A method an system is disclosed for characterizing DNA and/or RNA duplexes. The biosensing device comprises a heating element using a power and being suitable for providing thermal denaturation of target DNA and/or RNA bioparticles, a sample holder adapted for receiving a biocompatible substrate having a functionalized surface which is coated with probe DNA and/or RNA whereto target DNA and/or RNA duplexes can be attached, the sample holder further being adapted for exposing the biocompatible substrate at one side to the heating element, a first temperature sensing element for sensing a temperature at the side where the biocompatible substrate can be exposed to the heating element and a second temperature sensing element for sensing a temperature at the side opposite thereto with respect to the biocompatible substrate. The device also comprises a processing means programmed for calculating at least one heat transfer resistivity value based on temperature values obtained with the first temperature sensing element and the second temperature sensing element and the power for the heating element, for deriving a characteristic of the target DNA and/or RNA bioparticles from said heat transfer resistivity value.