A Portable Arsenic Sensor Integrating <i>Bacillus megaterium</i> with CMOS Technology

Bacteria innately monitor their environment by dynamically regulating gene expression to respond to fluctuating conditions. Through synthetic biology, we can harness this natural capability to design cell-based sensors. <i>Bacillus megaterium</i>, a soil bacterium, stands out due to its remarkable heavy metal tolerance and sporulation ability, making it an ideal candidate for heavy metal detection with low transportation costs. However, challenges persist: the synthetic biology toolkit for this strain is underdeveloped, and conventional whole-cell sensors necessitate specialized laboratory equipment to read the output. In our study, we have genetically modified <i>B. megaterium</i> for arsenic detection and established a detection threshold below the EPA's recommendation of 10 ppb for drinking water in both vegetative and spore forms. Additionally, we have integrated both engineered <i>B. megaterium</i> living cells and spores with a complementary metal-oxide-semiconductor (CMOS) chip, providing a proof-of-concept for field-deployable arsenic detection. We show that the limit of detection (LOD) of our integrated sensor is within the range to test arsenic levels in soil and food. As a proof of concept, this work paves the way for the deployment of our sensor in resource-limited settings, ensuring real-time arsenic detection in challenging environments.