Magnetic Microorganisms: Using Chemically Functionalized Magnetic Nanoparticles To Observe and Control Paramecia

With the growing use of nanotechnology in everyday life, there is a developing need to study the fate and potential impact of nanomaterials in the environment. This multiday laboratory experiment introduces students to magnetic nanoparticles (MNPs) and to the uptake of both uncoated and coated MNPs by microorganisms. To highlight the possible uses and potential consequences of the uptake of MNPs, a procedure was developed to "feed" small magnetic particles to paramecia, a process that can be observed using an optical microscope. During extensive laboratory analysis, uptake of the MNPs by these microorganisms was noted with all three species of paramecia examined: Paramecium aurelia, Paramecium bursaria, and Paramecium caudatum. The paramecia clearly ingested the iron oxide MNPs, but the amount of magnetic material per microorganism varied. In some cases, we were able to manipulate the "magnetized" P. aurelia and P. bursaria using a magnetic field. Uptake of uncoated MNPs led to microorganism death within the initial 12-18 h observation window. However, paramecia that ingested MNPs coated with the polymer poly(vinylpyrrolidone) (PVP) were still alive 1 week after ingestion. Included in this report are the procedures for the synthesis of the iron oxide (Fe304) MNPs and their functionalization with PVP, along with an analysis of the chemistry that occurs when uncoated MNPs are present within a cellular environment. Designed for high school students, this engaging experiment integrates chemistry, biology, and physics into the observations of a traditional science laboratory activity, providing a hands-on learning experience.