Engineering of plasmonic excitations for hand-held and ultra-sensitive biosensors
Cetin, Arif Engin
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Early detection and effective diagnosis are important for disease screening and preventing epidemics. Recently, optical biosensors have attracted significant attention, as they are very powerful detection and analysis tools that have variety of applications in homeland security, public and global healthcare, biomedical research and pharmacology. However, most of these biosensors are time-consuming, require costly chemical procedures and bulky instrumentation, and need advanced medical infrastructures with trained laboratory professionals. In order to address these needs, recently lensfree computational on-chip imaging techniques have been introduced to eliminate the need for bulky and costly optical components. However, this technology is limited by the size of the analytes as it uses a lensfree computational technique insufficient for detecting biomolecules down to nm-scale. In order to provide highly sensitive and massively multiplexed detection of biomolecular binding events, fluorescent imaging and surface plasmon resonance (SPR) based platforms are the most favored. However, SPR sensors are limited due to the alignment sensitive prism coupling scheme and bulky instrumentation while the fluorescence imaging suffers from quantitative and qualitative drawbacks of the labeling steps. This thesis focuses on the unique integration of lensfree telemedicine technology and nanostructured plasmonic chip technology to realize ultra-sensitive and label-free biosensing in a high-throughput and massively multiplexed manner for field-settings. Toward this aim, we introduce a handheld on-chip biosensing technology that employs plasmonic microarrays coupled with a lensfree computational imaging system. Employing a sensitive plasmonic array design that is combined with lensfree computational imaging, we demonstrate label-free and quantitative detection of biomolecules with a protein layer thickness down to 3 nm. Integrating large-scale plasmonic microarrays, our platform enables the simultaneous detection of protein mono- and bilayers on the same platform over a wide range of biomolecule concentrations. In this plasmonic device, we also monitor binding dynamics of protein complexes as a function of time by integrating it with microfluidics. Plasmonic antennas utilized in our lensfree platform, supporting very sharp and sensitive spectral feature as well as easily accessible large local electromagnetic fields, are highly advantageous for biosensing applications as they enable stronger interaction between surface waves and biological molecules on the sensing chip.
Thesis (Ph.D.)--Boston University