Bioelectronics of The Cellular Cytoskeleton: Monitoring Cytoskeletal Conductance Variation for Sensing Drug Resistance

Actin and microtubules form cellular cytoskeletal network, which mediates cell shape, motility and proliferation and are key targets for cancer therapy. Changes in cytoskeletal organization dramatically affect mechanical properties of the cells and correlate with proliferative capacity and invasiveness of cancer cells. Changes in the cytoskeletal network expectedly lead to altered nonmechanical material properties including electrical conductivity as well. Here we applied, for the first time, microtubule and actin based electrical measurement to monitor changes in the electrical properties of breast cancer cells upon administration of anti-tubulin and anti-actin drugs, respectively. Semiconductive behavior of microtubules and conductive behavior of actins presented different bioelectrical responses (in similar frequencies) of the cells treated by anti-tubulin with respect to anti-actin drugs. Doped silicon nanowires were applied as the electrodes due to their enhanced interactive surface and compatibility with electronic fabrication process. We found that treatment with Mebendazole (MBZ), a microtubule destabilizing agent, decreases electrical resistance while treatment with Paclitaxel (PTX), a microtubule stabilizing agent, leads to an increase in electrical resistance. In contrast, actin destabilizing agents, Cytochalasin D (CytD), and actin stabilizing agent, Phalloidin, lead to an increased and decreased electrical resistance, respectively. Our study thus provides proof-of-principle of the usage of determining the electrical function of cytoskeletal compartments in grading of cancer as well as drug resistance assays.

Nanoelectromechanical Chip (NELMEC) Combination of Nanoelectronics and Microfluidics to Diagnose Epithelial and Mesenchymal Circulating Tumor Cells from Leukocytes

An integrated nano-electromechanical chip (NELMEC) has been developed for the label-free distinguishing of both epithelial and mesenchymal circulating tumor cells (ECTCs and MCTCs, respectively) from white blood cells (WBCs). This nanoelectronic microfluidic chip fabricated by silicon micromachining can trap large single cells (>12 µm) at the opening of the analysis microchannel arrays. The nature of the captured cells is detected using silicon nanograss (SiNG) electrodes patterned at the entrance of the channels. There is an observable difference between the membrane capacitance of the ECTCs and MCTCs and that of WBCs (measured using SiNG electrodes), which is the key indication for our diagnosis. The NELMEC chip not only solves the problem of the size overlap between CTCs and WBCs but also detects MCTCs without the need for any markers or tagging processes, which has been an important problem in previously reported CTC detection systems. The great conductivity of the gold-coated SiNG nanocontacts as well as their safe penetration into the membrane of captured cells, facilitate a precise and direct signal extraction to distinguish the type of captured cell. The results achieved from epithelial (MCF-7) and mesenchymal (MDA-MB231) breast cancer cells circulated in unprocessed blood suggest the significant applications for these diagnostic abilities of NELMEC.

Monitoring the spreading stage of lung cells by silicon nanowire electrical cell impedance sensor for cancer detection purposes

We developed a silicon nanowire based electrical cell impedance sensor (SiNW-ECIS) as an instrument that detects cancerous cultured living lung cells by monitoring their spreading state at which the cells stretched and become extended on nanowires. Further current penetration into the extended membrane of malignant cells in respect to normal ones (In the first 6h after cells interaction with surface) are the key mechanism in our diagnosis procedure. The developed device applied to monitor the spreading-induced electrical differences between cancerous and normal lung cells in an integral fashion. Detection was performed so faster than the time required to complete cells mitosis. Morphology and architecture of doped Si nanowires covered microelectrodes observably enhance the contact area between cells and electrodes which support accurate signal recording from stretched cells as indicated by SEM and florescent images.