FT-IR Spectroscopy Study in Early Diagnosis of Skin Cancer

Abstract

Background/aim: Mid-infrared spectroscopy (4000-500 cm^-1) was used to analyze the spectral changes and differences of the characteristic absorption bands of the skin components due to cancer development for early clinical diagnosis.

Materials and methods: Human biopsies from basal cell carcinoma, malignant melanoma, and nevus were used, while normal skin tissue served as a control.

Results: The high quality of Fourier-transform infrared (FT-IR) spectra showed that upon cancer development the intensity of the absorption band at approximately 3062 cm^-1 was increased, indicating that most of the proteins had the configuration of amide B and the β-sheet protein structure predominated. The stretching vibration bands of vCH₂ in the region 2950-2850 cm^-1 were increased in melanoma and nevus, while were less pronounced in basal cell carcinoma due to the increased lipophilic environment. In addition, the intensity of a new band at 1744 cm^-1, which is assigned to aldehyde, was increased in melanoma and nevus and appeared as a shoulder in the spectra of normal skin. The absorption band of amide I at 1650 cm^-1 was split into two bands, at 1650 cm^-1 and 1633 cm^-1, due to the presence of both α-helix and random coil protein conformations for melanoma and nevus. This was confirmed from the amide II band at 1550 cm^-1, which shifted to lower frequencies at 1536 cm^-1 and 1540 cm^-1 for basal cell carcinoma and melanoma, respectively, indicating a damage of the native structure of proteins. The bands at 841 and 815 cm^-1, which are assigned to B-DNA and Z-DNA, respectively, indicated that only the bands of the cancerous Z-DNA form are pronounced in melanoma, while in BCC both the characteristic bands of B-DNA and Z-DNA forms are found.

Conclusion: It is proposed that the bands described above could be used as "diagnostic marker" bands for DNA forms, in the diagnosis of skin cancer.

Keywords: Skin cancer; basal cell carcinoma (BCC); diagnostic bands; infrared spectroscopy; melanoma (MM); nevous (NEV).

Figure 1. FT-IR spectra of skin tissues: normal healthy tissue (N), basal cell carcinoma (BCC), melanoma (MM) and nevus (NEV), in the region 4000-400 cm^–1.

Figure 2. FT-IR spectra of skin tissues: normal healthy tissue (N), basal cell carcinoma (BCC), melanoma (MM) and nevus (NEV), in the region 900-800 cm^–1.

Figure 3. FT-IR spectra of normal skin tissue (N) subtracted from the spectra of melanoma (MM) tissue (MM-N).

Figure 4. Reactions of hyaluronic acid (HA) with hydroxyl free radicals (HO*). The site of HA* radical formation is random and one monomer is shown here, which is denoted by the dashed lines. The final byproducts 5 and 6 are stable and are produced from the free radical 2.

Figure 5. FT-IR spectra of basal cell carcinoma (BCC) subtracted from the spectra of melanoma (MM) tissue (MM-BCC).