A new type of artificial ligaments
Artificial ligaments based on nanotubes and collagen
A group of scientists has developed a new type of artificial joint ligaments. The implant is a seamless polyethylene terephthalate tube covered with a carbon nanotube frame and collagen. Experiments have shown that the patient's rehabilitation time has decreased by 7 weeks, and the probability of repeated surgery has decreased by 2.5 times compared to traditional synthetic implants. The study was conducted with the participation of representatives of Sechenov University with the support of the Russian Science Foundation. The results are published in the International Journal of Molecular Sciences.
"The advantage of our development is that the method of ligament implantation has not changed, which is very important for bringing the product to market. The cost of nanocoated implants will be two to three times less than the average cost of foreign analogues of uncoated ligaments. We use available domestic materials and equipment with a large resource: it is possible to make about a million more units of artificial ligaments," says Alexander Gerasimenko, head of the research project, Candidate of Physical and Mathematical Sciences, head of the Laboratory of Biomedical Nanotechnology at Sechenov University and NIU "MIET".
Stretching or tearing of ligaments is a frequent and very unpleasant injury in athletes and in general in people who lead an active lifestyle. One careless movement can lead, at best, to two weeks of sick leave and pain, and at worst, to surgery or disability. Rupture of the anterior cruciate ligament of the knee joint is one of the most frequent and unpleasant injuries, it accounts for more than half of the total number of joint injuries. To treat such an injury, it is necessary to implant donor or synthetic ligaments. However, in the first case, there is a possibility of rejection of someone else's tissue, and in the second, artificial materials may have low biocompatibility and take root poorly. In both situations, repeated surgery will be required, which increases the recovery time of the patient.
Scientists from Sechenov University, NIU "MIET", "RGAU-MSHA", "MONIKI" and NIU "SSU" managed to find a solution to this problem. The implant developed by them is a fiber made of polyethylene terephthalate (PET) thermoplastic with a coating based on a frame of single-walled carbon nanotubes formed by infrared radiation in a collagen matrix. Unlike other polymers, for example, polyester and polypropylene, PET is less likely to cause inflammation of the joint cavity. However, this material has low biological properties, therefore, in the area of implantation into the bone, a scar from connective tissue occurs, which interferes with the patient's recovery and increases the risk of repeated surgery. To correct this, scientists were looking for a material with improved biocompatibility, which is able to strengthen the mechanical properties of the connection between the implant and the bone. As a result of studying various biopolymer materials, such as body proteins, and their interaction with PET fibers, scientists came up with the idea of combining carbon nanotubes with collagen. Thus, the skeleton of nanotubes in collagen provided the implant with a unique structure due to the strong bond between carbon atoms, and also improved the restoration and germination of bone tissue. In turn, the biocompatibility of PET ligaments was achieved, and as a result of bone healing, the amount of connective tissue around the implant was reduced.
The developed technology was tested on rabbits implanted with artificial PET ligaments coated with carbon nanotubes with collagen. Six-month tests have shown excellent survival of the implant. Thanks to the frame structure of carbon nanotubes in the collagen matrix, the femur overgrown smoothly and quickly and fixed the ligament implant, as evidenced by the images from the tomograph. Histological studies conducted three and six months after implantation showed the absence of inflammatory processes and the formation of new bone tissue.
It was also revealed that during biodegradation, pores with a diameter of 0.5 to 6 microns appear in the implant structure. Over time, the number of pores and their size increased to 20 microns. Through them, blood vessels and nerve endings grow inside the implant, which accelerates the patient's recovery.
In addition, PET fibers with nanotubes and collagen have better hemocompatibility. Scientists have found that the level of destruction of red blood cells in the developed implant has been reduced to 0.8%, when, as with conventional PET fibers, this indicator is 1.45%. This feature makes it possible to use a new technology to create cardiovascular implants that are constantly in contact with blood.
The researchers suggest that the technology they have developed will reduce the rehabilitation time of patients by an average of seven weeks. In addition, scientists expect that the rejection of the implant in the short term will decrease by 2.5 times compared to existing samples. The authors will also continue working on the nanocoating: it is necessary to make it last longer on the surface of the fibers. Then the cells will attach more efficiently to the implant, and as a result it will take root better. After that, it will be possible to conduct preclinical studies and register the development as a medical device.
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