Double Stimuli‐Responsive Isoporous Membranes via Post‐Modification of pH‐Sensitive Self‐Assembled Diblock Copolymer Membranes

Double stimuli‐responsive membranes are prepared by modification of pH‐sensitive integral asymmetric polystyrene‐b‐poly(4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer membranes with temperature‐responsive poly(N‐isopropylacrylamide) (pNIPAM) by a surface linking reaction. PS‐b‐P4VP membranes are first functionalized with a mild mussel‐inspired polydopamine coating and then reacted via Michael addition with an amine‐terminated pNIPAM‐NH₂ under slightly basic conditions. The membranes are thoroughly characterized by nuclear magnetic resonance (¹H‐NMR), Fourier transform infrared spectroscopy and X‐ray‐induced photoelectron spectroscopy. Additionally dynamic contact angle measurements are performed comparing the sinking rate of water droplets at different temperatures. The pH‐ and thermo‐double sensitivities of the modified membranes are proven by determining the water flux under different temperature and pH conditions.     

Photoporation with Biodegradable Polydopamine Nanosensitizers Enables Safe and Efficient Delivery of mRNA in Human T Cells

Safe and efficient production of chimeric antigen receptor (CAR)-T cells is of crucial importance for cell-based cancer immunotherapy. Physical transfection methods have quickly gained in importance in the context of transfecting T-cells, since they are readily compatible with different cell types and a broad variety of cargo molecules. In particular, nanoparticle-sensitized photoporation has been introduced in recent years as a gentle yet efficient method to transiently permeabilize cells, allowing subsequent entry of external cargo molecules into the cells. Gold nanoparticles (AuNPs) have been used the most as photothermal sensitizers because they can easily form laser-induced vapor nanobubbles, a photothermal phenomenon that is shown to be particularly efficient for permeabilizing cells. However, as AuNPs are not biodegradable, clinical translation is hampered. Here, for the first time, the possibility to form laser-induced vapor nanobubbles from biocompatible polymeric nanoparticles is reported. Compared to electroporation, the most used physical transfection method for T cells, 2.5 times more living mRNA transfected human T cells are obtained via photoporation sensitized by polydopamine nanoparticles. This shows that photoporation is a viable approach for efficiently producing therapeutic engineered T-cells at a throughput easily exceeding 10⁵ cells per second.     

负载银纳米催化剂的聚多巴胺基微球的高效催化性能

利用聚多巴胺（PDA）的还原性和黏附性，成功制备了分别负载银（Ag）纳米催化剂的聚N-异丙基丙烯酰胺-聚多巴胺（PN@PDA/Ag）核壳型微球、聚苯乙烯-聚多巴胺（PS@PDA/Ag）核壳型微球和聚多巴胺（PDA/Ag）均质型微球。系统研究了PN@PDA/Ag、PS@PDA/Ag和PDA/Ag微球的微观结构、化学组成及Ag纳米颗粒的分布情况，并考察了在模型催化反应中，还原剂硼氢化钠（NaBH₄）和反应物对硝基苯酚（4-NP）摩尔比对微球催化性能的影响。结果表明，3种微球均成功负载了Ag纳米催化剂，相比于两种核壳型微球，PDA/Ag微球负载Ag纳米催化剂的含量最多。随着NaBH₄和4-NP摩尔比的增加，PN@PDA/Ag、PS@PDA/Ag和PDA/Ag微球对4-NP的转化率逐渐增大。在考察的摩尔比下，PDA/Ag微球均表现出比PN@PDA/Ag和PS@PDA/Ag微球更优异的催化性能。当摩尔比为500∶1时，PN@PDA/Ag、PS@PDA/Ag和PDA/Ag微球的表观反应速率常数（k_app）值分别为0.21min^-1、0.35min^-1和1.78min^-1。PDA/Ag微球的k_app值远高于文献报道的PDA/Ag微球k_app的最大值0.35min^-1。研究结果将为高效催化微球的设计和制备提供理论指导和实验基础。     

Metal-Free Hydrogen-Bonded Polymers Mimic Noble Metal Electrocatalysts

The most active and efficient catalysts for the electrochemical hydrogen evolution reaction (HER) rely on platinum, a fact that increases the cost of producing hydrogen and thereby limits the widespread adoption of this fuel. Here, a metal-free organic electrocatalyst that mimics the platinum surface by implementing a high work function and incorporating hydrogen-affine hydrogen bonds is introduced. These motifs, inspired from enzymology, are deployed here as selective reaction centres. It is shown that the keto-amine hydrogen-bond motif enhances the rate-determining step in proton reduction to molecular hydrogen. The keto-amine-functionalized polymers reported herein evolve hydrogen at an overpotential of 190 mV. They share certain key properties with platinum: a similar work function and excellent electrochemical stability and chemical robustness. These properties allow the demonstration of one week of continuous HER operation without notable degradation nor delamination from the carrier electrode. Scaled continuous-flow electrolysis is reported and 1 L net molecular hydrogen is produced within less than 9 h using 2.3 mg of polymer electrocatalyst.     

Biomimetic Assembly of a Polydopamine Layer on Graphene as an Electron Gate for Fluorescent MicroRNA Detection in Living Cells

A novel strategy was developed for microRNA detection based on the fluorescence quenching of polydopamine (PDA)-coated reduced graphene oxide (RGO) nanosheets (RGO@PDA). Compared with graphene oxide (GO), the reduction of GO and modification of the surface of RGO by PDA not only improve the stability, dispersity, biocompatibility, and cellular uptake without degeneration of the unique electronic properties of graphene, but also add an electron gate for harvesting electrons, as well as enabling efficient and forward electron transfer to avoid unwanted electron transfer and realize highly sensitive miRNA detection; thus a lower detection limit can be achieved in this sensing system. Remarkably, nanoprobes consisting of RGO@PDA and fluorescein-labeled single-stranded DNA can naturally enter cancer cells without the aid of transfection agents, as well as resisting enzymatic lysis and showing almost no effect on the cell viability. More importantly, intense and time-dependent fluorescence responses were observed from the important tumor marker microRNA-21 (miR-21) in living cells; thus suggesting that the proposed sensing platform shows great promise for applications in disease diagnosis and fundamental research into biochemistry.     

Simultaneously enhanced mechanical properties and thermal properties of ultrahigh‐molecular‐weight polyethylene with polydopamine‐coated α‐alumina platelets

Polydopamine (PDA) was employed to modify micrometric Al₂O₃ platelets to improve the interfacial compatibility between α‐Al₂O₃ powder and ultrahigh‐molecular‐weight polyethylene (UHMWPE). The structure of PDA‐coated Al₂O₃ and UHMWPE composites was investigated via Fourier transform infrared spectroscopy, scanning electron microscopy and X‐ray photoelectron spectroscopy. The thermal stability and mechanical performance of the samples were also evaluated. It is clear that UHMWPE/PDA‐Al₂O₃ composites exhibit better mechanical properties, higher thermal stability and higher thermal conductivity than UHMWPE/Al₂O₃ composites, owing to the good dispersion of Al₂O₃ powder in the UHMWPE matrix and the strong interfacial force between the macromolecules and the inorganic filler caused by the presence of PDA. The tensile strength and the tensile elongation at break of UHMWPE/PDA‐Al₂O₃ composite with 1 wt% PDA‐Al₂O₃ are 62.508 MPa and 462%, which are 1.96 and 1.98 times higher than those of pure UHMWPE, respectively. The thermal conductivity of UHMWPE/PDA‐Al₂O₃ composite increases from 0.38 to 0.52 W m^?1 K^?1 with an increase in the dosage of PDA‐Al₂O₃ to 20 wt%. The results show that the prepared PDA‐coated Al₂O₃ powder can simultaneously enhance the mechanical properties and thermal conductivity of UHMWPE. © 2018 Society of Chemical Industry     

Near-Infrared Photodriven Self-Sustained Oscillation of Liquid-Crystalline Network Film with Predesignated Polydopamine Coating

Movement is one of the vital features of living systems, and remote control of bioinspired soft robotic systems in a precise, contactless and harmless way is extremely desirable but challenging. A near-infrared (NIR) photodriven polymeric oscillator is designed and fabricated by selectively coating a mussel-inspired polydopamine (PDA) polymer layer on the surface of splay-aligned liquid crystalline network (LCN) film. The oscillating motions of the LCN oscillators can be facilely manipulated by tuning light intensity and film thickness. More importantly, the programmability of the PDA coating enables the oscillating behaviors of LCN film to be predesignated and finely adjusted by coating the film with PDA locally and repeatedly. The self-oscillating movement mechanism can be attributed to the temperature oscillation at the PDA-coated LCN film since it is alternatively exposed and sheltered to the NIR-light irradiations. Owing to over 50% NIR irradiation in solar spectrum, PDA-coated film is found to oscillate upon exposure of focused sunlight, presenting great potential in fabrication of solar power generation devices. This provides a versatile strategy to fabricate NIR-light-actuated polymeric oscillators, providing inspirations in the development of biological soft robots and advanced biomimetic devices.