How to formulate effective suncare products

Sun protection cosmetics. Oil spray bottle with UV protection and moisturizing lotion tube. Packaging design. Vector illustration. Cosmetics mockup design.

A pleasure for our body and soul. Sun not only stimulates endorphines and serotonin, which generates a general state of psycho-physical wellness, but it also stimulates the production of vitamin D, fundamental for our health. It also spreads anti-oxydants, vaso actives and filtering substances
Solar radiations have positive effects for many skin diseases, such as eczema, dermatitis and acne. However, at the same time, it has been scientifically proved that a skin without an adequate protection from solar rays will suffer from several damages.
The actual knowledges in photodermatology agree on the fact that an adequate photo protection is fundamental not only for prevention of cutaneous flaws due to UV accumulation damages (photoaging), but also for a reduction of the incidence of skin tumors, immunosuppression, and for a control on the dermathological pathologies, photoinduced or photomediated.
In this perspective, and according to individual charateristics, the use of an adequate photoprotection from the solar radiations is necessary, like a real instrument for our health, for the present and the future. An ideal solar product has to be a product agreeable but also innocuous, non toxic, non sensitizing; it has to protect from UVA and UVB rays, from HEV (visible blue and violet light) and from IR-A (infrared rays) in a prolonged and safe way, both in normal and predictable conditions of use. It has to be efficient even when applied in a thin layer; usually the quantity applied on the skin is always lower than the one used to calculate the protection factor. It has to be distributed evenly, and it should grant a certain permanence on the skin, being both sweat and waterproof. Moreover, it has to offer a broad and complete protection, combined with an active photoprotection, and a photo-bio-stimulation, to obtain a stereo-therapic effect (internal-external). Starting from these premises, we realized a really innovative strategy to protect our skin from solar radiations.
This innovative, protective strategy against solar radiations contains a three-phase mechanism:
-First photodefense: blocking the photonic impact
-Active photoprotection: neutralizing the reactive species
-Photobiostimulation: stimulating the mechanisms of endogenous repair

First photodefense: blocking the photonic impact
For many years, research and protection strategies have always focused on the ultraviolet (UVA-UVA) component of the solar light; it has been verified that, due to their high photonic energy, the intense, chronical or unprotected expositions produce various changes in the physiological conditions of our skin. Nowadays, after some recent discoveries, it has been recognized that there are other components of the solar spectrum that can cause harmful effects. IRAs (infrared rays, with band going from 760 and 140 nm) have a lower energetic charge, when compared to UV, but they penetrate in depth and in a bigger quantity (48% of IRA radiations stops to derma, while 17% penentrate in the sub-cutaneous layer), amplifying thus the damages caused by UVR.
IR radiations cause vibrations and molecular rotations that provoke an increase of the temperature.
These energetic alterations can influence the photo-chemical reactions induced by the UV rays, leading to an acceleration of the skin-ageing process, of the carcinogenesis and the immunosuppression. HEV radiations (blue-violet light) generate the 50% of the free radicals induced by solar light, and they stimulate also the production of enzymes, that deteriorate the fibers constituting the derma. Melanin (HEV absorber), in a fractioned form, allows the protection from the HEV band, without screening the red visible light, rich in benefic effects. Melanin is also an efficient scavenger of free radicals: in fact, when it is irradiated, it turns itself in a reactive species, creating stable chemical bonds with the free radicals, in this way neutralizing them, by creating stable bonds with them. From this started our will to research, study and formulate a filtering system, adopting a photonic protection strategy really effective.

Reduction of solar filters quantity
Even though they haven’t the proper characteristics to absorb the UV radiations, some substances can strengthen the filtering power, with a great increase of the protection factor (SPF). They are called SPF boosters and they can function in a double way; they allow the formulation of suncare products with a very high SPF or the formulation of suncare products containing lower concentrations of filters with the same SPF.
Their peculiarity is to scatter the filters in a more stable and efficient way, they guarantee a more even distribution, and the maintenance of a subtle, even layer on the skin.
Our choice for the SPF booster has been Diethylhexyl 2,6 – Naphthalate, that has a double function: on one side, it is a great solvent of organic filters, on the other side it has a high refraction index, to deviate some of the incident radiations. In the composition of our formula there is also a film former containing Hydrolized wheat protein and PVP Crosspolymer; this helped us to increase the SPF, according to a simple principle: an evenly thick layer of product avoids the presence of skin areas partially exposed to UV.

Photostability of chemical filters
Photostability is the ability of a molecule of remaining intact, after it has been irradiated. When a filter is photoexposed, it gets excited. If this filter is photostable, it comes back to its basic status, dissolving the accumulated energy with a 100% performance. If it is not photostable, it undergoes some structural irreversible modifications, causing an alteration of its filtering characteristics, of its protective power and also releasing various degradation photoproducts, whose toxicologic sides are often unknown.
Our scientific research has improved the activity and security profile, by using filters with an active mechanism called Tautomer, in order to make last longer the protective action, and also limiting the filter «consumption».

Percutaneous absorption
This requisite is particularly important, as the UV filters act mainly on the skin surface.
It is necessary that the filter, after its topic application, is held in the outermost layers of the stratum corneum, and that its transdermic absorption is limited.
Different tests, both in vitro and in vivo, showed how some solar filters are absorbed after a topic application – on healthy volunteers – and how they are traceable in urine.
For this aspect, we used the «SOLID LIPID NANOPARTICLES» technology, to reduce the permeations through the skin, so to facilitate its localization in the outermost skin layers; a different approach would try to trap the chemical filters inside some modified clays.
Moreover, the lipidic nano-particles (SLN) with an approximative diametre between 50 and 100nm act like concrete screens, creating light scattering. The main unorganic filter, dioxide titanium, is susceptible to UV rays excitation and, once it has been photo-excited, it can generate a great abundance of free radicals. Other studies suggest that the frequent use of solar products containing nano particles of titanium dioxide may cause percutaneous titanium absorption.
We have successfully evalued a new micro-dispersed, skin-compatible active mineral of the hydroxiapatites: it showed characteristics of the UV spectre covering areas even greater than titanium dioxide. Moreover, thanks to its bio-compatibility with the human body (70% of human bones is made of calcium hydroxiapatite) and skin, will be avoided all the typical intolerance problems that usually occur with micronised solids, because they tend to diffuse themselves in-depth, interfering with the skin metabolism.

Active photoprotection: neutralizing the reactive species
Every molecule has a limited molecular extinction coefficient, so that fraction of photons that can be absorbed by a solar filter will always be lower than 100%. So, not only there is a part of the photons that still reaches our skin, despite UV filters, but the energy of a part of the absorbed photons is also used to generate singlet oxygen.

When solar radiations impact on the skin, they generate free radicals. Free radicals are highly reactive chemical species: they damage DNA and cellular membrane, and they modify proteins and enzymes, but they also increase lipidic peroxidation and they denaturate proteins.
To neutralize these reactive species, antioxidants are fundamental; however, not all of them are effective in the same way, therefore it is necessary to identify the ones with an intense antioxidative power (AP), a short reaction time and a high percutaneous penetration.
Our formula utilizes Dimethylmethoxy Chromanol, Delta-Tocopherol, associated with other Tocopherol isomers, Alpha-Lipoic acid and Bis-Ethylhexyl Hydroxydimethoxy Benzylmalonate (HDBM). Dimethylmethoxy Chromanol is a lipophilic antioxidant, with an excellent AP that works both on ROS and RNS. Scientific studies showed that the most antioxidating form of Tocopherol is Delta Tocopherol and that, with his others isomers, it can develop a synergic effect. HBDM not only has a high AP, but it has also a very peculiar characteristic: once it has completed its free radical scavenger role, it becomes a solar filter; this provokes an increase of SPF under radiation.
It is the ideal completion for the UV filter systems, because its action continues, even after the exposition to sun. Alpha lipoic acid has a double function, as antioxidant and as re-generator of tocopherol isomers. To demonstrate the efficiency of our filtering system, we made the RSF (Radical Status Factor) test on our formula. The results confirm a minimum formation of free radicals in the skin, that are removed at 97%. The un-screened photons can be directly absorbed from proteins and macro-molecules as DNA, and this can cause the proliferation of degenerated cells (in particlular, Keratinocytes and Langherans cells are victims of this phenomenon). A good formulation will aim not only to stimulate the endogenous mechanisms of DNA repair, and to induce the HSP (Heat Shock Protein) synthesis, but also to reactivate the phisiological functions that have been damaged by the aggression (increase of energetic metabolism, restoration of the minimal response).

Photoimmunosuppression and cellular protection
This phenomenon involves the efficiency loss of the immunitary system, due to cutaneous exposition to UVR radiations. Photoimmunosuppression is fight with the addition of the filtering and antioxidating system of a natural substance called ectoine, a photoimmunoprotector that can limit all the damages above metioned, and it also protects Langherans cells.
These cells are fundamental for a good and strong immunitary system, so, granting their presence means improving its efficacy. To obtain this, it is important to reduce sensibly the photodamaged cells, the so-called Sunburnt Cells. Ectoine can also increase the velocity of cellular protection thanks to «heat shock proteins», responsible for protein restoration and their eventual removal, if greatly damaged. The UVA damage to cells will be subjected to stop, also thanks to the inhibition of pro-inflammatory chemical factors that generate cellular damages. It is important to know that DNA damage can happen directly (UVB radiations, the cause the formation of thymine dimers) or indirectly (UVA radiations that cause free radicals).

Photobiostimulation: stimulating endogenous repair mechanisms
Not all light, however, generates unpleasant effects. Previous studies proved how elastine and collagene production can be induced, with a photocycle process called photobiostimulation: it could be defined as the inversion of the UVB damaging effects on elastine and collagene. So, photons emitted with light in the wavelenght from 625 to 660 nanometers can also be an advantage. Therefore this band of the spectrum must remain uncovered («Therapeutical window»). All this translates into the use of a modern filtering system that respects a selective photonic protection strategy. All this can be imagined as a laser cure, intrinsic to a cosmetic product, that can restore the skin architecture.

by Enzo Biraghi, Davide Quaggio, Pietro AbbĂ  – cosmetologists