Organic raw material

Hydroxyapatite (Hap, Hap or HA), as a naturally occurring form of the mineral calcium apatite, has its chemical formula precisely expressed as Ca5(PO4)3(OH), and to more clearly display its crystal structure, this chemical formula is often rewritten as Ca10 (PO4) 6(OH)2. Such a statement aims to emphasize that its crystalline unit, the cell, is composed of two interrelated entities. In the big family of mineralogy, hydroxyapatite plays the role of a hydroxyl terminal member that complexes apatite groups. This characteristic makes it occupy a place among many apatite minerals.

It is worth mentioning that the hydroxide ions in hydroxyapatite are not irreplaceable. They can be replaced by ions such as fluorides or chlorides, thereby forming varieties such as fluorapatite or chlorapatite. This phenomenon of ion replacement not only enriches the types of apatite minerals, but also provides more possibilities for studying the properties of such minerals.

From the perspective of crystallography, hydroxyapatite belongs to the hexagonal system, and this feature determines its unique physical and chemical properties. In a pure state, hydroxyapatite powder presents a flawless white color, as pure as the first snow in winter. However, apatite formed in nature may have a rich variety of colors due to the influence of various geological conditions. Besides white, it may also present multiple tones such as brown, yellow or green. These color changes are similar to the discoloration phenomenon of dental fluorosis.

In living organisms, hydroxyapatite also plays a crucial role. Up to 50% (by volume) and 70% (by weight) of human bones are composed of bone minerals, a modified form of hydroxyapatite. This special mineral form endows bones with strong support and good toughness. In terms of teeth, hydroxyapatite lacking calcium carbonate is the main constituent mineral of enamel and dentin, and together they safeguard our oral health.

In addition, hydroxyapatite crystals also play an important role in the process of pathological calcification. For instance, in breast tumors and the pineal gland (as well as other structures of the brain), calcified substances known as sarcoids or "brain sands" are sometimes found, and these substances often contain hydroxyapatite crystals. These findings not only reveal the wide distribution of hydroxyapatite in living organisms for us, but also provide new ideas and clues for the diagnosis and treatment of related diseases.

Hydroxyapatite plays an extremely important role in the biological world and human life activities. It is widely present in the bones and teeth of mammals and humans, just like the cornerstone of a building, providing solid support for the body structure.

As for the bones, their composition has an exquisite design. Bone is not a single and uniform entity, but is ingeniously composed of hyaluronic acid crystals scattered in the collagen matrix. Among them, the proportion of hyaluronic acid in bones is considerable, reaching approximately 65% to 70%. This unique composition structure endows the bones with both a certain degree of flexibility and sufficient hardness, enabling them to withstand the forces exerted by the human body in daily activities and various sports, while also adapting to changes in the external environment to a certain extent. By the same token, hyaluronic acid also plays a crucial role in the dentin and enamel of teeth, accounting for approximately 70% to 80% of its mass. It is worth noting that in tooth enamel, the matrix of hyaluronic acid is composed of both tooth enamel and amyloid protein, rather than collagen. This further demonstrates the subtle differences and high adaptability in the material composition of different parts to achieve their respective specific physiological functions.

However, the presence of hydroxyapatite is not always beneficial. In some cases, it can cause some health problems. For instance, when hydroxyapatite deposits in the tendons around the joint, it can cause calcific tendinitis. This kind of inflammation can cause patients to experience symptoms such as pain and restricted movement, bringing many inconveniences to their daily lives and seriously affecting their quality of life. In addition, hydroxyapatite is also one of the components of calcium phosphate kidney stones. The formation of kidney stones is often related to multiple factors, and the presence of hydroxyapatite among them undoubtedly intensifies the complexity of the condition and the difficulty of treatment, posing a potential threat to the kidney function of patients.

In the field of oral health, enamel remineralization is a topic of great concern. Enamel, as the outermost protective structure of teeth, its health condition is directly related to the overall function and appearance of teeth. The remineralization process of enamel is essentially the reintroduction of mineral ions into the demineralized enamel. As hydroxyapatite is the main mineral component of tooth enamel, during the demineralization process, calcium and phosphate ions are extracted from hydroxyapatite, which damages the structure of tooth enamel and makes it fragile and vulnerable. During the remineralization process, by introducing mineral ions, the structure of hydroxyapatite crystals can be restored, thereby repairing the damage to tooth enamel. It is worth mentioning that if fluoride ions are present during the remineralization process, whether through public health measures such as water fluorination or personal oral care methods such as using fluoride toothpaste, stronger and more acid-resistant fluorapatite crystals can be formed instead of ordinary hydroxyapatite crystals. The appearance of fluorapatite crystals provides a more solid protective barrier for tooth enamel, which helps prevent the occurrence of oral diseases such as dental caries.

In the wonderful world of Marine life, the rod-shaped appendages of the peacock mantis shrimp exhibit astonishing and unique properties. This unique body structure is meticulously crafted from a mineral of extremely high density and possesses an extraordinary specific strength. This outstanding performance has aroused great interest among scientific researchers, prompting them to conduct in-depth studies on its potential value in the preparation of synthetic materials and engineering applications. The excellent performance of the rod-shaped appendages of the peacock mantis shrimp is fully demonstrated in terms of impact resistance. When impacted, the impact area is mainly composed of crystalline hydroxyapatite, which has a relatively high hardness and can effectively resist the invasion of external impact forces. The periodic layer located beneath the impact layer is also composed of hydroxyapatite, but the content of calcium and phosphorus in it is relatively low (and therefore the modulus is much lower). This special structural design enables the periodic layer to suppress the crack propagation by forcing the new crack to change direction when facing impact, thereby greatly enhancing the impact resistance of the entire structure. In addition, due to the significant difference in modulus, this periodic layer can also reduce the energy transmitted between the two layers and even reflect part of the incident energy, further enhancing its ability to resist shock and providing a strong guarantee for the survival of this Marine organism in the complex Marine environment.