Detecting Bacterial Cell Viability in Few µL Solutions from Impedance Measurements on Silicon-Based Biochips

• Main Authors: Vinayak J. Bhat, Sahitya V. Vegesna, Mahdi Kiani, Xianyue Zhao, Daniel Blaschke, Nan Du, Manja Vogel, Sindy Kluge, Johannes Raff, Uwe Hübner, Ilona Skorupa, Lars Rebohle, Heidemarie Schmidt
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: International Journal of Molecular Sciences
• Subjects: cell viability; Lysinibacillus sphaericus; impedance biochips; membrane potential; dead bacterial cells; live bacterial cells
• Online Access: https://www.mdpi.com/1422-0067/22/7/3541
• ISSN: 1661-6596; 1422-0067

Using two different types of impedance biochips (PS5 and BS5) with ring top electrodes, a distinct change of measured impedance has been detected after adding 1–5 µL (with dead or live Gram-positive <i>Lysinibacillus sphaericus</i> JG-A12 cells to 20 µL DI water inside the ring top electrode. We relate observed change of measured impedance to change of membrane potential of <i>L</i><i>.</i><i> sphaericus</i><i> </i>JG-A12<i> </i>cells. In contrast to impedance measurements, optical density (OD) measurements cannot be used to distinguish between dead and live cells. Dead <i>L. sphaericus</i><i> </i>JG-A12<i> </i>cells have been obtained by adding 0.02 mg/mL of the antibiotics tetracycline and 0.1 mg/mL chloramphenicol to a batch with OD0.5 and by incubation for 24 h, 30 °C, 120 rpm in the dark. For impedance measurements, we have used batches with a cell density of 25.5 × 10⁸ cells/mL (OD8.5) and 270.0 × 10⁸ cells/mL (OD90.0). The impedance biochip PS5 can be used to detect the more resistive and less capacitive live <i>L. sphaericus</i><i> </i>JG-A12<i> </i>cells. Also, the impedance biochip BS5 can be used to detect the less resistive and more capacitive dead <i>L. sphaericus</i><i> </i>JG-A12<i> </i>cells. An outlook on the application of the impedance biochips for high-throughput drug screening, e.g., against multi-drug-resistant Gram-positive bacteria, is given.