Dynamic,Bioresponsive Hydrogels via Changes in DNA Aptamer Conformation

DNA aptamers are integrated into synthetic hydrogel networks with the aim of creating hydrogels that undergo volume changes when exposed to target molecules. Specifically, single‐stranded DNA aptamers in cDNA‐bound, extended state are incorporated into hydrogel networks as cross‐links, so that the nanoscale conformational change of DNA aptamers upon binding to target molecules will induce macroscopic volume decreases of hydrogels. Hydrogels incorporating adenosine triphosphate (ATP)–binding aptamers undergo controllable volume decreases of up to 40.3 ± 4.6% when exposed to ATP, depending on the concentration of DNA aptamers incorporated in the hydrogel network, temperature, and target molecule concentration. Importantly, this approach can be generalized to aptamer sequences with distinct binding targets, as demonstrated here that hydrogels incorporating an insulin‐binding aptamer undergo volume changes in response to soluble insulin. This work provides an example of bioinspired hydrogels that undergo macroscopic volume changes that stem from conformational shifts in resident DNA‐based cross‐links.     

Cycloaddition of 2′-azidoethyl glycosides to fullerene[C60] under ultrasonic irradiation

The reactions of fullerene[C₆₀] with 2′-azidoethyl 2,3,4,6-tetra-O-acetyl-α-d-mannopyranoside (2a) and 2′-azidoethyl 2,3,4,6-tetra-O-acetyl-β-d-galactopyranoside (2b) under ultrasonic irradiation cause the cycloaddition of 2′-azidoethyl glycosides to fullerene[C₆₀] and lead to d-glycosyl fullerene[C₆₀] derivatives 3a and 3b, respectively. The glycosyl fullerene[C₆₀] derivatives were characterized by ¹H and ¹³C NMR, UV–vis, FAB-MS, FT-IR spectra and were a 1:1 glycoside fullerene [C₆₀]-adduct.     

Targeted Gene Delivery via PEI Complexed with an Antibody

Stable carriers are required for gene delivery. The use of polyethyleneimine (PEI) has been researched extensively; however, it is not suitable for targeted gene delivery to specific cells. To provide a targeting ability of the specific antibody to PEI, two repeats of Fc-binding domain of protein G (C2) were utilized. The constructed protein containing C2 could bind to a specific antibody and form a larger complex with plasmid DNA/PEI complex. The specific antibody to cell surface protein was bound to the complex through the use of C2 domain, and it was added to cells. As the result, the efficient expression of delivered reporter gene could be realized.     

Pluronic/Polyethylenimine Shell Crosslinked Nanocapsules with Embedded Magnetite Nanocrystals for Magnetically Triggered Delivery of siRNA

Pluronic/polyethylenimine shell crosslinked nanocapsules with embedded magnetite nanocrystals (PPMCs) were developed for magnetically triggered delivery of siRNA. The positively charged PPMCs formed stable nanosized polyelectrolyte complexes via electrostatic interactions with negatively charged siRNA‐polyethylene glycol conjugate (siRNA‐s‐s‐PEG) that was linked via a cleavable disulfide linkage. PPMC/siRNA‐s‐s‐PEG polyelectrolyte complexes were efficiently taken up by cancer cells upon exposure to a magnet, thereby enhancing intracellular uptake and silencing effect of siRNA. The present study suggests that these novel nanomaterials could be potentially utilized for magnetically triggered delivery of various nucleic acid‐based therapeutic agents.

     

Core-shell-structured magnetic ternary nanocubes

We report a novel core-shell-structured ternary nanocube of MnZn ferrite synthesized by controlling the reaction temperature and composition in the absence of conventionally used reducing agents. The highly monodispersed core-shell structure consists of an Fe(3)O(4) core and an MnZn Ferrite shell. The observation of a Moire? pattern indicates that the core and the shell are two highly crystalline materials with slightly different lattice constants that are rotated relative to each other by a small angle. The ternary core-shell nanocubes display magnetic properties regulated by a combination of the core-shell composition and exhibit an increased coercivity and field-cooled/zero-field-cooled characteristics drastically different from those of regular MnZn ferrite nanoparticles. The ability to engineer the spatial nanostructures of ternary magnetic nanoparticles in terms of shape and composition offers atomic-level versatility in fine-tuning the nanoscale magnetic properties.     

Capacitance of a coaxial line terminated by a gap

Capacitance of a coaxial line terminated by a gap is investigated. An electrostatic boundary-value problem of the coaxial line terminated by a gap is rigorously solved based on the Fourier sine transform, mode matching technique, and superposition. The capacitance of the coaxial line is represented in a fast-convergent series and computed in terms of the gap geometry and the gap permittivity.     

Effects of controlling Cu spacer inter-diffusion by diffusion barriers on the magnetic and electrical stability of GMR spin-valve devices

An ultra-thin Co or CoFe diffusion barrier inserted at the NiFe/Cu interfaces was revealed to effectively control the electrical and magnetic stability of NiFe/Cu/NiFe-based giant magnetoresistance (GMR) spin-valve spintronics devices (SVSDs) operating at high current density. It was found that the activation energy, E_a, related to the electromigration (EM)-induced inter-diffusion process for the patterned NiFe(3)/Cu(2)/NiFe(3 nm) magnetic multi-layered devices (MMLD) was remarkably increased from 0.52±0.2 eV to 1.17±0.16 eV after the insertion of an ultra-thin Co diffusion barrier at the NiFe/Cu interfaces. The dramatically reduced “current shunting paths” from the Cu spacer to the NiFe thin films and the development of “self-healing process” resulted from the effectively restrained Cu inter-diffusion (intermixing with Ni atoms) due to the diffusion barriers were found to be primarily responsible for the improvement of electrical and magnetic stability. The further investigation on the effects of controlling Cu spacer inter-diffusion by diffusion barriers on the EM and thermomigration (TM)-induced magnetic degradation was carried out for the NiFe/(Co or Co₉₀Fe₁₀)/Cu/(Co or Co₉₀Fe₁₀)/NiFe/FeMn top exchange-biased GMR (EBGMR) SVSDs electrically stressed under the applied DC current density of J=2.5×10⁷ A/cm² (I=16.5∼17.25 mA). It was clearly confirmed that the Co and the CoFe diffusion barriers effectively control the Cu spacer inter-diffusion resulting in a smaller reduction in both GMR ratio and exchange bias field of the EBGMR SVSDs. Furthermore, it was obviously observed that the effects of CoFe diffusion barrier on controlling the Cu spacer inter-diffusion are more significant than that of Co. The effectively reduced Mn atomic inter-diffusion at the NiFe/FeMn interface and the well-maintained interfacial spin-dependent scattering resulted from the control of EM and TM-induced Cu spacer inter-diffusion were the main physical reasons for the significant improvement of magnetic and electrical degradation of top EBGMR SVSDs.