How engineered living biomaterials could change manufacturing forever.
Whether algae-based or oil-derived, all our industrial materials are composed of dead matter. Predictable and, above all stable, inert substances are ideal for many practical purposes. Their relatively simple molecular structures can be heated, twisted, and chemically treated to obtain fixed physical properties.
Yet there are many useful things that living organisms can do that dead matter cannot. Scientists are now creating a new class of functional materials known as engineered living materials (ELM). Tailored from biological constituents, they are the first ever artificial materials to behave like living organisms.
What makes ELM alive?
ELMs tap into two traits that set natural organisms apart from conventional man-made substances. At a basic level, living materials feel different. Our tissue is pliable yet resilient, enabling subtle and complex movements. The soft mechanics of living bodies allows another characteristic unique to biological lifeforms: their capacity to respond to environmental changes. Plants, animals, and microorganisms can alter their behaviours, both at the levels of cells and organs, to weather new external conditions. By regenerating tissue or changing cell functions, they can escape threats or actively influence their surroundings. This purposeful autonomy allows them to survive a world in constant flux.
At the basis of this adaptive capacity is cell signalling. This is the way that living cells constantly transmit chemical instructions among themselves. When faced with temperature, chemical, and light changes, the instructions tell the cells to perform new functions. Scientists can now manipulate the genetic information within cells to determine what environmental cues they respond to and how.
The most obvious applications for these advances lie in medicine. Because therapeutic substances work at molecular and cellular scales, materials that can be precisely tuned to respond to minute chemical changes are much in demand. Of course, we already use living organisms in health. Generally speaking, biomaterials are loaded with therapeutic microbes and then placed inside the body. Think about probiotic yoghurts that deliver beneficial bacteria to your gut in a delicious dairy medium.
However, engineered living biomaterials go a step further. It involves genetically re-programming microbial strains to respond to what’s happening in their surroundings in real time. For example, customed bacterial cultures could register changes in the biochemicals fluctuations of body fluids for health monitoring purposes. These cultures could be attached to the human body via wearables or even inked on the skin with bio-tattoos. Genetically engineered microbes could also become smart wound healing substances. E. Coli strains can be programmed to secrete curli nanofibers, a substance with powerful adhesive properties. They can be engineered to detect blood haemoglobin, the presence of which would activate curli fibres production to mend torn vessels.
Harvard’s Wyss Institute for Biologically Inspired Engineering is a premiere centre for ELM R&D. Their researchers have re-worked RNA molecules, the component of DNA that translates genetic information into different proteins. These customised RNA molecules create proteins that can detect and treat diseased cells without affecting benign ones. They call this a living cellular device.
Wyss Institute researchers are also creating much larger living devices. Earlier this year, they unveiled a biohybrid fish built from a combination of biological components (in this case, cardiac muscle cells cultured from human stem cells) as well as conventional synthetics materials. This cyborg fish can swim of its own accord using propulsion generated by the same muscle contractions that pump living human hearts. A fascinating feature of this fish is that as its heart cell components matured, the fish improved its swimming speed. The ultimate goal is to develop an artificial heart that will seamlessly integrate into the body and, like natural living organs, replace cells over its lifetime.
Wyss researchers also work at a scale smaller than that of the cell, programming the fundamental molecular components of DNA to create self-organising nano-robots. These molecular robots can carry out specific tasks adaptatively without requiring an external power source. These vibrant swarms of matter form assemblages of DNA that can be used as molecular sensors, computers, and actuators. At this scale, biology fades into chemistry. While the individual molecules behave in a highly ordered and predictable manner, their collective behaviour exhibits emergent properties we associate with whole living organisms: the ability to respond sensitively and even creatively to environmental changes.
ELMs also hold applications in environmentally sensitive robotic design. The Center for Micro-BioRobotics at the Instituto Italiano di Technologia is developing what are known as plant-inspired robots or “Green robots”, autonomous devices that blend into natural ecosystems. They might be infrastructure-exploring robots inspired by climbing plants or tiny environmental monitoring gadgets modelled on seeds. These green robots are not only built from sustainable materials but operate in a way that leaves nature undisturbed. Their flexible bio-bodies allow them to perform movements that mimic those of wild organisms.
Living materials could also become part of our built environment. Currently, the most commercially successful examples of ELM can be found in the construction and design sector with Ecovative Design and Mycoworks leading the way in producing living bricks and clothing materials at scale. In March 2022, Singaporean researchers published on fungal-bacterial biocomposites that can be cultivated into self-healing large structures that sense the world around them. These materials are easy to reproduce since the growth medium is simple wood waste.
Another way that living materials could find their way into everyday usage is through self-cleaning surfaces. Researchers at the Zurich-based Institute for Chemical and Bioengineering have used the fungal strain penicillium roqueforti to build a thin, dormant layer that springs into action when it detects food particles. Once it seizes upon a food spill, it metabolises it and uses it to grow. They have also developed an antibiotic releasing surface that uses penicillium chrysogenum to prevent bacterial growth. Biosensing surfaces like this would make it possible to build large-scale infrastructure that sweeps up pollutants and toxins from the environment.
The ultimate ambition of ELM is to devise substances that self-organise into a variety of complex materials using energy and matter from the immediate environment. We see this throughout nature. Seeds develop into trees that can produce the cellulose and lignin of bark as well as the complex molecular apparatuses for photosynthesis. Animals grow from single cells to complex organisms containing everything from fibrous proteins to fatty tissues. The growth and differentiation of cells is directed entirely by the genetic information contained inside them. Similarly, the most advanced ELM will require little human guidance to produce chemically and functionally distinct materials that work together as a whole system.
The future of ELMs
ELMs have not so far been scaled. Prototypes are small, generally in the nano to centimetre range. A 2021 pathfinder challenge announced by the European Innovation Council for example called for examples of novel ELMs bigger than 1 cm cubed. This reflects how researchers are still figuring out how to control cell growth and the viability of larger samples, especially in more complex formations. ELM production would also require sweeping changes to our manufacturing infrastructure, which today revolves around welding, milling, and grinding tools. Producing ELM at scale will require reducing the cost of making and operating the specialised bioreactors needed to cultivate large amounts of cellular substances.
The field of ELM is so new that it is hard to predict the full social and technological implications of mass commercialisation. However, the potential sustainability impacts of scaled ELM are huge. Aside from offering new customisable functions that elude even the most advanced synthetic materials, the obvious advantage of living engineered materials is that they are completely biodegradable. ELM offers the possibility of technologies that are indistinguishable from nature’s products.
Another potential advantage of self-healing living biomaterials is that we could manufacture products with a longer lifespan. Today, companies have massive incentives to make disposable products that feed the consumer cycle. This places serious limits on our ability to construct a sustainable and circular economy. To minimise virgin resource extraction and manufacturing emissions, some governments are establishing ‘right to repair’ laws to make companies ensure their products last longer. Materials with an inbuilt ability to repair themselves could support these efforts to build permanence into the material economy.