Raman Microscopy and Imaging: Applications to Skin Pharmacology and Wound Healing - Emerging Raman Applications and Techniques in Biomedical and Pharmaceutical Fields - page 370

Results

Confocal Raman spectra of skin following topical application of 60% α -TAc

in octanol were acquired every 2 m. The first

15 spectra of skin in the 450-1100 cm − 1 range are shown in Fig. 15.7b. The
spectral region selected for the current work, 450-600 cm − 1 , is free from oc-
tanol bands. Both

μ m to an overall depth of 60 μ

-TH exhibit (Fig. 15.7c) a strong feature at
485 cm − 1 whose presence permits us to track the penetration of

α -TAc and α

-
TH, although the relative proportions of the two cannot be deduced from
this single common spectral feature. The integrated area ratio, I (485) /I
(1004) cm − 1 , thus tracks the relative

α -TAc or α

-TH concentration in
skin; the 1004 cm − 1 band is a Phe ring mode from skin proteins whose in-
tensity corrects for the depth dependence of the scattering, as discussed else-
where [3].
Confocal Raman images were acquired from 50

α -TAc and/or α

μ m (axial) × 20 μ m (lateral)

areas with step sizes of 2 m in the lateral

direction. The map of the integrated area ratio 485 cm − 1 / 1004 cm − 1 is plotted
in Fig. 15.8. Most of the exogenous

μ m in the axial direction and 4 μ

∼

m into skin with a
more-or-less monotonic diminishing gradient at depths between 15 and 30

α -TAc permeated 15 μ

μ m.

Small pockets of material are observed at depths of m.

To distinguish the SC from the underlying epidermis and hence to define
the site within the skin to which the

∼ 30-35 μ

-TAc had permeated, a confocal Raman
image was acquired from an untreated section taken from the same piece of
skin whose spatial distribution of factor scores is depicted in Fig. 15.3c. A
comparison of Fig. 15.3c (factors 1 (SC) and 4 (epidermis)) with the map
of

α

-TAc remains localized
mostly in the stratum corneum, with little reaching the viable epidermis. The

α -TAc permeation (Fig. 15.8) clearly reveals that α

Fig. 15.8. Integrated area ratio map (485 cm − 1 /1004 cm − 1 ) calculated from Raman
spectra acquired from 50 μm × 20 μm areas with step sizes of 4 μminthe x (parallel
to skin surface) direction and 2 μminthe z (axial) direction