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A novel, metal ion-assisted drug-loading model, in which the metal ion was used to modify the microstructure of DPPC bilayers, has been developed to improve the drug-loading efficiency of cisplatin thermosensitivity liposomes. The reactions of dipalmitoyl phosphatidylcholine (DPPC) with diverse metal ions (Zn(2+), Cu(2+), Mn(2+) and Mg(2+)) yield four typical liposomes, which have been characterized by FT-IR, Raman and fluorescence techniques; the mechanism for higher drug encapsulation efficiency has also been investigated. In these prepared liposomes, the conformation of DPPC is changed due to the electrostatic interaction between the metal ions and phospholipid acyl group, leading to a closer arrangement of the lipid hydrocarbon chains and higher Tm of DPPC. As a result, the encapsulation efficiency of metal ion-assisted loading liposome is significantly higher than that of metal ion-free state. While for the release time, all four metal ion-assisted liposomes could be released within 10min at 42±0.5°C, which approach to the phase transition temperature, indicating that the introduction of metal ions into the DPPC bilayer membranes has no influence on the thermosensitivity of the liposome. Furthermore, the higher cytotoxicity of metal ion-bounded liposomes than that of free cisplatin solution suggests that high encapsulation efficiency can cause cytotoxicity increase. Hence, this work highlighted that metal ion-assisted loading model increased the encapsulation efficiency and cell cytotoxicity of cisplatin in thermosensitive liposomes with no obvious effects on sustained and temperature-dependent drug release., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Purpose: In order to improve formulation of targeting chemotherapy, cisplatin-loaded magnetic solid lipid nanoparticles (MSLNs) were prepared. In present study, the deliberate loading of Fe3O4 magnetic nanoparticles (MNs) into cisplatin SLNs was developed., Methods: SLNs were produced by film scattering ultrasonic technique. The effects of two different loading procedures of MNs on the microstructure and physicochemical properties of MSLNs were investigated by transmission electron microscopy (TEM), zetasizer, infrared spectroscopy (IR), and fluorescence spectroscopy. In vitro drug release and cytotoxicity against human cervical carcinoma SiHa cells, in vivo tumor cell uptake and target tissue distribution of MSLNs under external magnetic field were investigated., Results: The encapsulation efficiency of cisplatin and the content of MNs in procedure I SLNs were 69.20 ± 4.5% and 2.16 ± 0.53 mg/mL, respectively, which were higher than those of procedure II MSLNs. In procedure I, the MNs, which were combined with lipids during film formation, distributed in the middle of the lipid layer in SLNs. Differently, in procedure II, the MNs and cisplatin were contained in an interior compartment in SLNs, resulting from mixing with drugs during hydration of lipid film. The procedure I MSLNs had higher cytotoxicity than procedure II MSLNs or free cisplatin. With in vivo intratumoral administration, cisplatin concentration in the tumor tissue was maintained at higher level for MSLNs than that for free cisplatin, especially under external magnetic field., Conclusions: Procedure I, the developed deliberate MNs loading method, was superior over procedure II in cisplatin encapsulation efficiency, MNs content and cell cytotoxicity.