A 48-year-old woman with poorly controlled type 2 diabetes mellitus (HbA1c 9.8%) undergoes elective hysterectomy. On postoperative day 12, the surgical wound shows delayed healing with minimal granulation tissue formation and persistent serosanguinous drainage. The patient is afebrile and hemodynamically stable. Which investigation would best assess the adequacy of wound healing and identify any underlying collagen deposition abnormality?