Neuropeptide Substance P Released from a Nonswellable Laponite-Based Hydrogel Enhances Wound Healing in a Tissue-Engineered Skin In Vitro

Chronic wounds associated with diabetes remain a worldwide clinical challenge. Substance P (SP), which is an 11-amino acid neuropeptide secreted in the skin mainly by sensory neurons, has been reported to promote diabetic wound healing. However, like many bioactive peptides, the low stability of SP in the protease-rich wound environment limits its therapeutic topical application. To provide protection to SP and enable its sustained release in the wound, we have prepared an injectable Laponite nanodiscs-based hydrogel loaded with SP and evaluated its wound healing ability in a human tissue-engineered skin model. This hydrogel is nonswellable, self-standing, biodegradable and biocompatible, and the simple fabrication process with mild conditions have enabled the encapsulation of controlled concentrations of SP. Rheological experiments further showed the self-healing and shear-thinning behavior of this system. Histological analysis showed that the application of hydrogel did not alter the aspect or the differentiation of nearby epidermis, confirming its biocompatibility. Remarkably, one-time application experiments demonstrated that the hydrogel HSP2 containing SP at 10–5 M induced 98% wound closure within 16 days, whereas the control sample did not achieve full reepithelialization. This result indicated that SP was successfully released from the hydrogel and was available for keratinocytes to stimulate the reepithelialization process. Thus, the obtained data suggested that our SP-loaded hydrogel promoted wound healing, making it a potential formulation to be used as chronic wound dressing.