Genipin-crosslinked chitosan/alginate/alumina nanocomposite gels for 3D bioprinting

Characterization of Chitosan Hydrogels Obtained through Phenol and Tripolyphosphate Anionic Crosslinking

Chitosan is a deacetylated polymer of chitin that is extracted mainly from the exoskeleton of crustaceans and is the second-most abundant polymer in nature. Chitosan hydrogels are preferred for a variety of applications in bio-related fields due to their functional properties, such as antimicrobial activity and wound healing effects; however, the existing hydrogelation methods require toxic reagents and exhibit slow gelation times, which limit their application in biological fields. Therefore, a mild and rapid gelation method is necessary. We previously demonstrated that the visible light-induced gelation of chitosan obtained through phenol crosslinking (ChPh) is a rapid gelation method. To further advance this method (<10 s), we propose a dual-crosslinked chitosan hydrogel obtained by crosslinking phenol groups and crosslinking sodium tripolyphosphate (TPP) and the amino groups of chitosan. The chitosan hydrogel was prepared by immersing the ChPh hydrogel in a TPP solution after phenol crosslinking via exposure to visible light. The physicochemical properties of the dual-crosslinked hydrogels, including Young's moduli and water retentions, were subsequently investigated. Young's moduli of the dual-crosslinked hydrogels were 20 times higher than those of the hydrogels without TPP ion crosslinking. The stiffness could be manipulated by varying the immersion time, and the water retention properties of the ChPh hydrogel were improved by TPP crosslinking. Ion crosslinking could be reversed using an iron chloride solution. This method facilitates chitosan hydrogel use for various applications, particularly tissue engineering and drug delivery.

Composites based on alginate containing formylphosphazene-crosslinked chitosan and its Cu(II) complex as an antibiotic-free antibacterial hydrogel dressing with enhanced cytocompatibility

Hydrogels based on chitosan or alginate biopolymers are believed to be desirable for covering skin lesions. In this research, we explored the potential of a new composite hydrogels series of sodium alginate (Alg) filled with cross-linked chitosan to use as hydrogel wound dressings. Cross-linked chitosan (CSPN) was synthesized by Schiff-base reaction with aldehydated cyclophosphazene, and its Cu(II) complex was manufactured and identified. Then, their powder suspension and Alg were transformed into hydrogel via ion-crosslinking with Ca2+. The hydrogel constituents were investigated by using FTIR, XRD, rheological techniques, and thermal analysis including TGA (DTG) and DSC. Moreover, structure optimization calculations were performed with the Material Studio 2017 program based on DFT-D per Dmol3 module. Examination of Alg's interactions with CSPN and CSPN-Cu using this module demonstrated that Alg molecules can be well adsorbed to the particle's surface. By changing the dosage of CSPN and CSPN-Cu, the number and size of pores, swelling rate, degradation behavior, protein absorption rate, cytotoxicity and blood compatibility were changed significantly. Subsequently, we employed erythromycin as a model drug to assess the entrapment efficiency, loading capacity, and drug release rate. FITC staining was selected to verify the hydrogels' intracellular uptake. Assuring the cytocompatibility of Alg-based hydrogels was approved by assessing the survival rate of fibroblast cells using MTT assay. However, the presence of Cu(II) in the developed hydrogels caused a significant antibacterial effect, which was comparable to the antibiotic-containing hydrogels. Our findings predict these porous, biodegradable, and mechanically stable hydrogels potentially have a promising future in the wound healing as antibiotic-free antibacterial dressings.

Chitosan-Based Biomaterials: Insights into Chemistry, Properties, Devices, and Their Biomedical Applications

Chitosan is a marine-origin polysaccharide obtained from the deacetylation of chitin, the main component of crustaceans’ exoskeleton, and the second most abundant in nature. Although this biopolymer has received limited attention for several decades right after its discovery, since the new millennium chitosan has emerged owing to its physicochemical, structural and biological properties, multifunctionalities and applications in several sectors. This review aims at providing an overview of chitosan properties, chemical functionalization, and the innovative biomaterials obtained thereof. Firstly, the chemical functionalization of chitosan backbone in the amino and hydroxyl groups will be addressed. Then, the review will focus on the bottom-up strategies to process a wide array of chitosan-based biomaterials. In particular, the preparation of chitosan-based hydrogels, organic–inorganic hybrids, layer-by-layer assemblies, (bio)inks and their use in the biomedical field will be covered aiming to elucidate and inspire the community to keep on exploring the unique features and properties imparted by chitosan to develop advanced biomedical devices. Given the wide body of literature that has appeared in past years, this review is far from being exhaustive. Selected works in the last 10 years will be considered.

Graphene Oxide-Carbamoylated Chitosan Hydrogels with Tunable Mechanical Properties for Biological Applications

Chitosan (CH)-based hydrogels have been extensively researched in numerous biological applications, including drug delivery, biosensing, wound healing, and tissue engineering, to name a few. Previously, modified CH hydrogels by carbamoylation, using potassium cyanate (KCNO) as the cross-linker, have shown improvement in viscoelastic properties and biocompatibility. In this study, graphene oxide (GO) nanofillers are added to carbamoylated CH to form a nanocomposite hydrogel and study the influence of CH molecular weight (M_w) and GO loading concentrations on hydrogel properties. The physical properties (swelling, degradation, and porous structure) of the hydrogels can be tuned as required for cell attachment and spreading by varying both the GO concentration and the M_w of CH. Rheological characterization showed an improvement in the mechanical properties (storage modulus, yield stress, and viscosity) of the synthesized CH-GO hydrogels with an increase in the M_w of CH and the GO concentration. Human retinal pigmented epithelial-1 (RPE-1) cells seeded onto the prepared hydrogel scaffolds showed good cell viability, adhesion, and cell spreading, confirming their cytocompatibility, with dependence on both M_w of CH and GO loading.

Loofah-chitosan and poly (-3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) based hydrogel scaffolds for meniscus tissue engineering applications

The meniscus is a fibrocartilaginous tissue that is very important for the stability of the knee joint. However, it has a low ability to heal itself, so damage to it will always lead to articular cartilage degeneration. The goal of this study was to make a new type of meniscus scaffold made of chitosan, loofah mat, and PHBV nanofibers, as well as to describe hydrogel composite scaffolds in terms of their shape, chemical composition, mechanical properties, and temperature. Three different concentrations of genipin (0.1, 0.3, and 0.5 %) were used and the optimal crosslinker concentration was 0.3 % for Chitosan/loofah (CL) and Chitosan/loofah/PHBV fiber (CLF). Scaffolds were seeded using undifferentiated MSCs and incubated for 21 days to investigate the chondrogenic potential of hydrogel scaffolds. Cell proliferation analyses were performed using WST-1 assay, GAG content was analyzed, SEM and fluorescence imaging observed morphologies and cell attachment, and histological and immunohistochemical studies were performed. The in vitro analysis showed no cytotoxic effect and enabled cells to attach, proliferate, and migrate inside the scaffold. In conclusion, the hydrogel composite scaffold is a promising material for engineering meniscus tissue.

Biomimetic Nanomaterials: Diversity, Technology, and Biomedical Applications

Biomimetic nanomaterials (BNMs) are functional materials containing nanoscale components and having structural and technological similarities to natural (biogenic) prototypes. Despite the fact that biomimetic approaches in materials technology have been used since the second half of the 20th century, BNMs are still at the forefront of materials science. This review considered a general classification of such nanomaterials according to the characteristic features of natural analogues that are reproduced in the preparation of BNMs, including biomimetic structure, biomimetic synthesis, and the inclusion of biogenic components. BNMs containing magnetic, metal, or metal oxide organic and ceramic structural elements (including their various combinations) were considered separately. The BNMs under consideration were analyzed according to the declared areas of application, which included tooth and bone reconstruction, magnetic and infrared hyperthermia, chemo- and immunotherapy, the development of new drugs for targeted therapy, antibacterial and anti-inflammatory therapy, and bioimaging. In conclusion, the authors’ point of view is given about the prospects for the development of this scientific area associated with the use of native, genetically modified, or completely artificial phospholipid membranes, which allow combining the physicochemical and biological properties of biogenic prototypes with high biocompatibility, economic availability, and scalability of fully synthetic nanomaterials.