RAMAN APPLICATIONS IN CANCER STUDIES - Raman Spectroscopy for Soft Matter Applications - page 273

established in a number of studies [13,22,23,25]. We believe that similar
results as shown here will be obtained from measurement on live
patients.

10.5 APPLICATIONS TO SKIN DERMIS

The dermis is responsible for the resilience and elasticity of the skin.
The chemical composition of the dermis (collagen, elastin, hyaluronic
acid, etc.) relates closely to the skin aging process [38 - 41] . Very impor-
tant appendages of the skin, such as hair follicles and sebaceous glands,
are also located at the dermis, the lowest layer of the skin. These
appendages are involved in the development of acne [42,43] . The
in vivo analysis of the dermis is highly important for diagnosing these
skin functions in terms of chemical composition changes.
Although many analytical methods have been developed for inves-
tigating the human skin in vivo , most of these methods are for the
stratum corneum or for the epidermis. For in vivo analysis of the dermis,
many physicochemical methods such as ultrasound imaging, optical
coherence tomography, MRI, near-infrared diffuse refl ectance spec-
troscopy, and so on are used. However, ultrasound imaging and optical
coherence tomography only provide structural information of the
dermis. MRI yields only the distribution image of a limited specifi c
nucleus. Near-infrared diffuse refl ection gives extremely complicated
spectra, and its analytical depth is ambiguous. Although several imaging
techniques, such as confocal fl uorescence imaging, two-photon fl uores-
cence imaging, and second harmonic generation imaging, are attracting
considerable attention as new methods for skin analysis in vivo , they
show only the distribution image of specifi c probe molecules. An
effi cient in vivo analysis method for measuring the dermis is yet to be
developed.
Raman spectroscopy is a promising method for obtaining chemical
information of the dermis in vivo . Recently, confocal Raman micro-
spectroscopy has been shown to be powerful for studying the compo-
nents of the stratum corneum or of the epidermis at a distinct depth
[44-46], but not of the dermis. Due to the shorter excitation wave-
lengths (less than 830 nm), it is not applicable to the dermis because of
the short analytical depth (about 200 m) at these wavelengths.

Thus, 1064-nm near-infrared excited Raman spectroscopy is the most
suitable for analyzing the dermis in vivo [25]. Incident light with a
longer wavelength can penetrate into the dermis of skin owing to low
scattering probability. It is also effective in decreasing the fl uorescence

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