DNA known as a carrier of genetic information has been widely used in the field of nanomaterial sciences. In particular, DNA combined with nanotechnology is great importance for development of various effective biomedical applications. Here, I will talk about material design of gold nanoparticles modified with high surface-density of double-stranded DNA and their colloidal surface properties that can show a drastic color change owing to a band shift of the surface plasmon resonance. This behavior allows us to develop potential applications to colorimetric gene diagnostics of human related-samples and drug screenings of antitumor agents. During the lecture, the students with diverse backgrounds are also expected to gain an understanding of interdisciplinary research of chemical engineering and biomedical science.