Professor Miller-Jensen and her lab members made a presentation on microfluidic devices for high school students in the SCHOLAR program. They asked me to observe and make notes on the presentation so they could improve it for next year. I actually assumed the presentation started at 9:30 am because of a sign I saw outside the presentation room, but it was really at 11:15 am. During that time gap, I helped Laura, a research assistant, and Victor Bass, a graduate student, prepare pH solutions for the high schoolers to test their devices on. We prepared four solutions, one with a pH of 4, two with a pH of 7, and one with a pH of 10. I used a pipette to put the solutions in containers labeled A, B, C, and D, one container for each solution. The presentation was good, the students seemed somewhat interested in microfluidics. Some even asked if they could intern at Professor Miller-Jensen's lab since I was interning here. The professor also had the students do a hands-on activity where they make their own microfluidic device using filter paper and crayons. Students would draw a path with a crayon and melt the wax to create a channel so the fluids cannot escape.
I asked Victor about the goal of my internship, and he said that he was mainly teaching me technical skills so that I know how to operate and conduct myself in a lab in preparation for the future. He also wants me to make a passive-flow microfluidic device and test its efficacy for another experiment which will examine how heterogeneity affects cell-to-cell communication and the production of cytokines when a cell from the immune system (T Cell) is infected by HIV.
I made more devices by producing a PDMS solution and making molds of the passive-flow device. Victor let me do all the work by myself; he just watched me do it so I would not make a mistake. I polymerized a chemical by mixing it with a curing agent in a 1:10 ratio (25 g of chemical, 2.5 g of curing agent). After, I poured the PDMS into a container in the hood and used a centrifuge to get rid of the bubbles in the substance. I had to make sure the centrifuge was balanced by placing a container filled with water that was the same amount as my PDMS so it would not tip over. After using the centrifuge, I cleaned out the passive-flow device to make sure there was not any extra residue of PDMS present, otherwise it would mess up the device. I poured the PDMS into the container holding the passive-flow device and baked the cast in an 80˚C oven for 2+ hours. While the mold baked in the oven, Victor and I split my cells (J65C 6.6 and 4.4 -- just labels for the cells) in a 1:4 ratio (1 mL of cells: 4 mL of whole solution) to make sure they don't overpopulate. In each container, there was 8 mL of solution with 1 million cells per mL in the solution. I split the cells by pipetting the cells back and forth in the container to get rid of any clumps in the cell populations. I then placed only 2 mL of cells in each container and took out 6 mL. I dumped the 6 mL from 4.4 into a bleach container to kill the cells, but I put 6 mL of cells from 6.6 into a container so we could run them through the devices we already made. I replaced the 6 mL I removed from the containers with 6 mL of RPMI, which is the medium we use to grow our cells in. We then put the cell containers in an incubator so they could grow. We put the sample of cells from 6.6 in a centrifuge so that we could get a pellet of cells at the bottom of the container. This was so we could remove the medium from the sample and get 5 million cells in 1 mL of media (5 million cells is the optimal amount of cells to be tested in a microfluidic device). Victor then used a pipette to place the cells into a cell strainer to ensure there were no clumps of cells, otherwise the traps would not work well. Victor and I took two of the devices we made last week and cut out holes for the outlet and inlet so cells can flow through the channel. We then treated the devices and microscope slides with oxygen plasma in the Plasma Etch so we could attach the devices to the slides and make the devices hydrophilic so fluid can flow through them. After securing the devices, Victor ran distilled water through the devices to ensure flow could occur and hydrophilicity remains in channel. Using a pipette, Victor and I removed the water from our devices and placed 50 microL of our cell samples into the devices. We then observed the flow of the cells in the device under a microscope.
I talked with Professor Miller-Jensen about my view on the presentation and any notes or suggestions I had for her. My main suggestions were to go more into detail and explain some concepts further since I believed many of the students were confused at some of the content. I also recommended making visuals to help students picture how a microfluidic device works/flows so students can understand laminar flow better. The professor told me about how she wished there could be a workshop so she could explain the concepts that go with microfluidics more in detail and have more hands-on activities for students. It would definitely be a good idea; however, I am unsure if students will actually be willing to go to a workshop for multiple days to learn about microfluidic devices.
I made more PDMS molds of microfluidic devices with Laura. Instead of making molds of the passive-flow device, we made some for the well chip and the flow-patterning device. Still unsure of how they function, so I need to learn about that. I followed the same procedure as I did with Victor on Tuesday, July 12th. Laura and I punched holes in the devices for the inlets and outlets, and we cleaned the devices using tape to get rid of large sediment, as well as cleaning solutions and methods such as ethanol and sonication. Sonication is the use of sound waves to vibrate substances, and in this case, it is used to clean the devices and to get rid of extra PDMS on the device.
There was a lab meeting on the discussion of a paper on the microbiome in the human gut and how a species of bacteria (B. dorei) with LPS (lipopolysaccharide) can inhibit immune education (immune system adapting to illnesses early on -- hygiene hypothesis). Laura also discussed her progress on her project of studying cell signaling. I did not understand a thing from the presentations. I still need to learn more about science and the project since I only have high school biology as my background. So far, all I was taught in lab was technical skills
Victor and Laura did not have much planned for me today. The professor actually has Victor working on projects for the rest of this week and almost all of next week. However, I still managed to accomplish a few tasks. I cultured and split my cells (J65C 4.4 and 6.6). 4.4 seemed more dense, meaning that there seemed to be more cells in the container, but Victor assured me that they were just larger. Victor did not guide me, he was merely there for supervision and if I needed to ask any questions. I successfully split the cells with little to no trouble.
Laura then asked me to make some devices with PDMS, so I did that, too--on my own. Laura did not give me any instruction. I successfully made two PDMS solutions to be used as molds for the well chip and the flow-patterning device.
Laura also sent me some reference articles and papers with background information on her project where she is studying cell signaling. I am not completely sure on the specifics of her project, so once I finish reading the articles, I will be sure to ask her.