A Device for Ligand-Free Single Cell Loading Using Magnetic Fields and Paramagnetic Microspheres

A combination of mechanical and chemical signals govern tissue responses. Examination of the individual cellular response to the mechanical and the chemical stimuli is essential to understanding these tissue responses. The objective of this study was to develop and optimize a device enabling examination of cellular response under ligand-free compressive loading. This procedure will elicit cellular responses to mechanical loading without confounding biochemical signals imparted by tethering proteins. Particular loading parameters such as amplitude, duration, duty cycle, and frequency require investigation as they likely play a role in mechanotransduction control. We achieved cell nucleus loading through control of paramagnetic microspheres using magnetic fields generated by a hollow solenoid encircling a microscope objective. We placed paramagnetic microspheres upon A549 lung carcinoma epithelial cells in a coverslip dish with a current applied to a solenoid located below the dish. The magnetic field drew the paramagnetic microspheres towards the cells, resulting in nucleus deformation. We captured and analyzed images for morphological changes of the cell nuclei before and during the loading cycle. The results of this study represent the proof of concept for a ligand-free single-cell mechanical loading device for application of compressive loads using paramagnetic microspheres. Applications of this technology include studies involving effects of compressive loading on cell growth as well as investigations into the efficacy of therapeutic drugs when presented to diseased cells.