NOVEL DIFFERENTIAL SURFACE STRESS SENSOR FOR DETECTION OF DNA HYBRIDIZATION

摘要

A fiber optic coupled interferometric system designed to measure differential surface stress induced by DNA hybridization of (dA)_(30) single-stranded DNA (ssDNA) with complementary (dT)_(30) ssDNA in aqueous environment. The sensing system is amenable to miniaturize into a single MEMS-chip and performed direct detection of nanomechanical response of conformational change and the corresponding charge transduction during molecular adsorption. The static deflection of functionalized sensing cantilever respect to reference cantilever which passivated from additional target molecules converts into a surface stress change for quantitative analysis. The measured surface stress changes were turned to be 40 to 110 mN/m for the concentrations of 0.1 to 1.0 uM of target molecules associated with the dissociation constant (K_d) of 168 nM. X-ray photoelectron spectroscopy (XPS) analysis and noncomplementary experiments were also considered for the validity and reliability of the system.Over the great interests of optical fiber based biosensors, optical beam deflection technique has more scientists' attention due to its simplistic configuration and convenience, but it requires large working space because the resolution relies linearly on the sensing distance between sensitized surface of the cantilever and photodetectors. In contrast, interferometric technique does not depend on the sensing distance although it demands great labors in alignments of sensing components, matching the polarization, and nulling out as much of the background signal as possible. However, miniaturization of the sensor into a single MEMS device with high performance in surface stress measurement is a reasonable compensation for those difficulties in interferometric technique [3]. Detail sensor configuration is illustrated in Figure 1.