2012 Research Experience for Undergrads
Characterization of nanoplastic marine debris using flow cytometry
As a JISAO 2012 summer intern, I had the pleasure of working with Dr. Giora Proskurowski, Dr. Joel Baker, Julie Masura and Jarred Swalwell studying nanoplastic marine debris. Nanoplastics are plastic particles that are smaller than 300 microns in length, and have two suspected sources. One potential source of nanoplastic in the ocean is from the breaking up of larger pieces. The second and more surprising cause is from consumer products. Many items such as face washes and toothpastes contain polyethylene as an abrasive scrubber, and there is speculation that the nanoplastics in these products are not being filtered out by wastewater treatment plants after being washed down shower and sink drains.
Since these plastic pieces are too small to be seen, much less counted, there is currently no existing method to characterize the amount of nanoplastic marine debris in the ocean. My project involved developing a method to do this using a flow cytometer. A flow cytometer is an instrument that uses the forward scatter, side scatter and fluorescence of a population of particles to determine the approximate size and count. This method can be applied to phytoplankton because of their small size and the fluorescence of chlorophyll. However, there are multiple challenges to studying nanoplastics in a flow cytometer. Plastic naturally floats, so it does not disperse well in standard samples. Also, plastic does not fluoresce, making it virtually invisible in the cytometer.
To solve these problems, I used a sonicator to disperse the particles for a long enough time frame to be tested. I also stained the particles using Oil Red O dye. The same method used to test the standards was then applied to solutions of consumer products that contain polyethylene. It was found that the method can not only be used to identify plastics in a cytometer, but it can also find nanoplastics in certain face washes and toothpastes.
In addition to my work using the flow cytometer, I spent one day per week at the University of Washington-Tacoma. There, I tested larger pieces of plastics—called microplastics—using an FTIR-ATR. This instrument gives the spectra of the sample, and from there the type of plastic can be identified. A majority of samples that I tested were either high-density or low-density polyethylene.
While in Seattle, I got to explore downtown, see Snoqualmie Falls and go whale watching! I also went to Seafair Festival and spent a weekend in Victoria, British Columbia. But none of that compared to the adventure that awaited me aboard the tall ship Adventuress as I sailed the San Juan Islands with Sound Experience! While sailing, I had the opportunity to mentor young women in the sciences and share with them some of the work I did this summer.
Overall, the JISAO summer internship was an incredible experience. I had a ton of fun, and I am walking away a better scientist. Thank you Jed Thompson, my mentors, and the rest of the JISAO group for making this possible!
Click on poster for full-size image [PDF]