Date of Award

8-2008

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Biological Engineering

Advisor

Michael Mason

Second Committee Member

Douglas Bousfield

Third Committee Member

David Neivandt

Abstract

The need for rapid detection of pathogenic or viral DNA molecules as protective measures in health and public safety has led to the development of many new methods for biomolecular detection. Currently being developed is a micro-biosensor system on paper-based substrates feasible for wide-spread use for the rapid detection of target DNA sequences. Deposition of the system onto the substrates will be performed using inkjet technology. The proposed biosensor includes a peptide nucleic acid (PNA)-gold nanoparticle conjugated system which utilizes the tunable optical and electrical properties of gold nanoparticles as the sensitive detection mechanism. PNA, a nucleic acid analog, is being synthesized for use as the DNA recognition sequence due to its high affinity and specificity for binding of only complete complimentary DNA sequences. In this system, the binding of a target DNA sequence to the PNA probe sequence releases a linked PNA:nanoparticle conjugate. The released nanoparticles are then selectively focused using electrophoresis and dielectrophoresis under a non-uniform electric field. Concentration of these nanoparticles then allows for optical and electrical detection at ultra-low quantities. The primary objectives of this thesis research was the synthesis of modified PNA sequences capable of target DNA hybridization, functionalization of nanoparticle:PNA conjugates, and to test the efficiency of the proposed PNA:nanoparticle recognition system. This research demonstrates the successful design and implementation of the proposed recognition system. Hybridization of target DNA molecules to synthesized probe sequences led to the subsequent release of functionalized nanoparticles to be utilized in the sensitive detection method. Also in this work, a novel silver nanoparticle suspension was developed and investigated for use in ambient-cured conducting ink formulations for deposition of electrode systems to be used in the systems. Although these conducting inks were not highly conductive with curing under ambient conditions, they were found to be highly conductive at moderate curing temperatures suitable for application onto paper substrates. In addition, long-term stability and controllable physical dimensions of the developed nanoparticles may lead to other potential uses for such suspensions in other chemical, biochemical, and optical sensors.

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