A new delivery system based on loading of drug into nanostructured lipid carriers (NLC) and then encapsulating it into hydroxypropyl-β-cyclodextrin (HPCD) has been developed for rutin (RT) to overcome its limitation for practical application. Light microscope, scanning electronic microscope (SEM) and differential scanning calorimeter (DSC) were used to determine the morphology, microstructure and thermal properties of rutin-loaded microencapsulated nanostructured lipid carriers (RT-loaded MNLC), respectively. The effect of HPCD on the performance of RT-loaded MNLC was investigated in terms of particle size, entrapment efficiency, UV absorptivity and in vitro release. It is revealed that the combined encapsulated technology could successfully resolve the leakage and instability problems of rutin. The obtained RT-loaded MNLC in the size range of 210–270 nm (polydispersity index < 0·4) were spherical and homogeneous. The presence of HPCD influences the particle size, entrapment efficiency and release profile of rutin and has synergistic effect on UV protection.

In the cleaning field of the cosmetics industry, amino acid surfactants with low irritation and degradability have attracted more and more attention. However, in the actual application system, the amino acid type surfactant has the application difficulty that is not easy to thicken. In this study, the surface activities and application of the surfactant mixtures containing the cationic surfactant dodecyl tri-methyl ammonium chloride (DTAC) and anionic amino acid surfactant sodium lauroyl glutamate (SLG) (cationic/anionic amino acid surfactant system) were systematically studied, which will provide theoretical guidance for practical applications. First, the surface tension of the cationic/anionic amino acid surfactant system was measured, and the CMC value, interaction parameters, Gibbs free energy and other data were obtained. From this, the behavior characteristics of the adsorption and aggregation of SLG and DTAC in the solution can be judged. Then through dynamic light scattering instrument, rheometer, polarizing microscope, etc., we analyze the phase behavior of the cationic/anionic amino acid surfactant system under different compound ratios and different concentrations, and draw a pseudo-ternary phase diagram. Finally, the influence of the length of the hydrophobic chain of cationic surfactants on the phase behavior of amino acid surfactants was investigated. Experiments have found that the addition of cationic surfactant DTAC can significantly reduce the CMC value of the SLG system, and the CMC changes with the increase of the SLG ratio as follows: first decrease and then increase. The interaction parameters show that DTAC and SLG have a strong interaction. Contrary to the phenomenon of precipitation after the compounding of conventional cationic/anionic surfactants, the compounding of DTAC and SLG increases the solubility, reduces the Krafft point of SLG, and increases the application performance. At the same time, the problem of difficult control of the viscosity of the amino acid surfactant system has also been better solved. DTAC and SLG form a worm-like mixed micelle, which has a higher and controllable viscosity. Finally, it was found that changing the hydrophobic chain length of cationic surfactants has a direct effect on the viscosity of the system. Graphical Abstract

The effect of oil types on the formation and stability of nano-emulsions by D phase emulsification method was investigated comprehensively in this paper. Three kind of oils (straight-chain alkanes, branched alkanes, and esters oils) were used and the formation of the nano-emulsions was studied. The stability of prepared nano-emulsions was characterized by the variation curve of the droplet mean diameter within 28 days. It has been found that for alkane oils, the molecular weight was important to the formation and stability of nano-emulsions. Low molecular weight alkane oil (7# mineral oil, Isododecane) formed smaller nano-emulsions (157.3 nm, 125.1 nm), but the emulsions have poor stability. For ester oils containing heteroatoms in the structure, nano-emulsions with bigger particles tended to be formed due to the better affinity of oils to glycerin. In addition, it was found that the formation and stability of nano-emulsions should be discussed separately. Temperature had different effects at different preparation processes. Abbreviations: HLB: hydrophilic–lipophilic balance; PIT: phase inversion temperature; PIC: phase inversion concentration; EHP: ethylhexyl palmitate; IPM: isopropyl myristate; THE: triethylhexanoin; CCT: caprylic/capric triglyceride;

Aim: The aim of this study was to encapsulate glabridin (GB) into nanoparticles, prepared by an ionic-gelation method blended with chitosan (CS) and poly-γ-glutamic acid (γ-PGA) to address the issue of poor stability and low water solubility of glabridin. Methods: The physicochemical properties of nanoparticles were investigated by transmission electron microscope (TEM), dynamic light scattering (DLS) and fourier-transform infrared (FT-IR) spectroscopy. Result: FT-IR results indicated that the spontaneous interaction between CS, γ-PGA and GB can form a cross linked network-structure, leading to the spontaneous formation of nanoparticles. Morphology of the complex particles was nano-scale spherical shape. Furthermore, particle size was decreased according to the decrease of γ-PGA contents and CS, accompanying with the increase of mixed solution transmittance. The mγ-PGA: mGB = 1: 1 and mCS: (mγ-PGA + mGB) =1: 1 were considered to be a proper preparation condition of CS/γ-PGA/GB hybrid nanoparticles, which produced the smaller nanoparticles with the satisfactory encapsulation efficiency (EE), loading content (LC) and sustained GB release. With the increase of pH values, the potential, EE, and LC decreased gradually, while the particle size increased. The nanoparticles prepared with higher molecular weight γ-PGA had larger particle size and less loading capacity on GB. Additionally, moderate weight ratio of CS/γ-PGA/GB, low pH, and high molecular weight of γ-PGA were favorable for sustained release. Conclusion: It can be concluded that the physicochemical properties of nanoparticles and GB release behaviors were affected by several factors including the weight ratio of CS/γ-PGA/GB, pHvalues, and γ-PGA molecular weight (MW). Nanoencapsulation using CS, γ-PGA and GB has a potential application for the development of functional cosmetic products with skin-whitening effect.