Detection of Label-Free Biomolecules by Wavelength-Scanning Reflective Interferometric Sensing

Introduction Studies in sensing of biomolecules such as DNAs, RNAs and bacterial pathogens have grown rapidly and triggered many applications in biological research. Previously reported techniques have shown great significance in the area of medical tests, environmental monitoring and medicine (Cooper, 2002). Sensitivity and selectivity of the detection have been improved by fluorescent tagging of molecules in the analyte samples (Chee et.al.,1996; Iyer et.al., 1999) but this process is expensive and time-consuming. Additionally, the detector and the imaging system that are required by the current fluorescent readout schemes are complicated and expensive. Further studies focus efforts on two aspects: avoiding modification of the analyte to simplify the chemistry and reducing the cost to make easily portable readout systems. Ellipsometric approaches (Jin et.al.,1995; Landry & Zhu, 2004), Interferometric methods (Lin et.al.,1997; Jenison et.al.,2000;Chan et.al., 2001; Pan & Rothberg,2003) and Surface Plasmon Resonance (Knoll, 1998; Nelson et.al.,2001) still require relatively complex detection systems. Simple chemistry and inexpensive detection, while maintaining the high sensitivity and selectivity, continue to be goals for developing an efficient biomolecular sensing technique.