Effect of solid lipid's structure on nanostructured lipid carriers encapsulated with sun filter: characterisation, photo-stability and in vitro release.

Three series of solid lipid are formulated in nanostructured lipid carriers (NLC) system, which encapsulated with sun filter to evaluate the effect on the physicochemical properties of the nanocarriers. Production is performed by ultrasonication-homogenisation, analysis by particle size, zeta potential (ZP), transmission electron microscope, Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD). Moreover, the encapsulation efficiency, ultraviolet performance and in vitro release are also investigated. The particle sizes of NLCs are between 185 and 225 nm and the polydispersity index is lower than 0.4, ZP from -56.4 to -78.6 mV, and the particles are spherical and in homogenous shading. All prepared NCLs encapsulated the sun filter and the EE are higher than 73%. DSC analysis revealed α- to β-polymorphic modification existed in the system of fatty alcohol and fatty acid. However, α, β and β'-polymorphic modifications are exist in the system of cetyl palmitate (PC). Compared with conventional emulsion, all NLCs displayed perfect photo-protective property, especially for the alcohol system. The photo-stability studies showed that the all NLCs have the ability to improve the photo-stability of sunscreens. The in vitro release study suggested all three NLCs displayed sustained release profile and they were fit well with Higuchi equation.