Ligand Absorption on DNA Duplexes under the Influence of a Fluctuating Medium Changes the Output Signal of a DNA Biosensor

Ligand binding to DNA duplexes in a DNA biosensor was studied in conditions where the number of ligand molecules in the solution fluctuates under the influence of a fluctuating medium (external noise). A multiplicative stochastic differential equation was obtained for the case of low occupancy to describe the time-dependent change in the number of ligands absorbed on DNA duplexes. The average value and relaxation time of the output signal of a DNA biosensor were calculated as functions of ligand absorption on DNA duplexes in a fluctuating medium. Multiplicative noise was shown to decrease the average output signal of a DNA biosensor. Signal deterioration was found to have a threshold; i.e., the signal is not deteriorated at a certain ratio between the absorption parameters and the intensity of external noise. The relaxation time of the output signal of a DNA biosensor was shown to increase with the increasing intensity of external noise.