Inspired by natural materials such as bone, minerals and other substances, engineers have coaxed bacterial cells to produce biofilms that can incorporate nonliving materials such as gold nanoparticles and quantum dots.
These 'living materials' combine the advantages of live cells which respond to their environment, produce complex biological molecules and span multiple length scales - with the benefits of nonliving materials that add functions such as conducting electricity or emitting light.
"The new technique could one day be used to design more complex devices such as solar cells, self-healing materials or diagnostic sensors," said Timothy Lu, an assistant professor of electrical engineering and biological engineering at Massachusetts Institute of Technology (MIT).
The idea is to put the living and the nonliving worlds together to make hybrid materials that have living cells in them and are functional, Lu added.
Lu and his colleagues chose to work with the bacterium E. coli because it naturally produces biofilms that contain so-called 'curli fibres' - amyloid proteins that help E coli attach to surfaces.
Each curli fibre is made from a repeating chain of identical protein subunits called CsgA which can be modified by adding protein fragments called peptides.
These peptides can capture nonliving materials such as gold nanoparticles, incorporating them into the biofilms.
They also engineered the cells so they could communicate with each other and change the composition of the biofilm over time.
"It is a simple system but what happens over time is you get curli that is increasingly labeled by gold particles. It shows that indeed you can make cells that talk to each other and they can change the composition of the material over time," Lu explained.
"Ultimately, we hope to emulate how natural systems, like bone, form. No one tells bone what to do but it generates a material in response to environmental signals," Allen Chen, a PhD student at MIT-Harvard, noted.
These hybrid materials could be worth exploring for use in energy applications such as batteries and solar cells, said the researchers in the journal Nature Materials.