Sunscreen compound applied to the human skin give powerful protection against the harmful effect of ultraviolet radiation (UVR) (Diffey, 2005). Overexposure of human skin to ultraviolet radiation (UV) from the sun is major risk factor for sunburn and development of skin cancer. The use of sunscreen has expanded impressively in recent years; and, in the skincare market, sunscreens are right now having the highest level of sales (Hall, 2001, Honey and Krantz, 2007).
Hazardous UV light is divided into three band districts: low-energy UVA (with wavelength of 320–400 nm), high energy UVB (280–320 nm) and UVC (200–280 nm) [1] UVC area is generally consumed by the environmental ozone layer and it is of less burden from a well-being point of view. the different ratio of UVA and UVB depend of the height of the sun, which in turn depend on the season, altitude, time of the day. The biological efficacy is more important than the amount of given wavelength, as a rule, a given ratio of UVB is about 1000 times more erythemogenic than a similar ratio of UVA.
The small amount of UVB sunlight is the main cause of erythema and possibly nonmelanoma skin cancer. Sun protection factor (SPF) is a method of measuring the sunscreen efficacy, its globally accepted index of protection from erythema after exposure to solar-simulated radiation (SSR).
To prevent the harmful effect caused by UV light, different product been developed for the best protection. Mainly, there are two types of UV filters used as active ingredient in the formulation of a sunscreen product. Organic filters can absorb UV radiation of specific wavelength.
On the other hand, we have inorganic filters such as titanium dioxide and zinc oxide that can absorb and scatter UV radiation, thus have a more extensive UV blocking range than the organics. The protection of sunscreen does not depend only on the physiochemical properties of the filter encapsulated, yet it also depends on the method used to deliver them with the optimum protection.
Delivery of the active ingredient using nanoparticles is reported to be beneficial in many dermatological applications. Nanoparticles have been in the center of consideration the past few decades with their exceptional applications in various products. [[6], [7], [8]]. Their small molecule size and the high surface area has converted them to perfect particles in different uses, particularly as inactive ingredient carrier system.
What is nanotechnology & what is ‘Nano-sunscreens’?
The prefix Nano is derived from the Greek word ‘Nanos’ meaning “dwarf” which refers to things of one billionth in size. It was in the mid of twenty century when the proposition of nanotechnology was presented by the scientist Richard Feynman, an American physicist is known as the “Father of Nanotechnology”.
Nanotechnology is the emerging science of investigating the properties and applications of matter on an extremely small scale, ranging from 1 to 100 nm (one billionth of a meter).
The main goals for investigation of nanotechnologies in active ingredient of cosmetic carrier system such as limiting the side effect while maintaining photo-protective qualities.3, biocompatibility, not only cosmetics benefit but there are many biomedical applications in use or under investigation of nanoparticles that cloud change the future of diagnostic or therapeutic techniques, including tissue and organ engineering, implants, drug delivery system.
Nanoparticles have new and uncommon properties that are not clear in the bulk material. Transparency to visible light is one of many characteristics that make Nanoscale inorganic sunscreens so appealing to the developing cosmeceutical industry [6]. Smaller particles of sunscreen, with their higher surface-to-volume ratio and the existence of polar oxygen on their outside, have increased solubility in water-based emulsions, enabling them to be suspended in greaseless, cosmetically satisfying vehicles. Small particles of sunscreen also allow denser packing of this blocking agent between the corneocytes of the upper epidermis and stratum corneum, covering the skin evenly.
Main Concern of nanoparticle utilization:
Because nanotechnology is a relatively young field, there is some concern in its application in sunscreen. The primary concern is the progression of reactive oxygen species (ROS) from metal oxide nanoparticles on exposure to UV radiation. An investigation has shown that ROS could possibly cause a cytotoxic and carcinogenic effect. A few investigations have demonstrated that ROS to be possibly cytotoxic and carcinogenic.5 furthermore, there is contradictory evidence with regard to nanoparticles, due to their small size which allows them to diffuse into the epidermis layer of the skin and be absorbed into the circulatory system, causing a harmful effect in long-term use.2
The aim of the current study was to review the recent literature about the feasibility of using nanoparticles, specifically metal oxide, in sunscreen product. Our main focus was on zinc oxide and titanium dioxide uses in a Nanoscale formulation in sunscreen as a delivery agent and the beneficial effect of metal oxide in small particles size in protection from ultraviolet radiation. Data were collected from an electronic database using keywords such as nanoparticles, cosmetics, sunscreen, ultraviolet radiation and combination of these words.