In situ bioimaging of Lactobacillus by photoluminescence of MoS₂

Due to unique properties arising from its 2D nature, molybdenum disulfide (MoS₂) has been studied widely toward its application for biosensing. While MoS₂ field effect transistor has been utilized for electrical detection of biological events in many studies, photoluminescence (PL) characteristics of MoS₂ have been poorly employed. MoS₂ PL can provide not only information of interactions between biological moieties and the surface, but also their spatial distribution. In this work, we utilized PL of single-layer MoS₂ as a label-free bioimaging sensor. To fabricate the imaging device, we synthesized MoS₂ by chemical vapor deposition and transferred it on a glass substrate with patterned electrodes. We employed Lactobacillus known as a probiotic microorganism to demonstrate the ability of bioimaging. We found that the MoS₂ PL can be modulated by the concentration of lactic acid. Finally, we succeeded in monitoring PL image of MoS₂ modulated by Lactobacillus, which can be correlated with the production of lactic acid by Lactobacillus. (paper)