Total Defense + Repair: A Novel Concept in Solar Protection and Skin Rejuvenation

visible and IR light), and nor does it prevent heat accumulation damage.⁶⁵ Thus, none of the commercially-available sunscreens (that can block wavelengths up to 380 nm) are able to block 100% of UVR. For example, SPF 15 filters out approximately 93% of all incoming UVB rays. SPF 30 and SPF 50 keep out 97% and 98% of total UVR. The magnitude of the UVB radiation that escapes UV-filters may seem negligible, but can make a difference if the person has light-sensitive skin or a predisposition to skin cancer.

Although different wavelengths of solar radiation (UVA, UVB, IR, visible) damage human skin by activating different pathways, they share as a common mechanism the generation of RMS and oxidative stress (Figure 1). Therefore, it is logical to assume that more realistic broad solar protection can be accomplished by the combination of SPF active ingredients and antioxidants.⁶⁵ A key consideration for boosting SPF protection is to select the appropriate blend of antioxidants. Specifically, antioxidants should exhibit stability in response to solar radiations and to heat, and should also show high potency to neutralize RMS activity while promoting repair of damaged structures.

Inspired by the need to provide patients with a more comprehensive solar protection, SkinMedica® created Total Defense + Repair (TD+R), a rejuvenating superscreen that represents a new generation in solar skin care protection. TD+R combines SPF actives providing UVA and UVB broad spectrum protection with a proprietary blend of antioxidants (SOL-IR Advanced Antioxidant Complex™) that provides IR-A and heat protection while minimizing inflammation and promoting skin repair. Efficacy testing of TD+R was evaluated using in vitro, ex vivo, and clinical testing.

Protection against UVB radiation was tested using Epiderm-full thickness (Epiderm-FT™; MatTek Corporation, Ashland, MA, USA) radiated with a UVB light dose equivalent to 5 MED (200 mJ/cm²). As expected, this dose of UVB resulted in the formation of sunburn cells (SBCs) and cyclobutane pyrimidine dimers (CPDs) in radiated but untreated tissues (Figures 2 and 3). Pre-treatment of tissues with TD+R SPF34 (2 μl/cm²) 10 minutes before UVB radiation prevented both SBC and CPD formation, as well as other histological changes associated with UVB radiation. Interestingly, pretreatment with TD+R SPF34 also helped prevent UVB-mediated down regulation of ECM genes (Figure 4).

IR-A protection was evaluated using abdominal human skin explants (Figure 5). Human tissues were pretreated with SOL-IR Advanced Antioxidant Complex (2 μl/cm²) for 5 days before being radiated with a single dose of IR-A (720 J/cm²). We observed a significant alteration of tropoelastin distribution and abundance in both papillary and upper reticular dermis response to IR-A (24 hours after IR-A radiation). Pretreatment with SOL-IR Advanced Antioxidant Complex partially prevented these alterations (Figure 5). Moreover, tissues treated with this unique blend of antioxidant do not differ from the control tissues (non-radiated, non-treated) after 4 days IR-A radiation (data not shown).

To assess the ability of TDR to protect against IR-induced heat accumulation, a proof of concept clinical study was conducted. Two test sites (2 cm x 5 cm), including untreated control and TDR, were randomly assigned to designated locations on the back of each subject. TDR+R SPF34 was applied approximately 15 minutes prior to IR radiation exposure. Subjects were positioned 33 cm away from the IR source (Hydrosun ® 750; Hydrosun GmbH, Mullheim, Germany), which has an emission wavelength range of 760 nm to 1,400 nm. The test sites were exposed in 30 minute increments, where the surface skin temperature was recorded every 30 minutes. Infrared thermograph images were taken every 30 minutes to capture the skin’s surface temperature (ICI 9320 P-Series Thermal Camera; ICI Infrared Cameras Inc., Beaumont, Texas, USA) at baseline and at minutes 30, 60, 90, 120, and 150. Test sites treated with TDR consistently provided protection against IR-induced heat compared with untreated sites at all follow-up time points (Figure 6). The mean temperature for TDR test sites was significantly lower than untreated at 90 minutes (P<.039) and trended toward significance at other time points.

Initial clinical-use testing of TD+R SPF34 on subjects with moderate to severe facial photodamage demonstrated visible improvements in lines and wrinkles after 4 weeks of once-daily use (Figure 7). In a separate clinical study, significant improvements in lines and wrinkles, skin tone unevenness, and texture were observed after only 2 weeks of twice-daily use in subjects with moderate to severe facial photodamage (all P≤.03). These initial results suggest that the antioxidants included in TDR work beyond providing protection against solar radiation, and may also work on repairing existing photodamage.