During a 24-h period, equal amounts of ulcer secretion were collected by absorption using 1 cm2 of absorbent material (Mepilex, Mölnly Health Care AB, Box 13080, SE 40252, Göteborg, Sweden) placed under the dressing and then transferred into a flask (scintillation vial 20 mL, Sarstedt AB, SE- 26151 Landskrona, Sweden) containing 5 ml physiological sodium chloride (NaCl). The sample was vortexed (Vortex-Genie, Scientific Industries, Inc., New York, USA) and centrifuged at 3000 × g for 10 min. The supernatant was transferred into tubes (Nunc Cryo Tube, Nunc Brand Products, Denmark) and stored at −70 °C before analysis.