The present invention refers to a method of determining protein-nucleic acid interaction. The method comprises mixing a protein with a sample comprising a nucleic acid which is suspected to interact with the protein to form a first mixture. The first mixture can be incubated to allow interaction between the protein and nucleic acid. Metallic nanoparticles are added to the first mixture to obtain a second mixture. An electrolyte is added to the first or second mixture to determine the protein-nucleic acid interaction. The present invention also refers to a kit for determining protein-nucleic acid interaction. The kit comprises a protein capable of interacting with a nucleic acid or a nucleic acid capable of interacting with a protein, and at least one type of metallic nanoparticle.