SUPPORTING INFORMATION Efficient UV Filter Solubilizers Prevent Recrystallization Favoring Accurate and Safe Sun Protection Ivan D. da S. Souza 1, Emma Berkowitz 1, John D. Chea 1, Nicholas McBride 1, Kayla Sweet 1, Daniel Torri 1, Rocco V. Burgo 2, Mariano J. Savelski 1*, Joseph F. Stanzione, III 1*. S1
*Corresponding authors: Email: savelski@rowan.edu (M. J. S.), stanzione@rowan.edu (J. F. S.); Telephone: 856 256-5317 (M. J. S.), 856-256-5356 (J. F. S.); Fax: 856 256-5242. Figure S1. FT- 1 H NMR spectrum of pre-dissolution containing BMDM and DC, highlighting exclusive peaks for BMDM (a) and DC (b) S2
Figure S2. UV-DAD HPLC chromatogram of UV filters analyzed at 315 nm Figure S3. UV-DAD HPLC chromatogram of UV filters analyzed at 355 nm S3
Figure S4. Differential scanning calorimetry curves of opaque gel-cream sunscreen containing ethanol as solubilizer. Method: in a hermetic pan, equalize sample at 20 ºC and ramp up to 95 ºC at 3 ºC/min. S4
Figure S5. Differential scanning calorimetry curves of commercial sunscreen Product G. Method: in a hermetic pan, equalize sample at 25 ºC and ramp up to 135 ºC at 3 ºC/min. As noted on Figures S4 and S5, the reproducibility of the Differential Scanning Calorimetry (DSC) method tested to evaluate crystallization in opaque sunscreen formulations is not satisfactory, and it could not be used for quantification purposes. Melting peaks for pure UV filters were detected, but the complexity of final formulations requires a different approach. Therefore, opaque formulations were analyzed under the light microscope, as presented on Figure S6. First, microscopic images of UV filter crystals produced by supersaturation in ethanol or isopropyl alcohol were captured (Figure S6, A-E). Each crystal has a different shape or nucleation pattern, that is, DHHB, BMDM, and EHT formed distinct and irregular plates, while BP3 and BEMT formed needles. Subsequently, opaque formulations were analyzed to try to identify crystalline structures (Figure S6, F-T). Occasionally, coalescence and S5
other common emulsion instability phenomena were observed, but recrystallization was not noticed. Figure S6. Light microscope images of UV filter crystals and formulations. A to E, captured at 100 X, bar = 100 µm; A- DHHB crystals; B- BMDM crystals; C- BP3 crystals; D- BEMT S6
crystals; E- EHT crystals. F to N, images of opaque gel-cream emulsions distinguished by solubilizer and captured at 400 X, bar = 20 µm; F- ethanol; G- NGD; H- PGD; I- AB; J- DC; K- Blend A; L- Blend B; M- Blend C; N- Blend D. O to T, images of opaque commercial sunscreens captured at 400 X, bar = 20 µm; O- Product D; P- Product E; Q- Product F; R- Product G; S- Product H; T- Product I. Images were adjusted to monochromatic. Images in Figure S6, from F to N, were captured 14 days after manufacture, but no crystals were found even after 3 months at room temperature or in the refrigerator (images not shown). Commercial sunscreens (Figure S6, O-T) were analyzed as soon as received, and they did not present crystalline structures as well, even though some rounded shape material (possibly silica, guessing from their composition see Chart S2) was identified in some cases (see Figure S6, Q and R). In this study, a limited number of formulations was analyzed. The fact that crystalline structures were not identified under light microscope is not conclusive as to whether crystallization will or not happen in these or other formulations. Some authors have S7
reported recrystallization in opaque sunscreens, and we recommend that formulators include recrystallization studies during product development. Figure S7. Scanning electron microscopy images of custom-made formulations applied to artificial skin. All images at 750 X, bar = 100 µm. A-D, clear spray formulations. A- ethanol; B- PGD; C- AB; D- DC. E-H, opaque gel-cream formulations. E- ethanol; F- PGD, S8
G- AB; H- DC. Solubilizers: PGD propylene glycol dibenzoate; AB C12-15 alkyl benzoate; DC dicaprylyl carbonate. S9
Figure S8. Differential scanning calorimetry curves of UV filters applied to artificial skin. Method: in a hermetic pan, equalize sample at 25 ºC and ramp up to 135 ºC at 3 ºC/min. S10
Chart S1. Composition of sunscreen formulations developed for this study. Solubilizer X is each of the following: NGD neopentyl glycol diheptanoate; PGD propylene glycol dibenzoate; AB C12-15 alkyl benzoate; DC dicaprylyl carbonate; Blend A; Blend B; Blend C; Blend D and Ethanol. Clear Spray Sunscreen Ingredients: SD alcohol 40-B (ethanol); glycerin; tetradecane; caprylyl glycol (and) ethylhexylglycerin; sunflower oil; Daucus Carota Sativa (carrot) root extract; fragrance. Also contains Solubilizer X (10 %); ethylhexyl cyano diphenylpropenoate (10 %); diethylamino hydroxybenzoyl hexyl benzoate (9 %); ethylhexyl methoxycinnamate (5 %); ethylhexyl triazone (4 %); benzophenone-3 (2.5 %); bis-ethylhexyloxyphenol methoxyphenyl triazine (2.5 %); butyl methoxydibenzoylmethane (2 %). Opaque Gel-Cream Sunscreen Ingredients: water; glycerin; glyceryl stearate (and) stearamidoethyl diethylamine; caprylyl glycol; Olea Europaea (olive) leaf extract; acrylates/c10-30 alkyl acrylate crosspolymer; xanthan gum; caprylhydroxamic acid. Also contains Solubilizer X (8 %); ethylhexyl cyano diphenylpropenoate (10 %); diethylamino hydroxybenzoyl hexyl benzoate (9 %); ethylhexyl methoxycinnamate (5 %); ethylhexyl triazone (4 %); benzophenone-3 (2.5 %); bis-ethylhexyloxyphenol methoxyphenyl triazine (2.5 %); butyl methoxydibenzoylmethane (2 %). S11
Chart S2. Composition of commercial sunscreens Product A clear, SPF 20, UVA/UVB protection Ingredients: alcohol denat.; C12-15 alkyl benzoate; PPG-15 stearyl ether; acrylates/octylacrylamide copolymer; hydroxypropyl cellulose. Also contains unknown amounts of homosalate; diethylamino hydroxybenzoyl hexyl benzoate; ethylhexyl cyano diphenylpropenoate and butyl methoxydibenzoylmethane. Product B clear, SPF 30, UVA/UVB protection Ingredients: alcohol denat.; acrylates/octylacrylamide copolymer; dimethicone; trisiloxane; tocopheryl acetate; fragrance. Also contains homosalate (8.0 %); benzophenone-3 (5.0 %); octisalate (4.0 %); butyl methoxydibenzoylmethane (3.0 %) and ethylhexyl cyano diphenylpropenoate (2.0 %). Product C clear, SPF 85, UVA/UVB protection Ingredients: SD alcohol 40-B; cyclopentasiloxane; cyclohexasiloxane; C12-15 alkyl lactate; trimethylolpropane tricaprylate/tricaprate; dicaprylyl carbonate; acrylates/octylacrylamide copolymer; caprylyl glycol; dimethyl capramide; Aloe barbadensis leaf extract; retinyl palmitate; tocopherol; fragrance. Also contains homosalate (15 %); ethylhexyl cyano diphenylpropenoate (10 %); benzophenone-3 (6 %) and butyl methoxydibenzoylmethane (3 %). Product D opaque, SPF 15, UVA/UVB protection Ingredients: water; ethylhexyl benzoate; cetearyl alcohol; neopentyl glycol diheptanoate; VP/eicosene copolymer; phenetyl benzoate; dimethicone; glycerin; polymethylsilsesquioxane; triethanolamine; cocoglucoside; acrylates/c10-30 alkyl acrylate crosspolymer; caprylyl glycol; ceteth-10 phosphate; dicetyl phosphate; disodium EDTA; paraffin; xanthan gum; Butyrospermum parkii (shea) butter; sodium ascorbyl phosphate; tocopheryl acetate; panthenol; Aloe barbadensis leaf juice; Carica papaya (papaya) fruit extract; Colocasia antiquorum root extract; Mangifera indica (mango) fruit extract; Passiflora incarnata fruit extract; Plumeria acutifolia flower extract; Psidium guajava fruit extract; phenoxyethanol; methylparaben; propylparaben; fragrance. Also contains: ethylhexyl cyano diphenylpropenoate (3 %); benzophenone-3 (2 %) and butyl methoxydibenzoylmethane (2 %). Product E opaque, SPF 30, UVA/UVB protection Ingredients: water; ethylhexyl benzoate; butyloctyl salicylate; cetearyl alcohol; neopentyl glycol diheptanoate; phenetyl benzoate; polymethylsilsesquioxane; VP/eicosene copolymer; caprylyl glycol; dimethicone; glycerin; triethanolamine; coco-glucoside; acrylates/c10-30 alkyl acrylate crosspolymer; ceteth-10 phosphate; dicetyl phosphate; disodium EDTA; paraffin; xanthan gum; Butyrospermum parkii S12
(shea) butter; Mangifera indica (mango) seed butter; sodium ascorbyl phosphate; tocopheryl acetate; panthenol; Aloe barbadensis leaf juice; Carica papaya (papaya) fruit extract; Colocasia antiquorum root extract; Mangifera indica (mango) fruit extract; Passiflora incarnata fruit extract; Plumeria acutifolia flower extract; Psidium guajava fruit extract; phenoxyethanol; methylparaben; propylparaben; fragrance. Also contains ethylhexyl cyano diphenylpropenoate (5 %); benzophenone-3 (3 %) and butyl methoxydibenzoylmethane (2 %). Product F opaque, SPF 50, UVA/UVB protection Ingredients: acrylates/c12-22 alkyl methacrylate copolymer; acrylates/dimethicone copolymer; ammonium acryloyldimethyl-taurate/vp copolymer; ammonium hydroxide; behenyl alcohol; butylene glycol; butyloctyl salicylate; caprylyl glycol; cetearyl alcohol; ceteth-20 phosphate; cyclamen aldehyde; dicetyl phosphate; dimethicone; disodium EDTA; ethyl linalool; ethylene brassylate; ethylhexyl methoxycrylene; Euterpe oleracea fruit extract; glycerin; isobutyl methyl tetrahydropyranol; methyl trimethicone; methylenedioxyphenyl methylpropanal; pentylene glycol; phenoxyethanol; phenylisohexanol; propylene glycol; silica; sorbic acid; styrene/acrylates copolymer; tocopheryl acetate; triethanolamine; trimethylsiloxy-silicate; VP/eicosene copolymer; water; xantham gum. Also contains homosalate (10 %); ethylhexyl cyano diphenylpropenoate (5.5 %); benzophenone-3 (5 %); octisalate (4.5 %) and butyl methoxydibenzoylmethane (3 %). (continued) Chart S2. Composition of commercial sunscreens (conclusion) Product G opaque, SPF 50, UVA/UVB protection Ingredients: water; cyclopentasiloxane; alcohol denat.; silica; dicaprylyl ether; styrene/acrylates copolymer; PEG-30 dipolyhydroxystearate; dimethicone; cyclohexasiloxane; polymethylsilsesquioxane; nylon-12; caprylyl glycol; dicaprylyl carbonate; disodium EDTA; disteardimonium hectorite; dodecene; isostearyl alcohol; lauryl PEG/PPG-18/18-methicone; methylparaben; PEG-8 laurate; phenoxyethanol; poloxamer 407; poly C10-30 alkyl acrylate; sodium chloride; tocopherol; Vitis vinifera (grape) fruit extract. Also contains homosalate (10%); benzophenone- 3 (6 %); ethylhexyl cyano diphenylpropenoate (5 %); octisalate (5 %) and butyl methoxydibenzoylmethane (3 %). Product H opaque, SPF 50+, UVA/UVB protection S13
Ingredients: acrylates copolymer; butyloctyl salicylate; Butyrospermum parkii (shea) butter; C12-15 alkyl benzoate; Cocos nucifera (coconut) oil; disodium EDTA; ethylhexylglycerin; fragrance; glycerin; glyceryl stearate; hydrogenated palm glycerides; PEG-100 stearate; pentylene glycol; phenoxyethanol; potassium cetyl phosphate; styrene/acrylates copolymer; Theobroma cacao (cocoa) extract; Theobroma cacao (cocoa) seed butter; tocopheryl acetate; VP/eicosene copolymer; water; xanthan gum. Also contains homosalate (15 %); benzophenone-3 (6 %); octisalate (5 %); ethylhexyl cyano diphenylpropenoate (2.75 %); and butyl methoxydibenzoylmethane (3 %). Product I opaque, SPF 50+, UVA/UVB protection Ingredients: water; C12-15 alkyl benzoate; butyloctyl salicylate; butylene glycol; dipropylene glycol dibenzoate; polyester-7; dimethicone; neopentyl glycol diheptanoate; Aloe barbadensis leaf juice; mannitol; glycerin; PPG-15 stearyl ether benzoate; phenoxyethanol; lauryl glucoside; fragrance; polyglyceryl-2 dipolyhydroxystearate; potassium cetyl phosphate; ammonium acryloyldimethyltaurate/vp copolymer; dimethiconol; disodium EDTA; ethylhexylglycerin; tocopheryl acetate; tocopherol; cyclodextrin; dehydroacetic acid; Pisum sativum (pea) extract; tromethamine; Cassia alata leaf extract; yeast extract; citric acid; dextrin; hydrolyzed Adansonia digitata extract; Helianthus annuus (sunflower) seed oil; Olea europaea (olive) leaf extract; Platanus occidentalis (bark) extract; potassium sorbate; sodium benzoate; benzyl salicylate; limonene; butylphenyl methylpropional; hexyl cinnamal; citronellol. Also contains homosalate (10 %); benzophenone-3 (6 %); octisalate (5 %); ethylhexyl cyano diphenylpropenoate (2.7 %); and butyl methoxydibenzoylmethane (3 %). S14
Table S1. UV-Vis spectrometric quantification of UV filters. DHHB diethylamino hydroxybenzoyl hexyl benzoate; BMDM butyl methoxydibenzoylmethane; BP3 benzophenone-3; BEMT bis-ethylhexyloxyphenol methoxyphenyl triazine; EHT ethylhexyl triazone. UV filter Wavelengt h (nm) slope y- intercept Linearity r 2 range (µg/g) DHHB 354.6 11.772-0.7836 0.99999 0.25-25.00 BMDM 359.9 10.526-0.5281 0.99999 0.25-25.00 BP3 286.5 18.694-2.617 0.99999 0.25-25.00 BEMT 337.1 12.948-0.7044 0.99999 0.25-25.00 EHT 304.2 9.3181-1.5907 0.99704 0.25-25.00 S15
Table S2. UV-DAD chromatographic quantification of UV filters. BP3 benzophenone- 3; DHHB diethylamino hydroxybenzoyl hexyl benzoate; EHCDP ethylhexyl cyano diphenylpropenoate; EHMC ethylhexyl methoxycinnamate; BMDM butyl methoxydibenzoylmethane; EHT ethylhexyl triazone; BEMT bis-ethylhexyloxyphenol methoxyphenyl triazine. UV filter Wavelengt h (nm) Retention time (min) slope y- intercept Linearity r 2 range (µg/ml) BP3 315 3.40 [3.39;3.41] 15.598 1.4584 0.99322 1.43-42.94 S16
DHHB 355 3.97 [3.96;3.98] 33.184 11.453 0.99178 1.41-42.70 EHCDP 315 5.12 [5.10;5.14] 14.021 13.644 0.98269 1.43-43.10 EHMC 315 6.03 [6.01;6.05] 43.608-39.248 0.99857 1.43-42.90 BMDM 355 6.59 [6.57;6.62] 28.497-1.2853 0.99741 1.41-42.80 EHT 315 10.90 [10.89;10.91] 47.875 23.091 0.98906 1.41-42.80 BEMT 355 12.68 [12.67;12.69] 11.853 2.5696 0.99194 1.42-42.50 S17
Table S3. Hansen Solubility Parameters of UV filters and solubilizers. δ D atomic dispersion forces (non-polar interactions); δ P dipole-dipole interactions (polarity); δ H hydrogen bonding; δ total total Hansen Solubility Parameter. DHHB diethylamino hydroxybenzoyl hexyl benzoate; BMDM butyl methoxydibenzoylmethane; BP3 benzophenone-3; BEMT bis-ethylhexyloxyphenol methoxyphenyl triazine; EHT ethylhexyl triazone; EHCDP ethylhexyl cyano diphenylpropenoate; EHMC ethylhexyl methoxycinnamate. NGD neopentyl glycol diheptanoate; PGD propylene glycol dibenzoate; AB C12-15 alkyl benzoate; DC dicaprylyl carbonate. Chemicals δ D (MPa 1/2 ) δ P (MPa 1/2 ) δ H (MPa 1/2 ) δ total (MPa 1/2 ) DHHB 18.7 8.9 9.7 22.9 BMDM 18.1 5.2 0.0 18.8 BP3 20.5 6.8 11.9 24.7 BEMT 18.9 10.5 10.3 23.9 EHT 19.1 5.1 6.1 20.7 EHCDP 19.6 5.7 3.9 20.8 EHMC 17.7 5.0 5.2 19.1 Ethanol 15.8 8.8 19.4 26.5 S18
NGD 13.6 3.9 5.5 15.2 PGD 20.1 9.9 6.9 23.4 AB 17.8 5.3 2.6 18.8 DC 17.1 0.8 3.8 17.6 Blend A 15.2 5.4 5.8 17.2 Blend B 16.4 6.0 5.8 18.4 Blend C 15.2 5.8 6.3 17.5 Blend D 14.0 5.5 6.7 16.5 Table S4. Recrystallization in commercial clear spray sunscreens after sonication and cooling procedure. BMDM butyl methoxydibenzoylmethane; BP3 benzophenone-3; EHCDP ethylhexyl cyano diphenylpropenoate. Averages are not significantly different than time zero (P > 0.05). Sample % Recrystallization BMDM BP3 EHCDP Product B -1.65 [-10.43; 7.12] -0.89 [-3.30; 1.52] -0.37 [-5.35; 4.61] Product C -1.03 [-9.95; 7.89] 2.06 [-2.75; 6.87] -2.96 [-7.04; 1.11] S19