Optimization of Sonication Conditions for Nanoparticle Samples

Nanoparticles, although invisible to the naked eye, opens doors to colossal opportunities for improving various aspect of our lives ranging from agriculture to smart products. In biomedical research, the study of nanoparticles is commonly used for drug delivery of pharmaceuticals, proteins and therapeutics. We are developing a new protocol for surface modification of nanoparticles, and this study seeks to identify microcentrifuge tubes that are best suited for sonication, a key step in the process to disperse the nanoparticles. Plastic microcentrifuge tubes that feature a coating to provide ultra-low binding characteristics are used to prevent nanoparticles from sticking to the sides of the tube. However, we have observed particulate formation when samples are sonicated in these tubes. This could lead to a wide set of data to be misinterpreted due to contamination by these particulates. For instance, nanoparticle size and concentration measurements could be skewed because of the presence of these particulates. Therefore, our goal is to investigate the particulate concentration and size produced by tip sonication of water in several brands of microcentrifuge tubes, which are Thermo Scientific^TM Low Retention Microcentrifuge Tubes, Bitoix^TM Low Binding Microcentrifuge Tubes, Eppendorf^TM DNA LoBind Microcentrifuge Tubes, and Eppendorf^TM Protein LoBind Microcentrifuge Tubes. The temperature sensitive nature of polymeric nanoparticle samples often requires the sonication step to be performed at reduced temperature, so the effect of sonication temperature on particulate formation was also investigated. First, we sonicated ultrapure water in each of the brands of tubes, at room temperature, on ice, and on dry ice. We then examined the concentration and size of particulates formed from sonication using NanoSight’s Nanoparticle Tracking Analysis (NTA). It was observed that ThermoFisher^TM tubes produce less contaminant particulates compared to the other three tubes. Additionally, tubes sonicated on dry ice consistently produced less contaminant particulates compared to tubes at other temperatures. Because water sonicated in ThermoFisher^TM tubes on dry ice produced results most comparable to that of fresh ultrapure water, we recommend sonication of nanoparticle samples under these conditions to produce minimal contamination.