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Photo-Modification of Melanin by a Mid-Infrared Free-Electron Laser
摘要： Melanin is rigidly constructed by several nitrogen-containing aromatic rings, and its excess accumulation in skin tissue is closely associated with melanosis. Although visible lasers (wavelength: 600–1000 nm) are conventionally used for the photo-thermolysis of melanocyte, several pigmented nevi are difficult to be treated. Here, we propose an alternate method for targeting the molecular structure of melanin using an infrared free electron laser (FEL) tuned to 5.8 μm that corresponds to the stretching vibrational mode of carboxylate group. A drastic morphological change on the black-colored surface of melanin powder were observed after the pulse irradiation with a power of 500 mJ/cm2, and the minimum irradiation time for damage to the morphology was 1.4 seconds. Analyses by mass spectroscopy, infrared spectroscopy, and 13C-nuclear magnetic resonance implied that a pyrrole group was removed by the FEL irradiation. In addition, the FEL irradiation dispersed almost all of the melanoma cells from a culture solution without any influence on other ingredients in the medium, and one-cell analysis by infrared microscopy showed that the structure of melanoma could be substantially damaged by the irradiation. This study proposes the potency of intense mid-infrared laser as novel alternative way to reduce melanin.
关键词： Infrared free electron laser,Melanoma,Vibrational mode,Melanin,Photo-modification
更新于2025-11-21 11:03:13
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Melanin-like nanoparticles decorated with an autophagy-inducing peptide for efficient targeted photothermal therapy
摘要： Photothermal therapy efficiently ablates tumors via hyperthermia but inevitably induces serious side effects including thermal damage to normal tissues, inflammations and enhanced risk of tumor metastasis. In this study, we fabricated a dual peptide decorated melanin-like nanoparticle for tumor-targeted and autophagy-promoted photothermal therapy in pursuit of improved cancer treatment. The multifunctional nanoparticle was composed of dual peptide RGD- and beclin 1-modified and PEGylated melanin-like polydopamine nanoparticles. Beclin 1-derived peptide modified on the nanoparticle up-regulated autophagy in cancer cells and further sensitized the photothermal ablation to tumors. RGD decorated on the particle surface enhanced the selectivity and cellular uptake of polydopamine nanoparticles by breast cancer cells. In vivo therapeutic experiments revealed that the tumor-targeted and autophagy promotion-associated photothermal therapy efficiently regressed tumors at a low temperature around 43 oC. The study provides a novel and efficient strategy to improve the efficiency of photothermal therapy via the up-regulation of autophagy in tumor cells.
关键词： photothermal therapy,beclin 1,multifunctional nanoparticles,autophagy,melanin-like
更新于2025-11-19 16:56:35
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Eumelanin for Nature‐Inspired UV‐Absorption Enhancement of Plastics
摘要： In the human body, the black-brown biopigment eumelanin blocks the harmful ultraviolet (UV) radiation. In the plastics industry, additives are often added to polymers to increase their UV-absorption properties. We herein report an assessment of the biopigment eumelanin as a nature-inspired additive for plastics to enhance their UV-absorption. Since eumelanin is produced by natural sources and is non-toxic, it is an interesting candidate in the field of sustainable plastic additives. In this work, eumelanin-including films of commercial ethylene-vinyl acetate copolymer (EVA), a plastic used for packaging applications, were obtained by melt-compounding and compression molding. The biopigment dispersion in the films was improved by means of the Melanin Free Acid treatment (MFA). It was observed that eumelanin amounts as low as 0.8% wt. cause an increase of the UV absorption, up to one order of magnitude in the UVA range. We also evaluated the effect of eumelanin on the thermal and photostability of the films: the biopigment proved to be double-edged, working both as UV-absorption enhancer and photo-prooxidant, as thermogravimetric analysis (TGA) and infrared (IR) spectroscopy revealed.
关键词： Eumelanin,Packaging,Melanin Free Acid,UV-absorbers,Ethylene-vinyl acetate copolymer,UV-aging
更新于2025-10-22 19:40:53
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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Unveiling the Impact of Distinct Melanosome Arrangements on the Attenuation of Cancer-Inducing Ultraviolet Radiation
摘要： The exposure of human skin to ultraviolet radiation (UVR) can trigger a wide array of biological responses, including photocarcinogenesis. Melanin, either in colloidal form or encapsulated into melanosomes, is known to be the main UVR attenuation substance acting within the cutaneous tissues. Although many studies have addressed the protective role of this pigment against the harmful effects of UVR exposure, the impact of different melanosome arrangements on the mitigation of these effects remains to be quantitatively verified. The difficulties to resolve this open question can be mainly attributed to the intrinsic practical limitations of in vivo and in vitro experiments involving skin specimens. In this paper, we describe controlled in silico experiments that allowed us to overcome such limitations and provide quantitative evidence for the clarification of this question. Besides contributing to a more robust understanding of the physiological parameters associated with cutaneous UVR attenuation, our findings can be incorporated into the development of more effective strategies for the evaluation of individuals' susceptibility to UVR exposure. Such strategies are essential for the prevention of UVR-induced pathologies, particularly skin cancer.
关键词： melanosome,sieve and detour effects,ultraviolet radiation,melanin,predictive simulation,skin cancer
更新于2025-09-23 15:23:52
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Laser Treatment for Melanin Gingival Pigmentations: A Comparison Study for 3 Laser Wavelengths 2780, 940, and 445a??nm
摘要： The normal appearance of the gingiva is pink to light red, and this appearance may change due to many factors and might be noticeable causing aesthetic concerns. In the Gulf area, the gingival melanin pigmentation is of the main type of concern, and patients expect the pigmentation to be removed for aesthetic reasons. Many techniques have been used to remove the melanin pigmentation such as using surgical blades, diamond or ceramic burs, chemicals, and lasers. This study is comparing the results of three lasers (Er, Cr, YSGG 2780 nm, Diode 940 nm, and 445 nm) in the removal of melanin gingival depigmentation. Clinical outcome parameters including bleeding, wound healing, pain, duration of procedure, color improvement, patient satisfaction, and relapse rate after 2 years were assessed. Conclusion. Within the limitation of this study, all three wavelengths were fast, e?ective in peeling the pigmentations and well tolerated by the patients. The esthetical results were excellent, and the patients were highly satis?ed. Suggestion. To have a bigger number of samples in future papers, and histological studies might be included to explore the di?erent impacts of each wavelength on the gingival melanin pigmentation speci?cally and on the gingival tissue generally.
关键词： aesthetic dentistry,Cr,445 nm,YSGG 2780 nm,laser treatment,Diode 940 nm,Er,melanin gingival pigmentations
更新于2025-09-23 15:21:01
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Photoacoustic imaging for monitoring periodontal health: A first human study
摘要： The gold-standard periodontal probe is an aging tool that can detect periodontitis and monitor gingival health but is highly error-prone, does not fully characterize the periodontal pocket, and causes pain. Photoacoustic imaging is a noninvasive technique that can address these limitations. Here, a range of ultrasound frequencies between 16-40 MHz were used to image the periodontium and a contrast medium based on cuttlefish ink was used to label the pockets. A 40 MHz ultrasound frequency could spatially resolve the periodontal anatomy, including tooth, gum, gingival margin, and gingival thickness of tooth numbers 7-10 and 22-27. The photoacoustic-ultrasound measurements were more precise (0.01 mm) than those taken with physical probes by a dental hygienist. Furthermore, the full geometry of the pockets could be visualized with relative standard deviations of 10% (n = 5). This study shows the potential for non-invasive monitoring of periodontal health with photoacoustic-ultrasound imaging in the dental clinic.
关键词： periodontal disease,gingival thickness,periodontal charting,Photoacoustic imaging,melanin nanoparticles,diagnosis,pocket depth
更新于2025-09-23 15:21:01
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The influence of morphological distribution of melanin on parameter selection in laser thermotherapy for vascular skin diseases
摘要： Port wine stains (PWSs) are congenital vascular malformations that progressively darken and thicken with age. Currently, laser therapy is the most effective way in clinical management of PWS. It is known that skin pigmentation (melanin content) affects the radiant exposure that can be safely applied to treat PWS. However, the effect of melanin distribution in the epidermis on the maximum safe radiant exposure has not been studied previously. In this study, 10 different morphological distributions of melanin were proposed according to the formation and migration characteristics of melanin, and the two-scale heat transfer model was employed to investigate the influence of melanin distribution on the threshold radiant exposure of epidermis and blood vessels. The results show that melanin distributions do have a strong effect on laser parameter selection. When uniform melanin distribution is assumed, the threshold radiant exposure to damage a typical PWS blood vessel (50 μm diameter) is 8.62 J/cm2 lower than that to injure epidermis. The optimal pulse duration is 1–5 ms for a typical PWS blood vessel of 50 μm when melanin distribution is taken into consideration. PWS blood vessels covered by non-uniformly distributed melanin are more likely to have poor response to laser treatment.
关键词： Port wine stains,Melanin distribution,Two-scale model,Cryogen spray cooling,Laser treatment
更新于2025-09-12 10:27:22
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Photothermal-enhanced synthetic melanin inks for near-infrared imaging
摘要： Synthetic melanin has been increasingly exploited as a new class of functional ink materials due to its promising properties such as ultrahigh reflective index and blackness, and good stability in aqueous solution. Whilst the promising photothermal conversion feature of synthetic melanin has been well devoted, the relatively low near-infrared (NIR) light absorption limited their further application as the NIR imaging inks. Herein, we developed a series of synthetic melanin nanoparticles (SMNPs) inks doped with different kinds of metal ions and found that all the products exhibited enhanced light absorption ability and total photothermal effect compared to the undoped sample. Interestingly, it was also found that these properties could be improved correspondingly with the increase of metal ion concentration. This study not only provides a comprehensive understanding of the metal ion-loaded SMNPs with enhanced photothermal effect, but also paves the way towards fabricating new SMNP inks for NIR imaging applications.
关键词： enhanced photothermal effect,Synthetic melanin,ink
更新于2025-09-11 14:15:04
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Gingival melanin depigmentation by 810 nm diode laser
摘要： The color of gingiva is determined by number and size of blood vessels, thickness of epithelium, keratinization degree, and melanin pigments present in epithelium. Melanocytes, located in basal and suprabasal layers of epithelium, are the cells that produce melanin pigments which play a main role for pigmentation of gingiva. In this case series, the use of 810 nm diode laser for depigmentation of gingiva is presented. Two female patients applied with a chief complaint of “darkened gums” due to heavy smoking. In intraoral examination, diffuse melanin pigmentation was observed in both the maxilla and mandible. Under the local anesthesia, 810 nm diode laser was applied for depigmentation at 1.3 W power in continuous mode. Patients were recalled at weeks 1, 4, and 12 to evaluate the healing and recurrence rate. Both the patients had no postoperative pain or edema, and complete healing was observed at week 12. This study revealed that depigmentation with 810 nm diode laser is successful in terms of esthetics and patient comfort.
关键词： melanin,gingiva,Depigmentation,diode laser
更新于2025-09-11 14:15:04
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Objective determination of skin phototypes in healthy children by diffuse reflectance spectroscopy
摘要： Introduction: The clinical method of evaluating the color of the skin based on visual assessment is subjective and thus inaccurate. The objective determination of skin phototypes and levels of melanin in the skin is important for diagnosing the pigment disorders and also for adequate photoprotection. Diffuse re?ectance spectroscopy (DRS) is a non-invasive, precise and objective method for quantifying the melanin levels. Objective: The aim of this study is to assess the characteristic DRS spectrum of healthy skin in children and to detect the differences between them based on age, gender and skin phototype. Material and methods: Skin pigmentation was measured by DRS in 73 children patients with experimental spectrophotometer UM-ES600. The amount of melanin is quanti?ed from the obtained DRS spectra by proposed melanin quanti?cation angle α obtained by comparing the re?ectance properties of skin sample and universal depigmented sample (albino skin). Results: We evaluated spectroscopic characteristics of children’s healthy skin depending on age, gender and phototype. The value of melanin quanti?cation angle α grew proportionally from phototype I to phototype IV, without any correlation to age or gender. We con?rmed a clear association between clinical determination of Fitzpatrick’s skin phototypes and objective data collected by DRS and related angle α. Conclusions: Our proposed index quanti?es the difference in melanin levels in healthy children skin and also for different skin phototypes. The proposed method and melanin quanti?cation angle α can further be used for the objecti?cation of the progress of pigmentary diseases or for monitoring the effect of their therapy (Tab. 5, Fig. 4, Ref. 29). Text in PDF www.elis.sk.
关键词： melanin quanti?cation angle α,quanti?cation of skin melanin,diffuse re?ectance spectroscopy,skin phototypes
更新于2025-09-10 09:29:36