Washington DC: What if there was a device that could act a bit like a "pharmacy on demand" by creating a variety of drugs? Turns out, a team of researchers has already turned this idea into a reality.
The portable production system, designed to manufacture a range of biopharmaceuticals on demand, has been developed by researchers at MIT, with funding from the Defense Advanced Research Projects Agency (DARPA).
The researchers demonstrated that the system can be used to produce a single dose of treatment from a compact device containing a small droplet of cells in a liquid.
In this way, the system could ultimately be carried onto the battlefield and used to produce treatments at the point of care. It could also be used to manufacture a vaccine to prevent a disease outbreak in a remote village, according to senior author Tim Lu.
"Imagine you were on Mars or in a remote desert, without access to a full formulary, you could program the yeast to produce drugs on demand locally," Lu said.
The system is based on a programmable strain of yeast, Pichia pastoris, which can be induced to express one of two therapeutic proteins when exposed to a particular chemical trigger. The researchers chose P. pastoris because it can grow to very high densities on simple and inexpensive carbon sources and is able to express large amounts of protein.
"We altered the yeast so it could be more easily genetically modified, and could include more than one therapeutic in its repertoire," Lu noted.
When the researchers exposed the modified yeast to estrogen beta-estradiol, the cells expressed recombinant human growth hormone (rHGH). In contrast, when they exposed the cells to methanol, the yeast expressed the protein interferon.
The cells are held within a millimeter-scale table-top microbioreactor, containing a microfluidic chip, which was originally developed by Rajeev Ram and his team, and then commercialized by co-author Kevin Lee through a spin-off company.
A liquid containing the desired chemical trigger is first fed into the reactor, to mix with the cells. Inside the reactor, the cell-and-chemical mixture is surrounded on three sides by polycarbonate; on the fourth side is a flexible and gas-permeable silicone rubber membrane.
By pressurizing the gas above this membrane, the researchers are able to gently massage the liquid droplet to ensure its contents are fully mixed together. "This makes sure that the one milliliter (of liquid) is homogenous, and that is important because diffusion at these small scales, where there is no turbulence, takes a surprisingly long time," said Ram.
Because the membrane is gas permeable, it allows oxygen to flow through to the cells, while any carbon dioxide they produce can be easily extracted. The device continuously monitors conditions within the microfluidic chip, including oxygen levels, temperature, and pH, to ensure the optimum environment for cell growth. It also monitors cell density.
If the yeast is required to produce a different protein, the liquid is simply flushed through a filter, leaving the cells behind. Fresh liquid containing a new chemical trigger can then be added, to stimulate production of the next protein.
The study is published in the journal Nature Communications....