Optoelectronic tweezers for the measurement of the relative stiffness of erythrocytes

摘要

In this paper we describe the first use of Optoelectronic Tweezers (OET), an optically controlled micromanipulationmethod, to measure the relative stiffness of erythrocytes in mice. Cell stiffness is an important measure of cell health andin the case of erythrocytes, the most elastic cells in the body, an increase in cell stiffness can indicate pathologies such astype II diabetes mellitus or hypertension (high blood pressure). OET uses a photoconductive device to convert an opticalpattern into and electrical pattern. The electrical fields will create a dipole within any polarisable particles in the device,such as cells, and non-uniformities of the field can be used to place unequal forces onto each side of the dipole thusmoving the particle. In areas of the device where there are no field gradients, areas of constant illumination, the force oneach side of the dipole will be equal, keeping the cell stationary, but as there are opposing forces on each side of the cellit will be stretched. The force each cell will experience will differ slightly so the stretching will depend on the cellspolarisability as well as its stiffness. Because of this a relative stiffness rather than absolute stiffness is measured. Weshow that with standard conditions (20Vpp, 1.5MHz, 10mSm-1 medium conductivity) the cell’s diameter changes byaround 10% for healthy mouse erythrocytes and we show that due to the low light intensities required for OET, relativeto conventional optical tweezers, multiple cells can be measured simultaneously.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.