Harnessing the power of light in nanopore sensing and biomedical 3D printing applications
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Light is a ubiquitous form of energy used in many disciplines and industry sectors. Biomedical applications that harness the distinctive properties of light are rapidly growing in many areas, such as medical imaging, radiation therapy, and pathogen identification. This dissertation investigates two unique systems, in which the specific characteristics of light enable the single-molecule detection of fluorescently labeled polypeptides and the 3D printing of hydrogel-based cellular scaffolds and nasopharyngeal swabs. The first half of the dissertation presents a novel solid-state nanopore sensor that employs multicolor fluorescence detection to facilitate the discrimination of two polypeptides at a single-molecule level. Solid-state nanopore devices drilled in locally supported, free-standing TiO2 membranes exhibit exceptionally low photoluminescence in the visible spectral range under simultaneous excitation of multiple lasers. The significant reduction of the optical signal-to-background ratio enables the differentiation of a single fluorophore between two polypeptide populations, thus introducing future possibilities for optical based identification of more complex peptides and proteins in nanopores. The second half of the dissertation focuses on an emerging micro- and nano-fabrication technique based on direct laser writing (DLW) via two-photon polymerization. An innovative two-photon DLW-patterned hydrogel system to modulate cell alignment and adhesion is reported. Variations in the laser writing speed in the fabrication process lead to polymerized structures with distinctive stiff and soft components, without changing the photoresist. On cell-adhesive hydrogels, the width of the alternating stiff and soft patterns dictates the degree of F-actin alignment in hMSCs. The addition of a second hydrogel with cell-repellent properties enables the selective adhesion and alignment of hMSCs on microstructures with both flat and curved features. Lastly, the development of a novel 3D-printed nasopharyngeal test swab during the COVID-19 pandemic is presented. The optimized swab designs demonstrate non-inferior mechanical stability and testing accuracy compared to existing commercial test swabs. In summary, significant progress has been made in both nanopore-based optical sensing and DLW of microscale cellular scaffolds. Future work will enhance existing technologies in the detection of complex peptides and proteins and the fabrication of functional, biocompatible, and dissolvable 3D-printed scaffolds to enable their clinical applications in protein molecular biomarker diagnostics and stem-cell-derived regenerative tissues for the diagnosis and treatment of a wide range of diseases.