[Effects of nerve growth factor-insulin composite gel on deep second degree scald wound healing in diabetic rats]

To prepare nerve growth factor (NGF)-insulin composite gel and observe the effects of NGF-insulin composite gel on deep second degree scald wound healing in diabetic rats.

Carbomer 980, NGF (4 000 U), and insulin (800 U) were used to prepare the insulin gel, NGF gel, and NGF-insulin composite gel. The character of NGF-insulin composite gel was observed, and the in vitro drug release was tested. Seventy-five SPF Wistar male rats, weighing 200-250 g, were divided into 5 groups randomly, 15 rats each group: normal control group (group A), diabetes control group (group B), insulin gel treatment group (group C), NGF gel treatment group (group D), and NGF-insulin composite gel treatment group (group E). The type 1 diabetes rat model was established by intraperitoneal injection of Streptozotocin (55 mg/kg) in groups B, C, D, and E, while the rats in group A were injected with the same dose of citric acid and calcium citrate buffer. After modeling success, deep second degree scald wound on the back was made with constant temperature water bath box. Wounds were treated with carbomer blank gel in groups A and B, with insulin composite gel in group C, with NGF gel in group D, and with NGF-insulin composite gel in group E, once a day. At 3, 7, 11, 15, and 21 days after injury, the scald wound healing was observed and healing rate was calculated; the full-thickness skin specimens were harvested from 3 rats of each group for histological and immuohistochemical staining observation.

The NGF-insulin composite gel was clear and transparent, and had good moisture retention capacity and adhesion; it was easy to apply and clean up. The drug release in vitro lasted more than 24 hours and maintained for 30 days. No rat died during the experiment. At 3 days after injury, wound area did not reduce in all groups; at 7, 11, 15, and 21 days, group E had the highest wound healing rate, and group B had the lowest; significant differences were found between group E and group B and when compared with the other groups (P < 0.05). HE staining showed that group E surpassed other groups in the growth of granulation tissue and collagen fiber. Immunohistochemical results showed that the CD34 and proliferating cell nuclear antigen (PCNA) expressed at 3 days, and the number of positive cells increased gradually with time; the microvessel density and PCNA expression were highest in group E and were lowest in group B, showing significant differences when compared with the other groups and between group E and group B (P < 0.05).

NGF-insulin composite gel can improve deep second degree scald wound healing in diabetic rats.