Amazing Hydrogel Wound Dressing!

1：Research Background

The skin is the largest organ of the human body and can be divided into three layers: the epidermis, the dermis, and the subcutaneous fat layer. The barrier function provided by it is crucial to retain moisture, provide mechanical strength, and prevent the invasion of pathogenic microorganisms. When the skin is damaged by trauma, disease or surgery, it is very important to repair the skin quickly.

human skin structure

Compared with all other tissues in the human body, human skin has a powerful ability to self-regenerate . The self-repair of the skin is divided into four stages-coagulation stage, inflammation stage, proliferation stage, and remodeling stage.

wound healing process

Scars are generally formed during the wound healing process. When the subcutaneous tissue of the skin is damaged, the body deposits collagen fibers to cover the damaged area, which can produce obvious scars. Therefore, dressings that can induce scarless healing are needed.

An idealwound dressingshould have the following characteristics:

①Keep the wound moist and prevent dry scabs on the wound surface from hindering the delivery of nutrients, the immune defense of the wound surface, and the ability of cells to migrate on the wound surface, thereby promoting tissue regeneration.

②Good biocompatibility, non-allergic, non-toxic, so as not to cause wound infection.

③It can be removed painlessly to avoid secondary damage.

④ It has the characteristics of antibacterial, heat insulation and softness.

⑤The price is reasonable.

2：Advantages and pain points of commonly used wound dressings

Wound dressings are aids used on wounds to promote healing and prevent infection and further damage. Can be divided into dry dressing and wet dressing.

Common dry dressings include fibrous dressings (such as gauze), etc., but the wound will continue to contact with air and scab, covering the wound and reducing the rate of epithelial formation; injury.

Wet dressings such as hydrocolloids, foam dressings, hydrogel dressings, etc. will not form scabs and will increase the rate of healing as the wet dressing provides low oxygen tension which aids wound healing. These dressings not only keep the cells alive, allowing them to release growth factors, but also maintain contact between the cells and the healing tissue, regulating or stimulating their proliferation. These dressings reduce pain during rest, walking, and dressing changes. At the same time, the moist environment can quickly and efficiently deliver any added antimicrobial agents, thereby preventing wounds from becoming infected in a moist environment.

Hydrocolloid dressings are composed of absorbent ingredients (such as carboxymethylcellulose, pectin, and gelatin) and a rubber base. They are inexpensive to use and can effectively avoid secondary damage, but they cause the risk of contact dermatitis and can also be used in wounds. The underside of the dressing produces a foul-smelling yellow gel that may lead clinicians or patients to mistake the wound for infection.

Foam dressings are polyurethane- or silicone-based synthetic, moisture-retaining, usually thicker dressings that add volume and cushion to the wound bed. May produce malodorous gels similar to those observed with hydrocolloids.

Hydrogel dressings have a three-dimensional network composed of hydrophilic substances , are insoluble in water, and can absorb water up to 1000 times their own weight; at the same time, they are usually transparent and can monitor wound healing without removing the dressing; The gel will not adhere to the wound and the healthy skin around it, and will not cause secondary damage to the wound when it is removed; more importantly, the natural hydrogel has good biodegradability, and at the same time it is similar to the extracellular matrix. The characteristics make it have good biocompatibility , relatively safe and environmentally friendly.

In summary, hydrogel dressing is a promising wound dressing.

3：Types of hydrogel dressings

Chitosan-based hydrogel dressing

Chitin is the most abundant natural amino polysaccharide (poly-N-acetyl-glucosamine), which is a major component of invertebrate, crustacean and insect exoskeletons and fungal cell walls.

Chitosan (CS) is the deacetylation product of chitin, poly-N-acetyl-glucosaminoglycan, obtained by treating shrimp and other crustacean shells with sodium hydroxide. Composed of randomly distributed β-(1→4)-d-glucosamine and N-acetyl-d-glucosamine.

A biofunctional modification strategy was employed to enhance the antibacterial, antioxidant, and anti-inflammatory properties of chitosan hydrogels, thereby facilitating the complete closure of bacterially infected wounds.

Chitosan

Introduced multifunctional cinnamaldehyde-tannic acid-zinc acetate nanospheres (CA-TA-ZA NSs) incorporating hydrophilic and hydrophobic properties into chitosan (CS)-based hydrogel 3D networks.

Preparation of Multifunctional Cinnamaldehyde-Tannic Acid-Zinc Acetate Nanospheres

Cross-linking mechanism of chitosan-based hydrogels

(Strong ionic crosslinking, ammoniacal condensation, electrostatic interaction, hydrogen bonding)

The CS-based hydrogel exhibits good antibacterial, anti-oxidative, and anti-inflammatory capabilities, and can achieve rapid gelation in completely covering irregular wounds, thereby cleaning the wound, inducing regeneration of injured tissue, and promoting wound healing.

Gelatin-based hydrogel dressings

Gelatin (HA) is one of the common animal proteins, which contains many amino acid residues, including glycine, proline, hydroxyproline and tyrosine, has good biocompatibility and biodegradability, and has a large number of cellular Recognition site, strong ability to adsorb cells, and can promote cell proliferation.

Zhang et al. introduced a strong reducing catechol group into gelatin, grafted dopamine hydrochloride (DA) onto the gelatin main chain, increased its biomineralization ability, and used it as a biological template to reduce silver ions in situ to generate stable silver Nanoparticles (Ag NPs) to make Gel-DA@Ag hydrogel.

Preparation principle and antibacterial mechanism of gelatin-based hydrogel

On the one hand, the hydrogel can sterilize bacteria through the unique antibacterial properties of Ag nanoparticles, and on the other hand, the local temperature rise caused by the photothermal effect of the hydrogel can also remove bacteria attached to the wound.

Hyaluronic acid-based hydrogel dressing

Hyaluronic acid (HA) is a linear polysaccharide formed from repeating 1, 4- and 1,3-linked glucuronic acid and N-acetylglucosamine units and is ubiquitous in the ECM of all vertebrate tissues . Through its interactions with proteoglycans and connexins, HA organizes and maintains the structural integrity of the extracellular and pericellular matrix. As a signaling molecule, HA interacts with various cell surface receptors and HA-binding proteins to enable normal cellular physiological activities.

4：Summarize

In the research and development of wound dressings, hydrogel materials have received more and more attention. Natural polymer hydrogels with similar structures to living organisms are currently the most ideal wound dressings. However, natural polymer materials have the disadvantages of poor mechanical properties and insufficient functionalization. In response to these problems, researchers have conducted a large number of researches on the modification of natural polymer hydrogels, including the self-modification of natural polymer materials. , Composite modification between natural polymer materials, and composite modification between natural polymer materials and synthetic materials have made great progress, but to meet the requirements of ideal wound dressings, a lot of research is still needed Experiment and explore.