(WHS-P54) A NOVEL HYDROGEL IONIC CIRCUIT ELECTRODE FOR SAFE AND EFFECTIVE ELECTROTAXIS FOR CHRONIC WOUND HEALING
Friday, May 17, 2024
7:30 AM – 5:00 PM East Coast USA Time
A key cause of delayed healing in chronic wounds is the impaired cell migration due to systemic illnesses and advanced age. The current clinical care does not specifically address this impairment. Electrotaxis is the directional and accelerated cell migration guided by a direct current electric field (DC EF). Electrotaxis shows good efficacy in in vitro cell migration. But its in vivo efficacy is limited due to the difficulty in safely applying the EF strength typically used in in vitro studies (200 mV/mm) to in vivo tissues. Tissue damage can be caused by electrochemical reaction (ECR)-induced pH/temperature changes at high EF strengths. We developed a novel hydrogel ionic circuit (HIC) electrode to minimize pH/temperature changes when applying high-strength DC EFs. Our goal here was to determine the safety and in vitro electrotaxis efficacy of HIC electrodes when applying 200 mV/mm and higher DC EFs. A HIC electrode consists of a carbon electrode inserted in a chamber filled with a saturated phosphate salt solution to absorb ECR-induced pH/temperature changes. The chamber is separated from the skin by a polyethylene glycol hydrogel, which prevents high-concentration phosphate salt ions from diffusing into the tissue. To evaluate the safety, 3 DC EF strengths (200, 400, and 800 mV/mm) were applied to pig skin for 5 hrs. Skin pH and temperature were measured right after EF application. An in vitro electrotaxis setup and HaCaT cells were used to test the electrotaxis efficacy. 200, 400, and 800 mV/mm were applied for 5 hrs. The directedness and projected migration speed along the EF direction of HaCaT were calculated. Directedness is a measure of cell migration direction, which is the cosine of the angle between the migration and the EF vectors. 3 repeats were used for safety experiments. 100 cells were analyzed in each migration experiment. At all 3 DC EFs tested, HIC electrodes maintained a safe skin temperature below 42.8°C and a safe skin pH between 5.9 and 6.9. But a conventional carbon electrode increased the skin temperature to 43.9°C, 49.7°C, and 53.0°C at 200, 400, and 800 mV/mm, respectively. It changed the skin pH to 4.0(anode)/10.7(cathode) and 2.4(anode)/13.1(cathode) at 400 and 800 mV/mm, respectively. These pH/temperature changes can cause skin damage. At 200 mV/mm, HIC electrodes achieved similar directedness (0.67) and projected speed (11.1 µm/hr) as conventional carbon electrodes. At higher DC EFs, HIC electrodes significantly (P <0.05) increased the directedness to 0.90 and 0.95 and the projected speed to 33.2 and 61.8 µm/hr at 400 and 800 mV/mm, respectively. In summary, we showed the ex vivo safety of HIC electrodes when applying 200 mV/mm and higher DC EF to skin tissues. We showed that high-strength DC EFs applied by HIC electrodes enhanced the directedness and projected migration speed of HaCaT cells compared to 200 mV/mm DC EF.