Stabilizing entangled spaghetti-like materials: Controling forces between oppositely charged polymers opens new route for gene therapy vectors

Gene therapy can only be effective if delivered by a stable complex molecule. Now, scientists have determined the conditions that would stabilise complex molecular structures that are subject to inherent attractions and repulsions triggered by electric charges at the surfaces of the molecules, in a study about to be published in the European Physical Journal E, by Valentina Mengarelli and her colleagues from the Solid State Physics Laboratory at the Paris-Sud University in Orsay, France, in collaboration with Paris 7 and Évry Universities scientists.

The authors studied soluble complexes made of negatively charged DNA or another negatively charged polymer -- polystyrene-sulfonate (PSSNa) -- and a so-called condensation agent, which is a negatively charged polymer, known as linear polyethyleneimine (PEI). PEI participates in the condensation process by tying onto a molecule such as DNA, like tangled hair, to form an overall positively charged DNA/polymer complex structure. Previous research focused mainly on non-soluble complexes, while the few attempts at focusing on soluble complexes dealt either with smaller polymers or those with a weaker electric charge, which may therefore be easier to stabilise.

The French team thus confirmed experimentally that the complexation process does not depend on the rigidity of the original molecule, be it DNA or PSSNa, but on the positive/negative electric charge ratio and on the polymer concentrations. It is the interactions between electrically charged parts within the complex that govern its properties. When the condensation agent is in excess, the positively charged complex is then attracted to negatively charged biological cell membranes. This could be used to deliver the DNA into a targeted cell nucleus as part of gene therapy treatment.Future work will focus on using long DNA molecules and novel polymers to form complexes of controlled size and electric charge for gene therapy.

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The above story is reprinted from materials provided by Springer.

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Journal Reference:

Mengarelli V, Auvray L, Pastré D, and Zeghal M,. Charge inversion, condensation and decondensation of DNA and Polystyrene sulfonate by polyethylenimine. European Physical Journal E (EPJE), 2011; 34, 127 DOI: 10.1140/epje/i2011/11127-3

Genetically engineered spider silk for gene therapy

 Genetically engineered spider silk could help overcome a major barrier to the use of gene therapy in everyday medicine, according to a new study that reported development and successful initial laboratory tests of such a material. It appears in ACS' journal Bioconjugate Chemistry.

David Kaplan and colleagues note that gene therapy — the use of beneficial genes to prevent or treat disease — requires safe and efficient carriers or "vectors." Those carriers are the counterparts to pills and capsules, transporting therapeutic genes into cells in the body. Safety and other concerns surround the experimental use of viruses to insert genes. The lack of good gene delivery systems is a main reason why there are no FDA-approved gene therapies, despite almost 1,500 clinical trials since 1989. The new study focused on one promising prospect, silk proteins, which are biocompatible and have been used in everyday medicine and medical research for decades.

The scientists describe modifying spider silk proteins so that they attach to diseased cells and not healthy cells. They also engineered the spider silk to contain a gene that codes for the protein that makes fireflies glow in order to provide a visual signal (seen using special equipment) that the gene has reached its intended target. In lab studies using mice containing human breast cancer cells, the spider-silk proteins attached to the cancer cells and injected the DNA material into the cells without harming the mice. The results suggest that the genetically-engineered spider-silk proteins represent "a versatile and useful new platform polymer for nonviral gene delivery," the article notes.

More information: “Spider Silk-Based Gene Carriers for Tumor Cell-Specific Delivery” Bioconjugate Chem., Article ASAP. DOI: 10.1021/bc200170u

Abstract
The present study demonstrates pDNA complexes of recombinant silk proteins containing poly(l-lysine) and tumor-homing peptides (THPs), which are globular and approximately 150–250 nm in diameter, show significant enhancement of target specificity to tumor cells by additions of F3 and CGKRK THPs. We report herein the preparation and study of novel nanoscale silk-based ionic complexes containing pDNA able to home specifically to tumor cells. Particular focus was on how the THP, F3 (KDEPQRRSARLSAKPAPPKPEPKPKKAPAKK), and CGKRK, enhanced transfection specificity to tumor cells. Genetically engineered silk proteins containing both poly(l-lysine) domains to interact with pDNA and the THP to bind to specific tumor cells for target-specific pDNA delivery were prepared using Escherichia coli, followed by in vitro and in vivo transfection experiments into MDA-MB-435 melanoma cells and highly metastatic human breast tumor MDA-MB-231 cells. Non-tumorigenic MCF-10A breast epithelial cells were used as a control cell line for in vitro tumor-specific delivery studies. These results demonstrate that combination of the bioengineered silk delivery systems and THP can serve as a versatile and useful new platform for nonviral gene delivery.

Provided by American Chemical Society (news : web)

Compound may provide drug therapy approach for Huntington's disease

UT Southwestern Medical Center researchers have identified compounds that appear to inhibit a signaling pathway in Huntington's disease, a finding that may eventually lead to a potential drug therapy to help slow the progression of degenerative nerve disorders.

"Our studies have uncovered a new therapeutic target for Huntington's disease treatment and possibly for other neurodegenerative diseases," said Dr. Ilya Bezprozvanny, professor of physiology and senior author of the study, published in today's issue of Chemistry and Biology. "In addition, we now have this new series of compounds that gives us a tool to study the pathogenesis of Huntington's disease."

Huntington's disease is a fatal genetic disorder in which certain brain cells waste away. More than 250,000 people in the U.S. have the disorder or are at risk for it. The most common form is adult-onset, with symptoms usually developing in patients in their mid-30s and 40s.

The disease results in uncontrolled movements, psychiatric disturbance, gradual dementia and eventually death. There is no therapy available currently to slow the progression of the disease.

Scientists at UT Southwestern found that quinazoline-derived compounds effectively block what is known as the store-operated calcium entry signaling pathway, which was never before implicated in Huntington nerve cells but that might be a therapeutic target in the disease.

Dr. Bezprozvanny's laboratory research has contributed to growing scientific evidence that suggests abnormalities in neuronal calcium signaling play an important role in the development of Huntington's disease. UT Southwestern researchers demonstrated in the current study that the quinoline compounds – supplied by EnVivo – protected brain cells.

"If this holds, this compound can be considered to have potential therapeutic application for Huntington's," he said. "As we ultimately seek a cure, we are encouraged to have found something that may slow the progress or delay the onset of the disease."

Provided by UT Southwestern Medical Center (news : web)

Natural gases as a therapy for heart disease?

 An understanding of the interaction between hydrogen sulphide (the 'rotten eggs' gas) and nitric oxide, both naturally occurring in the body, could lead to the development of new therapies and interventions to treat heart failure.

Research carried out by scientists from the Peninsula Medical School at the University of Exeter and the National University of Singapore has analysed the complex 'cross talk' between hydrogen sulphide (H2S ) and nitric oxide (NO), both gasses that occur naturally in the body, and found that the interaction may offer potential strategies in the management of heart failure.

The research is published in the leading international journal Antioxidants and Redox Signaling.

Both gases interact naturally with each other within the body and the balance between the two and other chemical compounds has influence on health. The research team found that by modulating how H2S and NO interact, a positive affect was produced for heart health.

The two gases were found to interact together to form a thiol-sensitive compound (linked to the sulphur in H2S) which produces inotropic (muscular contraction) and lusitropic (muscular relaxation) effects in the heart. This crosstalk suggests that there is the potential to produce a molecule that may be of benefit to the heart and which could be the basis of a new drug therapy based on elements that occur naturally in the body.

The study also offers a new perspective on gaseous neurotransmitters, in which the function of cells is influenced by the interaction of the two gases.

Prof. Matt Whiteman, joint author from the Peninsula Medical School, commented: "Our findings are potentially very exciting and offer a novel insight into understanding how and why the heart fails. This could lead to new treatment and management strategies of heart failure, such as molecules which release H2S. By altering the ratio of H2S and NO, two naturally occurring physiological gases in the heart and perhaps the rest of the cardiovascular system, we have the potential to manipulate heart and vascular function. There is huge potential in the continued development of H2S delivery systems either through pharmacological means or through dietary intervention."

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by The Peninsula College of Medicine and Dentistry.

Journal Reference:

Qian-Chen Yong, Jia Ling Cheong, Fei Hua, Lih-Wen Deng, Yok Moi Khoo, How-Sung Lee, Alexis Perry, Mark Wood, Matthew Whiteman, Jin-Song Bian. Regulation of Heart Function by Endogenous Gaseous Mediators—Crosstalk Between Nitric Oxide and Hydrogen Sulfide. Antioxidants & Redox Signaling, 2011; 14 (11): 2081 DOI: 10.1089/ars.2010.3572

Astronomers reach for the stars to discover new cancer therapy

ScienceDaily (June 25, 2011) — Astronomers' research on celestial bodies may have an impact on the human body.

Ohio State University astronomers are working with medical physicists and radiation oncologists to develop a potential new radiation treatment -- one that is intended to be tougher on tumors, but gentler on healthy tissue.

In studying how chemical elements emit and absorb radiation inside stars and around black holes, the astronomers discovered that heavy metals such as iron emit low-energy electrons when exposed to X-rays at specific energies.

Their discovery raises the possibility that implants made from certain heavy elements could enable doctors to obliterate tumors with low-energy electrons, while exposing healthy tissue to much less radiation than is possible today. Similar implants could enhance medical diagnostic imaging.

On June 24, at the International Symposium on Molecular Spectroscopy, Ohio State University senior research scientist Sultana Nahar announces the team's computer simulations of the elements gold and platinum, and the design of a prototype device that generates X-rays at key frequencies.

Their simulations suggest that hitting a single gold or platinum atom with a small dose of X-rays at a narrow range of frequencies -- equal to roughly one tenth of the broad spectrum of X-ray radiation frequencies -- produces a flood of more than 20 low-energy electrons.

"As astronomers, we apply basic physics and chemistry to understand what's happening in stars. We're very excited to apply the same knowledge to potentially treat cancer," Nahar said.

"We believe that nanoparticles embedded in tumors can absorb X-rays efficiently at particular frequencies, resulting in electron ejections that can kill malignant cells," she continued. "From X-ray spectroscopy, we can predict those energies and which atoms or molecules are likely to be most effective."

Nahar and Anil Pradhan, professor of astronomy at Ohio State, discovered that particular frequencies of X-rays cause the electrons in heavy metal atoms to vibrate and break free from their orbits around the nucleus, creating what amounts to an electrically charged gas, or plasma, around the atoms at the nanometer scale.

They have thus dubbed their medical concept Resonant Nano-Plasma Theranostics (RNPT) -- the latter word a merger of "therapy" and "diagnostics."

"From a basic physics point of view, the use of radiation in medicine is highly indiscriminate," Pradhan added. "Really, there has been no fundamental advance in X-ray production since the 1890s, when Roentgen invented the X-ray tube, which produces X-rays over a very wide range."

No fundamental advance, that is, until now.

"Together with long-time collaborator and medical physicist Yan Yu from Thomas Jefferson University Medical College, we've developed the RNPT methodology, which we hope will have far-reaching consequences for X-ray imaging and radiation therapy," Pradhan said.

He explained why metals such as gold or platinum display this behavior, and how hospitals can take advantage of it. The basic physics, he said, has been well understood since the 1920s.

Physicists have long known that electrons orbit the nuclei of atoms at different distances, some close to the nucleus and some farther away. When one of the close-in electrons is lost, a far-out electron may drop in to take its place, which releases energy. This is called the Auger effect, which was discovered in 1922.

Often the energy is strong enough to kick out a second electron, called an Auger electron. The same process could also result in the emission of light particles, or photons, at specific energies or frequencies, the most prominent of which are called K-alpha X-rays.

The astronomers believe that K-alpha X-ray frequencies kick the close-in electrons out of heavy metal atoms such as platinum, causing many far-out electrons to fall in, and many more electrons to be kicked out. These free Auger electrons are low in energy but great in number, and could feasibly bombard nearby malignant cells and shatter their DNA.

While typical therapeutic X-ray machines such as CT scanners generate full-spectrum X-rays, hospitals could employ RNPT using only K-alpha X-rays, which would greatly reduce a patient's radiation exposure.

That's the function of the proof-of-principle device that the team has constructed. Though the working tabletop prototype needs to be further developed, these first experiments show that the Auger effect can be used to deliver specific frequencies of X-ray radiation to heavy metal nanoparticles embedded in diseased tissue for imaging or therapy.

Gold and Platinum are only the first two elements that the team is studying in detail for the application of the RNPT methodology. Both metals are safe to use in the body. Platinum is already used in the chemotherapy drug cisplatin, where it helps deliver the drug by binding to malignant DNA.

"This work could eventually lead to a combination of radiation therapy with chemotherapy using platinum as the active agent," Pradhan said.

Cancer therapy is new territory for the astronomers. Together with Yu, they came upon the idea for RNPT when they were trying to understand the abundance of different chemical elements inside stars.

Their goal at the time was to help astronomers understand what different stars are made of, based on how radiation flows through them and emanates from them.

Astronomers already have several methods for doing this, but their results vary widely. By simulating how different elements behave when exposed to the radiation inside stars, Nahar and Pradhan hope to help astronomers determine precisely what our sun is made of.

Even for a profession as mathematically rigorous as astronomy, Nahar and Pradhan's undertaking is staggeringly large. They must calculate how every possible atom contained in a star will react to every possible wavelength of energy. They rely on the Ohio Supercomputer Center for these calculations and simulations; in fact, their research team has ranked among the biggest users of computational resources ever since the center's establishment more than two decades ago.

The simulations have started to pay off, in an astrophysical sense. They have revealed that previous observations and calculations of chemical abundances of the sun may in fact be off by as much as 50 percent.

Even more surprising to the astronomers were the results for simulating the radiation absorption by heavy metal atoms, such as iron. Iron plays the dominant role in controlling radiation flow through stars, but it is also observed in some black hole environments, where K-alpha X-rays can be detected from Earth.

"That's when we realized that the implications went way beyond atomic astrophysics," Pradhan said. "X-rays are used all the time in radiation treatments and imaging, and so are heavy metals -- just not in this way. If we could target heavy metal nanoparticles to certain sites in the body, X-ray imaging and therapy could be more powerful, reduce radiation exposure, and be much more precise."

Leading a multi-disciplinary team, Nahar, Pradhan, and Yu are working with several colleagues in the departments of radiation oncology at Ohio State and Thomas Jefferson University Medical College to further explore these medical applications.

The Ohio State collaborators include Russell Pitzer, professor emeritus of chemistry, Enam Chowdhury, senior research associate in physics, and Sara Lim, a graduate student in biophysics. They also worked with Kaile Li and Jian Wang, assistant professors in radiation oncology; former postdoctoral researchers Max Montenegro (now of the Pontificia Universidad Católica de Chile), and Chiranjib Sur (now of the high-performance computing group of IBM's India Software Lab); and graduate student Mike Mrozik in chemical physics.

This research was funded by a Large Interdisciplinary Grant award from Ohio State, and computational resources were provided by the Ohio Supercomputer Center.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Ohio State University. The original article was written by Pam Frost Gorder.

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.