Optical Detection for Polymer Based Bio-Sensor

In this thesis, an optofluidic chip was used for detection of fluorescently labeled
streptavidin. The chip was fabricated from thiol-ene polymer, and incorporates
an embedded waveguide in direct contact with the sample fluid.
By using off-stoichiometric thiol-ene mixtures, the polymer was tailored to feature an excess of functional surface groups, enabling one-step site-specific functionalization with the binding molecule biotin.
Utilizing the high anity bond between biotin and streptavidin, fluorescently labeled streptavidin was immobilized on the waveguide surface, and excited by the evanescent field from the guided light in the waveguide. The biotin functionalization was optimized to provide the highest fluorescent signal,
and the resulting calibration curve, revealed a linear correlation between streptavidin concentration and fluorescence intensity, with a limit of detection of 0.2 M.
Due to the lack of information on the optical properties of thiol-ene polymers,
these were initially investigate to evaluate the use of thiol-ene in optofluidic chips.
The refractive index was determined by refractive index matching, and shown to
stay constant with a value of 1.57 for thiol-ene mixtures ranging from 150% excess alkene groups to 90% excess thiol groups, even though the mechanical properties and surface chemistry change considerably during this range. Thus, thiol-ene have a high refractive index compared to other lab-on-a-chip materials, which combined with its high optical transparency, make thiol-ene a promising material for optofluidic devices.