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26.10.2020PET implants with carbon nanotubes accelerate ligament healing
Treatment of ligament injury can take a long time because of the use of imperfect materials. Sechenov scientists designed artificial polyethylene terephthalate ligaments coated with carbon nanotubes in a collagen matrix. These implants can reduce the recovery time and have a lower rate of rejection by the immune system.
Ligament sprains and ruptures are quite common and immensely unpleasant injuries, in particular for athletes but also everyone who tends to maintain a high level of physical activity. The injury can be treated with surgery, while an extended recovery period is often needed to manage the consequences. Donor or synthetic ligaments can be implanted as part of the treatment, but the donor tissue may be rejected by the immune system, whereas artificial materials may have low biocompatibility. To circumvent this, scientists from Sechenov University and their colleagues from several other research organisations have designed and tested implants made of polyethylene terephthalate (PET) coated with a frame structure of single-walled carbon nanotubes (SWCNT) in a collagen matrix. The results have been published in the International Journal of Molecular Sciences.
The PET fibres used in the work were coated with a frame structure of SWCNT formed by infrared radiation in a collagen matrix. Unlike other commonly used polymers such as polyester and polypropylene, PET is less likely to cause joint inflammation. However, the material may lead to the scarring of the connective tissue in the area where the implant is in contact with the bone. This complication interferes with the recovery and increases the risk of a second surgery.
The collagen-based SWCNT structure was proved to have good biocompatibility, and it could reduce the amount of the connective tissue around the PET ligament. In addition, the PET fibres with carbon nanotubes and collagen have a better hemocompatibility. The experiments showed that the haemolysis (rupturing of erythrocytes) was reduced to 0.8%, while for conventional implants it is about 1.45%.
The artificial ligaments were tested in rabbits for 6 months. The femurs with the implants recovered evenly and quickly, as seen by tomography. Histology images made after 3 and 6 months post-implantation showed no signs of inflammation.
Pores with a diameter of 0.5–6 µm appeared in the implants over time, ultimately reaching 20 µm. This helped the blood vessels and nerve endings grow inside the ligaments, thus accelerating the recovery.
‘The advantage of the proposed implant structure is that the implantation method does not change, and it is important for rapid and successful implementation of the technology’, said Alexander Gerasimenko, Head of the Laboratory of Biomedical Nanotechnologies at Sechenov University and the first author of the paper. ‘Also, the cost of these nanocoated implants is 2–3 times lower than the cost of uncoated ligaments produced abroad. We use Russian-made materials and equipment and can scale up the manufacturing of our artificial ligaments to a million units’.
The researchers suggest that the new technology may reduce the rehabilitation time of the patients and the rate of immune rejection. The authors also hope to test their SWCNT-coated polyethylene terephthalate as cardiovascular implants — thanks to the good hemocompatibility required for the surfaces contacting with blood.
The study, supported by the Russian Science Foundation, was carried out by the Institute for Bionic Technologies and Engineering (Sechenov University) and several collaborators.
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PET implants with carbon nanotubes accelerate ligament healing
Treatment of ligament injury can take a long time because of the use of imperfect materials. Sechenov scientists designed artificial polyethylene terephthalate ligaments coated with carbon nanotubes in a collagen matrix. These implants can reduce the recovery time and have a lower rate of rejection by the immune system.
Ligament sprains and ruptures are quite common and immensely unpleasant injuries, in particular for athletes but also everyone who tends to maintain a high level of physical activity. The injury can be treated with surgery, while an extended recovery period is often needed to manage the consequences. Donor or synthetic ligaments can be implanted as part of the treatment, but the donor tissue may be rejected by the immune system, whereas artificial materials may have low biocompatibility. To circumvent this, scientists from Sechenov University and their colleagues from several other research organisations have designed and tested implants made of polyethylene terephthalate (PET) coated with a frame structure of single-walled carbon nanotubes (SWCNT) in a collagen matrix. The results have been published in the International Journal of Molecular Sciences.
The PET fibres used in the work were coated with a frame structure of SWCNT formed by infrared radiation in a collagen matrix. Unlike other commonly used polymers such as polyester and polypropylene, PET is less likely to cause joint inflammation. However, the material may lead to the scarring of the connective tissue in the area where the implant is in contact with the bone. This complication interferes with the recovery and increases the risk of a second surgery.
The collagen-based SWCNT structure was proved to have good biocompatibility, and it could reduce the amount of the connective tissue around the PET ligament. In addition, the PET fibres with carbon nanotubes and collagen have a better hemocompatibility. The experiments showed that the haemolysis (rupturing of erythrocytes) was reduced to 0.8%, while for conventional implants it is about 1.45%.
The artificial ligaments were tested in rabbits for 6 months. The femurs with the implants recovered evenly and quickly, as seen by tomography. Histology images made after 3 and 6 months post-implantation showed no signs of inflammation.
Pores with a diameter of 0.5–6 µm appeared in the implants over time, ultimately reaching 20 µm. This helped the blood vessels and nerve endings grow inside the ligaments, thus accelerating the recovery.
‘The advantage of the proposed implant structure is that the implantation method does not change, and it is important for rapid and successful implementation of the technology’, said Alexander Gerasimenko, Head of the Laboratory of Biomedical Nanotechnologies at Sechenov University and the first author of the paper. ‘Also, the cost of these nanocoated implants is 2–3 times lower than the cost of uncoated ligaments produced abroad. We use Russian-made materials and equipment and can scale up the manufacturing of our artificial ligaments to a million units’.
The researchers suggest that the new technology may reduce the rehabilitation time of the patients and the rate of immune rejection. The authors also hope to test their SWCNT-coated polyethylene terephthalate as cardiovascular implants — thanks to the good hemocompatibility required for the surfaces contacting with blood.
The study, supported by the Russian Science Foundation, was carried out by the Institute for Bionic Technologies and Engineering (Sechenov University) and several collaborators.