Adsorption and desorption behaviors of cationic liposome-DNA complexes upon lipofection in inside and outside biomembrane models using a dynamic quasi-elastic laser scattering method.

The dynamic behaviors of cationic liposome-DNA complexes in inside and outside biomembrane models upon lipofection were investigated using the time-resolved quasi-elastic laser scattering (QELS) method. Inside and outside biomembrane models with similar phospholipid compositions to those in living cells were formed at a tetradecane/phosphate buffered saline (TD/PBS) interface. Cationic liposome-DNA complexes were injected into the buffer subphase, and their adsorption/desorption behaviors at the biomembrane models were monitored through changes in the interfacial tension. We found that the adsorption rate of the complexes increased 2.6 times more in the outside model than in the inside one. The adsorption rate of DNA alone did not show a remarkable difference from one side to the other; however, the adsorption rate of the cationic liposome alone showed a similar tendency to that of the liposome-DNA complex. These results indicated that the difference in lipid composition induced a different dynamic behavior of exogenous biomolecules and that the cationic liposomes played an important role in the faster incorporation of DNA into cells upon lipofection.     

Self-assembly and subsequent accumulation of lipid nanotubes at oil/water interfaces.

We utilized oil/water interfaces as a new field to produce lipid nanotubes (LNTs), which are formed by the self-assembly of lipid molecules, and possess hollow nanometer-wide cylindrical structures. Compared to the self-assembling field in bulk water, oil/water interfaces produced shorter lipids nanotubes less than 10 microm long more efficiently. In addition, we found that the oil/water interface accumulates lipid nanotubes spontaneously. This methodology is favorable to fabricate LNTs as new nano-fluidic devices, or sensors that require accumulation and alignment in two dimensions.     

Transient reflecting grating for sub-surface analysis: GHz ultrasonic and thermal spectroscopies and imaging

Picosecond time-resolved Transient Reflecting Grating (TRG) measurements are demonstrated for GHz ultrasonic and thermal spectroscopies of thin films and sub-surface regions of sub-m scale. The measurements should be tools for electrochemical interface monitoring and time-resolved imaging. Some results are presented to show ion-implantation-induced surface hardening and unusual heat-diffusion behavior near a silicon surface. A model describing potential dependence of TRG responses at an electrochemical interface is proposed. An image of photoexcited carrier density is compared with a thermal image for a He-ion-implanted silicon wafer to demonstrate the time-resolved imaging.