A novel method of colorimetric assay for determining cis-Pt (cis-diammino-dichloroplatinum Ⅱ) was found by the binding affinities between cis-Pt and DNA based on the change of surface plasmon resonance band of gold nanoparticles. The red-shift of the maximum band of the surface plasmon resonance band of gold nanoparticles increased linearly with the logarithm of the cis-Pt concentration from 40 to 2000 nmol/L and the detection limit is 40 nmol/L when the concentration of gold nanoparticles is 4 nmol/L. The colorimetric readout can be visualised with the naked eyes.
