A pH-based bio-rheostat: a proof-of-concept

TL;DR

This paper demonstrates the feasibility of using the Reaction Center protein as a pH-sensitive bio-rheostat, showing its electrical resistance varies significantly with pH, paving the way for bio-based electronic devices.

Contribution

It introduces a novel concept of a bio-rheostat based on a photosensitive protein, supported by a microscopic model and experimental validation, for pH-dependent electronic applications.

Findings

Resistance increases by about 100% from pH 10 to 6.5

Model predictions agree with atomic force microscopy data

Supports potential for bio-based electronic device development

Abstract

New science and new technology need new materials and new concepts. In this respect, biological matter can play a primary role because it is a material with interesting and innovative features that have found several applications in technology, from highly sensitive sensors for medical treatments to devices for energy harvesting. Furthermore, most of its phenomenology remains unclear thus giving new hints for speculative investigations. In this letter, we explore the possibility to use a well-known photosensitive protein, the Reaction Center of Rhodobacter Sphaeroides, to build up an electrical pH sensor, i.e., a device able to change its resistance depending on the pH of the solution in which it crystalizes. By using a microscopic model successfully tested on analogue proteins, we investigate the electrical response of the Reaction Center single protein under different conditions of applied bias, showing the feasibility of the bio-rheostat hypothesis. As a matter of facts, the calculated resistance of this protein grows of about 100% when going from a pH = 10 to a pH = 6.5. Moreover, calculations of the current voltage characteristics well agree with available experiments performed with a current atomic force microscopy under neutral conditions. All findings are in qualitative agreement with the known role of pH in biochemical activities of Reaction Center and similar proteins, therefore supporting a proof-of-concept for the development of new electron devices based on biomaterials.