Spectroscopic observations on human pigmentation

Abstract

Background:The main chromophores of human skin are melanins and hemoglobins along with carotenoids, bilirubin, and other compounds. In an effort to study the spectral signatures of skin melanin, we measured absorption spectra in a variety of situations, including a method to show early signs of re-pigmentation in vitiligo. Methods:To measure skin in vivo, the essential component was a "Bifurcated OpticalFiber" with one end connected to the light source and the second end connected to the spectrometer while the common end was placed on the skin. Results:In a typical in situ "melanin in skin" spectrum, the absorbance values first rise gradually, from 750 to 600 nm, then rise moderately from 600 to 450 nm, and rise sharply from 450 nm to a broad peak at 335 nm, below which it gradually rolls down to much lower values. Conclusion:We successfully studied melanin spectroscopically in subjects with vitiligo lesions, obtaining the differential spectra. Higher melanin levels can be shown by steeper negative slopes of a straight line fitted between 620 and 720 nm. Also, absorption peak at 335 nm showed the presence of melanin. K E Y W O R D Smelanin spectra, skin chromophores, spectrophotometry, vitiligo

Innovative technology to eliminate the racial bias in non-invasive, point-of-care (POC) haemoglobin and pulse oximetry measurements

“…likely due to an in the absorption spectra of Hb and melanin. [1][2][3][4][5] Severe anaemia is a major cause of hospital admissions and mortality in the developing world such as sub-Saharan Africa, especially in children. 6 There is a significant unmet need in clinical practice in the region due to unavailability of an inexpensive, easy to use, non-invasive and accurate POC Hb method.…”

“…Hb as well as the skin melanin absorb a portion of the incident light, due to their overlapping absorption spectra in the green (520-580 nm) wavelength range. 4 Green light penetration is limited to approximately 2-3 mm depth from the skin surface. 20 In contrast, red and infrared light used in the available pulse oximeter technology penetrates deeper.…”

“…Blood oxygen saturation (SpO 2 ) measured by pulse oximetry is currently used to monitor tissue hypoxia. However, these non-invasive spectroscopy-based methods are inaccurate in people with darker skin, likely due to an overlap in the absorption spectra of Hb and melanin 1–5…”

“…The investigational device probe emits a narrow beam of green light onto the skin, as further described below. Hb as well as the skin melanin absorb a portion of the incident light, due to their overlapping absorption spectra in the green (520–580 nm) wavelength range 4. Green light penetration is limited to approximately 2–3 mm depth from the skin surface 20.…”

From Melanocytes to Melanoma Cells: Characterization of the Malignant Transformation by Four Distinctly Different Melanin Fluorescence Spectra (Review)

“…A red shift of the fluorescence can be caused by FC-relaxation in the pi-electronic excited states of the oligomers as well as by a “reorganization” of the microenvironment. Since the absorption profiles of the four cell types are identical in the relevant range around 800 nm [ 24 , 25 , 28 , 29 , 30 , 31 , 32 ], the extent of FC relaxation is identical in all four cell types. In conclusion, the increasing redshift of the melanin fluorescence in the process of malignant transformation from normal melanocytes to melanoma cells is caused by changes in the local microenvironment of the melanin in the melanosomes.…”