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Li X.,CAS Shanghai Institute of Materia Medica | Li X.,Zhejiang Chinese Medical University | Li H.,CAS Shanghai Institute of Materia Medica | Xiao Q.,Hainan Weikang Pharmaceutical Co. | And 6 more authors.
Physical Chemistry Chemical Physics | Year: 2014

The influence of surfactants on the stability of cyclodextrin (CD) Pickering emulsions is not well understood. In this study, we report two-way effects of Tween 80 and soybean lecithin (PL) on the long term stability of Pickering emulsions stabilized by the self-assembled microcrystals of α-CD and medium chain triglycerides (MCT). The CD emulsions in the absence and presence of Tween 80 or PL at different concentrations were prepared and characterized by the droplet size, viscosity, contact angle, interfacial tension and residual emulsion values. After adding Tween 80 and PL, similar effects on the size distribution and contact angle were observed. However, changes of viscosity and interfacial tension were significantly different and two-way effects on the stability were found: (i) synergistic enhancement by Tween 80; (ii) inhibition at low and enhancement at high concentrations by PL. The stability enhancement of Tween 80 was due to the interfacial tension decrease caused by the interaction of Tween 80 with CD at the o/w interface at lower concentrations, and significant viscosity increase caused by the Tween 80-CD assembly in the continuous phase. For PL at low concentrations, the replacement of α-CD/MCT by α-CD/PL particles at the o/w interface was observed, leading to inhibitory effects. High concentrations of PL resulted in an extremely low interfacial tension and stable emulsion. In conclusion, the extensive inclusion of surfactants by CD leads to their unique effects on the stability of CD emulsions, for which the changes of viscosity and interfacial tension caused by host-guest interactions play important roles. This journal is © the Partner Organisations 2014. Source


Li X.,Zhejiang Chinese Medical University | Li X.,CAS Shanghai Institute of Materia Medica | Guo Z.,CAS Shanghai Institute of Materia Medica | Guo Z.,University of Bradford | And 9 more authors.
Yaoxue Xuebao | Year: 2014

Paracetamol was used as a model drug in this study to investigate the synergetic effects of lipid coating and β-cyclodextrin (β-CD) inclusion for masking the bitter taste of poorly soluble drugs. To control the concentration as low as possible of the free drug which produced a bitter taste, a kinetic model was established to calculate the drug distribution theoretically among the free drug in medium, lipid coated particles and molecular inclusion on the basis of the preparation and characterization of the lipid microspheres, so as to select the proper amount of β-CD. Finally, the synergetic drug delivery systems were prepared and characterized by 1H nuclear magnetic resonance (1H NMR), molecular simulation and the electronic tongue. As a result, the drug release rate constant (k) of the lipid microspheres coated with octadecanol was determined as 0.001 270 s-1. Then, the synergetic drug delivery systems were prepared with the ratio of 6.74 : 1 (w/w) for β-CD and paracetamol. The chemical shift values for the fingerprint peaks of paracetamol all increased and hydrogen bonds were formed between the oxygen on the phenolic hydroxyl group, the nitrogen on the imino in paracetamol and the hydrogens on the hydroxyl groups in β-CD. The results tested by the electronic tongue indicated that the paracetamol, lipid microspheres, β-CD inclusion and their mixture showed different taste characteristics, with the bitterness order of the synergetic drug delivery systems ≈ lipid microspheres < β-CD inclusion < paracetamol, which confirmed the synergetic taste masking effects of lipid coating and β-CD molecular inclusion. In summary, the synergetic taste masking was jointly achieved through the retard of the drug release by the lipid coating and the inclusion of the free paracetamol by β-CD through hydrogen bonds. Source

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