Oxygen consumption of cell suspension in a poly(dimethylsiloxane) (PDMS) microchannel estimated by scanning electrochemical microscopy

Abstract

A quantitative analysis of the oxygen concentration profile near a poly(dimethylsiloxane) (PDMS) microfluidic device was performed using scanning electrochemical microscopy (SECM). A microchannel filled with sodium sulfite (Na(2)SO(3)) aqueous solution was imaged by SECM, showing that the oxygen diffusion layer of the PDMS microchannel was observed to be hemicylindrical. Based on a theoretical analysis of the hemicylindrical diffusion layer of the microchannel, the total oxygen mass transfer rates of oxygen to the PDMS microchannel filled with the Na(2)SO(3) solution was calculated to be (4.01 +/- 0.30) x 10(-12) mol s(-1). This is the maximum value of the oxygen transfer rate for this PDMS microchannel device. The oxygen consumption rate increased almost linearly with the logarithm of the concentration of E. coli cells (10(6) approximately 10(8) cells). The respiratory activity for a single E. coli cell was estimated to be approximately 4.31 x 10(-20) mol s(-1) cell(-1).

Addressing surface leakage in type-II InAs/GaSb superlattice materials using novel approaches to surface passivation

“…Furthermore, in an effort to address concerns regarding the long term stability of sulfide surface treatments, the application of a second SU8-2 layer made permanent by an elevated anneal step (150ºC) is introduced to temporarily preserve the sulfidized surface by minimizing atmospheric exposure. In this study, no investigations have been made to observe the atmospheric permeability of SU8-2, however, there have been previous studies attesting to the very low oxygen permeability of SU8 as compared with poly(dimethylsiloxane) PDMS 20 . In addition to these two-step passivation studies, further validation of surface modification has been provided by way of unpassivated and SU8-2 only passivated devices.…”

Chip Based Electroanalytical Systems for Cell Analysis

“…A common approach to monitor the consumption of oxygen by cells amperometrically is by the use of fiber based electrodes [100 -102], however, a few reports have addressed construction of microchip-based amperometric oxygen sensors intended for cell analysis [99,103]. Saito et al [104] proposed a system composed of a PDMS microchannel in combination with SECM to monitor oxygen consumption by E. coli bacteria. They determined the oxygen consumption for a single E. coli cell to be ca.…”

Real-time electrocatalytic sensing of cellular respiration

“…The current electrochemical BOD systems include the use of Clark-type electrodes (Suzuki et al, 2001), microchannel (Saito et al, 2006) and the use of ferricyanide as a mediator in the assay (Jordan et al, 2013; Pasco et al, 2004). The BODs that use the Clark-type electrode system are based on using platinum electrodes pre-coated with a Teflon membrane, allowing oxygen to diffuse through and be measured in real-time.…”

“…The microchannel system is highly sensitive, capable of monitoring single cell metabolism in a real time assay. However, it is relatively expensive and time consuming to fabricate the microchannels (Saito et al, 2006). The BOD assay that makes use of ferricyanide, involves incubating the cells with ferricyanide for one hour in a deoxygenated environment.…”