An analytical model for nanomechanical behavior of microcantilever-DNA chip

摘要

The paper is devoted to formulating an analytical relation between various biomolecular interactions during the process of label-free DNA-detection and changes in surface stress, which is widely accepted as the origin of nanomechanical motion of a microcantilever-DNA chip. First, considering electrostatic interactions between neighboring strands, hydration forces between DNA molecules and hydrogen bonding networks in water, conformational entropy of DNA chains, and mechanical energy of non-biolayers, the energy potential of a DNA chip and its first-order approximate expression are formulated. Second, the analytical expression for surface stress of a DNA chip is given by the minimum principle of energy. Third, the effects of grafting density and salt concentration on surface stress are investigated. Numerical results show that surface stress is a strong function of grafting density, which is in agreement with Stachowiak's experimental results. And, comparison of first-order and two-order predictions for surface stress is discussed.