Chapter 1: A Brief Introduction to Blood Purification Materials
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Published:27 Jan 2025
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Special Collection: 2025 eBook CollectionSeries: Biomaterials Science Series
S. Sun, W. Zhao, and C. Zhao, in Blood Purification Materials, ed. C. Zhao, Royal Society of Chemistry, 2025, vol. 19, ch. 1, pp. 1-5.
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Although the complete story of the exploration of blood purification can be traced back many years, the history of modern blood purification research is actually not long. With the recent developments in materials science and technology, blood purification materials, including membranes and adsorbents, have growing importance in the treatment of various blood-related diseases. This chapter provides a brief overview of the materials involved in blood purification, and an overall description of the contents of this book.
1.1 Blood Purification
In the distant past, people had already realized that blood is closely related to the health of the body. The ancients believed that certain substances (toxins) in human blood were the cause of some diseases. More than 2000 years ago, the classic medical work of ancient China, The Yellow Emperor’s Classic of Medicine (Huangdi Neijing),1 recorded the method of bloodletting through acupuncture, through which it was believed that some diseases such as insanity, headache, sudden silence, hot asthma, and epistaxis could be treated.
In early Rome and later in the Middle Ages, some patients suffering from uremia were soaked in baths, and it was hoped that the toxins and water would be removed from their bodies into the bath water through sweating and steam.2,3 This can be regarded as an embryonic form of dialysis.
Since the blood circulation was discovered by William Harvey,4 deep and detailed scientific research studies have been conducted on the composition and function of blood, and also methods for the treatment of blood-related diseases. In 1854, the Scottish chemist Thomas Graham first proposed the concept of “dialysis”, which earned him the title of “the father of modern dialysis”.5 In 1925, the renowned German scholar George Haas first applied dialysis technology to humans. Although this attempt failed, it laid the foundation for the development of dialysis.6,7 In 1943, Willem Kolff, a famous Dutch scholar, designed the rotating drum artificial kidney, which was used to treat a patient with acute renal failure successfully for the first time in history.8,9 On the other hand, Steinberg reported in 1944 that an ion-exchange resin could be used to remove calcium from blood and could act as an anticoagulant instead of citrate.10 In 1948, Muirhead and Reid first proposed the concept of a resin artificial kidney, and carried out animal experiments with Amberlite IR-100H resin, although the efficiency of removing urea and creatinine was low.11 Later, Rosenbaum et al.16 used an ion-exchange resin to carry out hemoperfusion in patients with uremia and acute liver failure.
In 1964, Yatzidis first used activated carbon to treat patients with uremia by hemoperfusion.12 It was found that good adsorption could be achieved with small-molecule substances, e.g. creatinine, uric acid, and phenols, although carbon particles could easily become detached and form a thrombus. So far, blood purification technology has developed into a series of treatment methods, making significant contributions to the therapy of various diseases. Taking hemodialysis as an example, it was estimated that the number of dialysis patients was over 3.9 million worldwide in 2022.13
Blood purification is a therapy based on the extracorporeal treatment of blood, and is widely used nowadays for the treatment of many blood-related disorders that are refractory to conventional therapies, such as drug administration and surgery.13 It works by removing harmful substances (such as toxins or pathogenic agents) in the blood, or correcting the blood composition, through dialysis, filtration, adsorption, or a combination of any of these, and also gas transfer. Owing to its capacity for the direct and rapid removal of pathogenic agents from patients, blood purification therapy is mainly employed in three areas in the clinic: (1) critical care, such as plasmapheresis for toxicants; (2) life support for organ failures, such as hemodialysis for renal failure; and (3) redress of metabolic and immune disorders, such as immunoadsorption for autoimmune diseases.13–15 Now, blood purification therapy mainly includes hemodialysis (HD), hemofiltration (HF), plasmapheresis (PP) or plasma exchange (PE), hemoperfusion (HF), blood oxygenation (BO), and so on.
Because the equipment used in some blood purification techniques such as hemodialysis and hemoperfusion can be used for the treatment of patients with renal failure, and can partially replace the function of the human kidney, it also called “artificial kidney”. On the other hand, that in techniques supporting the treatment of patients with hepatic failure is called “artificial liver”, and blood purification equipment that supports the treatment of patients with respiratory failure is commonly called “artificial lung”. In fact, several blood purification techniques can be used in the artificial kidney and the artificial liver support system.
In addition, blood purification technology also plays an active role in the treatment of endogenous and exogenous poisoning, immune diseases, organ transplantation, and other areas, and increases the survival rate of patients. Thanks to blood purification, some diseases that were considered incurable in the past, e.g. acute drug and chemical poisoning, systemic lupus erythematosus, rheumatoid arthritis, hemophilia, and many other diseases, have been effectively treated and the methods used have attracted extensive attention from the medical community worldwide.
The blood purification technologies can be summarized as shown in Table 1.1.
Classification of blood purification technologies
Technology | Technique |
Artificial kidney | Hemodialysis (HD) |
Hemofiltration (HF) | |
Hemodiafiltration (HDF) | |
Hemoperfusion (HP) | |
Plasmapheresis | Plasma separation (PS) |
Plasma fractionation (PF) | |
Artificial lung | Oxygenator Extracorporeal membrane oxygenation (ECMO) |
Artificial liver supporting system | Hemoperfusion |
Plasmapheresis | |
Hemofiltration (HF) | |
Other | Adsorptive separation |
Immunoadsorption |
Technology | Technique |
Artificial kidney | Hemodialysis (HD) |
Hemofiltration (HF) | |
Hemodiafiltration (HDF) | |
Hemoperfusion (HP) | |
Plasmapheresis | Plasma separation (PS) |
Plasma fractionation (PF) | |
Artificial lung | Oxygenator Extracorporeal membrane oxygenation (ECMO) |
Artificial liver supporting system | Hemoperfusion |
Plasmapheresis | |
Hemofiltration (HF) | |
Other | Adsorptive separation |
Immunoadsorption |
1.2 Materials for Blood Purification
1.2.1 Classification
According to the types of blood purification materials, they can be roughly divided into membranes and adsorption materials. The former mainly screen specific components in the blood through the micropores on the membrane, whereas the latter mainly adsorb and clear certain components in the blood through the large specific surface areas and/or special sites with specific or non-specific adsorption.
The materials used in blood purification are mainly polymeric materials, and almost all of the membranes used currently in blood purification are biomedical polymeric materials. Only a small number of inorganic materials (such as activated carbon, usually coated with polymers) are used in hemoperfusion.
From the perspective of material sources, blood purification materials can be divided into natural derivative materials and completely synthetic materials. The former include membrane materials based on cellulose or chitosan. The latter include various synthetic polymeric materials used as membranes and adsorbents for blood purification, such as polysulfone (PSF), polyethersulfone (PES), polyacrylonitrile (PAN), and so on.
1.2.2 Requirements for the Materials for Blood Purification
As the materials contact blood directly, hemocompatibility is the first consideration. After contacting with blood, the surfaces of all artificial materials will interact with proteins and cells, and will also have a profound impact on various coagulation factors, immune system, and complement system in the blood. Among these, the anticoagulant performance of the materials is the most important issue in terms of hemocompatibility of blood purification materials.
To achieve the desired result of blood purification, the effectiveness of the blood purification materials is also a very important indicator. For both membranes and adsorbents, the separation or adsorption effect will be seriously affected by fouling due to adsorption and deposition of proteins, cells, and other substances on the surfaces of the materials after contacting with blood. Therefore, maintenance of the expected effectiveness during the application of these materials is also a very important issue.
The production process and cost of blood purification materials also need to be considered. Generally, the production process for membrane materials is similar to that for chemical fibers, i.e. membranes can be made by melting or solution film-forming methods, in which thermally induced phase conversion or liquid–liquid phase conversion occurs. Adsorbents can be synthesized directly from monomers, in addition to being made from polymer material solutions. Choosing the most appropriate production processes can accurately control the structures of membranes and adsorbents and achieve large-scale production under cost-controlled conditions.
1.2.3 Auxiliary Materials for Blood Purification
In the process of blood purification, after leaving the human body blood comes into contact with not only functional membrane materials or adsorbents, but also many auxiliary containers and pipelines. The biocompatibility of these materials and their products is also crucial to the blood purification process.
1.3 Contents of the Book
In this book, current blood purification materials, including membranes and absorptive materials, are comprehensively and systematically reviewed. After this introductory chapter, the requirements and challenges of hemocompatibility for blood purification materials are discussed in the second part. The third part focuses on membrane materials used for blood purification, including the category, preparation, and modification of blood purification membranes; the membranes used in a liquid–liquid environment, e.g. hemodialysis, hemofiltration, and plasmapheresis; the membranes used in a liquid–gas environment, i.e. artificial lungs; and blood purification materials for hybrid artificial organs. In the fourth part, the adsorbents used in blood purification are discussed, including the categories, characteristics, and applications of adsorbents for blood purification; in vivo evaluation and application of adsorbents for hemoperfusion; in vivo evaluation and application of adsorbents for a bioartificial liver; and novel biomaterials for immunosorbents and bionic adsorbents. The fifth part covers the processing and assembly of blood purification materials, including membranes and adsorbent devices. The final part provides a brief outlook on future development trends in blood purification materials.