Multiple experiments on Teflon and thick films of ferric stearate
demonstrated the influence of a solution of holo-TLs on the wettability
of hydrophobic surfaces
(Table 1) . A representative experiment is shown in
Figure 4 . Droplets, 40 μl in volume, of buffer, tears, and reconstituted tears
depleted of TLs were placed on a clean Teflon surface
(Fig. 4A) . The
droplets with protein showed reduced initial contact angles for tears
(80°) and tears depleted of TLs (85°) indicating a reduction in
surface tension compared with buffer (104°). After aspiration,
droplets of 20 μl of buffer (a smaller volume was used to ensure that
the drop remained within the boundaries of the prior 40-μl droplet)
were replaced within the same area
(Fig. 4B) . The corresponding contact
angles, 54° and 57°, respectively, were reduced indicating, a
general interaction typical of most proteins with the Teflon surface
(Table 1) . The experiment was performed with purified TLs, lactoferrin,
and lysozyme on Teflon (
Figs. 4C ,
4D ) with similar results. The same
experiment was performed on a ferric stearate surface (
Figs. 4E ,
4F ).
The initial contact angle of 146° for buffer is typical of
hydrocarbon surfaces. When a 40-μl droplet of tears was applied, the
contact angle was slightly lower (133°), indicating a reduction in
surface tension compared with the contact angle of tears depleted of
TLs (143°). After aspiration and reapplication of 20 μl of buffer,
a much lower contact angle was observed (105°), indicating a marked
interaction with ferric stearate
(Fig. 4F) . When the major protein
components of tears were tested, the contact angle was most reduced on
the spot where TLs (110°) had been placed, indicating a marked
interaction with the ferric stearate surface (
Figs. 4G ,
4H ). A much
smaller reduction was observed for other components, 124° for
lactoferrin and 131° for lysozyme.