Sensitivity, Specificity and the Hybridization Isotherms of DNA Chips

TL;DR

This paper analyzes how competitive hybridization affects the sensitivity of DNA chips, using modified Langmuir isotherms to quantify the impact on hybridization performance and accuracy in detecting mutations.

Contribution

It introduces a thermodynamic model of hybridization isotherms accounting for electrostatic interactions and competition, enhancing understanding of DNA chip sensitivity limitations.

Findings

Competitive hybridization reduces DNA chip sensitivity.

Hybridization isotherms can be modeled as modified Langmuir curves.

The $c_{50}$ parameter helps quantify hybridization efficiency.

Abstract

Competitve hybridization, at the surface and in the bulk, lowers the sensitivity of DNA chips. Competitive surface hybridization occurs when different targets can hybridize with the same probe. Competitive bulk hybridization takes place when the targets can hybridize with free complementary chains in the solution. The effects of competitive hybridization on the thermodynamically attainable performance of DNA chips are quantified in terms of the hybridization isotherms of the spots. These relate the equilibrium degree of the hybridization to the bulk composition. The hybridization isotherm emerges as a Langmuir isotherm modified for electrostatic interactions within the probe layer. The sensitivity of the assay in equilibrium is directly related to the slope of the isotherm. A simpler description is possible in terms of $c_{50}$s specifying the bulk composition corresponding to 50% hybridization at the surface. The effects of competitive hybridization are important for the quantitative analysis of DNA chip results especially when used to study point mutations.