Novel flexible hydrogel wound dressing.
Novel flexible hydrogel wound dressing.

Cuts and abrasions to the skin are one of the most common injuries, but wound dressings that are flexible and comfortable enough for joints like knees, ankles, and wrists are lacking. A new self-healing, injectable, multifunctional wound dressing based on a micelle-hydrogel composite, developed by researchers from Xi’an Jiaotong University in China and the University of Michigan, could be the answer [Qu et al., Biomaterials 183 (2018) 185-199].

“Designing wound dressing materials with outstanding therapeutic, self-healing, adhesive, and mechanical properties has great practical significance in healthcare, especially for skin wound healing on joints,” says Baolin Guo of Xi’an Jiaotong University.

The novel composite hydrogel is prepared by mixing solutions of quaternized chitosan (QCS) and benzaldehyde-terminated poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO99-b-PPO65-b-PEO99, Pluronic® F127 (PF127)) in different ratios of –CHO to –NH2. The resulting injectable wound dressing material is inherently antibacterial and possesses a range of useful properties including tunable gelation time (on the order of a few seconds), pH-dependent biodegradation, biocompatibility, and mechanical properties similar to human skin. Moreover, the researchers demonstrate that the hydrogel mops up the free radicals generated during natural healing and can also be loaded with active agents – such as the antioxidant curcumin in this case – to enhance the process.

The researchers tested the hydrogel wound dressing in full-thickness skin defects in mice and found improved healing rate, higher density of fibroblasts – which produce collagen and other connective fibrous tissues, and ultimately thicker tissue and greater deposition of collagen. The hydrogel showed blood-clotting properties as well.

“Compared with existing wound-healing dressings, this kind of multifunctional hydrogel dressing could promote each stage of the wound healing process in terms of the hemostasis, inflammation, proliferation, and remodeling,” explains Guo.

Other kinds of wound dressing typically only support one or two stages of wound healing. Meanwhile, in practical terms, the hydrogel adheres well to skin and matches its physical properties in terms of flexibility and elasticity. These attributes could be particularly useful for wound dressings in awkward places such as joints, where repeated movement can loosen dressings or be uncomfortably restrictive for patients.

“The most obvious advantage of this kind of hydrogel is its multifunctional mechanism for settling the problem of joint skin damage,” says Guo. “The hydrogel dressings show suitable stretchable and compressive properties, comparable to the modulus of human skin, good adhesiveness, and self-healing capabilities for withstanding deformation.”

The adhesiveness and robustness of the hydrogels will need to be improved further before actual applications are possible, admits Guo, but this should be feasible using strategies such as mussel-inspired wet-adhesion. The researchers are now exploring different options to optimize the hydrogel dressing.