The Design of Polymer‐based Nanocarriers for Effective Transdermal Delivery

This study reports a facile and practical means to non‐invasively deliver biologically active ingredients through the skin using polymer‐based nanocarriers. For this, polymer nanocapsules were fabricated with different surface charges as well as glass transition temperatures and we observed their ability to deliver the encapsulated active ingredient, coenzyme Q10, through the skin layer. Direct imaging of a probe molecule, Nile Red, and a matrix polymer labeled with fluorescence moiety, Lucifer Yellow, allowed us to demonstrate that the probe molecule readily permeates into the deep skin, while the matrix polymer stays in the stratum corneum layer due to electrostatic interactions. Quantitative characterization of the penetrating amount of coenzyme Q10 using the Frantz cell method proved that, to achieve improved delivery efficiency, the nanocapsule should have a low glass transition temperature as well as positive surface charges.

     

\mathfrak D -parallelism of normal and structure Jacobi operators for hypersurfaces in complex two-plane Grassmannians

In this paper, we give non-existence theorems for Hopf hypersurfaces in complex two-plane Grassmannians $G_2(\mathbb{C }^{m+2})$ with $\mathfrak D $ -parallel normal Jacobi operator ${\bar{R}}_N$ and $\mathfrak D $ -parallel structure Jacobi operator $R_{\xi }$ if the distribution $\mathfrak D $ or $\mathfrak D ^{\bot }$ component of the Reeb vector field is invariant by the shape operator, respectively.     

Hopf hypersurfaces in complex two-plane Grassmannians with generalized Tanaka-Webster \mathfrak{D}^ \bot-parallel structure Jacobi operator

Regarding the generalized Tanaka-Webster connection, we considered a new notion of \(\mathfrak{D}^ \bot\) -parallel structure Jacobi operator for a real hypersurface in a complex two-plane Grassmannian G ₂(? ^m+2) and proved that a real hypersurface in G ₂(? ^m+2) with generalized Tanaka-Webster \(\mathfrak{D}^ \bot\) -parallel structure Jacobi operator is locally congruent to an open part of a tube around a totally geodesic quaternionic projective space ?P ⁿ in G ₂(? ^m+2), where m = 2n.     

Real hypersurfaces in complex two-plane Grassmannians with certain commuting condition II

Lee, Kim and Suh (2012) gave a characterization for real hypersurfaces M of Type (A) in complex two plane Grassmannians G ₂(? ^m+2) with a commuting condition between the shape operator A and the structure tensors φ and φ ₁ for M in G ₂(? ^m+2). Motivated by this geometrical notion, in this paper we consider a new commuting condition in relation to the shape operator A and a new operator φφ ₁ induced by two structure tensors φ and φ ₁. That is, this commuting shape operator is given by φφ ₁ A = A φφ ₁. Using this condition, we prove that M is locally congruent to a tube of radius r over a totally geodesic G ₂(? ^m+1) in G ₂(? ^m+2).     

Growth of high quality a-plane GaN epi-layer on r-plane sapphire substrates with optimization of multi-buffer layer

Nonpolar (1 1–2 0) a-plane GaN films have been grown using the multi-buffer layer technique on (1–1 0 2) r-plane sapphire substrates. In order to obtain epitaxial a-plane GaN films, optimized growth condition of the multi-buffer layer was investigated using atomic force microscopy, high resolution X-ray diffraction, and transmission electron microscopy measurements. The experimental results showed that the growth conditions of nucleation layer and three-dimensional growth layer significantly affect the crystal quality of subsequently grown a-plane GaN films. At the optimized growth conditions, omega full-width at half maximum values of (11–20) X-ray rocking curve along c- and m-axes were 430 and 530 arcsec, respectively. From the results of transmission electron microscopy, it was suggested that the high crystal quality of the a-plane GaN film can be obtained from dislocation bending and annihilation by controlling of the island growth mode.     

Hydrothermal synthesis of Bi2Te3 nanowires through the solid-state interdiffusion of Bi and Te atoms on the surface of Te nanowires

Polycrystalline Bi₂Te₃ nanowires were prepared by a hydrothermal method that involved inducing the nucleation of Bi atoms reduced from BiCl₃ on the surface of Te nanowires, which served as sacrificial templates. A Bi–Te alloy is formed by the interdiffusion of Bi and Te atoms at the boundary between the two metals. The Bi₂Te₃ nanowires synthesized in this study had a length of 3–5 μm, which is the same length as that of the Te nanowires, and a diameter of 300–500 nm, which is greater than that of the Te nanowires. The experimental results indicated that volume expansion of the Bi₂Te₃ nanowires was a result of the interdiffusion of Bi and Te atoms when Bi was alloyed on the surface of the Te nanowires. The morphologies of Bi₂Te₃ are strongly dependent on the reaction conditions such as the temperature and the type and concentration of the reducing agent. The morphologies, crystalline structure and physical properties of the product were analyzed by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and X-ray photoelectron spectroscopy (XPS).     

Mechanical properties of amphiphilic urethane acrylate ionomer hydrogels having heterophasic gel structure

Amphiphilic urethane acryale hydrogels containing ionic groups (dimethylolpropionic acid) were prepared by varying the molecular weight of the soft segment (polyether type) and the type of diisocyanate, and their mechanical properties were examined. They showed heterophasic gel structure composed of ionic hard domains induced by aggregation of the ionic groups and polyether soft domains comprising the urethane acrylate network. This heterophasic structure could be confirmed by dynamic mechanical analysis (DMA) and by wide-angle X-ray scattering analysis (WAXS); the crystallinity detected by WAXS and the transition peak of the ionic hard domains detected by DMA strongly suggested that there were ionic aggregates. These ionic aggregates acted as reinforcing fillers in the network, which eventually enhanced the tensile strength of the hydrogels. Above all, the tensile properties of the hydrogels were of interest in that the trends of the stress-strain curves were consistent with the rubbery ones. It is believed that the higher purity of the polyether soft domains resulted from the heterophasic gel structure imparting further elastomeric properties on the network. Received: 31 July 1998 Accepted in revised form: 15 October 1998     

Enhanced transdermal delivery by using electrostatically interactive chitosan nanocapsules

This paper describes a useful means of noninvasively enhancing transdermal delivery efficiency. For this, chitosan nanocapsules with positive surface charges were fabricated by using the in situ precipitation method. These nanocapsules cannot only have an ability to encapsulate the drug molecule (this study used riboflavin 5′-monophosphate), but also electrotatically interact with the stratum corneum layer. To demonstrate this, fluorescence-labeled polymer nanoparticles with different particle sizes as well as surface charges were topically applied onto the skin and their distribution was directly imaged. This demonstration experiment allowed us to figure out that once the nanocapsules were provided with positive surface charges, they readily deposited into the stratum corneum layer due to the electrostatic interaction. Further quantitative characterization of the penetrating amount of riboflavin 5′-monophosphate by using the Frantz diffusion cell method showed that our chitosan nanocapsule system effectively improved transdermal delivery efficiency.     

Synthesis of novel conjugated polymer based on cyclopenta[def]phenanthrene and vinylene with strong interchain interaction

In this study, a novel conjugated polymer, poly(4,4‐bis(2‐ethylhexyl)‐4H‐cyclopenta[def]phenanthrene‐2,6‐vinylene) (PCPPV) has been synthesized and characterized. For the polymerization, Gilch's reaction was applied for the first time with the cyclopenta[def]phenanthrene system. The absorption and emission spectra of PCPPV are red‐shifted about 40–50 nm due to the vinylene units when compared with those of poly(2,6‐(4,4‐bis(2‐ethylhex‐yl)‐4H‐cyclopenta[def]phenanthrene)) (PCPP). The solid‐state fluorescence is significantly broadened, possibly due to π–π interactions introduced by the phenanthrene and vinylene moieties. In solution, as the concentration of polar solvent increased, the photoluminescence (PL) intensity decreased due to quenching and aggregation by the interchain interactions between the conjugated backbones. After annealing the film at 80 °C, the PL and electroluminescence (EL) emission spectra exhibited also the quenching and aggregation effects indicating the interchain interactions of PCPPV. The large number of aromatic rings in a unit and the increased planarity achieved through introduction of vinylene units are able to give interchain interactions stronger than fluorene or phenylene units. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5068–5077, 2009