Two Azobenzene Derivatives CAB/ACB As Reusable Sunscreen:UV Absoretive Capacity And Biosafety Evaluation

The destruction of the ozone layer has led to an increasing number of ultraviolet rays to the earth.Ultraviolet irradiation can cause sunburn,erythema,skin aging and even skin cancer.A variety of UV protection measures are required,such as the recommended of sunscreen cosmetics in daily life.At present,avobezone is the most popular commercial UVA sunscreens components.But it might undergo photodegradation and to produce harmful by-products under the irradiation of ultraviolet light.Azobenzene derivatives as photo responsive compounds have been widely used in the fields of photo controlled drug release,artificial ion channels,DNA photoconductors and so on.Two azobenzene derivatives,4-cholesterocarbonyl-4'-(N,N,N-triethylaminebutyloxyl bromide)azobenzene(CAB)and 4-cholesterocarbonyl-4'-(N,N-diethylaminebutyloxyl)azobenzene(ACB)were synthesized by our group,while CAB with a positive charge and ACB without charge,and both have good absorption capacity near 360 nm.In this study,the biological safety and UV protection ability of two azobenzene compounds were measured in vivo and in vitro,and the possibility of their application in sunscreen cosmetics was also evaluated.The study is divided into two parts: the safety evaluation and the ultraviolet protection ability assessment of the two azobenzene compounds.In the first part of the safety evaluation section,both azobenzene compounds have high molar extinction coefficients in the UVA region.The reversible photoisomerization process allows repeated absorption of UVA and provides a structural basis for the development of reusable sunscreens.MTT assay was used to detect the cytotoxicity of two azobenzene compounds in cis-states.The results showed that the cell viability treated with azobenzene compounds were greater than 95%,indicating that cis-ACB and cis-CAB with no cytotoxicity.Agarose gel electrophoresis and TUNEL staining methods were used to evaluate the cell apoptosis induced by two azo compounds.Both ACB and CAB did not cause DNA breaks or aggregates even at the concentrations of 100 ?g /mL.Treated with azobenzene compounds for 24 hours did not induce the DNA damage or apoptosis of NIH 3T3 cells.According to the neutral red phototoxicity test results,CAB did not show cell phototoxicity.In contrast,ACB has certain cytotoxicity.However,animal skin phototoxicity test results showed that both two azobenzene compounds have no phototoxicity.In the second part of the evaluation of UV protection ability,both DCFH-DA fluorescent probe and chemiluminescence probe L-012 were used to detect reactive oxygen species(ROS)generation induced by UVA irradiation.Skin damage was evaluated by histological sectioning.The results showed that ROS production increased with the dose increasing of UVA irradiation,the cell viability decreased.The two azobenzene compounds can effectively absorb ultraviolet light to avoid the generation of ROS and protect cells.UV irradiation causes the stratum corneum shedding,the epidermis and dermis significantly thicker and fibrous cells arranged in disorder.The chemiluminescent probe L-012 achieved a real-time imaging of UVA-induced skin ROS in mice.The two azobenzene compounds with cream once again exhibited the anti-UVA efficacy after two rounds of UV exposure with this method.In summary,the two azobenzene compounds CAB/ACB synthesized by our group are expected to become a new type of sunscreen that can provide continuous UV protection.