Digital Electrical DNA Sensing
Sammanfattning: Molecule detection is a workhorse in life sciences and medicine, for example in cancer diagnosis and virus and bacterial detection. DNA analysis can provide vital information about the state of a host organism and its medical and health condition. A central challenge in DNA sensing lays in obtaining the following key detection characteristics in a single device: low limit of detection, small sample volume, high specificity, quantification, rapid time-to-result at a low cost.Here we investigate whether direct electrical DNA sensing in a miniaturized detector can enable such performance. The detector consists of a gold-coated thin porous membrane, functionalized with oligonucleotides receptors, that is sandwiched between two off-stoichiometric thiol-ene-epoxy layers. The device works as follows. First, target DNA in the sample is specifically recognized by padlock probe hybridization and ligation. Second, the target-receptor circular molecules are amplified by rolling circle amplification (RCA), generating long ssDNA concatemers (RCP). Third, the RCPs are stretched through the membrane pores. Fourth, DNA metallization was used to form the gold nanowires bridging both sides of membrane pores after gold enhancement, which results in a conductive path that is measured with a simple resistance measurement. The thesis describes the engineering technology that enables low LoD detection of ssDNA using a digital measurement and details the development and optimization of the detector fabrication and operation, including structural design, materials, and microfluidic operation. We demonstrated a detector with sub-aM LoD, high specificity and simple operation in a miniaturized and uncomplicated format. Furthermore, the thesis studies the long-term liquid storage in nL scale well arrays fabricated in off-stoichiometric thiol-ene (OSTE). We demonstrated liquid storage with < 10 % loss of stored PBS buffer for 33 days and the on-demand electrically controlled liquid release.The thesis presents the potential of a combination DNA detector with the method of liquid storage. Combining the on-chip liquid storage and DNA detection methods could provide a powerful alternative to conventional bio-detectors used in molecular diagnostics, and improved performance in multiplexed point-of-care sensing of (ultra-low abundant) biomolecules.
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