Month: December 2018

Over the course of this blog, I have delved into many concepts involving nano and microparticles and their potential applications in the field of nanorobotics. Despite the vast range of particulate systems that I have previously mentioned, all come from one of four fundamental structural material types: metals, ceramics, glasses, and polymers. In my final blog post, I will discuss how these materials can be combined to form composite nanoparticulate systems, where the constituent materials retain their identities, each adding to the overall properties of the “composite nanoparticle.”

Composites can be broadly sorted into two categories: Fiber Reinforced Composites and Aggregate Composites. A composite nanoparticle is generally defined as a nanoparticle of composite structure characterized by a core-shell structure, onion-like structure of multiple materials.

In a paper titled Multifunctional Composite Nanoparticles: Magnetic, Luminescent, and Mesoporous, Lin et al. suggest that nanocomposite materials with unique magnetic and luminescence properties have great potential in biological applications such as MRI contrast, drug delivery, cell sorting, and labeling. They focus on the synthesis of mesoporous silica nanoparticles, characterized by their uniquely high surface area, large pore volume, uniform pore size, and low cytotoxicity, combined with gadolinium. Such a composite nanoparticle, they demonstrated, was quite useful as an MRI contrast. They theorize that further modifications with polymer constituents and other metals would give the mesoporous silica nanoparticles even more unique characteristics suited to other biomedical applications.

Researchers agree that leveraging the properties of metals, ceramics, glasses, and polymers at the nanoscale lends nanoparticulate systems a wide variety of applications as catalysts (with huge activity and specificity), metal-semiconductor junctions, drug carriers, optical sensors, and modifiers of polymeric films for packaging.

Composite nanoparticles present a great opportunity to leverage all that we know about nanoparticles of the four fundamental structural material types – metals, ceramics, glasses, and polymers – to create novel nanomaterials and robots to carry out ever more complex and useful tasks.

 

References:

https://link.springer.com/referenceworkentry/10.1007%2F978-0-387-48998-8_243

https://www.hindawi.com/journals/jchem/2013/536341/

https://pubs.acs.org/doi/pdf/10.1021/cm061976z

https://link.springer.com/article/10.1007/s11051-016-3374-5

Metals, Stents, and Nanobots

Atherosclerosis – caused by the deposition of fat, cholesterol, calcium and other substances on the inner walls of the arteries – is the process by which blood vessels harden and narrow. It is a major medical issue that limits the ability of oxygen-rich blood to reach vital organs, thereby increasing an individual’s risk of heart attack or stroke.

In the past, physicians have used angioplasty or bypass surgery to either break up or circumvent the occluding plaque, but these methods have not always effective and are far from ideal. Currently, drug-eluting stents, self-expanding stents, and stents of various novel components (like magnesium for example) represent the cutting edge in atherosclerosis treatment (and as such are being heavily researched by scientists hoping to make a leap forward in the treatment of this disease).

Interestingly, “nanobots” have also been deployed to deal with serious medical threat. In 2015, a research team based in Drexel University demonstrated that they had created a micro-robotic technology capable of drilling through plaque buildup in clogged arteries. The micro-robots they discuss take the form of small microbeads with the ability to join together and form a corkscrew-like structure. These robots are made up of tiny iron oxide beads, with an average diameter of 400 nanometers, joined together in a long chain. Importantly, the Drexel researchers have reported that these beads are “composed of inorganic, biocompatible materials that will not trigger an immunological response.”

The exciting capability of these micro-robots is revealed when the beads are exposed to a magnetic field. When a bead chain is exposed to a finely tuned external magnetic field, they can be induced to move through the bloodstream. The rotation of a finely tuned magnetic field causes the bead chain to form a spinning helical structure that propels itself through the bloodstream. The properties of the aforementioned magnetic field control the speed, direction, and size of the chain, thus affecting the force with which it moves. After being injected into the body via catheter and manipulated by the magnetic field, these drill-like micro-robots can be directed to the site of an arterial occlusion. Upon deployment, the bead chains will drill into plaque buildups, loosening them. The plaques can then be finished off by a small surgical drill delivered via catheter to the site of the occlusion. After the surgery, the biodegradable beads release anticoagulant drugs into the bloodstream to help prevent future plaque buildup at the site.

The use of magnetic fields to transform metal micro-bead chains into small spinning drills is an incredibly novel idea. It represents the creativity necessary to develop nano- and micro-robots into effective therapeutic tools capable of making a difference in patient’s lives.

 

References

https://www.smithsonianmag.com/innovation/tiny-robots-can-clear-clogged-arteries-180955774/

https://www.sciencealert.com/graphene-based-nanobots-could-clean-up-the-metal-from-our-oceans