Self‐Healing Polyester Urethane Supramolecular Elastomers Reinforced with Cellulose Nanocrystals for Biomedical Applications

Stretchable self‐healing urethane‐based biomaterials have always been crucial for biomedical applications; however, the strength is the main constraint of utilization of these healable materials. Here, a series of novel, healable, elastomeric, supramolecular polyester urethane nanocomposites of poly(1,8‐octanediol citrate) and hexamethylene diisocyanate reinforced with cellulose nanocrystals (CNCs) are introduced. Nanocomposites with various amounts of CNCs from 10 to 50 wt% are prepared using solvent casting technique followed by the evaluation of their microstructural features, mechanical properties, healability, and biocompatibility. The synthesized nanocomposites indicate significantly higher tensile modulus (approximately 36–500‐fold) in comparison to the supramolecular polymer alone. Upon exposure to heat, the materials can reheal, but nevertheless when the amount of CNC is greater than 10 wt%, the self‐healing ability of nanocomposites is deteriorated. These materials are capable of rebonding ruptured parts and fully restoring their mechanical properties. In vitro cytotoxicity test of the nanocomposites using human dermal fibroblasts confirms their good cytocompatibility. The optimized structure, self‐healing attributes, and noncytotoxicity make these nanocomposites highly promising for tissue engineering and other biomedical applications.     

Joint routing and channel assignment using online learning in cognitive radio networks

Cognitive radio networks (CRNs) are the solution for the problem of underutilizing the licensed spectrum for which there are more requests in the last couple of decades. In CRNs, Secondary users (SUs) are permitted to access opportunistically the licensed spectrum owned by primary users (PUs). In this paper, we address the problem of joint routing and channel assignment for several flows generated by source SUs to a given destination. We consider a more realistic model based on Markov modulated Poisson process for modeling the PUs traffic at each channel and the SUs try to exploit short lived spectrum holes between the PUs packets at the selected channel. The SUs want to cooperatively minimize the end-to-end delay of source SUs flows meanwhile the quality of service requirements of the PUs would be met. To consider partial observation of SUs about PUs activity at all channels and quick adaptation of SUs decisions to environment changes and cooperative interaction of SUs, we use decentralized partially observable markov decision process for modeling the problem. Then, an online learning based scheme is proposed for solving the problem. Simulation results show that the performance of the proposed method and the optimal method is close to each other. Also, simulation results show that the proposed method greatly outperforms related works at control of interference to the PUs while maintains the end-to-end delay of SU flows in a low level.

     

MXene Composite and Coaxial Fibers with High Stretchability and Conductivity for Wearable Strain Sensing Textiles

The integration of nanomaterials with high conductivity into stretchable polymer fibers can achieve novel functionalities such as sensing physical deformations. With a metallic conductivity that exceeds other solution‐processed nanomaterials, 2D titanium carbide MXene is an attractive material to produce conducting and stretchable fibers. Here, a scalable wet‐spinning technique is used to produce Ti₃C₂T_x MXene/polyurethane (PU) composite fibers that show both conductivity and high stretchability. The conductivity at a very low percolation threshold of ≈1 wt% is demonstrated, which is lower than the previously reported values for MXene‐based polymer composites. When used as a strain sensor, the MXene/PU composite fibers show a high gauge factor of ≈12900 (≈238 at 50% strain) and a large sensing strain of ≈152%. The cyclic strain sensing performance is further improved by producing fibers with MXene/PU sheath and pure PU core using a coaxial wet‐spinning process. Using a commercial‐scale knitting machine, MXene/PU fibers are knitted into a one‐piece elbow sleeve, which can track various movements of the wearer's elbow. This study establishes fundamental insights into the behavior of MXene in elastomeric composites and presents strategies to achieve MXene‐based fibers and textiles with strain sensing properties suitable for applications in health, sports, and entertainment.     

Inkjet Printing of Self‐Assembled 2D Titanium Carbide and Protein Electrodes for Stimuli‐Responsive Electromagnetic Shielding

2D titanium carbides (MXene) possess significant characteristics including high conductivity and electromagnetic interference shielding efficiency (EMI SE) that are important for applications in printed and flexible electronics. However, MXene‐based ink formulations are yet to be demonstrated for proper inkjet printing of MXene patterns. Here, tandem repeat synthetic proteins based on squid ring teeth (SRT) are employed as templates of molecular self‐assembly to engineer MXene inks that can be printed as stimuli‐responsive electrodes on various substrates including cellulose paper, glass, and flexible polyethylene terephthalate (PET). MXene electrodes printed on PET substrates are able to display electrical conductivity values as high as 1080 ± 175 S cm^?1, which significantly exceeds electrical conductivity values of state‐of‐the‐art inkjet‐printed electrodes composed of other 2D materials including graphene (250 S cm^?1) and reduced graphene oxide (340 S cm^?1). Furthermore, this high electrical conductivity is sustained under excessive bending deformation. These flexible electrodes also exhibit effective EMI SE values reaching 50 dB at films with thicknesses of 1.35 µm, which mainly originate from their high electrical conductivity and layered structure.     

Design of a highly efficient and water-tolerant sulfonic acid nanoreactor based on tunable ordered porous silica for the von Pechmann reaction

Among a number of different sulfonic acid nanoreactors prepared, 5 having both acidic sites and phenyl groups located inside the mesochannels of SBA-15 was shown to be the most active and reusable catalyst in the von Pechmann reaction. The mesochannels, and covalently anchored organic groups, provide a synergistic means of an efficient approach of the reactants to acidic sites, enough space for the subsequent cyclization, and suitable hydrophobicity to drive out the water byproduct.     

Fabrication of poly(ϵ-caprolactone)/paclitaxel (core)/chitosan/zein/multi-walled carbon nanotubes/doxorubicin (shell) nanofibers against MCF-7 breast cancer

In the present study, paclitaxel (PTX), multi-walled carbon nanotubes (MWCNTs), and doxorubicin (DOX) have been simultaneously doped into the poly(ϵ-caprolactone) (PCL)/chitosan/zein core-shell nanofibers to increase its cytotoxicity for MCF-7 breast cancers killing. The physico-chemical properties of synthesized nanofibers were determined by scanning electron microscope, Fourier-transform infrared spectroscopy, tensile strength, and degradation rate determinations. The in vitro release studies demonstrated the sustained release of drugs from core-shell nanofibrous scaffold. The cytotoxicity and compatibility of core-shell nanofibers were investigated by their treating with MCF-7 breast cancer cells and L929 normal cells, respectively. PCL/PTX/chitosan/zein/MWCNTs/DOX core-shell nanofibers containing 1 wt% MWCNTs, 100 μg ml⁻¹ DOX and 100 μg ml⁻¹ PTX had a high biocompatibility with a 84% MCF-7 cancer cells killing. The in vivo studies revealed the synergic effects of MWCNTs and anticancer drugs on the tumor inhibition. This method could be considered as a new way for developing of MWCNTs loaded-nanofibers for cancer treatment in future.     

Targeted Delivery of Anticancer Drug Loaded Charged PLGA Polymeric Nanoparticles Using Electrostatic Field

Pure positive electrostatic charges (PPECs) show suppressive effect on the proliferation and metabolism of invasive cancer cells without affecting normal tissues. PPECs are used for the delivery of drug-loaded polymeric nanoparticles (DLNs) capped with negatively charged poly(lactide-co-glycolide) (PLGA) and Poly(vinyl-alcohol) PVA into the tumor site of mouse models. The charged patch is installed on top of the skin in the mouse models' tumor region, and the controlled selective release of the drug is assayed by biochemical, radiological, and histological experiments on both tumorized models and normal rats' livers. It is found that DLNs synthesized by PLGA show great attraction to PPECs due to their stable negative charges, which would not degrade immediately in blood. The burst and drug release after less than 48h of this synthesized DLNs are 10% and 50%, respectively. These compounds can deliver the loaded-drug into the tumor site with the assistance of PPECs, and the targeted-retarded release will take place. Hence, local therapy can be achieved with much lower drug concentration (conventional chemotherapy [2 mg kg⁻¹] versus DLNs-based chemotherapy [0.75 mg kg⁻¹]) with negligible side effects in non-targeted organs. PPECs have many potential clinical applications for advanced-targeted chemotherapy with the lowest discernible side effects.     

Synthesis of a Photoaffinity‐Labeled (11Z)‐Retinal: Identification of Retinal/Rhodopsin Cross‐Linked Sites along the Visual‐Transduction Path

The retinal chromophore (11Z)‐3‐diazo‐4‐oxoretinal ( 1 ) with two photo‐labile moieties has been synthesized by semi‐hydrogenation of an 11‐yne precursor with activated Zn in aqueous media. Incorporation of 1 into opsin yielded diazoketo rhodopsin (DK‐Rh), which, upon bleaching, gave rise to intermediates batho‐Rh, lumi‐Rh, meta‐Rh, and meta‐II‐Rh corresponding to those of native Rh but at lower temperatures. Photoaffinity labeling of DK‐Rh and these bleaching intermediates showed that the ionone ring cross‐linked to Trp265 of helix F in DK‐Rh and batho intermediate, and to Ala169 of helix D in lumi, meta‐I, and meta‐II intermediates. These results demonstrate the occurrence of large conformational changes along the visual transduction path, which, in turn, is responsible for activation of the G‐protein.