In-silico Feedback Control of a MIMO Synthetic Toggle Switch via Pulse-Width Modulation
This work addresses the need for real-time feedback control in synthetic biology, but the results are incremental as they build on existing models and simulation-based validation.
The paper develops feedback control strategies (hybrid PI-PWM and Zero-Average dynamics) for a synthetic toggle switch using pulse-width modulation inputs, validated via deterministic and stochastic simulations showing improved regulation over open-loop methods.
The synthetic toggle switch, first proposed by Gardner & Collins [1] is a MIMO control system that can be controlled by varying the concentrations of two inducer molecules, aTc and IPTG, to achieve a desired level of expression of the two genes it comprises. It has been shown [2] that this can be accomplished through an open-loop external control strategy where the two inputs are selected as mutually exclusive periodic pulse waves of appropriate amplitude and duty-cycle. In this paper, we use a recently derived average model of the genetic toggle switch subject to these inputs to synthesize new feedback control approaches that adjust the inputs duty-cycle in real-time via two different possible strategies, a model based hybrid PI-PWM approach and a so-called Zero-Average dynamics (ZAD) controller. The controllers are validated in-silico via both deterministic and stochastic simulations (SSA) illustrating the advantages and limitations of each strategy