An Explosive Material Based on Nanoparticles and DNA

Researchers have created an explosive composite material using nanoparticles and DNA. Aluminum and copper oxide put together are known to produce energy, but now by using nanoparticles of them their surface area can be increased, and by using DNA to link them together they can be made to self-assemble. DNA exists in organisms in two complementary strands tightly stuck together; these researchers took advantage of this by grafting individual DNA strands onto nanoparticles, mixing them up and letting the complementary DNA strands stick together.

From PhysOrg:

As a result, the complementary strands on each type of nanoparticle bind, turning the original aluminium and copper oxide powder into a compact, solid material which spontaneously ignites when heated to 410 °C (one of the lowest spontaneous ignition temperatures hitherto described in the literature).

If I’m not mistaken, spontaneous ignition here just means that it begins burning (combustion) without being “lit” by a flame or a spark. 

In addition to its low ignition temperature, this composite also offers the advantage of having a high energy density, similar to nitroglycerine: for the same quantity of material, it produces considerably more heat than aluminium and copper oxide taken separately, where a significant part of the energy is not released. In contrast, by using nanoparticles, with their large active surfaces, the researchers were able to approach the maximum theoretical energy for this exothermic chemical reaction.

The high energy density of this composite makes it an ideal fuel for nanosatellites, which weigh a handful of kilograms and are increasingly used. Such satellites are too light to be equipped with a conventional propulsion system once in orbit. However, a few hundred grams of this composite would give them sufficient energy to adjust their trajectory and orientation.

The composite could also have a host of terrestrial applications: ignitors for gas in internal combustion engines or for fuel in aircraft and rocket nozzles, miniature detonators, on-site welding tools, etc. Once its heat is turned into electrical energy, the composite could also be used as a back-up source for microsystems (such as pollution detectors scattered through the environment).

This article really caught my attention due, of course, to their use of DNA as a sort of glue. While the article explains why DNA works, and it seems like using DNA to bind nanoparticles is not a new idea, unfortunately it doesn’t explain why DNA is the best choice in this particular case. Double-stranded DNA normally comes apart at temperatures way below 410°C, which seems like it would be relevant here. 

In trying to find another article to explain the DNA thing, I found the one I just linked above (and here) about using DNA to form crystal lattices out of nanoparticles; you should check it out. Maybe this line of research will open up nanoparticles for wider use and greater self-assembly, which would probably be pretty revolutionary for all of us. 


Nanoparticle Exposure May Not Be An Issue After All

The study of nanoparticles is a growing field relevant to nanotechnology. Nanoparticles – tiny particles of a material, anywhere between 1 and 2500 nanometres in diameter – are particularly interesting because they can have different properties than the same material in larger quantities. They have size-dependent properties, because the proportion of atoms on a particle’s surface is non-negligible compared to the atoms inside the particle, unlike with larger objects. 

For example, from Wikipedia

Nanoparticles often possess unexpected optical properties as they are small enough to confine their electrons and produce quantum effects. For example gold nanoparticles appear deep red to black in solution. Nanoparticles of usually yellow gold and gray silicon are red in color. Gold nanoparticles melt at much lower temperatures (~300 °C for 2.5 nm size) than the gold slabs (1064 °C). And absorption of solar radiation in photovoltaic cells is much higher in materials composed of nanoparticles than it is in thin films of continuous sheets of material.

However, the unusual properties of nanoparticles means, naturally, that they could be harmful to human health in some way. This has been a worry for some time now as nanotechnology has risen to prominence. In what seems like a big relief, a new study shows that we may actually be exposed to nanoparticles all the time, so if they have any dangerous effects, we should already know about them.

From ScienceDaily:

Since the emergence of nanotechnology, researchers, regulators and the public have been concerned that the potential toxicity of nano-sized products might threaten human health by way of environmental exposure.

Now, with the help of high-powered transmission electron microscopes, chemists captured never-before-seen views of miniscule metal nanoparticles naturally being created by silver articles such as wire, jewelry and eating utensils in contact with other surfaces. It turns out, researchers say, nanoparticles have been in contact with humans for a long, long time…

Using a new approach developed at [the University of Oregon] that allows for the direct observation of microscopic changes in nanoparticles over time, researchers found that silver nanoparticles deposited on the surface of their SMART Grids electron microscope slides began to transform in size, shape and particle populations within a few hours, especially when exposed to humid air, water and light. Similar dynamic behavior and new nanoparticle formation was observed when the study was extended to look at macro-sized silver objects such as wire or jewelry.

“Our findings show that nanoparticle ‘size’ may not be static, especially when particles are on surfaces. For this reason, we believe that environmental health and safety concerns should not be defined — or regulated — based upon size,” said James E. Hutchison, who holds the Lokey-Harrington Chair in Chemistry. “In addition, the generation of nanoparticles from objects that humans have contacted for millennia suggests that humans have been exposed to these nanoparticles throughout time. Rather than raise concern, I think this suggests that we would have already linked exposure to these materials to health hazards if there were any.”

Any potential federal regulatory policies, the research team concluded, should allow for the presence of background levels of nanoparticles and their dynamic behavior in the environment.

So that’s good news. Nanotechnologists, nanotechnology away!

“Nanoparticles Seek and Destroy Glioblastoma in Mice”

Researchers created a nanosystem comprised of a nanoparticle and two peptides that can travel through the bloodstream selectively to cancerous cells and kill them. Apparently it was able to cure 9/10 glioblastoma-suffering mice on which it was tested (in one of the two models they tested). 

Glioblastoma is a type of relatively prevalent and very dangerous brain cancer, involving glia, a type of brain cell that plays Robin to neurons’ Batman. Glia are thought of as support cells to neurons, which do the actual signaling in the nervous system. There are about the same number of glia in the human nervous system as there are neurons. 

Peptide is a term for a series of amino acids not quite big enough to be called a protein. Amino acids are small molecules that are the building blocks of proteins, but their naming conventions have always been a bit arbitrary to me (and to my relief Wikipedia agrees): two amino acids form a dipeptide, more are a polypeptide, anything in that arena is a peptide, and longer sequences are a protein, or subunits of a protein (sometimes proteins are formed by a bunch of amino acid sequences coming together like Voltron). In short, peptide just means a molecule made up of the same stuff as proteins. 

From Science Daily:

Rather than presenting as a well-defined tumor, glioblastoma will often infiltrate the surrounding brain tissue, making it extremely difficult to treat surgically or with chemotherapy or radiation. Likewise, several mouse models of glioblastoma have proven completely resistant to all treatment attempts. In a new study, a team led by scientists at Sanford-Burnham Medical Research Institute (Sanford-Burnham) and the Salk Institute for Biological Studies developed a method to combine a tumor-homing peptide, a cell-killing peptide, and a nanoparticle that both enhances tumor cell death and allows the researchers to image the tumors.

The nanosystem developed in this study is made up of three elements. First, a nanoparticle acts as the carrier framework for an imaging agent and for two peptides (short proteins). One of these peptides guides the nanoparticle and its payload specifically to cancer cells and the blood vessels that feed them by binding cell surface markers that distinguish them from normal cells. This same peptide also drives the whole system inside these target cells, where the second peptide wreaks havoc on the mitochondria, triggering cellular suicide through a process known as apoptosis.

Together, these peptides and nanoparticles proved extremely effective at treating two different mouse models of glioblastoma. In the first model, treated mice survived significantly longer than untreated mice. In the second model, untreated mice survived for only eight to nine weeks. In sharp contrast, treatment with this nanosystem cured all but one of ten mice. What’s more, in addition to providing therapy, the nanoparticles could aid in diagnosing glioblastoma; they are made of iron oxide, which makes them — and therefore the tumors they target — visible by MRI, the same technique already used to diagnose many health conditions.

Using iron to make specific cells visible to MRI – sounds familiar, no? I wonder if that other group had considered using a nanoparticle delivery system to track neuroblasts; I imagine it’s more of a short-term solution though, compared to the long-term tracking they achieve through gene therapy, and it’s unclear if neuroblasts could be identified by a comparable system in any case. 

They mentioned mitochondria: a mitochondrion is the organelle (cellular subunit) where energy is basically produced from sugar and oxygen. The cell needs it for energy, so if a cell’s mitochondria get knocked out (as they do by this nanosystem), the cell is toast and will destroy itself in an orderly fashion, called apoptosis

In a final twist, the researchers made the whole nanosystem even more effective by administering it to the mice in conjunction with a third peptide. Dr. Ruoslahti and his team previously showed that this peptide, known as iRGD, helps co-administered drugs penetrate deeply into tumor tissue. iRGD has been shown to substantially increase treatment efficacy of various drugs against human breast, prostate, and pancreatic cancers in mice, achieving the same therapeutic effect as a normal dose with one-third as much of the drug. Here, iRGD enhanced nanoparticle penetration and therapeutic efficacy.

So, this is cool. However, it seems like their main focus was on whether or not, and for how long, the mice survived – a good starting point, for sure, but not nearly enough to show that this system is effective. There’s nothing to show that this system is actually specific – that it’s not also killing the healthy cells around the cancerous cells. That might require a different approach – maybe cutting up the mice brains afterwards, checking for extraneous damage and whatnot. If it kills tumors but causes severe brain damage… well, hell, it’s still probably better than the alternative, but it has to be known. 

My final question is whether or not glioblastoma is the only type of cancer that has easily-identifiable cancer cells (to a nanosystem). Is this a potential solution to a particular type of cancer, or to a broad swath of it? I’m guessing they’d be the first to pronounce if it was the latter case, but in any case we can still hope more advancements like this are made in the future; it sounds promising.

“Nanorockets could deliver drugs inside the body”

I don’t think I can summarize this brief article any better than their title. From New Scientist:

NANOROCKETS powered by a benign rocket fuel could one day carry drugs around the body…

Samuel Sanchez and colleagues at the Leibniz Institute for Solid State and Materials Research in Dresden, Germany, made nanotubes by rolling platinum-coated sheets of metal into tubes with the platinum on the inside.

When the team placed the tubes in a warm, weak solution of hydrogen peroxide, the platinum catalysed the decomposition of peroxide into water and oxygen. This forced bubbles of gas out of one end of the tube, generating thrust in the opposite direction…

The result is a nanorocket that travels up to 200 times its own length per second, faster than the quickest bacteria. The team can steer the tubes using a magnetic field and control the speed by varying the temperature of the fluid…

This is one of the few engines that can operate in blood, urine or saliva, says Joseph Wang, a nano-engineer at the University of California, San Diego.

My first question, naturally, is why you’d want a nanorocket to deliver drugs. Is good old blood too old-fashioned now? They’re working on making the fuel less toxic, but could the thrust itself be dangerous, piercing cell membranes? This article is short on context and unfortunately apparently the only article on this research. Nevertheless, it’s an interesting concept on its own.

I somehow don’t see nanorocket drug delivery systems as becoming common, but if they do, you saw it here first!

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