Using TiO2 and ZnO

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Using TiO2 and ZnO for Balanced UV Protection
Yun Shao, Ph.D. and David Schlossman Kobo
Products, Inc.
Sunscreen Symposium Disney World Resort September
7, 2007
www.koboproducts.com
2
Introduction
The need to provide broad-spectrum UV protection

• UVA (320-400 nm)
• Photo-aging
• Cancer
• Photosensitivity
• UVB (290-320 nm)
• Sunburn
• Cancer

3
Importance of UVA Protection
Japan Have a long history of UVA regulation
Persistent Pigment Darkening (PPD) method
Plus () system

• EU Sept. 22, 2006, EU Commission published
  recommendations
• UVA 1/3 of SPF, Critical Wavelength gt 370 nm
• UVA protection testing Persistent Pigment
  Darkening method

• USA Aug. 27, 2007, FDA proposed amendment of
  final monograph for sunscreens
• UVA label low, medium, high and highest
• UVA protection testing PPD or Boots Star system

4
Objective

• To investigate the attenuation behavior of TiO2
  and ZnO in UVA and UVB regions
• To develop an combination of only inorganic UV
  filters
• that can provide high and yet balanced UV
  protection to meet regulations globally

5
Can Titanium Dioxide alone provide high and yet
balanced UV protection?
www.koboproducts.com
6
UV Attenuation by TiO2
308 nm max erythemal effectiveness 360 nm Mid
of UVA 524 nm Blue end of visible light
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Transparency of TiO2 Dispersions

195 60 35 15 10 nm
195 60 35 15 10 nm
Asian
Caucasian
195 60 35 15 10 nm
195 60 35 15 10 nm
Latino
Black
All dispersions diluted in Cyclopentasiloxane (to
20 TiO2)
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UVA / B Extinction Ratio and Opacity
Opacity
Ext. ratio
Opacity 12 mm on Lenata card
0.001 in CHCl3
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Test Formulation (O/W)

• 15 - 50 nm TiO2 is pre-dispersed and milled
• SPF and PFA -- all testing on 3 people

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Comparison of Whitening
O/W, 10.3 TiO2 , 12 mm film
PPS 50 nm 35 nm 35 nm Size in dispersion 170
nm 154 nm powder
Size in dispersion --- intensity weighted mean
size measured on Dynamic Light Scattering
Particles sizer
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Comparison of Whitening
O/W, 10.3 TiO2, 12 mm film
PPS 15 nm 15 nm Size in dispersion powder 125 nm
Size in dispersion --- intensity weighted mean
size measured on Dynamic Light Scattering
Particles sizer
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Performance of TiO2 - In-vivo Results
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Role of TiO2 in Balanced UV Protection
For use in sunscreen lotions where whitening
needs to be minimized

• TiO2 cannot provide balanced UV protection.
• It should be used mainly for providing high SPF
• In general, small primary particle size (10 - 15
  nm) and aggregate size shall be used to minimize
  whitening

14
Can Zinc Oxide alone provide high and yet
balanced UV protection?
www.koboproducts.com
15
UV Attenuation by ZnO

• ZnO has more uniform absorption through UVA and
  UVB
• Maximum extinction value is used

Ext. max. Ext. 524
UVA and UVB attenuation Transparency
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Maximum Absorption of Dispersed ZnO
ZnO was milled before diluted for measurement
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Transparency of ZnO Dispersions

PS 120 60 15/35 20 nm PPS 260 260 220
150 nm
Caucasian
All dispersions diluted in Cyclopentasiloxane (to
20 ZnO)
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Test Formulation (W/O)

• Dispersion of 20 - 60 nm ZnO
• SPF and PFA -- all testing on 3 people

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Comparison of Whitening
Active 15 ZnO, 12 mm film
PPS 60 nm 15/35 nm 20 nm 20 nm Size in
dispersion 165 nm 228 nm 167 nm 130 nm
Size in dispersion --- intensity weighted mean
size measured on Dynamic Light Scattering
Particle sizer
20
Performance of ZnO - In vivo Results

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Role of ZnO in Balanced UV Protection

• ZnO can provide balanced UV protection when SPF
  is moderate (lt20)
• For high SPF (30) product, ZnO alone cannot
  provide balanced UV protection unless used at a
  very high level (close to 25).

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Balanced UV Protection

• Existing issue
• The results from last two sections indicate that
  for a transparent sunscreen
• TiO2 alone cannot provide balanced protection
• ZnO alone cannot provide enough SPF

• Solution
• Combo of TiO2 ZnO
• Combo of ZnO of large and small sizes
• Combo of ZnO organic UVB
• Combo of TiO2 organic UVA (outside USA)

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UVA / B Sunscreen Lotions Examples in USA
SPF product labeling PFA PPD test on 3
subjects

• All provides high UVA protection ( )
• But do not reach 3/1 ratio for EU market

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UVA Balanced Sunscreen Formula (W/O)
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Combination of TiO2 and ZnO
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UV Balanced Sunscreen Lotions
KSL-024E KSL-024D KSL-024F
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UV Balanced Sunscreen Lotions
Transparency on fair skin
Dosage 2 mg/cm2
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UV Balanced Sunscreen Lotions
Transparency on tanned skin
Dosage 2 mg/cm2
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UV Balanced Sunscreen Lotions
Transparency on dark skin
Dosage 2 mg/cm2
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Conclusions

• For high SPF and UV balanced formula, TiO2 is
  often too whitening while ZnO is not an efficient
  UVB sunscreen.
• By combing TiO2 and ZnO of right sizes, balanced
  UV protection with SPF of 30 or higher can be
  achieved.
• Combination of ZnO of different size can
  potentially provide balanced UV protection.