Like the Real Thing: Why Should Implants Pose as Living Tissues?

© Photo : Tomsk Polytechnic UniversityComposite implants made by 3D printing
Composite implants made by 3D printing - Sputnik International
The human body sees any alien object as an intruder and rejects it. This is a distinguishing feature of our immunity system that shields us from many health problems. But rehabilitation medicine considers the tissue-rejection response a serious problem because implants have the potential to be rejected.

Scientists from the Engineering School of Nuclear Technologies at National Research Tomsk Polytechnic University have developed a number of solutions for enhancing biocompatibility in oncology, cardiology, orthopedics and traumatology.

A Special Surface

Today, most implants are made of single-phase materials that fail to replicate all essential functions of the tissues and organs that are being replaced or restored. So, modern rehabilitation medicine is focusing on the development of multi-phase bio-materials that imitate living tissue.

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This technology uses multi-component hybridized materials, including composite materials with modified surfaces that have special water-repellent and water-receptive properties.

Tomsk Polytechnic University scientists have been developing materials like this for over ten years. For example, they have invented unique equipment for coating implants with bioactive surfaces, new spokes for Ilizarov frames that nearly cut the bone-tissue restoration time in half, as well as matrixes ("bio-reactors") for growing various organs and a coronary stent (special frame) coated with nano-particles that ‘destroy" atherosclerotic plaques to prevent cardiac arrests or strokes.

Hybrid materials can include surfaces with preset properties that are used in implantology and other areas. When placed inside a blood vessel, a coronary stent coated with composition nano-materials can destroy atherosclerotic plaques; and matrixes/bio-reactors coated with calcium phosphate can grow osseous tissue from cells. In the future, it may become possible to grow entire organs.

To create implants with enhanced bio-compatibility, scientists are developing new materials and modifying other materials by creating more dynamic surfaces and structures with ion-plasma and radiation techniques.

The surface of implants can offer antiseptic and, if necessary, anti-tumor properties, as well as enhanced osseous integration or a functional bond between an implant and osseous tissue. This helps prevent the rejection of implants, toxic chemical reactions and the expansion of pathogenic tissue.

Implants can be rejected when their immunological compatibility with the body is disrupted; this causes secondary infectious contamination. To prevent this, including the financial implications caused by less compatible materials, the university's researchers and doctors have developed a method for analyzing the body's immune system's response to implant materials.

"A study of the immune system's response analyzes the reaction of scavenger cells, which act as the immune system's agents in the bloodstream, to an implant material. This evaluation needs to be conducted during the selection of bio-compatible materials," Sergei Tverdokhlebov, an Assistant Professor with the university's Weinberg Science and Education Center, told RIA Novosti.

Titanium Bones Coated With Calcium Phosphate

Coatings based on calcium phosphate and other compounds were used in the development of titanium implants that closely resemble human bones. This helps reduce the rejection rate and accelerate the regeneration process.

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According to Tverdokhlebov, the current equipment for machining the surfaces of implants does not completely meet the needs of this development. The university's researchers are therefore developing new-generation systems to efficiently coat implants with bio-active substances using the micro-arc oxidizing method.

Researchers are also working to develop bio-resorption implants to substitute bone defects. They have already created hybrid bone implants for reconstructive facial-and-skull surgery with biodegradable polymers and 3D printers.

The implants mostly consist of metal net-rods and polymers that dissolve completely inside the body. The implants can be used for complicated operations on patients with skull and face-bone injuries, as well as cancer cases.

Specialists want to mass-produce medical items for restoring the functions of the human locomotor system, including hip joints and implants for spinal surgery.

Preventing Cardiac Arrest and Stroke

Atherosclerosis is the most widespread chronic disease affecting the arteries. Connective tissue that expands in an artery reduces its cross-section, with the cardiac muscle receiving less blood as a result.

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Charles Theodore Dotter, the father of a new medical specialty, interventional radiology, suggested a concept for expanding a blood vessel's affected sections with a frame/stent. The first stent-insertion surgery was performed in 1986. A stent is a thin metal tube consisting of wire sections; it is placed inside the affected artery to increase the cross-section.

Scientists at Tomsk Polytechnic University and their colleagues from the Cardiology Institute of the Tomsk Research & Development Medical Center have synthesized a composite nano-material for coating coronary stents. This material can destroy atherosclerotic plaque, the main cause of cardiac arrest and stroke.

Today, doctors often use medication-coated stents, but medications can produce side effects, Tomsk Polytechnic University staffer Marina Trusova, DSc (Chemistry), noted.

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"The plaque increases over five or six years, and we have to replace the stent. Our stent will ‘break up' the plaque, thus avoiding another operation," she told RIA Novosti.

he invention has been patented in the United States and Eurasia. A prototype coronary stent has been analyzed for toxicity levels during pre-clinical tests; and clinical trials are to commence before 2020.

Spokes for Fast Rehabilitation

The university's researchers teamed up with specialists from the Ilizarov Center in Kurgan and developed intra-osseous titanium and steel spoke-shaped implants with bio-active coatings to basically cut patient recovery times in half during post-traumatic limb break recovery.

The steel spokes are coated with the bio-active coating, a composite material based on piezo-electric carbon-fluoride plastics and hydroxyapatite using aerodynamic-formation or magnetron-coating methods. The micro-arc oxidizing method is used to coat the titanium implants with calcium phosphate.

"Tests indicate that it took 35 days to restore bone tissue using the new four-centimeter implants, as compared to 70 days for standard implants. Moreover, the new bone tissue was 150 percent denser and much closer to healthy bone-density levels, as compared to standard implants," Tverdokhlebov noted.

According to the researchers, this technology speeds up reparative osteogenesis, resulting in quicker positive treatment results. In this respect, Russia continues to lead the way in global orthopedics and traumatology.

Tissues From a Test-Tube

Scientists suggest matrixes that would function as bio-reactors for rehabilitation medicine are possible; they could also possibly help grow human body tissue. Stem cells capable of forming tissue, including connective, bone, skin or heart tissue, would be placed inside the porous structure.

"We create a matrix using an electrospinning method; they are formed from ultra-thin fibers under the influence of an electrical field," Yevgeny Bolbasov, a research associate with the Laboratory of Hybrid Plasma Systems at the university's Engineering School of Nuclear Technologies, told RIA Novosti.

Growth factors, including an extremely thin calcium-phosphate surface, are used to accelerate the formation of bone tissue.

"A cell applied to a calcium-phosphorus surface will start penetrating the bone tissue. If we place a cell inside a Petri dish, it will remain neglected, but it will receive a good home and enough food inside this matrix," Tverdokhlebov explained.

The Ministry of Science and Higher Education of the Russian Federation, the Russian Science Foundation, and the Russian Foundation for Fundamental Research finance these research projects under the Federal Targeted Program High-Priority Research & Development Projects in Russia's Science and Technological Sector in 2014-2020.
The university's innovations are already undergoing pre-clinical and clinical tests. Scientists want to create an implant that can take readings of a patient's condition, analyze the body's demand for various substances and deliver these substances to predetermined locations.

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