As a biomedical material, bioceramics have no toxic side effects, good compatibility with biological tissues and corrosion resistance, and have been widely used in the clinical manufacture of artificial bones, bone nails, dentures, dental implants and intramedullary nails. At present, the research of bioceramic materials has developed from short-term substitution and filling to permanent and firm planting, from biologically inert materials to biologically active materials. However, due to the influence of pores and defects in conventional ceramic materials, the low-temperature performance of this material is poor, the elastic modulus is much higher than that of human bones, the mechanical properties are mismatched, it is easy to break, and the strength and toughness can not meet the clinical requirements, which greatly limits its application.
The appearance of nano-materials makes it possible to greatly improve the biological and mechanical properties of bioceramics. Compared with conventional ceramic materials, the size of pores or defects in nano-ceramics is greatly reduced, and the material is not easy to cause transgranular fracture, which is beneficial to improve the fracture toughness of solid materials. However, grain refinement greatly increases the number of grain boundaries, which contributes to the slip between grain boundaries and makes nano-ceramic materials show unique superplasticity. Some materials scientists point out that nano-ceramics is a strategic way to solve the brittleness of ceramics. At the same time, the inherent surface effect of nano-materials makes its surface atoms have many hanging bonds, which are unsaturated and have high chemical activity. This characteristic can increase the biological activity and osteogenic induction ability of the material, and realize the purpose of early fixation of the implanted material in vivo.
American scientists studied the differences between nano-solid alumina and nano-solid apatite materials and conventional alumina and apatite solid materials in in vitro simulation experiments. The results show that nano-solid materials have stronger cell adsorption and reproduction ability. They suspect that this may be due to the following reasons.
(1) nano-solid materials are easier to degrade in simulated environment.
(2) The decrease of grain size and pore size changed the surface roughness of the material and enhanced the function of osteoblast-like cells.
(3) The surface of nano-solid materials is more hydrophilic, and cells are more easily adsorbed on it.
In addition, people also use the characteristics of small nanoparticles, large specific surface area and high diffusivity to add nano-ceramic powder to some proposed bioceramic materials to improve their density and toughness, and use them as bone substitute materials, such as nano-alumina toughened alumina ceramics and nano-zirconia toughened zirconia ceramics. , and made some progress.
Scientists from Sichuan University, China, made nano-bone-like apatite crystals and polyamide polymers into composites, and adjusted the content of nano-crystals to the same proportion as that of human bones, and successfully developed nano-artificial bones. This nano-artificial bone is a kind of high strength and flexible composite bionic bioactive material. Because this composite material has excellent biocompatibility, mechanical compatibility and biological activity, nano-artificial bone made from it can not only form biological combination with natural bone, but also grow firmly with human muscles and blood vessels. It can also induce the formation of cartilage, and its various characteristics are almost equivalent to those of human bones. In addition, they also imagine that nano-solid ceramic materials will be made into the shell of artificial eyeball, so that this artificial eyeball can not only move synchronously like a real eye, but also stimulate the cranial nerves through electrical pulses and see a wonderful world; The ideal nano-bioceramic eyeball can blend well with the orbital muscle tissue and move synchronously.
Among inorganic non-metallic materials, magnetic nano-materials are the most concerned and have become the research focus in the field of emerging biomaterials. In particular, magnetic nanoparticles show good surface effect, the specific surface area increases sharply, the functional group density and selective adsorption capacity increase, and the percentage of drugs or genes carried increases. In physical and biological sense, paramagnetic or superparamagnetic ferrite nanoparticles can kill tumors by heating to 40 ~ 45℃ under the action of external magnetic field.
German scholars reported the synthesis and physical and chemical properties of superparamagnetic polysaccharide nanoparticles (200 ~ 400 nm) with iron oxide content of 75% ~ 80%. It interacts with nano-silica to improve the strength of particle matrix, and the application of nano-magnetic particles in molecular biology is studied. Glucose and silica reinforced nanoparticles with specific specific surface areas were tested. Compared with the artificial magnetic beads available in industry, it includes DNA automatic purification, protein detection, separation and purification, retrovirus detection in biological materials, endotoxin removal and magnetic cell separation. For example, in the automatic purification of DNA, the nonspecific DNA binding ability of DNA type 1-2KD was realized by using dextran nanoparticles with a concentration of 25mg/mL and nanoparticle suspension reinforced by SiO2 _ 2. The application of silica reinforced dextran nanoparticles greatly weakened the background signal. In addition, magnetic nanoparticles can be coated with polymer materials, combined with protein, and injected into human body as drug carriers. Under the external magnetic field of 2 125× 103/π(A/m), the magnetic orientation of magnetic nanoparticles can make them move to the focus, thus achieving the purpose of targeted treatment: 4 cases of Fe3O4, 10 ~ 50n. This local treatment has good effect and few side effects. Promising nanotechnology.
In addition, according to the fact that TiO _ 2 nanoparticles have high redox ability and can decompose microbial protein under illumination, scientists further apply TiO _ 2 nanoparticles to the treatment of cancer cells. The results show that TiO _ 2 nanoparticles can kill all cancer cells after 65438 00 minutes of ultraviolet irradiation.
There are some examples of other applications.
In the early 1980s, people began to use nano-particles to separate cells, and established a new technology of using nano-silica particles to separate cells. The basic principle and process are as follows: First, prepare silica nanoparticles with the size controlled at 15 ~ 20 nm. The structure is generally amorphous, and then its surface is covered by a single layer. The choice of coating mainly depends on the kind of cells to be separated, and usually the substance with affinity to the cells to be separated is selected as the attachment layer. The size of the composite formed by coating silica nanoparticles is about 30 nanometers; . Step two, preparing polyvinylpyrrolidone colloidal solution containing various cells, and appropriately controlling the concentration of the colloidal solution; The third step is to evenly disperse nano-silica coated particles into polyvinylpyrrolidone colloidal solution containing various cells, and then quickly separate the required cells by centrifugation technology and density gradient principle. The advantages of this method are: ① it is easy to form density gradient; ② Nano-silica particles can be easily separated from cells. This is because nano-silica particles belong to the category of inorganic glass and have stable properties. Generally, it does not react with colloidal solution and biological solution, neither polluting biological cells nor easily separating.
Based on the significant differences in sensitivity and affinity of different antibodies to various organs and bone tissues in cells, antibody types were selected, and gold nanoparticles were mixed with pre-refined antibodies or monoclonal antibodies to prepare various gold nanoparticles-antibody complexes. With the help of composite particles combined with various organs and skeletal systems in cells, the composite presents a certain characteristic color under white light or monochromatic light irradiation (for example, gold particles of 10nm are red under optical microscope), thus "marking" various combinations with different colors, thus providing an urgently needed dyeing technique for improving the resolution of intracellular tissues.
After biomaterials are applied to human body, the surrounding tissues are in danger of associated infection, which will lead to the failure of materials and surgery and bring great pain to patients. Therefore, people have developed some nano-biomaterials with antibacterial properties. For example, in the reaction of synthesizing hydroxyapatite nano-powder, the aqueous solution of soluble salts such as silver and copper is added to the reactant, so that antibacterial metal ions enter the apatite crystal product, and antibacterial apatite micro-powder is prepared, which is used for filling bone defects and so on.
At present, many nano-materials with bactericidal or antiviral functions have been found. Titanium dioxide is a kind of photocatalyst. Ordinary TiO2 _ 2 has catalytic effect only under ultraviolet irradiation, but when its particle size reaches several tens of nanometers, it has strong catalytic effect as long as it is irradiated by visible light. Studies have shown that free radical ions will be produced on its surface to destroy protein in bacteria, thus killing bacteria and degrading toxic compounds released by bacteria. In practical application, nano-TiO2 _ 2 can be added to the whole or part of the product, and then it is immobilized with another substance, which will slowly release free radical ions at a certain temperature, so that the product has bactericidal or antibacterial functions. For example, when the towel treated with TiO2 is irradiated with visible light, the bacteria on the towel will be killed by the free radical ions released by nano-TiO2. TiO2 _ 2 photocatalyst is suitable for direct placement in hospital wards, operating rooms, living spaces and other places with dense bacteria.
After the development in recent years, the research of nano bioceramic materials has made gratifying achievements, but overall, this field is still in its infancy, and many basic theories and practical applications need further study. For example, the preparation technology of nano-bioceramics-how to reduce the cost and make it a civilian medical material; Development and utilization of new nano-bioceramic materials: how to make functional nano-bioceramic materials move from prospect to reality and from laboratory to clinic as soon as possible; Vigorously promote the development of molecular nanotechnology and realize the construction of instruments and devices at the molecular level to maintain human health at an early date. This requires the full cooperation and joint efforts of material workers and medical workers.