An electrophoresis approach with online thermal lens detection to monitoring DNA surface coatings on gold nanoparticles

•A novel gel electrophoresis with thermal lens detection biosensor was proposed.•Extremely small differences in the electrophoretic mobility of the particles can be resolved.•The developed sensor is highly sensitive and possesses a detection limit 0.023 nM.•The system enables acquiring results in remarkably shorter running times.•The presented approach can be of broad interest for effectively separating various biomolecules.