Any change in nanoparticle solubility with local acidity (pH**) ultimately affects how they are distributed in the environment as well as their potential for uptake into organisms. This is crucial when designing nanoparticles for use in medicine, explains NIST chemical engineer Vivek Prabhu. "Cells in the body are very compartmentalized.
There are places within the cell that have vastly different pH. For instance, in the sea of the cell, the cytosol, pH is regulated to be about 7.2, which is slightly basic. But within the lysosome, which is where things go to get broken down, the pH is about 4.5, so it's very acidic."
Nanoparticles designed for use in drug therapy or as contrast agents for medical imaging typically are coated with molecules to prevent the particles from clumping together, which would reduce their effectiveness. But the efficacy of the anti-clumping coating often depends on the pH of the environment. According to the NIST team, while it's relatively easy to put nanoparticles in a solution at a particular pH and to study the stability of the suspension over long times, it is difficult to tell what happens when the particles are suddenly exposed to a different level of acidity as often occurs in environmental and application contexts. How long does it take them to react to this change and how?
"Our idea borrows some of the materials used in photolithography to make microcircuits," says Prabhu. "There are molecules that become acids when you shine a light on them—photo acid generators. So instead of manually pouring acid into a solution and stirring it around, you start with a solution in which these molecules already are mixed and dissolved. Once you shine light on it …bam! Photolysis occurs and it becomes acidic." The acidity of the solution can be made to jump a major step—an amount chosen by the experimenter—without needing to wait for mixing or disturbing the solution. "It gives you a way to probe the nanoparticle solution dynamics at much shorter timescales than before," says Prabhu.
Using their "instant acid" technique and light scattering instruments to monitor the aggregation of nanoparticles, the NIST team followed the growth of clusters of chemically stabilized latex nanoparticles for the first few seconds after inducing the pH transition with light. Their results demonstrate that under certain conditions, the stability of the nanoparticles—their tendency to resist clumping—becomes very sensitive to pH. Studies such as these could provide a stronger foundation to design nanoparticles for applications such as targeting tumor cells that have levels of acidity markedly different from normal cells.
The work was supported in part by the National Research Council–NIST Postdoctoral Fellowship Program.
* R.J. Murphy, D. Pristinski, K. Migler, J.F. Douglas and V.M. Prabhu. Dynamic light scattering investigations of nanoparticle aggregation following a light-induced pH jump. Journal of Chemical Physics. 132, 194903 (2010) doi:10.1063/1.3425883.
** pH is the common measure used by chemists of how acidic or basic a solution is. The scale runs from 0 to 14; lower values are more acidic, higher values more basic; 7 is considered neutral.
Michael Baum | EurekAlert!
Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz
Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences