Navigation Links
Penn team uses self-assembly to make molecule-sized particles with patches of charge
Date:10/20/2009

PHILADELPHIA - Physicists, chemists and engineers at the University of Pennsylvania have demonstrated a novel method for the controlled formation of patchy particles, using charged, self-assembling molecules that may one day serve as drug-delivery vehicles to combat disease and perhaps be used in small batteries that store and release charge.

Researchers demonstrated that the positive electrical charges of calcium ions just like the calcium in teeth and bone can form bridges between negatively charged polymers that would normally repel each other. The polymers, similar to the lipids that make the membranes surrounding living cells, have both a water-loving part linked to a water-repelling part. On the surfaces of these cell-sized polymer sacks, the calcium ions create calcium-rich islands or patches on top of negatively-charged polymer. Copper ions also work, and the patches can be made to coalesce and cover half of the particle. This polarized structure is the basic arrangement needed to set up, for example, the two electrodes of a microscopic battery. They could also one day be functionalized into docking sites to enhance targeted delivery of drug-laden particles to cells.

While the concept seems simple, that opposite charges attract, the creation and control of patches on one small particle has been a challenge. Scientists like Dennis E. Discher, principal investigator of the study and a professor of chemical and biomolecular engineering at Penn, are designing materials at the nanoscale because future technologies will increasingly rely on structures with distinct and controlled surfaces. Physicians, for example, will improve medical therapies by wrapping drugs within the bioengineered polymer sacks, or by creating tiny biomedical sensors. Green energy production and storage will also require structures with scales no longer measured by inches, but by micrometers and nanometers.

The collaboration involved faculty from Penn's School of Engineering and Applied Science, the School of Medicine and the School of Arts and Sciences, and demonstrated, more specifically, the selective binding of multivalent cationic ligands within a mixture of both polyanionic and non-ionic amphiphiles that all co-assemble into either patchy sacks called vesicles or molecular cylinders called worm-like micelles. Similar principles have been explored with lipids in the field of membrane biophysics because calcium is key to many cellular signaling processes. The trick is that the energy of attraction of opposite charges must be adjusted to find a balance with the large entropic price for localization into spots. If the attractions are too large, the ions precipitate, just like adding too much sugar to tea or coffee.

Using a little bit of acid or a little of base, the patchy polymer vesicles and cylinders can be made with tunable sizes, shapes and spacings. Assemblies with single large patches are called Janus assemblies, named after the double-faced Roman god, and the assemblies generally last for years because these are polymer-based structures.

"The key advance we present in this study is the restricted range of conditions that are required for self assembly in these solutions," Discher said. "We show that, in addition to polymers, negatively-charged cell lipids which are involved in all sorts of cell-signaling processes like cell motion and cancer mechanics, can also make domains or islands with calcium."

The work is representative of national research into soft matter, materials constructed from organic molecules like lipids, peptides and nucleic acids. A properly designed molecular system can produce a wide array of nanostructures and microstructures, emulating and extending what is found in nature.


'/>"/>

Contact: Jordan Reese
jreese@upenn.edu
215-573-6604
University of Pennsylvania
Source:Eurekalert

Related biology news :

1. Clemson bioengineer uses nanoparticles to target drugs
2. Do dust particles curb climate change?
3. Therapeutic nanoparticles give new meaning to sugar-coating medicine
4. Carbon nanoparticles toxic to adult fruit flies but benign to young
5. New insights into health and environmental effects of carbon nanoparticles
6. Facile synthesis of nanoparticles with multiple functions advanced in Singapore
7. University of Leicester researchers discover new fluorescent silicon nanoparticles
8. New nanoparticles could revolutionize therapeutic drug discovery
9. Shape matters in the case of cobalt nanoparticles
10. UCSD researchers make first direct observations of biological particles in high-altitude ice clouds
11. To fight drug addiction, UB researchers target the brain with nanoparticles
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:3/31/2016)... March 31, 2016   ... or the "Company") LegacyXChange is excited to ... its soon to be launched online site for trading ... ) will also provide potential shareholders a sense ... technology to an industry that is notorious for fraud. ...
(Date:3/29/2016)... BOCA RATON, Florida , March 29, 2016 /PRNewswire/ ... ("LegacyXChange" or the "Company") LegacyXChange "LEGX" and SelectaDNA/CSI Protect ... Synthetic DNA in ink used in a variety of ... preventing theft. Buyers of originally created collectibles from athletes ... authenticity through forensic analysis of the DNA. ...
(Date:3/22/2016)... India , March 22, 2016 /PRNewswire/ ... market research report "Electronic Sensors Market for Consumer ... Proximity, & Others), Application (Communication & IT, ... Geography - Global Forecast to 2022", published ... industry is expected to reach USD 26.76 ...
Breaking Biology News(10 mins):
(Date:6/23/2016)... ... June 23, 2016 , ... Supplyframe, the Industry ... Supplyframe Design Lab . Located in Pasadena, Calif., the Design Lab’s mission ... hardware projects are designed, built and brought to market. , The Design Lab ...
(Date:6/23/2016)... 2016  Blueprint Bio, a company dedicated to identifying, ... community, has closed its Series A funding round, according ... "We have received a commitment from Forentis Fund ... to meet our current goals," stated Matthew Nunez ... to complete validation on the current projects in our ...
(Date:6/23/2016)... ... June 23, 2016 , ... Regulatory Compliance Associates® ... provides a free webinar on Performing Quality Investigations: Getting to Root ... CT at no charge. , Incomplete investigations are still a major concern to ...
(Date:6/22/2016)... 22, 2016 Cell Applications, Inc. and ... to produce up to one billion human induced ... one week. These high-quality, consistent stem cells enable ... and spend more time doing meaningful, relevant research. ... high-volume manufacturing process that produces affordable, reliable HiPSC ...
Breaking Biology Technology: