UV protection By Kidirbayeva Assem
What is the UV? Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than Xrays, that is, in the range between 400 nm and 10 nm, corresponding to photon energies from 3 e. V to 124 e. V. It is sonamed because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet. These frequencies are invisible to most humans except those with Aphakia. Near UV is visible to a number of insects and birds. Wavelength: Visible light (400 nm) > UV > X-rays (10 nm)Photon energies: 3 e. V (electron volt) to 124 e. VEmitted by: Sun, electric arcs, mercury lamps and black lights
Affects of UV on our skin Sunscreen has been the major combatant of skin cancer by protection against ultraviolet radiation (UV). Sunscreen formulations have adapted and improved to become protective over a broader spectrum of lightand maintain greater photostability. Sunscreens are comprised of organic and inorganicnanoparticles which act as chemical an physical UV protectors, respectively. Sunscreen components are limited by their spectrum of protection, photostability or often a combination of both. Recent studies using solid lipid nanoparticles (SLN), new organic molecules, inorganicsand antioxidants attempt to optimize UV protection.
Nanoparticles are at the heart of UV protection. They have a significant increase in their effectiveness of blocking UV light compared to natural material due to their large surface area to volume ratio. Figure 3 illustrates this effect: Incoming UV radiation is unblocked and penetrates the stratum conium. (B) An UV reflective material in bulk form (ex. Zn. O) is applied to the surface of the stratum corneum. Some incoming UV radiation is blocked by reflection/scattering and some UV radiation is unblocked/deflected to the stratum corneum. (C) UV reflective nanoparticles (ex. Zn. O) are appliedto the surface of the stratum corneum. The incoming UV radiation is reflected by the nanoparticles. This review will cover the use of organic and inorganic nanoparticle components in sunscreen and the use of solid lipid nanoparticles in UV protection. This review also touches upon the use of these particles in novel UV protection applications.
Inorganic nanoparticle components Titanium dioxide is a mineral which is prepared as ultra-fine nanoparticles with a diameter on the order of 14 nm. These particles form aggregates which reflect UVlight most efficiently with aggregates sized at 60 -120 nm. In sunscreens, Ti. O 2 is usually treated with coating materials such as silicon oils, Si. O 2, or Al 2 O 3 in order to make it more passive in relation to the organic components and improve its dispersion in the overall formulation. Additionally, Ti. O 2 nanoparticles can be coated with silica to increase UV absorption. Zinc Oxide Zinc oxide (Zn. O) is a mineral and prepared in particles that have an optimal size of 20 -30 nm [13]. Zn. O is also usually coated with silicon oils, Si. O 2, or Al 2 O 3 in sunscreen formulations. Additionally, Zn. O is considered a better sunscreen ingredient than Ti. O 2 because it is more transparent for a given concentration and is more protective against UVA light.
Advantages/disadvantages of inorganics Inorganics used in sunscreen are beneficial because they have been shown to reflect and scatter UV light, which is gnerally considered safer and more effective than absorption of UV light. Inorganics cover a broad spectrum, so their addition can simplify the sunscreen formulation by minimizing the necessary number of organic components. This can be beneficial for those with sensitivity or skin irritation issues [15]. Inorganic UV sunscreens have relatively high consumer acceptance because of their transparency, which increases the usage of sunscreen [7]. A drawback of using inorganics is their dispersion issues, which often require an additional material for coating the inorganic material [10]. The most considerable drawback is the potential risk caused by the generation of free radicals through oxidation when exposing inorganic molecules to UV radiation
Organic nanoparticle components Avobenzone Butyl methoxydibenzoylmethane(BMDM), more commonly known as avobenzone, is an oil soluble product used to absorb the full spectrum of UVA rays. It is considered one of the best sunscreen agents because of its ability to absorb UV light over a very broad spectrum. Since, avobenzone is highly degradable in the presence of sunlight it is often paired with a photo stabilizer in sunscreen formulations. Oxybenzone is also used in sunscreen formulations because of its ability to absorb UVA light. It is considered potentially harmful and a likely photocarcinogen because of its ability to penetrate through the stratum corneum and generate free radicals when illuminated with UV light. Oxybenzone is a derivative of benzophenone, a known photocarcinogen. Phenylbenzimidazole, Octyl methoxycinnamate, Octyl salicylate.
Advantages/disadvantages of organics Organic components used in sunscreen formulations are fairly abundant and diverse in comparison to inorganic. This gives manufactures flexibility with characteristics of the formulation such as the sun protection factor (SPF), water resistance, and product feel. Organic components could be considered less effective because they absorb UV radiation rather than reflecting or causing it to scatter. This makes them vulnerable to photodegradation and prone to generating ROS. However, the main concern and greatest risk with using organics is the threat of carcinogens or generating carcinogens in the presence of UV light.
Technology Solvothermal synthesis is a method of producing chemical compounds. It is very similar to the hydrothermal route. Using the solvothermal route gains one the benefits of both the sol-gelx and hydrothermal routes. Solvothermal synthesis has been used in laboratory to make nanostructured titaniudioxide, graphene, carbon and other materials. The high photocatalytic capacity of Ti. O 2 leads to the degradation of organic and biological molecules into smaller and less harmful compounds. Schematic diagram of solvothermal synthesis setup: (1) stainless steel autoclave (2) precursor solution (3) Teflon liner (4) stainless steel lid (5) spring
Properties and usage Used in creams, lotions to protect against sunburn and other damage to the skin caused by UV light. Completely photostable when used as an ingredient in sunscreen, sits on the skin’s surface and is not absorbed into the skin so, zinc oxide and titanium dioxide, are nonallergenic. It is found in almost every sunscreen with a physical blocker because of its high refractive index, its strong UV light absorbing capabilities, and its resistance to discolouration under ultraviolet light.
