A new sunscreen made from fish bones? New research shows it’s possible.
Researchers from the Escola Superior de Biotecnologia (Porto, Portugal) have developed a sunscreen filter from cod fish bones, a by-product of the food industry.
The material – a powder – is based on hydroxyapatite (a calcium phosphate) modified with iron and iron oxide, and absorbs in both UVA and UVB ranges.
Potentially, this powder could be used as additive in sun protection creams or embedded in fabrics and clothes.
Ultraviolet (UV) light corresponds to radiation emitted by the sun with a wavelength (l) between 200 and 400 nm. The whole UV interval can be divided into three ranges depending on the l values: UVC (200-290 nm), UVB (290-320 nm) and UVA (320-400 nm).
UVC radiations are mainly blocked by the ozone layer in the upper atmosphere and, therefore, they do not reach the Earth’s surface. UVB and UVA, on the contrary, reach the lower atmosphere. Both UVA and UVB radiations are very dangerous for human health; in fact, they can damage DNA and cause serious illness, such as skin cancer.
UV Protection: Sunscreen
One of the most common ways to get protection from UV light is the use of sunscreens. These are chemical compounds which can absorb the UV radiation, hence preventing this radiation from reaching the skin.
For a sunscreen to be effective, it should absorb over the whole UV range, and it should not be degraded when used under light irradiation. It also has to be inert and non-toxic for human health.
Inorganic Commercial Sunscreens
At present, titanium dioxide (TiO2) and zinc oxide (ZnO) are the most common inorganic sunscreens used in commercial products; they both give protection for the whole UV range. Recently, however, there has been increasing concern about their use, as both compounds have photocatalytic properties. This means that, under light irradiation, they can generate free radicals and/or other reactive species; these could be as dangerous for health as the UV radiations themselves.
Furthermore, their prolonged use is also causing worries for the environment; indeed, increasing concentrations of both compounds have been detected in coastal waters.
Development of New Sunscreen
Because of the reasons described above, the development of new sunscreens has been widely studied in recent years.
In this field, some interesting progress was made by the researchers of Escola Superior Biotecnologia of Portuguese Catholic University (Porto, Portugal). The researchers developed a sunscreen product from the bones of Atlantic cod fish (Gadus morhua); the obtained material is based on hydroxyapatite (HAp, Ca10(PO4)6(OH)2) modified with iron (Fe). The work was done in cooperation with the University of Aveiro (Portugal) and Inovapotek, a Portuguese company studying new developments in cosmetics.
Valorization of By-products
Professor Paula Castro, one of the researchers involved in the project, explains to Decoded Science a little more about this study.
“In Portugal, cod fish is our national dish, we consume it in large quantities; this generates large amounts of by-products, such as the bones of the fish. We thought it could be interesting to valorize these wastes, by extracting high added value compounds.
We know that HAp is the main component of fish bones, as well as of animal and human bones. Unmodified HAp, however, does not absorb in the UV; it is necessary to introduce some additional elements in its structure, for instance Fe, to have UV absorption.”
Treatment with Iron Solution
To introduce the iron, the bones were treated in a solution containing iron chloride (FeCl2); the bones were then dried and successively calcined at 700 oC. In this way, a multiphasic material was obtained, made of HAp, iron oxide (Fe2O3) and a calcium-iron mixed phosphate (Ca9FeH(PO4)7).
This material showed absorption in the whole UV range (UVA and UVB); it had, therefore, the potential to be used as a sunscreen.
The HAP-Fe based material was also tested under light irradiation, to see if any radical species was formed; the results showed no radical detection. Commercial TiO2 and ZnO, on the contrary, when irradiated in the same conditions, formed radical species.
Formulation of a Cream
Considering the encouraging results, the researchers decided to incorporate the powder material into a cream. Professor Manuela Pintado, another researcher involved in the work, gives details about this part.
“We made creams with different amounts of powder added to them; the maximum concentration was 20 % weight – this is the value normally used for other inorganic sunscreens. We tested the UV properties of these emulsions and we saw that they can give a good protection over the whole UV range. Because of this, these creams can be classified as broad spectrum sunscreen.”
As the creams absorb in both UVA and UVB intervals, they can be rated as 5 stars in the Boots UV protection scale; this corresponds to the maximum protection.
Moreover, the cream was tested in healthy volunteers to see if caused any irritation or erythema formation on human skin; results did not show any irritant reactions, indicating that the cream is safe to use.
According to Prof. Pintado: “In this first part of the work, we showed that it is possible to convert fish bones into a product with sunscreen properties. This product is highly biocompatible and safe to use, as it is mainly made of calcium phosphates, compounds which are already present in our body. Now we want to continue and do more studies, to improve the properties of the material. We also want to explore other possible applications, such as the incorporation in fabrics and/or different matrixes.”
Dr. Clara Piccirillo, author of this article, also took part in this research project.
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