Poly films assembly method

The MEND is constructed by a novel assembly method, the lipid film hydration method [3], which is comprised of three steps 1) DNA condensation with polycations 2) hydration of the lipid film for electrostatic binding of the condensed DNA and 3) sonication to package the condensed DNA with lipids. This packaging mechanism is based on electrostatic interactions between DNA, polycations, and lipids. Plasmid DNA is first condensed electrostatically with a polycation such as poly-L-lysine (PEL) by vortexing at room temperature. The kinetic control of this process is important for controlling... 

In recent years, there has been a steady shift away from the LB technique toward self-assembly methods for the fabrication of mono-layer and multilayer arrays (Fig. 12). In contrast to the LB method, which requires a film balance and careful control over surface pressures during dipping and transfer, self-assembly is carried out by simple immersion of a suitable support into a solution containing an excess of monomer. The formation of multilayer arrays via self-assembly has also become popular. Most commonly, a charged surface is dipped into a solution containing a poly ionic species, followed by dipping into a second solution that contains a polymeric counterion. Repetition of such dipping then produces the desired material in a layer-by-layer manner. 

Several polymer/polyelectrolyte-nanocrystal hybrid devices have been fabricated seeking to exploit the electro and photoluminescent properties of such material [179-188]. Device fabrication in all these cases is by low-cost self-assembly based techniques. These devices utilize thin films of these hybrids obtained either by multilayer deposition or drop/spin casting methods. Thus, solar cells have been made from poly(2-hexylthiophene)-CdSe nanorod multilayers, lasers from drop cast films of CdSe-titania composites and an infrared emitter from multilayers... 

The LbL technique is undoubtedly one of the best methods to incorporate biological components into man-made devices. Therefore, sensor applications must be one of the most promising subjects for LbL assemblies of biomaterials. For example, Leblanc and coworkers used several bilayers of chitosan and poly(thiophene-3-acetic acid) as cushion layers for stable enzyme films [187]. The first five bilayers of the cushion layer allowed for better adsorption of organophosphorus hydrolase than the corresponding adsorption on a quartz slide. The immobilized enzyme becomes more stable and can be used under harsher conditions. The assembled LbL films can be used for spectroscopic detection of paraoxon, an organophosphorus compound. This cushion layer strategy provides a well-defined substrate-independent interface for enzyme immobilization, in which the bioactivity of the enzyme is not compromised. This leads to fast detection of paraoxon and quick recovery times. 

Upon supramolecular self-assembly, low molecular-weight additives can be used to adjust the properties of BC bulk films by hydrogen bonds. Ikkala and coworkers first introduced this concept in PS-fc-poly(4-vinylpyridine) (P4VP) stoichiometrically complexed with pentadecylphenol molecules to form the supramolecules by hydrogen bonding (Makinen et al., 2000). The advantages of this method are as follows ... 

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