The researchers observed how the ribbon proteins unfurled and pierced the membranes of the bacterial cells when their environment became more acid.
Now, another inspiration from nature offers a possible solution in the form of protein ribbons that - under certain, controllable conditions - unfurl into sharp needles that can pierce through membranes. They are reminiscent of those paper party horns that uncurl when you blow them.
The coiled proteins are called R bodies, and they can be found inside bacteria that inhabit tiny aquatic, one-celled organisms called paramecia.
The bacteria unfurl the R bodies to deliver toxins to other one-celled creatures that threaten their hosts.
In its elongated state, the unfurled protein polymer becomes a needle that pierces the membrane of the target organism.
R bodies burst open 60% of E. coli cells
In a paper published in the journal Synthetic Biology, Pamela A. Silver and Jessica K. Polka, of Harvard University in Boston, MA, describe how they turned to R bodies as a possible mechanism for unloading encapsulated drugs inside cells.
In lab experiments, the researchers found they could control the sensitivity of R bodies so they unfurl when the acidity of their environment changes.
They then tested them inside cells of Escherichia coli, using the bacteria as a substitute for vesicles.
They found the proteins burst open the membranes of 60% of the E. coli cells under conditions of increased acidity. The authors conclude:
"As such, these protein machines present a novel way to selectively rupture membrane compartments and will be important for programming cellular compartmentalization."
The researchers say because they change state rapidly and reversibly, R bodies could be useful for a variety of biotechnology applications that target delivery of molecules inside living systems.
The following video sums up the research and demonstrates the action of R bodies inside E. coli cells:
The researchers note that R bodies could also be used as switches inside microelectromechanical systems (MEMS), a new technology with many applications in bioengineering - for example, biosensors and biochips - and other fields.
Meanwhile, Medical News Today recently learned how researchers are developing a new biomaterial for encapsulating implanted human pancreatic cells that helps them withstand attack by the immune system without losing their ability to sense blood sugar and produce insulin. Tests in mice showed the implanted encapsulated cells lasted for at least 6 months.