Barley protoplast was immobilized on poly(dially dimethylammonium) (PDADMAC) modified gold electrode via the electrostatic attraction between the positively charged amine groups of PDADMAC and the negatively charged barley protoplast. STM image reveals that PDADMAC/Au(111) surface displays a nano organized dot(4-6 nm) array structure. The processes of the PDADMAC adsorption and of the barley protoplast immobilization were monitored from the in situ QCM frequency change. The effects of the adsorbed mass and of the density and viscosity of medium on the frequency change of QCM were discussed, respectively. The QCM result shows that the thickness of the adsorbed PDADMAC layer is 2.4 nm
