Polymer science began its development and emerged as an independent field of knowledge in the mid-1950s. In Greek, polymer means "many parts". In other words, it is a substance in which several links-monomers are combined into one macromolecule. The nature of this material can be diverse, so its application will also be diverse.
Two large groups of polymeric materials can be distinguished: synthetic and natural. Synthetic polymers are produced by chemical reactions. There are two main mechanisms for obtaining polymers: the polycondensation reaction and the polypropylene addition reaction. Natural polymers are synthesized independently by the method of biosynthesis in cells of living organisms and then by extraction, fractionation or other methods of separation from plant or animal raw materials.
The beginning of using polymers in medicine can be considered the end of the XVIII century, when rubber was first used in surgery as a biomedical material. One hundred years later, for the first time, celluloid is used to close bone defects in surgical operations on cranial boxes. Then, by joint efforts of dentists, surgeons, chemists and biologists a wide range of polymeric materials on the basis of acrylic resins is created, which are widely used in the manufacture of prosthetic products: dental, eye and maxillofacial.
Today in medicine there are more than 3000 names of medical devices including biopolymers. Let's stop on the most known. For example, polypropylene is a synthetic polymer, which we often meet in the home. In medicine, it is widely used for cardiovascular surgery, primarily for heart valves, blood vessels, as well as suture material and threads. The second polymer is polyvinylchloride, which is used in traumatology, surgery and gynecology. It is used in defects that require high wear resistance and low speed of resorption, that is, the ability to dissolve in the body. Nowadays medicine and medical technologies are aimed not only at replacing bone tissue defects, but also at restoring the defect and functions of the organism, that is why absorbable materials are used, i.e. materials that gradually dissolve in the organism's environment, allowing natural bone or other human tissues to germinate.
Absorbable materials are used in tissue engineering. We have metal constructions, materials based on titanium and its alloys, as well as ceramic materials - calcium phosphates, zirconium ceramics. All such materials have a number of drawbacks. In particular, it is possible to allocate excessive rigidity or fragility. Polymeric materials, of course, occupy a niche in this area and allow you to level out some negative aspects of the use of metal materials. Pure polymers are little used to replace bone defects. But a few years ago, an implant of spongy bone tissue based on polyethylene was created, which passed preclinical tests and is now quite successfully, judging by publications, undergoing clinical trials. However, this approach is not very much in demand by scientists, because the main direction is the reconstruction of natural bone tissue.
As you know, bone tissue is an organic and inorganic component. Therefore, composite materials on the basis of polymeric component - it can be both synthetic and natural - and inorganic component are promising for replacement of bone tissue defects. Ceramic fillers are most often used for this purpose - in particular, calcium phosphates, tricalcium phosphate, hydroxyapatite, octocalcium phosphate, because their phase composition is close to the inorganic composition of natural human bone tissue.
Composite materials are not only used to create scaffolds based on polymer and ceramic filler. One of the active applications of these materials is hydrogels. They can be used for direct filling of defects without surgical intervention and cavity operation. That is, it is a hydrogel that is pumped into the syringe and injected through the needle into the bone defect under ultrasonic control. Accordingly, the surgeon does not perform abdominal surgery. The patient's workload is much less and recovery is much faster. In this case, the material, entering the body, hardens under the influence of chemical reactions.
The second direction of hydrogels is ink for three-dimensional printing. In today's world, additive technologies such as 3D printing and electrospinning are developing rapidly. Hydrogels are one of the most optimal and suitable materials for printing. In materials science, especially in biomedicine, more often composite hydrogels with additional fillers are printed. Three-dimensional printing allows you to create a three-dimensional design that is fully consistent with the patient's defects, that is, personalized by computed tomography. In bone t