Dispersion Method for Safety Research on Manufactured Nanomaterials

Nanomaterials tend to agglomerate in aqueous media, resulting in inaccurate safetyassessment of the biological response to these substances. The present study searched forsuitable dispersion methods for the preparation of nanomaterial suspensions. Titaniumdioxide (TiO₂) and zinc oxide (ZnO) nanoparticles were dispersed in abiocompatible dispersion medium by direct probe-type sonicator and indirect cup-typesonicator. Size characterization was completed using dynamic light scattering andtransmission electron microscopy. A series of dispersion time and output power, as well astwo different particle concentrations were tested. Microscopic contamination of metaltitanium that broke away from the tip of the probe into the suspension was found. Size ofagglomerated nanoparticles decreased with increase in sonication time or output power.Particle concentration did not show obvious effect on size distribution of TiO₂nanoparticles, while significant reduction of secondary diameter of ZnO was observed athigher concentration. A practicable protocol was then adopted and sizes of well-dispersednanoparticles increased by less than 10% at 7 d after sonication. Multi-walled carbonnanotubes were also well dispersed by the same protocol. The cup-type sonicator might be auseful alternative to the traditional bath-type sonicator or probe-type sonicator based onits effective energy delivery and assurance of suspension purity.