Melanin Concentration Research Articles

Comparison of Machine Learning Methods in Stochastic Skin Optical Model Inversion

In this study, we compare six different machine learning methods in the inversion of a stochastic model for light propagation in layered media, and use the inverse models to estimate four parameters of the skin from the simulated data: melanin concentration, hemoglobin volume fraction, and thicknesses of epidermis and dermis. The aim of this study is to determine the best methods for stochastic model inversion in order to improve current methods in skin related cancer diagnostics and in the future develop a non-invasive way to measure the physical parameters of the skin based partially on the results of the study. Of the compared methods, which are convolutional neural network, multi-layer perceptron, lasso, stochastic gradient descent, and linear support vector machine regressors, we find the convolutional neural network to be the most accurate in the inversion task.

LASER SURGERY OF NEVUS OF OTA AND NEVUS OF ITO

Introduction. Clinical variants of congenital melanocytosis in the dermis- nevus of Ota and nevus of Ito (NOI) - may cause marked cosmetic effects; they fail to regress and are reported to be associated with the risk of malignancy. Purpose. To develop criteria and the algorithm for selecting the optimal laser system and radiation specifications to remove NOI considering specific properties of the optical pattern of skin lesions having different locations and melanin concentration. Methods. A scientific and analytical review of publications indexed in PubMed, ScienceDirect, Embase, Web of Science, Russian Medicine, RSCI. Calculation of laser radiation absorption coefficients for various pathomorphological variants of dermal melanocyte locations, given the peculiarities of laser light interaction with targeted photothermophores in NOI focus. Results. The authors present data on epidemiology, history and clinical features of congenital derma melanocytosis of nevus of Ota and nevus of Ito (NOI) - localized, predominantly in periocular and periclavicular regions. Molecular mechanisms of NOI progression in children and adolescents are discussed. There are also data [WU1] on the efficacy and risks of side effects when treating NOI lesions with ruby (wavelength 694 nm), alexandrite ( wavelength 755 nm) and neodymium ( wavelength 1064 nm) laser light. Effectiveness and features of side effects of different wavelengths of laser light are compared. In the article, one can find criteria for selecting an optimal option for NOI laser treatment: maximal efficiency assessed by the visual analogue scale (VAS), number of laser sessions and severity of early and late side effects. For the first time, the authors present data on calculations of quantitative characteristics of optic skin biophotonic pattern if a melanocyte is localized in the papillary and reticular dermis in periocular zone. Conclusion. The obtained calculations on optic characteristics of skin biophotonics suggest [WU2] that two-wave laser irradiation with wavelengths 511 nm and 578 nm will be highly effective with a minimum risk of side effects when removing atypical melanocytes in case of congenital melanocytosis in the papillary and reticular dermis in periocular zone. Algorithms for different pathomorphological variants of melanocyte locatied in the dermis in NOI focus have been proposed to obtain an optimal modality for laser treatment using two-wavelength laser light with 511 nm and 578 nm which is generated by Russian-made copper vapor laser system "Yakhroma-Med" manufactured by Lebedev Physical Institute subordinate to the Russian Academy of Sciences (RAS).

Anti-Melanogenesis Activity of 6-O-Isobutyrylbritannilactone from Inula britannica on B16F10 Melanocytes and In Vivo Zebrafish Models.

A potential natural melanogenesis inhibitor was discovered in the form of a sesquiterpene isolated from the flowers of Inula britannica, specifically 6-O-isobutyrylbritannilactone (IBL). We evaluated the antimelanogenesis effects of IBL on B16F10 melanocytes and zebrafish embryos. As a result, we found that 3-isobutyl-1-methylxanthine (IBMX)-induced melanin production was reduced in a dose-dependent manner in B16F10 cells by IBL. We also analyzed B16F10 cells that were and were not treated with IBMX, investigating the melanin concentration, tyrosinase activity, mRNA levels. We also studied the protein expressions of microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase-related proteins (TRP1, and TRP2). Furthermore, we found that melanin synthesis and tyrosinase expression were also inhibited by IBL through the modulation of the following signaling pathways: ERK, phosphoinositide 3-kinase (PI3K)/AKT, and CREB. In addition, we studied antimelanogenic activity using zebrafish embryos and found that the embryos had significantly reduced pigmentation in the IBL-treated specimens compared to the untreated controls.

Abstract 1568: Effects of melanin on NanoString gene and miRNA expression assays for utilization in biomarker analysis for melanoma

Abstract Purpose Formalin-fixed, paraffin-embedded (FFPE) tumor tissue, while standard for biological preservation, can significantly impact nucleic-acid quality via degradation and cross-linking. The low quality of FFPE-treated samples, coupled with the presence of native small molecules inhibitors in various tissue types, yields significant challenges for PCR-based technologies. Alternatively, NanoString RNA assays combine straightforward workflows with multiplexed detection of up to 800 targets via hybridization-based chemistry that is not reliant on enzymatic processes, and thus may offer advantages in a melanin-rich environment. For utilization in a melanoma disease setting, we evaluated the impact of different melanin-levels in FFPE samples on the performance of NanoString mRNA and miRNA assays Methods One FFPE cell line block was sectioned and spiked with zero or a range of biologically-relevant levels of melanin, both before and after total nucleic acid isolation with the Qiagen AllPrep FFPE procedure. Total RNA content was measured by NanoDrop and fluorescent-based methods. Abundance of individual RNA molecules was assessed by the NanoString IO360 gene expression assay and the NanoString Human v3 miRNA panel. Results Melanin concentration was observed to directly impact quantification results, with higher concentrations correlating to elevated estimates of total RNA yield by NanoDrop, but reduced RNA by fluorescent-based measurement. Different melanin concentrations did not impact RNA expression measurements in the enzyme-free IO360 gene expression assay. For the v3 miRNA assay, however, increased melanin concentration resulted in significant reduction in miRNA signal, but as observed with the IO360 assay, did not affect endogenous mRNA transcript detection. The reduction in miRNA levels was significantly greater for the samples spiked with melanin post-extraction compared with those aliquots spiked prior to isolation. Tumor inflammation signature (TIS) scoring was not impacted by elevated melanin levels. Conclusions NanoString hybridization reactions exhibited minimal sensitivity to melanin content. Conversely, NanoString assays requiring enzymatic processing yielded substantially reduced counts at elevated melanin concentrations. Isolation procedures were effective in removing lower levels of melanin, but could not fully mitigate melanin impact at all tested concentrations. Significantly, classification of tumor immune-environment by NanoString was not affected by melanin, potentially making TIS scoring an attractive tool for biomarker analysis of checkpoint inhibitor therapies in melanoma. Citation Format: Alexis Kurmis, Eileen Kelly, Nancy Valencia, Justin Wahl, Christian Laing, Nathan Riccitelli, Reinhold Pollner. Effects of melanin on NanoString gene and miRNA expression assays for utilization in biomarker analysis for melanoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1568.

Real-time skin chromophore estimation from hyperspectral images using a neural network.

Hyperspectral imaging for in vivo human skin study has shown great potential by providing non-invasive measurement from which information usually invisible to the human eye can be revealed. In particular, maps of skin parameters including oxygen rate, blood volume fraction, and melanin concentration can be estimated from a hyperspectral image by using an optical model and an optimization algorithm. These applications, relying on hyperspectral images acquired with a high-resolution camera especially dedicated to skin measurement, have yielded promising results. However, the data analysis process is relatively expensive in terms of computation cost, with calculation of full-face skin property maps requiring up to 5hours for 3-megapixels hyperspectral images. Such a computation time prevents punctual previewing and quality assessment of the maps immediately after acquisition. To address this issue, we have implemented a neural network that models the optimization-based analysis algorithm. This neural network has been trained on a set of hyperspectral images, acquired from 204 patients and their corresponding skin parameter maps, which were calculated by optimization. The neural network is able to generate skin parameter maps that are visually very faithful to the reference maps much more quickly than the optimization-based algorithm, with computation times as short as 2seconds for a 3-megapixel image representing a full face and 0.5seconds for a 1-megapixel image representing a smaller area of skin. The average deviation calculated on selected areas shows the network's promising generalization ability, even on wide-field full-face images. Currently, the network is adequate for preview purposes, providing relatively accurate results in a few seconds.

CO RELATIVE STUDY OF BHRAJAK PITTA AND MELANIN

Dosa dhatu mala are the basic principles of Ayurveda. In Ayurveda vata,pitta, kapha are the main 3 types of dosa. According to Vagbhata pitta has these main function namely pakti (digestion),ushma(maintain proper body temperature),darshan (vision), kshudha(hunger), trushna(thirst), prabha (lustre) to skin ,medha( intellect). Pathological increase in Pitta causes yellow coloured skin and eyes and decrease in Pitta causes loss of lustre and low glorification (prabhahani). pitta has five subtypes Aalochak ,Ranjak ,Sadhak ,Pachak and Bhrajak pitta . Bhrajak pitta is located in skin and its functions are regulation of body heat and maintain normal skin colour and absorption and digestion of medicine applied on skin. According to modern science the colour of skin depends upon melanin concentration. Excess level of melanin results in skin tanning while absence of melanin causes albinism. Co- relative study of Bhrajak Pitta and melanin may helpful to ayurvedic students to understand ayurvedic concept Bhrajak pitta in modern point of view hence, detail study of Bhrajak pitta and Melanin in has been elaborated in this article.

Practical Measurement and Reconstruction of Spectral Skin Reflectance

AbstractWe present two practical methods for measurement of spectral skin reflectance suited for live subjects, and drive a spectral BSSRDF model with appropriate complexity to match skin appearance in photographs, including human faces. Our primary measurement method employs illuminating a subject with two complementary uniform spectral illumination conditions using a multispectral LED sphere to estimate spatially varying parameters of chromophore concentrations including melanin and hemoglobin concentration, melanin blend‐type fraction, and epidermal hemoglobin fraction. We demonstrate that our proposed complementary measurements enable higher‐quality estimate of chromophores than those obtained using standard broadband illumination, while being suitable for integration with multiview facial capture using regular color cameras. Besides novel optimal measurements under controlled illumination, we also demonstrate how to adapt practical skin patch measurements using a hand‐held dermatological skin measurement device, a Miravex Antera 3D camera, for skin appearance reconstruction and rendering. Furthermore, we introduce a novel approach for parameter estimation given the measurements using neural networks which is significantly faster than a lookup table search and avoids parameter quantization. We demonstrate high quality matches of skin appearance with photographs for a variety of skin types with our proposed practical measurement procedures, including photorealistic spectral reproduction and renderings of facial appearance.

Re-pigmentation of hair after prolonged cholinesterase inhibitor therapy in a Chinese population.

Eighty consecutive Chinese patients diagnosed with Alzheimer disease were assessed for darkening of grey hair. Of the 62 eligible patients (mean age=79.3±7.9years; male: female=1:1.48), 24/62 (38.7%, 95%CI: 26.6 - 51.9) reported hair darkening after prolonged usage of cholinesterase inhibitor for at least 6months. Of the 24 patients with hair darkening, 17 (70.9%) experienced hair darkening in the occipital region, 3 (12.5%) in the parietal region, 2 (8.3%) patients in the frontal region and 2 (8.3%) patients experienced hair darkening in multiple regions. Analysis of melanin concentration showed no significant difference between darkened hair of patients after prolonged drug use and the dark hair of controls (P=0.381).

Characterization of the fluorescence intensity and color tonality in the exoskeleton of scorpions

Scorpions are a mesodiverse and nocturnal group of arachnids inhabiting most biomes worldwide. Different species of scorpions have divergent adaptations to the substrate they live in, but most of them share an intriguing characteristic: their exoskeleton contains fluorophores that emit blue-greenish fluorescence under ultraviolet radiation. Although there are some reports in the literature on the study of fluorescence in scorpions, the biological functionality of this light emission is currently unknown and is under debate. In this work, the properties of emission from the scorpion's exoskeleton are studied by means of digitally processed photographs taken of living specimens under ultraviolet illumination and complemented with standard spectroscopic measurements of emission and excitation spectra. With the aim of identifying possible correlations between the fluorescence, the characteristics color of the exoskeleton and the biology of the scorpions, 4 families, 9 genera and 24 species were studied. Our results suggest that the intensity of fluorescence is heterogeneous throughout the scorpion's exoskeleton studied here in such a way that pedipalps and metasomal segments fluoresce more intensely than the mesosomal segments. The spectrum of fluorescence across species is practically identical, suggesting that the same fluorophores are present in their exoskeletons. However, the fluorescence intensity emitted by each species varies according to their characteristic color (associated with the exoskeleton optical reflectance). Since the coloration of the exoskeleton is determined by the concentration of melanin and other pigments according to the substrate where scorpions live in, we conclude by suggesting that fluorescence may correlate directly to the ecomorphotype of the scorpions.

Inhibitory Effects of Polyphenol-Rich Plant Extracts on Melanogenesis in B16F10 Murine Melanoma Cell Line

Abstract Objectives Polyphenol compounds have been demonstrated to exhibit melanin inhibitory activities in previous studies. We studied 4 extracts of polyphenol-rich plants—rose petal (Rosa centifolia), pomegranate (Punica granatum L.), red orange (Citrus sinensis (L.) Osbeck), and acai berry (Euterpe oleracea Mart.)—for their inhibitory effects on melanogenesis as potential skin whitening agents. Methods Four plant extracts were supplemented into the culture of B16F10 murine melanoma cell line respectively to study their influences on the cell viability using CCK-8 assay and optimal concentrations were determined for the following melanogenesis inhibitory experiments. Thereafter, melanin concentration in the co-cultured B16F10 cells was measured by the NaOH lysis method. Arbutin and kojic acid were used as positive controls. Results Plant extracts showed different effects on cell viability. To achieve cell viability higher than 80%, the concentration of rose and pomegranate extracts should be lower than 1.56 and 3.12 μg/mL, respectively; whereas acai and red orange extracts should be within 50 and 100 μg/mL, respectively. In the range of concentrations adopted in this study, 1.56 μg/mL rose petal extract, 25 μg/mL red orange fruit extract and 25 μg/mL acai berry polyphenol extract showed a melanogenesis inhibitory effect of 33.29%, 29.13%, and 24.09%, respectively, which were greater than that of 50 μg/mL arbutin (10.27%, P < 0.05), but had no difference with 50 μg/mL kojic acid (29.96%). Pomegranate juice powder exhibited a similar inhibitory effect with arbutin, but weaker than kojic acid (P < 0.05). Conclusions Four polyphenol-rich plant extracts were studied for their melanin inhibitory activity in B16F10 melanoma cells in the current study. Red orange fruit extract and acai berry polyphenol extract exhibited stronger inhibitory activity on melanogenesis but milder influence on cell viability compared to the extracts of rose petal and pomegranate, therefore they could be used as potential candidates for developing new skin whitening agents. Funding Sources As a joint project, this research was cofounded by Heilongjiang Feihe Co., Ltd. and Beijing Technology and Business University.

Unravelling the Role of Melanin in Cd and Zn Tolerance and Accumulation of Three Dark Septate Endophytic Species.

Dark septate endophytes (DSEs) are often trace element (TE)-tolerant fungi and are abundant in TE-polluted environments. The production of melanin, a black polymer found in cell walls, was hypothesized by several authors to play a role in the TE tolerance of DSEs. To test this hypothesis, we established a series of experiments using albino strains and melanin inhibitors and examined the responses to Cd and Zn. Six DSEs belonging to genera Cadophora sp., Leptodontidium sp. and Phialophora mustea, were evaluated. The strains mainly produced 1,8-dihydroxynaphthalene (DHN) melanin whereas 3,4-dihydroxyphenylalanin melanin was also synthetized. Cd and Zn decreased melanin synthesis in most of the strains. A reduction in melanin concentration in hyphae through the use of tricyclazole, an inhibitor of DHN-melanin synthesis, did not reduce the tolerance of the strains to Cd and Zn. Similarly, albino mutants of Leptodontidium sp. were not more sensitive to Cd and Zn than the WT strain. Moreover, tricyclazole-treated colonies accumulated less Cd but more Zn compared to untreated colonies. The Cd and Zn contents of Leptodontidium albino strains were variable and similar to that of the WT. The results suggest that melanin production is not an important functional trait that contributes to Cd and Zn tolerance, but might contribute to Cd accumulation.

Imaging human blood cells in vivo with oblique back-illumination capillaroscopy.

We present a non-invasive, label-free method of imaging blood cells flowing through human capillaries in vivo using oblique back-illumination capillaroscopy (OBC). Green light illumination allows simultaneous phase and absorption contrast, enhancing the ability to distinguish red and white blood cells. Single-sided illumination through the objective lens enables 200 Hz imaging with close illumination-detection separation and a simplified setup. Phase contrast is optimized when the illumination axis is offset from the detection axis by approximately 225 µm when imaging ∼80 µm deep in phantoms and human ventral tongue. We demonstrate high-speed imaging of individual red blood cells, white blood cells with sub-cellular detail, and platelets flowing through capillaries and vessels in human tongue. A custom pneumatic cap placed over the objective lens stabilizes the field of view, enabling longitudinal imaging of a single capillary for up to seven minutes. We present high-quality images of blood cells in individuals with Fitzpatrick skin phototypes II, IV, and VI, showing that the technique is robust to high peripheral melanin concentration. The signal quality, speed, simplicity, and robustness of this approach underscores its potential for non-invasive blood cell counting.

Melanin Bleaching and Melanogenesis Inhibition Effects of Pediococcus acidilactici PMC48 Isolated from Korean Perilla Leaf Kimchi.

Overproduction and accumulation of melanin in the skin will darken the skin and cause skin disorders. So far, components that can inhibit tyrosinase, a melanin synthase of melanocytes, have been developed and used as ingredients of cosmetics or pharmaceutical products. However, most of existing substances can only inhibit the biosynthesis of melanin while melanin that is already synthesized and deposited is not directly decomposed. Thus, their effects in decreasing melanin concentration in the skin are weak. To overcome the limitation of existing therapeutic agents, we started to develop a substance that could directly biodegrade melanin. We screened traditional fermented food microorganisms for their abilities to direct biodegrade melanin. As a result, we found that a kimchi-derived Pediococcus acidilactici PMC48 had a direct melanin-degrading effect. This PMC48 strain is a new strain, different from P. acidilactici strains reported so far. It not only directly degrades melanin, but also has tyrosinase-inhibiting effect. It has a direct melanindecomposition effect. It exceeds existing melanin synthesis-inhibiting technology. It is expected to be of high value as a raw material for melanin degradation drugs and cosmetics.

Selective retina therapy monitoring by speckle variance optical coherence tomography for dosimetry control.

.Significance: Selective retina therapy (SRT) selectively targets the retinal pigment epithelium (RPE) and reduces negative side effects by avoiding thermal damages of the adjacent photoreceptors, the neural retina, and the choroid. However, the selection of proper laser energy for the SRT is challenging because of ophthalmoscopically invisible lesions in the RPE and different melanin concentrations among patients or even regions within an eye.Aim: We propose and demonstrate SRT monitoring based on speckle variance optical coherence tomography (svOCT) for dosimetry control.Approach: M-scans, time-resolved sequence of A-scans, of ex vivo bovine retina irradiated by duration laser pulses were obtained by a swept-source OCT. SvOCT images were calculated as interframe intensity variance of the sequence. Spatial and temporal temperature distributions in the retina were numerically calculated in a 2-D retinal model using COMSOL Multiphysics. Microscopic images of treated spots were obtained before and after removing the upper neural retinal layer to assess the damage in both RPE and neural layers.Results: SvOCT images show abrupt speckle variance changes when the retina is irradiated by laser pulses. The svOCT intensities averaged in RPE and photoreceptor layers along the axial direction show sharp peaks corresponding to each laser pulse, and the peak values were proportional to the laser pulse energy. The calculated temperatures in the neural retina layer and RPE were linearly fitted to the svOCT peak values, and the temperature of each lesion was estimated based on the fitting. The estimated temperatures matched well with previously reported results.Conclusion: We found a reliable correlation between the svOCT peak values and the degree of retinal lesion formation, which can be used for selecting proper laser energy during SRT.

Fiber-optic pulseoximeter for local oxygen saturation determination using a Monte Carlo multi-layer model for calibration

Background and objectiveLocal tissue oxygenation determines the relationship between the supply and the demand for oxygen by the tissue and it is an important indicator of the physiological or pathological condition of the tissue. Moreover, some therapeutic methods strongly depend on the oxygen content of the tissue. In photodynamic therapy, when molecular oxygen is present, the irradiation of the photosensitizer with light triggers the generation of reactive oxygen species that kill the target diseased cells within the treated tissue. To ensure the best possible therapy response, the tissue must be well oxygenated; hence, oxygen concentration measurement becomes a decisive factor. In this work, the design, construction and calibration of a module to locally measure the blood oxygen saturation in tissue is presented. MethodsThe system is built using a red (660-nm) and an infrared (940-nm) light emitting diodes as light sources, a photodiode as a detector, and a homemade handheld fiber optic-based reflectance pulse oximetry sensor. In addition, the developed sensor was modeled by means of multilayered Monte Carlo simulations, to study its behavior when used in different thickness and melanin content skin. ResultsFrom the simulation reflectance values, the oxygen saturation calibration curves considering different melanin concentrations and skin thicknesses were obtained for two different skin models, one comprising three skin layers and the second, assuming seven different layers for the skin. A comparison of the performances of the developed pulse oximeter sensor with a commercial one is also presented. ConclusionsA new pulseoximeter for the measurement of local oxygenation in tissue was developed. Its calibration strongly depends on the site of measurement due to the influence of tissue thickness, vascularization, and melanin content. A three-layer skin model is proved to be suitable for the calibration of the pulseoximeter in thin and medium thickness skin.

Multiple behavioral contexts of a melanized tail display in a desert lizard

AbstractConspicuous color displays in animals are often studied in the context of how they communicate an individual's reproductive value, ability to escape capture, or overall health. The study of sexual dichromatism often focuses on the evolution of male display traits balanced between detectability and mate acquisition, representing constraints stemming from both natural and sexual selection. Melanistic coloration and melanin color patterns play important roles in both intraspecific and interspecific signaling in animals; as melanin serves multiple purposes in organismal biology, the evolution of melanin‐based visual displays might not be restricted to a single behavioral or ecological context. Here, we examine the behavioral contexts of the conspicuous melanin‐based tail display in the greater earless lizard (Cophosaurus texanus), asking if this melanized tail pattern is associated with (a) female association preference of males varying in the concentration of melanin, (b) individual locomotor performance capacity, and (c) thermal ecology. We found the amount of tail melanin is linked with both locomotor performance and female association preference, with greater concentrations of melanin predicting the evolution of faster performance capacities and females preferring males with more discrete melanin bars. We found limited support that differences in melanin are linked with thermoregulation or thermal ecology. Overall, we find that multiple behavioral contexts shape the evolution of this melanized display trait. We conclude that behavioral constraints stemming from both natural and sexual selection can interact synergistically to favor the evolution and expression of a melanistic visual display, even in potentially costly ecological contexts.

Comprehensive utilization of edible mushroom Auricularia auricula waste residue-Extraction, physicochemical properties of melanin and its antioxidant activity.

In order to promote the comprehensive utilization of the Auricularia auricula waste residue, the extraction process and the physicochemical properties of melanin from A. auricula waste residue were studied. Furthermore, the chemical antioxidant activity of waste residue melanin and its protective effect on cell oxidative injury induced by H2O2 were investigated. The results indicated that the ultrasonic‐assisted extraction process could be used to extract the melanin from A. auricula waste residue. Melanin had a good solubility in alkali solution and exhibited a certain stability to thermal. There was no significant difference between A. auricula melanin control group and waste residue melanin on ABTS, DPPH, and hydroxyl radical scavenging activity. Waste residue melanin significantly inhibited the cell death caused by H2O2, and the cell viability was restored to 98.09 ± 5.97% when the melanin concentration was 1.6 mg/ml. Cell morphology observation confirmed that the melanin ameliorated the morphological changes of cells induced by oxidative stress.

Estimation of Blood Concentrations in Skin Layers with Different Depths

In this research, we proposed a method to estimate the concentrations of melanin and blood in different layers of skin tissue. Furthermore, we stimulated skin with a warm bath and a carbon dioxide bath and obtained spectral data by a multispectral camera six times during 18 minutes. Based on the captured image, we estimated the blood concentrations in each blood layers by the proposed method. The result showed that the blood concentration of the deep layer is increased only with the stimulation by carbon dioxide bath, and the blood concentration in the shallow layer is increased in both stimuli cases, but the rate of increase in the carbon dioxide bath was higher and the increase time was longer. Our result is consistent with the result of the previous research.

Study on melanin enhanced third harmonic generation in a live cell model.

Melanin dominates the endogenous contrasts of in vivo third harmonic generation (THG) imaging of human skin. A recent study investigated the THG in melanin solution and a linear relationship between melanin concentration and THG intensity was reported, in contrast to the expected nonlinear relationship. Since melanin hydrocolloid solution is very different from the skin tissue, here we report our study on the origin of the melanin-enhanced THG by using a live cell model. Different from the previous conclusion, our live cell study has indicated an initial nonlinear process where the THG intensity was enhanced according to the 3.5th power of melanin mass density (MMD). When the MMD is higher than 11 mg/ml, a transition from the resonance-enhanced THG to the high-order hyper-Rayleigh scattering process occurs. This saturation phenomenon of the virtual-transition-based THG nonlinear process is attributed to the multi-melanosome-induced scattering within the sub-femtoliter focal volume.

Retrieval of Absorption or Scattering Coefficient Spectrum (RASCS) Program: A Tool to Monitor Optical Properties in Real Time.

Optical properties characterize light propagation in turbid media, such as tissue. Recovery of optical properties is of great importance in a wide variety of biomedical applications, including both therapeutic treatments and diagnosis. Most of the available methodologies are well established, however, these are not optimized for real-time measurements. Optical properties are recovered using the Inverse Adding Doubling program from reflectance measurements measured with an integrating sphere and light in the visible range. A user-friendly interface was programmed inVisual Studio and the libraries of aparticular spectrophotometer were used. To achieve real-time measurements, a parallel computing routine was implemented, splitting the whole spectra in threads to be computed independently. Several tests using living tissue and inorganic materials were carried out to validate the proposed algorithm. Recovery of absorption/scattering coefficient spectrum in the visible range with high precision in a couple of seconds was achieved, demonstrating its capabilities for real-time monitoring in biomedical applications. The absorption coefficient spectrum shows the expected characteristics according to the different melanin and blood concentration of various volunteers, also showing the expected changes during a thermoregulation process. A real-time monitoring of optical properties algorithm was developed, including parallel computing and a user-friendly interface. The proposed algorithm would be of help in biomedical applications, where real-time monitoring optical properties is required. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.