ABSTRACT
A novel optical biosensor using a one-dimensional photonic crystal structure in a total-internal-reflection geometry (PC-TIR) is presented and investigated for label-free biosensing applications. This simple configuration forms a micro Fabry-Perot resonator in the top layer which provides a narrow optical resonance to enable label-free, highly sensitive measurements for the presence of analytes on the sensing surface or the refractive index change of the surrounding medium in the enhanced evanescent field; and at the same time it employs an open sensing surface for real-time biomolecular binding detection. The high sensitivity of the sensor was experimentally demonstrated by bulk solvent refractive index changes, ultrathin molecular films adsorbed on the sensing surface, and real-time analytes binding, measuring both the spectral shift of the photonic crystal resonance and the change of the intensity ratio in a differential reflectance measurement. Detection limits of 7x10(-8) RIU for bulk solvent refractive index, 6x10(-5) nm for molecular layer thickness and 24 fg/mm(2) for mass density were obtained, which represent a significant improvement relative to state-of-the-art surface-plasmon-resonance (SPR)-based systems. The PC-TIR sensor is thus seen to be a promising technology platform for high sensitivity and accurate biomolecular detection.
ABSTRACT
The study of complex biological systems requires methods to perturb the system in complex yet controlled ways to elucidate mechanisms and dynamic interactions, and to recreate in vivo conditions in flexible in vitro set-ups. This paper reviews recent advances in the use of micro- and nanotechnologies in the study of complex biological systems and the advantages they provide in these two areas. Particularly useful for controlling the chemical and mechanical microenvironments of cells is a set of techniques called soft lithography, whereby elastomeric materials are used to transfer and generate micro- and nanoscale patterns. Examples of some of the capabilities of soft lithography include the use of elastomeric stamps to generate micropatterns of protein and the use of elastomeric channels to localize chemicals with subcellular spatial resolutions. These types of biological micro- and nanotechnologies combined with mathematical modeling will propel our understandings of cellular and subcellular physiology to new heights.
