Tag Archives: protein

Shape-conforming hydrogel and the body’s own healing mechanisms

A June 11, 2018 news item on ScienceDaily announces a development of interest to people with diabetes or those who treat them,

A simple scrape or sore might not cause alarm for most people. But for diabetic patients, an untreated scratch can turn into an open wound that could potentially lead to a limb amputation or even death.

A Northwestern University team has developed a new device, called a regenerative bandage, that quickly heals these painful, hard-to-treat sores without using drugs. During head-to-head tests, Northwestern’s bandage healed diabetic wounds 33 percent faster than one of the most popular bandages currently on the market.

A June 11, 2018 Northwestern University news release by Amanda Morris, which originated the news item, provides more detail,

“The novelty is that we identified a segment of a protein in skin that is important to wound healing, made the segment and incorporated it into an antioxidant molecule that self-aggregates at body temperature to create a scaffold that facilitates the body’s ability to regenerate tissue at the wound site,” said Northwestern’s Guillermo Ameer, who led the study. “With this newer approach, we’re not releasing drugs or outside factors to accelerate healing. And it works very well.”

Because the bandage leverages the body’s own healing power without releasing drugs or biologics, it faces fewer regulatory hurdles. This means patients could see it on the market much sooner.

The research was published today, June 11 [2018], in the Proceedings of the National Academy of Sciences. Although Ameer’s laboratory is specifically interested in diabetes applications, the bandage can be used to heal all types of open wounds.

An expert in biomaterials and regenerative engineering, Ameer is the Daniel Hale Williams Professor of Biomedical Engineering in the McCormick School of Engineering, professor of surgery in the Feinberg School of Medicine and director of Northwestern’s new Center for Advanced Regenerative Engineering (CARE).

The difference between a sore in a physically healthy person versus a diabetic patient? Diabetes can cause nerve damage that leads to numbness in the extremities. People with diabetes, therefore, might experience something as simple as a blister or small scratch that goes unnoticed and untreated because they cannot feel it to know it’s there. As high glucose levels also thicken capillary walls, blood circulation slows, making it more difficult for these wounds to heal. It’s a perfect storm for a small nick to become a limb-threatening — or life-threatening — wound.

The secret behind Ameer’s regenerative bandage is laminin, a protein found in most of the body’s tissues including the skin. Laminin sends signals to cells, encouraging them to differentiate, migrate and adhere to one another. Ameer’s team identified a segment of laminin — 12 amino acids in length — called A5G81 that is critical for the wound-healing process.

“This particular sequence caught our eye because it activates cellular receptors to get cells to adhere, migrate and proliferate,” Ameer said. “Then we cut up the sequence to find the minimum size that we needed for it to work.”

By using such a small fragment of laminin rather than the entire protein, it can be easily synthesized in the laboratory — making it more reproducible while keeping manufacturing costs low. Ameer’s team incorporated A5G81 into an antioxidant hydrogel bandage that it previously developed in the laboratory.

The bandage’s antioxidant nature counters inflammation. And the hydrogel is thermally responsive: It is a liquid when applied to the wound bed, then rapidly solidifies into a gel when exposed to body temperature. This phase change allows it to conform to the exact shape of the wound — a property that helped it out-perform other bandages on the market.

“Wounds have irregular shapes and depths. Our liquid can fill any shape and then stay in place,” Ameer said. “Other bandages are mostly based on collagen films or sponges that can move around and shift away from the wound site.”

Patients also must change bandages often, which can rip off the healing tissue and re-injure the site. Ameer’s bandage, however, can be rinsed off with cool saline, so the regenerating tissue remains undisturbed.

Not only will the lack of drugs or biologics make the bandage move to market faster, it also increases the bandage’s safety. So far, Ameer’s team has not noticed any adverse side effects in animal models. This is a stark difference from another product on the market, which contains a growth factor linked to cancer.

“It is not acceptable for patients who are trying to heal an open sore to have to deal with an increased risk of cancer,” Ameer said.

Next, Ameer’s team will continue to investigate the bandage in a larger pre-clinical model.

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

Potent laminin-inspired antioxidant regenerative dressing accelerates wound healing in diabetes by Yunxiao Zhu, Zdravka Cankova, Marta Iwanaszko, Sheridan Lichtor, Milan Mrksich, and Guillermo A. Ameer. PNAS [Proceedings of the National Academy of Science] June 11, 2018. 201804262; published ahead of print June 11, 2018. https://doi.org/10.1073/pnas.1804262115

This paper is behind a paywall.

‘Golden’ protein crystals

Yet another use for gold. From a March 14, 2017 news item on Nanowerk (Note: A link has been removed),

Scientists from the London Centre for Nanotechnology (LCN) have revealed how materials such as gold can help create protein crystals. The team hope their findings, published in the journal Scientific Reports (“Protein crystal nucleation in pores”), could aid the discovery of new medicines and treatments. The Lead author; Professor Naomi Chayen states that “Gold doesn’t react with proteins, due to its inert nature, which makes it an ideal material to create crystals”.

Image: Crystals of an antibody peptide complex related to AIDS research Courtesy: LCN

A March 14, 2017 (?) LCN press release, which originated the news item, expands on the theme,

Proteins are crucial to numerous functions in the body – yet scientists are still in the dark about what most of them look like. This is because the most powerful way of revealing the structure of proteins is to turn them into crystals, and then analyse these with X-rays. However, persuading proteins to turn into useful crystals is notoriously difficult. All crystals start from a conception stage when the first molecules come together; this is called nucleation. But reaching nucleation is often difficult as it requires a lot of energy – and many proteins simply can’t overcome this barrier. Scientists also struggle to create medicines that bind to particular proteins – for instance a protein involved in cancer formation, if they don’t know the protein’s structure.

“How can you target a protein if you have no idea what it looks like? It’s like recognising a face in a crowd – you need a picture,” explained Professor Naomi Chayen, lead author of the research.

Forcing molecules together with gold

One technique for allowing proteins to reach their nucleation point is to trap them in tiny holes. This forces the molecules together, which helps them overcome the energy barrier needed to trigger the first crystal. One material that scientists have found to be effective at growing crystals is gold. Creating many holes in the metal creates a substance called porous gold, which acts as a perfect environment for growing crystals, explained Professor Chayen: “Gold doesn’t react with proteins, due to its inert nature, which makes it an ideal material to create crystals. Creating holes in the metal enable it to act a bit like coral, with each hole providing an ideal environment to harbour crystals.”

Creating crystals

In the latest research, the team investigated the best size hole needed to create crystals. They found that a variety of different sized holes produced the highest quality crystals. Most holes were around 5-10nm, just slightly larger than the width of a human hair. Professor Chayen explained: “Imagine walking down a street with many potholes – some of the holes will be big enough for me to step out of, while some will be too small for my foot to fall into. “However, some will be the exact size of my foot, and will trap me in them. This is the same principle as having different pore sizes – it allows us to trap different size protein molecules, enabling them to form crystals.”

She added that the findings which give a simple explanation of why, and under what conditions porous materials can induce protein crystal nucleation may help scientists design porous materials that would produce the highest quality crystals.

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

Protein crystal nucleation in pores by Christo N. Nanev, Emmanuel Saridakis & Naomi E. Chayen. Scientific Reports 7, Article number: 35821 (2017) doi:10.1038/srep35821 Published online: 16 January 2017

This is an open access article.

Barnacle footprints could be useful

An Aug. 18, 2016 news item on Nanowerk describes efforts by scientists at the University of Twente (The Netherlands) and A*STAR (Singapore) to trace a barnacle’s footprints (Note: A link has been removed),

Barnacle’s larvae leave behind tiny protein traces on a ship hull: but what is the type of protein and what is the protein-surface interaction? Conventional techniques can only identify dissolved proteins, and in large quantities. Using a modified type of an Atomic Force Microscope, scientists of the University of Twente in The Netherlands and A*STAR in Singapore, can now measure protein characteristics of even very small traces on a surface. They present the new technique in Nature Nanotechnology (“Measuring protein isoelectric points by AFM-based force spectroscopy using trace amounts of sample”).

An Aug. 16, 2016 University of Twente press release, which originated the news item, explains how the ‘footprints’ could lead to new applications for ships and boats and briefly describes the technical aspects of the research,

In infection diseases, membrane fouling, interaction with bacteria, as well as in rapid healing of wounds for example, the way proteins interact with a surface plays an important role. On a surface, they function in a different way than in solution. On a ship hull, the larvae of the barnacle will leave tiny traces of protein to test if the surface is attractive for long-term attachment. If we get to know more about this interaction, it will be possible to develop surface conditions that are less attractive for the barnacle. Large amounts of barnacles on a ship will have a destructive effect on flow resistance and will lead to more fuel consumption. The new measuring method makes use of a modified Atomic Force Microscope: a tiny ball glued to the cantilever of the microscope will attract protein molecules.

Modified AFM tip with a tiny ball that can attract protein molecules

FORCE MEASUREMENTS

An amount of just hundreds of protein molecules will be sufficient to determine a crucial value, called the iso-electric point (pI): this is the pH-value at which the protein has net zero electric charge. The pI value says a lot about the surroundings a protein will ‘feel comfortable’ in, and to which it preferably moves. Using the AFM microscope, of which the modified tip has collected protein molecules, it is possible to perform force measurements for different pH values. The tip will be attracted or repelled, or show no movement when the pI point is reached. For these measurement, the researchers made a special reference material consisting of several layers. Using this, the effect of a number of pH-values can be tested until the pI value is found.

The traces the larve leaves behind (left) and force measurements (right)

PAINT CHANGE

The tests have been successfully performed for a number of known proteins like fibrinogen, myoglobine and bovine albumin. And returning to the barnacle: the tiny protein footprint will contain enough molecules to determine the pI value. This quantifies the ideal surface conditions, and using this knowledge, new choices can be made for e.g. the paint that is used on a ship hull.

The research has been done within the group Materials Science and Technology of Polymers of Professor Julius Vancso, in close collaboration with colleagues of A*STAR in Singapore – Prof Vancso is a Visiting Professor there as well. His group is part of UT’s MESA+ Institute for Nanotechnology.

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

Measuring protein isoelectric points by AFM-based force spectroscopy using trace amounts of sample by Shifeng Gu, Xiaoying Zhu, Dominik Jańczewski, Serina Siew Chen Lee, Tao He, Serena Lay Ming Teo, & G. Julius Vancso.  Nature Nanotechnology (2016) doi:10.1038/nnano.2016.118 Published online 25 July 2016

This paper is behind a paywall.

Dragonfly and locust rubber

There’s a protein in some insects such as dragonflies, mosquitoes (!) and locusts which is superior to synthetic rubber according to a July 30, 2013 news release from the American Chemical Society (ACS) [also on EurekAlert],

Kristi Kiick and colleagues explain that scientists discovered resilin a half-century ago in the wing hinges of locusts and elastic tendons of dragonflies. The extraordinary natural protein tops the best synthetic rubbers. Resilin can stretch to three times its original length, for instance, and then spring back to its initial shape without losing its elasticity, despite repeated stretching and relaxing cycles. That’s a crucial trait for insects that must flap or jump millions of times over their lifetimes. Scientists first synthesized resilin in 2005 and have been striving to harness its properties in medicine.

Kiick’s team describes how their own research and experiments by other scientists are making major strides toward practical applications of resilin. Scientists have modified resilin with gold nanoparticles for possible use in diagnostics, engineered mosquito-based resin to act like human cartilage and developed a hybrid material for cardiovascular applications. “This increasing amount of knowledge gained from studies on natural resilin and resilin-like polypeptides continues to inspire new designs and applications of recombinant resilin-based biopolymers in biomedical and biotechnological applications,” the scientists state.

Illustrating 'insect rubber' [downloaded from http://pubs.acs.org/doi/full/10.1021/mz4002194]

Illustrating ‘insect rubber’ [downloaded from http://pubs.acs.org/doi/full/10.1021/mz4002194]

Here’s a link to and a citation for the researchers’ biomimicry paper published by ACS Macro Letters,

Resilin-Based Materials for Biomedical Applications by Linqing Li and Kristi L. Kiick. ACS Macro Lett., 2013, 2, pp 635–640 DOI: 10.1021/mz4002194 Publication Date (Web): July 11, 2013
Copyright © 2013 American Chemical Society

This paper is open access.

Femtosecond laser writing and lenses

I’m highlighting this because I found a great new word in this Dec. 16, 2011 news item on Nanowerk,

Whether it’s right under our nose or far away, when we observe an object we see it—provided we have healthy eyes and normal vision or suitable glasses—in focus. For this to work, muscles deform the lenses of our eyes and adjust them to a suitable focal distance. For miniaturized technical devices, microscale lenses with a similar adaptable focus could be an advantage.

In this case scientist Hong Bo Bun and a team from Jilin University (China) have devised a new technique for creating microlenses. From the news item (here’s the new word),

The Chinese researchers have now met this challenge: They used a laser to “write” the desired micrometer-sized lens shape out of a solution of bovine serum albumin, a protein. Methylene blue acts as a photosensitizer, which captures the light energy like an antenna and triggers a crosslinking reaction of the protein molecules. Driven by a computer, the laser cuts out the desired three-dimensional form voxel by voxel. A voxel is a three-dimensional pixel, a tiny segment of volume. The irradiation used is in femtosecond pulses, which lasts on the order of 10-13 seconds. The crosslinking reaction only takes place in the locations that are irradiated. After the reaction, the protein molecules that have not reacted can simply be rinsed away. What stays behind is a cross-linked, aqueous protein gel in the shapes of micrometer-sized lenses.

You can get more details from the news item on Nanowerk or (provided you can get past the paywall) from the article in the journal Angewandte Chemie (“Dynamically Tunable Protein Microlenses”) .