A Spray‐Filming Self‐Healing Hydrogel Fabricated from Modified Sodium Alginate and Gelatin as a Bacterial Barrier

A Photo-induced Cross-Linking Enhanced A and B Combined Multi-Functional Spray Hydrogel Instantly Protects and Promotes of Irregular Dynamic Wound Healing

Wounds in harsh environments can face long-term inflammation and persistent infection, which can slow healing. Wound spray is a product that can be rapidly applied to large and irregularly dynamic wounds, and can quickly form a protective film in situ to inhibit external environmental infection. In this study, a biodegradable A and B combined multi-functional spray hydrogel is developed with methacrylate-modified chitosan (CSMA1st) and ferulic acid (FA) as type A raw materials and oxidized Bletilla striata polysaccharide (OBSP) as type B raw materials. The precursor CSMA1st-FA/OBSP (CSOB-FA1st) hydrogel is formed by the self-cross-linking of dynamic Schiff base bonds, the CSMA-FA/OBSP (CSOB-FA) hydrogel is formed quickly after UV-vis light, so that the hydrogel fits with the wound. Rapid spraying and curing provide sufficient flexibility and rapidity for wounds and the hydrogel has good injectability, adhesive, and mechanical strength. In rats and miniature pigs, the A and B combined spray hydrogel can shrink wounds and promote healing of infected wounds, and promote the enrichment of fibrocyte populations. Therefore, the multifunctional spray hydrogel combined with A and B can protect irregular dynamic wounds, prevent wound infection and secondary injury, and be used for safe and effective wound treatment, which has a good prospect for development.

A dual network cross-linked hydrogel with multifunctional Bletilla striata polysaccharide/gelatin/tea polyphenol for wound healing promotion

Wound healing is a dynamic and complex biological process, and traditional biological excipients cannot meet the needs of the wound healing process, and there is an urgent need for a biological dressing with multifunctionality and the ability to participate in all stages of wound healing. This study developed tea polyphenol (TP) incorporated multifunctional hydrogel based on oxidized Bletilla striata polysaccharide (OBSP) and adipic acid dihydrazide modified gelatin (Gel-ADH) with antimicrobial, antioxidant hemostatic, and anti-inflammatory properties to promote wound healing. The composite OBSP, Gel-ADH, TP (OBGTP) hydrogels prepared by double crosslinking between OBSP, TP and Gel-ADH via Schiff base bonding and hydrogen bonding had good rheological and swelling properties. The introduction of TP provided the composite hydrogel with excellent antioxidant antibacterial activities against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coil). In the rat liver hemorrhage model and skin injury model, the OBGTP composite hydrogel had significant (p < 0.001) hemostatic ability, and had the ability to accelerate collagen deposition, reduce the expression of inflammatory factors, and promote rapid wound healing. In addition, OBGTP hydrogels had adhesive properties and good biocompatibility. In conclusion, OBGTP multifunctional composite hydrogels have great potential for wound healing applications.

An Injectable, Adhesive, and Self-Healing Hydrogel with Inherently Antibacterial Property for Wound Dressing

Antibacterial hydrogel has emerged as an excellent candidate for wound dressing with the ability to eliminate infection and promote wound healing. Herein, a dynamic hydrogel is developed by Schiff base reaction of mixed charged polypeptides and oxidized dextran (ODex). Specifically, biodegradable polypeptides of 1-(propylthio)acetic acid-3-butylimidazole-modified poly(L-lysine) (PLL-PBIM) and adipate dihydrazide-modified poly(L-glutamic acid) (PLG-ADH) are achieved with tunable substitution and charge. By mixing with ODex, charged polypeptides of PLL-PBIM and PLG-ADH led to an injectable and self-healing hydrogel in seconds. The injectable and self-healing performances of the hydrogels are ascribed to the reversible imine and hydrazone bonds formed between polypeptides and ODex. The positively charged hydrogels exhibited over 95% antibacterial activity against E. coli and S. aureus. An optimized balancing of PLG-ADH and PLL-PBIM significantly reduced the hemolysis rate and cytotoxicity of hydrogels. Therefore, the dynamic hydrogel with excellent biocompatibility and inherently antibacterial ability can have potential application for wound dressing.

Advancements in gelatin-based hydrogel systems for biomedical applications: A state-of-the-art review

A gelatin-based hydrogel system is a stimulus-responsive, biocompatible, and biodegradable polymeric system with solid-like rheology that entangles moisture in its porous network that gradually protrudes to assemble a hierarchical crosslinked arrangement. The hydrolysis of collagen directs gelatin construction, which retains arginyl glycyl aspartic acid and matrix metalloproteinase-sensitive degeneration sites, further confining access to chemicals entangled within the gel (e.g., cell encapsulation), modulating the release of encapsulated payloads and providing mechanical signals to the adjoining cells. The utilization of various types of functional tunable biopolymers as scaffold materials in hydrogels has become highly attractive due to their higher porosity and mechanical ability; thus, higher loading of proteins, peptides, therapeutic molecules, etc., can be further modulated. Furthermore, a stimulus-mediated gelatin-based hydrogel with an impaired concentration of gellan demonstrated great shear thinning and self-recovering characteristics in biomedical and tissue engineering applications. Therefore, this contemporary review presents a concise version of the gelatin-based hydrogel as a conceivable biomaterial for various biomedical applications. In addition, the article has recapped the multiple sources of gelatin and their structural characteristics concerning stimulating hydrogel development and delivery approaches of therapeutic molecules (e.g., proteins, peptides, genes, drugs, etc.), existing challenges, and overcoming designs, particularly from drug delivery perspectives.

Recent update on alginate based promising transdermal drug delivery systems

Alongside oral delivery of therapeutics, transdermal delivery systems have gained increased patient acceptability over past few decades. With increasing popularity, novel techniques were employed for transdermal drug targeting which involves microneedle patches, transdermal films and hydrogel based formulations. Hydrogel forming ability along with other rheological behaviour makes natural polysaccharides an attractive option for transdermal use. Being a marine originated anionic polysaccharide, alginates are widely used in pharmaceutical, cosmetics and food industries. Alginate possesses excellent biodegradability, biocompatibility and mucoadhesive properties. Owing to many favourable properties required for transdermal drug delivery systems (TDDS), the application of alginates are increasing in recent times. This review summarizes the source and properties of alginate along with several transdermal delivery techniques including the application of alginate for respective transdermal systems.

Injectable multifunctional carboxymethyl chitosan/hyaluronic acid hydrogel for drug delivery systems

Injectable hydrogels with notable mechanical properties and self-healing ability are promising carriers for use as a drug delivery system. Here, adipic acid dihydrazide (ADH) and calcium ions (Ca2+) were introduced into quaternary ammonium carboxymethyl chitosan and aldehyde-modified hyaluronic acid hydrogels (QCS + OHA). The hydrogels were synthesized through the interaction of the Schiff bases (imine bonds, acylhydrazone bonds) and coordination bonds via a facile one-step approach. The gelation time (∼54 s) ensured excellent injectability. The QCS + OHA + ADH + Ca2+ hydrogel had notable mechanical properties (compressive stress up to 896.30 KPa), good self-healing ability (up to 94 %), good pH responsiveness, and excellent antibacterial properties. In addition, the QCS + OHA + ADH + Ca2+ hydrogel had a high drug loading capacity (121.3 mg/g) and sustained drug release behaviour (≥120 h). The results of cytotoxicity tests showed a high cell proliferation rate (up to 98 %) and good cytocompatibility. In summary, this work presents an injectable and self-healing pH-responsive hydrogel that can be used as a carrier for drug delivery systems.

Sustained release of alginate hydrogel containing antimicrobial peptide Chol-37(F34-R) in vitro and its effect on wound healing in murine model of Pseudomonas aeruginosa infection

BACKGROUND

Antibiotic resistance is a significant public health concern around the globe. Antimicrobial peptides exhibit broad-spectrum and efficient antibacterial activity with an added advantage of low drug resistance. The higher water content and 3D network structure of the hydrogels are beneficial for maintaining antimicrobial peptide activity and help to prevent degradation. The antimicrobial peptide released from hydrogels also hasten the local wound healing by promoting epithelial tissue regeneration and granulation tissue formation.

OBJECTIVE

This study aimed at developing sodium alginate based hydrogel loaded with a novel antimicrobial peptide Chol-37(F34-R) and to investigate the characteristics in vitro and in vivo as an alternative antibacterial wound dressing to treat infectious wounds.

METHODS

Hydrogels were developed and optimized by varying the concentrations of crosslinkers and subjected to various characterization tests like cross-sectional morphology, swelling index, percent water contents, water retention ratio, drug release and antibacterial activity in vitro, and Pseudomonas aeruginosa infected wound mice model in vivo.

RESULTS

The results indicated that the hydrogel C proved superior in terms of cross-sectional morphology having uniformly sized interconnected pores, a good swelling index, with the capacity to retain a higher quantity of water. Furthermore, the optimized hydrogel has been found to exert a significant antimicrobial activity against bacteria and was also found to prevent bacterial infiltration into the wound site due to forming an impermeable barrier between the wound bed and external environment. The optimized hydrogel was found to significantly hasten skin regeneration in animal models when compared to other treatments in addition to strong inhibitory effect on the release of pro-inflammatory cytokines (interleukin-1β and tumor necrosis factor-α).

CONCLUSIONS

Our results suggest that sodium alginate -based hydrogels loaded with Chol-37(F34-R) hold the potential to be used as an alternative to conventional antibiotics in treating infectious skin wounds.

One-Pot and Green Preparation of Phyllanthus emblica Extract/Silver Nanoparticles/Polyvinylpyrrolidone Spray-On Dressing

A spray-on wound dressing has many benefits, including easy and quick administration to broad and uneven wounds, better interface with the wound site, adhesion without additional dressing, and multiple applications in a portable package. By limiting direct contact with the wound site, such a design can prevent wound damage during treatment. This study revealed a simple, one-pot synthesis of spray-on wound dressing relying on polyvinylpyrrolidone solution incorporating silver nanoparticles as a broad-spectrum antibacterial agent and wound-healing antioxidant Phyllanthus emblica extract. Silver nanoparticles were synthesized in situ using Phyllanthus emblica extract as a biogenic reducing agent. Polyvinylpyrrolidone was employed as a film-forming agent to create an adhesive hydrogel-based dressing matrix to provide moisture and establish a shielding barrier for the wound bed as well as to regulate the release of fruit extract. In vitro tests revealed that the produced dressing film had a controlled release of the fruit extract, high antioxidant activity, and a good antibacterial action against S. aureus, P. aeruginosa, E. coli, and MRSA. Additionally, a biocompatibility study has shown that both human fibroblasts and keratinocytes are unaffected by the dressing film. Based on established findings, the current spray-on solution might be a potential option for antibacterial wound dressing.

Application of Alginate-Based Hydrogels in Hemostasis

Hemorrhage, as a common trauma injury and clinical postoperative complication, may cause serious damage to the body, especially for patients with huge blood loss and coagulation dysfunction. Timely and effective hemostasis and avoidance of bleeding are of great significance for reducing body damage and improving the survival rate and quality of life of patients. Alginate is considered to be an excellent hemostatic polymer-based biomaterial due to its excellent biocompatibility, biodegradability, non-toxicity, non-immunogenicity, easy gelation and easy availability. In recent years, alginate hydrogels have been more and more widely used in the medical field, and a series of hemostatic related products have been developed such as medical dressings, hemostatic needles, transcatheter interventional embolization preparations, microneedles, injectable hydrogels, and hemostatic powders. The development and application prospects are extremely broad. This manuscript reviews the structure, properties and history of alginate, as well as the research progress of alginate hydrogels in clinical applications related to hemostasis. This review also discusses the current limitations and possible future development prospects of alginate hydrogels in hemostatic applications.

Biomimetic Hydrogels to Promote Wound Healing

Wound healing is a common physiological process which consists of a sequence of molecular and cellular events that occur following the onset of a tissue lesion in order to reconstitute barrier between body and external environment. The inherent properties of hydrogels allow the damaged tissue to heal by supporting a hydrated environment which has long been explored in wound management to aid in autolytic debridement. However, chronic non-healing wounds require added therapeutic features that can be achieved by incorporation of biomolecules and supporting cells to promote faster and better healing outcomes. In recent decades, numerous hydrogels have been developed and modified to match the time scale for distinct stages of wound healing. This review will discuss the effects of various types of hydrogels on wound pathophysiology, as well as the ideal characteristics of hydrogels for wound healing, crosslinking mechanism, fabrication techniques and design considerations of hydrogel engineering. Finally, several challenges related to adopting hydrogels to promote wound healing and future perspectives are discussed.

Porous gelatin microspheres for controlled drug delivery with high hemostatic efficacy

Effective hemostasis and antibacterial efficacy for extensive trauma in a warzone and civilian accidents are important for reducing mortalities and serious complications. Gelatin has been widely used as a hemostatic agent and has the potential for use in drug delivery systems. To enhance its hemostatic efficiency and create conducive conditions for sustained drug release, we developed Vancomycin-impregnated porous gelatin microspheres (Van-MS) by introducing the porous structure into gelatin. Results showed that Van-MS can be successfully developed via the ice crystal pore-making method combined with hydration maintaining its stability. We also explored the use of biodegradable porous materials for treatment of infections and bleeding in soft tissue, and analyzed Van-MS via scanning electron microscopy (SEM), scanning electron microscopy and energy dispersive X-ray spectrometry (SEM-EDS), Fourier Transform infrared spectroscopy (FTIR) and High-Performance Liquid Chromatography (HPLC). Results from Van-MS showed high hemostatic both efficacies in vivo and in vitro. Moreover, muscle lesions treated by Van-MS showed formation of fibrous connective tissue and were nearly sealed after 10 days in a rabbit traumatic infection model. This antibacterial performance was attributed to absorption of exudates and sustained drug release. Hemostatic effects were due to: (1) particles water swelling form a physical barrier that led to physical hemostasis; (2) activation of the endogenous coagulation pathway which resulted in physiological hemostasis; (3) aggregation of platelets and erythrocytes after absorbing water; and (4) stronger hemostatic properties owing to their porous structure with high specific surface area.

A reduced polydopamine nanoparticle-coupled sprayable PEG hydrogel adhesive with anti-infection activity for rapid wound sealing

There is a growing demand to develop sprayable hydrogel adhesives with rapid-forming and antibacterial abilities to instantly seal open wounds and combat pathogen infection. Herein, we propose to design a polydopamine nanoparticle (PDA NP) coupled PEG hydrogel that can quickly solidify via an amidation reaction after spraying as well as tightly binding PDA NPs to deliver reactive oxygen species (ROS) and induce a photothermal effect for bactericidal activity, and provide a hydrophilic surface for antifouling activity. The molecular structure of the 4-arm-PEG-NHS precursor was regulated to increase its reactivity with 4-arm-PEG-NH2, which thus shortened the gelation time of the PEG adhesive to 1 s to allow a fast solidification after being sprayed. The PEG-NHS precursor also provided covalent binding with tissue and PDA NPs. The reduced PDA NPs have redox activity to convey electrons to oxygen to generate ROS (H2O2), thus endowing the hydrogel with ROS dependent antibacterial ability. Moreover, NIR irradiation can accelerate the ROS release because of the photothermal effect of PDA NPs. In vitro tests demonstrated that H2O2 and the NIR-photothermal effect synergistically induced a fast bacterial killing, and an in vivo anti-infection test also proved the effectiveness of PEG-PDA. The sprayable PEG-PDA hydrogel adhesive, with rapid-forming performance and a dual bactericidal mechanism, may be promising for sealing large-scale and acute wound sites or invisible bleeding sites, and protect them from pathogen infection.

Stretchable, self-healable integrated conductor based on mechanical reinforced graphene/polyurethane composites

Stretchable conductors are susceptible to wear through repeated deformation over time. Stretchable conductors with self-healing properties can increase longevity and reduce safety hazards. However, most current self-healing conductors can only repair either the conductive layer or the insulating layer. Meantime, high mechanical robustness and self-healing efficiency are exclusive especially at ambient conditions. Realizing a stretchable conductor with integral self-healing and ultra-high mechanical strength is challenging, because this requires good interfacial compatibility and adaptability of the conductive and insulating layers. We adapt a biphasic dynamic network strategy to add toughness to self-healing materials. The DOU (dimethylglyoxime-urethane polyurethane) dynamic bonds and hydrogen bonds in the soft phase enable high self-healing efficiency, while the graphene as a hard phase supports the material's superior mechanical properties. We have prepared an overall self-healing stretchable conductor through the soft phase as a self-encapsulating insulating layer. This all-solid (Tg = -49.5 °C) graphene/dimethylglyoxime-urethane polyurethane (Gr/DOU-PU) composites characteristic of both high mechanical strength (~6 MPa, ~1000%, ~48 MJ m^-3), self-healing conductivity (~90%, 10 min, 25 °C) and conductivity (R□=47.8 Ω □^-1, d = 0.4 mm). The conductor has excellent stability for flexible electronics and for building stress sensors.

Sustainable dialdehyde polysaccharides as versatile building blocks for fabricating functional materials: An overview

Dialdehyde polysaccharide (DAP), containing multiple aldehyde groups, can react with materials having amino groups via Schiff base crosslinking. Besides, it can also react with materials having carbonyl/hydroxyl groups via aldol reactions. Based on these intriguing properties, DAPs can be employed as versatile building blocks to fabricate functional materials used in biomedical field, wastewater treatment, leather manufacture, and electrochemistry field. This review aims to provide an overview of the recent advances in fabricating biomaterials, adsorbents, leather tanning agents, and electrochemical materials based on DAPs. The basic fabricating strategy and principle of these materials and their performances are overall summarized, along with a discussion of associated scalability challenges, technological strategies to overcome them, and the prospect for commercial translations of this versatile material. Blending the versatility of DAP with material science and technological advances can provide a powerful tool to develop more DAP-based functional materials in a scalable way.