neutrinos nobel prize

Neutrinos and the Nobel Prize

Neutrino experiments are difficult and often ground-breaking. In (sometimes long-delayed) recognition of this, a number of pioneers of neutrino physics have been awarded the Nobel Prize for Physics.

1988	Leon Lederman, Melvin Schwartz, Jack Steinberger	for the neutrino beam method and the demonstration of the doublet structure of the leptons through the discovery of the muon neutrino
1995	Frederick Reines	for the detection of the neutrino
2002	Raymond Davis and Masatoshi Koshiba	for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos

In addition, Wolfgang Pauli (1945), Enrico Fermi (1938), and Lee and Yang (1957), who made major contributions to neutrino theory, won the Nobel Prize for work not directly connected with neutrinos. Clyde Cowan did not share in the belated prize for the discovery of the neutrino because Nobel prizes are not awarded posthumously.

The Nobel Prize in Physics 2015

The Nobel Prize in Physics 2015

The Nobel Prize in Physics 2015 was awarded jointly to Takaaki Kajita and Arthur B. McDonald "for the discovery of neutrino oscillations, which shows that neutrinos have mass"

Photo © Takaaki Kajita

Takaaki Kajita

Prize share: 1/2

Photo: K. MacFarlane. Queen's University /SNOLAB

Arthur B. McDonald

Prize share: 1/2

Our own genes can block HIV

                              Our own genes can block HIV

       Two groups of researchers at the University of Massachusetts Medical School say a powerful weapon against the AIDS virus may exist in the unlikeliest of places — in our own genes.

The studies, published online yesterday in the journal Nature, found that two genes can block HIV from spreading to other cells, which researchers in the HIV/AIDS field say could open the door to promising new treatments and could even pave the way for a cure.

Two groups of UMass Medical researchers used different methods in each study, but came to the same conclusion: the SERINC5 and SERINC3 genes can shut down the virus, stopping its spread and rendering it inactive.

But a component of the virus — the protein Nef — counteracts the SERINCs inhibiting powers, which is why those genes don’t prevent people from contracting the virus.

The finding, though, could very well lead to treatments that weaken the damaging protein and allow the virus-fighting genes to fend off illness, researchers say.

“Nef is a gene that HIV evolved largely to overcome this anti-viral factor that our cells make,” said Dr. Jeremy Luban, professor of molecular medicine at UMass Medical, an investigator in one of the studies.

“The hope is that there will be 
a way to intervene, perhaps by developing a new drug that 
allows the SERINCs to escape from Nef,” Luban said.

Ideally, the discoveries will lead to the development of treatments in the next five years, though it 
is difficult to estimate, Luban said.

The research, funded primarily by the National Institutes of Health, was done in collaboration with scientists at the Univer-
sity of Trento in Italy and the University of Geneva in Switzerland.

The discovery coincides with new HIV guidelines issued yesterday by the World Health Organization, increasing the number of those infected or at risk who should seek virus-inhibiting therapy by 9 million.

“Advancing science is a critical part of what needs to happen,” said Dr. Carlos Del Rio, chairman-elect of the HIV Medicine Association.

“Gene therapy advances for HIV are very exciting. They could lead to treatments that can cure HIV,” Del Rio said.

Though there are more than 30 of these therapies available, they can cause a range of side effects, from skin rashes and nightmares to weakened bones and cardiovascular disease, according to 
Dr. Daniel Kuritzkes, chief of 
Infectious Diseases at Brigham and Women’s Hospital.

“Not everyone tolerates the currently available regimen equally well,” Kuritzkes said.

“We still need to keep looking for new and improved treatments.”

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Cell Division and Cancer

Cancer cells are cells gone wrong — in other words, they no longer respond to many of the signals that control cellular growth and death. Cancer cells originate within tissues and, as they grow and divide, they diverge ever further from normalcy. Over time, these cells become increasingly resistant to the controls that maintain normal tissue — and as a result, they divide more rapidly than their progenitors and become less dependent on signals from other cells. Cancer cells even evade programmed cell death, despite the fact that their multiple abnormalities would normally make them prime targets for apoptosis. In the late stages of cancer, cells break through normal tissue boundaries and metastasize (spread) to new sites in the body.

How Do Cancer Cells Differ from Normal Cells?

In normal cells, hundreds of genes intricately control the process of cell division. Normal growth requires a balance between the activity of those genes that promote cell proliferation and those that suppress it. It also relies on the activities of genes that signal when damaged cells should undergo apoptosis.

Cells become cancerous after mutations accumulate in the various genes that control cell proliferation. According to research findings from the Cancer Genome Project, most cancer cells possess 60 or more mutations. The challenge for medical researchers is to identify which of these mutations are responsible for particular kinds of cancer. This process is akin to searching for the proverbial needle in a haystack, because many of the mutations present in these cells have little to nothing to do with cancer growth.

Different kinds of cancers have different mutational signatures. However, scientific comparison of multiple tumor types has revealed that certain genes are mutated in cancer cells more often than others. For instance, growth-promoting genes, such as the gene for the signaling protein Ras, are among those most commonly mutated in cancer cells, becoming super-active and producing cells that are too strongly stimulated by growth receptors. Some chemotherapy drugs work to counteract these mutations by blocking the action of growth-signaling proteins. The breast cancer drug Herceptin, for example, blocks overactive receptor tyrosine kinases (RTKs), and the drug Gleevec blocks a mutant signaling kinase associated with chronic myelogenous leukemia.

Other cancer-related mutations inactivate the genes that suppress cell proliferation or those that signal the need for apoptosis. These genes, known as tumor suppressor genes, normally function like brakes on proliferation, and both copies within a cell must be mutated in order for uncontrolled division to occur. For example, many cancer cells carry two mutant copies of the gene that codes for p53, a multifunctional protein that normally senses DNA damage and acts as a transcription factor for checkpoint control genes.

New Graphene __ Black Phosphorus

NEW GRAPHENE

Atoms-thin flakes of phosphorus have a crucial property that graphene lacks

Chemists first synthesized black phosphorus over a hundred years ago. But it was only last year when anybody really took interest in the flaky black stuff. In a series of experiments reported in the first half of 2014, researchers were able to exfoliate black phosphorus into very thin films of only about 10 to 20 atoms thick. Now black phosphorus has become the new darling of two-dimensional materials research and a new hope for a postsilicon world.

The excitement around black phosphorus, which is also called phosphorene in reference to its 2-D cousin graphene, stems mainly from the fact that it has an inherent bandgap, something that graphene lacks. A bandgap, an energy band in which no electron states can exist, is essential for creating the on/off flow of electrons that are needed in digital logic and for the generation of photons for LEDs and lasers.

Black phosphorus doesn’t just have any bandgap. Its bandgap can be fine-tuned by adjusting the number of layers of the material, explains Philip Feng, an assistant professor of electrical engineering and computer science at Case Western Reserve University.

The bandgap can be dialed up from 0.3 to 2.0 electron volts. That’s a range covering a regime otherwise unavailable to all other recently discovered 2-D materials. It bridges the bandgaps of graphene (0 eV) and of transition-metal dichalcogenides such as molybdenum disulfide, which range from 1.0 to 2.5 eV.

By combining this bandgap tuning with different choices of contact materials, scientists at Sungkyunkwan University, in South Korea, were recently able to build both n-type transistors—those conducting electrons—and ambipolar transistors, which conduct both holes and electrons. Such a mix brings the material closer to mimicking the complementary logic used in today’s silicon chips.

Scientists are also excited about black phosphorus for photonics, “since optoelectronic functions, including light absorption, emission, and modulation, of semiconductor materials depend on the size of the bandgap,” says Mo Li, a photonics expert at the University of Minnesota. Black phosphorus’s bandgap range means it can absorb and emit light with wavelengths of 0.6 to 4.0 micrometers—covering the visible to infrared. That spectrum could be key to its use in sensors and in optical.

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Graphene Keeping It Cool In Electronics

By Dexter Johnson

Cooling fans and other system-level solutions are reaching their limits as circuit densities continue to grow. It’s no wonder then that graphene’s remarkable heat conductivity has led to a lot of research into using it to forthermal management in electronics.

Now an international team of researchers, organized by a team at the University of Michigan, has found that layered graphene can be an important tool for thermal management because of its ability to release heat efficiently.

In research published in the journal Nature Communications, the scientists demonstrated that the electrostatic interactions between electrically charged particles—known as Coulomb interactions—in  different layers of multi-layered graphene offers a key mechanism for dispersing heat. This occurs despite the fact that all electronic states are strongly confined within individual 2D layers.

“We believe that this cooling mechanism is not limited to multilayer graphene samples but is likely to be important in many other new, layered nanomaterials under active development by the scientific community,” said Theodore Norris, who led the research, in a press release.

This mechanism came as a bit of surprise to the researchers. They did not expect the heat building up in the electrons of the graphene to travel well through the layers because previous observations had shown that the graphene layers interact too strongly for this to occur. This stood in contrast to 3D pieces of silicon that are capable of conducting heat in any direction.

Momchil Mihnev, a doctoral student at the University of Michigan and first author on the paper, explained in the press release that while the electrons in the different layers can’t mechanically come in contact with each other, they do manage to interact with each other through their electrical charges.

When the negative charges repel each other, the electrons take on an effective size that extends between the layers. When the electrons come in contact with each other in this way, the hotter electrons transfer heat to the colder ones. This transfer of heat eventually channels down through the graphene towards the layer that is closest to the silicon carbide substrate the researchers used in these experiments. Once it gets to the final layer of graphene, the heat transfers into the silicon carbide.

The researchers have developed a detailed theory on why and how this mechanism works, and it could provide an important tool in keeping electronics cool well into the future.

cancer cell growth

Bacterial Sepsis Protein May Inhibit Cancer Cell Growth

A toxin secreted by Vibrio vulnificus, a water and food-borne bacteria that can cause rapidly lethal infections in persons with liver disease, has potential to prevent the growth of tumors, according to a new study by Northwestern Medicine scientists.

Karla Satchell, a professor in microbiology-immunology at Northwestern University Feinberg School of Medicine, and her team demonstrated in a paper in Nature Communications, that a multifunctional-autoprocessing repeats-in-toxin (MARTX) protein from Vibrio vulnificus can inhibit tumor cell growth by cutting the protein Ras. This protein is central to cell division and survival, and mutations in the gene that codes for Ras are a common cause of human malignancies.

"Ras is important for cell proliferation in cancer, so the toxin could potentially be developed as a treatment for different types of tumors," Satchell says. 'It has been known that Ras has a role in cancer development and targeting Ras has been one of the hardest challenges of cancer research and drug discovery.'

Ras also plays a role in detecting pathogens and activating an immune response. The bacterium uses the MARTX toxin protein to inactivate Ras, increasing its own virulence and allowing it to spread throughout the host.

They used cell biological, genetic and biochemical techniques to show how a specific part of the toxin, an effector domain called DUF5Vv, targets and cleaves Ras. Satchell's team also revealed the ability of this domain to slice both normal and mutant forms of Ras commonly found in cancers.

"What is unique about this study is the ability of the toxin to cleave Ras, rather than modify it, which is a novel mechanism for inactivating Ras," Satchell says.

The scientists plan to continue to study the mechanisms and biochemistry of the MARTX toxin specificity to the Ras protein.

The research was funded by National Institutes of Health grants R01AI051490, R01AI092825, R01AI098369, R01CA152601, R01CA152799, R01CA168292 and a Northwestern University Avon Center of Excellence grant and by the Northwestern Medicine Catalyst Fund.

Source: Northwestern University

http://www.infectioncontroltoday.com/news/2015/06/bacterial-sepsis-protein-may-inhibit-cancer-cell-growth.aspx

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polymeric nanoparticles

New technique precisely controls size and shape 

of polymeric nanoparticles

Over the last twenty years, scientists have developed many techniques to synthesize polymeric nanoparticles for a wide range of applications including surface coating, sensor technology, catalysis, and nanomedicine.These so-called reversible-deactivation radical polymerization (RDRP) techniques have provided researchers with powerful tools to synthesize well-defined macromolecules with predetermined molecular weight, low polydispersity, and precisely defined end groups.However, the precise control of the size and shape of polymer nanoparticles remains challenging, and RDRP techniques still fall well short of producing large, well-defined macromolecules with the same size and degree of precision as nature (proteins, nucleic acids, etc.).In new work, researchers at The Australian Research Council Centre of Excellence in Convergent Bio-Nano Science & Technology (CBNS) at Monash University, led by Professor Thomas Davis, have developed a new technique to precisely control the size and shape of polymeric nanoparticles.The scientific core of these findings lies in a novel stabilizer of nanoparticles that provide the precise control over particle size and a novel self-assembly method for the synthesis of various nanoparticle shapes. In combination with traditional techniques, this new method provides a useful approach for reproducibly generating an extensive library of nanostructured particles with different sizes and shapes.The team reports their findings in recent online editions of Polymer Chemistry ("Rapid synthesis of ultrahigh molecular weight and low polydispersity polystyrene diblock copolymers by RAFT-mediated emulsion polymerization") and in ACS Macro Letters ("Reproducible Access to Tunable Morphologies via the Self-Assembly of an Amphiphilic Diblock Copolymer in Water").

Various nanoparticle 

shapes synthesized by The Australian Research Council Centre of Excellence in Convergent Bio-Nano Science & Technology at Monash University.By using a novel macromolecular chain transfer agents (CTA) in reversible addition fragmentation chain transfer polymerization (RAFT)-mediated emulsion polymerization, the researchers have overcome a long-standing challenge in the synthesis of UHMW polymers and created a new nanomaterial with promising potential."Our synthesis technique has the following advantages," Nghia Truong Phuoc, a Postdoctoral Research Fellow at CBNS, tells Nanowerk: "1) ultrafast synthesis; 2) narrow distribution of particle sizes; 3) precise control over both molecular weight and particle size; 4) no use of organic solvents; 5) high solids content; 6) excellent stability; and 7) tunable morphologies."This makes the method very useful for the preparation of polymeric nanoparticles with predetermined size (from 20 nm to 200 nm) and shape (e.g., sphere, vesicle, worm, flower, etc.), opening the door to novel industrial, sensing and medical applications.Beside traditional applications, polymeric nanoparticles made via this novel technique could have great potential in biomedical engineering. For example, as Truong explains, worm-like nanoparticles can evade clearance by the immune system and achieve prolonged circulation time, which is a special feature similar to that of certain rod-shaped bacteria, viruses, and fungi found in nature."They also have the ability to accumulate in tumors to a very high concentration – i.e., up to 30 wt % of the injected dose – and achieve a higher antitumor efficacy when compared to spheres and vesicles," he points out. "In addition, nanoparticles with rare morphologies such as large compound vesicles and flower-like vesicles are rapidly taken up by cells and able to escape endolysosomal cellular transport compartments."Going forward, the researchers plan to study the structure-property relationship of nano-bio interactions occurring between these novel nanoparticles with biological systems, which could eventually provide highly efficient nanocarriers for drug and gene delivery.The ultimate goal for researchers in this field is to synthesize a library of polymeric nanoparticles possessing different sizes, shapes, surfaces, and cores to render different physicochemical properties which could support vastly different applications in biotechnology and medicine.By Michael Berger. Copyright © Nanowerk

 

Read more: New technique precisely controls size and shape of polymeric nanoparticles 

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Benign tumor

UAE hospital doctors remove rare tumour

A medical team in Sheikh Khelifa Specialty Hospital in Ras Al Khaimah (SKSH-RAK) succeeded in conducting an operation to remove a rare benign tumour for a UAE patient aged 58. The patient was suffering from shortness of breath due to a big mass of 3.5 cm that blocked her airway 

path at just behind the tongue.

Dr. Myung-Whun Sung, CEO of SKSH-RAK and head of the team who conducted the operation, stated that the surgery which took three hours had been done in three medical procedures to remove the rare tumor. “The tumour consisted of a vascular mass inside the airway track in the neck, anatomically called the hypopharynx; the patient had several previous CT scans and MRI in two different hospitals in the UAE but did not get the final. 

He noted that the patient who was referred to Sheikh Khelifa Specialty Hospital in Ras Al Khaimah (SKSH-RAK), conducted MRI to make a correct diagnosis of the mass  and to check its vascularity. The tests proved that the mass has blocked the airway and trachea causing severe shortness of breath. An MRI was done to define the size of the tumour since it was in a sensitive area.

Dr. Sung emphasized that prior to the operation, the surgeons conducted an important procedure called 'angiography embolization' to confirm the diagnosis and prevent any significant bleeding during the operation. “We then had to do the operation within a couple of days to have this preoperative procedure effective. ”, he said.

He added that the operation was conducted by a team of three doctors, achieving a successful complete removal of the tumor with minimal blood loss, and reconstructed the airway at the same time enable the patient to breath. The histopathologic diagnosis of the tumor was “paraganglioma”, which is rare but notorious for its difficulty in operation due to high Speaking about the condition of the patient. 

Dr. Sung said she is now in a good health condition and the operation was successful with no complications. We are waiting for her complete recovery to discharge her from the hospital in a few days.

“The procedures we have done before the operation made us able to define the size and type of the tumor and definitely led to its successful treatment. This uncommon case required a step-by-step team approach including radiological intervention and skilled surgery.”, he 

concluded.

source :   http://www.emirates247.com/news/emirates/uae-hospital-doctors-remove-rare-tumour-2015-06-05-1.592825

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Nano Drug Made From Lemon Juice Cures Jaundice Faster: Scientists 

 

 

Indian scientists recently claimed that the age-old home remedy of treating jaundice with lemon juice is one the fastest methods of treating the disease. The claim came after the scientists created a nano drug from the squeezed lemon juice to notice the speed and accuracy by which it treats the disease.
The nano particles developed by the scientists break down the bilirubin in the human body. Bilirubin is the pigment found in the bile juice produced by the liver. Higher levels of bilirubin in the blood are a marker of certain diseases, including jaundice. The discovery is believed to have opened new avenues in the field of nano medicine in the country.
"High levels may lead to brain damage or even death in newborns and adults, if not treated. To combat this, we designed manganese oxide nano particles capped with citrate, a derivative of citric acid found in citrus fruits such as lemons," said lead researcher Nabarun Polley, reported the Times of India. Polley further said that the new nano-hybrid efficiently brings down the level of bilirubin in blood by degrading the pigments.
Polley and his colleagues tested the nanoparticle in the lab on mice. According to the researchers, the nanoparticles are completely safe and compatible. In addition, the team claimed that the nano-hybrid is target-specific -- that is, it acts directly and already identifies the bilirubin pigments on which it needs to act. Therefore, the use of the nanoparticles thus eliminates its chances of targeting any other organ in the human body.
The study will be published in the Nanomedicine journal.

Contact the writer at: emailtoguneet@gmail.com.

for more ; http://www.ibtimes.com/nano-drug-made-lemon-juice-cures-jaundice-faster-scientists-1923859

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5 simple tips to prevent jaundice _ nanomedicine

Indian scientists working on nano medicine treatment for jaundice

The age-old home remedy for jaundice - nimbu paani or lemon juice – has now got a 21st century spin, thanks to Indian scientists. They have literally squeezed lemons to nano-dimensions to create a nanodrug for speedy and accurate therapy of the disease. Here are 5 simple tips to prevent jaundice.

Widening the scope of nanomedicines in India, scientists in West Bengal have designed special nanoparticles that break down bilirubin – the yellow pigment found in bile, a fluid made by the liver. Essential to liver health, higher than normal levels of bilirubin in blood (hyperbilirubinemia), may indicate certain diseases, including jaundice, in adults as well as newborns. Now, a smartphone app that detects jaundice in babies.

High levels may lead to brain damage or even death in newborns and adults, if not treated. To combat this, we designed manganese oxide nanoparticles capped with citrate, a derivative of citric acid found in citrus fruits such as lemons,’ Nabarun Polley, of S. N. Bose National Centre for Basic Sciences, Kolkata, told IANS. Polley, a senior researcher at the Centre’s department of chemical, biological and macro-molecular sciences, explained that this nano-hybrid helps to degrade bilirubin and bring it down to a normal level swiftly. ‘It is actually like nimbu paani administered through nanoparticles,’ said Polley, adding lemon juice is usually suggested due to its cleansing nature. Use these home remedies to relieve the symptoms of jaundice or hepatitis.

Through experiments performed on lab mice, Polley and his co-investigators at Jadavpur University and Dey’s Medical, showed the nanoparticles to be safe, compatible with the body, and proved that they had the ability to act directly and specifically on the target-bilirubin.This ensures the nanodrug doesn’t affect any organ. There were no toxic effects after the particles were injected into the mice and parameters like blood cell count didn’t change,’ said collaborator Soumendra Darbar, research and development division, Dey’s Medical Stores (Mfg.) Ltd. Read: 8 jaundice symptoms you need to watch out for.

In fact, this precision which is the product’s USP, also takes care of the time factor. ‘It brought down high bilirubin levels within two hours (in mice) while the commercially available drug silymarin took more than a day to control the levels for the equivalent dose,’ said Polley, adding the group has been working on this specific nanoparticle for the last five years.

The latest findings, which are currently in press for publication in the Nanomedicine journal, open a new door for ‘cost-effective and efficient therapeutic treatment of hyperbilirubinemia, jaundice and associated diseases,’ according to group leader Samir Kumar Pal. ‘We have been working on detection as well as the treatment aspect of elevated bilirubin. In the near future, we could help avoid preventable deaths of newborns,’ said Pal, professor at the Centre’s department of chemical, biological and macro-molecular sciences. 

Union Minister of Science and Technology Harsh Vardhan, post his visit to Pal’s lab recently, had highlighted on Facebook that neonatal jaundice deaths, comprise 18 percent of newborn mortality in India. He was particularly impressed with a non-invasive, computer-based fibre-optic detector fabricated by the group that detects bilirubin levels within three seconds by shining light on the white part of one’s eye.

‘Nanomedicine has huge potential for India as it has elsewhere in the world. Specially, diagnostics promises to offer cheap and faster way for detecting diseases for India. This has a huge potential for India because our healthcare is not as widespread,’ said Praveer Asthana, Mission Director, Nano Mission,Department of Science & Technology, India.

Source: IANS

http://www.thehealthsite.com/news/indian-scientists-working-on-nano-medicine-treatment-for-jaundice/

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carbon nanotube

Particle Characterization and Centrifugation Tools from Beckman Coulter for Nanomedicine Applications

Carbon Nanotube Preparation

Single-walled carbon nanotubes (Sigma-Aldrich) and 0.2% 1, 2-distearoyl-phosphatidylethanolamine -methyl-polyethyleneglycol (DSPE-mPEG, 5 kDa molecular weight, Laysan Bio) were mixed in 10mL of water. Well-dispersed carbon nanotubes were created by bath sonicating the solution for 30 minutes, as per previously established procedures.  

5 mL of SWCNT was centrifuged  in open-top polycarbonate centrifuge tubes (Beckman Coulter P/N 343778) at 22°C, 55,000 RPM (~I31,000 x g) for two minutes using a TLA-120.2 rotor in an Optima MAX-XP Ultracentrifuge. The top 650µL of supernatant was collected carefully to avoid disrupting the pelleted aggregates.

Using 10 kDa, Amicon Ultra 0.5 mL Centrifugal Filters (Millipore) with a Beckman Coulter Microfuge 20 microcentrifuge, concentration of the ultracentrifuged SWCNT(UCF’d SWCNT) and the uncentrifuged SWCNTs (As made SWCNT) was performed.

Measurement of the concentration was carried out using a UV-Vis-NIR spectrophotometer (Paradigm, Molecular Devices) and the established mass extinction coefficient of SWCNTs at 808nm of 46.5L/g*cm2 Deionized water was used to dilute the concentrated  UCF'd SWCNTs and As-Made SWCNTs to 0.6mg/mL, 0.3mg/mL, and 0.06mg/mL concentrations.

Toxicity Assay

24 hours prior to adding nanotubes, MCF-7 breast cancer cells were plated at a density of 0.08 x 106 per well in a 24-well plate with 900µL of RPMI/10% FBS (Invitrogen). Using one of the wells before nanotubes were added, cell growth and viability were confirmed. On the next day, 100µL of SWCNT samples were added to the wells.

In total, there were six SWCNT groups (n=2/group):

• 0.06 mg/mL UCF'd SWCNTs
• 0.06 mg/mL As-Made SWCNTs
• 0.03 mg/mL UCF'd SWCNTs
• 0.03 mg/mL As-Made SWCNTs
• 0.006 mg/mL UCF'd SWCNTs
• and 0.006 mg/mL As-Made SWCNTs.

To provide a control, 100µL of DSPE-mPEG only sample was added to the wells.  

In total, there were three surfactant buffer control groups (n=2/group):

• 0.2 mg/mL DSPE-mPEG;
• 0.02 mg/mL DSPE-mPEG;
• 0.002 mg/mL DSPE-mPEG.

Lastly, control 1 (n=1) was a complete control, with cells left untouched and 100µl of sterilized water was added to control 2(n=1). After 24 hours, in order to enable counting in the Vi-CELL XR, all wells were rinsed using PBS and then trypsinized and mixed in 1mL of PBS. To minimize aggregated nanotubes being counted as cells a novel cell type was developed using the Vi-CELL XR software. Comparison of cell viability and difference in the two solutions was carried out using the percentages of viable cells.

Figure 2. Cell Imaging. MCF-7 cells were imaged under an optical microscope after 24 hours of incubation with SWCNT. The cells, incubated with either 0.06 mg/mL As-Made SWNT (left image) or 0.06 mg/mL ultracentrifuged SWNT (right image), have not yet reached confluence. Black aggregates of SWNT can be seen in the image on the left; these aggregates are difficult to wash away without washing away the cells as well. The aggregates have absorption and fluorescence properties that will skew traditional toxicity assays.

Figure 3. Viability Results. At all concentrations, ultracentrifuged SWCNT (designated by UC) had minimal toxicity; 75% or more of the MCF-7 cells remained viable 24 hours after incubation. Contrastingly, SWCNT that were not centrifuged and contained aggregated species (designated by AG) had increasing toxicity toward MCF-7 cells that scaled with increasing concentration. At a stock concentration of 0.6 mg/mL, corresponding to a concentration in solution with cells at 0.06 mg/mL, the aggregated SWCNTs had greater than 50% cell death.

Results and Discussion

One of the key challenges of nano-biomedicine is aggregated nanoparticles. This article examined the  toxicity of As-Made SWCNTs (which included visible aggregates); however, this information is representative of most nanoparticles. The SWCNTs were separated into the As-Made group and the ultracentrifuged group. The former group did not undergo any purification for aggregate removal while the latter underwent ultracentrifugation in the Beckman Coulter Optima MAX-XP ultracentrifuge.

Although centrifugation is effective for the removal of aggregated nanoparticles, the research workflow is somewhat hindered by long centrifugation times, of at least 6 h at low speeds (5,000 x g to 22,000 x g). This new ultracentrifugation technique shows that a high-speed, two-minute ultracentrifugation can achieve the same biocompatibility and individual solubilized SWCNTs as the longer centrifugation time can, offering researchers a 180-fold time saving.

Dynamic light scattering data and optical images captured with the DelsaMax PRO provide proof that all aggregated SWCNT has been eliminated using the rapid ultracentrifugation. It was possible to collect the toxicity data in this study because  Vi-CELL XR was used; aggregates have a strong absorption that would confound typical MMP and MTT toxicity assays.

The Vi-CELL XR was programmed to specifically look for spherical cells having defined outlines in a sharply delineated size range, to minimize the counting  of carbon nanotube aggregates as either dead or viable. Due to the large number of aggregates present even after cell washing, the  Vi-CELL XR optimization is very important.

Ultracentrifuged nanotubes were run without any cells, as a control, and in this trial, the  Vi-CELL XR did not count a single cell as dead or live.

Figure 4. Size Distribution Data. Single-walled carbon nanotubes, after sonication in surfactant, still have a number of aggregated species. Size distribution, determined by Dynamic Light Scattering on the DelsaMax PRO, showed two broad species (red line). The first size range, roughly 100 nm in diameter, represents individually solubilized carbon nanotubes. The second species, containing mostly aggregated carbon nanotubes, has a diameter peak closer to one micron in size. After a two-minute ultracentrifugation, the SWNT demonstrate only a single broad species at 100 nm, indicating that virtually all aggregates have been removed. This is further indicated by a 59% decrease in polydispersity. Interestingly, the zeta potential remains unchanged between aggregated and centrifuged carbon nanotubes. This is most likely due to the fact that steric repulsion, from the Poly(ethylene glycol) surfactant, provides most of the stability to the carbon nanotubes, while electrostatic repulsion does not play a major role.

Figure 5. Flowchart

Conclusions

Compared with  ultracentrifuged SWCNT, aggregates show higher toxicity, something that can be attributed to poor surfactant coverage and the larger size of aggregated SWCNT. The surfactant-free surface is more exposed in aggregated SWCNT and this increased surface availability of SWCNT contributes directly to increasing the reactive oxygen species (ROS). Also, on the whole, As-Made or aggregated SWCNTs are much larger, as shown by the dynamic light scattering data. The larger size of  SWCNT can block cell-signaling pathways or hinder cellular action and thereby inhibit cell growth. It is therefore essential that removal of aggregated nanoparticles is performed before being used in vitro or in vivo.

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