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Label-Free Imaging

Because photonic crystal biosensors are designed to prevent lateral propagation of light, each individual location on a photonic crystal biosensor surface will reflect a wavelength that is dependent on the density of adsorbed biomolecules or cells that is independent of it neighboring regions.  Therefore, a large continuous photonic crystal surface provides a huge number of independent sensor regions that can be probed with the right instrument.  The BIND Scanner Imaging Instrument is capable of generating spatial maps of a photonic crystal surface resonant wavelength with spatial resolution of as little as 4x4 mm2 per pixel.  This capability is useful for high throughput label-free assays in the form of microarray spots, imaging individual cancer cells, and detecting the biochemical binding taking place within many microfluidic channels in parallel.  By taking multiple images over a period of time, we can use the label-free imaging capability to observe cell proliferation, apoptosis, wound healing, and chemotaxis. 

Figure 1. Schematic diagram of a photonic crystal imaging detection instrument capable of measuring the peak reflected resonant wavelength from a photonic crystal surface with pixel resolution as low as 4 microns.

Figure 2.  Peak wavelength value image of a photonic crystal biosensor surface in which human breast cancer cell attachment results in locally elevated reflected wavelength.  The method allows monitoring of cell attachment to the biosensor surface with single cell resolution, and time-course monitoring of cell proliferation, chemotaxis, apoptosis, and wound healing.

References:

1. "A New Method for Label-Free Imaging of Biomolecular Interactions," P. Li, B. Lin, J. Gerstenmaier, and B.T. Cunningham, Sensors and Actuators B, Vol. 99, p. 6-13, (2004).

2. "A label-free photonic crystal biosensor imaging method for detection of cancer cell cytotoxicity and proliferation," L. Chan, S. Gosangari, K. Watkin, and B.T. Cunningham,  Apoptosis, Vol. 12, No, 6, p. 1061-1068, 2007.

3. "Label-free imaging of cancer cells using photonic crystal biosensors and application to cytotoxicity screening of a natural compound library," L.L. Chan, S. Gosangari, K.L. Watkin, and B.T. Cunningham, Sensors and Actuators B, Accepted, October, 2007.

4. "Single-step fabrication of photonic crystal biosensors with polymer microfluidic channels by a replica molding process," C.J. Choi and B.T. Cunningham, Lab-On-A-Chip, Vol. 6, p. 1373-1380, 2006.