Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Let's do the twist: Spiral proteins are efficient gene delivery agents

16.12.2011
Clinical gene therapy may be one step closer, thanks to a new twist on an old class of molecules.

A group of University of Illinois researchers, led by professors Jianjun Cheng and Fei Wang, have demonstrated that short spiral-shaped proteins can efficiently deliver DNA segments to cells. The team published its work in the journal Angewandte Chemie.

“The main idea is these are new materials that could potentially be used for clinical gene therapy,” said Cheng, a professor of materials science and engineering, of chemistry and of bioengineering.

Researchers have been exploring two main pathways for gene delivery: modified viruses and nonviral agents such as synthetic polymers or lipids. The challenge has been to address both toxicity and efficiency. Polypeptides, or short protein chains, are attractive materials because they are biocompatible, fine-tunable and small.

“There are very good in vitro transfection agents available, but we cannot use them in vivo because of their toxicity or because some of the complexes are too large,” Cheng said. “Using our polypeptides, we can control the size down to the 200 nanometer range, which makes it a very interesting delivery system for in vivo applications.”

A polypeptide called poly-L-lysine (PLL) was an early contender in gene delivery studies. PLL has positively charged side chains – molecular structures that stem from each amino acid link in the polypeptide chain – so it is soluble in the watery cellular environment.

However, PLL gradually fell into disuse because of its limited ability to deliver genes to the inside of cells, a process called transfection, and its high toxicity. Cheng postulated that PLL’s low efficiency could be a function of its globular shape, as polypeptides with charged side chains tend to adopt a random coil structure, instead of a more orderly spiral helix.

“We never studied the connections of conformation with transfection efficiency, because we were never able to synthetically make materials containing both cationic charge and a high percentage of helical structures,” Cheng said. “This paper demonstrated for the first time that helicity has a huge impact on transfection efficiencies.”

Earlier this year, Cheng’s group developed a method of making helical polypeptides with positively charged side chains. To test whether a helical polypeptide could be an efficient gene delivery agent, the group assembled a library of 31 helical polypeptides that are stable over a broad pH range and can bond to DNA for delivery. Most of them outperformed PLL and a few outstripped a leading commercial agent called polyethyleneimine (PEI), notorious for its toxicity although it is highly efficient. The helical molecules even worked on some of the hardest cells to transfect: stem cells and fibroblast cells.

“People kind of gave up on polypeptide-based materials for gene deliveries because PLL had low efficiency and high toxicity,” Cheng said. “The polypeptide that we designed, synthesized and used in this study has very high efficiency and also well-controlled toxicities. With a modified helical polypeptide, we demonstrated that we can outperform many commercial agents.”

The polypeptides Cheng and his co-workers developed can adopt helical shapes because the side chains are longer, so that the positive charges do not interfere with the protein’s winding. The positive charges readily bind to negatively charged DNA, forming complexes that are internalized into cellular compartments called endosomes. The helical structures rupture the endosomal membranes, letting the DNA escape into the cell.

To confirm that the spiral polypeptide shape is the key to transfection, the researchers then synthesized two batches of the most efficient polypeptide: one batch with a helical shape, one with the usual random coil. The helical polypeptide far exceeded the random-coil polypeptide in both efficiency and stability.

“This demonstrates that the helicity is very important, because the polymer has exactly the same chemical makeup; the only difference is the structure,” said Cheng, who also is associated with the Institute for Genomic Biology and the Beckman Institute for Advanced Science and Technology, both at the U. of I.
Next, the researchers plan to further explore their helical polypeptides’ properties, especially their cell-penetrating abilities. They hope to control sequence and structure with precision for specific applications, including gene delivery, drug delivery, cell-membrane penetration and antimicrobial action.

The National Science Foundation and the National Institutes of Health supported this work. Fei Wang is a professor of cell and development biology and of bioengineering. Postdoctoral researchers Nathan Gabrielson, Lichen Yin and Dong Li and graduate student Hua Lu were co-authors of the paper.

Liz Ahlberg | University of Illinois
Further information:
http://www.illinois.edu

More articles from Life Sciences:

nachricht Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY

nachricht NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>