A Stomach Implant Saved Me. When Your Organs Fail, You Could Become a Cyborg, Too
Beware, cyborgs walk among us. They’re mostly indistinguishable from regular humans and are infiltrating every nook and cranny of society. For full disclosure, I’m one myself. No, we’re not deadly intergalactic conquerors like the Borg race of Star Trek fame, just ordinary people living better with chronic conditions thanks to medical implants.
In recent years there has been an explosion of developments in implantable devices that merge multiple technologies into gadgets that work in concert with human physiology for the treatment of serious diseases. Pacemakers for the heart are the best-known implants, as well as other cardiac devices like LVADs (left-ventricular assist devices) and implanted defibrillators. Next-generation devices address an array of organ failures, and many are intended as permanent. The driving need behind this technology: a critical, persistent shortage of implantable biological organs.
The demand for transplantable organs dwarfs their availability. There are currently over 100,000 people on the transplant waiting list in the U.S., compared to 40,000 transplants completed in 2021. But even this doesn’t reflect the number of people in dire straits who don’t qualify for a transplant because of things like frailty, smoking status and their low odds of surviving the surgery.
My journey to becoming a cyborg came about because of a lifelong medical condition characterized by pathologically low motility of the digestive system, called gastroparesis. Ever since I was in my teens, I’ve had chronic problems with severe nausea. Flareups can be totally incapacitating and last anywhere from hours to months, interspersed with periods of relief. The cycle is totally unpredictable, and for decades my condition went both un- and misdiagnosed by doctors who were not even aware that the condition existed. Over the years I was labeled with whatever fashionable but totally inappropriate medical label existed at the time, and not infrequently, hypochondria.
Living with the gastric pacer is easy. In fact, most of the time, I don’t even know it’s there.
One of the biggest turning points in my life came when a surgeon at the George Washington University Hospital, Dr. Frederick Brody, ordered a gastric emptying test that revealed gastroparesis. This was in 2009, and an implantable device, called a gastric pacer, had been approved by the FDA for compassionate use, meaning that no other treatments were available. The small device is like a pacemaker that’s implanted beneath the skin of the abdomen and is attached to the stomach through electrodes that carry electrical pulses that stimulate the stomach, making it contract as it’s supposed to.
Dr. Brody implanted the electrical wires and the device, and, once my stomach started to respond to the pulses, I got the most significant nausea relief I’d had in decades of futile treatments. It sounds cliché to say that my debt to Dr. Brody is immeasurable, but the pacer has given me more years of relative normalcy than I previously could have dreamed of.
I should emphasize that the pacer is not a cure. I still take a lot of medicine and have to maintain a soft, primarily vegetarian diet, and the condition has progressed with age. I have ups and downs, and can still have periods of severe illness, but there’s no doubt I would be far worse off without the electrical stimulation provided by the pacer.
Living with the gastric pacer is easy. In fact, most of the time, I don’t even know it’s there. It entails periodic visits with a surgeon who can adjust the strength of the electrical pulses using a wireless device, so when symptoms are worse, he or she can amp up the juice. If the pulses are too strong, they can cause annoying contractions in the abdominal muscles, but this is easily fixed with a simple wireless adjustment. The battery runs down after a few years, and when this happens the whole device has to be replaced in what is considered minor surgery.
Such devices could fill gaps in treating other organ failures. By far most of the people on transplant waiting lists are waiting for kidneys. Despite the fact that live donations are possible, there’s still a dire shortage of organs. A bright spot on the horizon is The Kidney Project, a program spearheaded by bioengineer Shuvo Roy at the University of California, San Francisco, which is developing a fully implantable artificial kidney. The device combines living cells with artificial materials and relies not on a battery, but on the patient’s own blood pressure to keep it functioning.
Several years into this project, a prototype of the kidney, about the size of a smart phone, has been successfully tested in pigs. The device seems to provide many of the functions of a biological kidney (unlike dialysis, which replaces only one main function) and reliably produces urine. One of its most critical components is a special artificial membrane, called a hemofilter, that filters out toxins and waste products from the blood without leaking important molecules like albumin. Since it allows for total mobility, the artificial kidney will provide patients with a higher quality of life than those on dialysis, and is in some important ways, even better than a biological transplant.
The beauty of the device is that, even though it contains kidney cells sourced, as of now, from cadavers or pigs, the cells are treated so that they can’t be rejected and the device doesn’t require the highly problematic immunosuppressant drugs a biological organ requires. “Anti-rejection drugs,” says Roy, “make you susceptible to all kinds of infections and damage the transplanted organ, causing steady deterioration. Eventually they kill the kidney. A biological transplant has about a 10-year limit,” after which the kidney fails and the body rejects it.
Eventually, says Roy, the cells used in the artificial kidney will be sourced from the patient himself, the ultimate genetic match. The patient’s adult stem cells can be used to produce some or all of the 25 to 30 specialized cells of a biological kidney that provide all the functions of a natural organ. People formerly on dialysis could drastically improve their functionality and quality of life without being tethered to a machine for hours at a time, three days a week.
As exciting as this project is, it suffers from a common theme in early biomedical research—keeping a steady stream of funding that will move the project from the lab, into human clinical trials and eventually to the bedside. “It’s the issue,” says Roy. “Potential investors want to see more data indicating that it works, but you need funding to create data. It’s a Catch-22 that puts you in a kind of no-man’s land of funding.” The constant pursuit of funding introduces a variable that makes it hard to predict when the kidney will make it to market, despite the enormous need for such a technology.
Another critical variable is if and when insurance companies will decide to cover transplants with the artificial kidney, so that it becomes affordable for the average person. But Roy thinks that this hurdle, too, will be crossed. Insurance companies stand to save a great deal of money compared to what they ordinarily spend on transplant patients. The cost of yearly maintenance will be a fraction of that associated with the tens of thousands of dollars for immunosuppressant drugs and the attendant complications associated with a biological transplant.
One estimate that the multidisciplinary team of researchers involved with The Kidney Project are still trying to establish is how long the artificial kidney will last once transplanted into the body. Animal trials so far have been looking at how the kidney works for 30 days, and will soon extend that study to 90 days. Additional studies will extend much farther into the future, but first the kidneys have to be implanted into people who can be followed over many years to answer this question. But unlike the gastric pacer and other implants, there won’t be a need for periodic surgeries to replace a depleted battery, and the stark improvements in quality of life compared to dialysis add a special dimension to the value of whatever time the kidney lasts.
Another life-saving implant could address a major scourge of the modern world—heart disease. Despite significant advances in recent decades, including the cardiac implants mentioned above, cardiovascular disease still causes one in three deaths across the world. One of the most promising developments in recent years is the Total Artificial Heart, a pneumatically driven device that can be used in patients with biventricular heart failure, affecting both sides of the heart, when a biological organ is not available.
The TAH is implanted in the chest cavity and has two tubes that snake down the body, come out through the abdomen and attach to a 13.5-pound external driver that the patient carries around in a backpack. It was first developed as a bridge to transplant, a temporary alternative while the patient waited for a biological heart to replace it. However, SynCardia Systems, LLC, the Tucson-based company that makes it, is now investigating whether the heart can be used on a long-term basis.
There’s good reason to think that this will be the case. I spoke with Daniel Teo, one of the board members of SynCardia, who said that so far, one patient lived with the TAH for six years and nine months, before he died of other causes. Another patient, still alive, has lived with the device for over five years and another one has lived with it for over four years. About 2,000 of these transplants have been done in patients waiting for biological hearts so far, and most have lived mobile, even active lives. One TAH recipient hiked for 600 miles, and another ran the 4.2-mile Pat Tillman Run, both while on the artificial heart. This is a far cry from their activities before surgery, while living with advanced heart failure.
Randy Shepard, a recipient of the Total Artificial Heart, teaches archery to his son.
Randy Shepard
If removing and replacing one’s biological heart with a synthetic device sounds scary, it is. But then so is replacing one’s heart with biological one. “The TAH is very emotionally loaded for most people,” says Teo. “People sometimes hold back because of philosophical, existential questions and other nonmedical reasons.” He also cites cultural reasons why some people could be hesitant to accept an artificial heart, saying that some religions could frown upon it, just as they forbid other medical interventions.
The first TAHs that were approved were 70 cubic centimeters in size and fit into the chest cavities of men and larger women, but there’s now a smaller, 50 cc size meant for women and adolescents. The FDA first cleared the 70 cc heart as a bridge to transplant in 2004, and the 50 cc model received approval in 2014. SynCardia’s focus now is on seeking FDA approval to use the heart on a long-term basis. There are other improvements in the works.
One issue being refined deals with the external driver that holds the pneumatic device for moving the blood through a patient’s body. The two tubes connecting the driver to the heart entail openings in the skin that could get infected, and carrying the backpack is less than ideal. The driver also makes an audible sound that some people find disturbing. The next generation TAH will be quieter and involve wearing a smaller, lighter device on a belt rather than carrying the backpack. SynCardia is also working toward a fully implantable heart that wouldn’t require any external components and would contain an energy source that can be recharged wirelessly.
Teo says the jury is out as to whether artificial hearts will ever obviate the need for biological organs, but the world’s number one killer isn’t going away any time soon. “The heart is one of the strongest organs,” he says, “but it’s not made to last forever. If you live long enough, the heart will eventually fail, and heart failure leads to the failure of other organs like the kidney, the lungs and the liver.” As long as this remains the case and as long as the current direction of research continues, artificial organs are likely to play an ever larger part of our everyday lives.
Oh, wait. Maybe we cyborgs will take over the world after all.
Creamy milk with velvety texture. Dark with sprinkles of sea salt. Crunchy hazelnut-studded chunks. Chocolate is a treat that appeals to billions of people worldwide, no matter the age. And it’s not only the taste, but the feel of a chocolate morsel slowly melting in our mouths—the smoothness and slipperiness—that’s part of the overwhelming satisfaction. Why is it so enjoyable?
That’s what an interdisciplinary research team of chocolate lovers from the University of Leeds School of Food Science and Nutrition and School of Mechanical Engineering in the U.K. resolved to study in 2021. They wanted to know, “What is making chocolate that desirable?” says Siavash Soltanahmadi, one of the lead authors of a new study about chocolates hedonistic quality.
Besides addressing the researchers’ general curiosity, their answers might help chocolate manufacturers make the delicacy even more enjoyable and potentially healthier. After all, chocolate is a billion-dollar industry. Revenue from chocolate sales, whether milk or dark, is forecasted to grow 13 percent by 2027 in the U.K. In the U.S., chocolate and candy sales increased by 11 percent from 2020 to 2021, on track to reach $44.9 billion by 2026. Figuring out how chocolate affects the human palate could up the ante even more.
Building a 3D tongue
The team began by building a 3D tongue to analyze the physical process by which chocolate breaks down inside the mouth.
As part of the effort, reported earlier this year in the scientific journal ACS Applied Materials and Interfaces, the team studied a large variety of human tongues with the intention to build an “average” 3D model, says Soltanahmadi, a lubrication scientist. When it comes to edible substances, lubrication science looks at how food feels in the mouth and can help design foods that taste better and have more satisfying texture or health benefits.
There are variations in how people enjoy chocolate; some chew it while others “lick it” inside their mouths.
Tongue impressions from human participants studied using optical imaging helped the team build a tongue with key characteristics. “Our tongue is not a smooth muscle, it’s got some texture, it has got some roughness,” Soltanahmadi says. From those images, the team came up with a digital design of an average tongue and, using 3D printed molds, built a “mimic tongue.” They also added elastomers—such as silicone or polyurethane—to mimic the roughness, the texture and the mechanical properties of a real tongue. “Wettability" was another key component of the 3D tongue, Soltanahmadi says, referring to whether a surface mixes with water (hydrophilic) or, in the case of oil, resists it (hydrophobic).
Notably, the resulting artificial 3D-tongues looked nothing like the human version, but they were good mimics. The scientists also created “testing kits” that produced data on various physical parameters. One such parameter was viscosity, the measure of how gooey a food or liquid is — honey is more viscous compared to water, for example. Another was tribology, which defines how slippery something is — high fat yogurt is more slippery than low fat yogurt; milk can be more slippery than water. The researchers then mixed chocolate with artificial saliva and spread it on the 3D tongue to measure the tribology and the viscosity. From there they were able to study what happens inside the mouth when we eat chocolate.
The team focused on the stages of lubrication and the location of the fat in the chocolate, a process that has rarely been researched.
The artificial 3D-tongues look nothing like human tongues, but they function well enough to do the job.
Courtesy Anwesha Sarkar and University of Leeds
The oral processing of chocolate
We process food in our mouths in several stages, Soltanahmadi says. And there is variation in these stages depending on the type of food. So, the oral processing of a piece of meat would be different from, say, the processing of jelly or popcorn.
There are variations with chocolate, in particular; some people chew it while others use their tongues to explore it (within their mouths), Soltanahmadi explains. “Usually, from a consumer perspective, what we find is that if you have a luxury kind of a chocolate, then people tend to start with licking the chocolate rather than chewing it.” The researchers used a luxury brand of dark chocolate and focused on the process of licking rather than chewing.
As solid cocoa particles and fat are released, the emulsion envelops the tongue and coats the palette creating a smooth feeling of chocolate all over the mouth. That tactile sensation is part of the chocolate’s hedonistic appeal we crave.
Understanding the make-up of the chocolate was also an important step in the study. “Chocolate is a composite material. So, it has cocoa butter, which is oil, it has some particles in it, which is cocoa solid, and it has sugars," Soltanahmadi says. "Dark chocolate has less oil, for example, and less sugar in it, most of the time."
The researchers determined that the oral processing of chocolate begins as soon as it enters a person’s mouth; it starts melting upon exposure to one’s body temperature, even before the tongue starts moving, Soltanahmadi says. Then, lubrication begins. “[Saliva] mixes with the oily chocolate and it makes an emulsion." An emulsion is a fluid with a watery (or aqueous) phase and an oily phase. As chocolate breaks down in the mouth, that solid piece turns into a smooth emulsion with a fatty film. “The oil from the chocolate becomes droplets in a continuous aqueous phase,” says Soltanahmadi. In other words, as solid cocoa particles and fat are released, the emulsion envelops the tongue and coats the palette, creating a smooth feeling of chocolate all over the mouth. That tactile sensation is part of the chocolate’s hedonistic appeal we crave, says Soltanahmadi.
Finding the sweet spot
After determining how chocolate is orally processed, the research team wanted to find the exact sweet spot of the breakdown of solid cocoa particles and fat as they are released into the mouth. They determined that the epicurean pleasure comes only from the chocolate's outer layer of fat; the secondary fatty layers inside the chocolate don’t add to the sensation. It was this final discovery that helped the team determine that it might be possible to produce healthier chocolate that would contain less oil, says Soltanahmadi. And therefore, less fat.
Rongjia Tao, a physicist at Temple University in Philadelphia, thinks the Leeds study and the concept behind it is “very interesting.” Tao, himself, did a study in 2016 and found he could reduce fat in milk chocolate by 20 percent. He believes that the Leeds researchers’ discovery about the first layer of fat being more important for taste than the other layer can inform future chocolate manufacturing. “As a scientist I consider this significant and an important starting point,” he says.
Chocolate is rich in polyphenols, naturally occurring compounds also found in fruits and vegetables, such as grapes, apples and berries. Research found that plant polyphenols can protect against cancer, diabetes and osteoporosis as well as cardiovascular ad neurodegenerative diseases.
Not everyone thinks it’s a good idea, such as chef Michael Antonorsi, founder and owner of Chuao Chocolatier, one of the leading chocolate makers in the U.S. First, he says, “cacao fat is definitely a good fat.” Second, he’s not thrilled that science is trying to interfere with nature. “Every time we've tried to intervene and change nature, we get things out of balance,” says Antonorsi. “There’s a reason cacao is botanically known as food of the gods. The botanical name is the Theobroma cacao: Theobroma in ancient Greek, Theo is God and Brahma is food. So it's a food of the gods,” Antonorsi explains. He’s doubtful that a chocolate made only with a top layer of fat will produce the same epicurean satisfaction. “You're not going to achieve the same sensation because that surface fat is going to dissipate and there is no fat from behind coming to take over,” he says.
Without layers of fat, Antonorsi fears the deeply satisfying experiential part of savoring chocolate will be lost. The University of Leeds team, however, thinks that it may be possible to make chocolate healthier - when consumed in limited amounts - without sacrificing its taste. They believe the concept of less fatty but no less slick chocolate will resonate with at least some chocolate-makers and consumers, too.
Chocolate already contains some healthful compounds. Its cocoa particles have “loads of health benefits,” says Soltanahmadi. Dark chocolate usually has more cocoa than milk chocolate. Some experts recommend that dark chocolate should contain at least 70 percent cocoa in order for it to offer some health benefit. Research has shown that the cocoa in chocolate is rich in polyphenols, naturally occurring compounds also found in fruits and vegetables, such as grapes, apples and berries. Research has shown that consuming plant polyphenols can be protective against cancer, diabetes and osteoporosis as well as cardiovascular and neurodegenerative diseases.
“So keeping the healthy part of it and reducing the oily part of it, which is not healthy, but is giving you that indulgence of it … that was the final aim,” Soltanahmadi says. He adds that the team has been approached by individuals in the chocolate industry about their research. “Everyone wants to have a healthy chocolate, which at the same time tastes brilliant and gives you that self-indulging experience.”
In 1945, almost two decades after Alexander Fleming discovered penicillin, he warned that as antibiotics use grows, they may lose their efficiency. He was prescient—the first case of penicillin resistance was reported two years later. Back then, not many people paid attention to Fleming’s warning. After all, the “golden era” of the antibiotics age had just began. By the 1950s, three new antibiotics derived from soil bacteria — streptomycin, chloramphenicol, and tetracycline — could cure infectious diseases like tuberculosis, cholera, meningitis and typhoid fever, among others.
Today, these antibiotics and many of their successors developed through the 1980s are gradually losing their effectiveness. The extensive overuse and misuse of antibiotics led to the rise of drug resistance. The livestock sector buys around 80 percent of all antibiotics sold in the U.S. every year. Farmers feed cows and chickens low doses of antibiotics to prevent infections and fatten up the animals, which eventually causes resistant bacterial strains to evolve. If manure from cattle is used on fields, the soil and vegetables can get contaminated with antibiotic-resistant bacteria. Another major factor is doctors overprescribing antibiotics to humans, particularly in low-income countries. Between 2000 to 2018, the global rates of human antibiotic consumption shot up by 46 percent.
In recent years, researchers have been exploring a promising avenue: the use of synthetic biology to engineer new bacteria that may work better than antibiotics. The need continues to grow, as a Lancet study linked antibiotic resistance to over 1.27 million deaths worldwide in 2019, surpassing HIV/AIDS and malaria. The western sub-Saharan Africa region had the highest death rate (27.3 people per 100,000).
Researchers warn that if nothing changes, by 2050, antibiotic resistance could kill 10 million people annually.
To make it worse, our remedy pipelines are drying up. Out of the 18 biggest pharmaceutical companies, 15 abandoned antibiotic development by 2013. According to the AMR Action Fund, venture capital has remained indifferent towards biotech start-ups developing new antibiotics. In 2019, at least two antibiotic start-ups filed for bankruptcy. As of December 2020, there were 43 new antibiotics in clinical development. But because they are based on previously known molecules, scientists say they are inadequate for treating multidrug-resistant bacteria. Researchers warn that if nothing changes, by 2050, antibiotic resistance could kill 10 million people annually.
The rise of synthetic biology
To circumvent this dire future, scientists have been working on alternative solutions using synthetic biology tools, meaning genetically modifying good bacteria to fight the bad ones.
From the time life evolved on earth around 3.8 billion years ago, bacteria have engaged in biological warfare. They constantly strategize new methods to combat each other by synthesizing toxic proteins that kill competition.
For example, Escherichia coli produces bacteriocins or toxins to kill other strains of E.coli that attempt to colonize the same habitat. Microbes like E.coli (which are not all pathogenic) are also naturally present in the human microbiome. The human microbiome harbors up to 100 trillion symbiotic microbial cells. The majority of them are beneficial organisms residing in the gut at different compositions.
The chemicals that these “good bacteria” produce do not pose any health risks to us, but can be toxic to other bacteria, particularly to human pathogens. For the last three decades, scientists have been manipulating bacteria’s biological warfare tactics to our collective advantage.
In the late 1990s, researchers drew inspiration from electrical and computing engineering principles that involve constructing digital circuits to control devices. In certain ways, every cell in living organisms works like a tiny computer. The cell receives messages in the form of biochemical molecules that cling on to its surface. Those messages get processed within the cells through a series of complex molecular interactions.
Synthetic biologists can harness these living cells’ information processing skills and use them to construct genetic circuits that perform specific instructions—for example, secrete a toxin that kills pathogenic bacteria. “Any synthetic genetic circuit is merely a piece of information that hangs around in the bacteria’s cytoplasm,” explains José Rubén Morones-Ramírez, a professor at the Autonomous University of Nuevo León, Mexico. Then the ribosome, which synthesizes proteins in the cell, processes that new information, making the compounds scientists want bacteria to make. “The genetic circuit remains separated from the living cell’s DNA,” Morones-Ramírez explains. When the engineered bacteria replicates, the genetic circuit doesn’t become part of its genome.
Highly intelligent by bacterial standards, some multidrug resistant V. cholerae strains can also “collaborate” with other intestinal bacterial species to gain advantage and take hold of the gut.
In 2000, Boston-based researchers constructed an E.coli with a genetic switch that toggled between turning genes on and off two. Later, they built some safety checks into their bacteria. “To prevent unintentional or deleterious consequences, in 2009, we built a safety switch in the engineered bacteria’s genetic circuit that gets triggered after it gets exposed to a pathogen," says James Collins, a professor of biological engineering at MIT and faculty member at Harvard University’s Wyss Institute. “After getting rid of the pathogen, the engineered bacteria is designed to switch off and leave the patient's body.”
Overuse and misuse of antibiotics causes resistant strains to evolve
Adobe Stock
Seek and destroy
As the field of synthetic biology developed, scientists began using engineered bacteria to tackle superbugs. They first focused on Vibrio cholerae, which in the 19th and 20th century caused cholera pandemics in India, China, the Middle East, Europe, and Americas. Like many other bacteria, V. cholerae communicate with each other via quorum sensing, a process in which the microorganisms release different signaling molecules, to convey messages to its brethren. Highly intelligent by bacterial standards, some multidrug resistant V. cholerae strains can also “collaborate” with other intestinal bacterial species to gain advantage and take hold of the gut. When untreated, cholera has a mortality rate of 25 to 50 percent and outbreaks frequently occur in developing countries, especially during floods and droughts.
Sometimes, however, V. cholerae makes mistakes. In 2008, researchers at Cornell University observed that when quorum sensing V. cholerae accidentally released high concentrations of a signaling molecule called CAI-1, it had a counterproductive effect—the pathogen couldn’t colonize the gut.
So the group, led by John March, professor of biological and environmental engineering, developed a novel strategy to combat V. cholerae. They genetically engineered E.coli to eavesdrop on V. cholerae communication networks and equipped it with the ability to release the CAI-1 molecules. That interfered with V. cholerae progress. Two years later, the Cornell team showed that V. cholerae-infected mice treated with engineered E.coli had a 92 percent survival rate.
These findings inspired researchers to sic the good bacteria present in foods like yogurt and kimchi onto the drug-resistant ones.
Three years later in 2011, Singapore-based scientists engineered E.coli to detect and destroy Pseudomonas aeruginosa, an often drug-resistant pathogen that causes pneumonia, urinary tract infections, and sepsis. Once the genetically engineered E.coli found its target through its quorum sensing molecules, it then released a peptide, that could eradicate 99 percent of P. aeruginosa cells in a test-tube experiment. The team outlined their work in a Molecular Systems Biology study.
“At the time, we knew that we were entering new, uncharted territory,” says lead author Matthew Chang, an associate professor and synthetic biologist at the National University of Singapore and lead author of the study. “To date, we are still in the process of trying to understand how long these microbes stay in our bodies and how they might continue to evolve.”
More teams followed the same path. In a 2013 study, MIT researchers also genetically engineered E.coli to detect P. aeruginosa via the pathogen’s quorum-sensing molecules. It then destroyed the pathogen by secreting a lab-made toxin.
Probiotics that fight
A year later in 2014, a Nature study found that the abundance of Ruminococcus obeum, a probiotic bacteria naturally occurring in the human microbiome, interrupts and reduces V.cholerae’s colonization— by detecting the pathogen’s quorum sensing molecules. The natural accumulation of R. obeum in Bangladeshi adults helped them recover from cholera despite living in an area with frequent outbreaks.
The findings from 2008 to 2014 inspired Collins and his team to delve into how good bacteria present in foods like yogurt and kimchi can attack drug-resistant bacteria. In 2018, Collins and his team developed the engineered probiotic strategy. They tweaked a bacteria commonly found in yogurt called Lactococcus lactis to treat cholera.
Engineered bacteria can be trained to target pathogens when they are at their most vulnerable metabolic stage in the human gut. --José Rubén Morones-Ramírez.
More scientists followed with more experiments. So far, researchers have engineered various probiotic organisms to fight pathogenic bacteria like Staphylococcus aureus (leading cause of skin, tissue, bone, joint and blood infections) and Clostridium perfringens (which causes watery diarrhea) in test-tube and animal experiments. In 2020, Russian scientists engineered a probiotic called Pichia pastoris to produce an enzyme called lysostaphin that eradicated S. aureus in vitro. Another 2020 study from China used an engineered probiotic bacteria Lactobacilli casei as a vaccine to prevent C. perfringens infection in rabbits.
In a study last year, Ramírez’s group at the Autonomous University of Nuevo León, engineered E. coli to detect quorum-sensing molecules from Methicillin-resistant Staphylococcus aureus or MRSA, a notorious superbug. The E. coli then releases a bacteriocin that kills MRSA. “An antibiotic is just a molecule that is not intelligent,” says Ramírez. “On the other hand, engineered bacteria can be trained to target pathogens when they are at their most vulnerable metabolic stage in the human gut.”
Collins and Timothy Lu, an associate professor of biological engineering at MIT, found that engineered E. coli can help treat other conditions—such as phenylketonuria, a rare metabolic disorder, that causes the build-up of an amino acid phenylalanine. Their start-up Synlogic aims to commercialize the technology, and has completed a phase 2 clinical trial.
Circumventing the challenges
The bacteria-engineering technique is not without pitfalls. One major challenge is that beneficial gut bacteria produce their own quorum-sensing molecules that can be similar to those that pathogens secrete. If an engineered bacteria’s biosensor is not specific enough, it will be ineffective.
Another concern is whether engineered bacteria might mutate after entering the gut. “As with any technology, there are risks where bad actors could have the capability to engineer a microbe to act quite nastily,” says Collins of MIT. But Collins and Ramírez both insist that the chances of the engineered bacteria mutating on its own are virtually non-existent. “It is extremely unlikely for the engineered bacteria to mutate,” Ramírez says. “Coaxing a living cell to do anything on command is immensely challenging. Usually, the greater risk is that the engineered bacteria entirely lose its functionality.”
However, the biggest challenge is bringing the curative bacteria to consumers. Pharmaceutical companies aren’t interested in antibiotics or their alternatives because it’s less profitable than developing new medicines for non-infectious diseases. Unlike the more chronic conditions like diabetes or cancer that require long-term medications, infectious diseases are usually treated much quicker. Running clinical trials are expensive and antibiotic-alternatives aren’t lucrative enough.
“Unfortunately, new medications for antibiotic resistant infections have been pushed to the bottom of the field,” says Lu of MIT. “It's not because the technology does not work. This is more of a market issue. Because clinical trials cost hundreds of millions of dollars, the only solution is that governments will need to fund them.” Lu stresses that societies must lobby to change how the modern healthcare industry works. “The whole world needs better treatments for antibiotic resistance.”