Development of plasma-on-chip: Plasma treatment for individual cells cultured in media

Abstract

A device consisting of Si microwells and microplasma sources has been fabricated for plasma treatment of individual cells cultured in media. We named the device plasma-on-chip. The microwells have through-holes at the bottom where gas–liquid interfaces form when they are filled with media containing biological samples. The microplasma sources, which supply reactive species, are located on the back of each microwell. Through the gas–liquid interface, the reactive species are supplied to the cells. Chlorella cells were used to demonstrate the feasibility of the device and after three minutes of plasma treatment, the fluorescence intensity of Chlorella cells appeared to be decreased. Optical emission spectroscopy identified O and OH radicals in the plasma, which can affect the cells. In the analysis of biological samples such as human cells or tissues, this device raises the possibility of revealing the mechanisms of plasma medicine in more detail.

Plasma cell treatment device Plasma-on-Chip: Monitoring plasma-generated reactive species in microwells

“…Arrays of through-holes were fabricated in a 200-μm-thick Si substrate (22 mm × 22 mm) by a deep reactive ion etching technique (etching depth: 200 μm) 32 . Three different sizes (50 μm × 50 μm, 100 μm × 100 μm, and 200 μm × 200 μm) of through-hole arrays were created, with distances between the through-holes of 150 μm, 300 μm, and 600 μm, respectively.…”

“…It is readily understood that the plasma affects cells in the vicinity of the treated area. Figure 1 illustrates what occurs when the plasma irradiation area is reduced to a size as small as a cell (plasma ≒ cell) or smaller (plasma < cell) 30 31 32 33 34 . In these cases, we expect that the plasma treatment activates or inactivates biological reactions at the single-cell level.…”

“…We have developed a plasma cell culture device that enables plasma treatment at the single-cell level ( Fig. 2 ) 32 33 34 . The device is referred to as “ Plasma-on-Chip ” and is used to analyse the interactions between the plasma and cells in real time.…”

“…If the size of the through-hole is reduced to smaller than that of a cell, the cell is locally treated with plasma, which can selectively activate or inactivate the specific functions of the cell. Thus far, we have reported the inactivation of Chlorella cells with the Plasma-on-Chip device 32 34 …”

“…To analyse the plasma-cell interaction in more detail, we should know the behaviour of the reactive species during treatment. In the gas phase, optical emission spectroscopic studies showed that the plasma can generate elements to form RONS, including excited O* atoms, excited N 2 molecules, and OH radicals 32 34 43 . Ionic species were also identified by ambient molecular beam mass spectrometry 44 45 46 .…”