A Melanin Derivative to Shield the Skin from High Energy Visible Light

Mar 1, 2011 | Contact Author | By: N. Dayan, PhD, Lipo Chemicals Inc.; A. Ballantyne, T. Ngo, J. Davis, A. Peterson, K. Larsen, J. Gray and H. Knaggs, PhD, Nu Skin Enterprises Inc.; and J. Gallas, PhD, Photo Protective Technologies Inc.
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Title: A Melanin Derivative to Shield the Skin from High Energy Visible Light
fractionated melaninx HEV lightx viscosityx stabilityx aestheticsx
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Keywords: fractionated melanin | HEV light | viscosity | stability | aesthetics

Abstract: High energy visible (HEV) light recently has been suspected of causing as much damage as UVA and UVB combined. Thus, the present paper describes a fractionated melanin tailored to absorb light in the visibile 400–500 nm range. In addition, because the material exhibits color, the authors focus on formulation techniques to incorporate it into semi-solid formulations.

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N Dayan et al, A Melanin Derivative to Shield the Skin from High Energy Visible Light, Cosm & Toil

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While the industry and general public are highly educated about the dangers associated with excessive exposure to sunlight, especially the UVA and UVB wavelengths, findings in recent years reveal that the full spectrum of benefits and harm related to sun exposure are yet to be explored. One of the more striking recent discoveries is that while UVA and UVB are indeed responsible for skin damage, high energy visible (HEV) light, i.e. in the violet and blue range, may cause as much damage as UVA and UVB combined.1–4 However, developing a compound to shield the skin by the selective filtration of violet and blue light presents challenges in molecular design as well as formulation because an effective compound must exhibit color.

UV absorbers in skin care formulas do not impart color because the retina does not respond to the range of photon energies they absorb. However, since HEV absorbers selectively reduce, for example, violet and blue light from the visible spectrum, the eye perceives this as a change in color as the remaining spectrum is expressed; in this case, it appears brown or yellow-brown.

In this paper, the authors present the rationale behind the development of a fractionated melanin (FM) that is tailored to absorb light in the HEV blue to violet wavelength range of 400–500 nm, with minimal absorption in the red range. Since it provides UV as well as HEV photoprotection, it imparts color to formulations. Therefore, the present paper also suggests approaches to cope with the aesthetic challenges this molecule presents when introduced into semi-solid formulations. Overall, this material is presented as a novel means to maximize photoprotection and phototherapy while minimizing its color footprint.

HEV Light and Skin

HEV light is in the blue to violet band, 400–500 nm, of the visible spectrum. The effects of HEV light on macular degeneration have been studied and results suggest it may be a key factor in this age-related disorder.5 The mechanism by which the light damages the lens and retina of the eye is believed to be the generation and accumulation of reactive oxygen species (ROS) that lead to oxidative damage to cells and their organelles. These changes are irreversible and should therefore be minimized as much as possible. In relation to skin, two independent studies were conducted to evaluate the effects of HEV light, which demonstrated photodegradative effects similar to those found in the eye to the epidermal and dermal tissues.

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Table 1. Test Formulas Used for the Described Studies

Table 1. Test Formulas Used for the Described Studies

Since FM showed the ability to absorb radiation in the visible blue/violet range, it was then formulated into a selection of common emulsion, sunscreen, and other cosmetic formulations (see Table 1) and compared with formulas omitting FM in order to explore its physical, chemical or aesthetic effects on each formula type.

Table 2. Accelerated Stability Protocol

Table 2. Accelerated Stability Protocol

Product samples in 2-oz. glass containers of the control and active formulas were then tested by an accelerated stability protocol, as described in Table 2.

Figure 1. Standard vs. fractionated melanin structure

Figure 1. Standard vs. fractionated melanin structure

Further, the melanin was fractionated (see Figure 1) to produce smaller polymers for easier application and to increase HEV filtration while minimizing the perception of darkness.

Figure 2. Spectra for FM vs. standard melanin (normalized at 500 nm)

Figure 2. Spectra for FM vs. standard melanin (normalized at 500 nm)

Figure 2 shows a graphical representation of the performance of FM in the HEV wavelength region, in comparison with standard, full molecular weight melanin.

Figure 3. Light microscopy of three w/o sunscreens and one TiO2 slurry

Figure 3. Light microscopy of three w/o sunscreens and one TiO2 slurry

Figure 3. Light microscopy of a) w/o emulsion sunscreen with inorganic actives (control); b) w/o emulsion sunscreen with inorganic actives with FM; c) w/o emulsion sunscreen with inorganic actives, without TiO2 and with FM; and d) TiO2 in caprylic/ capric triglyceride slurry; all photographs were taken at 1,000x.

Figure 4. Test toner and gel formulas in 2-oz. samples a) without and b) with FM

Figure 4. Test toner and gel formulas in 2-oz. samples a) without and b) with FM

Being a water-soluble compound, FM generated the darkest color in the toner and gel test formulations (see Figure 4).

Figure 5. Approaches to mitigate the color contribution of the FM

Figure 5. Approaches to mitigate the color contribution of the FM

Figure 5. In an attempt to mitigate the color contribution of the FM, three approaches were taken: a) and b) concealing the color in the internal phase of w/o emulsions; and c) adding titanium dioxide to brighten the emulsion; and d) adding FM to a water-in-silicone color foundation to mask the FM color contribution.

Footnotes (CT1103 Dayan)

a The Powershot G3 camera is manufactured by Canon.
b Canfield standardized clinical studio lighting systems are manufactured by Canfield Scientific Inc.
c The Brookfield RVT or LVDV-II+Pro viscometers are manufactured by Brookfield Engineering Laboratories, Inc.
d The SevenGo Pro pH Meter is manufactured by Mettler-Toledo GmbH.
e The DM1000 microscope and DFC420 camera are manufactured by Leica Microsystems CMS GmbH.

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