Hypothesis and Evidence: Potential Cellular Damage Induced by Pipetting Flow

Fluid shear stress, a critical mechanical factor in the cellular microenvironment, regulates cell morphology, function, gene expression, and signaling pathways, making it a research focus in life sciences and biomedical engineering. Responses to shear stress vary significantly across cell types (e.g., vascular endothelial cells, chondrocytes, immune cells, and tumor cells), with force magnitude, duration, and flow patterns (laminar vs. turbulent) eliciting distinct biological effects. In the cardiovascular system, shear stress modulates atherosclerotic plaque stability by regulating endoplasmic reticulum stress proteins (e.g., GRP78 and CHOP). In cartilage, shear stress synergizes with inflammatory factors (e.g., TNF-α) to influence cell phenotype maintenance and extracellular matrix synthesis. Under pathological conditions (e.g., thrombosis), abnormally high shear stress (>1000 dyne/cm²) directly causes cell detachment and damage. Notably, cells exhibit "mechanical memory," whereby transient exposure to low shear stress triggers long-term changes in endothelial cell traction forces, altering alignment and function. Given that in vitro manipulations (e.g., pipetting) introduce uncontrolled fluid stress—compromising cell viability and experimental reproducibility—microfluidic technologies enabling precise shear stress control and standardization offer a vital solution to optimize cell-based assays and enhance data reliability.