Hybrid PMMA Bead Containing Chemical Sunscreen Filters

Transcription

1 Hybrid PMMA Bead Containing Chemical Sunscreen Filters Sung-HO Lee, Jeonghwan Kim, Jangho Park, Sangwook Kim, Jinkwan Park, Sookyung Kim, Sooyoung Lee, Byungcheol Lee SUNJIN Chemical Co. LTD, Korea Keywords: Avobenzone, UV protection, Hybrid, Photo-stabilization, PMMA, Introduction The task of photo-stabilization avobenzone has been a great focus of sunscreen formulators worldwide. Moreover, the combination of OMC (Octyl Methoxy Cinnamate) and avobenzone, the most efficient UVB filter and UVA filter is well known to be not photo-stable unless used together with photo-stabilizers such as Octocrylene or 4- Methylbenzyl Camphor. Unfortunately, these routes of stabilization are blocked by patent restrictions. Another approach to photo-stabilizing avobenzone is encapsulation[1-2]. OMC in glass particle or OMC in silicone resin particle are the commercial examples of the encapsulation approach. However, as avobenzone has several other drawbacks beside poor photo-stability such as poor solubility to cosmetic media, especially non-solubility to silicone oils, making complex with metal ions in formula and so on. Thus, the encapsulation of OMC can not be a complete cure. Recently our company developed the hybrid PMMA (Polymethylmethaacrylate) bead system that is made of solid PMMA matrix with embedded avobenzone by suspension polymerization. Hybrid PMMA bead is physically unbreakable, spherical, of no odor so brings many kinds of cosmetic benefits for sunscreen formulators such as minimized skin irritancy, good sensorial feeling, water based formula compatibility, silicone based formula compatibility, improved photo-stability and so on Materials and Methods

2 Materials PMMA, Avobenzone, OMC(Octyl Methoxy Cinnamate), OS(Octyl Salicylate) We prepared two types of Hybrid PMMA via suspension polymerization: Grade Composition Particle size(um) Hybrid BMDBM(Avo Benzone) 25~30% 2~7 ABOS Octyl Salicylate 5~8%, PMMA 62~70% Hybrid ABOMC BMDBM(Avo Benzone) 25~30% 2-Ethylhexyl 4-methoxycinnamate 5~8%, PMMA 62~70% 2~7 Figure 1-Hybrid ABOMC Methods Sun protection efficacy was measured by In vitro SPF analyzer (Optometrics 290) 85.7 MED was applied for photo-stability test and its test condition was: Light source: Solar Cell Tester (one port), Light intensity: 1000uW/cm2 = 0.001W/cm 2, Irradiation time: 30min = 1800sec, Light energy = 0.001W/cm2*1800sec = 1.8J/cm 2, Average 1 MED of Koreans tested = 0.021J/cm 2, Irradiated MED = (1.8J/cm 2 )/(0.021J/cm 2 ) = 85.7 MED Skin irritation test was done by closed patch test and its test condition was: Sample size: 5 Koreans, Application time: 72hr, Dosage: 25μl Results and Discussions

3 Sun Protection Efficiency 5 test samples were prepared and their sun protection efficacies were measured Table I-in vitro sun protection test sample preparation #1 #2 #3 #4 #5 HYBRID ABOMC HYBRID ABOS Avobenzone Octocrylene Octyl Methoxy Cinnamate Octyl Salicylate PMMA-S C12-15 Alkyl Benzoate Vaseline Table II-in vitro sun protection results #1 #2 #3 #4 #5 SPF UVA/UVB ratio Boots Star Rating Average UVA PF Critical Wavelength As shown above, sample #1 and sample #4 had exactly the same amount of OMC and avobenzone and showed the similar level of UVA and UVB protection properties. Again sample #1, #4 and #5 had the similar amount of OMC and avobenzone and showed similar level of UVA and UVB protection properties. Photo-stability After 85.7MED applied to all of the samples below, in vitro SPF were measured: Table III-Photo-stability test results (before after) #1 #2 #3 #4 #5 SPF UVA/UVB ratio Boots Star Rating

4 Average UVA PF Critical Wavelength Sample #1 showed poor-photostablity Sample #2, #3, #4, #5 showed good photo-stabilities Skin Irritancy test Dermal response evaluation criteria: 0 = No evidence of irritation 1 = Minimal erythema, 2 = Readily visible erythema, 3 = Erythema and papules 4 = Definite edema 5 = Erythema, edema, and papules 6 = Vesicular eruption 7 = strong reaction spreading Test results Table IV-Skin Irritancy test at Isohexadecane base #1 #2 #3 #4 #5 #6 #7 #8 #9 Distilled Water Isohexadecane SUNPMMA-S OMC AvoBenzone Hybrid ABOMC Dermal response Table V-Skin Irritancy test at Alkyl Benzoate base #11 #12 #13 #14 #15 #16 #17 #18 #19 Distilled Water Alkyl Benzoate SUNPMMA-S OMC AvoBenzone Hybrid ABOMC Dermal response

5 Sample #4, #5 & #14 showed significant dermal irritation response While sample #6 and #16 showed no skin irritation Conclusions An efficient sunscreen must, first of all, show good sun protection efficiency, good photo-stability, safety, ease to incorporate in various formulation and cosmetically acceptable aesthetics (i.e. good sensorial feeling, not too much whitening, and no odor) Based on the test results of table II, Avobenzone embedded Hybrid PMMA beads, both Hybrid ABOS and hybrid ABOMC performed as efficiently as compared to incorporating avobenzone and OMC directly into cosmetic media. At the same level of avobenzone and OMC in cosmetic formula, whether avobenzone or OMC are firstly embedded in Hybrid PMMA bead system then later incorporated to media or directly incorporated to cosmetic media from the beginning, did not make any difference in sun protection efficacies Photo-degradation of Avobenzone can be successfully blocked as avobenzone is immobilized or located inside solid PMMA matrix where avobenzone are segregated or protected from other UV filters or any other potentially reactive chemicals. Thus, hybrid PMMA system is very a novel and innovative way to improve photo-stability of avobenzone. In addition, as avobenzone is embedded in PMMA bead, poor formula stability of avobenzone mostly originated from poor media solubility of avobenzone and complexation with metal ions is also greatly improved. Figure 2-Photo-degradation pathways of avobenzone

6 Skin irritation test results (Table IV & V) showed that Hybrid PMMA bead system greatly minimized skin irritation of avobenzone and OMC by reducing skin penetration. Hybrid PMMA beads would be kept on the outermost layer of the skin because Hybrid PMMA bead is too big(i.e. 5um) to penetrate the corneal layer. While, it is wildly believed that molecules with molecular weight less than 500 Da are considered as potential allergens. In that sense, as molecular weight of chemical filters tested here are less than 500(Avobenzone Mw: 310.4, OMC Mw: 290), it s no wonder that the big micro sized Hybrid PMMA bead system is very safe to skin as compared to incorporating small chemical filters to cosmetic formula directly Moreover, a good sun screen material should provide formulators global registration and patent freedom. As Hybrid PMMA system utilizes globally approved UV filters such as avobenzone, OMC and OS, there is no restriction of usage of Hybrid PMMA beads worldwide. As our company applied for global patents with regard to the synthesis of Hybrid PMMA bead system and its application to cosmetic formula, so sunscreen formulators would enjoy global patent freedom too. References [1] Schwack W. Rudolph T. Photoreactions of chemical UVA filters in Cosmetics. GIT Lab J 1997; 1:17-20 [2] Chadorowski S, Quinn FX, Sanchez C. Assignee: L Oreal. Method for improving UV radiation stability of photosensitive sunscreen filters. US Patent No. 6,607,713 issued August 19, 2003 Acknowledgement We are greatly thankful to David Schlossman, KOBO products Inc for his idea generation about the initial concept of Hybrid PMMA system