Preparation Of Nanostructured Lipid Carrier Coated With Sunscreen Agent And Research On Sunscreen Effect

The efficiency of a cosmetic product depends not only on the active ingredients,but also on the carrier system devoted to improve its bioavailability.After the SLN,second generation lipid systems for the delivery of bioactive compounds have been developed by mixing a liquid carrier oil with a solid lipid to form so-called nanostructured lipid carriers（NLCs）,which still the blend being solid at body temperature.The article aims to encapsulate two couples of UV molecular absorbers,with a blocking action on both UVA and UVB domains,into efficient lipid nanoparticles by hot high pressure homogenization technique.The optimal homogeneous condition parameter was determined in single factor experiment,which was as follows:homogenization pressure of 800 bar,homogenization temperature of 80℃and homogeneous four times.Based on the orthogonal test results,the optimum formulation parameter for the preparation of NLCs were as follows:total oil phase account for 6%,GTCC accounts for the total lipids is 25%,and emulsifier content is 4%,with the high encapsulation efficiency of BP-3 and OMC,93.2%and 98.8%,respectively.The particle size was 138.7±0.5 nm,polydispersity index（PDI）was 0.142±0.021 and zeta potentiawas-28.30±0.98 mV.Furthermore,TEM images of the NLC formulation were obtained,which the particles acquired smooth surface and were spherical in shape but preparation of the sample by lyophilization induced the aggregation of nanoparticles.Then,the NLC was characterized by FTIR,XRD and DSC,the results suggesting that the sunscreen would be molecularly dispersed within the matrix or distributed in the lipid matrix in an amorphous state.The NLC formulations were incorporated into hydrogel formulations,and the ultraviolet absorbance and photostability behaviour were measured.The result shows that,NLC loaded such sunscreen couples have a better UV absorption performance and good photostability in comparison to the conventional emulsion.This study provides a suitable cosmeceutical lipidic colloidal system of UV absorb to be employed as a successful photoprotective preparation.Also,the influence of electrolyte and the emulsifier content on the aggregation kinetics of NLC was investigated.Aggregation kinetics of the BP-3-OMC-NLC exhibited reaction-limited and diffusion-limited regimes in the presence of both electrolytes,having critical coagulation concentrations（CCC）of 535 mM and 96.3 mM for the monovalent（NaCl）and divalent（CaCl₂）salts,respectively.The CCC decreases with the increase of emulsifier concentration for NLCs,suggesting that the A165influence the aggregation behavior of the SLN by its steric stabilization.In addition,an aggregation behavior model of NLC at different NaCl concentration（0¹000 mM）and different mass fraction A165 emulsifier（0⁴%）is also established,which can be used to predict the stability of NLC system in this range.As a liquid lipid,GTCC was synthesized under microwave irradiation whereby the esterification reaction of caprylic/capric acids with glycerol in this study.Subsequently,gas chromatography mass spectrometry（GC/MS）were used to determine the structure and compositions of the liquid products,and the yiled of the triglyceride was 95.7%.Compared to the conventional heating method,microwave assisted synthesis of GTCCs shortened the reaction time greatly when achieving the same conversion.Response surface methodology（RSM）with a 3-level-3-factor central composite design（CCD）was applied to model and optimize the reaction conditions and,a quadratic model was developed as consequence,in order to correlate the preparation variable to the response.The optimum conditions for the synthesis of GTCC were as follows:reaction temperature of 190℃,substrate mole ratio（fatty acid:glycerol）of 3.33:1 and PTSA loading of 4.30 Wt.%.Under these conditions,the actual hydroxyl value 1.12 mgKOH.g^-1 was obtained,which is comparably well with the minimum predicted value of 1.03 mgKOH.g^-1,corresponding to the conversion yield was 99.7%.