Date of Award

Summer 2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Micro and Nanoscale Systems

First Advisor

Long Que

Abstract

Nanotechnology is a multidisciplinary field that combines science and engineering to design, synthesize, characterize and explore applications for materials and devices whose smallest functional organization in at least one dimension is on the nanometer scale. Nanotechnology is undergoing an explosive development and the extent of potential application is vast and widely diverse. In the field of human health care, nanotechnology is helping to develop novel materials and structures, which have made it possible to miniaturize many of the tools used in conventional assays. Smart biochips constructed out of these novel materials and structures are now capable of performing limited in vitro diagnostic tests involved in immunoassays. In this work, we report two devices that make use of micro scale and/or nano scale structures to contribute to the ever-expanding use of biochips in human health care.

The first device is a Patch-Clamp microchip that is capable of monitoring cell viability in real-time. It is critical to monitor the health of cells in biological life science and medical research. Researchers must know if a new drug is capable of killing cancer cells or in other cases to determine the toxic effects of a drug or a pesticide on healthy cells. Conventional cell viability monitoring techniques that use flow cytometer or fluorescent dyes in conjunction with fluorescence microscope are time consuming and require sample labeling. Alternatively, we have designed a patch-clamp microchip, which allows one to measure the ion-channel currents in real-time. This microchip provides a faster and label-free platform to monitor the health of the cell. Simultaneously, viability tests were performed on four different types of cancer cells (MB231, MB231-BR-vector, MB231-BR-HER 2, and MB231-BR) using the conventional fluorescent dye technique and using the patch-clamp microchip technique. For the patch-clamp technique, the seal resistance of the device decreased from ∼22 MΩ, (living cell) to ∼4 MΩ (dead cell) over a period of 120 minutes. Comparing the seal resistance to the intensity of the fluorescence images over the 120 minute period confirms a correlation between the health of the cell and the ion-channel current, validating our claim that the patch-clamp microchip can be used as an alternate technical platform to the conventional techniques that use fluorescent dyes or a flow cytometer.

The second device is a Field-Effect Transistor (FET) based biosensor used for the detection of biomolecules. The conventional technique, ELISA, is still the gold standard for immunoassays. Most of the modern biosensors have exploited the semi conductive nature of CNT to design a label-free FET based immunosensor (biosensor that exclusively monitors the antibody-antigen interaction). Even though biosensors made out of a single CNT are ideally capable of detecting a single molecule, the fabrication of such devices is challenging. To avoid the fabrication complexity involved with a single CNT based immunosensor, we have developed an FET based biosensor, in which the channel is made out of Carbon Nanotube Thin Film (CNTF). The CNTF channel between the source and drain electrodes is assembled using electrostatic layer-by-layer (LBL) self-assembly. The bio-affinity interaction between Protein A and rabbit IgG is used to model the antibody-antigen interaction, and our initial results show the device is capable of detecting IgG concentrations as low as 1 pg/mL.

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