Search Results (74)

Background: Chitosan (CS) crosslinked with genipin (GNP) provides a mild, non-toxic route to generate nanogels (NGs) with enhanced integrity and colloidal stability. Objectives: To develop and characterise CS-GNP NG as a novel platform for targeted cellular delivery, optimising design through physicochemical characterisation and biocompatibility evaluation. Methods: NGs were synthesised under optimised conditions by adjusting the pH of the CS solution, followed by high-intensity ultrasound (HIUS) to achieve disaggregation. Physicochemical characterisation was carried out using UV-Vis spectroscopy, FTIR, dynamic light scattering (DLS), and scanning electron microscopy (SEM). Rheological studies and SAXS analysis assessed structural properties. Biocompatibility was evaluated via MTT assay, and internalisation was monitored by fluorescence microscopy on mammalian cell lines. Results: NG formation was highly pH-dependent, with optimal configuration at pH 4.5, yielding stable, uniformly sized particles (~200 nm, ζ-potential +29 mV). Kinetic modelling showed a sigmoidal formation pattern, suggesting nucleation, growth, and stabilisation. FTIR confirmed covalent bonding between CS and GNP via primary amide bonds and Schiff bases. Rheology indicated pseudoplastic behaviour, and SAXS revealed a compact network formation. Biocompatibility assays confirmed non-cytotoxicity below 100 µg/mL and efficient cellular uptake. Conclusions: This study presents a rapid, reproducible protocol for generating colloidally stable, biocompatible NGs suitable for drug delivery. Full article

This study synthesized two eco-friendly inhibitors—a chitosan–copper metal–organic framework (CS@Cu MOF) and chitosan–Schiff base–Cu complex (Schiff–CS@Cu)—for Q345 steel protection in 3.5% NaCl/1M HCl. Electrochemical and weight loss analyses demonstrated exceptional corrosion inhibition: untreated specimens showed a 25.889 g/(m²·h) corrosion rate, while 100 mg/L of CS@Cu MOF and Schiff–CS@Cu reduced rates to 2.50 g/(m²·h) (90.34% efficiency) and 1.67 g/(m²·h) (93.56%), respectively. Schiff–CS@Cu’s superiority stemmed from its pyridine–Cu²⁺ chelation forming a dense coordination barrier that impeded Cl⁻/H⁺ penetration, whereas CS@Cu MOF relied on physical adsorption and micro-galvanic interactions. Surface characterization revealed that Schiff–CS@Cu suppressed pitting nucleation through chemical coordination, contrasting with CS@Cu MOF’s porous film delaying uniform corrosion. Both inhibitors achieved optimal performance at 100 mg/L concentration. This work establishes a molecular design strategy for green inhibitors, combining metal–organic coordination chemistry with biopolymer modification, offering practical solutions for marine infrastructure and acid-processing equipment protection. Full article

Implant-associated infections (IAIs) are major complications in dental and orthopedic implants, potentially compromising osseointegration and eventually causing implant loosening or removal. Thus, early prevention of bacterial adhesion and biofilm formation is critical for successful long-term osseointegration. Polyetheretherketone (PEEK) exhibits excellent physicochemical properties and an elastic modulus similar to bone tissue, making it a promising material for dental and orthopedic implants. However, its inherent lack of antibacterial properties limits its ability to prevent IAIs. Herein, an antibacterial coating with controlled drug release and excellent biocompatibility is designed by immobilizing minocycline (Mino)-doped carboxymethyl chitosan (CMCS) onto the PEEK surface via a polydopamine (PDA)-mediated Michael addition and Schiff base reaction. The coating is characterized by SEM, XPS, water contact angle measurements, and in vitro Mino release assays. Antibacterial activity is evaluated using the zone of inhibition (ZOI), turbidity, and colony counting assays, while biocompatibility is assessed through a SEM analysis of cell morphology and CCK-8 assay. The results show that the Mino-modified coating is successfully fabricated on the PEEK surface, achieving sustained Mino release for up to 14 days. Among the three Mino concentrations, the PEEK-0.5Mino group demonstrates the best balance of antibacterial activity and biocompatibility, highlighting its potential for preventing IAIs in orthopedic and dental applications. Full article

The hyperglycemic microenvironment in diabetic wounds predisposes them to bacterial infections, sustains chronic inflammation, and hinders therapeutic efficacy. In this study, antibiotic-loaded fast-crosslinked hybrid nanogel wound dressings (florfenicol nanogels) based on Schiff’s base bond were obtained through N, O-carboxymethyl chitosan (N, O-CMCS) and oxidized hyaluronic acid (OHA). The successfully prepared florfenicol N, O-CMCS/OHA nanogels exhibited obvious pH- and HAase-responsiveness release, which allowed it to quickly release florfenicol at infected wounds to exert on-demand antibacterial activity, as well as accelerate diabetic bacterial-infected wound healing. The nanogel dressings showed excellent antibacterial activity by destroying the bacterial cell membrane and wall. More specifically, the glucose oxidase in the dressings can catalyze the breakdown of high-concentration glucose, generating abundant ROS that directly cause cellular damage. According to the results of wound healing, the dressings showed satisfactory anti-inflammatory and therapeutic effects for the full-thickness mouse skin defect wounds. The nanogel dressings are anticipated to be excellent wound dressings to synergistically overcome the theraputic difficulty of diabetic bacterial wounds. Full article

Background: In tissue engineering, developing injectable hydrogels with tailored mechanical and bioactive properties remains a challenge. This study introduces an injectable hydrogel composite for soft tissue regeneration, composed of oxidized alginate (OA) and N-succinyl chitosan (NSC) cross-linked via Schiff base reaction, reinforced with graphene oxide (GOx) and cyclic arginylglycylaspartic acid (c-RGD). The objective was to create a multifunctional platform combining injectability, bioactivity, and structural stability. Methods: The OA/NSC/GOx-cRGD hydrogel was synthesized through Schiff base cross-linking (aldehyde-amine reaction). Characterization included FTIR (C=N bond at 1650 cm⁻¹), Raman spectroscopy (D/G bands at 1338/1567 cm⁻¹), SEM (porous microstructure), and rheological analysis (shear-thinning behavior). In vitro assays assessed fibroblast viability (MTT) and macrophage TNF-α secretion (ELISA), while ex-vivo injectability and retention were evaluated using chicken cardiac tissue. Results: The hydrogel exhibited shear-thinning behavior (viscosity: 10 to <1 Pa·s) and elastic-dominated mechanics (G′ > G″), ensuring injectability. SEM revealed an interconnected porous structure mimicking native extracellular matrix. Fibroblast viability remained ≥95%, and TNF-α secretion in macrophages decreased by 80% (30 vs. 150 pg/μL in controls), demonstrating biocompatibility and anti-inflammatory effects. The hydrogel adhered stably to cardiac tissue without leakage. Conclusions: The OA/NSC/GOx-cRGD composite integrates injectability, bioactivity, and structural stability, offering a promising scaffold for tissue regeneration. Its modular design allows further functionalization with peptides or growth factors. Future work will focus on translational applications, including scalability and optimization for dynamic biological environments. Full article

Chitosan (CS), a versatile biopolymer obtained through the deacetylation of chitin, has gained significant interest in biomedical and pharmaceutical applications due to its biocompatibility, biodegradability, and unique gel-forming capabilities. This review comprehensively analyzes CS-based gel development, covering its extraction from various natural sources, gelation mechanisms, and biomedical applications. Different extraction methods, including chemical, biological, and green techniques, are discussed regarding efficiency and sustainability. The review explores the physicochemical properties of CS that influence its gelation behavior, highlighting various gelation mechanisms such as physical, ionic, and chemical cross-linking. Recent advances in gel formation, including Schiff base reactions, Diels–Alder click chemistry, and thermosensitive gelation, have expanded the applicability of CS hydrogels. Furthermore, CS-based gels have demonstrated potential in wound healing, tissue engineering, drug delivery, and antimicrobial applications, offering controlled drug release, enhanced biocompatibility, and tunable mechanical properties. The incorporation of nanomaterials, bioactive molecules, and functional cross-linkers has further improved hydrogel performance. The current review underscores the growing significance of CS-based gels as innovative biomaterials in regenerative medicine and pharmaceutical sciences. Full article

Natural hydrogels have attracted considerable attention due to advantages of moisturizing, biocompatibility, and plasticity. In this study, a dual-network oxidized peach gum polysaccharide–carboxymethyl chitosan (OPGC) hydrogels with ultrafast self-healing ability was constructed by self-assembly using oxidized peach gum polysaccharide (OPGP) and carboxymethyl chitosan (CMCS). After complete fracture, OPGC hydrogels rapidly self-healed within 30 s due to the dual-network structure formed by the hydrogen bonds between the OPGP molecules and the Schiff base bonds between them and the CMCS. Meanwhile, the hydrogels exhibited good injectability and biocompatibility. With the increase of CMCS from 0.5 wt% to 2.5 wt%, the gel formation time of OPGC hydrogels was drastically shortened from 12 min to 3 min, while the strength and water-holding capacity were enhanced. Furthermore, experimental in vitro and in vivo animal studies demonstrated excellent drug loading capacity of OPGC hydrogels, and the release rate of bactericide could be controlled by adjusting the content of CMCS. The OPGC hydrogels have outstanding properties for potential applications in the health and medical fields. Full article

Using chitosan and polyvinyl alcohol (PVA) as substrates, active packaging composite (VPC) films based on vanillin-crosslinked PVA/chitosan with different concentrations of added vanillin were prepared and characterized. The results show that the VPC films exhibited higher tightness and hydrophobicity, lower water content and water vapor permeability, as well as better UV resistance. The potential interactions between the film groups were analyzed by SEM, FTIR, and XRD, and the results showed that the formation of Schiff base and hydrogen bond interactions affected the properties of the films. The VPC films also showed excellent antioxidant activity. Therefore, vanillin-crosslinked PVA/chitosan active films have broader application prospects as packaging materials for food preservation. Full article

Chitosan is an attractive material for developing inks for extrusion-based bioprinting of 3D structures owing to its excellent properties, including its mechanical properties and antimicrobial activity when used in wound dressings. A key challenge in formulating chitosan-based inks is to improve its gelation property to ensure reliable printing and the mechanical stability of the printed structures. To address these challenges, this article presents a novel chitosan/oxidized glucomannan composite hydrogel obtained through the combination of Schiff base and phenol crosslinking reactions. The proposed biomaterial forms soft hydrogels through Schiff base crosslinking, which can be further stabilized via visible light-induced phenol crosslinking. This dual-crosslinking approach enhances the printability and robustness of chitosan-based ink materials. The proposed chitosan/oxidized glucomannan hydrogel exhibits excellent extrudability and improved shape retention after extrusion, along with antimicrobial properties against Escherichia coli. Moreover, good cytocompatibility was confirmed in animal cell studies using mouse fibroblast 10T1/2 cells. These favorable features make this hydrogel highly promising for the extrusion-based bioprinting of complex 3D structures, such as tubes and nose-like structures, at a low crosslinker concentration and can expand the prospects of chitosan in bioprinting, providing a safer and more efficient alternative for tissue engineering and other biomedical applications. Full article

To expand the utilization of bio-based materials as flame retardants in epoxy resin (EP), a green Schiff base structural material (CSV) was synthesized via a one-pot approach employing chitosan and vanillin as the raw materials. Then, the CSV combined with 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide (DOPO) (the mass ratio between CSV and DOPO was 1:2, written as CSV-DOPO) improved the flame retardancy of the EP. When the amount of CSV−DOPO in the EP was only 3 wt%, the thermogravimetric analysis (TGA) results indicated that the residue of the EP composites was 50.6% higher than that of the EP. The combustion class of the EP/3 wt% CSV−DOPO composites achieved a UL-94 V0 rating and the limit oxygen index (LOI) reached 34.0%. The cone calorimeter test (CCT) showed that the peak heat release rate (PHHR), total heat release (THR), total smoke release (TSP), and peak carbon dioxide production (PCO₂P) of the EP/3 wt% CSV−DOPO composites decreased by 32.3%, 22.0%, 4.6%, and 51.0%, respectively, compared to the EP. The flame-retardancy mechanism was studied by scanning electron microscopy (SEM) and Raman spectra. The quenching effect of phosphorus-containing radicals, the dilution effect of noncombustible gases, and the impeding effect of the carbon layer in the condensed phase contributed collectively to the excellent flame retardancy of the EP/CSV−DOPO composites. Considering the facile preparation method and small addition amount of the flame retardant, the present work provides a convenient solution for the preparation of modified EP with good flame retardancy and heat stability, which is expected to be widely used in industries. Full article

The aim of this randomized clinical trial was to evaluate the efficacy of two different remineralising toothpastes in preventing dental caries and promoting oral health. Patients aged 6–18 years old with healthy and fully erupted first permanent molars (C1 and C2 DIAGNOdent scores) were enrolled and randomized into two groups according to the home-hydroxyapatite-based remineralising treatment used: the Trial group used zinc carbonate hydroxyapatite-based treatment (Biorepair Total Protective Repair), while the Control group used magnesium strontium carbonate hydroxyapatite conjugated with chitosan toothpaste (Curasept Biosmalto Caries Abrasion & Erosion). Dental and periodontal parameters were measured over a six-month period, including the DIAGNOdent Pen Index (primary outcome), BEWE Index, Plaque Index, Bleeding Score, Schiff Air Index, and ICDAS assessed with DIAGNOcam. A total of 40 patients were equally allocated in the two groups and finally analyzed. A significant reduction in the DIAGNOdent Pen score was reported in the Trial group after 1 month of treatment, while in the Control group, no significant change was found. The Trial group also showed a significant reduction in plaque levels after 3 months of treatment, while in the Control group, it occurred after 1 month. However, the Bleeding Score and Schiff Air Index showed no significant differences between the groups, suggesting that additional measures may be required to address gingival inflammation and hypersensitivity. The ICDAS index also showed no statistically significant changes, due to the limited duration of this study. Overall, zinc-hydroxyapatite-based toothpaste was more effective than magnesium strontium carbonate hydroxyapatite toothpaste in enhancing enamel remineralisation in the short-term period. The assigned treatments did not result in significant improvements in the oral indexes assessed in this study. Full article

The scientific interest in the chemical modification of chitosan to increase its solubility and application has led to its conjugation with Schiff bases, which are interesting scaffolds endowed with diverse biological properties. The resultant chitosan-based Schiff bases (CSBs) are widely studied in scientific literature due to the myriad of activities exerted, both catalytic and biological, including anticancer, anti-inflammatory, antioxidant, and especially antimicrobial ones. Antimicrobial resistance (AMR) is one of the major public health challenges of the twenty-first century because it represents a threat to the prevention and treatment of a growing number of bacterial, parasitic, viral, and fungal infections that are no longer treatable with the available drugs. Thus, in this review, we present a brief outline of the biological activities of CSBs as well as their complexes with metals, with a particular focus on the recent literature regarding the antimicrobial effect of these captivating derivatives. Full article

Nanotechnology has ushered in significant advancements in drug design, revolutionizing the prevention, diagnosis, and treatment of various diseases. The strategic utilization of nanotechnology to enhance drug loading, delivery, and release has garnered increasing attention, leveraging the enhanced physical and chemical properties offered by these systems. Polyamidoamine (PAMAM) dendrimers have been pivotal in drug delivery, yet there is room for further enhancement. In this study, we conjugated PAMAM dendrimers with chitosan (CS) to augment cellular internalization in tumor cells. Specifically, doxorubicin (DOX) was initially loaded into PAMAM dendrimers to form DOX-loaded PAMAM (DOX@PAMAM) complexes via intermolecular forces. Subsequently, CS was linked onto the DOX-loaded PAMAM dendrimers to yield CS-conjugated PAMAM loaded with DOX (DOX@CS@PAMAM) through glutaraldehyde crosslinking via the Schiff base reaction. The resultant DOX@CS@PAMAM complexes were comprehensively characterized using Fourier-transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). Notably, while the drug release profile of DOX@CS@PAMAM in acidic environments was inferior to that of DOX@PAMAM, DOX@CS@PAMAM demonstrated effective acid-responsive drug release, with a cumulative release of 70% within 25 h attributed to the imine linkage. Most importantly, DOX@CS@PAMAM exhibited significant selective cellular internalization rates and antitumor efficacy compared to DOX@PAMAM, as validated through cell viability assays, fluorescence imaging, and flow cytometry analysis. In summary, DOX@CS@PAMAM demonstrated superior antitumor effects compared to unconjugated PAMAM dendrimers, thereby broadening the scope of dendrimer-based nanomedicines with enhanced therapeutic efficacy and promising applications in cancer therapy. Full article

Chitosan (CS) has a natural origin and is a biodegradable and biocompatible polymer with many skin-beneficial properties successfully used in the cosmetics and pharmaceutical industry. CS derivatives, especially those synthesized via a Schiff base reaction, are very important due to their unique antimicrobial activity. This study demonstrates research results on the use of hydrogel microspheres made of [chitosan-graft-poly(ε-caprolactone)]-blend-(ĸ-carrageenan)], [chitosan-2-pyridinecarboxaldehyde-graft-poly(ε-caprolactone)]-blend-(ĸ-carrageenan), and chitosan-sodium-4-formylbenzene-1,3-disulfonate-graft-poly(ε-caprolactone)]-blend-(ĸ-carrageenan) as innovative vitamin carriers for cosmetic formulation. A permeation study of retinol (vitamin A), L-ascorbic acid (vitamin C), and α-tocopherol (vitamin E) from the cream through a human skin model by the Franz Cell measurement system was presented. The quantitative analysis of the release of the vitamins added to the cream base, through the membrane, imitating human skin, showed a promising profile of its release/penetration, which is promising for the development of a cream with anti-aging properties. Additionally, the antibacterial activity of the polymers from which the microspheres are made allows for the elimination of preservatives and parabens as cosmetic formulation ingredients. Full article

Lead contamination in water poses significant health risks, making its removal imperative. In this study, magnetic strontium ferrite (SrFe₁₂O₁₉) nanoparticles were facilely synthesized by the Pechini sol–gel method and subsequently functionalized with a novel chitosan–Schiff base ligand to obtain a novel inorganic/organic nanocomposite for removing Pb(II) ions from aqueous solutions. The chitosan–Schiff base ligand was synthesized through the reaction of chitosan with 2,4,5-trihydroxybenzaldehyde. The presence of two X-ray diffraction (XRD) peaks at 2Ɵ = 10.5° and 2Ɵ = 20.5°, alongside the characteristic SrFe₁₂O₁₉ peaks, confirmed the functionalization of the nanoparticles with the ligand. Additionally, a significant decrease in the saturation magnetization value from 40.29 emu/g in pure SrFe₁₂O₁₉ nanoparticles to 17.32 emu/g in the nanocomposite further verified the functionalization. The presence of carbon (C) and nitrogen (N) atoms in the energy-dispersive X-ray (EDX) pattern of the nanocomposite, in addition to iron (Fe), strontium (Sr), and oxygen (O), also confirmed the functionalization. The nanocomposite’s maximum adsorption capacity for Pb(II) ions was 390.63 mg/g. Moreover, the adsorption process is endothermic, spontaneous, and chemical, occurring via complexation with -C=N and -OH groups, and it fits well with the Langmuir equilibrium isotherm and the pseudo-second-order kinetic equation. Full article