Adsorption behavior of plasmid DNA on binary self-assembled monolayers modified gold substrates

Molecular mechanism of stabilization of thin films for improved water evaporation protection

All-atom molecular dynamics simulations and experimental characterization have been used to examine the structure and dynamics of novel evaporation-suppressing films where the addition of a water-soluble polymer to an ethylene glycol monooctadecyl ether monolayer leads to improved water evaporation resistance. Simulations and Langmuir trough experiments demonstrate the surface activity of poly(vinyl pyrrolidone) (PVP). Subsequent MD simulations performed on the thin films supported by the PVP sublayer show that, at low surface pressures, the polymer tends to concentrate at the film/water interface. The simulated atomic concentration profiles, hydrogen bonding patterns, and mobility analyses of the water-polymer-monolayer interfaces reveal that the presence of PVP increases the atomic density near the monolayer film, improves the film stability, and reduces the mobility of interfacial waters. These observations explain the molecular basis of the improved efficacy of these monolayer/polymer systems for evaporation protection of water and can be used to guide future development of organic thin films for other applications.

Cucurbit[8]uril supramolecular assembly for positively charged ultrathin films as nanocontainers

The design of positively charged ultrathin films for surface modification is of crucial importance for biomedical applications. Herein, we report the layer-by-layer assembly of pure positively charged ultrathin films based on the host-guest interaction of cucurbit[8]uril (CB[8]). Two positively charged poly(ethylenimine)s (PEI) functionalized with guest moieties methyl viologen (MV) and indole (ID) were alternately assembled with the formation of CB[8] ternary complex under basic conditions. The growth of the (PEI-MV@CB[8]/PEI-ID) films was monitored by spectroscopic ellipsometry and quartz crystal microbalance. The morphology and structure of the films were characterized by scanning electron microscopy and UV-vis spectroscopy, respectively. These positively charged (PEI-MV@CB[8]/PEI-ID) films were very stable in the pH range from 4 to 9 but disassembled immediately when subjected to a competitive guest adamantylamine. Finally, the films were successfully employed as nanocontainers for DNA loading and subsequent directing the transfection of the adhered cells.