Precision medicine is the idea where diagnostics and therapeutics are catered to each individual patient to provide personalized care that is optimally effective. For this to be achieved, technologies must exist that extensively examine samples and provide a highly detailed diagnosis for each patient, and processes must exist that can produce personalized drugs that specifically target the patient's illness. Aptamers are short single stranded nucleic acids that bind to their targets with high

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... finity and specificity. Aptamers could make a substantial impact toward the goal of precision medicine. However, one of the main challenges preventing aptamers from reaching their potential is the efficient discovery of new high-affinity aptamers. Currently, aptamer selections are very time consuming and expensive, and often do not result in the discovery of a high-quality aptamer. The ability to reliably select aptamers with high affinity and specificity is paramount to the widespread use of aptamers. Consequently, there is great interest in improving selection technology to obtain high-quality aptamers much more rapidly. Toward this effort, we have developed a Microplate-based Enrichment Device Used for the Selection of Aptamers (MEDUSA) that uses affinity microcolumn chromatography. Its versatile 96-well microplate-based design allows this device to be compatible with downstream plate-based processing in aptamer selections, and it lends itself to automation using existing microplate-based iv liquid-handling systems. MEDUSA is also reconfigurable and is able to operate in serial and/or parallel mode with up to 96 microcolumns. We have demonstrated its use in high-throughput aptamer selections, characterization and optimization of the aptamer selection process, and characterization of previously selected aptamers. More specifically, MEDUSA was used to perform 96 simultaneous tests that determined the optimal target loading on resin to maximize aptamer enrichment for three target proteins, GFP, HSF, and NELF-E. These tests also verified the specificity of aptamers to these three proteins, as well as the non-specific binding of two suspected background binding aptamers. MEDUSA was also used to performed novel RNA aptamer selections to 19 different targets simultaneously. For these selections, a new, more efficient selection strategy was tested that greatly reduced the selection time and reagent consumption. Through the use of MEDUSA, aptamer selections can be optimized and performed in a high-throughput manner, and the success rate of novel aptamer discovery can be drastically improved. In addition to the improvement of novel aptamer discovery, developing valuable applications that use aptamers is of equal importance. An area of study in which aptamers could be of great benefit is cancer. Cancer cells are extremely diverse and contain genetic mutations that allow them to escape the regulatory processes necessary for the healthy function of tissues and organs. Moreover, there are numerous mechanisms for malignancy each with different combinations of genetic mutations, and cancer cells are constantly evolving, which makes cancer treatment difficult with varying levels of efficacy. Aptamers can be selected that bind specifically to cancer cells, and this can be accomplished without any knowledge about the cancer cell surface composition. We have developed a diagnostic device that uses cancer cell-specific aptamers to capture and filter out cancer cells from complex samples, such as blood. Within this same device, the captured cancer v cells are lysed, and their genomic DNA (gDNA) is isolated using a micropillar array. The long strands of gDNA are physically entangled within the array, and remain in the microchannel even under flow. With this device, we have demonstrated the successful capture of human cervical and ovarian cancer cells. In addition, we have developed a custom isothermal amplification technique within the microchannel that amplifies a specific gene of interest for subsequent sequencing and analysis to determine the presence of any genetic mutations. Following the capture of cervical and ovarian cancer cells, we successfully amplified the TP53 gene and sequenced a fragment from this gene. By comparing the sequencing results to the known human TP53 gene sequence, we successfully detected a point mutation in the ovarian cancer cells, whereas the cervical cancer cells contained the wildtype version of this gene fragment. This device can be used to amplify multiple genes consecutively, since the gDNA is retained, so many genes of interest in cancer can be tested in the same small population of cancer cells. Using our device to test patients' cancer cells, a large amount of information can be provided to clinicians about each specific patient that will help them to prescribe the most effective treatment strategy. From the research presented here, aptamers could have a great impact in many areas, and technologies like MEDUSA would help move the field forward by enabling novel aptamers to be successfully discovered rapidly and efficiently. Moreover, aptamers that bind specifically to cancer cells in diagnostics like the one presented here would enable highly informed decisions to be made by clinicians about treatment options. Furthermore, aptamers could also be used in targeted drug delivery and therapies. Therefore, technologies such as these are examples of key steps toward truly personalized and precision medicine.