Old bones will still serve
Scientists have developed a method for manufacturing implants based on natural bone
NUST MISIS Company blog, Habr
The installation of such a foreign body as an implant is a great stress for the body, and that is why scientists pay great attention to ensuring rapid survival and the longest possible service life of the product. Success depends both on the properties of the source material itself and on the structural features of the implant, production methods, etc. Metal, ceramics, various polymers, as well as their combinations can be used. Ideally, the less the body "feels" the foreignness of the implant, the faster it takes root, the freer the patient's cells feel, the lower the risk of rejection. Guided by these principles, scientists at NUST MISIS, together with colleagues from the N.N. Blokhin NMIC and the Technical University of Dortmund, have developed a unique technology for manufacturing polymer implants, where the real bone serves as a "negative" for casting the product.
One of the most popular materials for the production of bone implants is ultrahigh molecular weight polyethylene (UHMWPE). NUST MISIS scientists have been developing biomimetic (repeating the real bone structure of implants) scaffolds (structures that become implants after implantation) based on it for several years. Special attention is paid to imitating the porosity of the bone core so that after the implant is installed, the patient's bone cells can divide and "germinate" into the implant. Previously, the team achieved such an architecture of samples by 3D modeling and printing the "negative" of the bone, followed by filling the mold with polymer.
A new development of scientists is a biomimetic scaffold from UHMWPE, the structure of which is copied from the structure of a real mammalian bone. Initially, experiments were carried out with fragments of cow bones. The bone marrow was removed using hydrogen peroxide, then the bone was filled with polyestersulfone – to form a "negative" internal structure. Then the resulting "negative" was washed with hydrochloric acid, filled with UHMWPE powder, and thermal compression took place. Finally, the sample was immersed in N-methylpyrrolidone, which completely dissolved the polyestersulfone "negative", leaving only a porous UHMWPE with a structure imitating the original bone structure.
"A characteristic feature of the spongy part of the bone is anisotropy – pores elongated along the length of the bone, elliptical in section. It is impossible to completely repeat this on a 3D printer due to the high viscosity of the UHMWPE melt,“ says Inna Bulygina, an employee of the NUST MISIS Center for Composite Materials and the main author of the development. – When we used as a “negative” bone with the lengths of the major and minor axes of the pores ~ 770 microns and 470 microns, respectively, we got polymer pores with axis lengths ~ 700 microns and 500 microns. That is, the shape of the pores turned out to be elliptical on the slice, as close as possible to the natural one."
Scientists from the Technical University of Dortmund evaluated the topography of the sample, and thanks to specialists from the N.N. Blokhin NMIC, in vitro tests were carried out.
The experiments on incubation of the implant with multipotent mesenchymal stromal cells proved their 75% proliferation after 48 hours. Next, the scientists plan to test various combinations of materials for the manufacture of implants with a spongy core and a hard shell. According to the researchers, the most promising niche for the potential implementation of the development is veterinary medicine.
The technology has already been patented, an article about the development has been published in the journal Polymer Degradation and Stability.
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