  Biocomputing systems based on engineered bacteria can lead to novel tools for
environmental monitoring and detection of metabolic diseases. In this paper, we
propose a Bacterial Molecular Computing on a Chip (BMCoC) using microfluidic
and electrochemical sensing technologies. The computing can be flexibly
integrated into the chip, but we focus on engineered bacterial AND Boolean
logic gate and ON-OFF switch sensors that produces secondary signals to change
the pH and dissolved oxygen concentrations. We present a prototype with
experimental results that shows the electrochemical sensors can detect small pH
and dissolved oxygen concentration changes created by the engineered bacterial
populations' molecular signals. Additionally, we present a theoretical model
analysis of the BMCoC computation reliability when subjected to unwanted
effects, i.e., molecular signal delays and noise, and electrochemical sensors
threshold settings that are based on either standard or blind detectors. Our
numerical analysis found that the variations in the production delay and the
molecular output signal concentration can impact on the computation reliability
for the AND logic gate and ON-OFF switch. The molecular communications of
synthetic engineered cells for logic gates integrated with sensing systems can
lead to a new breed of biochips that can be used for numerous diagnostic
applications.
