Fischell Department of Bioengineering
Permanent URI for this communityhttp://hdl.handle.net/1903/6626
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Item Surface enhanced Raman spectroscopy technologies and techniques for on-site quantification of chemical and biological analytes(2017) Restaino, Stephen Mario; White, Ian M; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The rapid advancement in mobile devices has illustrated the widening technological gap in health and environmental sensing. Unfortunately, the time and financial burdens imposed by the current central lab model prohibit regular sensing of crucial biological and ecological elements, which can lead to delayed responses and exacerbated conditions. Current portable diagnostic solutions lack the necessary sensitivity or multiplexing potential to address the ever-expanding library of biomarkers. An emerging solution known as surface enhanced Raman spectroscopy (SERS) can provide the sensitivity of current techniques, but with drastically improved multiplexing density. Many existing SERS applications however, require multiple processing steps to introduce samples to the enhancement surface. Practical application of SERS to diagnostics and environmental samples requires more convenient materials and methods to support the broad array of conditions in on-site sensing. In this work, three new methods to apply SERS to portable sensing systems are developed. Specifically, a new SERS diagnostic is presented that details the first implementation of SERS for real-time PCR; we accomplished multiplexed detection of MRSA genes to specifically identify species and drug resistance. Second, we developed a new flexible SERS sponge based on PDMS that provides unprecedented control over sample handling and can readily concentration organic analytes. Finally, we present a novel raster scanning protocol to address the persistent reproducibility issues that has slowed commercialization of new SERS devices. Together, these three techniques advance the development SERS as a practical and portable solution for on-site diagnostics and environmental sensing.Item Bridging the biology-electronics communication gap with redox signaling(2015) Gordonov, Tanya; Bentley, William E; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Electronic and biological systems both have the ability to sense, respond to, and communicate relevant data. This dissertation aims to facilitate communication between the two and create bio-hybrid devices that can process the breadths of both electronic and biological information. We describe the development of novel methods that bridge this bi-directional communication gap through the use of electronically and biologically relevant redox molecules for controlled and quantitative information transfer. Additionally, we demonstrate that the incorporation of biological components onto microelectronic systems can open doors for improved capabilities in a variety of fields. First, we describe the original use of redox molecules to electronically control the activity of an enzyme on a chip. Using biofabrication techniques, we assembled HLPT, a fusion protein which generates the quorum sensing molecule autoinducer-2, on an electrodeposited chitosan film on top of an electrode. This allows the electrode to controllably oxidize the enzyme in situ through a redox mediator, acetosyringone. We successfully showed that activity decrease and bacterial quorum sensing response are proportional to the input charge. To engineer bio-electronic communication with cells, we first aimed for better characterizing an electronic method for measuring cell response. We engineered Escherichia coli (E.coli) cells to respond to autoinducer-2 by producing the β-galactosidase enzyme. We then investigated an existing electrochemical method for detecting β-galactosidase activity by measuring a redox-active product of the cleavage of the added substrate molecule PAPG. In our novel findings, the product, PAP, was found to be produced at a rate that correlated with the standard spectrophotometric method for measuring β-galactosidase, the Miller assay, in both whole live and lysed cells. Conversely, to translate electronic signals to something cells can understand, we used pyocyanin, a redox drug which oxidizes the E.coli SoxR protein and allows transcription from the soxS promoter. We utilized electronic control of ferricyanide, an electron acceptor, to amplify the production of a reporter from soxS. With this novel method, we show that production of reporter depends on the frequency and amplitude of electronic signals, and investigate the method’s metabolic effects. Overall, the work in this dissertation makes strides towards the greater goal of creating multi-functional bio-hybrid devices.Item Bio-templated Substrates for Biosensor Applications(2013) Fu, Angela Li-Hui; Kofinas, Peter; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Nanopatterning of materials is of particular interest for applications in biosensors, microfluidics, and drug delivery devices. In biosensor applications there is a need for rapid, low cost, and durable system for detection. This dissertation aims to investigate methods to pattern nanostructured surfaces using virus particles as templates. The virus species used in these experiments is a cysteine modified tobacco mosaic virus. The first project utilized the lamellar microphase separation of a block copolymer to pattern the virus particles. Although microphase separation of the poly(styrene-b-2-vinylpyridine) (PS-P2VP) into lamellae was confirmed, specificity of the viruses to the gold doped block of the polymer could not be achieved. Single virus particles lay across multiple lamellae and aggregated in side-to-side and head-to-tail arrangements. The second project studied the effect of a surfactant on virus assembly onto a gold chip. The experiments included placing a gold chip in virus solutions with varying triton concentrations (0-0.15%), then plating the virus particles with a metal. Results showed that as the triton concentration in the virus solution increases, the virus density on the surface decreases. The gold coated virus particles were applied to Surface Enhanced Raman Spectroscopy (SERS) detection in the final project. SERS is of interest for biosensor applications due to its rapid detection, low cost, portability, and label-free characteristics. In recent years, it has shown signal enhancement using gold, silver, and copper nanoparticles in solutions and on roughened surfaces. The gold plated virus surfaces were tested as SERS substrates using R6G dye as the analyte. An enhancement factor (EF) of 10^4 was seen in these samples versus the non-SERS substrate. This corresponded to the sample with 0.05% triton in the virus solution which showed the most intersection points between the virus particles and the most uniform coverage of the viruses on the surface. This value is lower than that of previous studies; however, future work may be performed to optimize conditions to achieve the highest signal possible.