Calcification crystal initiation

Calcification mechanisms. The mechanisms of CaCOs deposition have not been clearly defined. Two major questions are involved first, the relation of the organic portion of the skeleton to the initiation and control of crystal growth and, second, the role of the symbiotic photosynthetic zooxanthellae, the algae which grow within the tissue of hermatypic corals (Chapman, 1974). Another persistent question has been the site of crystal initiation, whether it is entirely extracellular or whether it is partly intracellulfir as well (Muscatine, 1971). 

In the calcification process of bone formation, the initial crystals of hydroxyapatite are found at intervals of 67 nm along the collagen fiber. What is the reason for this ... 

The last theory on stone formation comprises the matrix theory in which proteins may play an important role in urolithiasis (FI). This theory is based on analyses of many stones, which revealed that the core of these stones contained protein. It had been shown in vitro that certain proteins bind calcium and even induce the calcification process (Rl). These proteins, also called promoters, were therefore considered to be able to activate the initial crystallization process. However, these results could not be verified (FI). Recently it has been shown that in vitro calcium oxalate crystals do contain protein and that the crystallization in urine is not a random event, but rather a selective phenomenon (M4). This supports an earlier statement that stones contain about 1.6% of their weight in nondialyzable extractable protein and that the composition is the same for all stones, regardless of their mineral composition (S7). 

The term biocompatibility is defined as the ability of a material to perform with an appropriate host response in a specific situation" (Williams 2008). A biocompatible material can be inert, where it would not induce a host immune response and have little or no toxic properties. A biocompatible material can also be bioactive, initiating a controlled physiological response. For porous silicon, bioactive properties were initially suggested based on the observation that hydroxyapatite (HA) crystals grow on microporous silicon films. HA has implications for bone tissue implants and bone tissue engineering (Canham 1995). An extension of this work showed that an applied cathodic current was able to further promote calcification on the surface (Canham et al. 1996). More recently, Moxon et al. showed another example of bioactive porous silicon where the material promoted neuron viability when inserted into rat brains as a potential neuronal biosensor, whereas planar silicon showed significantly fewer viable neurons surrounding the implant site (Moxon et al. 2007). 

When a medical device is in contact with body fluid such as blood, the first thing that occurs on the surface is protein adsorption [96-98]. Proteins in solution trying to minimize the total surface energy is the thermodynamic driving force of protein adsorption on solid surfaces. In blood contact protein adsorption is believed to be the initial event in thrombus formation [99-101], calcification [102-104], and biofilm attachment [105-107], which leads to the failure of implanted devices. Therefore, protein-reducing surface modifications of polyurethane biomaterials have been applied to improve the service life of implants. Previous studies of protein adsorption have focused on adsorption of albumin, IgG, and Fg, which are the predominant three proteins in blood plasma. Surface protein adsorption can be quantitated by several methods such as quartz crystal microbalance (QCM) [108-112], surface plasmon resonance (SPR) [113-118], and iodonization radiolabeling [78,119-125]. 

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