Smaller Is Not Always Better: Large-Size Hollow Polydopamine Particles Act as an Efficient Sun Protection Factor Booster for Sunscreens

Abstract

Ultraviolet (UV) radiation from the sun is the most harmful factor for human skin, causing sunburn, melasma, freckles, blemishes, and skin cancer. Sunscreens play a key role in blocking UV absorption on the skin. This study focused on the synthesis of hollow polydopamine (h-PDA), whose structure mimics the naturally occurring melanin in humans, for use as an active ingredient in sunscreens by means of a hard-template-based method. The reactions involve a spontaneous polymerization of a dopamine monomer in the presence of tris­(hydroxymethyl)­aminomethane (Tris) as a catalyst onto a polystyrene (PS) core template. Different sizes of the PS core (about 280 and 450 nm) and weight ratios of PS/DA were applied to elucidate the effect of the hollow diameter and thickness of the shell on the morphology and absorbance of the synthesized h-PDA. From UV absorption results, it was observed that the synthesized h-PDA particles with a larger core diameter (about 450 nm) and a thin shell thickness (about 57 nm) presented high UV absorption. We found that the structure of the synthesized h-PDA is mainly composed of a mixture of 5,6-dihydroxyindole and indole-5,6-quinone precursors covalently linked together. After blending the h-PDA particles with the base cream, the formulation containing h-PDA with a large void diameter of about 450 nm showed the highest sun protection factor (SPF) of up to 7.43, which is related to % booster of 234.7%. In addition, the h-PDA particles exhibited biocompatibility and cellular uptake in keratinocyte HaCaT cells after 24 h of incubation, indicating the potential to mimic natural melanin in preventing UV-induced DNA damage, which could be safely used as an alternative sunscreen.

Polydopamine-Based Nanoparticles for Safe Sunscreen Protection Factor Products with Enhanced Performance

“…C–N and C–O vibrations were found in the ranges of 285.53–285.79 and 286.67–287.22, respectively. The last peak was obtained in the range of 287.92–288.50 eV and was assigned to CO . Furthermore, the shake-up peak of C–N was detected in the range of 290.87–291.97 eV.…”

“…It is known that small particles are easily internalized by cells. In addition, biomimic melanin nanoparticles were proved to be able to uptake into skin cells in our previous study (with the particle sizes of 300–400 nm) and another study (with the particle size of 200 nm) . Therefore, PDA5, our largest particle size (659.1 nm), was chosen to address whether the large particles can be taken up by the skin cells.…”

Biomimetic Chiral Photonic Materials with Tunable Metallic Colorations Prepared from Chiral Melanin-like Nanorods for UV Shielding, Humidity Sensing, and Cosmetics

“…The biocompatibility to skins of both PDA and CNC is well-established. 63,64 In addition, the rod-like morphology could diminish the skin penetration-induced photoallergies and phototoxicity encountered sun screen materials based on organic chemicals or spherical nanoparticles. 65,66 Together with the shiny coloration effects, these properties make the current CNC@PDA-based photonic films very attractive for sun screen coatings, if transparency is not concerned, such as applications in decorative beauty coatings in cosmetics with UV shielding, as will be shown later.…”

“…PDA in the shell of CNC@PDA has many inherent functions. Especially, as the artificial version of the natural melanin widely existing in organs such as human skin that plays the critical role in UV protection, the UV absorption properties of PDA and its applications as the key components for UV blocking have been well established. ,− We therefore tested the UV blocking capability of the above-mentioned chiral photonic CNC@PDA films with brilliant metallic colors. Similar to tuning the color of the CNC@PDA films (Figure ), the thickness of the PDA shell ( T PDA ) again endowed us with the possibility to fine-tune the shielding efficiency (SE) for three ranges of UV light, i.e, UV-C (200–280 nm), UV-B (280–320 nm), and UV-A (320–400 nm) (Figure ).…”

Dual Functional Titanium Hydride Particles for Anti‐Ultraviolet and Anti‐Oxidant Applications

“…At present, sunscreen chemicals such as TiO 2 , LS@TiO 2 , [ 18 ] OL‐S, [ 19 ] Apple polyphenol, [ 19 ] GCO, [ 21 ] Ca‐lignosulfonate, [ 22 ] resvertrol, [ 23 ] LCS@TiO 2 , [ 24 ] Octinoxate, [ 25 ] ZnO@MFCNC, [ 26 ] BC‐OMC‐PDA, [ 27 ] (OMC+BMDM)/EHL, [ 28 ] and MWL‐M, [ 29 ] etc have been mainly used to reflect and scatter UV rays. Among them, TiO 2 shows advantages in the absorption of UV radiation, brightening skin tone, and lack of toxicity.…”