SYNTHESIS AND CHARACTERIZATION OF pH-SENSITIVE N-SUCCINYL CHITOSAN HYDROGEL AND ITS PROPERTIES FOR BIOMEDICAL APPLICATIONS

A Closed Loop Stimuli-Responsive Concanavalin A-Loaded Chitosan-Pluronic Hydrogel for Glucose-Responsive Delivery of Short-Acting Insulin Prototyped in RIN-5F Pancreatic Cells

The optimal treatment of diabetes (in particular, type 1 diabetes-T1D) remains a challenge. Closed-loop systems (implants/inserts) provide significant advantages for glucose responsivity and providing real-time sustained release of rapid-acting insulin. Concanavalin A (ConA), a glucose affinity agent, has been used to design closed-loop insulin delivery systems but not without significant risk of leakage of ConA from the matrices and poor mechanical strength of the hydrogels impacting longevity and control of insulin release. Therefore, this work focused on employing a thermoresponsive co-forming matrix between Pluronic F-127 (PL) and structurally robust chitosan (CHT) via EDC/NHS coupling (i.e., covalent linkage of -NH2 from CHT and ConA to the -COOH of PL). The system was characterized for its chemical structure stability and integrity (FTIR, XRD and TGA), injectability, rheological parameters and hydrogel morphology (Texture Analysis, Elastosens TM Bio2 and SEM). The prepared hydrogels demonstrated shear-thinning for injectability with a maximum force of 4.9 ± 8.3 N in a 26G needle with sol-gel transitioning from 25 to 38 °C. The apparent yield stress value of the hydrogel was determined to be 67.47 Pa. The insulin loading efficiency within the hydrogel matrix was calculated to be 46.8%. Insulin release studies revealed glucose responsiveness in simulated glycemic media (4 and 10 mg/mL) over 7 days (97%) (305 nm via fluorescence spectrophotometry). The MTT studies were performed over 72 h on RIN-5F pancreatic cells with viability results >80%. Results revealed that the thermoresponsive hydrogel is a promising alternative to current closed-loop insulin delivery systems.

Synthesis and characterization of thiazolium chitosan derivative with enhanced antimicrobial properties and its use as component of chitosan based films

In this work, chemical modification of chitosan using cationic thiazolium groups was investigated with the aim to improve water solubility and antimicrobial properties of chitosan. Enzymatic synthesis and ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) chemistry were employed to synthesize and attach to chitosan through the amine groups the molecule bearing thiazolium moieties, quaternized 4-(2-(4-methylthiazol-5-yl) ethoxy)-4-oxobutanoic acid (MTBAQ). On the basis of Fourier transform infrared spectroscopy (FTIR), elemental analysis and solid state nuclear magnetic resonance (ssNMR), around 95 % of the available amine groups of chitosan (of 25 % degree of acetylation) reacted. The resulting derivative was water soluble at physiological pH and exhibit excellent antimicrobial activity against Listeria innocua, Staphylococcus epidermidis, Staphylococcus aureus and Methicillin Resistant S. aureus Gram-positive bacteria (MIC = 8-32 μg/ mL), whereas its efficiency decreases against fungi Candida albicans and Eschericia coli Gram-negative bacterium. Subsequently, the thiazolium chitosan derivative was employed as antimicrobial component (up to 7 wt%) of chitosan/glycerol based films. The incorporation of the chitosan derivative does not modify significantly the characteristics of the film in terms of thermal and mechanical properties, while enhances considerably the antimicrobial activity.

Chitosan Based Materials in Cosmetic Applications: A Review

This review provides a report on the properties and recent advances in the application of chitosan and chitosan-based materials in cosmetics. Chitosan is a polysaccharide that can be obtained from chitin via the deacetylation process. Chitin most commonly is extracted from cell walls in fungi and the exoskeletons of arthropods, such as crustaceans and insects. Chitosan has attracted significant academic interest, as well as the attention of the cosmetic industry, due to its interesting properties, which include being a natural humectant and moisturizer for the skin and a rheology modifier. This review paper covers the structure of chitosan, the sources of chitosan used in the cosmetic industry, and the role played by this polysaccharide in cosmetics. Future aspects regarding applications of chitosan-based materials in cosmetics are also mentioned.

Laccase Cross-Linked Ultraporous Aluminas for Sustainable Biodegradation of Remazol Brilliant Blue R

Over the past few decades, enzyme-based green and sustainable chemistry has attracted extensive research attention, which provides a promising alternative to the conventional treatment methods of recalcitrant micropollutants. However, enzyme denaturation and stability loss remain critical challenges for its potential applications in industrial wastewater treatment. In this study, laccase from Trametes versicolor (laccase T.) was cross-linked immobilized by ultraporous alumina (UPA) for the sustainable biodegradation of Remazol Brilliant Blue R (RBBR). Through sequential use of an aminosilane coupling agent (3-aminopropyl)triethoxysilane (APTES) and bifunctional cross-linker glutaraldehyde (GA), the synthesized biocatalysts showed better immobilization performances (about 4-fold to physical adsorption). The GA concentration considerably affected the laccase T. cross-linking degree, while the GA post-treatment protocol showed the highest laccase T. immobilization yield with lower activity recovery. Moreover, the biocatalyst stabilities including pH stability, thermal stability, storage stability, and reusability were also studied. Tolerance to broader pH and temperature ranges, better storage stability, good reusability of laccase T. cross-linked UPA(γ) biocatalysts, and their continuous RBRR biodegradation efficiency highlight the potentials of enzyme-based inorganic materials in industrial wastewater treatment, which can broaden our understanding of their practical applications in environmental fields.

Development of polycarbonate urethane-based materials with controlled diclofenac release for cartilage replacement

Hydrogels are very promising human cartilage replacement materials since they are able to mimic its structure and properties. Besides, they can be used as platforms for drug delivery to reduce inflammatory postsurgical reactions. Polycarbonate urethane (PCU) has been used in orthopedic applications due to its long-term biocompatibility and bio-durability. In this work, PCU-based hydrogels with the ability to release an anti-inflammatory (diclofenac) were developed, for the first time, for such purpose. The materials were reinforced with different amounts of cellulose acetate (CA, 10%, 15%, and 25% w/w) or carbon nanotubes (CNT, 1% and 2% w/w) in order to improve their mechanical properties. Samples were characterized in terms of compressive and tensile mechanical behavior. It was found that 15% CA and 2% CNT reinforcement led to the best mechanical properties. Thus, these materials were further characterized in terms of morphology, wettability, and friction coefficient (CoF). Contrarily to CNTs, the addition of CA significantly increased the material's porosity. Both materials became more hydrophilic, and the CoF slightly increased for PCU + 15%CA. The materials were loaded by soaking with diclofenac, and drug release experiments were conducted. PCU, PCU + 15%CA and PCU + 2%CNT presented similar release profiles, being able to ensure a controlled release of DFN for at least 4 days. Finally, in vitro cytotoxicity tests using human chondrocytes were also performed and confirmed a high biocompatibility for the three studied materials.

Evaluation of an Injectable Hydrogel Based on Hyaluronic Acid-chitosan/β-glycerophosphate-loaded Mesenchymal Stem Cells in Enhancing the Therapeutic Efficacy of Myocardial Infarction

Myocardial infarction (MI), which is due to cardiac dysfunction, results in morbidity and mortality. Moreover, the cellular activity of transplanted mesenchymal stem cells (MSCs)generally limits their therapeutic efficacy in the treatment of MI. Here, inject able hyaluronic acid-chitosan/β-glycerophosphate (HA-CS/β-GP) hydrogel-loaded MSCs were prepared, after which their effects on the treatment of MI were investigated. The synthesized HA-CS/β-GP hydrogels exhibited swelling ratio (SR), an in vitro degradation value, and a gelatin time of 82.19 ± 4.1, 88.18% ± 2.4%, and 9 s, respectively. Further, rheological studies revealed that the elastic modulus of the HA-CS/β-GP hydrogels was ≥230 Pa, exhibiting large elastic to viscous modulus ratio, which indicated their mechanical strength. Furthermore, the in vitro 3T3 cell and MSC culture studies confirmed the good biocompatibility of the HA-CS and HA-CS/β-GP hydrogels. The implantation of the synthesized hydrogels in the mouse MI model considerably improved the therapeutic effect of the MSCs (enhanced cardiac function, reduced cardiomyocyte apoptosis, and increased vascularization) for the first time. The innovative synergistic strategy of combining injectable HA-CS and HA-CS/β-GP hydro gels with MSCs might be suitable for the effective treatment of cardiac morbidity due to MIs. This article is protected by copyright. All rights reserved.

Fungal Chitosan-Derived Biomaterials Modified with Kalanchoe pinnata as Potential Hemostatic Agents-Development and Characterization

Massive blood loss is still a great challenge for modern medicine. To stop the hemorrhage during the surgery or after injury apart from suturing or electrocoagulation, the most efficient method of hemostasis restoration is the use of hemostatic agents. Although there are numerous products on the market, there is still a need for biomaterials that are capable of fast and efficient bleeding management without affecting wound closure or embolism. Chitosan is known for its hemostatic activity; however, its quite poor mechanical properties and heterogenous chemical composition still needs some improvements to become superior compared to biological adhesives. The following study deals with the preparation and evaluation of chitosan-derived natural biomaterials containing Kalanchoe pinnata extract with the potential application as a blood-clotting agent. The materials were obtained under microwave-assisted conditions in two different forms (granules/dressing), whose chemical structure and morphology were studied. Their antioxidant properties have been proven. The chitosan-derived hemostatic agents exhibited superior blood sorption abilities and lack of cytotoxicity to L929 mouse fibroblasts. The study also showed the differences in biological properties depending on their preparation method. The potential mechanism of action was proposed as well as their potential in hemostasis revival.

Development and Evaluation of Superabsorbent Hydrogels Based on Natural Polymers

Superabsorbent hydrogels (SAHs) are three dimensional networks formed by polymers that can absorb aqueous solution of over 100% of their initial weight. This work aimed to develop and characterize SAHs of Chitosan/Xanthan gum (CG), Chitosan/Alginate (CA) and controlled Chitosan (C), Xanthan gum (G), and Alginate (A) produced using “onion-like” methodology. The swelling performance, the morphological structure, the crystallinity, and the Fourier transformed infrared spectroscopy characteristics of SAH were used for the characterization of polyelectrolytes complex. Swelling analysis showed that chitosan has a strong influence on the maintenance of hydrogels structure after swelling, mainly in the acid environment (pH = 2). The chitosan hydrogel presented around 3000% of acidic fluid absorption after 24 h. The chitosan:xanthan gum (1:1 and 2:1 named as C1G1 and C2G1, respectively) hydrogels were the best combination regarding swelling performance in an acid environment, reaching 1665% and 2024%, respectively, as well at pH 7.0, presenting 1005% (C1G1) and 667% (C2G1). Scanning electron microscopy analysis showed samples with pores, and with different shapes. The X-ray diffraction showed the presence of a characteristic peak at 2θ = 20° in all developed composition because of the crystalline nature of chitosan. This work shows the possibility of developing eco-friendly biopolymer-based SAHs at a low cost with a good swelling capacity and stability.