Oxidized Alginate Supplemented Gelatin Hydrogels for the In Situ Formation of Wound Dressing with High Antibacterial Activity

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.

In situ forming alginate/gelatin hydrogel scaffold through Schiff base reaction embedded with curcumin-loaded chitosan microspheres for bone tissue regeneration

In this study, we developed a biocompatible composite hydrogel that incorporates microspheres. This was achieved using a Schiff base reaction, which combines the amino and aldehyde groups present in gelatin (Gel) and oxidized alginate (OAlg). We suggest this hydrogel as a promising scaffold for bone tissue regeneration. To further boost its osteogenic capabilities and mechanical resilience, we synthesized curcumin (Cur)-loaded chitosan microspheres (CMs) and integrated them into the Gel-OAlg matrix. This formed a robust composite gel framework. We conducted comprehensive evaluations of various properties, including gelation time, morphology, compressive strength, rheological behavior, texture, swelling rate, in vitro degradation, and release patterns. A remarkable observation was that the inclusion of 30 mg/mL Cur-CMs significantly enhanced the hydrogel's mechanical and bioactive features. Over three weeks, the Gel-OAlg/Cur-CMs (30) composite showed a cumulative curcumin release of 35.57%. This was notably lower than that observed in standalone CMs and Gel-OAlg hydrogels. Additionally, the Gel-OAlg/Cur-CMs (30) hydrogel presented a reduced swelling rate and weight loss relative to hydrogels devoid of Cur-CMs. On the cellular front, the Gel-OAlg/Cur-CMs (30) hydrogel showcased superior biocompatibility. It also displayed increased calcium deposition, alkaline phosphatase (ALP) activity, and elevated osteogenic gene expression in human bone marrow mesenchymal stem cells (hBMSCs). These results solidify its potential as a scaffold for bone tissue regeneration.

Liposomal oxygen-generating hydrogel for enhancing cell survival under hypoxia condition

The inadequate oxygen supply to engineered tissues has been a persistent challenge in tissue engineering and regenerative medicine. To overcome this limitation, we developed a scaffold combined with an oxygen-releasing liposomal system comprising catalase-loaded liposomes (CAT@Lip) and H2O2-loaded liposomes (H2O2@Lip). This oxygenation system has shown high cytocompatibility when they were applied to human stromal cells. Under hypoxic conditions, the cell viability enclosed in the oxygen-releasing liposomal alginate hydrogel (94.62 ± 3.46 %) was significantly higher than that of cells enclosed in hydrogel without liposomes (47.18 ± 9.68 %). There was no significant difference in cell viability and apoptosis rate compared to normoxia conditions after three days, indicating the effectiveness of the oxygen-releasing approach in hypoxic conditions. In conclusion, our study demonstrates that the use of liposomal oxygen-releasing scaffolds can overcome the oxygen diffusion challenge in tissue implant fabrication, providing a simple solution for cellular oxygenation that could be a crucial element in tissue engineering.

An antibacterial and self-healing hydrogel from aldehyde-carrageenan for wound healing applications

This study aimed to develop and characterize a novel antibacterial, self-healing hydrogel made from aldehyde-carrageenan. Thus, carrageenan (CA) was first oxidized using different amounts of sodium periodate (NaIO₄), and the highest concentration of aldehyde was obtained when the ratio of NaIO₄ to CA was 1.5:1. Using dopamine (PDA) and zinc ions (Zn²⁺), various hydrogels were synthesized from oxidized carrageenan (O-CA). The effects of dopamine and zinc ions on the properties of O-CA hydrogel were examined. According to Fourier Transform Infrared Spectroscopy (FTIR) studies, the hydrogel's components are linked by Schiff bases, hydrogen bonds, and ion complexes. The rheological tests confirmed that hydrogels were elastic gels, not viscous sol, and were able to recover rapidly. Adding zinc to the hydrogel reduced weight loss (38 %) and provided extra antibacterial properties, particularly against E. coli. In addition, collagen secretion and cell attachment to Zn-containing hydrogels were significantly increased, and fibroblast viability reached 118 %. Overall, a hybrid O-CA/PDA/Zn hydrogel has excellent potential for wound healing applications.

Supramolecular Gels Incorporating Cordyline terminalis Leaf Extract as a Polyphenol Release Scaffold for Biomedical Applications

Cordyline terminalis leaf extract (aqCT) possesses abundant polyphenols and other bioactive compounds, which are encapsulated in gelatin-polyethylene glycol-tyramine (GPT)/alpha-cyclodextrin (α-CD) gels to form the additional functional materials for biomedical applications. In this study, the gel compositions are optimized, and the GPT/α-CD ratios equal to or less than one half for solidification are found. The gelation time varies from 40.7 min to 5.0 h depending on the increase in GPT/α-CD ratios and aqCT amount. The aqCT extract disturbs the hydrogen bonding and host-guest inclusion of GPT/α-CD gel networks, postponing the gelation. Scanning electron microscope observation shows that all gels with or without aqCT possess a microarchitecture and porosity. GPT/α-CD/aqCT gels could release polyphenols from 110 to 350 nmol/mL at the first hour and sustainably from 5.5 to 20.2 nmol/mL for the following hours, which is controlled by feeding the aqCT amount and gel properties. GPT/α-CD/aqCT gels achieved significant antioxidant activity through a 100% scavenging DPPH radical. In addition, all gels are non-cytotoxic with a cell viability more than 85%. Especially, the GPT3.75α-CD10.5aqCT gels with aqCT amount of 3.1-12.5 mg/mL immensely enhanced the cell proliferation of GPT3.75α-CD10.5 gel without extract. These results suggest that the inherent bioactivities of aqCT endowed the resulting GPT/α-CD/aqCT gels with effective antioxidant and high biocompatibility, and natural polyphenols sustainably release a unique platform for a drug delivery system or other biomedical applications.

Dual-functional alginate crosslinker: Independent control of crosslinking density and cell adhesive properties of hydrogels via separate conjugation pathways

Alginate is an abundant natural polysaccharide widely utilized in various biomedical applications. Alginate also possesses numerous hydroxyl and carboxylate functional groups that allow chemical modifications to introduce different functionalities. However, it is difficult to apply various chemical reactions to alginate due to limited solubility in organic solvents. Herein, functional moieties for radical polymerization and cell adhesion were separately conjugated to hydroxyl and carboxylate groups of alginate, respectively, in order to independently control the crosslinking density and cell adhesive properties of hydrogels. Sodium counterions of alginate are first substituted with tetrabutylammonium ions to facilitate the dissolution in an organic solvent, followed by in situ conjugations of (1) cell adhesion molecules (CAM) via carbodiimide-mediated amide formation and (2) methacrylate via ring-opening nucleophilic reaction. The resulting CAM-linked methacrylic alginate was able to not only crosslink different monomers to form hydrogels with varying mechanical properties, but also induce stable cell adhesion to the hydrogels.

Graft Architecture Guided Simultaneous Control of Degradation and Mechanical Properties of In Situ Forming and Fast Dissolving Polyaspartamide Hydrogels

Polyaspartamide, derived from polysuccinimide (PSI), has the advantage of conveniently presenting desired functional groups by ring-opening addition of amine-based nucleophiles to the succinimidyl ring moieties of PSI. Using diamines with varying lengths of poly(ethylene glycol) linker, polyaspartamide presenting amine groups with controllable grafting density and length, namely, poly(2-hydroxyethyl aspartamide)-g-amino-poly(ethylene glycol) (PHEA-PEGAm) could be synthesized. This PHEA-PEGAm was then used to develop in situ forming hydrogels by Schiff base formation with aldehyde-containing alginate (Alg-ALD). By modulating the graft architecture (i.e., grafting length and density), the mechanical properties of the resulting Alg-PHEA hydrogels could be controlled in a broad range. Remarkably, the hydrogels were shown to undergo facile degradation and complete dissolution in physiological conditions, regardless of hydrogel mechanics, by the expedited hydrolysis through the action of remaining amine groups, which was also heavily influenced by the graft architecture. Moreover, the rate of degradation could be further controlled by additional ionic cross-linking of alginate. The potential application as an injectable drug delivery system was demonstrated by measuring drug release kinetics and monitoring degradation ex vivo.

Intranasal delivery of icariin via a nanogel-thermoresponsive hydrogel compound system to improve its antidepressant-like activity

Although icariin has been reported to have antidepressant-like effects in different animal models, its poor oral bioavailability and low efficiency of delivery to the brain limit its application. In this study, icariin nanogels were prepared by reverse microemulsion methods to improve its poor water solubility. Then, we developed an icariin nanogel loaded self-assembled thermosensitive hydrogel system (icariin-NGSTH) to deliver icariin via a noninvasive, direct nose-to-brain delivery route for the treatment of depression. The in vivo distribution was investigated by fluorescence imaging with rhodamine B-labeled nanogels. The antidepressant efficacy of icariin-NGSTH was evaluated in behavioral despair tests and the chronic unpredictable mild stress (CUMS) model. The results showed that icariin-NGSTH had a zero-order kinetics release in the first 10 h. Icariin-NGSTH led to rapid brain distribution within 30 min. Icariin-NGSTH significantly reduced the duration of immobility in the tail suspension test (TST) and forced swim test (FST). Compared with oral administration, intranasally administered icariin-NGSTH had a fast-acting antidepressant effect in the TST and FST. Moreover, icariin-NGSTH increased body weight and sucrose preference, reversed abnormal plasma levels of testosterone, interleukin-6 (IL-6) and prostaglandin E₂ (PGE₂), and repaired neuronal damage in the hippocampi of CUMS rats. These results indicated that icariin-NGSTH at a low dose produced a significant antidepressant effect. As a complex drug delivery system, intranasally administered icariin-NGSTH is a rapid and effective treatment for depression, increasing the antidepressant-like activity of icariin.

Hydrogel-Based Active Substance Release Systems for Cosmetology and Dermatology Application: A Review

Hydrogels are playing an increasingly important role in medicine and pharmacy. Due to their favorable physicochemical properties, biocompatibility, and designed interaction with living surroundings, they seem to be one of the most promising groups of biomaterials. Hydrogel formulations from natural, semi, or synthetic polymeric materials have gained great attention in recent years for treating various dermatology maladies and for cosmetology procedures. The purpose of this review is to present a brief review on the basic concept of hydrogels, synthesis methods, relevant mechanisms, and applications in dermatology or cosmetology. This review discusses transdermal therapies and the recent advances that have occurred in the field.

In situ forming and reactive oxygen species-scavenging gelatin hydrogels for enhancing wound healing efficacy

The overexpression of reactive oxygen species (ROS) contributes to the pathogenesis of numerous diseases such as atherosclerosis, myocardial infarction, cancer, and chronic inflammation. Therefore, the development of materials that can locally control the adverse effects resulting from excessive ROS generation is of great significance. In this study, the antioxidant gallic acid-conjugated gelatin (GGA) was introduced into gelatin-hydroxyphenyl propionic (GH) hydrogels to create an injectable hydrogel with enhanced free radical scavenging properties compared to pure GH hydrogels. The modified hydrogels were rapidly formed by an HRP-catalyzed cross-linking reaction with high mechanical strength and biodegradability. The resulting GH/GGA hydrogels effectively scavenged the hydroxyl radicals and DPPH radicals, and the scavenging capacity could be modulated by varying GGA concentrations. Moreover, in an in vitro H₂O₂-induced ROS microenvironment, GH/GGA hydrogels significantly suppressed the oxidative damage of human dermal fibroblast (hDFBs) and preserved their viability by reducing intracellular ROS production. More importantly, the ROS scavenging hydrogel efficiently accelerated the wound healing process with unexpected regenerative healing characteristics, shown by hair follicle formation; promoted neovascularization; and highly ordered the alignment of collagen fiber in a full-thickness skin defect model. Therefore, we expect that injectable GH/GGA hydrogels can serve as promising biomaterials for tissue regeneration applications, including wound treatment and other tissue repair related to ROS overexpression. STATEMENT OF SIGNIFICANCE: Recently, many researchers have endeavored to develop injectable hydrogel matrices that can modulate the ROS level to normal physiological processes for the treatment of various diseases. Here, we designed an injectable gelatin hydrogel in which gallic acid, an antioxidant compound, was conjugated onto a gelatin polymer backbone. The hydrogels showed tunable properties and could scavenge the free radicals in a controllable manner. Because of the ROS scavenging properties, the hydrogels protected the cells from the oxidative damage of ROS microenvironment and effectively accelerated the wound healing process with high quality of healed skin. We believe that this injectable ROS scavenging hydrogel has great potential for wound treatment and tissue regeneration, where oxidative damage by ROS contributes to the pathogenesis.