study provided a facile one-step route to obtain microsphere with glycoconjugation structure. This hybrid polysaccharide-polypeptide microsphere may give promising application in drug delivery and tissue engineering.

Pseudomonas aeruginosa LecB is involved in pilus biogenesis and protease IV activity but not in adhesion to respiratory mucins

Pseudomonas aeruginosa expresses two lectins which are implicated in adhesion and biofilm formation. In this study, we demonstrate that P. aeruginosa LecB is involved in pilus biogenesis and proteolytic activity. Moreover, neither lectin was involved in adhesion to human tracheobronchial mucin. We infer that some of the ascribed functions are secondary effects on other systems rather than effects of the lectins themselves.