Human placental mesenchymal stem cell gel(Beijing Health & Biotech)

1) To clarify the tolerance and safety of human placental mesenchymal stem cell gel in the treatment of patients with diabetic foot ulcers and determine the safe range of clinical medication. 2) To preliminarily observe the effectiveness of human placental mesenchymal stem cell gel in the treatment of diabetic foot ulcers and provide a basis for the design of subsequent confirmatory clinical trials. 3) To explore the pharmacokinetics of human placental mesenchymal stem cell gel in the treatment of diabetic foot ulcers.