**2.1 Preface**

30 Ceramic Coatings – Applications in Engineering

Picture PH NO3- (M) i(mA/cm2) t(min) Result a 0.71 0.02 20 4 No film b 1.2 0.02 20 4 Thick film c 1.2 0 20 4 Thin film d 1.2 0 5 4 No film e 1.2 0.02 5 4 No film f 1.2 0.2 5 4 Thick film

Table 1-2. Processing parameter and electrodeposition result in electrolyte of different PH

1. In self-prepared Ti(SO4)2 solution of electrolyte (PH1.2), at a constant current density of 5mA/cm2, cathodically-electrodeposited for 4min, a layer of amorphous Ti-O film could be obtained on TiNi SMA. This Ti-O film is composed of a lot of fine and close particles gathered, the particles' size in dozens of nanometers. And the atomic ratio of Ti and Ni reached to 3:1 through a primary detection by EDS. This illustrates that there were a lot of Ti element included in the film, and this closely bonding of fine particles

2. Through XPS analysis, Ti-O film elements of TiNi SMA cathodically-electrodeposeted

3. After the sample cathodically-electrodeposited Ti-O film was crystallized at 300C, no TiO2 existing was found, but crystallized at 450C, there was anatase TiO2 peak emerging. After the non-deposited blank TiNi SMA sample was crystallized at 450C, there was no TiO2 peak emerging. This illustrates that the film obtained by cathodicelectrodeposition was certainly an amorphous Ti-O film, and its composition was

4. The tests of corrosion potential and electrochemical corrosion illustrated that the TiNi SMA cathodically-electrodeposited presented the better thermodynamic stability and corrosion resistance in Hank's solution (PH7.45) and Fusayama solution (PH6.13). 5. At different current densities, there was much different in roughness, even level, thickness and crack of Ti-O film surface morphology of cathodically-electrodeposited TiNi SMA, among them, the film obtained at the current density of 5mA/cm2 was the best one. 6. The thermodynamic stability and electrochemical anti-corrosion of the cathodicallyelectrodeposited samples at different current densities in Hank's solution (PH7.45) and Fusayama solution (PH6.13) were different. Those of the sample deposited at current density of 20mA/cm2 were better. But for the one crystallized at 450C, and cathodically-electrodeposited at the current density of 5mA/cm2, its thermodynamic

7. The surface morphologies of Ti-O film before and after crystallization at 450C were different. The crystallized Ti-O film was distributed in fine and close particles. Moreover the sample before crystallization had better thermodynamic stability and corrosion resistance in Hank's solution (PH7.45) and Fusayama solution (PH6.13). 8. The morphologies of the Ti-O film(s) obtained which were cathodicallyelectrodeposited for different times were different. At the current density of 20mA/cm2, The Ti-O film change with time was a growth process of "thickening-cracking-

has contributed to strengthening the surface properties of TiNi SMA.

values and NO3- concentrations

**1.4 The summary of this chapter** 

existed in form of TiO2 or hydrate Ti(OH)4.

stability and electrochemical anti-corrosion were better.

existed in form of hydrate Ti(OH)4.

The key, for a plant material to bonding surface, is that the material must be with excellent bioactivity, that is, the biomaterial should have capability of closely bonding with surrounding living tissue under physiological fluid environment[9]. The bioactive bonding called, is that after a bone plant is planted into human body, there will be a layer of bioactive hydroxyapatite (HA) forming on the material's surface. HA is a main inorganic substance, occupying about 69%, and about 41.8% in volumetric fraction of human bone. Through HA thin layer, chemical bonding at a molecular level is formed. After planting into human body for 3-6 months, the interface strength of the bioactive bonding is equal to or higher than that of surrounding bone tissue[9]. Under the circumstance of guaranteeing other properties, promoting coating's bioactivity will be helpful to shorten osseointegration period, make patient's injured site(s) recover the functions early, and alleviate suffering[10].

Blood compatibility includes quite wide content. There are the reactions at cell level, such as thrombosis (platelet adhesiveness, agglomerating, and deformation) when connecting with material, haemolysis and leucopenia; there are the reactions at plasma protein level, such as coagulation system and fibrinolytic system activation; and there are the reactions at molecular level, such as immune ingredient change, platelet receptor and ADP (adenosine diphosphate)[11].

When a material connects to blood, a competitive protein adsorption will come about first to form a complex protein adsorption layer, then blood cell and platelet adhesiveness, and then thrombosis, if which can not be repaired or cured, it is easy to bring about coagulating. So, avoiding thrombosis and preventing coagulation are the most important factors of a biomaterial's blood compatibility. Approach a mechanism of thrombosis to promote material's blood compatibility is a research hot point in the academic circle[12,13], and it has been made a great progress recent years.

In this chapter, evaluations for the biomaterials' blood compatibility in vitro have been experimentally carried out in following two aspects[14]:

1. Haemolysis rate test For a plant apparatus directly connected to blood, it is necessary to carry out the experiment on haemolysis rate in vitro. Under normal circumstance, the average life of erythrocyte is 120d. Under the same reason, the life of erythrocyte shortens, it is called that a haemolysis process comes about. Through haemolysis rate experiment the rank of toxicity produced by erythrocyte in blood connecting to material can be evaluated, the erythrocyte in blood will be damaged in varying degrees because of the toxic substance(s) of the material, to release hemoglobin, and to bring about haemolysis. By testing the amount of hemoglobin released from the material, the haemolysis rate for the material can be obtained. Generally speaking, the concentration

Ti-O Film Cathodically-Electrodeposited on

2000type of X-ray diffractormeter (XRD).

absorbance hemolysis rate was taken out.

coagulation time for different materials.

**2.3.1 Evaluation of biocompatibility of TiNi SMA surfacely-modified** 

**2.3 Experimental results and discussion** 

compound ACD blood.

time.

layer on the surface was detected with Finder 1000 type of EDS.

**2.2.2.2 Test of hemolysis rate of TiNi SMA after surfacely- modified** 

the Surface of TiNi SMA and Its Bioactivity and Blood Compatibility 33

coated with silica gel. Dipping for 7d in a water bath at 37C. The deposition of the Ca/P

The samples before and after cathodic-electrodeposition respectively were dipped into 25ml SBF solution of PH7.40. The working area was 10mm×10mm, and the non-working one was coated with silica gel. Dipping for 7d in a water bath at 37C1C, the solution was changed every two days. The deposition of the Ca/P layer on the surface was detected with Finder 1000 type of EDS. And the hydroxyapatite (HA) on the surface was analyzed with D/max

8ml fresh rabbit blood selected was anti-coagulated with 1ml heparin solution, and diluted with 10ml physiological saline. The samples were put in 10ml physiological saline in the water bath at 37℃, then putting in 0.2ml dilution blood, mixing well gently, and continuing to keep the temperature for 60min. Then the fluid was poured into a test tube, separated at a speed of 1000r/min with LXJ-64-01 type of separator, and the up layer solution was taken out to test absorbance value at wave length of 545nm with Lambda 35 type of spectrophotometer. Anode control group used 10ml distilled water + 0.2ml dilution blood,

> (%) *t nc* 100% *pc nc D D D D*

*Dt* : Sample absorbance; *Dnc* : Cathode control group absorbance; *Dpc* : Anode control group

1. To compound an ACD blood and 0.47g citric acid, 0.3g glucose and 1..22g sodium citrate were dissolved in 100ml distilled water to compound the blood preservation solution (ACD). Taking that fresh rabbit blood : ACD as 1 : 4 in proportion to

2. Taking 0.2ml ACD blood and dropping on the surface of the test material after clearing. Adding to 20μl from the 0.2ml CaCl2 solution, then mixing well and then recording

3. At 5, 10, 20, 30, 40, 50 and 60min of given times, respectively having 100ml distilled water flowed through the material surface slowly, the fluid was gathered up to a beaker, the absorbance values (O. D.) of the solution at different times were got at 540nm wavelength with Lambda 35 type of spectrophotometer, and plotting the O. D.-t curves to compare. Taking the connecting time at 0.100 absorbance as the dynamic

Figure 2-1 shows the EDS results of Ca/P deposition on TiNi SMA before and after anodicoxidation respectively in SBF solution for 7d. It is seen from Figure 2-1a that there was small

(2.1)

and cathode one 10ml physiological saline + 0.2ml dilution blood. By the formula:

**2.2.2.3 Test of dynamic coagulation time of TiNi SMA after surface modification** 

of a toxic substance which can produce haemolysis reaction is higher than that of the one which can only produce toxic effect. For the biomedical materials, it is extremely important to alleviate erythrocyte damage.

2. Dynamic coagulation time test Blood would be activated to coagulate and to affect platelet's formation and function as a material connects with blood. And blood coagulation is a result from a series of reaction in blood. There are two processes which would initiate coagulation, that is, intrinsic coagulation (activated by coagulation factor XII) and extrinsic coagulation reactions. Firstly, prothrombin factor XII was changed into active factor XII a; the active XIIa made the coagulation factor XI change into an activation factor XIa, and furthermore made factor IX activate to be IXa; then the activated IXa combined with the factor VIII, phosphatide and C2+ ions to form a complex compound, which would make factor X change into activation factor Xa; furthermore, the active factor Xa combined with factor Va, phosphatide and C2+ to form the complex compound which would make prothrombin change into thrombin; finally, the thrombin made fibrinogen molecules change into fibrinogen monomer, then into the fibrin colloid under the action of activated factor XIII a, thus forming the blood clots. On the other hand, the extrinsic clotting system, activated by tissue factor and VII factor, directly made the factor X activate to be Xa, the next process emerged was as the same as the intrinsic one's[15].

The process of blood coagulation shows that globin and fibrin in blood on material's surface would bring about activation of the coagulation factor, thus causing fibrin to form and to coagulate. At the same connecting time, by the experiment of dynamic coagulation time in vitro, the activation degrees of different materials on intrinsic coagulation factor can be compared. The activation degrees on coagulation are different, so are the coagulation degrees. With the time of material connecting to blood, coagulation degrees increases correspondingly. The dynamic coagulation time curve is a relation curve to absorbance and time. The more smooth the curve is, the longer the coagulation time lasts, it shows, and the lower the degree activated by coagulation is. And the longer the coagulation time lasts, it shows, the lower the degree for a material to bring about thrombus is, and the better the material's anti-coagulating property is.
