Norman H. Fontaine

Self-referencing a single waveguide grating sensor in a micron-sized deep flow chamber for label-free biomolecular binding assays

In order to allow the design of increasingly sensitive label-free biosensors, compensation of environmental fluctuations is emerging as the dominant hurdle. The system and technique presented here utilize a unique combination of microfluidics, optical instrumentation, and image processing to provide a reference signal for each label-free biomolecular binding assay. Moreover, this reference signal is generated from the same sensor used to detect the biomolecular binding events. In this manner, the reference signal and the binding signal share nearly all common-mode noise sources (temperature, pressure, vibration, etc.) and their subtraction leaves the purest binding signal possible. Computational fluid dynamic simulations have been used to validate the flow behavior and thermal characteristics of the fluids inside the sensing region. This system has been demonstrated in simple bulk refractive index tests, as well as small molecule (biotin/streptavidin) binding experiments. The ability to perform not only simple binding but also control experiments has been discussed, indicating the wide applicability of the technique.

Optical Biosensors for Monitoring Dynamic Mass Redistribution in Living Cells Mediated by Epidermal Growth Factor Receptor Activation

This paper reported the identification and mechanism of dynamic mass redistribution in living cells mediated by epidermal growth factor receptor (EGFR) activation using resonant waveguide grating (RWG) biosensors. In response to epidermal growth factor (EGF) stimulation, human epidermoid carcinoma A431 cells gave rise to a dynamic response due to dynamic mass redistribution (DMR) in the cells. The DMR response was strongly dependent on cell culture conditions and EGF concentrations. The DMR response of quiescent A431 cells was found to be saturable to the concentration of EGF, and was able to be fully suppressed by a specific and potent EGFR tyrosine kinase inhibitor, AG1478. The effect of various known inhibitors/drugs on the DMR response of quiescent A431 cells clearly showed that the EGF-induced DMR involves the Ras/mitogen-activated protein (MAP) kinase pathway, and mainly proceeds through MEK. The DMR signatures obtained here offer integrated quantitative and dynamic representation of EGFR activation and can be used to screen modulators that can regulate critical targets in both the upstream and the downstream EGFR signaling pathways