A simple mathematical model for electric cell-substrate impedance sensing with extended applications

• Published in: Biosensors & bioelectronics Vol. 25; no. 7; pp. 1774 - 1780
• Main Authors: Xiao, Caide, Luong, John H.T.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.03.2010; Elsevier
• Subjects: Anti-Bacterial Agents - administration & dosage; Antibiotics resistance; Bacteria; Bacterial Physiological Phenomena - drug effects; Bacterial Physiological Phenomena - radiation effects; Biological and medical sciences; Biological Assay - instrumentation; Biosensing Techniques - instrumentation; Biosensing Techniques - methods; Biotechnology; Computer Simulation; Computer-Aided Design; Conductometry - instrumentation; Conductometry - methods; Doubling time; Electric cell-substrate impedance sensing; Electromagnetic Fields; Equipment Design; Equipment Failure Analysis; Ferri/ferrocyanide; Fundamental and applied biological sciences. Psychology; l-Cysteine; Mathematical model; Models, Biological; Plethysmography, Impedance - instrumentation; Reproducibility of Results; Sensitivity and Specificity; l-Cysteine; Ferri/ferrocyanide; Doubling time; Electric cell-substrate impedance sensing; Bacteria; Mathematical model; Antibiotics resistance; Cysteine; Resistance; Substrate; Antibiotic; L-Cysteine; Impedance; Application
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/j.bios.2009.12.025

This paper presents a simple mathematical model to predict the impedance data acquired by electric cell-substrate impedance sensing (ECIS) at frequencies between 25Hz and 60kHz. With this model, the equivalent resistance (R) and capacitance (C) of biological samples adhered on gold surfaces could be more precisely measured at 4kHz. ECIS applications were extended for real-time monitoring of living bacteria cultivated in Luria Bertani (LB) culture medium by two different approaches. In the former, we used a ferri/ferrocyanide redox couple in LB medium as an indicator for bacterial multiplication. Because the redox couple was toxic to some bacteria, we developed a second approach, in which l-cysteine self-assembled monolayers (SAM) on gold electrodes were used to detect living bacteria. The l-cysteine SAM could also be detected by ECIS. Unlike traditional impedance microbiological methods which need special culture media with low ions, our procedures significantly enhanced signal/noise ratios so bacteria could be detected in general purpose culture media. It was easy and convenient to obtain bacterial doubling times and evaluate the resistance of bacteria to antibiotics from ECIS spectra.