Page 84 - Magnesium-based supports for stem cell therapy of vascular disease - Mónica Echeverry Rendón

CHAPTER 5
2.4 Wettability
Contact angle of the samples before and after sterilization were measured. For this procedure, a drop of deionized water was dispensed on each sample then the contact angle was measured with the help of a Goniometer/Tensiom- eter Ramé-hart Model 250 Standard. The measurement was performed in triplicate, in three different samples and the average of the all measurements was calculated. Those values were used to calculate the surface energy (γ(S )) by the numerical iterations and using the Neuman method described by the (Eq. 1), where β = 0.0001247 (m2/mJ)2, γ_(L )=72.8 mJ·m-2 and θ (contact angle)
2.5 Hemolysis test
Healthy human blood from volunteers was collected in a flask containing sodium citrate (0.109M, 3.2%) in a ratio 9:1. Then, the blood was diluted with saline solution in a ratio of 4:5. After that, samples were dipped in tubes containing 10 ml of saline solution and incubated at 37oC for 30 min. Then, 0.2 ml of diluted blood were added to each tube, mixed carefully and incubated at 37oC for 60 min. After that, tubes were centrifuged at 3000 rpm for 5 min. Supernatants were removed and transferred to a plate in order to do spectroscopic analysis at 545 nm. Normal saline solution was use as a negative control and deionized water as positive control. The hemolysis was calculated based on the Eq.2:
3. Results
3.1 Characterization of the sample
The samples were treated under potentiostatic mode in a solution base of silicate. According to the current density- time curve we observed that in the beginning of the process, the system reached the maximal value of 166mA·cm-2 due to the low resistance of the system (given for the substrate and electrolytic solution) and after 36s, in response to the growing of the barrier layer, the current dropped down drastically until 60 mA·cm 2. Then in the phase 2, the current decreased slowly during 60s until it reached a value of around 2mA·cm 2, in this point the phase 3 started and the current remained constant.
Fig.1 Current density-time curve of the anodizing process of the c.p Mg in silicate solution.
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