The mixing effect of amine and carboxyl groups on electrorheological properties and its analysis by in situ FT-IR under an electric field

Low-filled suspensions of α-chitin nanorods for electrorheological applications

Highly anisometric α-chitin nanoparticles isolated by TEMPO-oxidation were investigated as filler for electrorheological fluids. The dimensions of rod-like particles were determined by AFM and cryo-TEM methods. The rheological behavior of α-chitin nanoparticles in polydimethylsiloxane changes from viscous to elastic under electric field. The yield stress reaches about 220 Pa at 7 kV/mm for 1.0 wt% fluid. Despite the nanosize of particles, the suspensions sedimentation ratio was found to be low (~23%). The electrorheological behavior of the fluids was discussed in terms of the Mason numbers. The stability of fluids response under switching electric field was shown. The activation energy of polarization processes in suspensions was calculated as 58 ± 2 and 64 ± 1 kJ/mol for 0.5 and 1.0 wt% filler content from the impedance spectra. The high aspect ratio (~70) and dielectric permittivity result in high electrorheological activity of α-chitin suspensions at extremely low concentrations (≤1.0 wt%).

Enhanced proton transport properties of sulfonated polyarylene ether nitrile (SPEN) with moniliform nanostructure UiO-66-NH2/CNT

Metal-organic frameworks (MOFs) have been widely investigated for their porosity and functional diversity. Inspired by the flexible designability of MOFs, UiO-66-NH2/CNT with moniliform nanostructure was designed and synthesized successfully. SPEN@UiO-66-NH2/CNT composite proton exchange membranes were prepared by loaded UiO-66-NH2/CNT into sulfonated polyarylene ether nitrile (SPEN). Due to the addition of UiO-66-NH2/CNT, all the properties of composite proton exchange membranes were improved. The composite membranes exhibit excellent thermal stability and dimensional stability. The tensile strength of the composite membranes was improved about twofold compared to that of recast SPEN membrane, which was contributed by the interlaced property and rigid structure of UiO-66-NH2/CNT. Especially, the proton conductivity of the composite membranes was greatly facilitated by the additional proton acceptors and donors provided by the abundant amino groups and carboxyl groups in UiO-66-NH2/CNT. Furthermore, the methanol permeability of SPEN@UiO-66-NH2/CNT reduced consistently (from 6.13 to 0.96 × 10−7 cm2 s−1), which was much lower than that of Nafion membrane (21.36 × 10−7 cm2 s−1). All the results suggest that the design of multifunctional nanofillers based on the skeleton structure of MOFs could provide a new strategy to enhance the performance of PEMs.

The Alginate Layer for Improving Doxorubicin Release and Radiolabeling Stability of Chitosan Hydrogels

PURPOSE

Chitosan hydrogels (CSH) formed through ionic interaction with an anionic molecule are suitable as a drug carrier and a tissue engineering scaffold. However, the initial burst release of drugs from the CSH due to rapid swelling after immersing in a biofluid limits their wide application as a drug delivery carrier. In this study, alginate layering on the surface of the doxorubicin (Dox)-loaded and I-131-labeled CSH (DI-CSH) was performed. The effect of the alginate layering on drug release behavior and radiolabeling stability was investigated.

METHODS

Chitosan was chemically modified using a chelator for I-131 labeling. After labeling of I-131 and mixing of Dox, the chitosan solution was dropped into tripolyphosphate (TPP) solution using an electrospinning system to prepare spherical microhydrogels. The DI-CSH were immersed into alginate solution for 30 min to form the crosslinking layer on their surface. The formation of alginate layer on the DI-CSH was confirmed by Fourier transform infrared spectroscopy (FT-IR) and zeta potential analysis. In order to investigate the effect of alginate layer, studies of in vitro Dox release from the hydrogels were performed in phosphate buffered in saline (PBS, pH 7.4) at 37 °C for 12 days. The radiolabeling stability of the hydrogels was evaluated using ITLC under different experimental condition (human serum, normal saline, and PBS) at 37 °C for 12 days.

RESULTS

Formatting the alginate-crosslinked layer on the CSH surface did not change the spherical morphology and the mean diameter (150 ± 10 μm). FT-IR spectra and zeta potential values indicate that alginate layer was formed successfully on the surface of the DI-CSH. In in vitro Dox release studies, the total percentage of the released Dox from the DI-CSH for 12 days were 60.9 ± 0.8, 67.3 ± 1.4, and 71.8 ± 2.5 % for 0.25, 0.50, and 1.00 mg Dox used to load into the hydrogels, respectively. On the other hand, after formatting alginate layer, the percentage of the released Dox for 12 days was decreased to 47.6 ± 1.4, 51.1 ± 1.4, and 57.5 ± 1.6 % for 0.25, 0.50, and 1.00 mg Dox used, respectively. The radiolabeling stability of DI-CSH in human serum was improved by alginate layer.

CONCLUSIONS

The formation of alginate layer on the surface of the DI-CSH is useful for improving the drug release behavior and radiolabeling stability.