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7 results on '"Swami, N. S."'

1. Two-Potential Electrochemical Probe for Study of DNA Immobilization

Author

Swami, N. S., Chou, C.-F., and Terberueggen, R.

Abstract

A two-potential electrochemical method is applied to study DNA immobilization, by the simultaneous characterization of capture probe DNA self-assembled monolayers and hybridized target DNA molecules on a given gold electrode surface. Capture probe and target DNA strands are labeled with ferrocenes composed of differing chemical environments, to permit their simultaneous, yet independent signaling at different formal potentials, so that their respective signals may be de-convoluted and assessed for relative surface concentration. Some special attributes of the nondestructive two-potential electrochemical probe described herein include surface sensitivity, chemical and orientation specificity, and the ability to provide a real-time, in situ probe that does not need any wash steps for stringency. This electrochemical probe is applied to study the kinetics, surface architecture, coverage, and orientation of DNA during its immobilization on gold. On the basis of our results primarily from this electrochemical probe, and validated by N(1s) core-level X-ray photoelectron spectra, we judge significant DNA deposition within 5 min of incubation in the deposition solutions, with the capture probe DNA anchored predominantly via the thiol end, even at low coverages. Surface coverage for DNA immobilization plateaus within 30 min of incubation time to ~2 × 1013 molecules/cm2 and the immobilization kinetics as determined from this electrochemical method are consistent with surface re-organization as the rate-determining step.

Published
2005

7. Electrophysiology-based stratification of pancreatic tumorigenicity by label-free single-cell impedance cytometry.

Author

McGrath JS, Honrado C, Moore JH, Adair SJ, Varhue WB, Salahi A, Farmehini V, Goudreau BJ, Nagdas S, Blais EM, Bauer TW, and Swami NS

Subjects
Adenocarcinoma genetics, Adenocarcinoma pathology, Adenocarcinoma physiopathology, Animals, Carcinoma, Pancreatic Ductal genetics, Carcinoma, Pancreatic Ductal pathology, Carcinoma, Pancreatic Ductal physiopathology, Cell Line, Tumor, Electric Impedance, Electrophysiology instrumentation, Electrophysiology methods, Gene Expression Regulation, Neoplastic, Heterografts physiopathology, Humans, Liver pathology, Liver physiopathology, Mice, Microfluidics instrumentation, Microfluidics methods, Pancreas pathology, Pancreas physiopathology, Proto-Oncogene Proteins p21(ras) genetics, Single-Cell Analysis instrumentation, Single-Cell Analysis methods, Adenocarcinoma diagnosis, Carcinoma, Pancreatic Ductal diagnosis
Abstract

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer lacking specific biomarkers that can be correlated to disease onset, promotion and progression. To assess whether tumor cell electrophysiology may serve as a marker for PDAC tumorigenicity, we use multi-frequency impedance cytometry at high throughput (∼350 cells/s) to measure the electrical phenotype of single PDAC tumor cells from xenografts, which are derived from primary pancreatic tumors versus those from liver metastases of different patients. A novel phase contrast metric based on variations in the high and low frequency impedance phase responses that is related to electrophysiology of the cell interior is found to be systematically altered as a function of tumorigenicity. PDAC cells of higher tumorigenicity exhibited lowered interior conductivity and enhanced permittivity, which is validated by the dielectrophoresis on the respective cell types. Using genetic analysis, we suggest the role of dysregulated Na + transport and removal of Ca 2+ ions from the cytoplasm on key oncogenic KRAS-driven processes that may be responsible for lowering of the interior cell conductivity. We envision that impedance cytometry can serve as a tool to quantify phenotypic heterogeneity for rapidly stratifying tumorigenicity. It can also aid in protocols for dielectrophoretic isolation of cells with a particular phenotype for prognostic studies on patient survival and to tailor therapy selection to specific patients., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Published
2020
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