In this study, interaction of produced magnetic fluidwith single stranded DNA was investigated by using designed magneto-opticallinear dichroism (MOLD) measurement system. Fe3O4 nanoparticles,produced by using co-precipitation method were characterized by means ofstructure, magnetic, and size distribution. These nanoparticles coated witholeic acid and Tetramethylammonium (TMA) in water and ethanol. Change ofthe linear dichroism property of fluid under applied magnetic field wasobserved due to the interaction of produced magnetic fluid with single strandedDNA. Obtained results were shown that it is possible to develop a single strandedDNA sensor by using its interaction with magnetic liquid and MOLD effect.