An unexpected reactivity during periodate oxidation of chitosan and the affinity of its 2, 3-di-aldehyde toward sulfa drugs

A tough, strong, and fast-curing phenolic resin enabled by dopamine-grafted chitosan and polyethyleneimine-functionalized graphene

Phenolic resins are widely used for outdoor and structural wood-based panels; however, they are challenged by high curing temperatures, low curing rates, and high brittleness. Inspired by lobster epidermis hardening, a tough, strong, and fast-curing phenolic resin (named DCS/PG/PF) was proposed herein. In this approach, dopamine-grafted chitosan (DCS) and polyethyleneimine-functionalized graphene (PEI@G) were incorporated into neat phenol formaldehyde (PF) resin. The gel time and maximum curing temperature of DCS/PG/PF resin were considerably reduced from 445 s and 147.8 °C for the neat PF resin to 317 s and 127.8 °C, respectively. This was attributed to the oxidative crosslinking of catechol moieties in DCS and amino groups in PEI@G within the naturally alkaline environment of phenolic resins in addition to the high reactivity between catechol moieties and PF chains as well as between amino and PF chains. The prepared resin demonstrated a dry bonding strength of 2.56 MPa, wet bonding strength of 1.81 MPa, and debonding work of 0.714 J, exhibiting a considerable increase of 16.9 %, 52.1 %, and 95.1 %, respectively, compared with those of the PF resin. These improvements were attributed to the dense organic-inorganic hybrid crosslinking network formed in the DCS/PG/PF. Furthermore, the DCS/PG/PF resin exhibited enhanced thermal stability.

Hydrogels Based on Proteins Cross-Linked with Carbonyl Derivatives of Polysaccharides, with Biomedical Applications

Adding carbonyl groups into the hydrogel matrix improves the stability and biocompatibility of the hydrogels, making them suitable for different biomedical applications. In this review article, we will discuss the use of hydrogels based on polysaccharides modified by oxidation, with particular attention paid to the introduction of carbonyl groups. These hydrogels have been developed for several applications in tissue engineering, drug delivery, and wound healing. The review article discusses the mechanism by which oxidized polysaccharides can introduce carbonyl groups, leading to the development of hydrogels through cross-linking with proteins. These hydrogels have tunable mechanical properties and improved biocompatibility. Hydrogels have dynamic properties that make them promising biomaterials for various biomedical applications. This paper comprehensively analyzes hydrogels based on cross-linked proteins with carbonyl groups derived from oxidized polysaccharides, including microparticles, nanoparticles, and films. The applications of these hydrogels in tissue engineering, drug delivery, and wound healing are also discussed.

Eco-friendly anti-corrosion performance of chitosan modified with fused heterocyclic compound on mild steel in acidic medium

This study aims to explore the prevention of chitosan modified with a fused heterocyclic compound as a sustainable corrosion inhibitor for mild steel in 1 M HCl. Electrochemical instruments, including potentiodynamic polarization techniques, and electrochemical impedance spectroscopy (EIS), were employed to evaluate the corrosion protection performance. The outcomes showed that the chitosan modified with a fused heterocyclic compound has outstanding inhibition performance, with an inhibition effectiveness of 98.25 % at 100 ppm. The anti-corrosion features of modified chitosan were ascribed to the presence of hetero atoms in modified chitosan composite which leads to the creation of a protective layer, The modified chitosan composite behaved as mixed-typed inhibitors, as shown by the PDP results. The modified chitosan composite adsorbs on mild steel in the investigated corrosive media via chemisorption interactions, and its adsorption followed the Langmuir adsorption model. Furthermore, increasing the temperature from 303 to 333 K enhanced the corrosion rate, most likely due to the desorption of the inhibitor agent from the steel surface.

Dialdehyde carbohydrates - Advanced functional materials for biomedical applications

Dialdehyde carbohydrates (DCs) have found applications in a wide range of biomedical field due to their great versatility, biocompatibility/biodegradability, biological properties, and controllable chemical/physical characteristics. The presence of dialdehyde groups in carbohydrate structure allows cross-linking of DCs to form versatile architectures serving as interesting matrices for biomedical applications (e.g., drug delivery, tissue engineering, and regenerative medicine). Recently, DCs have noticeably contributed to the development of diverse physical forms of advanced functional biomaterials i.e., bulk architectures (hydrogels, films/coatings, or scaffolds) and nano/-micro formulations. We underline here the current scientific knowledge on DCs, and demonstrate their potential and newly developed biomedical applications. Specifically, an update on the synthesis approach and functional/bioactive attributes is provided, and the selected in vitro/in vivo studies are reviewed comprehensively as examples of the latest progress in the field. Moreover, safety concerns, challenges, and perspectives towards the application of DCs are deliberated.

Synthetic strategy towards novel composite based on substituted pyrido[2,1-b][1,3,4]oxadiazine-dialdehyde chitosan conjugate with antimicrobial and anticancer activities

Synthesis of new compounds that have biological activity is an indispensible issue in order to deal with the drug resistant bacteria. This wok reports preparation of a novel composite based on substituted pyrido[2,1-b][1,3,4] oxadiazine-dialdehyde chitosan (PODACs) conjugate. Firstly, a novel approach of synthesizing of a new substituted pyrido[2,1-b][1,3,4]oxadiazine-7-carboxylic acid (PO) is reported through reacting(Z)-N'-(1-(3-aminophenyl)ethylidene)-2-cyanoacetohydrazide with (Z)-ethyl 2-cyano-3-(pyridin-3-yl)acrylate. Then Dialdehyde chitosan (DACs) has prepared via periodat oxidation of chitosan (Cs). The synthesized compounds have studied via various spectroscopic instruments to validate their chemical structure such as nuclear magnetic resonance 1 H NMR, ¹³ C NMR, fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). The substituted pyrido [2,1-b][1,3,4]oxadiazine and the composite were evaluated for antimicrobial activity against pathogenic bacteria and unicellular fungi. The results revealed that, the composite exhibited promising antimicrobial activity against E. coli, S. aureus, B. subtilis and C. albicans where inhibition zones were 19, 18, 36 and 20 mm respectively. Furthermore, the substituted pyrido [2,1-b][1,3,4]oxadiazine and the composite were evaluated for cytotoxic activity against MCF-7 human breast cancer cell line as well as vero normal cell line. Results illustrated the prepared composite has anticancer activity against MCF7 where IC₅₀ was 238 µg/ml.

Injectable nano-composite hydrogels based on hyaluronic acid-chitosan derivatives for simultaneous photothermal-chemo therapy of cancer with anti-inflammatory capacity

Nowadays, the photothermal therapy (PTT) has received widespread attention and research by rapidly killing tumors with local high temperature. However, due to the irregular edges of tumor and the blurred boundary between normal and necrotic tissues, the desirable treatment cannot be achieved by the single PTT, and excessive heat will cause serious inflammation in local tissues. Herein, an injectable composite hydrogel is prepared by the oxidized hyaluronic acid (OHA) and hydroxypropyl chitosan (HPCS) via the imine bonds, which is employed as the delivery substrate for functional substances. In the gel medium, the mesoporous polydopamine (MPDA) nanoparticles are incorporated as the high efficiency photothermal agent and a reservoir of DOX, which can achieve the good photothermal conversion performance and pulsed drug release. Besides, the addition of the curcumin-cyclodextrin host-guest inclusion complex (CUR@NH₂-CD) in the composite hydrogel could reduce the inflammation caused by PTT. The composite hydrogel shows favorable the Hepa1-6 tumor inhibition in vivo by virtue of the comprehensive effect of the admired photothermal efficacy of MPDA, chemotherapy of DOX and anti-inflammatory of CUR. It can be predicted that the composite hydrogel has a broad prospect in the field of comprehensive therapy for tumor.

Natural organic-inorganic hybrid structure enabled green biomass adhesive with desirable strength, toughness and mildew resistance

Plant based proteins are green, sustainable, and renewable materials that show the potential to replace traditional formaldehyde resin. High performance plywood adhesives exhibit high water resistance, strength, toughness, and desirable mildew resistance. Adding petrochemical-based crosslinkers is not economically viable or environmentally benign; this chemical crosslinking strategy makes the imparted high strength and toughness less attractive. Herein, a green approach based on natural organic-inorganic hybrid structure enhancement is proposed. The design of soybean meal-dialdehyde chitosan-amine modified halloysite nanotubes (SM-DACS-HNTs@N) adhesive with desirable strength and toughness enhanced by covalent bonding (Schiff base) crosslinking and toughened by surface-modified nanofillers is demonstrated. Consequently, the prepared adhesive showed a wet shear strength of 1.53 MPa and work of debonding of 389.7 mJ, which increased by 146.8 % and 276.5 %, respectively, due to the cross-linking effect of organic DACS and toughening effect of inorganic HNTs@N. The introduction of DACS and Schiff base generation enhanced the antimicrobial property of the adhesive and increased the mold resistance of the adhesive and plywood. In addition, the adhesive has good economic benefits. This research creates new opportunities for developing biomass composites with desirable performance.

Covalent Immobilization of Natural Biomolecules on Chitin Nanocrystals

As a highly crystalline and renewable natural polymer nanomaterial, chitin nanocrystals (ChNCs) have attracted intense interest in the biomedical field. The structure of a ChNC is composed of an acetylglucosamine unit containing two hydroxyl groups and an acetyl group. The acetyl group can be converted to the active amino group through deacetylation, which is under the condition of maintaining the rod-like morphology and high crystalline property and is beneficial for the following modification and potential application. We investigated the relationship between different treatments and varied crystallinities of the modified ChNC, which obtained surface amino groups and aldehyde groups and retained high crystallinity. The natural biomolecules were covalently immobilized on the surface of the ChNC. The etherification was performed based on the hydroxyl groups. Based on the amino groups and the aldehyde groups, the carboxyamine and Knoevenagel condensation reactions were realized on ChNCs. Finally, natural biomolecule-modified ChNCs showed no or low cytotoxicity, antibacterial properties, and high antioxidant properties, which extended their potential biomedical applications.

Novel diaminoguanidine functionalized cellulose: synthesis, characterization, adsorption characteristics and application for ICP-AES determination of copper(II), mercury(II), lead(II) and cadmium(II) from aqueous solutions

In this study, the novel adsorbent diaminoguanidine-modified cellulose (DiGu.MC) was synthesized to extract mercury, copper, lead and cadmium ions from aqueous solutions and environmental water samples. The synthetic strategy involved oxidizing cellulose powder into dialdehyde cellulose (DAC) and reacting DAC with diaminoguanidine to create an imine linkage between the two reactants to form diaminoguanidine-modified cellulose (DiGu.MC). The structure and morphology of the adsorbent were studied using a variety of analytical techniques including Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) surface area measurements. Adsorption of mercury, copper, lead, and cadmium ions was optimized by examining the effects of pH, initial concentration, contact time, dose, temperature and competing ions. Under optimal adsorption conditions, the adsorption capacities of Cu²⁺, Hg²⁺, Pb²⁺, and Cd²⁺ were 66, 55, 70 and 41 mg g⁻¹, respectively. The adsorption isotherm is in very good agreement with the Langmuir isotherm model, indicating that a monomolecular layer is formed on the surface of DiGu.MC. The kinetics of adsorption are in good agreement with the pseudo-second kinetics model that proposes the chemical adsorption of metal ions via the nitrogen functional groups of the adsorbent. Thermodynamic studies have confirmed that the adsorption of heavy metals by DiGu.MC is exothermic and spontaneous. Regeneration studies have shown that the adsorbent can be recycled multiple times by removing metal ions with 0.2 M nitric acid. The removal efficiency for regeneration was over 99%. DiGu.MC is introduced as a unique adsorbent in removing mercury, copper, lead and cadmium with a simple synthetic strategy, with cheap starting materials, a unique chemical structure and fast adsorption kinetics leading to excellent removal efficiency and excellent regeneration. The mechanism of adsorption of the investigated heavy metals, is probably based on the chelation between the metal ions and the N donors of DiCu.MC.

Oxidized Chitosan-Tobramycin (OCS-TOB) Submicro-Fibers for Biomedical Applications

Chitosan (CS) is a biodegradable, biocompatible, and non-toxic natural amino-poly-saccharide with antibacterial ability, owing to its positively charged amino groups. However, the low charge density leads to poor antibacterial efficiency which cannot meet the biomedical application requirements. In this study, Tobramycin (TOB) was grafted onto the backbone of oxidized chitosan (OCS) to synthesize oxidized chitosan-tobramycin (OCS-TOB). FTIR, ¹H NMR and elemental analysis results demonstrated that OCS-TOB was successfully synthesized. OCS-TOB/PEO composite fibrous materials were produced by a self-made centrifugal spinning machine. In vitro experiments showed that cells proliferated on the submicro-fibrous OCS-TOB/PEO of appropriate concentration, and the antibacterial ability of OCS-TOB was much improved, compared with pristine CS. The results demonstrated that OCS-TOB/PEO nanofibrous materials could potentially be used for biomedical applications.

Facile route to tri-carboxyl chitin nanocrystals from di-aldehyde chitin modified by selective periodate oxidation

Chitin, a kind of polysaccharide mainly obtained from food waste, has emerged as an important biodegradable biopolymer in composite materials. The difficulty of aldehyde modification, which greatly limited the application of chitin nanocrystals, was addressed by applying a facile route of partial deacetylation followed by periodate oxidation in this study. Deacetylation occurred on the surface of both crystalline and amorphous regions, which were significantly degraded in the following periodate oxidation due to the inevitable cleavage of chitin chains, leading to an increase in the crystallinity index of obtained di-aldehyde chitin. The degree of deacetylation and periodate addition had limited improvement in the aldehyde content of di-aldehyde chitin with a maximum value of around 0.42 mmol/g. With further 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated oxidation, the carboxyl content of tri-carboxyl chitin was improved to 1.58 mmol/g, which played a critical role in the dispersion efficiency and morphology of chitin nanocrystals. The obtained rod-like chitin nanocrystals with a ζ-potential value of -42 mV and an average size of 97 nm have potential application in dye-adsorption and emulsion stabilizers.

Scaffolds Loaded with Dialdehyde Chitosan and Collagen—Their Physico-Chemical Properties and Biological Assessment

In this work, dialdehyde chitosan (DAC) and collagen (Coll) scaffolds have been prepared and their physico-chemical properties have been evaluated. Their structural properties were studied by Fourier Transform Infrared Spectroscopy with Attenuated Internal Reflection (FTIR–ATR) accompanied by evaluation of thermal stability, porosity, density, moisture content and microstructure by Scanning Electron Microscopy—SEM. Additionally, cutaneous assessment using human epidermal keratinocytes (NHEK), dermal fibroblasts (NHDF) and melanoma cells (A375 and G-361) was performed. Based on thermal studies, two regions in DTG curves could be distinguished in each type of scaffold, what can be assigned to the elimination of water and the polymeric structure degradation of the materials components. The type of scaffold had no major effect on the porosity of the materials, but the water content of the materials decreased with increasing dialdehyde chitosan content in subjected matrices. Briefly, a drop in proliferation was noticed for scaffolds containing 20DAC/80Coll compared to matrices with collagen alone. Furthermore, increased content of DAC (50DAC/50Coll) either significantly induced the proliferation rate or maintains its ratio compared to the control matrix. This delivery is a promising technique for additional explorations targeting therapies in regenerative dermatology. The using of dialdehyde chitosan as one of the main scaffolds components is the novelty in terms of bioengineering.

Chitosan Functionalization: Covalent and Non-Covalent Interactions and Their Characterization

Chitosan (CS) is a natural biopolymer that has gained great interest in many research fields due to its promising biocompatibility, biodegradability, and favorable mechanical properties. The versatility of this low-cost polymer allows for a variety of chemical modifications via covalent conjugation and non-covalent interactions, which are designed to further improve the properties of interest. This review aims at presenting the broad range of functionalization strategies reported over the last five years to reflect the state-of-the art of CS derivatization. We start by describing covalent modifications performed on the CS backbone, followed by non-covalent CS modifications involving small molecules, proteins, and metal adjuvants. An overview of CS-based systems involving both covalent and electrostatic modification patterns is then presented. Finally, a special focus will be given on the characterization techniques commonly used to qualify the composition and physical properties of CS derivatives.

Preparation, Characterization, and Biological Evaluation of Transparent Thin Carboxymethyl-Chitosan/Oxidized Carboxymethyl Cellulose Films as New Wound Dressings

Full thickness burns in which the damage penetrates deep into the skin layers and reaches underneath the muscle, compel the need for more effective cure. Herein, cross-linked carboxymethyl-chitosan (CM-chitosan) films, prepared by Schiff base association with oxidized carboxymethyl cellulose (OCMC), are investigated regarding the wound healing capacity on full thickness burn injuries in vivo. Transparent thin CM-chitosan/OCMC films are obtained with tensile strength reaching 6.11 MPa, elongation at break above 27%, and water absorption more than 800%, which operates in favor of absorbing excess exudate and monitoring the wound status. Furthermore, the nonadherent CM-chitosan/OCMC films, with satisfactory biodegradability, cell, and tissue compatibility, are readily used to the wound sites and easily removed following therapy on scalded tissue so as to alleviate the suffering from burn. The films efficiently promote epithelial and dermal regeneration compared to the control, achieving 75.9% and 94.4% wound closure, respectively, after 14 and 27 days. More importantly, CM-chitosan/OCMC films accelerate wound healing with natural mechanisms which include controlling inflammatory response, reducing apoptosis, promoting fibroblast cell proliferation, and collagen formation. In conclusion, the CM-chitosan/OCMC films elevate the repair ratio of burn injuries and have great potential for facilitating the healing process on full-thickness exuding wounds.

Therapeutic effect and immune mechanism of chitosan-gentamicin conjugate on Pacific white shrimp (Litopenaeus vannamei) infected with Vibrio parahaemolyticus

To explore the disease resistance mechanism of chitosan conjugates, chitosan-gentamicin conjugate (CS-GT) was synthesized and systematically characterized, the immune mechanism of CS-GT on Litopenaeus vannamei infected with Vibrio parahaemolyticus was further explored. The results showed that imine groups in CS-GT were effectively reduced. Dietary supplementation of CS-GT can significantly increase the survival rate, total hemocyte counts, the antioxidant and immune related enzyme activity levels of shrimps (P < 0.05), which are all dose-dependent under the experimental conditions. In addition, CS-GT can protect the hepatopancreas from invading bacteria and alleviate inflammation. Particularly, CS-GT promotes the expressions of legumain (LGMN), lysosomal acid lipase (LIPA) and Niemann-Pick type C2 (NPC2) up-regulated. It is speculated that CS-GT may stimulate the lysosome to phagocytose pathogens more effectively. In conclusions, shrimps fed with CS-GT can produce immune response via lysosome and greatly improve the disease resistance to Vibrio parahaemolyticus.

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.

Is Dialdehyde Chitosan a Good Substance to Modify Physicochemical Properties of Biopolymeric Materials?

The aim of this work was to compare physicochemical properties of three dimensional scaffolds based on silk fibroin, collagen and chitosan blends, cross-linked with dialdehyde starch (DAS) and dialdehyde chitosan (DAC). DAS was commercially available, while DAC was obtained by one-step synthesis. Structure and physicochemical properties of the materials were characterized using Fourier transfer infrared spectroscopy with attenuated total reflectance device (FTIR-ATR), swelling behavior and water content measurements, porosity and density observations, scanning electron microscopy imaging (SEM), mechanical properties evaluation and thermogravimetric analysis. Metabolic activity with AlamarBlue assay and live/dead fluorescence staining were performed to evaluate the cytocompatibility of the obtained materials with MG-63 osteoblast-like cells. The results showed that the properties of the scaffolds based on silk fibroin, collagen and chitosan can be modified by chemical cross-linking with DAS and DAC. It was found that DAS and DAC have different influence on the properties of biopolymeric scaffolds. Materials cross-linked with DAS were characterized by higher swelling ability (~4000% for DAS cross-linked materials; ~2500% for DAC cross-linked materials), they had lower density (Coll/CTS/30SF scaffold cross-linked with DAS: 21.8 ± 2.4 g/cm3; cross-linked with DAC: 14.6 ± 0.7 g/cm3) and lower mechanical properties (maximum deformation for DAC cross-linked scaffolds was about 69%; for DAS cross-linked scaffolds it was in the range of 12.67 ± 1.51% and 19.83 ± 1.30%) in comparison to materials cross-linked with DAC. Additionally, scaffolds cross-linked with DAS exhibited higher biocompatibility than those cross-linked with DAC. However, the obtained results showed that both types of scaffolds can provide the support required in regenerative medicine and tissue engineering. The scaffolds presented in the present work can be potentially used in bone tissue engineering to facilitate healing of small bone defects.

A self-healing and injectable hydrogel based on water-soluble chitosan and hyaluronic acid for vitreous substitute

Vitreous, an essential dioptric medium for the human eyes, must be filled with artificial materials once damaged. Carboxymethyl chitosan (CMCTS) is one of the most important water-soluble chitosan derivatives with improved biocompatibility and biodegradability. In this study, oxidized hyaluronic acid (OHA) was prepared as crosslinking reagent. CMCTS and OHA were used to develop a biocompatible, self-repairing and in-situ injectable hydrogel for vitreous substitutes. Results showed the hydrogel with controllable swelling properties, high transparency, acceptable cytocompatibility on mouse fibroblast L929 and histocompatibility in vivo. Furthermore, hydrogel was injected in-situ into the vitreous cavity after vitrectomy on New Zealand Rabbits, no significant and persistent adverse effects were observed during the 90-day follow-up period. In addition, the hydrogel maintained intraocular pressure of the operated eyes and the inherent position of the retina. Collectively, this injectable, biodegradable, nontoxic hydrogel possessed enormous potential to become a vitreous substitute material.

Promising alternative gum: Extraction, characterization, and oxidation of the galactomannan of Cassia fistula

Galactomannan extracted from Cassia fistula seed endosperm present little data related to the its structural characterization. This study reports the chemical characterization of the galactomannan from Cassia fistula (CF) and their oxidized derivatives. The extracted CF presented a yield of 26.5% (w/w) and the intrinsic viscosity [η] was 9.73 dL/g. 1D and 2D nuclear magnetic resonance spectroscopy (NMR) confirmed that the polysaccharide has a backbone of 4-linked β-D-mannose units, and contains galactose units as pending groups. These galactose units are linked to the central core through a (1→6) linkage and the galactomannan presented Man/Gal ratio of 3.1/1. The galactomannan from Cassia fistula presents low cytotoxicity in Vero cells with a CC₅₀ > 1000 μg/ml. The properties of CF resemble other commercially important galactomannans such as Locust bean gum. Three oxidized derivatives of CF were produced by periodate oxidation, which were carefully characterized by different structural techniques. It was observed that as the degree of oxidation increased, there was an increase in the Man/Gal ratio and a reduction in molar mass and viscosity. The polialdehyde produced may be explored as a versality material to react with amine group of the protein and amined polysaccharide to produce biomaterials.

In-situ crosslinked hydrogel based on amidated pectin/oxidized chitosan as potential wound dressing for skin repairing

Hydrogel can provide a favorable moisture environment for skin wound healing. In this study, a novel in-situ crosslinked injectable hydrogel was prepared using the water-soluble amidated pectin (AP) and oxidized chitosan (OC) through Schiff-base reaction without any chemical crosslinker. The influence of AP content on the properties of the hydrogel was systemically investigated. It showed that gelation time, pore structure, swelling capability and degradability of the hydrogel can be tuned by varying the content of amine and aldehyde groups from AP and OC. All the porous hydrogels with various AP contents (65%, 70%, and 80%) presented desirable gelation time, swelling property, high hemocompatibility and biocompatibility. Particularly, AP-OC-65 hydrogel presented superior swelling capability and better hemo- and bio-compatibility, owing to more residual amine sites in the hydrogel. Therefore, the injectable AP-OC-65 hydrogel has a greater potential for application to wound dressing or skin substitute.

Crosslinking of Chitosan with Dialdehyde Chitosan as a New Approach for Biomedical Applications

Materials based on natural high molecular compounds are particularly interesting for biomedical applications. It is known that the cross-linking agent used for preparation of biomacromolecule-based materials is as important as used biopolymer. Therefore, natural cross-linkers containing reactive carbonyl groups are of great interest especially for modifying properties of natural polysaccharides. One of the most popular cross-linking agents is glutaraldehyde. Nevertheless, the unreacted particles can be released from the cross-linked material and cause cytotoxic effects. This can be eliminated when using a cross-linker based e.g., on polysaccharides. This article describes quick and efficient synthesis of dialdehyde chitosan (DACS) and its application for the preparation of chitosan films. Materials obtained with different amount of DACS were fully characterized in terms of structure and surface morphology. Thermal and mechanical properties as well as hydrophilic character were also examined. The results obtained were compared with the materials obtained by cross-linking chitosan with low molecular weight glutaraldehyde and high molecular weight cross-linking agent based on polysaccharide-dialdehyde starch. Toxicity of all obtained materials was tested using the Microtox® test. It has been shown that due to better mechanical, thermal and surface properties as well as lower toxicity, dialdehyde chitosan is a very promising crosslinking agent.

Functionalization of developed bacterial cellulose with magnetite nanoparticles for nanobiotechnology and nanomedicine applications

This paper deals with the preparation of novel magnetic materials made from tetraaza macrocyclic Schiff base bacterial cellulose ligands with magnetite nanoparticles (Fe₃O₄NPs) through a multi-step procedure for antimicrobial and cytotoxic activities and chemotherapy in cancer treatment. First, the 2,3-dialdehyde bacterial cellulose (DABC) was chemically modified by ethylenediamine (EDA) and benzil (Bzl) in the presence of ferrous ions. Then, the magnetite nanoparticles (Fe₃O₄NPs) was produced inside the complex [Fe(DABC-EDA-Bzl)Cl₂] through a co-precipitation method. In nanobiotechnology, the magnetic [Fe₃O₄NP-INS-(DABC-EDA-Bzl)] material was showed moderate antimicrobial and cytotoxic activities against different species and cells, respectively. In particular, the magnetic [Fe₃O₄NP-INS-(DABC-EDA-Bzl)] material have not any cytotoxic activity towards peripheral blood mononucleocyte (PBMC) cells. Anti-tumor studies demonstrated that the magnetic [Fe₃O₄NP-INS-(DABC-EDA-Bzl)] material effectively inhibits the growth of the CT26 tumor model in BALB/c mice compared with other resulting materials throughout the experimental period and can be effective drug delivery in nanomedicine.

Oxidized chitosan modified electrospun scaffolds for controllable release of acyclovir

Developing a novel scaffold carrier with a sustained and controllable release profile of drug is essential to promote the effective transdermal delivery for acyclovir (ACY). In this work, electrospun polyacrylonitrile nanofibers (PAN NFs) was chemically modified with oxidized chitosan (OC). The modified fibrous scaffold was further loaded with the ACY for drug released investigation. FT-IR and NMR results revealed that the conversion of the functional group for each step has successfully occurred on the surface of the fibers. Through the in-vitro drug release and kinetic study, it demonstrated that ACY could be sustainably and controlled released from the OC modified scaffold following the Korsmeyer-Peppas model with a Fickian diffusion mechanism. The human adipose-derived stem cells and the blood combability evaluation confirmed the obtained scaffold possessed excellent cell biocompatibility and hemocompatibility. It could be concluded that the resultant OC modified scaffold based on electrospun PAN NFs opened a new potential option for the topical/transdermal drug delivery of ACY.

Potential of di-aldehyde cellulose for sustained release of oxytetracycline: A pharmacokinetic study

This study focused on the in-vivo sustained release of oxytetracycline (OTC) loaded on di-aldehyde cellulose (DAC). The periodate oxidation method was used for the synthesis of DAC. The prepared DAC-OTC material was characterized by different techniques such as Scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Transmission electron microscopy (TEM) and particle size analyzer. The pharmacokinetic studies were performed on DAC-OTC composite system and commercial tablet (COTA). The results of pharmacokinetic studies demonstrated that DAC-OTC exhibited higher area under the curve (AUC) (482.8 μghmL^-1) as compared to COTA (90.72 μghmL^-1). DAC-OTC composite system has double compartment pattern with improvement in mean residing time (MRT) and area under moment curve (AUMC_0-∞) than the commercial tablet (2.8 and 15.13 folds higher, respectively). Swelling index of DAC-OTC at different pH and pKa of OTC release imply that controlled in-vivo release in DAC-OTC composite system could be due to the simultaneous occurrence of the covalent and hydrogen bond between OTC and di-aldehyde cellulose. These results indicate that di-aldehyde cellulose may improve the in-vivo bioavailability of OTC.

A review on applications of chitosan-based Schiff bases

Biopolymers have become very attractive as they are degradable, biocompatible, non-toxic and renewable. Due to the intrinsic reactive amino groups, chitosan is vibrant in the midst of other biopolymers. Using the versatility of these amino groups, various structural modifications have been accomplished on chitosan through certain chemical reactions. Chemical modification of chitosan via imine functionalization (RR'CNR″; R: alkyl/aryl, R': H/alkyl/aryl and R″: chitosan ring) is significant as it recommends the resultant chitosan-based Schiff bases (CSBs) for the important applications in the fields like biology, catalysis, sensors, water treatment, etc. CSBs are usually synthesized by the Schiff condensation reaction between chitosan's amino groups and carbonyl compounds with the removal of water molecules. In this review, we first introduce the available synthetic approaches for the preparation of CSBs. Then, we discuss the biological applications of CSBs including antimicrobial activity, anticancer activity, drug carrier ability, antioxidant activity and tissue engineering capacity. Successively, the applications of CSBs in other fields such as catalysis, adsorption and sensors are demonstrated.

Development of High-Capacity Periodate Battery with Three-Dimensional-Printed Casing Accommodating Replaceable Flexible Electrodes

We present the development of a novel battery comprising iron(III) periodate complex cathode and zinc anode. The periodate complex [H₇Fe₄(IO₄)₃O₈] was prepared by a precipitation reaction between Fe(NO₃)₃ and NaIO₄ and was used in battery development for the first time. The periodate complex along with 14% carbon nanotubes and a polytetrafluoroethylene coating formed a stable flexible electrode, and the battery showed specific capacity as high as 300 mA h g^-1. Compared to single-electron processes in conventional cathode reactions, the possibility to significantly enhancing the cathode specific capacity via a multielectron process associated with valence change from I(VII) to I₂ is demonstrated. A novel three-dimensional printed reserve battery design comprising replaceable electrodes and acetic acid electrolyte is also presented.