May's Paper of the Month

Blood transfusions are life changing operations needed by many, yet donors – especially for rare blood groups – are hard to come by.  

Medical advancements in the last few decades have seen the average human life expectancy notably increase. However, despite improved medical techniques and procedures, the demand for blood is ever increasing. Donated blood is in short supply and has a limited shelf life while current in-vitro methods of culturing do not provide a sustainable supply suitable for clinical needs. 

May’s paper of the month by Trakarnsanga et al., discovered a method of creating an immortal red blood cell (RBC) supply. Through testing these RBCs have been shown to be molecularly and functionally similar to in vitro cultured RBCs. 

Stem cells are cells which are capable of proliferating into many - and sometimes all - types of cells. Previous in-vitro methods of culturing RBCs used the differentiating abilities of stem cells to produce RBCs from adult peripheral blood or umbilical cord blood stem cells. However, these RBCs have limited proliferation capacity and cells derived from cord blood often show fetal phenotypes. 

Trakarnsanga et al., produced the BEL-A (Bristol Erythroid Line Adult) line which was created through transducing early erythroid cells grown from adult bone marrow stem cells with a plasmid construct. Environmental control maintained these erythroid cells in an indefinitely proliferative state. The cultured cells could then be induced to complete maturation through removal of the inducing factor. The bloodgroup of the cultured RBC matched that of the cell donor while the protein expression profiles of these cells were found to be similar to in-vitro cultured RBCs. 

RBCs must be able to change shape under the stress of mechanical forces without rupturing. Testing this property in the BEL-A line is vital for clinical use. The group used the CSS450 shear stage, Imaging Station and Linkam imaging and control software to test the deformability of the cultured cells. The BEL-A line bound oxygen and had deformability indexes comparable to normal RBCs. 

Transplantation of the BEL-A line into a murine host also proved successful with no difference in survival rate between these mice and mice transplanted with donor RBCs. 

The group have created an immortal RBC line which through testing, matches in-vitro and normal RBCs in all categories tested. The discovery could provide a reliable and suitable blood source for those with rare blood groups and those requiring regular transfusions. Although more work will need to be done before clinical use, the ability to create RBCs through an immortal line could help alleviate the pressure of securing blood donors for patients and could prove life-changing for many.  

By Tabassum Mujtaba

Trakarnsanga, K. et al. An immortalized adult human erythroid line facilitates sustainable and scalable generation of functional red cells. Nat. Commun. 8, 14750 doi: 10.1038/ncomms14750 (2017).
 

April's Paper of the Month

Lithium ion batteries (LIBs) are heavily used in the portable electronics industry due to their low weight and high energy output. Although they are incredibly popular, improvements can be made in terms of capacity and replacing the volatile and flammable organic solvents within the batteries. 

This month’s paper of the month comes from the Warsaw University of Technology. They tested and researched different constituents of LIBs to increase conductivity and capacity of the ionic liquid-lithium salt binary system.  They did so by introducing lithium salt as a Li+ cation glyme solvent. By using the LTS120 system with a Raman spectrometer they could study phase transitions and salt dissociation, giving a better understanding of the conducting mechanism. 

Due to their great conductivity, Ionic liquids (ILs) could be a potential replacement for the dangerous solvents in LIBs. However, there are several issues with their incorporation. Firstly, ILs are produced on a small scale so they are very expensive. Secondly, their high melting points, poor compatibility with electrodes and other electrochemical properties make them less ideal as lithium conducting electrolytes. 

The research group created a new family of ILs to try and improve on the disadvantages of the classic ILs. The ionic salts were mixed with LiTDI salt to create a XMIm+TDI- LiTDI system. This formed a chain shaped [Li(TDI)2]nn- and XMIm+, but this system was found to be a poor conductor of lithium ions. 

Studies from another group found the solvent glyme, when mixed with LiTDI salt, creates a solvated Li(glyme)+ cation and Li polyanion system which is great for ionic conductivity as well as Li cation transference. Both qualities were desired in the Warsaw group’s BMIm+TDI- LiTDI system. 

Karpierz, E. et al. thus incorporated the solvent glyme into their system. Their ternary mixture consisted of an aggregated system of [Li(glyme)]+ cations and [Li(TDI)2]NN- anions dissolved in the ionic liquid BMIm+TDI-. They discovered the order and method of mixing affected the electrochemical properties of their system. They found that by mixing the LiTDI with the glyme first for at least six hours followed by the addition of the ionic liquid, it produces the system with the greatest conductivity.

The group have found a novel method of improving the ionic liquid-lithium salt binary system, which could have great potential application in lithium ion batteries.  

By Tabassum Mujtaba

Karpierz, E. et al. Ternary mixtures of ionic liquids for better salt solubility, conductivity and cation transference number improvement. Sci. Rep. 6, 35587; doi: 10.1038/srep35587 (2016).
 

March's Paper of the Month

Exposure to the environment can cause metallic materials to deteriorate but a 2D material coating may help protect against corrosion and oxidation. 

Metals are a significantly important material for a range of different industries including oil, chemical, aerospace, pharmaceutical and medical. However, metallic components exposed to the environment are prone to corrosion and oxidation. 

Various methods have been implemented to protect metals from corrosion, including galvanising, painting and electroplating. Recent studies have been looking at the potential benefits of using 2D materials as protective coatings for metals.  For example, graphene, the first 2D material to be discovered, is highly impermeable to liquids, gases and chemicals. It is also only one atomic layer thick and therefore would not affect the morphology of the metal. Such qualities make it an attractive candidate for coating metals. 

The potential problem with graphene is the high electronic conductivity and the direct contact with the metal could create a galvanic cell which over time would cause degradation of the metal. 

As such other 2D materials have been investigated. 

Hexagonal Boron nitride (hBN) has been studied as a potential alternative as it has the same permeability as graphene and does not form a galvanic cell. 

This month’s paper of the month comes from the Technical University of Denmark from the Micro & Nanotechnology department. They compared the protective properties of graphene and hBN under two oxidation environments, one simulating an acute and one a long-term. 

The group grew both materials on copper through chemical vapour deposition. They then conducted a variety of experiments to analyse their capability as barriers to corrosion and oxidation. This included Raman spectroscopy, x-ray photoemission spectroscopy and X-ray induced auger electron spectroscopy. 

To simulate the short acute oxidative conditions, the samples were first heated from room temperature to 400°C for 45 minutes. The second experiment was an isothermal experiment where samples were held at 50°C for 60 hours to simulate long-term oxidative conditions. 
They conducted the heating of their samples inside a custom Linkam LTS600, which was used in conjunction with a Raman microscope. 

The results from the Raman spectroscopy indicated graphene to be an effective oxidation barrier in the acute oxidative environment. Between temperatures 150°C to 300°C hBN was less effective which is assumed to be due to the higher density of grain boundaries and wrinkles, which are known to induce faster oxidation of the copper substrate.

However above 300°C the oxidation of the graphene coat increased as measured by the increase in the Raman intensity of the copper oxide peaks that were larger than that for hBN. 

Results from the isothermal experiment showed the barrier properties of graphene were effective only in short periods. After being held for 9 hours in 50°C, the oxidation of graphene resulted in an increase in copper oxide peaks. The failings of the graphene coat were due to the galvanic cell formation.  

The x-ray photoemission spectroscopy and x-ray induced Auger electron spectroscopy results showed hBN to be a better coating under the long term oxidative conditions. At 9 hours, the material showed little to no oxidation. After 40 hours there was a detectable increase in Cu(OH)2 but this was negligible compared to the graphene coated sample. 

They also showed the main peak on the surface of the graphene sample was copper oxide and copper for the hBN sample. The lack of a measurable oxide peak in the hBN sample demonstrates its superior ability as a protective barrier under long term oxidative conditions. 

When discussing the role of the LTS600, Dr Luca Camilli explained, “The system ‘window + heater’ enables the experiment to be possible. The heater allowed us to reach the desired temperatures for the oxidation experiments, while the window allowed us to study the oxidation process through Raman spectroscopy. The laser used for Raman passes through the window, impinges on the sample and is reflected back to the detector, through the window. “

Their research highlights another great potential application for 2D materials which would be greatly beneficial for many different industries. 

By Tabassum Mujtaba

Galbiati, M. et al. Real-time oxide evolution of copper protected by graphene and boron nitride barriers. Sci. Rep. 7, 39770; doi: 10.1038/srep39770 (2017).

February's Paper of the Month

There is great desire to create self-oscillating systems, such as the natural circadian rhythm of flowers, as such systems would have an incredible number of applications in different fields. 

In nature, it is common to find self-oscillating systems. These systems are either self-regulated or respond to external stimuli. Recreating this process synthetically is of great interest to scientists yet currently, there are only several attempted examples, all chemically driven and within non-dry systems. However, a light driven non-invasive system which would work in dry environments would prove to be much more useful. 

Self-oscillating actuators would have incredible application in self-cleaning devices and even as a renewable energy source, by converting solar energy into kinetic energy. 

February’s Paper of the Month is a collaboration between the Humboldt University of Berlin and the Eindhoven University of Technology. They attempted to address the need for an external stimulus driven actuator by creating a synthetic material which responds in an oscillatory fashion when exposed to a light stimulus. 

Azobenzenes are chemicals which can undergo a reversible reaction when exposed to light. These photo-reversible molecules are traditionally triggered by ultra-violet (UV) and blue light, causing a cis-trans isomerisation. This reaction can be utilised in self-oscillating actuators because of the reversible cis-trans isomerisations which make the film “move”. However, UV light eventually deteriorates the azobenzene, so creating a permanent self-oscillator requires tuning to less damaging electromagnetic waves such as visible light. 

Recent work has shown fluorinated azobenzene undergo cis-trans isomerisations with blue and green light, proving a viable candidate for incorporation into their actuator film research. 

They developed a liquid crystal polymer film doped with fluorinated azobenzene to test its oscillating prowess in the presence of only visible light. 

The liquid crystal film alignments were characterised using polarised light transmission microscopy and a THMS600. The THMS600 was used to determine the liquid crystal phase and alignment of the samples. The characterisation was vital for understanding and creating actuators with specific response properties. 

The polymer was sliced into a splay orientation to maximise film bending and was placed in sunlight. The exposure to light induced continuous bending in the polymer with no obvious frequency or pattern of oscillation.

Two superimposed freeze frames of the moving actuator. The red lines illustrate the top of the position of the film at the point the video was frozen. A notable change in position can be seen.  

To account for the effect of air currents, a control experiment was conducted by comparing the movements of a non-oscillating film with the fluorinated azobenzene film. The non-oscillator was created from a liquid crystal mixture and hydrogen azobenzene which is non-responsive to light. Both films were placed together and exposed to sunlight. The H-Azobenzene showed no movement indicating the oscillating behaviour in the fluorinated azobenzene was not due to air currents but the light induced changes in the film.   

Further experimentation found the experiments to be reversible with the number of cis and trans isomerisations determining the degree of bending. 
Professor Albert Schenning, from the Eindhoven University of Technology, said of the work:

 “A polymer actuator has been fabricated that is capable of continuous chaotic oscillatory motion when exposed to ambient sunlight in air. This work constitutes an important step towards the realisation of autonomous, persistently self-propelling machines and self-cleaning surfaces powered by sunlight. 

The actuator is based on a liquid crystalline polymer film doped with a visible light responsive fluorinated azobenzene. The alignment and the phase behaviour of the mixture was fully characterised by an optical microscope equipped with a Linkam hot stage. Such an analysis is crucial to prepare actuators with programmed response properties.”

Currently it is difficult to quantify the results but the experiments show promise for future applications in self-cleaning devices and possibly as a solar energy converter.  

By Tabassum Mujtaba

Kumar, K. et al. A chaotic self-oscillating sunlight-driven polymer actuator. Nat. Commun. 7:11975 doi: 10.1038/ncomms11975 (2016).