Adsorption of polyethyleneimine characterized by spectroscopic ellipsometry

Abstract Polyethyleneimine (PEI) is a well known gene transfection reagent that has been extensively studied in the pass two decades. In this work, we have explored its physiochemical properties by examining its interfacial absorption at the hydrophilic silicon oxide/water interface and its ability to immobilize bioactive DNA under physiological conditions. Its surface excess was found to show a gradual increase with pH between pH 3 and pH 10. At pH 7 the surface absorbed amount increased with increasing salt concentaration. The amount of DNA immobilzed was found to be controlled by the charge ratio between PEI and DNA under these physiological conditions. Thus, the amount of bioactive DNA immobilized can be tuned by badjusting the amount of PEI preadsorbed. This study provides useful information for fabrication of biosensors and gene chips via interfacial adsorption.