In this work, aluminum oxide nanoparticles were fabricated by two physical methods: laser ablation in liquid medium and plasma discharge under the action of intensive ultrasonic cavitation. Dynamic light scattering, scanning electron microscopy, and electrokinetic potential measurements were employed to comparatively examine the nanoparticles obtained by both methods. It was found that the synthesized particles had spherical shapes with a size range of about 50-70 nm and relatively narrow particle size distributions and were stable to aggregation and sedimentation. The electrokinetic potential values of the pure particles and the effects of the presence of water-soluble polymer polyethylene glycol were used to examine the surface properties of the nanoparticles. This study demonstrates the effect of ultrasonic action on particle surface activity.