One of the advantages of nanotech treatments for cancer is that nanoparticles can be large enough to introduce more than one type of therapeutic molecule into the same cancer cell. Another advantage is that nanoparticles can protect and deliver into cells molecules that would never make it into the cancer cell unassisted. Now scientists at Pennsylvania State University have demonstrated that nanoparticles can introduce two very promising, but easily degraded, therapeutic molecules into a laboratory model of human skin, and that together they are much more effective than either is alone is slowing the development of deadly melanoma skin cancer. From the National Cancer Institute’s Alliance for Nanotechnology in Cancer “Nanoparticles Target Multiple Cancer Genes, Shrink Tumors More Effectively“:

Nanoparticles filled with small interfering RNA (siRNA) molecules targeting two genes that trigger melanoma have shown that they can inhibit the development of melanoma, the most dangerous type of skin cancer. The nanoparticles, administered in conjuction with ultrasound irradiation, exerted their effects only on malignant tissue, leaving healthy tissue alone.

“It is a very selective and targeted approach,” said Gavin Robertson, Ph.D., who led the team of researchers from the Penn State College of Medicine. “And unlike most other cancer drugs that inadvertently affect a bunch of proteins, we are able to knock out single genes.”

The Penn State researchers speculated that siRNA could turn off the two cancer-causing genes and potentially treat the deadly disease more effectively. “siRNA checks the expression of the two genes, which then lowers the abnormal levels of the cancer causing proteins in cells,” explained Dr. Robertson. This research appears in the journal Cancer Research [abstract].

In recent years, researchers have zeroed in on two key genes—B-Raf and Akt3—that play key roles in the development of melanoma. Mutations in the B-Raf gene, the most frequently mutated gene in melanoma, lead to the production of a mutant form of the B-Raf protein, which then helps mole cells survive and grow. B-Raf mutations alone, however, do not trigger melanoma development. That event requires a second protein, called Akt3, that regulates the activity of the mutated B-Raf, which aids the development of melanoma. The siRNA agents used in this study specifically target Akt3 and the mutant B-Raf and therefore do not affect normal cells.

However, although knocking out specific genes may seem like a straightforward task, delivering the siRNA drug to cancerous cells is another story, because not only do protective layers in the skin keep drugs out but also chemicals in the skin quickly degrade the siRNA. To clear these two hurdles, Dr. Robertson and his team engineered lipid-based nanoparticles that can incorporate siRNA into their hollow interiors. The researchers then used a portable ultrasound device to temporarily create microscopic holes in the surface of the skin, allowing the drug-filled particles to leak into tumor cells beneath.

When the researchers exposed lab-generated skin containing early cancerous lesions to the treatment 10 days after the skin was created, the siRNA reduced the ability of cells containing the mutant B-Raf to multiply by nearly 60 to 70 percent and more than halved the size of lesions after 3 weeks. “This is essentially human skin with human melanoma cells, which provides an accurate picture of how the drug is acting,” said Dr. Robertson.

—Jim

Organisms that live in extreme environments may provide building blocks for nanotech applications that need to withstand extreme environments. A virus that infects a microorganism that lives in volcanic springs looks particularly promising. From Norwich BioScience Institutes, via AAAS EurekAlert “Extreme nature helps scientists design nano materials“:

Scientists are using designs in nature from extreme environments to overcome the challenges of producing materials on the nanometre scale. A team from the UK’s John Innes Centre, the Scripps Research Institute in California and the Institut Pasteur in Paris have identified a stable, modifiable virus that could be used as a nanobuilding block.

Viral nanoparticles (VNPs) are ideally sized, can be produced in large quantities, and are very stable and robust. They can self-assemble with very high precision, but are also amenable to modification by chemical means or genetic engineering.

Some applications of VNPs require them to withstand extremely harsh conditions. Uses in electrical systems may expose them to high temperatures, and biomedical uses can involve exposure to highly acidic conditions. VNPs able to remain functional in these conditions are therefore desirable. The team identified viruses from the hot acidic sulphurous springs in Iceland. One of these, SIRV2, was assessed for its suitability for use as a viral nanobuilding block.

SIRV2 is a virus that infects Sulfolobus islandicus, a single-celled microorganism that grows optimally at 80°C and at pH 3, and it was also able to withstand other harsh environments created in the laboratory. This shows that the rigid, rod-shaped SIRV2 virus capsule must be very stable, an important characteristic for use as a nanobuilding block. To be potentially useful as a VNP, the viral capsule also needs to be open to modification or decoration with functional chemical groups.

The researchers found that, depending on the chemistry used, modifications could be targeted specifically to the ends of the virus particle, to its body, or both. This spatially controlled modification is unique to this VNP, and opens up new possibilities when the nanobuilding blocks are built up into arrays or layers. Since the virus body and ends can be selectively labelled it is expected that arrays with different physical properties can be fabricated, for example by aligning particles body-to-body versus self-assembly end-to-end. This option is not possible with other rod-shaped VNPs.

“Future applications may be found in liquid crystal assembly, nanoscale templating, nanoelectronic and biomedical applications.” said Dr Dave Evans of the John Innes Centre.

“Further studies towards the development of these VNPs for materials are currently underway”, said Dr Nicole F. Steinmetz of the Scripps Research Institute. “We are looking into the use of the particles to generate complex structures such as rings or tetrapods”.

The research was published in the journal Advanced Functional Materials [abstract].
—Jim

On 5 June 2008, Robert Freitas and Ralph Merkle of the Institute for Molecular Manufacturing (IMM) submitted to IEEE Spectrum the following response to the article “Rupturing the Nanotech Rapture” by Richard A.L. Jones (IEEE Spectrum, June 2008 issue). Their brief letter is reproduced below because Spectrum has chosen to publish only one of the responses it received on this topic.

Several items that Richard Jones mentions are well-known research challenges, not showstoppers. All have been previously identified as such along with many other technical challenges not mentioned by Jones that we’ve been aware of for years. Unfortunately, the article also evidences numerous confusions: (1) The adhesivity of proteins to nanoparticle surfaces can (and has) been engineered; (2) nanorobot gears will reside within sealed housings, safe from exposure to potentially jamming environmental bioparticles; (3) microscale diamond particles are well-documented as biocompatible and chemically inert; (4) unlike biological molecular motors, thermal noise is not essential to the operation of diamondoid molecular motors; (5) most nanodiamond crystals don’t graphitize if properly passivated; (6) theory has long supported the idea that contacting incommensurate surfaces should easily slide and superlubricity has been demonstrated experimentally, potentially allowing dramatic reductions in friction inside properly designed rigid nanomachinery; (7) it is hardly surprising that nanorobots, like most manufactured objects, must be fabricated in a controlled environment that differs from the application environment; (8) there are no obvious physical similarities between a microscale nanorobot navigating inside a human body (a viscous environment where adhesive forces control) and a macroscale rubber clock bouncing inside a clothes dryer (a ballistic environment where inertia and gravitational forces control); and (9) there have been zero years, not 15 years, of “intense research” on diamondoid nanomachinery (as opposed to “nanotechnology”). Such intense research, while clearly valuable, awaits adequate funding — as is now just beginning.

Robert A. Freitas Jr.
Ralph C. Merkle
Institute for Molecular Manufacturing (www.imm.org)

—Jim

To develop nanotech therapies for cancer, it would be useful to be able to follow the distribution of nanoparticles in the patient to see if they are in fact accumulating in the targeted tumor(s). A noninvasive Raman microscope has allowed scientists to track carbon nanotubes injected into living mice. From the National Cancer Institute’s Alliance for Nanotechnology in Cancer “Seeing Nanotubes Targeting Tumors In Vivo“:

Carbon nanotubes have significant potential for delivering both imaging and therapeutic agents to tumors, but there is still a need to better quantify how well these rolled-up sheets of graphite can target tumors. Now, thanks to the development of a microscope capable of measuring Raman spectroscopic signals from living mice, researchers have a noninvasive tool to study where carbon nanotubes travel once they are injected into the blood stream.

Reporting its work in the journal Nano Letters [abstract], a team of investigators led by Sanjiv Gambhir, M.D., Ph.D., principal investigator of the Center for Cancer Nanotechnology Excellence Focused on Therapy Response (CCNE-TR), based at Stanford University, and Hongjie Dai, Ph.D., also a member of the CCNE-TR, described its use of an optimized Raman microscope to track two different sets of carbon nanotubes as they transited through the body of living mice. One of the nanotubes was covered with the tumor-targeting peptide known as RGD; the other set was used without any added functionality.

…Using this Raman microscope, the investigators were able to track differences in nanotube trafficking between the targeted and untargeted nanotubes. Although both sets of nanotubes showed an initial spike in tumor accumulation, the concentration of untargeted nanotubes in tumors began dropping as early as 20 minutes after injection. In contrast, the tumor concentration of the targeted nanotubes remained elevated for at least 72 hours after injection. In animals treated with the targeted nanotubes, tumors were readily visible as early as 2 hours postinjection and for at least 72 hours.

Not mentioned in either the NCI article or in the abstract is the question of how deep inside the body tissues can be imaged by the Raman microscope. If the microscope can penetrate a couple centimeters, for example, essentially all of a mouse but only the outermost tissue of a human could be imaged.
—Jim