In a paper entitled “Programmable and printable Bacillus subtilis biofilms as engineered living materials,” a team of researchers discusses how they used 3D printing to produce custom nanoscale biomaterials from the natural secretion of amyloid fibers from the bacteria Bacillus subtilis. The bacteria generate biofilms by secreting amyloid fibers via a tightly controlled cluster of genes called the tapA-sipW-tasA operon. TapA nucleates the extracellular assembly of TasA proteins to create the amyloid nanofibers that give the biofilm its structural integrity. The researchers were able to genetically modify the TasA protein and introduce functional chemical groups onto the TasA fibers excreted by the bacteria. This means that the bacterial films could be designed to act as functional living materials.
The researchers were able to engineer the bacteria to secrete fibers containing enzymatic functional groups into harmless products. They also combined the biofilms produced with multiple bacterial strains, which allowed them to perform a two-step degradation of the pesticide paraoxan. This shows the potential for producing efficient, eco-friendly materials.
In addition to showing the functional capabilities of the biofilms, the researchers also studied their processability as materials. Because of the viscoelastic properties of the biofilms, they are well-suited to 3D printing. Modifying the functional groups on the secreted enzymes did not hinder the processability of the biofilms, instead enabling the researchers to tune their viscoelastic properties for 3D printing applications.
“In a series of increasingly complex proof-of-concept demonstrations, we deployed these engineered biofilms in fluorescence detection, conjugation chemistry, single-substrate bioremediation, and multireaction bioremediation cascades incorporating NPs,” the researchers state.“We also exploited the intrinsic viscoelastic properties of our engineered biofilms and fabricated well-defined ‘living shapes’, trapping these materials into hydrogels and microgels using 3D printing and microencapsulation techniques.”
The living materials were shown to be able to self-regenerate after printing, sustaining their original printing shape as well as their viscoelastic and functional properties. The bacteria were able to incorporate onto their fibers without affecting the biofilm growth or cell viability. The cells remained viable for five weeks without supplemental nutrition.
“As this new type of living functional material offers previously unattainable material performance properties relevant to manufacturing, our study opens the door for the development of many conceivable new classes of complex multifunctional materials and dynamic and regenerative nanotechnologies,” the researchers conclude.
Authors of the paper include Jiaofang Huang, Suying Liu, Chen Zhang, Xinyu Wang, Jiahua Pu, Fang Ba, Shuai Xue, Haifeng Ye, Tianxin Zhao, Ke Li, Yanyi Wang, Jicong Zhang, Lihua Wang, Chunhai Fan, Timothy K. Lu and Chao Zhong.
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