Highly stretchable, transparent cellulose/PVA hydrogel and its functions in temperature, pressure and strain sensing and energy harvesting.
A transparent and flexible cellulose/KOH composite ionic film (CKF) is fabricated as a humidity sensor. CKF exhibits high optical transmittance (87.14% at 550 nm), which has rarely been reported among humidity sensors as a result of the small pore size of the cellulose matrix caused by water-evaporation-induced dense packing and uniform distribution of amorphous KOH via simply soaking–drying. CKF also possesses flexibility and robust mechanical property. The conductive CKF shows fast and reversible real-time response to relative humidity (RH) in the 11.3–97.3% RH range with conductance varying over 200 times, response/recovery times of 6.0/10.8 s, which are shorter than the majority of the reported values, as well as a hysteresis error of 0.57%, which is significantly less than that reported in the literature. Furthermore, CKF is insensitive to both the temperature (10–70 °C) and pressure (0–120 kPa), indicating high selectivity as humidity sensors. In both the non-contact fingertip moisture detection and breathing rate detection, the flexible and transparent CKF-based humidity sensor responds favorably to RH change. Moreover, a flexible and transparent CKF-based wearable skin moisture detector is assembled to measure the moisture of human skin in different situations, whose measurement is very close to the commercial detector. The results offer real-time moisture information on human skin and demonstrate the potential of a CKF-based moisture detector as a promising modular component in integrated intelligent wearable equipment.
Despite significant advances in the past two decades, gene therapy is still in the stage of clinical trials worldwide mainly due to the lack of safe and efficient delivery vehicles for therapeutic nucleic acids. Among the various attempts to develop clinically applicable gene therapy, polymer-based nucleic acid delivery systems have attracted great interest, especially for the exciting RNAi-based gene therapy. Regarding in vivo nucleic acid delivery, in particular via intravenous injection, there are many extraand intracellular obstacles, some of which are conflicting. Virus-mimicking nucleic acid delivery systems that combine multiple and programmable functions are thought to be very promising for conquering these challenging barriers. In this review article, we highlight recent progress in stimuliresponsive polymers that have been applied in fabrication of non-viral multi-functional nucleic acid vehicles, which are categorized by the type of stimulus: reduction potential, pH, temperature, and others. In each section, intelligent pDNA delivery systems are introduced first, followed by summarizing various responsive polymer-based siRNA vehicles. Considering the great potential of RNAi-based gene therapy, we devote some space to the recent progress of multi-functional siRNA delivery systems. In addition, different requirements in designing polymer-based siRNA and pDNA carriers are also specified in this review.
Reproducing a tumor microenvironment consisting of blood vessels and tumor cells for modeling tumor invasion in vitro is particularly challenging. Here, we report an artificial blood vessel implanted 3D microfluidic system for reproducing transvascular migration of tumor cells. The transparent, porous and elastic artificial blood vessels are obtained by constructing polysaccharide cellulose-based microtubes using a chitosan sacrificial template, and possess excellent cytocompatibility, permeability, and mechanical characteristics. The artificial blood vessels are then fully implanted into the collagen matrix to reconstruct the 3D microsystem for modeling transvascular migration of tumor cells. Well-defined simulated vascular lumens were obtained by proliferation of the human umbilical vein endothelial cells (HUVECs) lining the artificial blood vessels, which enables us to reproduce structures and functions of blood vessels and replicate various hemodynamic parameters. Based on this model, the adhesion and transvascular migration of tumor cells across the artificial blood vessel have been well reproduced.
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