Effect and mechanism of fish scale extract natural hydrogel on skin protection and cell damage repair after UV irradiation.

Skin lesions caused by ultraviolet radiation exposure seriously reduce people's life quality, safe natural products development to prevent and repair ultraviolet damage is an effective strategy. We investigated the protective and reparative effects of the natural composite gel (SE-gel) derived from fish scales on UV-irradiated skin by inhibiting reactive oxygen species (ROS) -mediated oxidative stress and inflammatory responses. Our results showed that SE-gel rich in glycine and proline had good ultraviolet absorption, water absorption, moisturizing and free radical scavenging abilities. In vitro, SE-gel could improve UV-irradiated L929 cell viability by 1.24 times via inhibiting 50% ROS production and malondialdehyde, and improving superoxide dismutase activity to reduce oxidative stress caused by UV irradiation. In UV-irradiated mouse skin damage model, SE-gel prevent UV-induced skin erythema, epidermal thickening, collagen fiber degradation and disruption, and reduced UV-induced inflammatory response via NF-κB signaling pathway, showing potential application in UV-irradiated skin damage prevention and repair.

Effects of reaction environments on the structure and physicochemical properties of chitosan and its derivatives.

The structural transformation of chitosan caused by reaction environment is one of the main factors affecting its functional properties. Herein, the effects of homogeneous and heterogeneous reactions on the structure and properties of chitosan were investigated. The pretreatment of reaction increased the deacetylation degree (DD) of chitosan and resulted in its degradation. In contrast, the effect of alkali dissolution process on the above characteristics was less than 8 %. In addition, the modification of functional groups and alkaline reaction environment leaded to further degradation and deacetylation of chitosan. The alkali swelling increased the specific surface area of chitosan particles, but not completely destroy its internal structure to ensure the uniformity of reaction. Interestingly, the homogeneous modification of dissolved chitosan at lower temperature reduced the degree of substitution (DS) of its derivatives but made them exhibit self-assembly properties. This study provided theoretical basis for precise preparation and application of chitosan derivatives.

Homogeneous deacetylation and degradation of chitin in NaOH/urea dissolution system.

Since being discovered, alkali/urea has been widely used in the dissolution of natural polysaccharides and the preparation of functional materials such as hydrogels, fibers, films and nanoparticles. This work will focus on verifying the structural stability, homogeneous degradation and deacetylation of chitin in alkali-soluble systems. The chitin was dissolved in NaOH/urea solution and stored at different temperature. At the specific time, the structure, viscosity, acetylation degree (DA) and biocompatibility of chitin and prepared chitosan were determined. The results indicated that dissolution process did not affect the structure and bioactivity of chitin. However, with the increase of storage time and temperature, chitin undergone significant homogeneous deacetylation (DA from 99.5% to 33.2%) and degradation (viscosity from 9284 cP to 1538 cP), accompanying by changes in crystalline structure and thermal stability. Moreover, the processed chitins were no-toxic for the biomedicine applications. This work will provide new ideas for the application of alkali-soluble systems.

A composite sponge based on alkylated chitosan and diatom-biosilica for rapid hemostasis.

Rapid control of bleeding is of great significance in military trauma and traffic accidents. In this study, alkylated chitosan (AC) and diatom biosilica (DB) were combined to develop a safe and effective hemostatic composite sponge (AC-DB sponge) for hemorrhage control. Due to the procoagulant chemical structure of AC-DB sponge, it exhibited rapid hemostatic ability in vitro (clotting time was shortened by 78% than that of control group), with favorable biocompatibility (hemolysis ratio < 5%, no cytotoxicity). The strong interface effect between AC-DB sponge and blood induced the erythrocyte and platelets activation, deformation and aggregation, intrinsic coagulation pathway activation, resulting in significant coagulation acceleration. AC-DB sponge had excellent performance in in vivo assessments with shortest clotting time (106.2 s) and minimal blood loss (328.5 mg). All above results proved that AC-DB sponge had great potential to be a safe and rapid hemostatic material.

Quantitative evaluation of the antibacterial effectiveness and efficiency of chitosan considering the effect of neutralization.

In the present research, an optimized liquid medium which had no neutralizing effect to chitosan was developed. Moreover, magnesium chloride (MgCl2) was identified to be able to absolutely neutralize the antibacterial activity of chitosan and its derivatives. Took the two results together, the minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) of chitosan were precisely quantified through a further improved method based on the optimized medium and the relation curve between antibacterial rate and reaction time was obtained with the help of MgCl2 neutralizer. The MBC and MIC of chitosan were all 30 µg/mL against Staphylococcus aureus and Escherichia coli, and 100 µg/mL of chitosan acetate could reach 100 % of antibacterial rate within 3 min. Furthermore, coordination between magnesium ions and chitosan as well as reduced zeta potential of chitosan caused by coordination were inferred to be the neutralizing mechanism of MgCl2 neutralizer.

Temperature sensitive self-assembling hydroxybutyl chitosan nanoparticles with cationic enhancement effect for multi-functional applications.

Hydroxybutyl chitosan (HBC) with different degree of substitution (DS) were prepared using a homogeneous reaction system (KOH/urea), which could achieve temperature-dependent reversible morphological transition in aqueous solution. During hydrophobic assembly, amino groups on HBC chains exposed on the surface of nanoparticles formed a poly-cationic structure. The structure of HBCs was characterized by FTIR, 13C NMR, XRD, TGA and rheology. The morphology and assembly mechanism of HBC nanoparticles were studied by TEM, AFM and DLS. Also, the results of coagulation, bacteriostatic, superoxide anion clearance and anionic contaminant removal tests suggested that HBC nanoparticles had excellent flocculation and removal effect of anionic composites. Moreover, the cytocompatibility test indicated that HBC could effectively promote proliferation and division of mouse fibroblast, mouse embryonic fibroblast and rat bone marrow mesenchymal stem cells. These cationic HBC nanoparticles exhibited great potential in multi-functional applications.

Mechanically and functionally strengthened tissue adhesive of chitin whisker complexed chitosan/dextran derivatives based hydrogel.

Schiff base reaction crosslinking hydrogels are advantageous by rapid formation and absence of external crosslinkers. However, poor mechanical hindered their broader applications. Here, a mechanically strengthened tissue adhesive was constructed through incorporation of chitin nano-whiskers (CtNWs) with a Schiff base crosslinking hydrogel of carboxymethyl chitosan (CMCS) and dextran dialdehyde (DDA). The optimal formulation of complexed hydrogel exhibited 1.87 folds higher compressive stress than non-complexed and 1.51 time higher adhesive strength on porcine skin. The complexed hydrogel exhibited negligible cytotoxicity, anti-swelling performance in PBS, optimum antibacterial and hemostatic capacities. In vivo implantation studies confirmed the complexed hydrogel was degradable without long-term inflammatory responses. Desirable efficacy of injectable complexed hydrogel as hemostat was demonstrated in rat liver injury model, which could avoid severe postoperative adhesion and necrosis as observed in the treatment with commercial 3 M™ vetbond™ tissue adhesive. The results highlighted that the complexed hydrogel potentiated rapid hemostasis and wound repair applications.

Thermo/photo dual-crosslinking chitosan-gelatin methacrylate hydrogel with controlled shrinking property for contraction fabrication.

Stimuli-responsive gel volume variation is reversible and has shown promising applications, which may be potential for contraction or expansion fabrication, generating shrinking or swelling volume of the original. In this study, a thermo/photo dual-crosslinking hydrogel is prepared with methacrylated hydroxylbutyl chitosan (MHBC) and gelatin methacrylate (GelMA). The M/G hydrogel undergoes sol-gel phase transition under room temperature and shrinking deformation upon elevating temperature. Besides nontoxicity and biodegradability, dual crosslink endowed the composite hydrogel with strengthened and tunable mechanical property, controlled and repeatable contraction property in response to temperature elevation from 25 ℃ to 37 ℃, and enhanced cell adhesion in 3D culture. These peculiarities of M/G hydrogel provide great potential for application in contraction fabrication to acquire high resolution or small scale features that may be limited by fabrications devices.

Evaluation of structure transformation and biocompatibility of chitosan in alkali/urea dissolution system for its large-scale application.

Alkali/urea, a green dissolution system for chitosan, have been widely used in preparation of chitosan-derived materials. However, there are no related reports detail the structure stability and biocompatibility of chitosan in alkali/urea, which are important for its large-scale application. In this work, chitosan was dissolved in KOH/urea solution and stored at different temperature for different time. The structure, viscosity, molecule weight (Mw), degree of deacetylation (DD), and biocompatibility of chitosan were determined. The Mw of chitosan decreased from 1011 KDa to 827-834 KDa, and DD increased from 76.9% to 85.7-93.5% after been stored at 25 °C and 4 °C for 5 weeks. Incomplete dissolution of chitosan and increase of DD enhanced its thermal stability by forming new crystallization zone. In contrast, chitosan stored in -20 °C for 5 weeks was stable without obvious change of Mw and DD. Moreover, the processed chitosans were no-toxic and safety for the biomedicine applications.

Temperature responsive self-assembled hydroxybutyl chitosan nanohydrogel based on homogeneous reaction for smart window.

Chitosan (CS) based self-assembled nanohydrogels are considered as promising platform for biomedicine, petrochemical, agricultural and food applications due to their unique biodegradability, nano-interface effect, and intelligent responsiveness. However, the most CS derivatives are prepared in heterogeneous system, which is unstable and environmentally unfriendly. In this work, a series of hydroxybutyl chitosan (HBC) was synthesized based on a green and homogeneous system (potassium hydroxide (KOH)/urea), which given this derivative interesting temperature responsive phase transformation behavior. HBC could change from dissolved state into nanohydrogel state in deionized water, when the temperature exceed its critical phase change temperature, and this process could be repeated more than 50 cycles (one cycle/day) without coagulation. The nanohydrogels solution exhibited concentration and temperature-dependent ultraviolet absorption and visible light regulation, which had great application potential in smart windows. This study provided a novel preparation method and extended the application of chitosan-based temperature responsive self-assembled nanohydrogels.

Preparation and characterization of chitosan from crab shell (Portunus trituberculatus) by NaOH/urea solution freeze-thaw pretreatment procedure.

The effect of NaOH/urea solution freeze-thaw pretreatment to the chitosan of purity and the degree of deacetylation from the crab shell was examined. Higher purity chitosan (CS1) was prepared. On this basis, the raw materials after the first demineralization were pretreated with NaOH/urea solution freeze-thaw under different freeze-thaw situations. The produced chitosans (CS1-CS4) were characterized in the ash content, solubility, protein content, degree of deacetylation, viscosity average molecular weight, SEM, FTIR, XRD, antimicrobial activity. The results showed that the freeze-thaw process had advantageous influence on decreasing the ash content and increasing degree of deacetylation and antibacterial activity. Moreover, the antibacterial property of the extracted chitosans seemed to be positively related to their degree of deacetylation. It is concluded that CS4 had the lowest ash content (0.052%), the highest degree of deacetylation (86.02%) and the greatest antibacterial activity. Therefore, we recommend CS4 as agent for industrial and pharmaceutical applications.

The toughness chitosan-PVA double network hydrogel based on alkali solution system and hydrogen bonding for tissue engineering applications.

Biocompatibility and mechanical properties have always been important indicators for the application of hydrogel materials in tissue engineering. In this work, a high strength and toughness chitosan-poly (vinyl alcohol) (PVA) DN (double network) hydrogel based on multiple hydrogen bonding interactions was prepared by applying the simple freezing-heating alternate treatment to the chitosan-PVA alkaline solution. The PVA first network was prepared by freeze crystallization, and the chitosan second network was constructed by raising the chitosan/KOH/urea temperature to 45 °C. The dynamic hydrogen bonding presented in the first PVA network and the second chitosan network given the hydrogel superior compressive (60%-230 KPa), tensile (152 KPa-360%), recoverability (90.77% after 5 cycles) and anti-swelling properties. The results of in vitro cell compatibility and in vivo subcutaneous implantation in rats both indicated that the chitosan-PVA DN hydrogel had the ability to promote cell attachment and wound healing. This DN hydrogel based on hydrogen bonding is expected to be applied in the tissue engineering repair. In addition, the hydrogel preparation process is simple and non-toxic, which provides a reference for the production of green and safe tissue engineering hydrogels.

Construction of physical-crosslink chitosan/PVA double-network hydrogel with surface mineralization for bone repair.

Weak mechanical properties, lack biocompatibility and relatively bioinert are formidable obstruct in application of bone repair materials. Multifunctional composite materials have been considered as a viable solution to this problem. Here, a new double network (DN) hydrogel was constructed by physical cross-linking of medical grade poly (vinyl alcohol) (PVA) and chitosan in KOH/urea dissolution system. The obtained hydrogel demonstrated excellent tensile strength (0.24 MPa), elongation at break (286%), and high compressive strength (0.11 MPa on the strain of 60%). Our studies showed that the prepared hydrogel had excellent biocompatibility in vitro and the introduction of hydroxyapatite (HAp) by surface mineralization imparted hydrogel the ability to induce rat bone marrow stem cells (rBMSCs) differentiation. The in vivo experiments revealed that the surface mineralized double network hydrogel significantly accelerated simultaneous regeneration of bone defects in a rabbit bone defect model. All the results indicated that this hydrogel has the potential as a bone repair material.

Nasal adaptive chitosan-based nano-vehicles for anti-allergic drug delivery.

Allergic rhinitis (AR) was a chronic airway inflammatory disease. Nasal administration showed superiorities due to its effective drug absorption. Cetirizine (CTZ) was a common H1-antihistamine in allergic disorders therapy, while hydrophobicity and irritation to nasal mucosa limited its application. In this regard, deoxycholate-chitosan-hydroxybutyl nanoparticles with CTZ covalently grafted and free CTZ encapsulated (CTZ:CDHBCs-NPs) were synthesized as nasal adaptive nano-drug delivery systems. CDHBCs-NPs with various lower critical solution temperature (LCST) (29, 33, 37 °C) were prepared, with particle sizes of ~120 nm and zeta potentials of ~4 mV. In nasal condition (pH 5.5, 33 °C), the diameters of CDHBCs-NPs increased slightly (~129 nm to ~134 nm) because of the pH-responsive expansion. Burst release of free CTZ from CDHBC-29-NPs (~76%) was significantly (p < 0.05) accelerated compared with that of CDHBC-33-NPs and CDHBC-37-NPs (~60%), owing to thermo sensitive drug squeeze out (T > LCST). Incubating with lysozyme (30 µg/mL), CDHBCs-NPs swelled and exhibited ~2-fold increase (p < 0.01) of sizes, with additional CTZ releasing (~5%) attributing to the digestion of polysaccharide backbone covalent connected with CTZ. It could be speculated that stimuli-responsive CDHBCs-NPs might hold tremendous potential as nasal adaptive delivery vehicles in allergic airway inflammatory diseases therapy.

The green and stable dissolving system based on KOH/urea for homogeneous chemical modification of chitosan.

The novel solvent (0.25 M KOH/0.01 M urea alkaline solution) was used to successfully dissolve chitosan without freezing-thawing cycles, for the first time. The results from XRD, FTIR, and 13CNRM proved that KOH/urea solution could destroy the hydrogen bonds between chitosan chains more efficiently than NaOH/urea solution. The dynamic light scattering, rheology, viscosity and elemental analysis confirmed that the KOH/urea hydrogen-bonded chitosan complex had a better thermal stability at 40 °C, and no obvious deacetylation and degradation appeared in dissolution process. Subsequently, the homogeneous chemical modification of chitosan based on KOH/urea dissolution system solution was conducted at 25 °C. The FTIR and microscopic observation indicated that the carboxymethyl chitosan, N,N,N-trimethyl chitosan and hydroxyl butyl chitosan were synthetized successfully. This work provided a green and stable solvent for homogeneous chemical modification of chitosan.

Chitosan-Based Thermo/pH Double Sensitive Hydrogel for Controlled Drug Delivery.

A series of thermo/pH sensitive N-succinyl hydroxybutyl chitosan (NSHBC) hydrogels with different substitution degrees of succinyl are prepared for drug delivery. Rheology analysis shows that the gelation temperature of NSHBC hydrogels is 3.8 °C higher than that of hydroxybutyl chitosan (HBC) hydrogels. A model drug bovine serum albumin (BSA) is successfully loaded and released. NSHBC hydrogels show excellent pH sensitivity drug release behaviors. After incubation for 24 h, 93.7% of BSA is released from NSHBC hydrogels in phosphate buffer saline (PBS) (pH 7.4), which is significantly greater than that of 24.6% at pH 3.0. In contrast, the release rate of BSA from HBC is about 70.0% at pH 3.0 and 7.4. Thus, these novel hydrogels have the prominent merits of high adaptability to soluble drugs and pH sensitivity triggered release, indicating that NSHBC hydrogels have promising applications in oral drug delivery.

Preparation of composite hydroxybutyl chitosan sponge and its role in promoting wound healing.

In this work, a composite sponge was produced by physically mixing hydroxybutyl chitosan with chitosan to form a porous spongy material through vacuum freeze-drying. Hydrophilic and macroporous composite hydroxybutyl chitosan sponge was developed via the incorporation of chitosan into hydroxybutyl chitosan. The composite sponge showed higher porosity (about 85%), greater water absorption (about 25 times), better softness and lower blood-clotting index (BCI) than those of chitosan sponge and hydroxybutyl chitosan sponge. The composite sponge with good hydrophilic could absorb the moisture in the blood to increase blood concentration and viscosity, and become a semi-swelling viscous colloid to clog the capillaries. Cytocompatibility tests with L929 cells and HUVEC cells demonstrated that composite sponge were no cytotoxicity, and could promote the growth of fibroblasts. It made up for the shortcomings of hydroxybutyl chitosan with unfavorable antibacterial effect to achieve a higher level of antibacterial (>99.99% reduction). Eventually, the vivo evaluations in Sprague-Dawley rats revealed that epithelial cells attached to the composite sponge and penetrated into the interior, in addition to this, it was also proved that the composite sponge (HC-1) had a better ability to promote wound healing and helped for faster formation of skin glands and re-epithelialization. The obtained data encourage the use of this composite sponge for wound dressings.

Tough chitosan hydrogel based on purified regeneration and alkaline solvent as biomaterials for tissue engineering applications.

The chitosan based on purified regeneration could be dissolved in 6wt% aqueous NaOH without freeze-thawing cycles and acetylation processing, and such a solution system was effective and different from other dissolving methods Upon heating, a tough hydrogel was constructed from the chitosan (purified regeneration) alkaline solution. The results of XRD, TEM, SEM and rheology analysis proved that chitosan easily aggregated in the solution and formed a nanofibers network to gelate at elevated temperature and concentration. The merely chitosan hydrogel had a uniform network structure and its (5wt%) compressive fracture stress could reach 0.2MPa. Furthermore, the hydrogels exhibited excellent biodegradability, blood compatibility and cellular compatibility. Therefore, the tough chitosan hydrogels may have a wide range of applications in biomedicine.