In‐depth analysis of pH‐dependent mechanisms of electromechanical reshaping of rabbit nasal septal cartilage

Abstract

Objectives/Hypothesis Electromechanical reshaping (EMR) involves reshaping cartilage by mechanical deformation and delivering electric current to the area around the bend axis, causing local stress relaxation and permanent shape change. The mechanism of EMR is currently unclear, although preliminary studies suggest that voltage and application time are directly related to the concentration and diffusion of acid–base products within the treated tissue with little heat generation. This study aims to characterize local tissue pH changes following EMR and to demonstrate that local tissue pH changes are correlated with tissue damage and shape change. Study Design Ex vivo animal study involving EMR of rabbit nasal septal cartilage and biochemical estimation of tissue pH changes. Methods The magnitude and diffusion of acid–base chemical products in control (0V, 2 minutes), shape change (4V, 4 minutes; 6V, 1, 2, 4 minutes; 8V, 1, 2 minutes), and tissue damage (8V, 4, 5 minutes; 10V, 4, 5 minutes) parameters following EMR are approximated by analyzing local pH changes after pH indicator application. Results There is a direct relationship between total charge transfer and extent of acid–base product diffusion (P <0.05). A “pH transition zone” is seen surrounding the bend apex above 8V, 2 minutes. Colorimetric analysis suggests that small local pH changes (10−8 hydrogen ions) are at least partly implicated in clinically efficacious EMR. Conclusions These results provide additional insight into the translational applications of EMR, particularly the relationship among pH changes, shape change, and tissue injury, and are integral in optimizing this promising technology for clinical use.

Multiphoton Microscopy of Collagen Structure in Ex Vivo Human Skin Following Electrochemical Therapy

“…Notably, the mean width at lowest time application (3 minutes), increase in mean width with time, and SD are all greater at the base site. This acid base dose–response relationship has been demonstrated in the previous studies . This process is mediated by the generation of chemical species and their migration down both their concentration gradient and electropotential gradient .…”

“…Previous studies in our lab have demonstrated collagen structural change in the rabbit cartilage and pig skin [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. This study is the first to characterize the redoxinduced alteration in the optical and mechanical behavior in the human skin.…”

“…These ions create a steep pH gradient around the electrodes, which lead to localized stress relaxation and shape change, a process we refer to as electromechanical reshaping (EMR) [27,28]. Through a series of studies, we demonstrated the safety and efficacy of this approach to reshape cartilage [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. During these in vivo EMR studies in rabbits, changes in skin texture were incidentally observed around the non-insulated needle-insertion sites [12,15,24].…”

Long‐term in vivo electromechanical reshaping for auricular reconstruction in the New Zealand white rabbit model

“…Although we have begun to demonstrate the varying tissue changes that can occur with this technology, further investigation is needed to evaluate the response to a broader range of voltage‐time parameters and even longer implantation intervals. Moreover, specific characterization of the pH gradient occurring at anode and cathode sites will enhance our understanding of the tissue changes occurring within the cartilaginous matrix . Finally, the mechanical behavior of reshaped tissue can be further assessed via detailed mechanical analysis and finite element modeling to quantitatively assess the response to physical deformation following EMR.…”

“…Moreover, specific characterization of the pH gradient occurring at anode and cathode sites will enhance our understanding of the tissue changes occurring within the cartilaginous matrix. 27 Finally, the mechanical behavior of reshaped tissue can be further assessed via detailed mechanical analysis and finite element modeling to quantitatively assess the response to physical deformation following EMR.…”