The present work was focused on the preparation and characterization of polyelectrolyte complex (PEC) fibers based on the natural oppositely charged biopolymers, chitosan and sodium hyaluronate, via a freeze-drying method. The physical structure and chemical properties of the freeze-dried fibers were characterized by means of Fourier transform infrared spectroscopy (FT-IR), solid-state 13C nuclear magnetic resonance (13C-NMR) and X-ray diffraction (XRD). The morphology, size, and surface structure of the freeze-dried PEC fibers were observed by means of scanning electron microscopy (SEM). An indirect in vitro cytotoxicity test showed the extracts of fibers had no significant effects on cell viability. Moreover, an in vitro cytocompatibility test exhibited cell population and spreading tendency, suggesting the fibers were non-toxic to L929 cells. All the results indicated that such freeze-dried PEC fibers might have potential applications in tissue engineering scaffolds.
Abstract Reactive oxygen species (ROS) have become an effective tool for tumor treatment. The combination of photodynamic therapy (PDT) and chemodynamic therapy (CDT) takes advantage of various ROS and enhances therapeutic effects. However, the activation of CDT usually occurs before PDT, which hinders the sustained maintenance of hydroxyl radicals (⋅OH) and reduces the treatment efficiency. Herein, we present a light‐triggered nano‐system based on molecular aggregation regulation for converting cancer therapy from PDT/photothermal therapy (PTT) to a long‐lasting CDT. The ordered J‐aggregation enhances the photodynamic properties of the cyanine moiety while simultaneously suppressing the chemodynamic capabilities of the copper‐porphyrin moiety. Upon light irradiation, Cu‐PCy JNPs demonstrate strong photodynamic and photothermal effects. Meanwhile, light triggers a rapid degradation of the cyanine backbone, leading to the destruction of the J‐aggregation. As a result, a long‐lasting CDT is sequentially activated, and the sustained generation of ⋅OH is observed for up to 48 hours, causing potent cellular oxidative stress and apoptosis. Due to their excellent tumor accumulation, Cu‐PCy JNPs exhibit effective in vivo tumor ablation through the converting therapy. This work provides a new approach for effectively prolonging the chemodynamic activity in ROS‐based cancer therapy.
A unique core–shell architecture of dual-phase FeCo based nanoparticles@heteroatom-doped carbon microspheres (FeCo@C MS) has been prepared which exhibits excellent performance in the electrochemical oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER).
A biocomposite of hydroxyapatite (HAp) with electrospun nanofibrous scaffolds was prepared by using chitosan/polyvinyl alcohol (CS/PVA) and N-carboxyethyl chitosan/PVA (CECS/PVA) electrospun membranes as organic matrix, and HAp was formed in supersaturated CaCl2 and KH2PO4 solution. The influences of carboxylic acid groups in CECS/PVA fibrous scaffold and polyanionic additive poly(acrylic acid) (PAA) in the incubation solution on the crystal distribution of the HAp were investigated. Field-emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), wide-angle X-ray diffraction (WAXD), and Fourier transform infrared (FTIR) were used to characterize the morphology and structure of the deposited mineral phase on the scaffolds. It was found that addition of PAA to the mineral solution and use of matrix with carboxylic acid groups promoted mineral growth and distribution of HAp. MTT testing and SEM imaging from mouse fibroblast (L929) cell culture revealed the attachment and growth of mouse fibroblast on the surface of biocomposite scaffold, and that the cell morphology and viability were satisfactory for the composite to be used in bioapplications.
Developing an efficient and durable oxygen reduction electrocatalyst is critical for clean-energy technology, such as fuel cells and metal–air batteries. In this study, we developed a facile strategy for the preparation of flexible, porous, and well-dispersed metal–heteroatom-doped carbon nanofibers by direct carbonization of electrospun Zn/Co-ZIFs/PAN nanofibers (Zn/Co-ZIFs/PAN). The obtained Zn/Co and N co-doped porous carbon nanofibers carbonized at 800 °C (Zn/Co–N@PCNFs-800) presented a good flexibility, a continuous porous structure, and a superior oxygen reduction reaction (ORR) catalytic activity to that of commercial 20 wt% Pt/C, in terms of its onset potential (0.98 V vs. RHE), half-wave potential (0.89 V vs. RHE), and limiting current density (− 5.26 mA cm−2). In addition, we tested the suitability and durability of Zn/Co–N@PCNFs-800 as the oxygen cathode for a rechargeable Zn–air battery. The prepared Zn–air batteries exhibited a higher power density (83.5 mW cm−2), a higher specific capacity (640.3 mAh g−1), an excellent reversibility, and a better cycling life than the commercial 20 wt% Pt/C + RuO2 catalysts. This design strategy of flexible porous non-precious metal-doped ORR electrocatalysts obtained from electrospun ZIFs/polymer nanofibers could be extended to fabricate other novel, stable, and easy-to-use multi-functional electrocatalysts for clean-energy technology.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)