Tag Archives: biomolecules

A DNA origami-based nanoscopic force clamp

Nanoclamp made of DNA strands. Illustration: Christoph Hohmann

Nanoclamp made of DNA strands. Illustration: Christoph Hohmann

An Oct. 21, 2016 news item on ScienceDaily announces a new nanotool,

Physicists at Ludwig-Maximilians-Universitat (LMU) in Munich have developed a novel nanotool that provides a facile means of characterizing the mechanical properties of biomolecules.

An Oct. 21, 2016 Ludwig-Maximilians-Universitat (LMU) press release (also on EurekAlert), which originated the news item, explains the work in more detail (Note: A link has been removed),

Faced with the thousands of proteins and genes found in virtually every cell in the body, biologists want to know how they all work exactly: How do they interact to carry out their specific functions and how do they respond and adapt to perturbations? One of the crucial factors in all of these processes is the question of how biomolecules react to the minuscule forces that operate at the molecular level. LMU physicists led by Professor Tim Liedl, in collaboration with researchers at the Technical University in Braunschweig and at Regensburg University, have come up with a method that allows them to exert a constant force on a single macromolecule with dimensions of a few nanometers, and to observe the molecule’s response. The researchers can this way test whether or not a protein or a gene is capable of functioning normally when its structure is deformed by forces of the magnitude expected in the interior of cells. This new method of force spectroscopy uses self-assembled nanoscopic power gauges, requires no macroscopic tools and can analyze large numbers of molecules in parallel, which speeds up the process of data acquisition enormously.

With their new approach, the researchers have overcome two fundamental limitations of the most commonly used force spectroscopy instruments. In the case of force microscopy and methodologies based on optical or magnetic tweezers, the molecules under investigation are always directly connected to a macroscopic transducer. They require precise control of the position of an object – a sphere or a sharp metal tip on the order of a micrometer in size – that exerts a force on molecules that are anchored to that object. This strategy is technically extremely demanding and the data obtained is often noisy. Furthermore, these procedures can only be used to probe molecules one at a time. The new method dispenses with all these restrictions. “The structures we use operate completely autonomously“, explains Philipp Nickels, a member of Tim Liedl’s research group. “And we can use them to study countless numbers of molecules simultaneously.”

A feather-light touch

The members of the Munich group, which is affiliated with the Cluster of Excellence NIM (Nanosystems Initiative Munich), are acknowledged masters of “DNA origami”. This methodology exploits the base-pairing properties of DNA for the construction of nanostructures from strands that fold up and pair locally in a manner determined by their nucleotide sequences. In the present case, the DNA sequences are programmed to interact with each other in such a way that the final structure is a molecular clamp that can be programmed to exert a defined force on a test molecule. To this end, a single-stranded DNA that contains a specific sequence capable of recruiting the molecule of interest spans from one arm of the clamp to the other. The applied force can then be tuned by changing the length of the single strand base by base. “That is equivalent to stretching a spring ever so-o-o slightly,” says Nickels. Indeed, by this means it is possible to apply extremely tiny forces between 1 and 15 pN (1 pN = one billionth of a Newton) – comparable in magnitude to those that act on proteins and genes in cells. “In principle, we can capture any type of biomolecule with these clamps and investigate its physical properties,” says Tim Liedl.

The effect of the applied force is read out by taking advantage of the phenomenon of Förster Resonant Energy Transfer (FRET). “FRET involves the transfer of energy between two fluorescent dyes and is strongly dependent on the distance between them.” explains Professor Philip Tinnefeld from TU Braunschweig. When the force applied to the test molecule is sufficient to deform it, the distance between the fluorescent markers changes and the magnitude of energy transfer serves as an exquisitely precise measure of the distortion of the test molecule on the nanometer scale.

Together with Dina Grohmann from Universität Regensburg, the team has used the new technique to investigate the properties of the so-called TATA Binding Protein, an important gene regulator which binds to a specific upstream nucleotide sequence in genes and helps to trigger their expression. They found that the TATA protein can no longer perform its normal function if its target sequence is subjected to a force of more than 6 pN. – The new technology has just made its debut. But since the clamps are minuscule and operate autonomously, it may well be possible in the future to use them to study molecular processes in living cells in real time.

Sometimes reading these news releases, my mind is boggled. What an extraordinary time to live.

Here’s a link to and a citation for the paper,

Molecular force spectroscopy with a DNA origami–based nanoscopic force clamp by Philipp C. Nickels, Bettina Wünsch, Phil Holzmeister, Wooli Bae, Luisa M. Kneer, Dina Grohmann, Philip Tinnefeld, Tim Lied. Science  21 Oct 2016: Vol. 354, Issue 6310, pp. 305-307 DOI: 10.1126/science.aah5974

This paper is behind a paywall.

Medical nanobots (nanorobots) and biocomputing; an important step in Russia

Russian researchers have reported a technique which can make logical calculations from within cells according to an Aug. 19, 2014 news item on ScienceDaily,

Researchers from the Institute of General Physics of the Russian Academy of Sciences, the Institute of Bioorganic Chemistry of the Russian Academy of Sciences and MIPT [Moscow Institute of Physics and Technology] have made an important step towards creating medical nanorobots. They discovered a way of enabling nano- and microparticles to produce logical calculations using a variety of biochemical reactions.

An Aug. 19 (?), 2014 MIPT press release, which originated the news item, provides a good beginner’s explanation of bioengineering in the context of this research,

For example, modern bioengineering techniques allow for making a cell illuminate with different colors or even programming it to die, linking the initiation  of apoptosis [cell death] to the result of binary operations.

Many scientists believe logical operations inside cells or in artificial biomolecular systems to be a way of controlling biological processes and creating full-fledged micro-and nano-robots, which can, for example, deliver drugs on schedule to those tissues where they are needed.

Calculations using biomolecules inside cells, a.k.a. biocomputing, are a very promising and rapidly developing branch of science, according to the leading author of the study, Maxim Nikitin, a 2010 graduate of MIPT’s Department of Biological and Medical Physics. Biocomputing uses natural cellular mechanisms. It is far more difficult, however, to do calculations outside cells, where there are no natural structures that could help carry out calculations. The new study focuses specifically on extracellular biocomputing.

The study paves the way for a number of biomedical technologies and differs significantly from previous works in biocomputing, which focus on both the outside and inside of cells. Scientists from across the globe have been researching binary operations in DNA, RNA and proteins for over a decade now, but Maxim Nikitin and his colleagues were the first to propose and experimentally confirm a method to transform almost any type of nanoparticle or microparticle into autonomous biocomputing structures that are capable of implementing a functionally complete set of Boolean logic gates (YES, NOT, AND and OR) and binding to a target (such as a cell) as result of a computation. This method allows for selective binding to target cells, as well as it represents a new platform to analyze blood and other biological materials.

The prefix “nano” in this case is not a fad or a mere formality. A decrease in particle size sometimes leads to drastic changes in the physical and chemical properties of a substance. The smaller the size, the greater the reactivity; very small semiconductor particles, for example, may produce fluorescent light. The new research project used nanoparticles (i.e. particles of 100 nm) and microparticles (3000 nm or 3 micrometers).

Nanoparticles were coated with a special layer, which “disintegrated” in different ways when exposed to different combinations of signals. A signal here is the interaction of nanoparticles with a particular substance. For example, to implement the logical operation “AND” a spherical nanoparticle was coated with a layer of molecules, which held a layer of spheres of a smaller diameter around it. The molecules holding the outer shell were of two types, each type reacting only to a particular signal; when in contact with two different substances small spheres separated from the surface of a nanoparticle of a larger diameter. Removing the outer layer exposed the active parts of the inner particle, and it was then able to interact with its target. Thus, the team obtained one signal in response to two signals.

For bonding nanoparticles, the researchers selected antibodies. This also distinguishes their project from a number of previous studies in biocomputing, which used DNA or RNA for logical operations. These natural proteins of the immune system have a small active region, which responds only to certain molecules; the body uses the high selectivity of antibodies to recognize and neutralize bacteria and other pathogens.

Making sure that the combination of different types of nanoparticles and antibodies makes it possible to implement various kinds of logical operations, the researchers showed that cancer cells can be specifically targeted as well. The team obtained not simply nanoparticles that can bind to certain types of cells, but particles that look for target cells when both of two different conditions are met, or when two different molecules are present or absent. This additional control may come in handy for more accurate destruction of cancer cells with minimal impact on healthy tissues and organs.

Maxim Nikitin said that although this is just as mall step towards creating efficient nanobiorobots, this area of science is very interesting and opens up great vistas for further research, if one draws an analogy between the first works in the creation of nanobiocomputers and the creation of the first diodes and transistors, which resulted in the rapid development of electronic computers.

Here’s a link to and a citation for the paper,

Biocomputing based on particle disassembly by Maxim P. Nikitin, Victoria O. Shipunova, Sergey M. Deyev, & Petr I. Nikitin. Nature Nanotechnology (2014) doi:10.1038/nnano.2014.156 Published online 17 August 2014

This paper is behind a paywall.

Extracting biomolecules from live cells with carbon nanotubes

Being able to extract biomolecules from living cells means nondestruction of the rest of the cell and the ability to observe the consequences of the extraction. From a July 18, 2014 news item on Azonano,

University of Houston researchers have devised a new method for extracting molecules from live cells without disrupting cell development, work that could provide new avenues for the diagnosis of cancer and other diseases.

The researchers used magnetized carbon nanotubes to extract biomolecules from live cells, allowing them to retrieve molecular information without killing the individual cells. A description of the work appears this week in the Proceedings of the National Academy of Sciences.

A July 16, 2014 University of Houston news release by Jeannie Kever, which originated the news item, provides more detail,

Most current methods of identifying intracellular information result in the death of the individual cells, making it impossible to continue to gain information and assess change over time, said Zhifeng Ren, M.D. Anderson Chair professor of physics and principal investigator at the Center for Superconductivity at UH and lead author of the paper. The work was a collaboration between Ren’s lab and that of Paul Chu, T.L.L. Temple Chair of Science and founding director of the Texas Center for Superconductivity.

Chu, a co-author of the paper, said the new technique will allow researchers to draw fundamental information from a single cell.The researchers said the steps outlined in the paper offer proof of concept. Ren said the next step “will be more study of the biological and chemical processes of the cell, more analysis.”

The initial results hold promise for biomedicine, he said.  “This shows how nanoscience and nanoengineering can help the medical field.”

Cai said the new method will be helpful for cancer drug screening and carcinogenesis study, as well as for studies that allow researchers to obtain information from single cells, replacing previous sampling methods that average out cellular diversity and obscure the specificity of the biomarker profiles.

In the paper, the researchers explain their rationale for the work – most methods for extracting molecular information result in cell death, and those that do spare the cell carry special challenges, including limited efficiency.

This method is relatively straightforward, requiring the use of magnetized carbon nanotubes as the transporter and a polycarbonate filter as a collector, they report. Cells from a human embryonic kidney cancer cell line were used for the experiment.

The work builds on a 2005 paper published by Ren’s group in Nature Methods, which established that magnetized carbon nanotubes can deliver molecular payloads into cells. The current research takes that one step further to move molecules out of cells by magnetically driving them through the cell walls.

The carbon nanotubes were grown with a plasma-enhanced chemical vapor deposition system, with magnetic nickel particles enclosed at the tips. A layer of nickel was also deposited along the surface of individual nanotubes in order to make the nanotubes capable of penetrating a cell wall guided by a magnet.

Here’s a link to and a citation for the paper,

Molecular extraction in single live cells by sneaking in and out magnetic nanomaterials by Zhen Yang, Liangzi Deng, Yucheng Lan, Xiaoliu Zhang, Zhonghong Gao, Ching-Wu Chu, Dong Cai, and Zhifeng Ren. PNAS 2014 ; published ahead of print July 16, 2014, doi:10.1073/pnas.1411802111

This paper is behind a paywall.

Similarities between biological molecules and synthetic nanocrystals extend beyond size

Researchers at the University of Illinois at Urbana-Champaign have determined that there are more similarities between biological molecules and synthetic nanocrystals than formerly believed, according to a Dec. 17, 2013 news item on Nanowerk (Note: A link has been removed),

Researchers have long thought that biological molecules and synthetic nanocrystals were similar only in size. Now, University of Illinois at Urbana-Champaign chemists have found that they can add reactivity to the list of shared traits. Atoms in a nanocrystal can cooperate with each other to facilitate binding or switching, a phenomenon widely found in biological molecules.

The finding could catalyze manufacturing of nanocrystals for smart sensors, solar cells, tiny transistors for optical computers, and medical imaging. Led by chemistry professor Prashant Jain, the team published its findings in the journal Nature Communications (“Co-operativity in a nanocrystalline solid-state transition”).

A Dec. 16, 2013 University of Illinois at Urbana-Champaign news release, which originated the news item, explains why the scientists are so interested and how they went about their investigation,

“In geological, industrial and domestic environments, the nanoscale grains of any material undergo chemical transitions when they are put under reactive conditions,” Jain said. “Iron rusting over time and diamond forming from carbon are examples of two commonly occurring transitions. Understanding how these transitions occur on the scale of the tiniest grains of the material is a major motivation of our work.”

Scientists can exploit such transitions to make nanocrystals that conform to a particular structure. They can make a nanocrystal of one material and transform it into another material, essentially using the original nanocrystal framework as a template for creating a nanocrystal of the new material with the same size and shape. This lets researchers create nanocrystals of new materials in shapes and structures they may not be able to otherwise.

In the new study, the researchers transformed tiny crystals of the material cadmium selenide to crystals of copper selenide. Copper selenide nanocrystals have a number of interesting properties that can be used for solar energy harvesting, optical computing and laser surgery. Transformation from cadmium selenide creates nanocrystals with a purity difficult to attain from other methods.

The researchers, including graduate student Sarah White, used advanced microscopy and spectroscopy techniques to determine the dynamics of the atoms within the crystals during the transformation and found that the transformation occurs not as a slow diffusion process, but as a rapid switching thanks to co-operativity.

The researchers saw that once the cadmium-selenide nanocrystal has taken up a few initial copper “seed” impurities, atoms in the rest of the lattice can cooperate to rapidly swap out the rest of the cadmium for copper. Jain compares the crystals to hemoglobin, the molecule in red blood cells that carries oxygen. Once one oxygen molecule has bound to hemoglobin, other binding sites within hemoglobin slightly change conformation to more easily pick up more oxygen. He posits that similarly, copper impurities might cause a structural change in the nanocrystal, making it easier for more copper ions to infiltrate the nanocrystal in a rapid cascade.

The researchers reproduced the experiment with silver, in addition to copper, and saw similar, though slightly less speedy, cooperative behavior.

Now, Jain’s team is using its advanced imaging to watch transitions happen in single nanocrystals, in real time.

“We have a sophisticated optical microscope in our lab, which has now allowed us to catch a single nanocrystal in the act of making a transition,” Jain said. “This is allowing us to learn hidden details about how the transition actually proceeds. We are also learning how one nanocrystal behaves differently from another.”

Next, the researchers plan to explore biomolecule-like cooperative phenomena in other solid-state materials and processes. For example, co-operativity in catalytic processes could have major implications for solar energy or manufacturing of expensive specialty chemicals.

“In the long term, we are interested in exploiting the co-operative behavior to design artificial smart materials that respond in a switch-like manner like hemoglobin in our body does,” Jain said.

Here’s an image of the various forms of cadmium selenide used in research,

Nanocrystals of cadmium selenide, known for their brilliant luminescence, display intriguing chemical behavior resulting from positive cooperation between atoms, a behavior akin to that found in biomolecules.  Photo courtesy Prashant Jain

Nanocrystals of cadmium selenide, known for their brilliant luminescence, display intriguing chemical behavior resulting from positive cooperation between atoms, a behavior akin to that found in biomolecules. Photo courtesy
Prashant Jain

For the curious, here’s a link to and a citation for the paper,

Co-operativity in a nanocrystalline solid-state transition by Sarah L. White, Jeremy G. Smith, Mayank Behl, & Prashant K. Jain Nature Communications 4, Article number: 2933 doi:10.1038/ncomms3933 Published 12 December 2013

This article is behind a paywall.

Watching zinc, iron, and copper molecules real-time as they interact with biomolecules

Eventually they’re hoping this work will lead to insights about diabetes and cancer. In the meantime, researchers at RIKEN Center for Life Science Technologies (Japan) have developed a new imaging technique that allows them to observe metal molecules interacting with biomolecules in real-time. From the May 2, 2013 news release on EurekAlert,

Metal elements and molecules interact in the body but visualizing them together has always been a challenge. Researchers from the RIKEN Center for Life Science Technologies in Japan have developed a new molecular imaging technology that enables them to visualize bio-metals and bio-molecules simultaneously in a live mouse. This new technology will enable researchers to study the complex interactions between metal elements and molecules in living organisms.

It’s well known we need zinc, iron, and copper in our bodies for proper functioning. Until now, no one has been able to observe the interaction in real-time, from the RIKEN May 2, 2013 press release (which originated the EurekAlert news release),

In the study, the researchers were able to visualise two radioactive agents injected in a tumor-bearing mouse, as well as an anti-tumor antibody labelled with a PET molecular probe agent, simultaneously in the live mouse.

This new revolutionary technology is expected to offer new insights into the relationships between bio-metal elements and associated bio-molecules, and the roles they play in diseases such as diabetes and cancer.

The researchers had to create a camera capable of visualizing the interactions (from the RIKEN press release),

Dr. Shuichi Enomoto, Dr. Shinji Motomura and colleagues, from the RIKEN Center for Life Science Technologies have developed a gamma-ray imaging camera enabling them to detect the gamma-rays emitted by multiple bio-metal elements in the body and study their behavior.

Their second prototype of the system, called GREI–II and presented today in the Journal of Analytical Atomic Spectrometry, enables them to visualize multiple bio-metal elements more than 10 times faster than before, and to do so simultaneously with positron emission tomography (PET).

You can find the research study here.

For those unfamiliar with RIKEN, here’s more from their About RIKEN page,

RIKEN is Japan’s largest comprehensive research institution renowned for high-quality research in a diverse range of scientific disciplines. Founded in 1917 as a private research foundation in Tokyo, RIKEN has grown rapidly in size and scope, today encompassing a network of world-class research centers and institutes across Japan.

Making movies of biomolecules

’tis the season for recycling news; this research about making biomolecular movies was published in Nature Protocols in June 2012 according to the Jan. 4, 2013 news item on phys.org (Note: Links have been removed),

Toshio Ando and co-workers at Kanazawa University [Japan] have developed and used HS-AFM [high-speed atomic force microscopy] to increase our understanding of several protein systems through microscopic movies of unprecedented spatial and temporal resolution. The team have now published a guide to video recording these important cell components, so that other researchers can benefit from this unique technology.

To produce an image, HS-AFM acquires information on sample height at many points by tapping the sample with the sharp tip of a tiny cantilever. Depending on the application, this might involve recording the amplitude and phase of oscillations, or the resonant frequency of the cantilever.

Ando and co-workers use very small cantilevers that afford 10 to 20 times the sensitivity of larger, conventional cantilevers. Copies of their home-made apparatus are now commercially available through the manufacturer Research Institute of Biomolecule Metrology Co., Ltd. (RIBM) in Tsukuba, and record images at least ten times more quickly than their competitors.

There are more details in the news item or for those who want to read the guide, here’s a citation and a link,

Guide to video recording of structure dynamics and dynamic processes of proteins by high-speed atomic force microscopy by Takayuki Uchihashi, Noriyuki Kodera, & Toshio Ando in Nature Protocols 7 (6), 1193–1206 (2012) doi:10.1038/nprot.2012.047

This article is behind a paywall.

Lastly, should anyone wish to purchase the apparatus developed at Kanazawa University from the Research Institute of Biomolecule Metrology Co., Ltd., here’s more about it from the company’s home page,

Dynamic Visualization of nano-scale world

HS-AFM*1.0 – Ando model – is the High-Speed Atomic Force Microscope which was developed based on the research achievements accomplished by Prof. Ando in Kanazawa University. This is the world’s first instrument that broke through the weak point of conventional AFM “low-speed”, and realized the video rate scan. The high-speed scan enables us to capture swinging molecules in solution clearly without blurring. Consequently, the strong anchoring of a sample to the substrate is unnecessary and a dynamic observation is achieved without losing the activities of soft biomolecules.

Protein cages, viruses, and nanoparticles

The Dec. 19, 2012 news release on EurekAlert about a study published by researchers at Aalto University (Finland) describes a project where virus particles are combined with nanoparticles to create new metamaterials,

Scientists from Aalto University, Finland, have succeeded in organising virus particles, protein cages and nanoparticles into crystalline materials. These nanomaterials studied by the Finnish research group are important for applications in sensing, optics, electronics and drug delivery.

… biohybrid superlattices of nanoparticles and proteins would allow the best features of both particle types to be combined. They would comprise the versatility of synthetic nanoparticles and the highly controlled assembly properties of biomolecules.

The gold nanoparticles and viruses adopt a special kind of crystal structure. It does not correspond to any known atomic or molecular crystal structure and it has previously not been observed with nano-sized particles.

Virus particles – the old foes of mankind – can do much more than infect living organisms. Evolution has rendered them with the capability of highly controlled self-assembly properties. Ultimately, by utilising their building blocks we can bring multiple functions to hybrid materials that consist of both living and synthetic matter, Kostiainen [Mauri A. Kostiainen, postdoctoral researcher] trusts.

The article which has been published in Nature Nanotechnology is free,

Electrostatic assembly of binary nanoparticle superlattices using protein cages by Mauri A. Kostiainen, Panu Hiekkataipale, Ari Laiho, Vincent Lemieux, Jani Seitsonen, Janne Ruokolainen & Pierpaolo Ceci in Nature Nanotechnology (2012) doi:10.1038/nnano.2012.220  Published online 16 December 2012

There’s a video demonstrating the assembly,

From the YouTube page, here’s a description of what the video is demonstrating,

Aalto University-led research group shows that CCMV virus or ferritin protein cages can be used to guide the assembly of RNA molecules or iron oxide nanoparticles into three-dimensional binary superlattices. The lattices are formed through tuneable electrostatic interactions with charged gold nanoparticles.

Bravo and thank  you to  Kostiainen who seems to have written the news release and prepared all of the additional materials (image and video). There are university press offices that could take lessons from Kostiainen’s efforts to communicate about the work.

Environment influences nanomaterial reactions to biological cells

The discussion I’ve seen around nanomaterials and toxicological effects has largely centered on shapes, size, aggregate/agglomerate, etc. By contrast, Carl Walkey’s July 24, 2012 Nanowerk Spotlight essay focuses on nanomaterial surfaces, bare or coated with serum proteins (Note: I have removed links),

Biomolecule adsorption to nanomaterials is usually studied from physiological fluids with suspended biomolecules. Examples include blood serum/plasma, pulmonary surfactant, and synovial fluid. However, until now the amount of those molecules has not been considered relevant to the study. In a recent article appearing in ACS Nano (“Effects of the Presence or Absence of a Protein Corona on Silica Nanoparticle Uptake and Impact on Cells”), Drs. Anna Salvati, Kenneth Dawson, and their colleagues at the University College in Dublin, Ireland, show that if nanoparticles are exposed directly to cells in the absence of suspended biomolecules, the nanoparticles will extract biomolecules directly from cells themselves.

In their experiments, the team exposed silica nanoparticles to cells in two sets. One set was introduced into cell culture media that was supplemented with the usual concentration of fetal bovine serum, and the other into media that had no serum additives. They then incubated both sets of particles with a lung cancer cell line and measured particle uptake kinetics and cell adhesion. Nanoparticles treated under both conditions associated with cells. However, the particles that were incubated in media alone associated to a much greater extent than those that were first incubated in serum. This indicates that the affinity of the bare nanoparticle surface to the cell is much higher than the affinity of an equivalent surface that is coated with serum proteins. [emphasis mine] Similar observations are reported before for other systems, where it was also found that uptake under serum-free conditions is higher.

Moe specifically,

“When the nanomaterial is put in contact with a physiological environment, it is given a menu of possible biomolecules to adsorb” explains Dawson. “It will essentially go shopping for the biomolecules that it wants. Over time, it will exchange with the environment until it finds the things that it really likes most. If you don’t give it enough biomolecules in the form of serum, it will extract components from the cells themselves.”

The same silica nanoparticles exposed to cells in the two different conditions had different cellular responses as well. Most of the serum-coated particles were taken up within vesicles in the cell cytoplasm and produced no overt signs of toxicity. In contrast, the particles without a serum coating adhered to the cell surface to a greater extent, were present in vesicles, and some were also found free-floating in the cytoplasm. Exposure to particles in absence of serum significantly decreased cell viability and caused cells to take on a rounded morphology that is indicative of cell death. Dawson believes that cell death from uncoated particles is the result of strong interactions between the particle surface and the cell surface, which may damage the cell membrane, and/or initiate aberrant signaling cascades. When serum proteins are adsorbed to the nanoparticles, they ‘passivate’ the surface and limit direct nanomaterial-cell interactions.

When considering the early interactions of a nanomaterial with a cell, Dawson points out that one cannot think of the nanomaterial alone. Instead, one must think of the nanoparticle and its adsorbed biomolecules as a fundamental unit. [emphasis mine]

Most importantly,

Dawson believes that researchers must pay closer attention to the composition of the biomolecular environment surrounding the particles and cells when performing in vitro experiments. In other words, it is as important to consider the composition of the biomolecules in the media as it is to consider the chemical nature of the nanoparticle and the cell type. [emphasis mine]

“What’s absolutely clear is that depending on the type of dispersion that you make up, whether you add 10% serum or 20% serum, you get different levels of cell uptake” says Dawson. “Indeed, you get different levels of damage as well. It is therefore not meaningful to say that the nanoparticle is or is not toxic in that simplistic way. You can make a material toxic if you really want to make it toxic. You can make many materials damage cells simply because these have high surface energy. However, in a realistic physiological environment, part of the particle surface is covered and so that kind of damage would not be applicable.”

I encourage anyone who’s interested in nanotoxicology to read Walkey’s essay in full as I’ve excerpted only a portion.

BTW, Carl Walkey is a PhD graduate student at the University of Toronto and a member of the Integrated Nanotechnology & Biomedical Sciences Laboratory (INBS). I last mentioned Walkey in my July 12, 2012 posting about his Nanowerk Spotlight essay on nanotoxicology and animal studies.