Hydrogel-based Chlorella vulgaris extracts: a new topical formulation for wound healing treatment

Chlorella vulgaris is a microalga which contains a variety of bioactive compounds. Chlorella has been used in different fields for several years and proved attractive to the pharmaceutical and cosmetic industry. The present study aimed to evaluate the wound-healing activity of a hydrogel-based C. vulgaris extract in in vivo assay. A hydrogel formulation containing different concentrations of extracts of C. vulgaris grown under autotrophic (AE) or mixotrophic (ME) condition was developed and applied for 12 days on excisional wounds in mice. Macroscopic analyses and histomorphometric studies were performed to investigate tissue repair. Extracts were evaluated for protein concentration, phytochemical profile, hemagglutinating activity, antioxidant activity using DPPH assay, and antibacterial activity. The wound-healing assay suggested that animals treated with hydrogel containing 25% of ME exhibited a higher presence of collagen deposition, a decrease of fibroblast and inflammatory cells, strong evidence of skin appendages, and evidence of basal laminae. Results showed that ME has 1.174 mg mL−1 of total proteins and hemagglutinating activity ≥ to 248 against rabbit erythrocytes and ≥ to 224 against human type B blood. The phytochemical profile of the extract demonstrated the presence of steroids, triterpenes, saponins, and sugars. In addition, ME had the highest values of antioxidant activity (54.64%) and antibacterial activity against Klebsiella pneumoniae, Enterococcus faecalis, and Escherichia coli. This first report of a hydrogel formulation containing microalgae extracts for wound healing showed that C. vulgaris cell extracts from mixotrophic cultivation have pro-healing and anti-inflammatory properties, which accelerated the wound healing process.