High-Speed Liquid Switching and On-Chip Force Sensing Reveal the Transient Mechanical Response of MscL in Synechocystis sp. PCC 6803

Abstract

How cells mechanically respond to rapid stimulation in the extracellular microenvironment is a key question for understanding the physiological functions of mechanosensitive (MS) channels. In this study, we investigated the single Synechocystis sp. PCC 6803 cell transient mechanical response under osmotic downshock using a microfluidic system that assembles a robot-integrated microfluidic chip with a synchronized injection-aspiration liquid switching module. Through theoretical analysis and system optimization, we achieved high-speed, localized liquid switching on the millisecond scale while simultaneously measuring cell deformation and reactive force. Using this system, we compared the Young's modulus of wild-type (WT) and MS channel-deficient mutant (ΔmscL) cells in hypoosmotic and hyperosmotic conditions, and quantified their transient mechanical responses under millisecond-scale liquid switching times. In particular, we compared the response time and key deformation parameters (expansion and shrinkage rates) of the two strains when the cells were compressed under osmotic downshock. Multi-parameter analysis suggested that MscL transiently gates to buffer membrane tension during osmotic downshock, thereby delaying deformation and preventing excessive swelling or rupture. These findings advance the understanding of cellular mechanical adaptation under rapid environmental transitions and demonstrate the broad applicability of this integrated microfluidic system for high-speed liquid switching and synchronous force sensing in single-cell mechanobiological studies.