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Schematic representation of human skin structure. Typical optical penetration depths for specific wavelengths in the UVA and UVB bands.
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It has been demonstrated that ex-vivo human skin autofluorescence is different for healthy and diseased tissue. In order to use these results for in vivo clinical applications, it is necessary to guarantee safe levels of UV radiation during skin scanning of patients and protect the eyes from scattered UV radiation coming from the skin surface. One...
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... and eyes are the organs most exposed to UV radiation, and therefore the most injured. The skin consists of three main layers: the epidermis, dermis and subcutaneous tissues. A representation of human skin, its different layers, and their corresponding thickness are presented in Fig. 2. The epidermis is mainly composed of squamous cells. The innermost layer of the epidermis is made up of a single layer of cuboidal cells, called basal cells. Placed at intervals between basal cells are melanocytes, specialized cells respon- sible for the production of melanin. The outermost layer of the epidermis, the stratum corneum, ...
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Chronic exposure to ultraviolet (UV) radiation causes skin cancer in humans and mice. We have previously shown that in hairless SKH-hr1 mice, UVB-induced p53 mutations arise very early, well before tumor development. In this study, we investigated whether discontinuation of UVB exposure before the onset of skin tumors results in the disappearance o...
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... The outermost layer is called the epidermis, beneath lies the larger dermis, and the deepest layer is the hypodermis (also known as subcutis), as shown in Figure 2. The thickness of the epidermis is between 50 to 150 µm. The outer most layer of the epidermis is called the stratum corneum, which is 8 to 20 µm in thickness and acts as a barrier to almost all macromolecules and hydrophilic drugs [15]- [17]. The second layer, being the dermis, is 1 to 2 mm in thickness and has a rich blood supply, containing microscopic blood vessels. ...
Microneedles are needle-like microscopic structures used to pierce the skin in order to either deliver medical substances, or to extract fluids from a body for sampling purposes. These needles are usually arranged in an array with individual needle lengths ranging from 25 to 2000 μm. Micro-sized needles offer various advantages compared to traditional hypodermic needles, such as a pain free delivery of medical substances. However, manufacturing microneedles represents a real challenge and a mass production process with high volume outputs at low cost is currently lacking.
A promising manufacturing process which fits these criteria is polymer injection moulding. By applying the negative geometry of the microneedles on a mould cavity, millions of polymer microneedle systems can be produced at a low cost. However, within the current state of the art, methods for applying the negative of the microneedles on the injection mould are limited to expensive and time consuming precision techniques. Besides, manufacturing microneedle cavities with a sharp tip has proven to be very difficult with these techniques, while small tip-radii are essential for microneedles to effectively penetrate the skin.
In this thesis, a production methodology for the fabrication of high volume, low cost polymer microneedles was developed. This methodology consists of a laser ablation process to produce cone-shaped microneedle cavities, which are afterwards replicated using injection moulding. First, insights are established in the influence of the laser scanning parameters on the geometry of the ablated microneedle cavities, being the cavity depth, the cavity base diameter and the shape of the needle flank. Next, the effect of various parameters on the replication fidelity and uniformity is investigated, being (i) the geometry of the microcavity, (ii) the location of the microneedles on the macroscopic product, (iii) the polymer characteristics, (iv) the mould material, and (v) the injection moulding technique (conventional injection moulding and injection compression moulding) with corresponding processing parameters. Furthermore, it is demonstrated that numerical flow simulations can be used to accurately predict the replication fidelity, in order to prevent extensive experimental injection moulding experiments.
A valorisation plan is then proposed which includes an identification of the target group that can benefit from the obtained research results, and an estimation on the market size is provided. The position of the developed methodology in the market is presented together with an economical evaluation. From an industrial point of view, the developed methodology is proven to be a suitable mass manufacturing technique to produce high volume, low cost polymer microneedles. Additionally, a key advantage of the methodology is its flexibility, which allows the development of microneedles with different shapes and dimensions in various thermoplastics.
... It penetrates more deeply into the epidermis and reaches the basal layer, which is responsible for the proliferation of epidermal cells. 44 In addition, UVA is responsible for the immediate tanning reaction (immediate pigment darkening reaction); and new melanogenesis, a phenomenon related to the oxidation of melanin present in melanocytes, and consequent increase in the synthesis of melanin 48 hours aer the exposure. 45 It also leads to the formation of direct products of photochemical reactions within DNA 46 and increases the 'network of cytokines induced by UV', which in turn increases the expression of collagenase-1, a metalloproteinase, and loss of interstitial collagen due to photoaging. ...
Despite the challenges in producing plant-derived photoprotective products, novel natural, broad-spectrum sunscreens have gained momentum in the cosmetic industry in the past few years. Traditionally, most of these products have been derived from plants producing polyphenolic and flavonoid compounds. In this study, we focused on plants belonging to the genus Lippia. The study aimed to develop a natural broad-spectrum sunscreen from a Lippia species that could be used as a single UV filter in formulation. Initially, UV transmission of sunscreens (10%, w/w) derived from four different Lippia species was determined to estimate their UVB protection factor (SPF). Next, the extract from species showing the best result was subjected to in vivo SPF and in vitro UVA radiation protection factor (UVAPF) determination using diffuse transmittance spectroscopy. The natural sunscreens obtained in vitro SPF values ranging from 1.7 to 7.6. The higher SPF was obtained with L. sericea species; the in vivo SPF of this sunscreen was 7.5 and its UVAPF was 2.97 when used as a single UV filter in a lotion. The photoprotective activity of this sunscreen was found to be related to the total polyphenolic content of the plant and not to its flavonoid content or antioxidant capacity. Thus, the results of this study suggested that the natural sunscreen from L. sericea has the potential to be used commercially.
... 6 UV radiation (UVR) from the sun is the main trigger of skin cancer, and it can be divided into UVA (315-400 nm), UVB (280-315 nm), and UVC (100-280 nm). Both UVA and UVB are linked to cancer pathogenesis, 7,8 and it is estimated that, at minimum, 10% of all new cancer cases could be prevented if people made proper and continuous use of sunscreens with broad-spectrum protection. 9 The efficacy of sunscreens is dependent on their capacity to absorb radiant energy, and broadspectrum protection requires a combination of UVA and UVB filters. ...
... Thus, upon reaching the basal layers responsible for the proliferation of epidermal cells, it contributes significantly to skin damage. 8 Consequently, it is indeed imperative that sunscreens protect against both UVA and UVB rays. ...
Octocrylene (2-ethylhexyl 2-cyano-3,3-diphenyl-2-propenoate) is present in several sunscreens and is known to work synergistically with UV filters. We prepared eight octocrylene-related compounds to test their photoprotective activities by measuring diffuse transmittance. The compounds had varied photoprotection profiles, with Sun Protection Factors (SPF) ranging from 1 to 5 and UVA Protection Factors (UVAPF) ranging from 1 to 8. Compounds 4, 5, and 7 showed the best protection against UVB sunrays, while compounds 5, 6, and 7 presented the best results for protection from UVA, so compound 7 had the most balanced protection overall. Results for compounds 4, 8, and 9 are reported for the first time in the literature.
... Deste modo, ao atingir as camadas basais, responsáveis pela proliferação das células epidérmicas, contribui significativamente para o dano cutâneo. 8 A Tabela 1 representa a penetração dos raios UV na pele humana. processo de excitação direta dos nucleotídeos, o que leva à formação de fotoprodutos diméricos. ...
Natural extracts (NE) with antioxidant properties can minimize the effects of photoaging. Photobiomodulation (PBM) has proven to be a useful tool for the modulation of cell metabolism. Here, we investigate the associations of antioxidants with PBM with the aim of promoting skin rejuvenation. We began with standardization of the experimental protocol. Extracts of chamomile, rosemary, blueberry, green tea, figs, pomegranate, and nutwood were tested. A custom irradiation system (366 ± 10 nm) was used to simulate sun exposure. A light emitting diode system (640 ± 12.5 nm) was used for PBM. Viability assessments were performed by the MTT assay method. Based on the results, radiant exposure to UVA was defined as 15 J/cm² and 1 J/cm² for PBM. Extract concentrations were established on the basis of dark toxicities, which ranged from 0.01% to 0.3%. The data show that PBM is a promising therapy to restore keratinocytes after UVA damage; however, the detailed mechanism and effects require further exploration. Moreover, although the combination of PBM with NE may be a useful strategy, the choice of a NE is challenging, since the working concentration and other properties, such as photosensitivity, may bring about unwanted results.
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Sunscreens are known to play an important role on the prevention of skin cancer, as they act by blocking the carcinogenic solar radiations. The currently methods for determining the sun protection efficacy of these products are all based on in vivo tests. In this light, the aim of the present study was to compare the performance of two spectrophotometric in vitro methods, in order to determine which one generates more trustworthy Sun Protection Factors (SPF) values: the classical UV spectrophotometry or the diffuse transmittance reflectance spectrophotometry. For that, twenty-five SPF 30 commercial sunscreen samples were used. The methods generated different results, being the diffuse transmittance spectrophotometry more appropriate and reliable for determining the SPF of these products. Moreover, it provides as additional advantage the possibility of quantifying the protection against UVA radiation through the UVA/UVB Ratio and the Critical Wavelength.
Resveratrol is a promising agent for protecting human skin from UV radiation and to reduce the occurrence of cutaneous malignancies. We describe the photoprotective activity of six resveratrol analogues using the diffuse transmittance technique to determine the SPF and the protection against UVA radiation. The analogues presented a varied profile of photoprotection, the SPF ranging from 2 to 10 and the UVAPF from 0 to 9. Among the six compounds tested, the protection against UVB sunrays provided by compound B was more significant than the protection provided by resveratrol; compounds C, D, E and F show photoprotection similar to resveratrol.
Light passing through the atmosphere is scattered and absorbed by the molecules and particles in the atmosphere. This can adversely restrict and limit not only the signal-to-noise ratio (SNR) but also the accuracy and sensitivity of measurements, especially in long-path remote sensing. Usually, in differential absorption lidar (DIAL) techniques, errors are increased mainly because of the different extinction and backscattering properties of the atmosphere at the DIAL probe wavelengths. In this work we have investigated the effects of background aerosol and molecular extinction in DIAL remote sensing in the lower atmosphere for several visibilities at ultraviolet (UV) wavelengths by taking into account the dependence of refraction on the air temperature and pressure. For simplicity, we neglected the spatial inhomogeneity of aerosols in the lower atmosphere. Because of the weak attenuation produced by oxygen and other gaseous atmospheric constituents in this region compared with that from ozone, only ozone is considered as significant among the expected errors. Values for the total attenuation (km−1) at wavelengths 200–400 nm are tabulated for several values of visibility. The acquired results show that the absorption and scattering by the molecules and aerosols vary with wavelength and visibility. The aerosol attenuation in the UV region varies smoothly and thereby errors caused by aerosol scattering can be neglected in remote sensing by UV-DIAL. In addition, aerosols play a very important role in lidar remote sensing in the lower atmosphere by scattering and absorption of radiation, which is considered as a significant factor. At high altitudes, the aerosol concentration is lower than at the ground; the molecular scattering is important, especially for wavelengths greater than 310 nm, where ozone attenuation is not important. The obtained results are important for accurate UV-DIAL measurements of concentration as well as when real-world signals are not available, for example when designing lidar and simulating or when access to real-world signals is not possible.
This study examined the optical properties of an oxidized form of maghemite (γ-Fe(2)O(3)) nanoparticles and their protective effects against the photoaging of human skin fibroblasts irradiated with ultraviolet (UV) light. Nanoparticles with diameters ranging from 8.7 to 12 nm were prepared using a chemical co-precipitation method. The nanoparticles were coated with two surfactants to obtain a water-based product. The onset of the absorption of the γ-Fe(2)O(3) nanoparticles in the UV-visible absorption spectra increased with increasing particle size. The γ-Fe(2)O(3) nanoparticles significantly inhibited the production of matrix metalloproteinase-1 in human skin fibroblast HS 68 cells by 60% compared with the UV-irradiated control. These results suggest that γ-Fe(2)O(3) nanoparticles have photoprotective properties, and have potential use as an agent against photoaging.
