Characterization of Melanin Radicals in Paraffin-embedded Malignant Melanoma and Nevus Pigmentosus Using X-band EPR and EPR Imaging

Abstract

Continuous wave electron paramagnetic resonance (CW EPR) and X-band (9 GHz) EPR imaging (EPRI) were used to nondestructively investigate the possible differentiation between malignant melanoma (MM) and nevus pigmentosus (NP) melanin radicals in paraffin-embedded specimens. The EPR spectra of both samples were analyzed using linewidth, spectral pattern, and X-band EPRI. The CW-EPR spectra of the MM showed an additional signal overlap. Eumelaninand pheomelanin-related radicals were observed in the MM specimens. The EPR results revealed that the peak-to-peak linewidths (ΔHpp) of paraffin-embedded MM and NP samples were 0.65 ± 0.01 and 0.69 ± 0.01 mT, respectively. The g-value was 2.005 for both samples. Moreover, the two-dimensional (2D) EPRI of the MM showed different signal intensities at the different tumor stages, unlike the NP, which displayed fewer variations in signal intensity. Thus, the present results suggest that EPR and 2D EPRI can be useful for characterization of the two melanin radicals in the MM and for determination of their size and concentration.

X-band EPR Spectroscopic Investigation of Seborrheic Keratosis

“…Notably, a paraffin sample containing no tissue was also measured, and no signal was observed. Based on a single line, ΔHpp (0.58), g-value (2.004), and the previous data, 8,10 the radical is the eumelaninrelated radical. In addition, pigmented SK was suggested to contain melanin.…”

“…Thus, non-invasive EPRI can provide detailed information regarding the location and concentration of paramagnetic species in naturally occurring biomedical samples, such as melanin radicals in malignant melanoma (MM). 7,8 Melanin radicals in biomedical samples have been studied using EPR methods in various ways, such as using paraffin-embedded human MM, and human basal cell carcinoma (BCC) specimens. 9 Melanin radicals in MM and nevus pigmentosus (NP) were also compared using EPR.…”

“…Several studies have used this method to investigate free radicals in naturally occurring samples. 3,5,[8][9][10] The application of noninvasive two-dimensional (2D) EPRI and EPR spectroscopy may provide detailed information regarding the location and concentration of paramagnetic species in relation to various disease states. Therefore, further EPR investigation could lead to the development of useful analytical tools for analyzing tumors and non-tumors.…”

Investigation of Paraffin-embedded Basal Cell Carcinoma Using Electron Paramagnetic Resonance

“…The characterization of melanin radicals, such as eumelanin and pheomelanin, in paraffin-embedded samples of MM and nevus pigmentosus (NP) at ambient temperatures have been studied. 9 The two-dimensional (2D) EPRI of MM exhibited varying signal intensities at different tumor stages, unlike the NP, which exhibited fewer variations in the signal intensity. 9,10 However, the distribution and other characteristics of free radicals in paraffin-embedded BCC samples have not yet been investigated.…”

“…We performed characterization of the radical in the paraffin-embedded BCC and compared this with paraffin-embedded MM and NP. 9,10 We also examined the stability of the radical using sepia pigment.…”