The interaction of phenosafranine （PSF） with a glycosaminoglycans of heparin （Hep） in aqueous solution has been characterized by UV-Vis absorption spectrophotometry and cyclic voltammetry in pH 1.5 Britton-Robinson （B-R） buffer solution. The addition of Hep caused decrease of the absorbance of PSF at 532 nm and the redox peak current of PSF. The study showed that an supramolecular complex of PSF-Hep was formed because of the electrostatic attraction of negatively charged Hep with the positively charged PSF, which resulted in the decrease of the equilibrium concentration of PSF in solutions, and the decrease of the absorbance or the peak current of PSF. The stoichiometry of the Hep/PSF complex was further calculated by voltammetric data with the result of 1：1 complex.
A NOS gene electrochemical biosensor was prepared by covalently immobilizing of NOS ssDNA sequence on the mercaptoacetic acid monolayer self-assembled gold electrode with the help of N-（3-dimethylaminopropyl）-N’-ethylcarbodiimide hydrochloride（EDC）and N-hydroxysuccinimide（NHS）.By using methylene blue as the electrochemical indicator,the increase of cathodic peak current was in linear with the concentration of complementary ssDNA in the concentration range of 5.0×10-8 1.0×10-4 mol/L with the linear regression equation as ΔI pc=1.10lgc+8.25（n=8,γ=0.998 5）and the detection limit as 3.60×10-8 mol/L（3σ）.
