Summary: Nanodocs are medical nanorobots that work from inside like a tiny doctor. The authors of a recent research study say we may be able to swallow the doctor sooner than we think. Once considered science fiction, the ability to “swallow the surgeon” – using medical nanobots to diagnose and treat disease from inside the body – is becoming a reality. The study authors highlight recent advances in nanotechnology tools, such as nanodrillers, microgrippers, and microbullets – and show how nanodocs have tremendous potential in the areas of precision surgery, detection, detoxification and targeted drug delivery. [Cover photo: The old way to swallow the surgeon. Credit: R. Collin Johnson / Attributed to Stanford University.]
Imagine that you need to repair a defective heart valve, a major surgery. Instead of ripping your chest cut open, a doctor merely injects you with a syringe full of medical nanorobots, called nanodocs for short. You emerge from the ‘surgery’ unscathed, and your only external wound is the puncture hole from the injection.
According to a recent study published by nanorobotic engineers at the University of California San Diego (UCSD), the concept of ‘swallow the doctor’ may be closer to reality than we think.
Jinxing Li and a team of nanorobotic engineers at UCSD’s Department of NanoEngineering published their findings in the journal Science Robotics, highlighting the significant advances in medical nanorobots over the past few years. According to the authors of the study, called the nanodoc review for short,
“Designing miniaturized and versatile robots of a few micrometers or less would allow access throughout the whole human body, leading to new procedures down to the cellular level and offering localized diagnosis and treatment with greater precision and efficiency”
Challenges of Being a Nanodoc
The authors of the nanodoc review listed the main challenges involved in making nanodocs, including propulsion, navigation and a power source.
Nanodocs Need Steady Hands
Most of us think of blood as a fluid. However, the nanodoc has a different point of view. When you get down to the nanoscale world, blood becomes a thick sludge. Nanobots can’t rely on inertia, so gliding is out of the question. Being at the nanoscale means they are also subject to Brownian motion—constant bombardment by other molecules in their environment. This causes the nanodoc to move like a drunken sailor. Little guys always get pushed around the most.
If you swallow the surgeon, make sure that you have one with steady hands.
Yes, some nanodocs do have hands. More on that later.
Nanodocs on the Move
Nanodocs can’t swim in the way larger critters do, and from the perspective of a nanodoc, every other organism is bigger. To overcome the limitations of being overly small, nanodoc engineers have developed novel propulsion and navigation strategies for the medical nanorobots. Nanodoc engineers drew inspiration from the microbiology world and copied the propulsion systems of the micro-organisms that share their environments, such as bacteria and human cells.
Powering a nanodoc is also difficult. And conventional batteries can’t be scaled down to the nano-level. Instead, nanodoc engineers have created chemically-powered motors that use fuels found in their environment. Nanodoc engineers also employ external power sources, such as magnetic fields and ultrasound.
Four Ways To Swallow the Doctor (Four Uses of Nanodocs)
According to the authors of the nanodoc review article, medical nanorobots provide us with four potential ways to swallow the doctor, including Precision Surgery, Sensing & Detection, Detoxification, and Targeted Drug Delivery
1. Nanodocs in Precision Surgery (Swallow the Surgeon)
The ability to swallow the doctor does more than just reduce the invasiveness of medical procedures. Nanodocs can go where no doctor has gone before. According to the authors of the nanodoc review,
“With dimensions compatible with those of the small biological entities that they need to treat, micro/nanorobots offer major advantages for high-precision, minimally invasive surgery.” Adding “Unlike their large robotic counterparts, these tiny robots can navigate through the body’s narrowest capillaries and perform procedures down to the cellular level.”
After we swallow the doctor, nanodocs can operate in hard-to-reach locations and carry out medical procedures at the cellular level. According to the authors of the nanodoc review, several advances in medical nanorobots will make the dream of “swallow the doctor” a reality, including nanodrillers, microgrippers, and microbullets.
Swallow a Surgeon with a Good Pair of Microgrippers
A skilled surgeon’s greatest asset is his hands. Before we can swallow the surgeon, we have to make sure our nanodoc has a decent pair of hands. Nanoengineers have found a solution to the handless surgeon problem by developing a class of nanodocs called microgrippers who “can capture and retrieve tissues and cells.”
Tethered and larger sized versions of these tools are nothing new, however, suffer from the drawback of being comparatively large. Furthermore, the tethered version are not autonomous and require a mechanical or electrical tether, making it difficult to swallow the surgeon.
Thanks to nanotechnology, that’s about to change. According to the authors of the nanodoc review article, advances in materials science is making an untethered version possible. The new microgrippers are self-folding so that they can close around the target tissue and. They don’t require external intervention, as they can be triggered by environmental cues such as temperature or pH.
Nanodocs With a Magnetic Personality
The UCSD authors also hold that surgical procedures can be performed using Magnetically–controlled nanodocs because magnetic fields can penetrate thick tissue. Magnetic nanodocs have already proved their merit, having been successfully tested on laboratory animals. For example, Doctors in Canada have successfully tested magnetically controlled nanodocs to treat cancers in mice. The doctors created the nanodoc using magnetic bacteria. The bacteriobot has been a success in animal trials, and a doctor in Montreal is planning to use them on cancer patients. In another example, Nanodoc engineers used magnetically controlled nanodocs to carry out surgery inside a living rabbit’s eye.
Nanodocs Armed With Microbullets
While magnetism is the favored tool of the nanoengineers, ultrasonically-controlled nanodocs are also on the horizon. Researchers use ultrasound to trigger so-called microbullets that penetrate deep into diseased tissue. Propelled by vaporizing a biocompatible fuel, enabling microbullets to reach speeds of six meters per second.
Researchers use ultrasound to trigger so-called microbullets that penetrate deep into diseased tissue. Propelled by vaporizing a biocompatible fuel, enabling microbullets to reach speeds of six meters per second.
Nanodocs With Nanodrillers
Microbullets aren’t the only trick up the nanoengineers sleeve. Enterprising nanoengineers have developed prototype nanodrillers to penetrate cells and tissues. powered by chemical fuels. Nanodrillers burrow deep into tissues using a corkscrew motion.
Powered by chemical fuels, nanodrillers burrow deep into tissues using a corkscrew motion.
2. Sensing Nanodocs
A medical doctor performs two key tasks: she detects diseases and then treats them. While nanodocs are pretty good at treating diseases, they need to add a way to detect disease tissue to be truly effective. Nanoengineers have solved that problem, by adding sensing mechanisms in the form of bioreceptors, including cells, proteins, and nucleic acids.
Example of Sensing Nanodoc
Using the bacteriobots as an example, the test of nanodocs guided by magnetic fields and built-in low oxygen sensors was a stellar success. The Canadian engineers designed their particular flavor of nanodoc by modifying existing bacteria that naturally swim along magnetic field lines. As well, the Canadian bacteriobots builders engineered their bacteria to sense and seek out low oxygen environments. Cancers create more energy than healthy tissue and therefore tend to live in low oxygen neighborhoods.
Despite their tails, the Canadian bacteriobots aren’t self-guided all the way. After inserting the bacteria based nanodocs, surgeons use magnetic fields to guide the bacteria based nanodocs to the general location of the tumor, after which the bacteriobots are on their own. Relying on their low oxygen sensors, the bacteria-based nanodocs burrow deep into tumors where they deliver a lethal payload of cancer drugs.
3. Nanodocs for Detoxification
Using their keen sensing capabilities, nanodocs can also remove toxins from a diseased tissue. Nanodoc engineers discovered that when they attached a bioreceptor to a constantly moving nanomotor, and the resulting nanodevice collides with its target molecule far faster than if it was merely floating free. Nanoengineers can utilize this principle to create a self-mixing solution. These nanodevices are powerful enough to both detect and transport target cells, while others are small enough to operate inside cells, creating the possibility that nanodocs can repair structures inside the cell, including damaged mitochondria.
The Organic Trend in Nanodocs
While people think of a nanorobot as one based on tiny wires and metals, the trend these days is a move towards organic machines based on molecular nanotechnology or perhaps a combination of both organic and inorganic to create hybrid nanodocs.
Not all nanodocs are created from scratch. Sometimes it pays just to take a living organism, such as a bacteria, virus or human cell and customize it into a nanodoc. For example, red blood cells are excellent toxin-absorbing nanosponges. Nanoengineers have combined red blood cells with nanomotors to create nanodocs capable of absorbing and neutralizing toxins.
4. Nanodocs Provide Targeted Drug Delivery
Using nanotechnology in drug delivery is nothing new. In fact, drug delivery was one of the first applications of nanotechnology back in the early 1990’s. The problem is that most existing nano-based drug delivery treatments lack self-propulsion. Old school nanomedicine merely relied on the body’s natural circulatory system to get medicine where it needs to go. Everyone knows that doctors are impatient, and have invented self-propelled nanodocs that get drugs to their destination faster and more accurately. In this way, medical nanorobots are more effective and reduce side effects from powerful drugs.
Nanoengineers like to propel nanodocs using chemical nanomotors. These tiny engines break down a chemical fuel and create bubbles that propel them. The drawback to this approach is that the fuel has to be carried along with the nanomotor, or added to the environment. The UCSD nanoengineers pointed out that, to date, most of these studies using chemical nanomotors are successful only in a test tube. The goal, of course, is to have successful nanomotors that operate in living organisms, preferably the two-legged living organisms that have ample medical insurance. Another drawback is that the current crop of nanomotors relies on hydrogen peroxide, a toxin, as a fuel. And have the potential to poison the patient if their fuel tanks were to rupture inside the body
According to the authors of the nanodoc review article, the outlook for chemical nanomotors is becoming brighter as nanoengineers are conducting experiments with chemical nanomotors on living organisms, just not the insurance-card carrying two-legged kind. Nanoengineers report promising results including the development of synthetic motors powered by biological fluids such as water or gastric acid. The chemical nanomotors developed thus far tend to decompose into non-toxic compounds, making them the ideal workhorse. After having done their job, they self-destruct, saving doctors the trouble of having to retrieve them.
Because of recent advances in nanotechnology tools, such as nanodrillers, microgrippers, and microbullets we are poised to we can swallow the surgeon, and use medical nanobots to diagnose and treat disease from inside the body. Nanodocs have tremendous potential in the areas of precision surgery, detection, detoxification and targeted drug delivery.
Despite the many challenges, nanodoc engineers have successfully demonstrated a variety of medical nanorobots that can navigate through complex biological environments. These prototype nanodocs have been able to remove biopsy samples, deliver drugs and even diagnose diseases.
Nanoengineers add functionalities to nanomaterials by interfacing them with biological molecules or structures. Nanomaterials have a size similar to most biological molecules and structures; therefore they can be used inside the body, even down to the level of a human cell. By combining nanomaterials with biology, clever nanodoc engineers have developed nanoscale diagnostic devices, contrast agents, analytical tools, and drug delivery vehicles.
Related Articles on Nanodocs
Two types of medical nanobot possess many of the above characteristics and one of them, the bacteriobot, is poised to enter clinical trials.
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Richard Feynman, “There’s Plenty of Room at the Bottom.” Lecture at American Physical Society meeting. December 29, 1959. Full Text.
Jinxing Li, Berta Esteban-Fernández de Ávila, Wei Gao, Liangfang Zhang and Joseph Wang. “Micro/nanorobots for biomedicine: Delivery, surgery, sensing, and detoxification,” Science Robotics 01 Mar 2017. Vol. 2, Issue 4, eaam6431. DOI: 10.1126/scirobotics.aam6431
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