Microfluidic Selection of Aptamers towards Applications in Precision Medicine

Precision medicine represents a shift in medicine where large datasets are gathered for massive patient groups to draw correlations between disease cohorts. An individual patient can then be compared to these large datasets to determine the best treatment strategy. While electronic health records and next generation sequencing techniques have enabled much of the early applications for precision medicine, the human genome only represents a fraction of the information present and important to a person’s health. A person’s proteome (peptides and proteins) and glycome (glycans and glycosylation patterns) contain biomarkers that indicate health and disease; however, tools to detect and analyze such biomarkers remain scarce. Thus, precision medicine databases are lacking a major source of phenotypic data due to the absence of available methods to explore these domains, despite the potential of such data to allow further stratification of patients and individualized therapeutic strategies. Available methods to detect non-nucleic acid biomarkers are currently not well suited to address the needs of precision medicine. Mass spectrometry techniques, while capable of generating high throughput data, lack standardization, require extensive preparative steps, and have many sources of errors. Immunoassays rely on antibodies which are time consuming and expensive to produce for newly discovered biomarkers. Aptamers, analogous to antibodies but composed of nucleotides and isolated through in vitro methods, have potential to identify non-nucleic acid biomarkers but methods to isolate aptamers remain labor and resource intensive and time consuming. Recently, microfluidic technology has been applied to the aptamer discovery process to reduce the aptamer development time, while consuming smaller amounts of reagents. Methods have been demonstrated that employ capillary electrophoresis, magnetic mixers, and integrated functional chambers to select aptamers. However, these methods are not yet able to fully integrate the entire aptamer discovery process on a single chip and must rely on off-chip processes to identify aptamers. In this thesis, new approaches for aptamer selection are developed that aim to integrate the entire process for aptamer discovery on a single chip. These approaches are capable of performing efficient aptamer selection and polymerase chain reaction based amplification while utilizing highly efficient bead-based reactions. The approaches use pressure driven flow, electrokinetic flow or a combination of both to transfer aptamer candidates through multiple rounds of affinity selection and PCR amplification within a single microfluidic device. As such, the approaches are capable of isolating aptamer candidates within a day while consuming <500 µg of a target molecule. The utility of the aptamer discovery approach is then demonstrated with examples in precision medicine over a broad spectrum (small molecule to protein) of molecular targets. Seeking to demonstrate the potential of the device to generate probes capable of accessing the human glycome (an emerging source of precision medicine biomarkers), aptamers are isolated against gangliosides GM1, GM3, and GD3, and a glycosylated peptide. Finally, personalized, patient specific aptamers are isolated against a multiple myeloma patient serum sample. The aptamers have high affinity only for the patient derived antibody.