Fabrication of triple-crosslinked gelatin/alginate hydrogels for controlled release applications

Crosslinking of gelatin Schiff base hydrogels with different structural dialdehyde polysaccharides as novel crosslinkers: Characterization and performance comparison

Few studies have been conducted on the relationship between the crosslinking ability of dialdehyde polysaccharides (DPs) with different structures and the structure and properties of hydrogels. Herein, the effects of dialdehyde sodium alginate (DSA), dialdehyde guar gum (DGG), and dialdehyde dextran (DDE) as crosslinking agents for gelatin (GE)-based hydrogels were comparatively studied. First, the structure and aldehyde content of DPs were evaluated. Subsequently, the structure, crosslinking degree, and physicochemical properties of GE/DP hydrogels were characterized. Compared with pure GE hydrogels, GE/DP hydrogels had higher thermal stability and mechanical properties. Moreover, the aldehyde content of DPs was ordered as follows: DSA < DGG < DDE. The higher crosslinking degree of the hydrogels formed by DPs with a higher aldehyde content resulted in smaller hydrogel pores, higher mechanical strength, and a lower equilibrium swelling rate. These observations provide a theoretical basis for selecting crosslinking candidates for hydrogel-specific applications.

Study the effect of different concentrations of polydopamine as a secure and bioactive crosslinker on dual crosslinking of oxidized alginate and gelatin wound dressings

Alginate hydrogels are commonly used in wound care due to their ability to maintain a moist environment, absorb fluids, and aid wound healing. However, their stability and mechanical properties can sometimes limit their effectiveness. This study explores a new approach by creating a dual network system of oxidized alginate and gelatin hydrogel crosslinked with polydopamine in a single step, with the goal of improving the mechanical properties of these hydrogels. The unique aspect of this research is the comprehensive examination of different polydopamine concentrations in dual crosslinking systems. First, alginate was modified with sodium periodate to create additional active groups on its backbone, and various polydopamine concentrations were then tested to assess their impact on the dual crosslinking network and hydrogel properties. The study involved a range of tests, including FTIR, H-NMR, SEM, gelation time, rheology, adhesion, antioxidant activity, swelling ratio, weight loss, drug release, and cell viability. The addition of polydopamine was found to enhance the crosslinking density (0.859 × 109 mol.cm-3). Additionally, the results indicated improvements in properties such as reduced weight loss, enhanced antioxidant and adhesive qualities, and better mechanical properties (2240 kPa). However, the optimal concentration of polydopamine must be determined to achieve the best properties for a wound dressing. Excessive polydopamine can increase the space between polymer chains, leading to a reduction in crosslinking density and storage modulus. Nevertheless, it can also increase the swelling ratio, degradation rate, pore size, porosity, antioxidant activity, and dopamine release. Therefore, identifying the optimal concentration for a functional hydrogel is crucial. Notably, the hydrogel containing 0.5 mg.mL-1 polydopamine exhibited outstanding cell viability (108 % on the third day), swelling capacity (480 %), storage modulus (2240 kPa), gelation time (3 min), antioxidant activity (42.27 %), and skin adherence (11 kPa), making it an optimal choice for advanced wound management. According to the findings, it is emphasized that the application of this particular hydrogel expedites wound healing, as indicated by wound closure and histological studies. ABBREVIATIONS.

Fabrication of Luminescent Triple-Cross-Linked Gelatin/Alginate Hydrogels through Freezing-Drying-Swelling and Freezing-Thawing Processes

Lanthanide-containing luminescent hydrogels have shown potential for sensing and imaging applications. Nonetheless, integrating lanthanide ions or complexes into the polymer matrix often results in the poor stability and mechanical strength of the hydrogels. This work presents an innovative approach to fabricating luminescent hydrogels with three dynamic cross-links: imine bond, boronate ester bond, and metal-ligand coordination. Europium(III) (Eu3+) ions are incorporated into a dual-cross-linked matrix composed of phenylboronic acid-polyethylenimine-modified gelatin (PPG) and alginate dialdehyde (ADA) through a combined treatment involving freeze-drying-swelling (FDS) and freeze-thawing (FT) processes. The FDS process facilitates the formation of additional europium-carboxylate cross-links within the polymeric network to enhance its luminescence and stability, while the FT process strengthens the network physically. The impact of the FDS-FT cycle number on the microstructures and properties of PPG/ADA-Eu3+ hydrogels is thoroughly investigated, and their potential for monitoring bacterial growth and detecting copper(II) ions is also demonstrated.

3D Printing of Polysaccharide-Based Hydrogel Scaffolds for Tissue Engineering Applications: A Review

In tissue engineering, 3D printing represents a versatile technology employing inks to construct three-dimensional living structures, mimicking natural biological systems. This technology efficiently translates digital blueprints into highly reproducible 3D objects. Recent advances have expanded 3D printing applications, allowing for the fabrication of diverse anatomical components, including engineered functional tissues and organs. The development of printable inks, which incorporate macromolecules, enzymes, cells, and growth factors, is advancing with the aim of restoring damaged tissues and organs. Polysaccharides, recognized for their intrinsic resemblance to components of the extracellular matrix have garnered significant attention in the field of tissue engineering. This review explores diverse 3D printing techniques, outlining distinctive features that should characterize scaffolds used as ideal matrices in tissue engineering. A detailed investigation into the properties and roles of polysaccharides in tissue engineering is highlighted. The review also culminates in a profound exploration of 3D polysaccharide-based hydrogel applications, focusing on recent breakthroughs in regenerating different tissues such as skin, bone, cartilage, heart, nerve, vasculature, and skeletal muscle. It further addresses challenges and prospective directions in 3D printing hydrogels based on polysaccharides, paving the way for innovative research to fabricate functional tissues, enhancing patient care, and improving quality of life.

Modulating macrophage phenotype for accelerated wound healing with chlorogenic acid-loaded nanocomposite hydrogel

Wound healing involves distinct phases, including hemostasis, inflammation, proliferation, and remodeling, which is a complex and dynamic process. Conventional preparations often fail to meet multiple demands and provide prompt information about wound status. Here, a pH/ROS dual-responsive hydrogel (OHA-PP@Z-CA@EGF) was constructed based on oxidized hyaluronic acid (OHA), phenylboronic acid-grafted ε-polylysine (PP), chlorogenic acid (CA)-loaded ZIF-8 (Z-CA), and epidermal growth factor (EGF), which possesses intrinsic antibacterial, antioxidant, and angiogenic capacities. Due to the Schiff base and Phenylboronate ester bonds, the hydrogel exhibited excellent mechanical properties, strong adhesion, good biodegradability, high biocompatibility, stable rheological properties, and self-healing ability. Moreover, introducing Z-CA as an initiator and nanofiller led to the additional cross-linking of hydrogel through coordination bonds, which further improved the mechanical properties and antioxidant capabilities. Bleeding models of liver and tail amputations demonstrated rapid hemostatic properties of the hydrogel. Besides, the hydrogel regulated macrophage phenotypes via the NF-κB/JAK-STAT pathways, relieved oxidative stress, promoted cell migration and angiogenesis, and accelerated diabetic wound healing. The hydrogel also enabled real-time monitoring of the wound healing stages by colorimetric detection. This multifunctional hydrogel opens new avenues for the treatment and management of full-thickness diabetic wounds.

A guanosine/konjac glucomannan supramolecular hydrogel with antioxidant, antibacterial and immunoregulatory properties for cutaneous wound treatment

Developing naturally-derived wound dressing materials with intrinsic therapeutic effects is desirable for the clinical applications. Recently, guanosine-based supramolecular G-quadruplex (G4) hydrogel exhibited great potential in preparing biological materials due to its simple fabrication method and responsive gel networks. However, the weak mechanical properties and the consequent burst release of bioactive molecules restrict its clinical applications. Herein, we found that konjac glucomannan (KGM) with immunoregulatory effect did not affect the self-assembly of G-quadruplexes and thus effectively enhancing the mechanical properties of G4 hydrogel. Aloin, as a model drug, was in situ loaded into gel networks, finally obtaining the G4/Aloin-KGM hydrogel. This hydrogel exhibited porous morphology, swelling ability and hemostatic capability. Boronate bonds in G4 networks and aloin collectively endowed the hydrogel with excellent antioxidant performance. Meanwhile, aloin also provided outstanding in vitro and in vivo bactericidal ability. The wounds treated with this biocompatible hydrogel demonstrated faster regeneration of epithelial and dermal tissues, and the whole wound healing stages were accelerated by promoting collagen deposition, facilitating macrophage polarization towards M2 phenotype, down-regulating the expression level of IL-6, and up-regulating the expression level of IL-10, CD31 and α-SMA.

Doxorubicin-loaded Niosomes functionalized with gelatine and alginate as pH-responsive drug delivery system: A 3D printing approach

Despite many efforts, breast cancer remains one of the deadliest cancers and its treatment faces challenges related to cancer drug side effects and metastasis. Combining 3D printing and nanocarriers has created new opportunities in cancer treatment. In this work, 3D-printed gelatin-alginate nanocomposites containing doxorubicin-loaded niosomes (Nio-DOX@GT-AL) were recruited as an advanced potential pH-sensitive drug delivery system. Morphology, degradation, drug release, flow cytometry, cell cytotoxicity, cell migration, caspase activity, and gene expression of nanocomposites and controls (Nio-DOX and Free-DOX) were evaluated. Results show that the obtained niosome has a spherical shape and size of 60-80 nm. Sustained drug release and biodegradability were presented by Nio-DOX@GT-AL and Nio-DOX. Cytotoxicity analysis revealed that the engineered Nio-DOX@GT-AL scaffold had 90 % cytotoxicity against breast cancer cells (MCF-7), whereas exhibited <5 % cytotoxicity against the non-tumor breast cell line (MCF-10A), which was significantly more than the antitumor effect of the control samples. Scratch-assay as an indicator cell migration demonstrated a reduction of almost 60 % of the covered surface. Gene expression could provide an explanation for the antitumor effect of engineered nanocarriers, which significantly reduced metastasis-promoting genes (Bcl2, MMP-2, and MMP-9), and significantly enhanced the expression and activity of genes that promote apoptosis (CASP-3, CASP-8, and CASP-9). Also, considerable inhibition of metastasis-associated genes (Bax and p53) was observed. Moreover, flow-cytometry data demonstrated that Nio-DOX@GT-AL decreased necrosis and enhanced apoptosis drastically. The findings of this research can confirm that employing 3D-printing and niosomal formulation can be an effective strategy in designing novel nanocarriers for efficient drug delivery applications.