Novel nanomaterials are actively sought by chemists, biologists and engineers for a variety of applications. Biosensor platforms used for diagnostic purposes would benefit greatly from the development of new electrochemical or optical transducer substrates. This dissertation is a detailed account of the research effort to develop novel nanotechnology platforms for advanced electrochemical and optical detection of biological molecules. Specifically, my goal was to design and fabricate operationally simple yet inexpensive new electrochemical and optical biosensors that are highly selective and sensitive.
The first section will cover the early work in the development of a porous polyelectrolyte interfaces with well-defined structure and electrochemical behavior using electrochemical surface plasmon resonance (ESPR) spectroscopy. This early work will also cover the application of the unobstructed electron transfer on porous polyelectrolyte nanostructures for the detection of poliovirus type 1 (PV1) using electrochemical enzymatic amplification. The electrochemical behavior of this sensor for whole viral particles is characterized using an enzymatic sandwich based immunoassay, with the final antibodies tagged with an ultra sensitive electrochemically active enzyme. Two important factors that make this sensor design innovative is the high loading capacity within a 3-D nano-assembly and the unhindered fast electron transfer through the nanofilm to the electrode surface. The enzymatic amplification scheme is an alkaline phosphatase (ALP) system, which has shown superb properties to enhance the redox current of electroactive species in the presence of aminophenyl phosphate (APP).
The majority of the thesis will focus on the electrospinning technique and how electrospun nanofibers can be used to create novel optical transducer platforms. Electrospinning is a polymer processing technique used to create continuous fibers with diameters ranging from a few nanometers to micrometers, and is ideal for encapsulating functional units, especially fluorescent and optical receptors, for biosensing applications. This section of the thesis will be divided into three specific parts. The first part will focus on a solid-state reusable and porous nanofiber-based optical (fluorescent) transducer for detecting proteins using an array of fluorescent dendrimers. The second part will cover the details of an optical (colorimetric and fluorescent) transducer using electrospun nanofibers doped with the conjugated polymer polydiacetylene (PDA) for the detection of volatile organic compounds (VOCs) and proteins. Lastly, the third part will describe the development of 2D-silica nanofiber thin films doped with gold nanoparticles, their enhanced optical properties, and the potential use in future sensor technology.
