A nanofluidic biosensor system (200) comprising a bottom substrate (120) and a top substrate (110) between which are defined an input lateral aperture (210), a nanoslit (230) which contains at least one functionalized area (231) and an output lateral aperture (220) or an internal reservoir (221), said biosensor system (200) being adapted to let a solution containing biomolecules (320) enter the input lateral aperture (210) and successively pass through said nanoslit (230) and said output lateral aperture (220) or internal reservoir (221); said biosensor system (200) furthermore comprising a gas evacuation subsystem (150-155) which is located between said nanoslit (230) and the biosensor external environment.