Weizmann Institute scientists have created innovative materials inspired by the lubrication model of our joints. The result may be real news for the biomedical industry
"...and he came like water in his heart and like oil in his bones" (Psalms 99:18)
They face heavy pressures, are in constant friction with the environment - but hardly wear out even for many decades. Our joints are an elaborate creation like no other that has been shaped over millions of years of evolution. The cartilage tissue that lines the ends of the bones in the joint is one of the significant components of this wonderful system. In a new study, Weizmann Institute of Science scientists have created Water-based gels inspired by cartilage tissue With coefficients of friction and erosion that are dozens of times lower than normal gels. Their findings may be used in the biomedical industry, for example for the purpose of inserting medical devices into the body and even in tissue engineering.
No man-made substance can match the lubrication of our joints. Damage to this pin will lead to increased friction and wear of the joint, as happens for example in degenerative arthritis (osteoarthritis). However, the origin of this unique pin is not well understood. According to a model developed in the last two decades in the laboratory of Prof. Jacob Klein From the Department of Molecular Chemistry and Materials Science, a central component of the lubrication system in the joints is lipids - fatty molecules that are the building blocks of cell membranes and other membranes in our body; These molecules consist of "water-hating" (hydrophobic) tails, attached to a "water-loving" (hydrophilic) head group. According to the model, in the uppermost layer of the cartilage tissue - the one that rubs against the cartilage tissue of the opposite bone - there are exposed lipid heads that form a unique coat of water molecules around them called a "hydration coat". Due to chemical and electrical properties, this sheath adheres firmly to the surface of the cartilage and is therefore resistant to pressure, but at the same time remains quite fluid, therefore allowing the surfaces of the cartilage in our joints to slide over each other - over and over again, every day, for years.
In a new study published recently, Prof. Klein together with Dr. Ronit Goldberg, a former doctoral student and senior intern in his laboratory, and in collaboration with research colleague Dr. Weifeng Lin, postdoctoral researcher Dr. Monika Kluzak, and senior faculty scientists Dr. Nir Kempf and Dr. Eyal Shimoni, innovative materials inspired by the lubrication model of cartilage: water-based gels containing Microreservoirs of lipids that are released to the surface of the gel during friction. "In cartilage, as in any biological system, the units that produce the various substances are cells. In the synthetic gels we created, instead of living cells, there are microreservoirs of lipid assemblies (liposomes) scattered throughout the bulk of the gel," explains Prof. Klein. "Thus, when the gel is eroded - and this is the erosion of individual microns - new reservoirs are exposed of lubricants. In other words, the surface of the gel is continuously renewed."
The performance of the new gels was extraordinary: the scientists saw up to a 100-fold reduction in friction and wear coefficients compared to conventional water-based gels. Furthermore, the low coefficient of friction remains almost the same even at different friction speeds and in contact with different types of materials, such as metal and glass. The excellent lubrication phenomenon is maintained even after the gels have been completely dried and rewetted, a feature that gives the devices based on these gels possibilities for use in the field and a long shelf life.
From the laboratory to the clinic
Water-based gels are adapted for contact with the soft tissues of the body - which also consist of considerable amounts of water - and are therefore widely used in the biomedical industry. Therefore, the new gels with the ability to self-lubricate may be real news for this industry, for example for inserting catheters and supports (stents) into the body as well as in tissue engineering. In the future, this model may also help in the development of artificial joints with high wear resistance, which will help those suffering from osteoarthritis or other diseases that damage cartilage. To promote these and other applications, in 2019 the start-up company "Liposphere" was established (Liposphere) in a license agreement with "Yida", an arm of the commercialization of the intellectual property of the institute's scientists. The founders of Liposphere are Dr. Goldberg (CEO of the company) and Dr. Sabrina Jahn, both former members of Prof. Klein's group and partners in other researches in his laboratory. The scientific journal Nature and the drugs and chemicals group Merck Choose Liposphere as one of the most promising start-up companies in 2020 that came out from within the walls of academic research institutions.
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