A bio-syncretic phototransistor based on optogenetically engineered living cells.

Human eyes rely on photosensitive receptors to convert light intensity into action potentials for visual perception, and thus bio-inspired photodetectors with bioengineered photoresponsive elements for visual prostheses have received considerable attention by virtue of superior biological functionality and better biocompatibility. However, the current bioengieered photodetectors based on biological elements face a lot of challenges such as slow response time and lack of effective detection of weak bioelectrical signals, resulting in difficulty to perform imaging. Here, we report a human eye-inspired phototransistor by integrating optogenetically engineered living cells and a graphene-based transistor. The living cells, engineered with photosensitive ion channels, channelrhodopsin-2 (ChR2), and thus endowed with the capability of transducing light intensity into bioelectrical signals, are coupled with the graphene layer of the transistor and can regulate the transistor's output. The results show that the photosensitive ion channels enable the phototransistor to output stronger photoelectrical currents with relatively fast response (~25 ms) and wider dynamic range, and demonstrate the transistor owns optical and biological gating with a significant large on/off ratio of 197.5 and high responsivity of 1.37 mA W-1. An artificial imaging system, which mimics the pathway of human visual information transmission from the retina through the lateral geniculate nucleus to the visual cortex, is constructed with the transistor and demonstrate the feasibility of imaging using the bioengineered cells. This work shows a potential that optogenetically engineered cells can be used to develop novel visual prostheses and paves a new avenue for engineering bio-syncretic sensing devices.