Liquid crystal (LC) orientation responds sensitively to biomolecules and thus it has been employed as a transducer for label-free bio-detection. Nevertheless, most of current LC based biodetection methods require microscopes equipped with cross polarizers for visualization, making it difficult to integrate these methods with portable biosensors for point-of-care applications. Herein, we introduce a LC based protein detection methods which enables naked-eye observation of the signal without requirement for any optical instrumentation. This method is based on amplification of weak interference color arisen from parallel protein lines by using a thin layer of LC. Because LC is birefringent, it forms a diffraction grating with periodical refractive indices. This diffraction grating generates strong interference color in ambient light conditions (As shown on the Figure). As a proof of concept, we employ this method for naked-eye detection of surface patterned immunoglobulin (IgG). Moreover, when coupled with affinity contact printing, this method enables the immunosensing of anti-IgG with a detection limit of ~ 1 �g/ml. This LC based detection method is generic for other LC-responsive biomolecules, such as DNA and lipids. Its simplicity and miniaturization can lead to the development of portable, label free and low-cost biosensors for point-of-care diagnostics.

Amplification of interference color by using liquid crystal for protein detection

247th National Meeting (2014)

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