3.3 Animals and surgical procedure
Adult male Sprague–Dawley rats (weight: 220–250 g) were purchased from the Laboratory Animals Centre, Zhengzhou University. All animal operations and experiments were approved by the Zhengzhou University Animal Care Committees. The rats were anesthetised with 4% isoflurane inhalant anaesthetic and maintained at surgical plane anaesthesia with 2.5% isoflurane throughout the procedure. The samples were assigned to six groups, as follows: freeze-drying (ks-f, kc-f, and k-f) and oven-drying (ks-o, kc-o, and k-o). Following the preparation of the dorsum of the rats, a midline skin incision of approximately 2 cm was made, and the skin and subcutaneous tissues were bluntly dissected. The samples (1.5-cm length, 1.5-cm width, and 0.5-cm height) were subcutaneously implanted into the rats. Following the placement of the samples, the skin and fascia were sutured with 5-0 sutures. Upon completion of the surgical procedure, the inhalant anaesthetic gases were discontinued, and the animal was recovered from anaesthesia. All animals were housed in plastic boxes at a controlled temperature (23 ±2℃) and were provided ad libitum food and water under a standard 12-h on/off light cycle.