Designing artificial cells to harness the biological ion concentration gradient

Abstract

Cell membranes contain numerous nanoscale conductors in the form of ion channels and ion pumps that work together to form ion concentration gradients across the membrane to trigger the release of an action potential. It seems natural to ask if artificial cells can be built to use ion transport as effectively as natural cells. Here we report a mathematical calculation of the conversion of ion concentration gradients into action potentials across different nanoscale conductors in a model electrogenic cell (electrocyte) of an electric eel. Using the parameters extracted from the numerical model, we designed an artificial cell based on an optimized selection of conductors. The resulting cell is similar to the electrocyte but has higher power output density and greater energy conversion efficiency. We suggest methods for producing these artificial cells that could potentially be used to power medical implants and other tiny devices.

Fig. 1. Anatomy of the electric eel and structure of the natural electrocyte

a , The anatomy of the electric eel; b, the electrocyte in the resting stage and, c, stimulated stage. Adapted from reference .

Fig. 2. Schematic diagram of a system of electrodenic cells used in the simulations and subsequent action potential formation

a , Multiple cells connected in series to drive an external circuit; b, Innervated membrane potential and transcellular potential from simulations (27 °C, data shown at 4.01 s) and recordings from a natural electrocyte; c, Regression results for Na (m³h), Kv (n⁴) and Kir channel open probability parameters for the innervated membrane.

Fig. 3. Action potentials formed in the artificial cell based on maximizing the single pulse energy output

(left) Transcellular potential of the electrocyte as a function of external resistance, R; (right) Peak of transcellular voltage output (V_AP) and single pulse energy output (W_s) as a function of R. (R normalized to R_st = 8.53×10⁻² Ω·m²·cell⁻¹.5).

Fig. 4. Action potentials formed in the artificial cell based on maximizing the power output and energy conversion efficiency over many seconds

a, AP formation when the cells are stimulated at the optimal interval (external resistance R = R_st, 27 °C, stimulus: −21.3 mV) b, maximum power output (P) as a function of R; c, maximum energy conversion efficiency (C) as a function of R.