Langmuir-Blodgett (L-B) transfer of mixed octadecanethiol (Ci8SH)-octadecanol (CigOH) monlayers onto vapor-deposited gold films on glass slides leads to the formation of stable, densely packed monomolecular films when the composition of the mixed monolayers involves 60-80 mol % octadecanethiol. This composition of the mixed L-B films is a result of a trade-off between the mole fraction of CigOH, whose increasing magnitude allows one to increase surface pressure of a mixed monolayer during an L-B transfer, and the mole fraction of CigSH, whose increasing magnitude enhances stability of the mixed monolayer on the gold surface following the L-B transfer. The passivating properties of CigSH/CigOH L-B monolayers were investigated electrochemically. Determination of interfacial capacitance and measurements of the extent of permeability of the surface monolayers by cyclic voltammetry demonstrated that the passivating characteristics of the CigSH/CigOH L-B monlayers are essentially identical to the best self-assembled octadecanethiol monolayers described in the literature. L-B transfer of monolayers containing small quantities of an electroactive reagent can be used as a general technique of reagent immobilization at the electrode surface. Unlike self-assembly methods, reagent incorporation in Langmuir-Blodgett monolayers offers precise control of their composition in a broad range of concentrations. Comparison of the surface concentrations of ubiquinone incorporated in CigSH/CigOH monolayers at the air/water interface before L-B transfer and at the electrode surface following L-B transfer gave 1:1 correlations in the concentration range 1.0 X 10~12-1.0 X 10~10 mol/cm* 12.
Lipid liquid-crystalline nanoparticles (cubosomes) were used for the first time as a dual-modality drug delivery system for internal radiotherapy combined with chemotherapy. Monoolein (GMO)-based cubosomes were prepared by loading the anticancer drug, doxorubicin and a commonly used radionuclide, low-energy beta (β−)-emitter, 177Lu. The radionuclide was complexed with a long chain derivative of DOTAGA (DOTAGA-OA). The DOTAGA headgroup of the chelator was exposed to the aqueous channels of the cubosomes, while, concerning OA, the hydrophobic tail was embedded in the nonpolar region of the lipid bilayer matrix, placing the radioactive dopant in a stable manner inside the cubosome. The cubosomes containing doxorubicin and the radionuclide complex increased the cytotoxicity measured by the viability of the treated HeLa cells compared with the effect of single-drug cubosomes containing either the DOX DOTAGA-OA or DOTAGA-OA-177Lu complex. Multifunctional lipidic nanoparticles encapsulating the chemotherapeutic agent together with appropriately complexed (β−) radionuclide are proposed as a potential strategy for effective local therapy of various cancers.
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