Fabrication And Characterization Of Nanoemulsion System For Ceramide

Ceramide is an important lipid naturally present in the stratum corneum,which can significantly improve the barrier function of the skin.However,the direct addition of ceramide will cause problems such as crystallization and poor transdermal performance,which greatly limits its application in cosmetics.It is necessary to use a suitable carrier to encapsulate it to improve these application defects.One of the commonly used carriers is nanoemulsion.In this study,nanoemulsion was used to carry Ceramide Ⅲ(Cer3).The mechanism of the system’s inhibition of Cer3 crystallization was explored.The transdermal performance of Cer3-nanoemulsion was investigated,and the nanoemulsion system for co-transporting Cer3 and coenzyme Q10(CoQ10)was constructed to investigate the permeation promotion mechanism of Cer3.On this basis,phytosphingosine(PS)with the functions of emulsification and penetration promotion and cholesterol(CHOL)and fatty acid(FA)which simulate the lipid composition of the stratum corneum were added to improve the high-temperature storage stability and transdermal performance of the nanoemulsion system.Firstly,when using hydrogenated lecithin(HSPC)to prepare Cer3-nanoemulsion,it was found that when the mass ratio of glycerol to water was 7:1,the mass fraction of HSPC was4%,the high-pressure homogenization pressure was 900 bar,and the number of cycles was 9,Cer3-nanoemulsion had the smallest particle size,about 80 nm.After dilution,heating,centrifugation,and freeze-thaw cycles,the particle size had no obvious change.Ultra-depth 3D microscope,polarized light microscope and X-ray diffractometer(XRD)found that HSPC can inhibit the formation of Cer3 crystals and reduce its crystallinity.Differential scanning calorimeter(DSC)found that HSPC can reduce the phase transition temperature and melting enthalpy(ΔH)of Cer3.Total reflection fourier infrared spectrometer(FTIR)characterized that there is no chemical reaction between HSPC and Cer3.The fluorescent ceramide(NBD-Cer)emulsion was then observed with laser scanning confocal microscope(CLSM).The image showed that NBD-Cer can be arranged at the oil-water interface of the particles together with HSPC,which proves that HSPC can interact with Cer3 and rearrange with each other.It was speculated that the inhibition mechanism is:HSPC and Cer3 are both double hydrophobic chain structures.After the two are mixed,they will rearrange into a molecular structure embedded with each other due to the similar structure which can disrupt the arrangement of Cer3molecules and inhibit the formation of Cer3 crystals.Secondly,the transdermal performance of Cer3-nanoemulsion and the penetration mechanism of Cer3 to co-delivered CoQ10 were investigated.Compared with the Cer3 oil solution,the content of Cer3 in the skin increased from(0.50±0.13)μg/cm~2 to(4.02±0.74)μg/cm~2 after being transported by the nanoemulsion,indicating that the nanoemulsion can effectively promote the penetration of Cer3.The nanoemulsion that co-transports Cer3 and CoQ10 was then investigated.The results of transdermal experiments showed that as Cer3increased from 0%to 2%,the content of Cer3 penetrated into the stratum corneum increased.And the transdermal content of CoQ10 increased from(5.76±0.41)μg/cm~2 to(9.81±0.60)μg/cm~2.The results of closure effect experiments showed that Cer3 can effectively reduce water volatilization and promote skin hydration.The FTIR characterization results of pigskin showed that the fusion of Cer3 penetrated to the stratum corneum can induce enhanced fluidity of the stratum corneum lipids and loosen the keratin secondary structure,thereby promoting the transdermal delivery of CoQ10.At last,the storage stability of Cer3-nanoemulsion was investigated.The change in particle size showed that the emulsion was prone to Ostwald ripening at 40℃.PS was added to improve the high-temperature storage stability and skin permeability of the system.The results showed that when the PS was 1.5%,the Ostwald ripening rate of the emulsion decreased from 6.06 to1.53 after storage at 40℃.And the contents of Cer3 and CoQ10 in the skin increased to(8.12±0.45)μg/cm~2and(17.66±0.57)μg/cm~2,respectively.CoQ10 can penetrate into the dermis.FTIR characterization of pig skin found that PS can improve the lipid fluidity of the stratum corneum and loosen the structure of keratin through electrostatic interaction with epidermal cells.CHOL and FA were then added to the system.the results showed that when using oleic acid(OA)as FA,the contents of Cer3 and CoQ10 in the skin were increased to(11.94±0.56)μg/cm~2 and(24.18±0.71)μg/cm~2,respectively.FTIR characterization of pig skin found that OA can enhance the lipid fluidity by twisting the lipid bilayer and disrupting the orderly arrangement of lipids in the stratum corneum.The Cer3/CHOL/FA molar ratio was further investigated.The results showed that when the molar ratio was 1:1:1,the contents of Cer3 and CoQ10 in the skin were increased to(13.69±0.51)μg/cm~2 and(28.60±0.68)μg/cm~2respectively.After FTIR characterization of pig skin,it was found that at this molar ratio,the emulsion lipids had the best compatibility with stratum corneum lipids,and could fuse with stratum corneum lipids then induce lipid fluidity enhancement.