Research articles

We developed pDNA/polysaccharide complexes suitable for reverse transfection (RTF) and investigated their transfection mechanisms. The pDNA/chitosan/hyaluronic acid ternary complexes showed excellent transfection efficiency in RTF compared with the conventional forward transfection (FTF). The ternary complexes were taken up via macropinocytosis in RTF. Furthermore, the ternary complexes in RTF were transported to late endosomes via microtubules, and were remarkably accumulated in the nucleus. These results suggest that the cell transfection efficiency of the ternary complexes in RTF was enhanced by their efficient delivery to the nucleus via late endosomes.

Molecular dynamics simulation of chitosan and anionic oligosaccharides was conduced to elucidate the formation mechanism and structure of polyion complex (PIC) of polysaccharides. The association of oligosaccharides with scrambled structure indicated that PIC of polysaccharides takes on the structure of “Scrambled egg model”. The formation of hydrogen bond between deprotonated chitosan and anionic oligosaccharides suggested that hydrogen bonds contribute to the stabilization of PIC under neutral condition.

The surface glass transition temperature (T_g) of polymer materials is believed to be significantly lower than the bulk value. We prepared a molecularly flat substrate of poly(methyl methacrylate) (PMMA) by thermally imprinting a PMMA plate with mica, on which polystyrene-b-PMMA was deposited by the Langmuir-Blodgett technique in a dilute state, and the thermal stability of the surface was evaluated by in situ high-temperature atomic force microscopy. Both the PMMA chains deposited on the plate and of the surface of the plate started to move close to the bulk PMMA T_g.

Photoisomerization of doped azobenzene (AB) caused “photoinduced plasticization” effects such as reductions in the glass transition temperature (T_g) and Young’s modulus of the matrix polymer. The mechanism of the reduction in T_g and Young’s modulus of polycarbonate (PC) was investigated by comparing the two values with the characteristic times of the isomerization reactions. The sum of the characteristic times of trans→cis and cis→trans conversion is related to the repeating isomerization rate. The faster repeating isomerization enhanced the free volume of PC, resulting in the reduction in T_g and Young’s modulus.

We visualized the spatial inhomogeneity of chain orientation on the submicron scale in high-density polyethylene associated with strain-induced density fluctuations using STXM and USAXS/SAXS/WAXD. Real-space images of the density fluctuations were obtained with STXM at the strain where a butterfly pattern was observed with USAXS. STXM observation also revealed that the chains in the low-density region were more often oriented parallel to the stretching direction than those in the high-density region.