Chemically Detachable Polyelectrolyte Multilayer Platform for Cell Sheet Engineering

International audienc

Degradable block copolymer-derived nanoporous membranes and their applications

Nanoporous membranes exhibit wide applications in the fields of energy, environmental, and analytical science. Among all nanoporous membrane materials, degradable block copolymers (DBCP) have attracted attention due to their well-defined nanopores, high porosity, narrow pore size distributions, and abundant functional end-groups. In this review, the fabrication strategies of DBCP-derived nanoporous membranes are described first, including degradation of sacrificial blocks, cleavage of block-linkers, and the removal of pore-forming agents. Secondly, the extensive applications of DBCP-derived nanoporous membranes are discussed. Generally, they have been used for separation membranes, nanotemplates, etched masks, catalysis, electronics, biomedicine, etc. Finally, the possible development directions and challenges of DBCP-derived nanoporous membranes in various applications are proposed

Detecting topology freezing transition temperature of vitrimers by AIE luminogens.

Vitrimers are one kind of covalently crosslinked polymers that can be reprocessed. Topology freezing transition temperature (Tv) is vitrimer's upper limit temperature for service and lower temperature for recycle. However, there has been no proper method to detect the intrinsic Tv till now. Even worse, current testing methods may lead to a misunderstanding of vitrimers. Here we provide a sensitive and universal method by doping or swelling aggregation-induced-emission (AIE) luminogens into vitrimers. The fluorescence of AIE-luminogens changes dramatically below and over Tv, providing an accurate method to measure Tv without the interference of external force. Moreover, according to this method, Tv is independent of catalyst loading. The opposite idea has been kept for a long time. This method not only is helpful for the practical application of vitrimers so as to reduce white wastes, but also may facilitate deep understanding of vitrimers and further development of functional polymer materials

Detecting topology freezing transition temperature of vitrimers by AIE luminogens.

Vitrimers are one kind of covalently crosslinked polymers that can be reprocessed. Topology freezing transition temperature (Tv) is vitrimer's upper limit temperature for service and lower temperature for recycle. However, there has been no proper method to detect the intrinsic Tv till now. Even worse, current testing methods may lead to a misunderstanding of vitrimers. Here we provide a sensitive and universal method by doping or swelling aggregation-induced-emission (AIE) luminogens into vitrimers. The fluorescence of AIE-luminogens changes dramatically below and over Tv, providing an accurate method to measure Tv without the interference of external force. Moreover, according to this method, Tv is independent of catalyst loading. The opposite idea has been kept for a long time. This method not only is helpful for the practical application of vitrimers so as to reduce white wastes, but also may facilitate deep understanding of vitrimers and further development of functional polymer materials

Bioinspired light-driven chloride pump with helical porphyrin channels

Abstract Halorhodopsin, a light-driven chloride pump, utilizes photonic energy to drive chloride ions across biological membranes, regulating the ion balance and conveying biological information. In the light-driven chloride pump process, the chloride-binding chromophore (protonated Schiff base) is crucial, able to form the active center by absorbing light and triggering the transport cycle. Inspired by halorhodopsin, we demonstrate an artificial light-driven chloride pump using a helical porphyrin channel array with excellent photoactivity and specific chloride selectivity. The helical porphyrin channels are formed by a porphyrin-core star block copolymer, and the defects along the channels can be effectively repaired by doping a small number of porphyrins. The well-repaired porphyrin channel exhibits the light-driven Cl− migration against a 3-fold concentration gradient, showing the ion pumping behavior. The bio-inspired artificial light-driven chloride pump provides a prospect for designing bioinspired responsive ion channel systems and high-performance optogenetics

Fabrication of CO2 Facilitated Transport Channels in Block Copolymer through Supramolecular Assembly

In this paper, the molecule 12-amidine dodecanoic acid (M) with ending groups of carboxyl and amidine groups respectively was designed and synthesized as CO2-responsive guest molecules. The block copolymer polystyrene-b-polyethylene oxide (PS-b-PEO) was chosen as the host polymer to fabricate a composite membrane through H-bonding assembly with guest molecule M. We attempted to tune the phase separation structure of the annealed film by varying the amount of M added, and investigated the nanostructures via transmission electron microscope (TEM), fourier transform infrared (FT-IR) etc. As a result, a reverse worm-like morphology in TEM image of bright PS phase in dark PEO/M matrix was observed for PS-b-PEO/M1 membrane in which the molar ratio of EO unit to M was 1:1. The following gas permeation measurement indicated that the gas flux of the annealed membranes dramatically increased due to the forming of ordered phase separation structure. As we expected, the obtained composite membrane PS-b-PEO/M1 with EO:M mole ratio of 1:1 presented an evident selectivity for moist CO2 permeance, which is identical with our initial proposal that the guest molecule M in the membranes will play the key role for CO2 facilitated transportation since the amidine groups of M could react reversibly with CO2 molecules in membranes. This work provides a supramolecular approach to fabricating CO2 facilitated transport membranes

Artificial NO and Light Cooperative Nanofluidic Diode Inspired by Stomatal Closure of Guard Cells

Gas messenger molecule (NO) plays important roles in K⁺ nanochannels of guard cells by binding directly to the heme-containing enzymes. Inspired by this natural phenomenon, we developed artificial K⁺ nanochannels modified with ferroporphyrin, where NO triggered the nanochannels to turn “ON” states from the ferroporphyrin blocked “OFF” states. The mechanism relies on the fact that NO has higher affinity with ferroporphyrin compared to carboxyl groups on the nanochannel surface. The synergistic effect of the released carboxyl groups and the conically asymmetric shape leads the ion transportation to be diode-like. However, the nanofluidic diode properties vanished after illumination with light to remove NO from the ferroporphyrin–NO complex. This NO and light cooperative nanofluidic diode possesses excellent stability and reversibility, which shows great promise for use in gas detection and remote control of mass delivery

Engineered Nanochannel Membranes with Diode-like Behavior for Energy Conversion over a Wide pH Range

Electric eels can generate high potential bioelectricity because of the numerous electrocytes, where the cell membranes contain ion-selective channels. Net electric current is formed by the directional permeation of ions across the channels. Many nanofluidic devices have been designed for energy conversion. However, the challenge still remains of the fabrication of scalable ion-selective membranes with high power density. Inspired by the electric eels, we designed an asymmetric nanochannel membrane with diode-like ion transport behaviors, resulting in high performance energy conversion over a wide pH range. The nanochannel membranes were obtained from the polymeric nanochannels with carboxyl groups and the anodic alumina oxide (AAO) nanochannels bearing hydroxyl groups. At different pH conditions, the synergistic effect of the hybrid nanochannels ensured directional ion regulation, leading to energy conversion with high power density. The scalable, versatile nanochannel membranes have promising potential applications in the salinity gradient energy harvest from various sources

Biodegradation and Mineralization of Polystyrene by Plastic-Eating Mealworms: Part 1. Chemical and Physical Characterization and Isotopic Tests

Polystyrene (PS) is generally considered to be durable and resistant to biodegradation. Mealworms (the larvae of Tenebrio molitor Linnaeus) from different sources chew and eat Styrofoam, a common PS product. The Styrofoam was efficiently degraded in the larval gut within a retention time of less than 24 h. Fed with Styrofoam as the sole diet, the larvae lived as well as those fed with a normal diet (bran) over a period of 1 month. The analysis of fecula egested from Styrofoam-feeding larvae, using gel permeation chromatography (GPC), solid-state ¹³C cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy, and thermogravimetric Fourier transform infrared (TG–FTIR) spectroscopy, substantiated that cleavage/depolymerization of long-chain PS molecules and the formation of depolymerized metabolites occurred in the larval gut. Within a 16 day test period, 47.7% of the ingested Styrofoam carbon was converted into CO₂ and the residue (ca. 49.2%) was egested as fecula with a limited fraction incorporated into biomass (ca. 0.5%). Tests with α ¹³C- or β ¹³C-labeled PS confirmed that the ¹³C-labeled PS was mineralized to ¹³CO₂ and incorporated into lipids. The discovery of the rapid biodegradation of PS in the larval gut reveals a new fate for plastic waste in the environment