Conductive hydrogels have emerged as fascinating materials applied in flexible electronics because of their integrated conductivity and mechanical flexibility. However, the large amounts of water in conductive hydrogels inevitably freeze at subzero temperature, causing a reduction of their ionic transport ability and elasticity. Herein, the bioinspired antifreezing agents—zwitterionic osmolytes (e.g., betaine, proline) are first proposed to prevent ammonium chloride‐containing Ca‐alginate/polyacrylamide hydrogels from freezing. With a facile one‐pot solvent displacement method, the zwitterionic osmolytes can displace the water molecules inside the hydrogels. Due to the excellent freeze tolerance of zwitterionic osmolytes, the resulting zwitterionic osmolyte‐based hydrogels exhibit outstanding ionic conductivity (up to ≈2.7 S m−1) at −40 °C, which exceeds the conductivities of most reported conductive hydrogels. Meanwhile, they present stable mechanical flexibility over a wide temperature range (−40 to 25 °C). More importantly, two types of the resulting hydrogel‐based flexible electronics, including a capacitive sensor and a resistive sensor, can maintain their response function at −40 °C. This work offers a new solution to fabricate conductive hydrogels with antifreezing ability, which can broaden the working temperature range of flexible electronics.
The development of environmentally friendly and highly efficient antifouling coatings is vastly desirable in the marine industry. Herein, we prepared a novel amphiphilic block copolymer that combined hydrophilic polyvinylpyrrolidone (PVP) with hydrophobic poly(1-(1H,1H,2H,2H-perfluorodecyloxy)-3-(3,6,9-trioxadecyloxy)-propan-2-yl acrylate) (PFA) and polydimethylsiloxane (PDMS). The amphiphilic copolymer (PVP−PFA−PDMS) was blended into a cross-linked PDMS matrix to form a set of controlled surface composition and surface-renewal coatings with efficient antifouling and fouling-release properties. These coatings incorporated the biofouling settlement resistance ability attributed to the hydrophilic PVP segments and the reduced adhesion strength attributed to the low surface energy of fluorine−siliconcontaining segments. As expected, the coatings showed an excellent antifouling performance against bacteria and marine unicellular Navicula parva diatoms (98.1 and 98.5% of reduction, respectively) and fouling-release performance against pseudobarnacle adhesion (84.3% of reduction) compared to the pristine PDMS coating. Moreover, a higher-content PVP-based coatings presented higher ability to resist biofouling adhesion. The nontoxic antifouling coating developed in this paper hold the potential to be applied in a variety of marine industrial facilities.
Currently,
the state-of-the-art cryoprotectants for cell cryopreservation
have bottleneck problems (such as cytotoxicity), which place enormous
logistical limitations to the development of regenerative medicine.
In this work, a first alginate polymer-based approach for human chondrocyte
cryopreservation is reported. Combined with zwitterionic betaine,
a natural osmoprotectant to offer intracellular protection, this alginate
polymer-based approach can achieve ∼90% cryopreservation efficiency.
Because of the biocompatibility of alginate polymer and betaine, this
approach can easily retrieve the post-thaw cells without traditional
multistep cryoprotectant washing procedures, which is highly favorable
to cell therapy. Meanwhile, because of the feasible and mild gelation
process of alginate polymer, this approach can also directly encapsulate
the post-thaw cells into hydrogels without cryoprotectant removal,
which is highly useful to tissue engineering. Moreover, these hydrogels
exhibit tunable mechanical properties and can form variable shapes
and sizes of scaffolds to inject into the patient’s defect
sites. After encapsulating post-thaw cells, these hydrogels can maintain
high cell viability (∼90%) and normal cellular functions for
at least 14 days. This work provides a step-change in cryopreservation
of cells to be directly used in cell-based applications and may realize
promising cellular therapy products that can integrate preservation
with clinical practice.
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