‘Living cantilever arrays’ for characterization of mass of single live cells in fluids

Abstract

The size of a cell is a fundamental physiological property and is closely regulated by various environmental and genetic factors. Optical or confocal microscopy can be used to measure the dimensions of adherent cells, and Coulter counter or flow cytometry (forward scattering light intensity) can be used to estimate the volume of single cells in a flow. Although these methods could be used to obtain the mass of single live cells, no method suitable for directly measuring the mass of single adherent cells without detaching them from the surface is currently available. We report the design, fabrication, and testing of 'living cantilever arrays', an approach to measure the mass of single adherent live cells in fluid using silicon cantilever mass sensor. HeLa cells were injected into microfluidic channels with a linear array of functionalized silicon cantilevers and the cells were subsequently captured on the cantilevers with positive dielectrophoresis. The captured cells were then cultured on the cantilevers in a microfluidic environment and the resonant frequencies of the cantilevers were measured. The mass of a single HeLa cell was extracted from the resonance frequency shift of the cantilever and was found to be close to the mass value calculated from the cell density from the literature and the cell volume obtained from confocal microscopy. This approach can provide a new method for mass measurement of a single adherent cell in its physiological condition in a non-invasive manner, as well as optical observations of the same cell. We believe this technology would be very valuable for single cell time-course studies of adherent live cells.

Measurement of single leukemia cell's density and mass using optically induced electric field in a microfluidics chip

“…Two well-known methods, i.e., suspended microchannel resonator (SMR) [3][4][5] and pedestal resonant sensor (PRS), [6][7][8] have been developed based on physical approaches using micro resonators. Although both of them involve complicated fabrication and indirect mappings between the cell mass and the measured physics-parameters, these two methods have been found to be applicable in the measurement of the density and mass of single cells.…”

Enhancing the Performance of Surface-based Biosensors by AC Electrokinetic Effects - a Review

“…However, Islam et al (2007) successfully applied AC electroosmotic flow to drive polystyrene particles to a point near the anchor and detected a mass change after drying. (Park et al, 2008). Reused with permission.…”

“…As more bioparticles become deposited on the surface, the shift becomes more pronounced. The combination of AC electrokinetics with a cantilever beam was recently achieved and allowed for the rapid collection of human cancer cells (Park et al, 2008). Using two conductive cantilevers situated across from one another over a well, Park et al used pDEP to direct the human cancer cells onto the cantilever surface.…”

Integrated optical dual-cantilever arrays in silica on silicon

“…A three stage model was built that first simulates the thermal oxide and FHD glass depositions to simulate the thermal stresses that are built up once the consolidated glass layers are cooled to room temperature. The 3 rd stage was to model the out of plane deflections once the cantilevers are freed from the silicon substrate. The following values were used for the thermal expansion coefficients.…”

“…Ollier et al fabricated an optical switch based on silica-on-silicon technology that used electrostatic switching to function as a switch between channel waveguides [2]. While single cantilevers provide a way to create devices, the use of dual cantilevers has been pioneered by Park et al as a way of attracting cells to adhere to a cantilever, whereon they can be cultured and weighed using a resonance frequency method [3]. In another example of this geometry Xu et al fabricated dual cantilevers in polymer, which also served as waveguides, in a device that functioned as an acoustic sensor [4].…”