Gang Jin Peiqing Ying
Institute of Mechanics, Chinese Academy of Sciences
(November 2000-February 2001)
From Chinese Academy of Sciences Nano Science and Technology Network
What does nano-bioengineering mean? What exactly does it include? Generally speaking it includes nanomedicine, nanobiotechnology and nanobiomaterials. In fact, medicine, biotechnology and biomaterials are all familiar terms and elements that seem to be in suspense when wearing a nano hat. Here we will first review the substances and things related to the terms we are familiar with, and then link these with the nano concept to see what new changes have been made, and understand nano-bioengineering by observing some relevant scientific research results and application examples.
I. Nanomedicine
Most people have the experience of being sick, taking medicine and injections, and medicine is the science of studying diseases and curing them. So what is nanomedicine? We know that the human body is composed of a variety of organs, such as: brain, heart, liver, spleen, stomach, intestines, lungs, bones, muscles and skin; organs are composed of a variety of cells, the cell is the organization of the organ unit, the combination of the role of the cell to show the function of the organ. So what are cells made of? According to the current understanding, the main components of the cell is a variety of proteins, nucleic acids, lipids and other biomolecules, can be collectively referred to as biomolecules, which are in the hundreds of thousands of species. Biomolecules are the basic components of the human body, each of them has a unique biological activity, it is their different biological activity determines their division of labor and role in the human body. Since the human body is composed of molecules, all diseases, including aging itself, can be attributed to changes in the molecules in the human body. When the body's molecular machinery, such as ribosomes, which synthesize proteins, and enzymes, which are required for DNA replication, malfunction or work out of order, it can lead to cell death or abnormalities. From the microscopic point of view of molecules, current medical technology is not yet able to reach the level of molecular repair. Nanomedicine, on the other hand, is the science and technology of diagnosis, medical treatment, prevention of disease, prevention of trauma, pain relief, health care and improvement of health, etc. at the molecular level, utilizing molecular tools and the molecular knowledge of the human body, which, broadly speaking, all belong to the scope of nanomedicine. In other words, people will know themselves at the molecular level, create and utilize nano-devices and nanostructures to prevent and treat diseases, and improve the whole life system of human beings. It is first necessary to understand the molecular basis of life, and then to develop from scientific understanding to engineering technology, designing and manufacturing a large number of nanodevices with incredibly strange effects. These tiny nanodevices, with a geometrical scale of only about one-thousandth of a hair's thread, are assembled one molecule at a time, and are able to perform functions similar to those of tissues and organs, and to do so more accurately and more effectively. They can travel throughout the human body, even in and out of cells, accomplishing special missions in the body's microcosm. For example: repairing aberrant genes, killing newly sprouted cancer cells, capturing bacteria and viruses that invade the human body and eliminating them before they cause disease; detecting changes in chemical or biochemical components in the body, releasing medicines and trace substances needed by the human body at the right time, and promptly improving the health of human beings. Ultimately, nanomedicine will be realized so that human beings can have sustained health. The future of nanomedicine will be powerful, and it will be surprisingly small, because the drugs and medical devices that play a role in it are invisible to the naked eye. But its capabilities will amaze the world.
It should be noted that one should not immediately run to the doctor for a nano-prescription. The nanomedicine landscape discussed above is still in the design and nascent stages, and there are still many unknowns to be explored, such as: what should these nanodevices be made of? Will they be acceptable to the human body? And perform the intended role? Scientists are doing their best to turn the scientific idea of nanomedicine into a medical reality. One day, the smaller the medicine cabinet, the more effective it will be.
Some people must ask: Is nanomedicine science fiction? How far away is it from us? How much longer do we have to wait to see medicine realized? In fact, it is already beginning to step into reality and gaining momentum. Here's a look at the scientific advances that have been made in this field.
(1) Smart Drugs
This is a very active area of nanomedicine, and releasing drugs at the right time and with the right precision is one of its basic functions. Scientists are developing an ultra-small, glucose-detecting system for diabetics that mimics the glucose detection system in healthy people. It can be implanted under the skin to monitor blood glucose levels and release insulin when necessary, so that the patient's blood glucose and insulin levels are always in a normal state. More recently, researchers at the Massachusetts Institute of Technology in the United States have made the prototype of a micropharmacy: a microchip with thousands of small drug reservoirs, each of which could hold up to 25 nanoliters of any drug, such as painkillers or antibiotics. Robert Langer, one of its researchers, says that the chip, which is currently the size of a small coin, could be made even smaller, and plans to equip it with an "intelligent" sensor that would allow it to release just the right amount of drug at just the right time. Is it possible to kill cancer cells at an early stage before a deadly tumor forms? Dr. James R. Baker Jr. of the University of Michigan, USA, is designing a nano "smart bomb" that can recognize the chemical "signatures" of cancer cells. The "smart bomb" is small, only about 20 nanometers, and can enter and destroy individual cancer cells. Development of the device has just begun, and initial human trials are at least five years away.
(2) Artificial Red Blood Cells
Schematic of the structure and work of an artificial red blood cell
With the rotation of the rotor, the gas molecules combine with the binding sites on the rotor and then release them, entering the plasma from the diamond cavity
Nanomedicine not only has the function of eliminating the bad factors in the body, but also has the ability to enhance the function of the human body. As we know, brain cells are necrotic after 6 to 10 minutes of oxygen deprivation, and internal organs will show failure after oxygen deprivation. Imagine a kind of artificial red blood cells equipped with ultra-small nanopumps, the oxygen carrying capacity is more than 200 times of natural red blood cells. When a person's heart suddenly stops beating due to an accident, the doctor can immediately inject a large number of artificial red blood cells into the human body, and then provide the oxygen on which life depends, in order to maintain the normal physiological activities of the whole organism. The design of artificial red blood cells (respirocyte) initially proposed by American nanotechnology expert Robert Freitas has become a landmark result of nanotechnology. The blood cell is a one-micron-sized diamond oxygen container with an internal pressure of 1,000 atmospheres, pumped by serum glucose. It delivers 236 times more oxygen than an equivalent volume of natural red blood cells and maintains biochar activity. It can be used in applications such as topical treatment of anemia, artificial respiration, loss of lung function, and additional oxygen consumption required for sports. Its basic design and structural function, as well as its compatibility with living organisms, have been discussed in detail in monographs. Here we will only briefly introduce its structure and function. The figure shows the structure and working diagram of this artificial red blood cell.
It has a cavity shell of diamond which is compatible with living organisms, and oxygen is stored in the cavity, and at the opening is a rotor which can transfer oxygen from the cavity to the outside, and rotate with it to input oxygen molecules into the blood.
(3) Nano drug delivery
Nano-particle drug delivery technology is also one of the important development direction. According to the current understanding, more than half of the new drugs have problems of dissolution and absorption. Since the effective contact area between the drug and the gastrointestinal fluid will increase when the drug particles are reduced, the dissolution rate of the drug increases with the reduction of the drug particle scale. The absorption of the drug is in turn limited by its dissolution rate, so shrinking the particle scale of the drug becomes a feasible way to improve the utilization of the drug. Nanocrystal technology can convert drug particles into stable nanoparticles while improving solubility to increase the drug efficiency of difficult-to-solve drugs. The pulverization process causes an increase in the interaction force between the particles and to avoid aggregation of nanoparticles during the pulverization process, the insoluble drug is processed by being suspended in a suspension containing stabilizers and excipients that are generally considered safe. Intensively researched powdering techniques have been able to reduce the drug to less than 400 nanometers. Also, these excipients act as surfactants in the gastrointestinal tract and improve the dissolution rate of nanodrug particles. Once, insoluble drugs are converted into stable nanoparticles, they are suitable for oral administration or injection.
There is already growing recognition that nanomedicine will revolutionize medicine, the treatment of diseases such as cancer, diabetes and Alzheimer's disease. Using nanotechnology it is possible to deliver novel genetic material into already existing DNA without causing any immune response. Dendrimers are good candidates to provide such delivery. Because they are non-biological materials, they do not induce an immune response in the patient, and there is no risk of rejection; therefore, they can be used as nanocarriers for drugs, carrying the drug molecules into the human bloodstream, so that the drugs can exert their curative effects without immune rejection. This technology is promising for diabetes and cancer treatment.
(4) Nanotraps for capturing viruses
Donald Tomalia et al. at the University of Michigan have developed nanotraps capable of capturing viruses using tree polymers. In vitro experiments showed that the nanotraps were able to capture influenza viruses before they infected cells, and the same approach is expected to be used to capture more complex viruses such as the AIDS virus. The nanotraps use ultra-small molecules that bind to the virus before it can enter the cell and cause disease, rendering the virus incapable of causing disease.
In layman's terms, the surface of a human cell is equipped with a "lock" containing silica-aluminum acid, which allows only the person holding the "key" to enter. Unfortunately, viruses have silica-aluminate receptor "keys," and Tomalia's approach is to cover the surface of trap cells (glycodendrimers) with silica-aluminate sites that can bind to viruses. When the virus binds to the surface of the trap cells, it can no longer infect human cells. The trap cell consists of three parts: the outer shell, the inner lumen, and the nucleus. The inner cavity can be filled with drug molecules; in the future, it could potentially be loaded with chemotherapy drugs and delivered directly to the tumor. Trap cells are capable of reproducing, generating different offspring, with the larger offspring potentially carrying more drugs. Although the reason for this is unclear, the observed feature is that bigger is more effective. The researchers hope to develop specialized trap cells for various disease-causing viruses and a library of trap cells for medical use.
(5) Biochip to recognize blood abnormalities
The discovery at the U.S. San Diego National Laboratory fulfills the predictions of nano enthusiasts. Just as predicted, nanotechnology could cruise through the bloodstream, instantly detecting foreign invaders such as viral and bacterial types and wiping them out, thus eliminating infectious diseases. Micheal Wisz made a prototype device that functions as a lab-on-a-chip, which can flow along the bloodstream and track cells like those with sickle cell anemia and those infected with AIDS. The blood cells are channeled into the surface of a cavity that emits a laser, which changes the formation of the laser. Cancer cells produce a bright flash of light; healthy cells emit only a standard wavelength of light to identify cancerous lesions.
Two, nanobiotechnology
Nanobiotechnology is a product of the combination of nanotechnology and biotechnology, which can be used in biomedicine, but also can serve other social needs. It is very rich in content and is increasing and developing at such a fast rate that it is difficult to summarize. Here are just a few examples of research results.
(1) Biochip Technology
Biochips are another type of chip different from semiconductor electronic chips. Semiconductor electronic chip is integrated with a specific electronic function of the micro-unit, the formation of electronic integrated circuits; while the biochip is a very small geometric scale surface area, assembly of one or integrated multiple biological activity, only a trace amount of physiological or biological sampling, that is, you can simultaneously detect and study different biological cells, biological molecules, and DNA characteristics, as well as their interactions, and access to the life of the micro-activity laws. activity laws of life. Biochips can be roughly divided into cell chips, protein chips (biomolecule chips) and gene chips (i.e., DNA chips) and other categories, all of which have the advantages of integration, parallelism and rapid detection, and have become the cutting-edge science and technology of biomedical engineering in the twenty-first century.
In the past two years, has been through the micro-production (MEMS) technology, made of micron-scale manipulator, able to capture a single cell in cell solution, cell structure, function and communication and other characteristics of the study. Researchers led by Prof. Whitesides of Harvard University in the U.S. have developed the application of photolithography, which is commonly used in the microelectronics industry, in the field of biology, and have developed a soft lithography method with better results. As a result, biochips that can capture and immobilize individual cells have been produced, and cell secretion and intercellular communication can be studied by adjusting cell spacing. This type of cell chip can also be used for cell sorting and purification. The principle of its function is very simple, using only the geometry and surface modification of the microcells on the surface of the chip to select and immobilize cells, as well as to control the cell surface density.
Figure 2: Multi-Protein Microarray Model The figure shows in clockwise direction:
1) immobilization of ligands on a formatted modified surface;
2) interaction of the ligand-containing microarray with the protein solution, with protein-specific binding to form protein complexes;
3) assaying of the microarray to determine the protein-protein interactions.
The development of protein microarrays has gone through about ten years, and relatively mature technologies have emerged, such as the unit chip of BIACORE in Sweden, the multivariate protein optical microarray of the Institute of Mechanics of the Chinese Academy of Sciences, and SELDI mass spectrometry microarrays in the United States, etc. They all have the same characteristics. Their **** the same characteristics are biomolecules as ligands, fixed on the surface of the solid chip or surface micro-units to a single, or face array, or sequence type. Utilizing the natural property of specific binding between biomolecules, the molecule to be tested and the ligand molecule will form a biomolecular complex on the chip surface. The presence or absence of this complex is then detected for the purpose of protein detection, identification and purification. The difference between the above technologies is only in the detection method; BIACORE technology utilizes surface plasma*** vibration technology to detect the chip for single protein detection; Multiple Protein Optical Chip is an optical imaging method, which can detect multiple mixed proteins at the same time; and SELDI technology employs mass spectrometry to detect sequential proteins in a temporal order.
Figure 3: Microarrays for studying protein interactions Three proteins, Protein G, p50, and FRB, were immobilized onto slides in dot arrays. Three fluorescently labeled probes, IgG (blue), I B (green), and FKBP12 (red), were probed with one (A, B, C) or all three (E) at the same time. The three probes interact specifically with each of the three proteins. d indicates the state without any probe.
With the development of human genetic engineering, gene chips (i.e., DNA chips) have been rapidly developed.DNA chips, also known as oligonucleotide arrays or hybridization array analysis, is a technique of molecular hybridization between nucleic acid chains developed according to the principle of the DNA double helix. Its basic structure is similar to a face-array protein chip, on the surface of which thousands of gene units can be prepared as ligands for screening the genes to be tested. The genes to be tested are quantitatively amplified by PCR amplification and then fluorescently labeled to produce a recognizable fluorescence emission or spectral shift during the screening process. This fluorescent signal is detected by a fluorescence microscope for the purpose of gene identification. One side between the known DNA (probe) and the unknown nucleic acid sequence is immobilized in an ordered array onto a slide or silicon wafer, which is then hybridized to the fluorescently labeled other side. Hybridization occurs when the fluorescently labeled side finds complementary sequences on the DNA chip, and the results of the hybridization are detected by fluorescence and pattern recognition analysis.DNA microarray technology can rapidly analyze a large amount of genetic information, thus enabling biomedical workers to study and collect information on gene expression and mutation. There are two types of DNA chips that have been produced and sold by companies at home and abroad. One type is to synthesize the oligonucleotide to be tested in situ on the chip, and then put it together with fluorescently labeled DNA probes, and the complementary sequences are determined by fluorescence scanning when the DNA probes are hybridized to the oligonucleotide arrays. This oligonucleotide array format can be used to detect variants, localize target regions in genes, and studies of gene expression, as well as to determine gene function. Another class of DNA microarrays utilizes microdot sampling techniques to create complementary DNA (cDNA) arrays on a chip, which are then hybridized to fluorescently labeled DNA probes. cDNA array formats are used for rapid screening. The cDNA array format is used for rapid screening. cDNA arrays such as the GeneChip? from Affymetrix, Inc. in Santa Clara, CA, contain high-density DNA probe arrays that can be used to analyze genetic information in the human genome. The special-purpose DNA probe arrays allow rapid screening of known DNA sequences in the human genome.
DNA microarrays can also be used to monitor gene expression in different human cells and tissues to detect changes in genes responsible for cancer or other diseases. With the development of DNA microarrays and hybridization technologies, DNA microarrays will have the potential to be directly applied to clinical diagnostics, drug development, and human genetic diagnostics.
Figure 4: Microarray of gene expression Samples from two cell types are labeled with two colors of fluorescence, hybridized, and then scanned for fluorescence at each bit of the microarray. The light intensity of each bit is proportional to the amount of fluorescent cDNA it binds. The stronger the light intensity, the higher the level of expression of that gene in the sample. If the sites of the microarray do not fluoresce, it means that neither cell expresses the gene. If a site shows one type of fluorescence, the labeled gene is only expressed in this cell sample. If the same site shows two types of fluorescence, the gene is expressed in both cell samples.
(2) Molecular motors
Molecular motors are nanosystems composed of biological macromolecules that utilize chemical energy to perform mechanical work. Natural molecular motors, such as kinesin, RNA polymerase, myosin, etc., are involved in a series of important life activities such as cytoplasmic transport, DNA replication, cell division, muscle contraction, etc., in living organisms. Molecular motors include two main categories: linear propulsion and rotary. Linear molecular motors are biological molecules that convert chemical energy into mechanical energy and move along a linear track, mainly including myosin, kinesin, DNA helicase and RNA polymerase. Among them, muscle myosins are one of the more intensively studied ones, and they have actin (actin) as a linear orbital whose movement is coupled to ATP hydrolysis. Kinesins, on the other hand, use microtubule proteins as orbitals, move along the negative pole of microtubules to the positive pole, and thus fulfill various intra- and extracellular mass transfer functions. Currently, a walking ("hand-over-hand") model has been proposed for the kinesin movement mechanism, in which the two heads of kinesin are alternately bound to microtubules and move along microtubules in a walking manner with a step size of 8 nm (Figure 5). The relationship between ATP hydrolysis and the chemical-mechanical coupling between the mechanical movements of myosin and kinesin is currently unclear. Recent studies have revealed that they share the same central nuclear structure and convert ATP energy into protein motions with similar conformational changes.DNA deconjugases act as linear molecular motors, using the DNA molecule as an orbital and coupling with the energy released by ATP hydrolysis to separate the DNA double strand into two complementary single strands while releasing ADP and Pi.RNA polymerases, on the other hand, are involved in the process of DNA transcription, moving along the DNA template moves rapidly, consuming energy from the polymerization of nucleotides and the folding reaction of RNA.
Figure 5: A model of the cycle of motion of muscle myosin (left) and kinesin
protein (right)
Rotary molecular motors work in a similar way to the rotary motion between a stator and a rotor, and some of the more typical rotary engines are the F1-ATPase. the ATPase is a type of enzyme that is ubiquitously found in living organisms. It is shown in the figure: it consists of two parts, one bound to the mitochondrial membrane, called F0, and the other outside the membrane, called F1.The a, b, and c subunits of the F0-ATPase form a channel for proton flow through the membrane. When protons flow through F0, a moment is generated, which drives the rotation of the g-subunit of F1-ATPase. clockwise and counterclockwise rotation of the g-subunit is associated with ATP synthesis and hydrolysis, respectively. the diameter of F1-ATPase is less than 12 nm, and the enzyme is capable of generating a force greater than 100 pN, and the rotational speed of the enzyme can reach up to 17 rpm when no load is applied. the combination of the F1-ATPase and the nano-nanoNEMS has become a new type of nanomachine device. The combination of F1-ATPase and nanoNEMS has become a new type of nanomechanical device.
Figure 6: Schematic structure of ATPase
Scientists at Connell University in the United States have developed a nano-electromechanical device, the "nano-helicopter," that can enter human cells using ATPase as a molecular motor. The device*** consists of three components, two metal propellers and a biomolecular component attached to a metal rod connected to the metal propellers. The biomolecular component converts ATP, the biological "fuel" of the human body, into mechanical energy, enabling the metal thrusters to operate at a rate of eight revolutions per second. This technology is still in the early stages of development, and its control and application are still unknown. In the future, it may be possible to accomplish medical tasks such as dispensing drugs inside human cells.
Figure 7: U.S. Connell University developed into the "nano-helicopter" schematic
(3) Silicon worm transistor
Researchers in the U.S. and Northern Ireland stumbled upon a living semiconductor (half bacterium, half microchip), which is able to sniff out the toxic gases used in biological warfare. This discovery came from the repeated failure of scientists to eliminate some special bacteria on the production line of computer chips. Researchers have tried everything from ultraviolet light to powerful oxidizing agents to eliminate these microbes, but the bacteria still survive. Robert Baier, a biologist at the State University of New York, explains the phenomenon. When cleaning semiconductor chips, ultrapure water dissolves some semiconductor materials, such as germanium oxide, which crystallize around the bacteria, allowing them to survive in their crystalline "home" without damage. Microorganisms build a "living" unit with semiconducting materials. This phenomenon opens up a wide range of imaginative possibilities. Physicists O'Hanlon and Baier of the University of Arizona believe that bacteria with a hard outer shell could be used to make biological transistors. In a normal transistor, the current from source to drain is controlled by the voltage at the gate. The bacterial semiconductor crystals could be used as the gate of a biotransistor. During biological processes such as respiration and photosynthesis, which produce electron transfer, light or water vapor from the organ can induce the bacteria to produce electrons, as if turning on the biotransistor. This ingeniously sensitive device is capable of detecting biological warfare gases.
They made the bacterial crystal unit with pure water on a semiconductor surface, and the next step is to make it function as a transistor and gain more applications.
Figure 8: A nanosensor probe carrying a laser beam (blue) passes through a living cell to detect whether the cell has been placed under a carcinogen
(4) Nanoprobe
A nanosensor that detects a single living cell, with a probe size on the order of a nanometer, probes for early-stage DNA damage that would lead to a tumor when it is inserted into a living cell.
To mimic exposure to carcinogens, cells are immersed in a liquid containing a metabolite of benzopyr (BaP). Benzopyr is a carcinogen commonly found in polluted urban air. Under normal exposure conditions, cells take up and metabolize benzopyr. The metabolic reaction between benzopyr and cellular DNA results in the formation of a hydrolyzable DNA adduct, BPT (benzo(a)pyrene tetrol). The nanoprobe is a 50 nm diameter, silver-coated optical fiber that conducts a helium-cadmium laser beam. A monoclonal antibody that recognizes and binds to BPT is attached to the tip of the fiber, and the 325 nm wavelength of the laser light excites the molecular complex formed by the antibody and BPT to fluoresce. This fluorescence enters the probe's optical fiber and is picked up by a photodetector.Tuan Vo-Dinh and his colleagues believe that this highly selective and sensitive nanosensor can be used to detect many cellular chemicals, and that it can monitor proteins and other biochemicals of interest in living cells.
The sensor could also detect gene expression and protein production in target cells, and be used to screen trace amounts of drugs to determine which ones are most effective at blocking the activity of disease-causing proteins within cells. With advances in nanotechnology, the ultimate realization is to rate the health of individual cells.
Three, nano-biomaterials
Biomaterials are already familiar content, for example: animal leather used for clothes and belts are biomaterials; materials used for dental veneers and the production of invisible eyes, although not a biologic product, but is used in living organisms, can also be attributed to biomaterials. Nano-biomaterials can also be divided into two categories, one is nanomaterials suitable for application in living organisms, which may or may not be biologically active in themselves, but are simply easy to be accepted by living organisms without causing adverse reactions. Another category is the development of novel nanomaterials that utilize the properties of biomolecules, which may no longer be used in living organisms, but in other nanotechnologies or microfabrication.
(1) Living wires
In many ways, DNA is almost ideal for constructing nanoscale structures. Recently, scientists have synthesized electrically conductive DNA strands by covering the surface of DNA with metal atoms in a cultivation method. However, because DNA is completely covered with metal, it acts only as a scaffold and no longer has the valuable property of selectively binding other biomolecules. Saskatchewan researchers are discovering ways to develop DNA into a new generation of biosensors and semiconductor wires. Researchers in the laboratory of biochemistry professor Jeremy Lee found that DNA easily incorporates ions such as zinc, nickel and cobalt into the center of its double helix, and found a new DNA conductor that stabilizes the metal ion-containing state of DNA under basic conditions such as high pH. Moreover, such metallic DNA still maintains the ability to selectively bind other molecules. One of the applications being developed is genetic aberration detection biosensors. Similar to other DNA detectors, the sensor is fitted with a customized DNA sequence to be detected. Here, the DNA strands are electrically conductive. Deletions or changes induced by hybridizing the DNA act to block the current, and the computer is able to identify the DNA abnormality simply by measuring the change in conductance.
The biosensor can also be used to identify mixtures, such as environmental toxins, drugs, or proteins, and when such molecules bind to metallic DNA, they repel the metal ions, causing the current to be interrupted. Since, the decrease in signal strength is proportional to the concentration of the contaminant, the amount of environmental toxins can be easily determined. Metallic DNA can also be used to screen for anti-tumor drugs bound to DNA, as wires for microfabricated semiconductor circuits, and so on.
(2) Nanobiomaterials in Tissue Engineering
Material scaffolds play an important role in tissue engineering because wall-dependent cells can grow and differentiate only after adhering to materials. Biodegradable materials containing nanofibers that mimic the structure of collagen, the natural extracellular matrix, have begun to be used in tissue engineering in vitro and animal experiments, and will have good application prospects. The nanoscale hydroxyapatite/collagen complexes developed by Tsinghua University in China mimic the inorganic and organic components of the natural bone matrix in composition, and their nanoscale microstructure is similar to that of the natural bone matrix. The porous nanohydroxyapatite/collagen complexes form a three-dimensional scaffold that provides osteoblasts with a microenvironment similar to that in vivo. Cells grow well on this scaffold and can secrete bone matrix. In vitro and animal experiments showed that such hydroxyapatite/collagen complexes are good bone repair nanobiomaterials.
Through the above, it can be clearly seen that the contents of nanomedicine, nanobiotechnology and nanobiomaterials, there is no obvious boundary, and it can be said that they are intersecting and interdependent, **** the same development. This is exactly the meaning of nano-bioengineering.
As we enter the 21st century, the development of nanotechnology will make today's science fiction become tomorrow's practical technology generally accepted by the world.