Optical Detection of Protein Adsorption on Doped Titanium Surface - Biomaterials Science and Engineering - page 182

When effective air layer appears on the surface, the reflectance increases. This air layer exists
on the surface in liquid in the form of nanobubbles. On the contrary the formation of oxide
layer on the surface, for the calculated oxides TiO 2 ,Al 2 O 3 and V 2 O 5 decreases the reflectance,
and thus the observed gloss values.
Figure 9 presents the temporal responses of gloss and R opt from a polished titanium surface
(Ti p ) surface when surface is immersed in water and in PBS without and with HPF molecules.

x 10 −8

70

water
PBS
HPF

water
PBS
HPF

3.5

65

3

60

55

2.5

50

500 1000 1500 500 1000 1500

t (s) t (s)

(a) (b)

Fig. 9. (a) Temporal gloss ( G ) in GU and (b) optical roughness R opt in meters of a Ti p surface,
when the surface is in water, in PBS without and with HPF-molecules with 500 nM
concentration.

When the surface is presented with the PBS, gloss decreases and R opt increases. This is caused
by the chemical reaction from PBS, causing surface energy driven formation of oxides and
the mobility of initial gas nanobubbles on the surface (see figure 8). Also the formation
of additional nanobubbles can occur, but that would require increase in gloss values, like
observed in similar case with Ti6Al4V surface in figure 10.

x 10 −8

water
PBS
HPF

water
PBS
HPF

420

4.2

400

4

380

3.8

360

3.6

340

3.4

320

500 1000 1500 500 1000 1500

t (s) t (s)

(a) (b)

Fig. 10. (a) Temporal gloss ( G ) in GU and (b) optical roughness R opt in meters of a Ti6Al4V
surface, when the surface is in water, in PBS without and with HPF-molecules with 500 nM
concentration.

After the PBS solution measurement the cuvette is emptied and the HPF solution is injected
in the cuvette. The HPF solution typically has higher changes in the signal from water than