TRENDING TECHNOLOGIES
protecting the skin microbiome etc. Mintel research also highlights that brands
can add value and stem competition from facial care products with SPF by promoting multi- protection benefits and aligning them with wellbeing trends.12
Biomimetic hydroxyapatite: a bio- compatible mineral Hydroxyapatite (HAP) is a mineral occurring in nature based on calcium, phosphate and hydroxyls, with the following stoichiometric composition: Ca10
(PO4 )6 OH2 . Hydroxyapatite forms also physiologically
occur in human tooth and bone: in contrast to stoichiometric HAP, the bone and tooth mineral is structurally disordered, and compositionally nonstoichiometric due to the presence of a substantial amount of anionic (e.g., HPO42 2− ,Cl−) and cationic (e.g., Na+, Mg2
−, CO3 +)
species, together with the presence of ion vacancies into the crystal lattice.16
Such variants
fall in the ‘physiological HAP’ category. Physiological HAP is the main mineral of
dental enamel and dentin; 70% of human bone is made of it. Fishbone is also mainly composed of HAP. In light of its physiological nature, physiological HAP can be synthetized to obtain the ‘biomimetic HAP’ mineral. Such a mineral has multiple applications as biocompatible material:3,17
it is used as coating to promote
bone ingrowth into prosthetic implants,18,19 in aesthetic medicine to fill wrinkles and homogenize skin texture, while in oral care it is used to promote tooth remineralization, anti- plaque and anti-caries activities.20 It is also considered to be an anti-ageing
active since it is a source of calcium and phosphate ions for epidermal cells and its mineral surface has been proven to subtract sebum unsaturated fatty acids otherwise exposed to UV rays and converted in lipid peroxides.21
a pharmaceutical carrier.22
Mineral SPF booster with no skin whitening effect and light texture Apalight biomimetic hydroxyapatite is a
1.80 1.60 1.40 1.20 1.00
0.80 0.60 0.40 0.20 0.00
290 300 310 320 330 340 350 360 370 380 390 400 410 420 430 440 450 Wavelenght/nm
Figure 2: Biomimetic hydroxyapatite @ 22% a.m. based formula: absorbance value before and after irradiation
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Figure 1: Whitening effect: comparison between micron-sized titanium dioxide and Apalight, both used @ 6%
Furthermore, it can also be used as
natural-like mineral with porous and rough surface, with ‘acidic pH-dependent’ solubility. Its mineral nature and specific refraction index (n=1.6) make it ideal as booster in sunscreen application as replacement of inorganic filters in hybrid formulations containing organic filters,23 it can also be combined to inorganic filters in mineral sunscreens. Given its little bit lower refraction index than titanium dioxide and zinc oxide, its presence in formula enables to keep an effective screening action against UV-rays, while avoiding the typical blue whitening effect and heavy texture associated to the previously mentioned inorganic filters (Figure 1). Furthermore, the physiological presence of
hydroxyapatite in the fishbone composition is a key element to consider in the evaluation of the use of synthetic biomimetic hydroxyapatite for sunscreen products, especially in the optics of development of sunscreens containing
ADO ■ ADx ■
ADO: Absorbance Before Irradiation ADx: Absorbance After Irradiation
ingredients similar to components expressed in the sea eco-system. In addition to its sustainable nature, biomimetic hydroxyapatite use is approved in natural eco-certified cosmetics and its powdery form boasts values of 100% naturalness, with a natural index score of 1.
Absorbance and photostability In accordance to the ISO24443:2012 standard, the UV absorbance curve and the critical wavelength of a cosmetics formulation containing 22% of biomimetic hydroxyapatite was assessed in absence of registered sunscreen filters and SPF/UV-A protection booster to evaluate the contribution of HAP itself in terms of UV absorbance. The test enables to identify the absorbance
curves of a thin film of product spread over a rough substrate, before and after exposure to a controlled dose of UV radiation from a solar simulator and determine the photo-stability. The resulting spectral absorbance provides a representation of both the width and the height of its UV-protection characteristics. According to the above-mentioned
methodology, the biomimetic HAP-based formulation showed overlapping absorbance spectra before and after irradiation, with a critical wavelength of 384 nm. The results suggest therefore that HAP shows maximum photo-stability after exposure to UV radiation (Figure 2).
In vivo SPF test & in vitro UVA-PF: mineral sunscreen formula A base formulation containing biomimetic HAP active matter at 25% and zinc oxide at 4%, developed in cold process and using exclusively eco-certified raw materials (Table 1) was tested through a preliminary SPF in vivo test carried out on three subjects (phototype II and III, average skin tone ITA° 68), according to the Protocol of COLIPA International Sun Protection Factor Test Method, May 2006.
June 2022 PERSONAL CARE
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Absorbance
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