RESUMO
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 ß-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.
