INTERFACIAL NUCLEIC-ACID HYBRIDIZATION STUDIED BY RANDOM PRIMER P-32 LABELING AND LIQUID-PHASE ACOUSTIC NETWORK ANALYSIS

Single-strand DNA labeled with P-32 by the random primer method has been adsorbed to the surface of palladium electrodes of thickness shear-mode acoustic wave sensors and nylon membranes under various solution conditions. The mass of nucleic acid attached to these substrates has been quantified by scintillation counting and phosphor image analysis. Measurement of the mass on sensors by acoustic wave sensor response obtained in the gas phase does not correlate with the values given by radiochemical labeling. Hybridization of cDNA to the single-strand species on the sensor surface has also been determined by the P-32 technique. The added mass has been correlated with real-time changes in the series resonant frequency obtained in situ from acoustic network analysis. The value for the alteration of the frequency is 18 times that predicted by the Sauerbrey expression. This result is ascribed to changes in interfacial viscosity originating from duplex formation. The limit of detection of the unoptimized technique is 2 ng of on-surface added nucleic acid. In addition to the series resonant frequency, other parameters from network analysis, such as the motional resistance, have been measured on a real-time basis during interfacial hybridization.