Preparation And Anti Ultraviolet Application Of Bacterial Cellulose/Polydopamine Composite Nanomaterials

If the skin is exposed to the sun for a long time,it will cause a series of physiological reactions,such as skin inflammation and keratin thickening.Ultraviolet light(UV light)is the main cause of skin damage and skin aging.The shorter the wavelength,the higher the energy,and the greater the degree of skin damage.Although UVB(290-320 nm)has relatively weak penetration,its energy is very high.It can penetrate the epidermis of the skin to reach the superficial dermis,mainly causing DNA damage,oxidative stress and skin inflammation.UVA(320-400 nm)has a strong penetration ability,which can penetrate the epidermis to the dermis,induce apoptosis of fibroblasts,destroy the extracellular matrix,produce a great quantity of oxygen free radicals,trigger inflammatory reaction,immune response,etc.,and eventually cause skin photoaging.Traditional anti ultraviolet methods include:physical sunscreen can diffuse ultraviolet rays by introducing nanoparticles(TiO₂,ZnO or CeO₂),but its ability to block long wave UVA is very weak;chemical sunscreen can absorb ultraviolet rays by adding diketones,salicylates and other chemicals,but chemicals are easy to cause skin allergic reaction and damage human health.Therefore,we need to develop new safe and highly-efficient UV resistant materials.Bacterial cellulose is a kind of natural polymer produced by bacterial fermentation.On the one hand,it has the characteristics of high degree of polymerization,high crystallinity,high purity,strong water retention,high biological safety and good biodegradability.In addition,bacterial cellulose can also scatter ultraviolet light,so it has ultraviolet shielding function.Polydopamine is a kind of melanin material with high biological safety.It contains catechol and other polyphenols.It can absorb ultraviolet light,inhibit the activity of tyrosinase and catalase,reduce and decolorize melanin,and remove reactive oxygen species.Therefore,this study is proposed to prepare a kind of UV resistant composite nanomaterials based on bacterial cellulose and artificial melanin.By controlling the self polymerization process,polydopamine was successfully coated on the surface of bacterial cellulose,and finally a new type of composite nanomaterial with high UV resistance was prepared.Acetobacter xylosum was selected as the fermentation strain to prepare bacterial cellulose by dynamic fermentation;bacterial cellulose colloid was prepared by chemical purification and mechanical crushing;then,polydopamine(PDA)was grown on the surface of bacterial cellulose via oxidative self polymerization of dopamine to prepare bacterial cellulose/polydopamine composite material(BC@PDA).The results showed that polydopamine was uniformly deposited on the surface of bacterial cellulose by electron microscope observation.The formation of bacterial cellulose/polydopamine composite was further confirmed by infrared spectrum and Raman spectrum analysis.Thermogravimetric analysis showed that the thermal stability of BC@PDA was significantly improved after PDA deposition.The ultraviolet visible spectrum analysis showed that BC@PDA shows excellent UV shielding performance in the wavelength range of 290-400 nm.Furthermore,human immortalized keratinocytes(Ha Ca T)and mouse fibroblasts(NIH3T3)were selected for in vitro study.BC@PDA showed minimal cytotoxicity in the range of 50-500?g/ml.It could efficiently protect the two cells against UV irradiation at a concentration of 500?g/m L.It can also effectively reduce the generation of reactive oxygen species in cells under UV irradiation,and prevent cell apoptosis.Finally,BALB/c nude mice were used as an animal model for in vivo assay.The mice were irradiated with UVA and UVB to mimic natural light.After one week of UV irradiation,the left back of nude mice smeared with basic cream showed obvious signs of peeling and redness,while the right back of nude mice smeared with BC@PDA cream showed significantly reduced redness and swelling.The results showed that the abnormal proliferation of the skin of nude mice was significantly alleviated,the thickness of the cuticle was not thickened,and the epidermal cells were evenly arranged when treated with BC@PDA.Taken together,BC@PDA can be an excellent UV resistant agent.