Glycol Chitosan Research Articles

Synthesis and characterization of methacryl glycol chitosan as a novel functionally advanced thermogel for biomedical applications

Thermo-responsive hydrogels (thermogels), known for their sol-gel transition capabilities, have garnered significant interest for biomedical applications over recent decades. However, conventional thermogels are hindered by intrinsic physicochemical and functional limitations that impede their broader utility. This study introduces methacryl glycol chitosan (MGC) as a novel thermogel, offering enhanced functionality and addressing these limitations. MGCs, synthesized through N-methacrylation of glycol chitosan, exhibit tunable thermogelling and photo-crosslinking behaviors. The thermo-reversible sol-gel transition of MGCs occurs within a 21–54 °C range, adjustable by polymer concentration and methacryl substitution degree. Photo-crosslinking using UV light further enhances the mechanical properties of MGC thermogels, creating thermo-irreversible, chemically crosslinked hydrogels. MGCs show no cytotoxic effects and effectively support cell encapsulation. In vivo studies demonstrate stable crosslinking with minimal UV-induced skin damage. Due to their unique thermo-sensitivity, multi-functionality, and customizable properties, MGC thermogels are promising novel biomaterials for various biomedical applications, particularly injectable tissue engineering and cell encapsulation, thus overcoming the limitations of conventional thermogels.

Highly efficient dip catalysts using bacterial cellulose impregnated with self-crosslinked glycol chitosan and silver nanoparticles for 4-nitrophenol reduction

The application of environmentally friendly and sustainable catalysts requires efficient and safe preparation methods using cheap and renewable materials. Although many metal nanoparticles (NPs) have low colloidal stability, they are still very effective as catalysts. Using a straightforward method, we developed a bacterial cellulose–glycol chitosan–silver (BC–GCS–Ag) nanocomposite, by introducing both AgNPs and self-crosslinked GCS within the BC network. Self-crosslinking of GCS occurred during the formation of AgNPs by employing the glycol moieties for reduction to produce aldehyde functionalities, thereby forming Schiff's base bonds within the GCS structure. Using GCS, well-defined AgNPs within the BC matrix. The formation of AgNPs and the self-crosslinking of GCS were characterized using UV–visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that spherical AgNPs with a mean diameter of 10 nm exhibited a well-organized structure within the BC–GCS matrix. The BC–GCS–Ag nanocomposite was applied as dip catalyst for the reduction of 4-nitrophenol (4NP) to 4-aminophenol (4AP), chosen as a model reaction. The results showed that the catalytic reaction was completed within 4 min, with high reusability (10 times) and without loss of catalyst. The reaction followed pseudo-first-order kinetics with a high rate constant of 0.582 min−1. Therefore, the BC–GCS–Ag dip catalyst is an attractive alternative for environmentally friendly and sustainable catalysis, owing to its exceptional catalytic performance, high recyclability, and stability, as well as the minimal environmental footprint of the supporting materials.

Gelatin-based hydrogels with tunable network structure and mechanical property for promoting osteogenic differentiation

Osteoarthritis (OA) is a joint disease involving all joint components, including cartilage, calcified cartilage, and subchondral bone. The repair of osteochondral defects remains a significant challenge in orthopedics. Development of new strategies is essential for effective osteochondral injury repair. In this study, gelatin (Gel), polyethylene glycol diglycidyl ether (PEGDGE), hydroxyethyl cellulose (HEC) and chitosan (CS) were used to prepare semi-IPNs and IPNs hydrogels. Mechanical properties of Gel based hydrogels significantly improved with the semi-IPN and IPN structures. Tensile strength ranges from 238.7 KPa to 479.5 KPa, and its compressive strength ranges from 35.6 KPa to 112.7 KPa. Additionally, the stress relaxation rate increased with higher CS concentrations, ranging from 25 % to 35 %. The network structure of Gel-based hydrogels was a key factor in regulating stress relaxation. Viscoelasticity was adjusted by its network structures. Swelling and degradation behaviors of Gel based hydrogels were systematically investigated. Gel based hydrogels had good cytocompatibility. Both semi-IPN and IPN structures Gel based hydrogels could promote cell spreading and osteogenic differentiation. G10HEC1 and G10CS1 hydrogels show promise as candidates for osteochondral tissue regeneration, offering a new strategy for osteochondral tissue engineering.

Poly(Lactic-co-Glycolic Acid Nanoparticles Loaded with Docetaxel and Coated with Chitosan, Carboxymethyl Chitosan, or Glycol Chitosan.

Docetaxel (DTX) is a chemotherapeutic drug that has high toxicity and low bioavailability. To solve these problems, PLGA nanoparticles (NPs) were loaded with DTX and coated with mucoadhesive polymers; chitosan (CS), carboxymethyl chitosan (CMCS), or glycol chitosan(GCS). The NPs were characterized for size, charge, and polydispersity. The particles were explored using SEM, FTIR, DSC, and XRD. In vitro studies were performed to evaluate the mucoadhesive properties of the NPs and the drug release. The results validated the successful formation of spherical and monodispersed DTX NPs. The coated NPs exhibited highly positive charges, reaching +44.30±0.21 mV, whereas the uncoated NPs were almost neutral. The formulations demonstrated excellent encapsulation efficiency (>98%) and loading capacity (>45%). All polymers used in the coating process enhanced the mucoadhesive properties of PLGA NPs and sustained DTX release. Both the mucoadhesiveness and release were related to the used coating polymer and its concentration. The formulations were stable for up to three months in the refrigerator. In conclusion, loading DTX in PLGA NPs and coating them with CS, CMCS, or GCS provides a promising strategy to increase the NPs' residence time on mucosal surfaces, which is expected to decrease the required dose of DTX and reduce its side effects.

Light-Driven Green-Fabricated Artificial Intelligence-Enabled Micro/Nanorobots for Multimodal Phototherapeutic Management of Bladder Cancer.

Combination therapy based on precise phototherapies combined withimmunemodulation provides successful antitumor effects. In this study, a combination therapy is designed based on phototactic, photosynthetic, and phototherapeutic Chlamydomonas Reinhardtii (CHL)-glycol chitosan (GCS)-polypyrrole (PPy) nanoparticle (NP)-enhanced immunity combined with the tumor microenvironment turnover of cytotoxic Tcells and M1/M2 macrophages, which is based on photothermal GCS-PPy NPsdecorated onto the phototactic and photosyntheticCHL. Phototherapy based on CHL-GCS-PPy NPs alleviates hypoxia and modulates the tumor immunemicroenvironment, which induces tumor cell death. In particular, the precise antitumor immune response and potent immune memory induced by combining self-navigated phototherapies significantly alleviate the progression of bladder cancer in C57BL/6 mice and effectively inhibit bladder tumor growth. Furthermore, they also potentially prevent tumor recurrence, which provides a promising therapeutic strategy for clinical tumor therapy.

Probing the effects of polysaccharide hydrogel composition on the viability and pro‐angiogenic function of human adipose‐derived stromal cells

AbstractCell therapies harnessing the pro‐vascular regenerative capacities of mesenchymal stromal cell (MSC) populations, including human adipose‐derived stromal cells (hASCs), have generated considerable interest as an emerging treatment strategy for peripheral arterial disease (PAD) and its progression to critical limb ischemia (CLI). There is evidence to support that polysaccharide hydrogels can enhance therapeutic efficacy when applied as minimally‐invasive delivery systems to support MSC survival and retention within ischemic tissues. However, there has been limited research to date on the effects of hydrogel composition on the phenotype and function of encapsulated cell populations. Recognizing this knowledge gap, this study compared the pro‐angiogenic function of hASCs encapsulated in distinct but similarly‐modified natural polysaccharide hydrogels composed of methacrylated glycol chitosan (MGC) and methacrylated hyaluronic acid (MHA). Initial in vitro studies confirmed high viability (>85%) of the hASCs following encapsulation and culture in the MGC and MHA hydrogels over 14 days, with a decrease in the cell density observed over time. Moreover, higher levels of a variety of secreted pro‐angiogenic and immunomodulatory factors were detected in conditioned media samples collected from the hASCs encapsulated in the MGC‐based hydrogels compared to the MHA hydrogels. Subsequent testing focused on comparing hASC delivery within the MGC and MHA hydrogels to saline controls in a femoral artery ligation‐induced CLI (FAL‐CLI) model in athymic nu/nu mice over 28 days. For the in vivo studies, the hASCs were engineered to express tdTomato and firefly luciferase to quantitatively compare the efficacy of the two platforms in supporting the localized retention of viable hASCs through longitudinal cell tracking with bioluminescence imaging (BLI). Interestingly, hASC retention was significantly enhanced when the cells were delivered in the MHA hydrogels as compared to the MGC hydrogels or saline. However, laser Doppler perfusion imaging (LDPI) indicated that the restoration of hindlimb perfusion was similar between the treatment groups and controls. These findings were corroborated by endpoint immunofluorescence (IF) staining showing similar levels of CD31+ cells in the ligated limbs at 28 days in all groups. Overall, this study demonstrates that enhanced MSC retention may be insufficient to augment vascular regeneration, emphasizing the complexity of designing biomaterials platforms for MSC delivery for therapeutic angiogenesis. In addition, the data points to a potential challenge in approaches that seek to harness the paracrine functionality of MSCs, as strategies that increase the secretion of immunomodulatory factors that can aid in regeneration may also lead to more rapid MSC clearance in vivo.

Development and Characterization of a Novel Composite Hydrogel Biomaterial for Improved Mucoperiosteal WoundRepair.

Mucoperiosteal wound healing, as it occurs after pediatric cleft palate surgery, can be challenging due to the limitations of current treatments such as tissue flaps secured with sutures and fibrin glue. In this study, we characterized the in vitro performance of a novel composite hydrogel biomaterial designed to be employed as an in situ wound filler and enhance mucoperiosteal wound healing. We evaluated a range of photopolymerizable formulations containing methacrylated gelatin (GelMA), glycol chitosan, and bioglass microparticles. Our aim was to identify one or more formulations with an appropriate balance of properties against a set of functional requirements that we established for this application. To test the formulations against these criteria, we measured photopolymerization kinetics, mechanical properties, degradation rate, in vitro biocompatibility, and ex vivo tissue adhesion. All formulations polymerized in less than 90 s using violet light. In addition, we found that GelMA-based hydrogels were more adhesive to mucoperiosteal tissue than clinical standard fibrin glue. Inclusion of small amounts of bioglass in the formulation increased mechanical compatibility with mucoperiosteal tissue, enhanced cytoconductivity, and promoted cell proliferation. Taken together, our results support the suitability of these photopolymerized composite hydrogels as in situ mucoperiosteal wound fillers. Overall, this study lays the groundwork for investigating the in vivo, pre-clinical effectiveness of these composite hydrogels in improving mucoperiosteal wound healing outcomes.

Phototactic/Photosynthetic/Magnetic-Powered Chlamydomonas Reinhardtii-Metal-Organic Frameworks Micro/Nanomotors for Intelligent Thrombolytic Management and Ischemia Alleviation.

Thrombosis presents a critical health threat globally, with high mortality and incidence rates. Clinical treatment faces challenges such as low thrombolytic agent bioavailability, thrombosis recurrence, ischemic hypoxia damage, and neural degeneration. This study developed biocompatible Chlamydomonas Reinhardtii micromotors (CHL) with photo/magnetic capabilities to address these needs. These CHL micromotors, equipped with phototaxis and photosynthesis abilities, offer promising solutions. A core aspect of this innovation involves incorporating polysaccharides (glycol chitosan (GCS) and fucoidan (F)) into ferric Metal-organic frameworks (MOFs), loaded with urokinase (UK), and subsequently self-assembled onto the multimodal CHL, forming a core-shell microstructure (CHL@GCS/F-UK-MOF). Under light-navigation, CHL@GCS/F-UK-MOF is shown to penetrate thrombi, enhancing thrombolytic biodistribution. Combining CHL@GCS/F-UK-MOF with the magnetic hyperthermia technique achieves stimuli-responsive multiple-release, accelerating thrombolysis and rapidly restoring blocked blood vessels. Moreover, this approach attenuates thrombi-induced ischemic hypoxia disorder and tissue damage. The photosynthetic and magnetotherapeutic properties of CHL@GCS/F-UK-MOF, along with their protective effects, including reduced apoptosis, enhanced behavioral function, induced Heat Shock Protein (HSP), polarized M2 macrophages, and mitigated hypoxia, are confirmed through biochemical, microscopic, and behavioral assessments. This multifunctional biomimetic platform, integrating photo-magnetic techniques, offers a comprehensive approach to cardiovascular management, advancing related technologies.

Robust and customizable spheroid culture system for regenerative medicine

Three-dimensional cell spheroids show promise for the reconstruction of native tissues. Herein, we report a sophisticated, uniform, and highly reproducible spheroid culture system for tissue reconstruction. A mesh-integrated culture system was designed to precisely control the uniformity and reproducibility of spheroid formation. Furthermore, we synthesized hexanoyl glycol chitosan, a material with ultralow cell adhesion properties, to further improve spheroid formation efficiency and biological function. Our results demonstrate improved biological function in various types of cells and ability to generate spheroids with complex structures composed of multiple cell types. In conclusion, our spheroid culture system offers a highly effective and widely applicable approach to generating customized spheroids with desired structural and biological features for a variety of biomedical applications.

Facile preparation of interpenetrating network hydrogel adsorbent from starch- chitosan for effective removal of methylene blue in water

Hydrogels based on biopolymers have attracted considerable interest in the last decades. Herein, an interpenetrating network hydrogel (IPN-Gel) adsorbent from starch-chitosan was fabricated facilely in one-pot through tandem Schiff base reaction and photopolymerization. First, aldehyde starch (DAS) was synthesized by the reaction of soluble starch with sodium periodate. Afterward, acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), polyethylene glycol dimethacrylate (PEGDMA), photoinitiator, chitosan and DAS were dissolved in water to obtain a clear solution. Schiff base reaction between chitosan and DAS took place quickly to form the first network, and then photopolymerization of AM, AMPS, and PEGDMA occurred under ultraviolet radiation to form the second network. The preparation conditions of the as-prepared IPN-Gel were optimized with two indexes of gel mass fraction and swelling ratio. Its swelling behavior with pH and temperature change was explored. Finally, its adsorption performance was characterized with methylene blue (MB) as a model contaminant. The maximum adsorption capacity of IPN-Gel can reach 2039 mg·g−1 at pH =10. Its adsorption performance accords with Langmuir isothermal model and pseudo-second-order kinetic model and it was mainly controlled by chemisorption. This strategy is expected to found broad application prospects in the preparation of hydrogel adsorbents.

Optimization of Interfacial Properties Improved the Stability and Activity of the Catalase Enzyme Immobilized on Plastic Nanobeads.

The immobilization of catalase (CAT), a crucial oxidoreductase enzyme involved in quenching reactive oxygen species, on colloids and nanoparticles presents a promising strategy to improve dispersion and storage stability while maintaining its activity. Here, the immobilization of CAT onto polymeric nanoparticles (positively (AL) or negatively (SL) charged) was implemented directly (AL) or via surface functionalization (SL) with water-soluble chitosan derivatives (glycol chitosan (GC) and methyl glycol chitosan (MGC)). The interfacial properties were optimized to obtain highly stable AL-CAT, SL-GC-CAT, and SL-MGC-CAT dispersions, and confocal microscopy confirmed the presence of CAT in the composites. Assessment of hydrogen peroxide decomposition ability revealed that applying chitosan derivatives in the immobilization process not only enhanced colloidal stability but also augmented the activity and reusability of CAT. In particular, the use of MGC has led to significant advances, indicating its potential for industrial and biomedical applications. Overall, the findings highlight the advantages of using chitosan derivatives in CAT immobilization processes to maintain the stability and activity of the enzyme as well as provide important data for the development of processable enzyme-based nanoparticle systems to combat reactive oxygen species.

WITHDRAWN: Folic acid Grafted, cell-penetrating peptide conjugated pH-sensitive hydrophobically modified Glycol chitosan nanoparticles for drug delivery in breast cancer

Nanocarriers are an outcome of the fast development of nanotechnology; however, delivering drugs to tumor sites effectively is still a major difficulty. A pH-responsive drug carrier with good cell penetration and targeting ability was developed to release the drug exactly to the cancer site and overcome these limitations.The drug carrier FA-TAT-HGCNPs/PTX, which is pH-responsive, uses folic acid (FA) and TAT peptide to deliver paclitaxel (PTX) for target folate-receptor-overexpressing breast cancer cells. 2-(diisopropylamino) ethyl methacrylate was connected to glycol chitosan (GC) to form HGCNPs. Then TAT and HGCNPs were conjugated and FA was grafted onto the HGCNPs’ hydroxyl group. Physicochemical characterizations of FA-TAT-HGCNPs was also evaluated. The maximum DLE and EE values of the FA-TAT-HGCNPs at pH 8.0 were 74.0 ± 2.22 % and 93.7 ± 2.8 %, respectively. FA-TAT-HGCNPs, for instance, showed stability during long-term storage and lyophilization while exhibiting pH-responsive dissociation properties. The synthesized drug carrier was characterized by FTIR, XRD, SEM, HRTEM, DLS, and Zeta analysis. MTT assay exhibited the high anticancer activity of the FA-TAT-HGCNPs/PTX against the MCF-7 cells, whereas drug-free ones are highly biocompatible. The pharmacokinetic results showed twice the bioavailability of FA-TAT-HGCNPs/PTX compared to HGCNPs/PTX. Unlike FA-HGCNPs/PTX, CLSM analysis showed that FA-TAT-HGCNPs/PTX had a significantly more efficient intracellular uptake in MCF-7 cells. These data have shown the transmembrane ability of TATpeptide,the targeting effects of folate decoration, and the synergistic interaction between them.According to these findings, PTX-loaded FA-TAT-HGCNPs offer a potentially effective nanoscale drug delivery system for the treatment of breast cancer.

High efficient dip catalyst for nitrophenol reduction using bacterial cellulose impregnated self-crosslinked glycol chitosan via formation of gold nanoparticles

A simple approach was used to create an environmentally friendly dip catalyst by incorporating gold nanoparticles (AuNPs) into bacterial cellulose (BC) via glycol chitosan (GCS), which acted as both a reducing and self-crosslinking agent. The BC-GCS-AuNPs dip catalyst was analyzed using UV–Vis spectroscopy, FTIR, SEM, XRD, and TEM to confirm the formation of AuNPs and GCS self-crosslinking within the BC network. The catalyst efficacy was tested for converting 4-nitrophenol (NP) to 4-amino phenol (AP). Results demonstrated excellent catalytic performance, achieving up to 98 % within 5 min. The dip catalyst present an appealing option for green and sustainable catalysis due to its outstanding performance, stability, and reusability.

PH-responsive chitosan hollow microspheres pro-flavor based on interfacial Schiff-base bonding for controlled release of cinnamaldehyde

The strong volatility and instability of cinnamaldehyde (CA) limits its application in food and flavor industry. Combining physical encapsulation techniques and chemical bonding methods is a novel strategy to overcome this challenge. Herein, a cinnamaldehyde-chitosan hollow microsphere pro-flavor (CHMP) was developed through interfacial Schiff-base bonding reaction with an average size of 220∼800 nm. Hydrophilic macromolecules of glycol chitosan (GC) are fixed at the oil/water interface via numerous hydrophobic small molecules of CA, forming the CHMP with a positively charged surface and lipophilic cavity. Thus, physical and chemical double-barrier CA delivery system was fabricated in which CA molecules were chemically linked to GC and at the same time embedded in the particles’ core. This structure endows CHMP excellent stability and pH-responsive release abilities. After 48 d of open storage at room temperature, the retention rate of CA in CHMP powder was above 85%. CA release from CHMP exhibited a sustained release rate at neutral pH and a fast release under acidic condition. CHMP also retained excellent sensory profile and exhibited durable antibacterial performance against both Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). Therefore, rather than most of the traditional methods, this CHMP may open a new path for CA controlled release, widening their applications with multifunctionalities.

Enhanced hexanoyl glycol chitosan/tannic acid thermogels: Customizable physico-mechanical and biofunctional characteristics for biomedical applications

This study introduces HGC/TA thermogels, innovative thermosensitive hydrogels developed by integrating tannic acid (TA), a natural polyphenolic compound, into hexanoyl glycol chitosan (HGC). This unique formulation not only enhances the mechanical strength of the thermogels but also incorporates the beneficial physicochemical and biological properties of TA. Compared to conventional thermogels, including pure HGC variants, HGC/TA thermogels demonstrate significantly enhanced storage modulus and compressive strength, remarkable self-healing abilities, increased mucoadhesion, improved stability, and tunable degradation rates, all while being minimally cytotoxic. Moreover, these thermogels exhibit notable antioxidant properties, effectively counteracting free radicals, and display significant antibacterial activity against both Gram-negative E. coli and Gram-positive S. aureus. The ability to tailor the physico-mechanical and biological functions of HGC/TA thermogels by varying the TA concentration makes them highly versatile, marking them as ideal for diverse biomedical applications, particularly in wound care and tissue engineering.

Design of glycol chitosan-decorated liposomes for the intranasal delivery of hydrophilic substances: physicochemical and in vitro/in vivo biological assessment

The surface of phosphatidylcholine-based liposomes was decorated with mucoadhesive polymer glycol chitosan (GC) to enhance the penetration of hydrophilic substance encapsulated therein from the nose to the brain. The composition of coated liposomes (chitosomes) was optimized by evaluating physicochemical characteristics, including hydrodynamic diameter, zeta potential, and polydispersity index. Particle stability over time was assessed, and both in vitro and in vivo biological tests were conducted using the leading system. Deposition of the polymer onto the liposome surface increased both the particle size (from 100 nm to 150 nm) and the zeta potential (from −75 mV to +42 mV) at the optimal GC/lipid wt. ratio of 1/10. Chitosome stability depends on storage temperature, and is maintained for up to 3 months at optimal component ratio. Hemagglutination and hemolytic activity were only observed at high concentrations of components beyond optimal compositions. The encapsulation efficiency of Rhodamine B (RhB) in optimized chitosomes was approximately 80 %, which was 20–25 % higher than that observed in liposomes. The chitosomes showed enhanced cellular internalization compared to conventional liposomes. Spectrophotometric analysis revealed that nearly complete release of RhB occurred from liposomes within 7 h, while only 70 % of RhB was released from chitosomes during the same period. Fluorescence microscopy tests demonstrated that intranasal administration of chitosomes led to their effective penetration into the rat brain in vivo.

Antioxidant and antibacterial hydrogel formed by protocatechualdehyde–ferric iron complex and aminopolysaccharide for infected wound healing

To better treat bacteria-infected wounds and promote healing, new wound dressings must be developed. In this study, we obtained PA@Fe by chelating iron trivalent ions (Fe3+) with protocatechualdehyde (PA), which has a catechol structure. Subsequently, we reacted it with ethylene glycol chitosan (GC) via a Schiff base reaction and loaded vancomycin to obtain an antibacterial Gel@Van hydrogel with a photothermal response. The as-prepared Gel@Van hydrogel exhibited good injectability, self-healing, hemostasis, photothermal stability, biocompatibility, and antioxidant and antibacterial properties. Moreover, Gel@Van hydrogel achieved highly synergistic antibacterial efficacy through photothermal and antibiotic sterilization. In a mouse skin-damaged infection model, Gel@Van hydrogel had a strong ability to promote the healing of methicillin-resistant Staphylococcus aureus (MRSA)-infected wounds, indicating the great potential application value of Gel@Van hydrogel in the field of treating and promoting the healing of infected wounds.

Turning Polysaccharides into Injectable and Rapid Self-Healing Antibacterial Hydrogels for Antibacterial Treatment and Bacterial-Infected Wound Healing.

Great efforts have been devoted to the development of novel and multifunctional wound dressing materials to meet the different needs of wound healing. Herein, we covalently grafted quaternary ammonium groups (QAGs) containing 12-carbon straight-chain alkanes to the dextran polymer skeleton. We then oxidized the resulting product into oxidized quaternized dextran (OQD). The obtained OQD polymer is rich in antibacterial QAGs and aldehyde groups. It can react with glycol chitosan (GC) via the Schiff-base reaction to form a multifunctional GC@OQD hydrogel with good self-healing behavior, hemostasis, injectability, inherent superior antibacterial activity, biocompatibility, and excellent promotion of healing of methicillin-resistant Staphylococcus aureus (MRSA)-infected wounds. The biosafe and nontoxic GC@OQD hydrogel with a three-dimensional porous network structure possesses an excellent swelling rate and water retention capacity. It can be used for hemostasis and treating irregular wounds. The designed GC@OQD hydrogel with inherent antibacterial activity possesses good antibacterial efficacy on both S. aureus (Gram-positive bacteria) and Escherichia coli (Gram-negative bacteria), as well as MRSA bacteria, with antibacterial activity greater than 99%. It can be used for the treatment of wounds infected by MRSA and significantly promotes the healing of wounds. Thus, the multifunctional antibacterial GC@OQD hydrogel has the potential to be applied in clinical practice as a wound dressing.

Insights into Chitin-Degradation Potential of Shewanella khirikhana JW44 with Emphasis on Characterization and Function of a Chitinase Gene SkChi65.

Chitin, a polymer of β-1,4-linked N-acetylglucosamine (GlcNAc), can be degraded into valuable oligosaccharides by various chitinases. In this study, the genome of Shewanella khirikhana JW44, displaying remarkable chitinolytic activity, was investigated to understand its chitin-degradation potential. A chitinase gene SkChi65 from this strain was then cloned, expressed, and purified to characterize its enzymatic properties and substrate hydrolysis. Genome analysis showed that, of the 14 genes related to chitin utilization in JW44, six belonged to glycoside hydrolase (GH) families because of their functional domains for chitin binding and catalysis. The recombinant chitinase SkChi65, consisting of 1129 amino acids, was identified as a member of the GH18 family and possessed two chitin-binding domains with a typical motif of [A/N]KWWT[N/S/Q] and one catalytic domain with motifs of DxxDxDxE, SxGG, YxR, and [E/D]xx[V/I]. SkChi65 was heterologously expressed as an active protein of 139.95 kDa best at 37 °C with 1.0 mM isopropyl-β-d-thiogalactopyranoside induction for 6 h. Purified SkChi65 displayed high stability over the ranges of 30-50 °C and pH 5.5-8.0 with optima at 40 °C and pH 7.0. The kinetic parameters Km, Vmax, and kcat of SkChi65 towards colloidal chitin were 27.2 μM, 299.2 μMs-1, and 10,203 s-1, respectively. In addition to colloidal chitin, SkChi65 showed high activity towards glycol chitosan and crystalline chitin. After analysis by thin-layer chromatography, the main products were N,N'-diacetylchitobiose, and GlcNAc with (GlcNAc)2-6 used as substrates. Collectively, SkChi65 could exhibit both exo- and endochitinase activities towards diverse substrates, and strain JW44 has a high potential for industrial application with an excellent capacity for chitin bioconversion.

Enhanced gut microbiota delivery of a model probiotic (Faecalibacterium prausnitzii): Layer-by-layer encapsulation using riboflavin-conjugated sodium alginate and glycol chitosan

Faecalibacterium prausnitzii (F. prausnitzii) exhibits a variety of biological functions that make it suitable for use as a next-generation probiotic. However, its high sensitivity to oxygen and digestive fluids currently limits its application. Riboflavin is known to support the growth of F. prausnitzii in oxygen environments, but it is important that it is in close proximity to the probiotics. Layer-by-layer assembly can be used to form protective coatings around probiotics, which can protect them from adverse environmental conditions. Moreover, riboflavin can be conjugated to these coatings, thereby increasing its efficacy by bringing it close to probiotic surfaces. In this study, we therefore evaluated the potential of electrostatic layer-by-layer assembly to protect F. prausnitzii by coating them with riboflavin-alginate and glycol-chitosan layers. Initially, we showed that riboflavin could be successfully conjugated to alginate, with a grafting ratio of around 4.35%. Then, the layer-by-layer method was used to coat F. prausnitzii using cationic glycol chitosan and anionic riboflavin-alginate. The coating formed was found to have a thickness of approximately 18.5 nm. Encapsulation did not adversely affect the growth of F. prausnitzii, but it significantly enhanced its resistance to oxygen and digestive fluids. The encapsulated probiotic was shown to have enhanced mucoadhesive properties using an in vitro intestinal monolayer model. Furthermore, the encapsulated probiotics colonized the colons of rats for longer than nonencapsulated ones. These results show that coating F. prausnitzii with riboflavin-rich biopolymer layers improves its resistance to oxygen and digestive fluids, and enhances its mucoadhesion and colonization properties, which should enhance its potential as an orally administered probiotic.