Hello! Welcome to micROS—a collaboration between McGill Biodesign and the McGill Rocket Team! Together, we are investigating the changes in levels of reactive oxidative species in microgravity and hyper gravity environments. Our McGill Biodesign team is focused on designing 1) the microfluidic chip composed of channels for the flow of reagents and a microwell holding the cells and where the reaction will take, 2) the perfusion system for timely and efficient delivery of reagents to the microwell containing the cells, and 3) the hydrogel that the cells will be embedded in to keep them alive throughout the experiment.
Reactive Oxidative Species (ROS) can have many positive roles in the body, particularly facilitating the apoptosis, the programmed cell death, of mutated cells. Unfortunately, as its name suggests, these species–specifically in their free radical form–are very reactive and hence are capable of great harm to humans. In fact, free radicals induce oxidative stresses in cells, possibly causing damage to them, when overproduced. This can occur through exhaustive exercise, frequent exposure to environmental pollutants and radiation, or hypergravity and microgravity, which can potentially negatively impact astronauts.
Previous studies have suggested that ROS released specifically by macrophages tend to increase in hypergravity and decrease in microgravity environments. Interestingly, macrophages kill bacteria through ROS production, and this could be linked to the increased susceptibility of astronauts to infections. Thus, we wanted to observe and confirm changes in macrophage ROS levels in different space environments.
Our team set out to design a microfluidics system that encapsulates alveolar macrophages and ensures reagents reach these cells in time to measure ROS levels in the micro and hyper-gravity environments. Described in further detail below, our proposed system contains a 3D printed chip connected to a peristaltic pump that will deliver reagents to the macrophages nested in a hydrogel matrix.
The microfluidic chip team designed and manufactured a chip that combines and precisely channels reagents to reach a microwell the moment the chip experiences microgravity and hypergravity during a rocket's flight. After designing iterations, analysing fluid dynamics, prototyping, testing, and using high-resolution 3D printing, we perfected the chip design. Many factors were considered, but the following are the most notable.
The channel design uses passive mixing techniques with the highest mixing coefficients, serpentine channels, J-shaped baffles, and an optimal channel combination angle to promote the dispersion of the reagents. The microwell dimensions were selected for the best possible surface area considering the distribution of the macrophages and to reduce the formation of bubbles at the channel-microwell interface. The chip is semi-covered to enable easier manufacturing processes, as well as to ensure a water-tight seal whilst facilitating access to the microwell.
The team was very successful and enthusiastic, working together to reach goals ahead of schedule, ultimately achieving the team’s main aim of designing and producing a specialised, functioning microfluidic chip. Given more time, further prototyping would have been done using other methods, such as the “Shrinky Dink” method. Results from the testing of these prototypes would have then been compared to a computational fluid analysis of the chip, to allow us to quantify the ability of the chip design.
This subteam worked on the hydrogel that would contain the macrophages inside the microfluidic chip. We researched the base materials as well as the manufacturing methods including dimensions, mechanical properties of the gel, and potential additions. We found that the best solution was an HA-PEG composite hydrogel crosslinked with collagen that had the mechanical properties and biocompatibility to simulate the macrophages' natural microenvironment. Our next steps for the project are to test our composite and attempt to successfully grow macrophages on the gel. We would need to determine through laboratory tests whether macrophages produced enough ROS to detect when embedded, and what the optimal confluency of cells should be.
The perfusion subteam is working on a peristaltic pump to drive the reagents through the chip. It will be composed of 3D printed parts as well as a motor controlled by an Arduino. The peristaltic pump relies on the driving force of rollers, which compress tubes and create a pressure difference, drawing fluid into the tube and allowing fluid flow. We will use this concept by powering a motor attached to rollers in order to push reagants into the microfluidic chip, modifying the rpm to suit the needs of the macrophage experiment.
Future of Project
The next steps of the project would include testing the design of the 3D printed chip when attached to the perfusion system and with the hydrogel added to the microwell. The entire system must run smoothly, from the introduction of reagents to the swelling of the hydrogel with encapsulated cells. Then, we hope to integrate our design with a fluorescence detection system to test if ROS can be measured and how well it can be done.
Ultimately, we hope to have the opportunity to send the entire system into space to best mimic micro and hyper gravity environments to achieve our initial goal.
Hi everyone! My name is Mary and I’m a U2 Bioeng student in my 3rd year, and I’m the team lead for micROS for this year. I am responsible for ensuring that the project runs smoothly, coordinating with subteam leaders and with the MRT team and contacting our mentor. In my free time, I enjoy nature walks and hiking in Banff, working with little kids, and watching hockey.