Surface Coating of a Metal Mesh Device Sensor With Gold to Improve the Separation and Sensing of Mammalian Cells

Separation and detection of particular cells from culture media and clinical specimens is important for cell engineering and clinical examination. In this paper, we developed a metal mesh device (MMD) in which a thin nickel mesh with periodic microstructures consisting of square apertures plays a pivotal role in cellular fractionation and sensing. The mesh aperture in our 100-THz MMD had a side length of 1.8 $\mu \text{m}$ . This size of aperture was suitable for optically sensing mesh-captured particles by detecting transmittance of the corresponding electromagnetic waves, and simultaneously functioned as a sieve to separate microspheres according to their size. HeLa cells could be selectively captured by filtration through the 100-THz MMD, and the captured cells were detected by infrared transmittance changes. Coating of the mesh with gold improved sensing capability by sharpening of the transmittance peak. Most (98%) HeLa cells captured on the gold-coated mesh were viable and proliferated normally when re-cultured. When a mixture consisting of HeLa cells and an excess number of erythrocytes was filtered, HeLa cells were captured on the mesh, whereas erythrocytes were not, even though the average size of erythrocytes was much larger than the mesh aperture. Thus, gold-coated mesh may be useful for separating solid tumor-derived circulating cancer cells from erythrocytes, a major blood cell type. In addition, metal mesh-aided recovery of mammalian cells from cultures without cellular damage may facilitate the large-scale culture in cell biotechnology, because centrifugation, a laborious process for harvesting cells, becomes dispensable.