TITANIUM NITRIDE AND DIAMOND LIKE CARBON COATINGS FOR CARDIOVASCULAR APPLICATIONS - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 668

21.3 HEMOCOMPATIBILITY

The success of any material in the biological environment is defi ned by its reac-
tion to and from the surrounding environment. But there is no universally
accepted defi nition for biomaterial and biocompatibility. In general, it is under-
stood that a biomaterial is required to perform with appropriate host response in
a specifi c application . Hence no single test can be used for ascertaining the bio-
compatibility of a material and a material cannot be categorically stated as a
biocompatible. But it can be concluded, through a series of properly selected
qualifi cation studies, that a material is suitable for use in a certain specifi c applica-
tion. The most popular and accepted standard in this area is ISO 10993: Biological
evaluation of medical devices , which addresses the issue of biocompatibility by
categorizing the materials based on the nature and duration of body contact. In
this context, the classifi cation of biomaterials based on the nature of body contact
takes practical signifi cance and biomaterials get classifi ed as cardiovascular,
orthopedic, dental, wound care materials, etc.
Blood constitutes about 8% of the total body weight of the human and con-
tains mainly water ( 90%), proteins such as albumin, globulins, fi brinogen, differ-

ent types of cells (platelets, white and red cells), ions and different organic
nutrients such as lipids and carbohydrates [see Table 21.2] [Moriau et al., 1988].
All these components are implicated in several complex physiological processes
related to the multiple functions of blood such as:

>

• transport of gases, nutrients, waste products, regulatory molecules;
• regulation of pH and osmosis;

TABLE 21.2. Major Constituents of Blood

Constituent Primary function(s)

Plasma (55%) Water 92% Transport

Proteins 7% Albumin (58%) Capillary colloid; reduces fl uid

leakage out of capillaries; transport

Globulin (38%) Substrate for formation of other

molecules; immunity [antibodies];
transport

Fibrinogen (4%) Blood clotting

Other Solutes (1%)
Na + , K + , Ca 2+ , Mg 2+ , Cl − , HCO − , HPO 2− , SO 2−
Organic nutrients (lipids, carbohydrates, amino acids)
Organic wastes (urea, uric acid, creatine, bilirubin)

Formed
Elements

Platelets (250 - 400 × 10 3 /mm 3 ) Blood clotting

WBC (5 - 9 × 10 3 /mm 3 ) Immunity

RBC (4200 - 6200 × 10 3 /mm 3 )
(> 99.9%)

Transport