Team:BrownStanfordPrinctn/Hardware
Designing and Fabricating Microfluidics for Drug Production
This summer our team designed microfluidic devices that produce and purify biopharmaceuticals. We then worked with the Fordyce Lab and NASA Ames SpaceShop to produce functional PDMS and 3D printed devices. Below you can look at pictures of our designs, devices, and fabrication process.
AutoCAD drawing for SEC module
AutoCAD drawing for IMAC module
SU8 on a silicon wafer before spinning
Spinning photoresist on a silicon wafer
Preparing wafers for exposure to UV
Developing wafers with UV radiation
Why Microfluidics?
Our goal for this project was to create a drug production system that could be used on long term space missions. This meant that while our system only had to produce a single dose of medicine, it had to do so fast (under 24 hours), and with minimal mass requirements. Using conventional fluid handling would not be feasible for a project like this, as bringing up large scale lab equipment to purify medicine would require significant mass. We designed microfluidic chips that were only a few centimeters long and made out of lightweight glass and PDMS to reduce mass requirements for production and purification. The ability to chain chips together to avoid human liquid handling has allowed us to carry out what would be equipment intensive processes on just 3 chips powered by a syringe pump. Further, the small amounts of liquid contained on chips speed chemical reactions significantly, making on chip purification faster than standard techniques. These advantages make microfluidics an attractive option for a drug production in space.
An End to End Process
Our first foray into microfluidics was our creation of a 3D printed microfluidic used to produce drugs. This chip is designed to take liquids from up to 3 sources, mix them, and then retain them to allow for protein expression. This makes the chip compatible with a cell free system, in that it can mix the different components of the system and allow expression for several hours. The chip also works with a cellular system, as one chip can hold cells that produce protein, while another can mix the cells with detergent to lyse them. The following pictures show our design and chips that we produced.
Image of the SOLIDWORKS file for the expression chip
Printed final version of the expression chip interfaced with a syringe and tubing
We went through several versions of this chip due to difficulties in the manufacturing process. Our chip was originally going to be printed in two halves, with alignment markers to allow the chip to be assembled. This proved to be more difficult than expected, as it would cause significant leakage in the chip, and the alignment markers often wouldn’t fit together right. After several attempts at reworking the alignment markers, it was decided that it would instead be best to print in one solid piece. While this required enlarging several features due to reduced resolution, it also made fabrication much more practical and resulted in a functioning prototype. All 3D printing was done using a Form 2 SLA printer at the NASA Ames SpaceShop, with assistance through the entire fabrication process provided by their staff.
To convert drugs produced using our expression chip to a more usable form, we designed a purification system which could carry out two different processes, Immobilized Metal Affinity Chromatography (IMAC), and Size Exclusion Chromatography (SEC). The first of these runs the solution through negatively charged resin, which allows positive His tagged protein to bind to the column while impurities wash out. The protein can then be eluted using a salt solution, or the protein can be separated from the tags using a his tagged protease, which then sticks to the column itself. The second of these process is used for buffer exchange, removing small molecules and replacing them with a protein buffer that is safe for human use. We were able to fabricate a first round of chips with assistance from the Fordyce Lab, although some difficulties were encountered with loading resin into the chip. A second version of the chip with an enlarged media loading port is currently a work in progress.
Prototype for IMAC column interfaced with a syringe pump
Prototype for SEC column interfaced with a syringe pump
Flow test for IMAC column using blue food coloring to show liquid more clearly
Flow test for expression chip replacing blue food coloring with red food coloring
Expression, IMAC and SEC chips interfaced with syringe and collection tube, demonstrating fabrication of all Astropharmacy hardware