Aim. The research was aimed to determine the optimal working conditions of SPR biosensor system for the detection of DNA sequences of the hybrid gene BCR-ABL under which it is possible to enhance its sensor signal using gold nanoparticles modified with probe oligonucleotides and surface blocking molecules. Conclusions. The use of the developed AuNPs led to the shift of linear operating range of the proposed biosensor system to low concentrations by two orders of magnitude, which makes it more perspective for analyzing biological samples prior to their PCR treatment.