Using synthetic genome readers/regulators to interrogate chromatin processes: A brief review

Aberrant gene expression underlies numerous human ailments. Hence, developing small molecules to target and remedy dysfunctional gene regulation has been a long-standing goal at the interface of chemistry and medicine. A major challenge for designing small molecule therapeutics aimed at targeting desired genomic loci is the minimization of widescale disruption of genomic functions. To address this challenge, we rationally design polyamide-based multi-functional molecules, i.e., Synthetic Genome Readers/Regulators (SynGRs), which, by design, target distinct sequences in the genome. Herein, we briefly review how SynGRs access chromatin-bound and chromatin-free genomic sites, then highlight the methods for the study of chromatin processes using SynGRs on positioned nucleosomes in vitro or disease-causing repressive genomic loci in vivo.

Engraving Polyamide Layers by In Situ Self-Etchable CaCO3 Nanoparticles Enhances Separation Properties and Antifouling Performance of Reverse Osmosis Membranes

Nanovoids within a polyamide layer play an important role in the separation performance of thin-film composite (TFC) reverse osmosis (RO) membranes. To form more extensive nanovoids for enhanced performance, one commonly used method is to incorporate sacrificial nanofillers in the polyamide layer during the exothermic interfacial polymerization (IP) reaction, followed by some post-etching processes. However, these post-treatments could harm the membrane integrity, thereby leading to reduced selectivity. In this study, we applied in situ self-etchable sacrificial nanofillers by taking advantage of the strong acid and heat generated in IP. CaCO3 nanoparticles (nCaCO3) were used as the model nanofillers, which can be in situ etched by reacting with H+ to leave void nanostructures behind. This reaction can further degas CO2 nanobubbles assisted by heat in IP to form more nanovoids in the polyamide layer. These nanovoids can facilitate water transport by enlarging the effective surface filtration area of the polyamide and reducing hydraulic resistance to significantly enhance water permeance. The correlations between the nanovoid properties and membrane performance were systematically analyzed. We further demonstrate that the nCaCO3-tailored membrane can improve membrane antifouling propensity and rejections to boron and As(III) compared with the control. This study investigated a novel strategy of applying self-etchable gas precursors to engrave the polyamide layer for enhanced membrane performance, which provides new insights into the design and synthesis of TFC membranes.

The role of sheet-like TiO2 in polyamide reverse osmosis membrane for enhanced removal of endocrine disrupting chemicals

Thin film composite (TFC) reverse osmosis (RO) membrane shows good promise for treating wastewater containing endocrine disrupting chemical (EDC) pollutants. The incorporation of functional materials with exceptional structural and physico-chemical properties offers opportunities for the membranes preparation with enhanced permselectivity and better antifouling properties. The present study aims to improve the EDC removal efficiency of TFC RO membrane using two-dimensional titania nanosheets (TNS). RO membrane was prepared by incorporating TNS in the dense layer of polyamide (PA) layer to form thin film nanocomposite (TFN) membrane. The TNS loading was varied and the influences on membrane morphology, surface hydrophilicity, surface charge, as well as water permeability and rejection of EDC were investigated. The results revealed that the inclusion of TNS in the membrane resulted in the increase of water permeability and EDC rejection. When treating the mixture of bisphenol A (BPA) and caffeine at 100 ppm feed concentration, the TFN membrane incorporated with 0.05% TNS achieved water permeability of 1.45 L/m2·h·bar, which was 38.6% higher than that of unmodified TFC membrane, while maintaining satisfactory rejection of >97%. The enhancement of water permeability for TFN membrane can be attributed to their hydrophilic surface and unique nanochannel structure created by the nanoscale interlayer spacing via staking of TiO2 nanosheets. Furthermore, the 0.05TFN membrane exhibited excellent fouling resistance towards BPA and caffeine pollutants with almost 100% flux recovery for three cycles of operations.

Polyamide Membranes with Tunable Surface Charge Induced by Dipole-Dipole Interaction for Selective Ion Separation

Nanofiltration (NF) has the potential to achieve precise ion-ion separation at the subnanometer scale, which is necessary for resource recovery and a circular water economy. Fabricating NF membranes for selective ion separation is highly desirable but represents a substantial technical challenge. Dipole-dipole interaction is a mechanism of intermolecular attractions between polar molecules with a dipole moment due to uneven charge distribution, but such an interaction has not been leveraged to tune membrane structure and selectivity. Herein, we propose a novel strategy to achieve tunable surface charge of polyamide membrane by introducing polar solvent with a large dipole moment during interfacial polymerization, in which the dipole-dipole interaction with acyl chloride groups of trimesoyl chloride (TMC) can successfully intervene in the amidation reaction to alter the density of surface carboxyl groups in the polyamide selective layer. As a result, the prepared positively charged (PEI-TMC)-NH2 and negatively charged (PEI-TMC)-COOH composite membranes, which show similarly high water permeance, demonstrate highly selective separations of cations and anions in engineering applications, respectively. Our findings, for the first time, confirm that solvent-induced dipole-dipole interactions are able to alter the charge type and density of polyamide membranes and achieve tunable surface charge for selective and efficient ion separation.

From Forest to Future: Synthesis of Sustainable High Molecular Weight Polyamides Using and Investigating the AROP of β-Pinene Lactam

Polyamides (PA) are among the most essential and versatile polymers due to their outstanding characteristics, for example, high chemical resistance and temperature stability. Furthermore, nature-derived monomers can introduce hard-to-synthesize structures into the PAs for unique polymer properties. Pinene, as one of the most abundant terpenes in nature and its presumable stability-giving bicyclic structure, is therefore highly promising. This work presents simple anionic ring-opening polymerizations of β-pinene lactam (AROP) in-bulk and in solution. PAs with high molecular weights, suitable for further processing, are produced. Their good mechanical, thermal (Td s up to 440 °C), and transparent appearance render them promising high-performance biomaterials. In the following, the suitability of different initiators is discussed. Thereby, it is found that NaH is the most successful for in-bulk polymerization, with a degree of polymerization (DP) of about 322. For solution-AROP, iPrMgCl·LiCl is successfully used for the first time, achieving DPs up to about 163. The obtained PAs are also hot-pressed, and the dynamic mechanical properties are analyzed.

Reducing Chloride Ion Permeation during Seawater Electrolysis Using Double-Polyamide Thin-Film Composite Membranes

Low-cost polyamide thin-film composite membranes are being explored as alternatives to expensive cation exchange membranes for seawater electrolysis. However, transport of chloride from seawater to the anode chamber must be reduced to minimize the production of chlorine gas. A double-polyamide composite structure was created that reduced the level of chloride transport. Adding five polyamide layers on the back of a conventional polyamide composite membrane reduced the chloride ion transport by 53% and did not increase the applied voltage. Decreased chloride permeation was attributed to enhanced electrostatic and steric repulsion created by the new polyamide layers. Charge was balanced through increased sodium ion transport (52%) from the anolyte to the catholyte rather than through a change in the transport of protons and hydroxides. As a result, the Nernstian loss arising from the pH difference between the anolyte and catholyte remained relatively constant during electrolysis despite membrane modifications. This lack of a change in pH showed that transport of protons and hydroxides during electrolysis was independent of salt ion transport. Therefore, only sodium ion transport could compensate for the reduction of chloride flux to maintain the set current. Overall, these results prove the feasibility of using a double-polyamide structure to control chloride permeation during seawater electrolysis without sacrificing energy consumption.

Development of multifunctional pyrrole-imidazole polyamides that increase hepatocyte growth factor and suppress transforming growth factor-β1

PURPOSE

The DNA recognition peptide compounds pyrrole-imidazole (PI) polyamides bind to the minor groove and can block the binding of transcription factors to target sequences. To develop more PI polyamides as potential treatments for fibrotic diseases, including chronic renal failure, we developed multifunctional PI polyamides that increase hepatocyte growth factor (HGF) and decrease transforming growth factor (TGF)-β1.

METHODS

We designed seven PI polyamides (HGF-1 to HGF-7) that bind to the chicken ovalbumin upstream promoter transcription factor-1 (COUP-TF1) binding site of the HGF promoter sequence. We selected PI polyamides that increase HGF and suppress TGF-β1 in human dermal fibroblasts (HDFs).

FINDINGS

Gel shift assays showed that HGF-2 and HGF-4 bound the appropriate dsDNAs. HGF-2 and HGF-4 significantly inhibited the TGF-β1 mRNA expression in HDFs stimulated by phorbol 12-myristate 13-acetate. HGF-2 and HGF-4 significantly inhibited the TGF-β1 protein expression in HDFs with siRNA targeting HGF, indicating that HGF-2 and HGF-4 directly inhibited the expression of TGF-β1.

CONCLUSION

The designed and synthetic HGF PI polyamides targeting the HGF promoter, which increased the expression of HGF and suppressed the expression of TGF-β, will be a potential practical medicine for fibrotic diseases, including progressive renal diseases.

Mechanism Study of the Polymerization of Polyamide 56: Reaction Kinetics and Process Parameters

Polyamide 56 (PA56) has gained significant attention in the academic field due to its remarkable mechanical and thermal properties as a highly efficient and versatile biobased material. Its superior moisture absorption property also makes it a unique advantage in the realm of fiber textiles. However, despite extensive investigations on PA56's molecular and aggregate state structure, as well as processing modifications, little attention has been paid to its polymerization mechanism. Herein, the influence of temperature and time on PA56's polycondensation reaction is detailed studied by end-group titration and carbon nuclear magnetic resonance (NMR) techniques. The reaction kinetics equations for the pre-polymerization and vacuum melt-polymerization stages of PA56 are established, and possible side reactions during the polycondensation process are analyzed. By optimizing the reaction process based on kinetic characteristics, PA56 resin with superior comprehensive properties (melting temperature of 252.6 °C, degradation temperature of 371.6 °C, and tensile strength of 75 MPa) is obtained. The findings provide theoretical support for the industrial production of high-quality biobased PA56.

Ti2NTx quasi-MXene modified polyamide thin film composite reverse osmosis membrane with effective desalination and antifouling performance

In this study, considering the serious problem of lack of fresh water worldwide and the effectiveness of reverse osmosis (RO) membranes in water purification, we prepared improved RO membranes with two-dimensional quasi-MXene nanosheets. In this study, the MAX phase with the chemical formula of Ti2AlN was prepared through the reactive sintering route. Prosperous preparation of the MAX phase with the hexagonal crystalline structure was approved by an X-ray diffraction pattern. Compacted sheets morphology was recognized for the prepared MAX phase from transmittance electron microscopy and scanning electron microscopy micrographs. Then, Ti2NTx quasi-MXene nanosheets were prepared by selective ultrasonic-assisted exfoliation of the MAX phase. Polyamide (PA) thin-layer composite RO membranes with different weight percentages of Ti2NTx quasi-MXene were fabricated by the interfacial polymerization (IP) method. The addition of ultrasonic-assisted prepared quasi-MXene creates numerous and coherent nanochannels on the surface of the membrane. The optimum membrane with 0.01 wt% of quasi-MXene showed the highest pure water flux of 31.9 L m-2. h-1 with an improved salt rejection of 98.2%. Therefore, these nanosheets showed that they can partially solve the trade-off between water permeability and salt rejection, which is a serious challenge in RO membranes. Also, the membranes containing quasi-MXene showed good resistance against fouling by humic acid. This research can be a scalable development in making high-performance membranes.

A review on artificial water channels incorporated polyamide membranes for water purification: Transport mechanisms and performance

While thin-film composite (TFC) polyamide (PA) membranes are advanced for removing salts and trace organic contaminants (TrOCs) from water, TFC PA membranes encounter a water permeance-selectivity trade-off due to PA layer structural characteristics. Drawing inspiration from the excellent water permeance and solute rejection of natural biological channels, the development of analogous artificial water channels (AWCs) in TFC PA membranes (abbreviated as AWCM) promises to achieve superior mass transfer efficiency, enabling breaking the upper bound of water permeance and selectivity. Herein, we first discussed the types and structural characteristics of AWCs, followed by summarizing the methods for constructing AWCM. We discussed whether the AWCs acted as the primary mass transfer channels in AWCM and emphasized the important role of the AWCs in water transport and ion/TrOCs rejection. We thoroughly summarized the molecular-level mechanisms and structure-performance relationship of water molecules, ions, and TrOCs transport in the confined nanospace of AWCs, which laid the foundation for illustrating the enhanced water permeance and salt/TrOCs selectivity of AWCM. Finally, we discussed the challenges encountered in the field of AWCM and proposed future perspectives for practical applications. This review is expected to offer guidance for understanding the transport mechanisms of AWCM and developing next-generation membrane for effective water treatment.

High performance forward osmosis membrane with ultrathin hydrophobic nanofibrous interlayer

The novel thin film composite (TFC) forward osmosis (FO) membrane with electrospinning nanofibers as support layer can alleviate internal concentration polarization (ICP). While the macropores of the nanofiber support layer cause defects in the polyamide (PA) layer. Therefore, hydrophobic polyvinylidene fluoride (PVDF) fine nanofibers were used as an interlayer to modulate the process of interfacial polymerization (IP) in this study. The results showed that the introduction of the interlayer improved the hydrophobicity of the support layer for achieving uniform, thin and defect-free selective polyamide (PA) layer. The water flux of TFC-PVDF was 58.26 LMH in the FO mode of 2 M NaCl, which was two times higher than that of the unmodified FO membrane. Lower reverse salt flux (4.91 gMH) and structural parameter (179.43 μm) alleviated the ICP. In addition, TFC-PVDF membrane showed good anti-fouling performance for SA (flux recovery ratio of 93.97%) due to high hydrophilicity, low zeta potential and low roughness. This study provides an easy and promising method to prepare defect-free PA selective layer on the macropores nanofiber support layer. The novel FO membrane shows high desalination performance and anti-fouling properties.

Tailoring properties and performance of thin-film composite membranes by salt additives for water treatment: A critical review

During the fabrication of thin film composite (TFC) membranes by interfacial polymerization (IP), the utilization of salt additives is one of the effective methods to regulate membrane properties and performance. Despite gradually receiving widespread attention for membrane preparation, the strategies, effects and underlying mechanisms of using salt additives have not yet been systematically summarized. This review for the first time provides an overview of various salt additives used to tailor properties and performance of TFC membranes for water treatment. By classifying salt additives into organic and inorganic salts, the roles of added salt additives in the IP process and the induced changes in membrane structure and properties are discussed in detail, and the different mechanisms of salt additives affecting membrane formation are summarized. Based on these mechanisms, the salt-based regulation strategies have shown great potential for improving the performance and application competitiveness of TFC membranes, including overcoming the trade-off relationship between water permeability and salt selectivity, tailoring membrane pore size distribution for precise solute-solute separation, and enhancing membrane antifouling performance. Finally, future research directions are suggested to focus on the long-term stability assessment of salt-modified membranes, the combined use of different salt additives, and the integration of salt regulation with other membrane design or modification strategies.

Internal Concentration Polarization in the Polyamide Active Layer of Thin-Film Composite Membranes

A free-standing polyamide (PA) film is fabricated via in situ release from a thin-film composite (TFC) membrane achieved through the removal of the polysulfone support. The structure parameter S of the PA film is measured to be 24.2 ± 12.6 μm, which is about 87-fold of its film thickness. A significant decline in water flux of the PA film from an ideal forward osmosis membrane is observed. We find that the decline is predominantly influenced by the internal concentration polarization (ICP) of the PA film based on our experimental measurements and theoretical calculations. We propose that the asymmetric hollow structures of the PA layer with dense crusts and cavities may be the underlying cause of the occurrence of the ICP. More importantly, the structure parameter of the PA film can be reduced and its ICP effect can be mitigated by tuning its structures with fewer and shorter cavities. Our results for the first time provide experimental evidence to prove that the PA layer of the TFC membrane has the ICP effect, which could potentially provide fundamental insights into the influence of structural properties of PA on the membrane separation performance.

Significance of Co-ion Partitioning in Salt Transport through Polyamide Reverse Osmosis Membranes

Salt permeability of polyamide reverse osmosis (RO) membranes has been shown to increase with increasing feed salt concentration. The dependence of salt permeability on salt concentration has been attributed to the variation of salt partitioning with feed salt concentration. However, studies using various analytical techniques revealed that the salt (total ion) partitioning coefficient decreases with increasing salt concentration, in marked contrast to the observed increase in salt permeability. Herein, we thoroughly investigate the dependence of total ion and co-ion partitioning coefficients on salt concentration and solution pH. The salt partitioning is measured using a quartz crystal microbalance (QCM), while the co-ion partitioning is calculated from the measured salt partitioning using a modified Donnan theory. Our results demonstrate that the co-ion and total ion partitioning behave entirely differently with increasing salt concentrations. Specifically, the co-ion partitioning increased fourfold, while total ion partitioning decreased by 60% as the salt (NaCl) concentration increased from 100 to 800 mM. The increase in co-ion partitioning with increasing salt concentration is in accordance with the increasing trend of salt permeability in RO experiments. We further show that the dependence of salt and co-ion partitioning on salt concentration is much more pronounced at a higher solution pH. The good co-ion exclusion (GCE) model─derived from the solution-friction model─is used to calculate the salt permeability based on the co-ion partitioning coefficients. Our results show that the GCE model predicts the salt permeabilities in RO experiments relatively well, indicating that co-ion partitioning, not salt partitioning, governs salt transport through RO membranes. Our study provides an in-depth understanding of ion partitioning in polyamide RO membranes and its relationship with salt transport.

Dual-layer Janus charged nanofiltration membranes constructed by sequential electrospray polymerization for efficient water softening

The separation of hardness ions such as calcium and magnesium from hard water can improve water quality, which is important but technically challenging. Nanofiltration (NF) has attracted much attention because of its efficiency, environmental friendliness and low cost. However, common NF membranes with a singly (either positively or negatively) charged layer have insufficient water softening capacity. In this work, two types of dual-layer Janus charged polyamide NF membranes composed of oppositely charged inner and outer layers were developed for the first time by sequential electrospray polymerization strategy for efficient water softening. The effect of the microstructure of the dually charged barrier layer on the separation performance of divalent salt ions was explored. Detailed mechanistic studies revealed that the microstructure of the outer layer of the barrier layer played a crucial role in the ion separation of the Janus membrane due to its control of the reverse transport of ions. Janus charged polyamide NF membrane with a loose outer layer exhibited better water softening performance (93.6% of hardness removed) compared to the singly charged NF membranes due to the simultaneous dual electrostatic effect and no ion reverse transport confinement. This Janus charged NF membrane also possessed good antifouling performance, mainly due to its negatively charged outer layers. The mechanistic insights gained in this study reveal the huge potential of microstructural design toward high-performance Janus charged NF membranes, and provide important guidance on the future development of high-efficiency water softening NF membranes.

N-Oxide Zwitterion Functionalized Positively Charged Polyamide Composite Membranes for Nanofiltration

N-Oxide zwitterionic polyethyleneimine (ZPEI), a new kind of aqueous phase monomer synthesized by commercially branched polyethyleneimine (PEI) via oxidation reaction, was prepared for fabrication of thin-film composite (TFC) polyamide membranes via interfacial polymerization. The main factors, including the monomer concentration and immersion time of the aqueous phase and organic phase, were investigated. Compared with PEI-TFC membranes, the obtained optimal defect-free ZPEI-TFC membranes exhibited a lower roughness (3.3 ± 0.3 nm), a better surface hydrophilicity, and a smaller pore size (238 Da of MWCO). The positively charged ZPEI-TFC membranes (isoelectric point at pH 8.05) showed higher rejections toward both divalent cationic (MgCl₂, 93.0%) and anionic (Na₂SO₄, 96.1%) salts with a water permeation flux of up to 81.0 L·m^-2·h^-1 at 6 bar, which surpassed currently reported membranes. More importantly, mainly owing to N-oxide zwitterion with strong hydration capability, ZPEI-TFC membranes displayed a high flux recovery ratio (97.0%) toward a model protein contaminant (bovine serum albumin), indicating good anti-fouling properties. Therefore, the novel N-oxide zwitterion functionalized positively charged nanofiltration membranes provide an alternative for water desalination and sewage reclamation.

Planting Anion Channels in a Negatively Charged Polyamide Layer for Highly Selective Nanofiltration Separation

A nanofiltration (NF) membrane with high salt permeation and high retention of small organics is appealing for the treatment of high-salinity organic wastewater. However, the conventional negatively charged NF membranes commonly show high retention of divalent anions (e.g., SO₄^2-), and the reported positively charged NF membranes normally suffer super low selectivity for small organics/Na₂SO₄ and high fouling potential. In this work, we propose a novel "etching-swelling-planting" strategy assisted by interfacial polymerization and mussel-inspired catecholamine chemistry to prepare a mix-charged NF membrane. By X-ray photoelectron spectroscopy depth profiling and pore size distribution analysis, it was found that such a strategy could not only deepen the positive charge distribution but also narrow the pore size. Molecular dynamics confirm that the planted polyethyleneimine chains play an important role to relay SO₄^2- ions to facilitate their transport across the membrane, thus reversing the retention of Na₂SO₄ and glucose (43 vs 71%). Meanwhile, due to the high surface hydrophilicity and smoothness as well as the preservation of abundant negatively charged groups (-OH and -COOH) inside the separation layer, the obtained membrane exhibited excellent antifouling performance, even for the coking wastewater. This study advances the importance of vertical charge distribution of NF membranes in separation selectivity and antifouling performance.

Zwitterionic metal-organic frameworks modified polyamide membranes with enhanced water flux and antifouling capacity

Antifouling properties are considered to be crucial parameter to polyamide (PA) composite nanofiltration (NF) membranes for practical applications. In this study, an antifouling material, surface zwitterionization of Metal-organic frameworks (Z-MIL-101 (Cr)) was firstly prepared by decorating zwitterionic polymer onto the MOFs surface. Subsequently, a novel type of MOFs-based hybrid membranes were fabricated via mixing the Z-MIL-101 (Cr) nanoparticle with the organic matrix by interfacial polymerization technique. The most optimal hybrid membrane had a high water permeation of 26 L m^-2 h^-1 bar^-1, which was 2.1 times higher than that pristine PA membrane, while the retention for Na₂SO₄ was still kept at a considerably high value of 93%. The significant increased water flue can attribute to the existence of water channels generated by the Z-MIL-101 (Cr). More important, the antifouling property of the hybrid membrane was much better than that pristine PA, which was due to the formation of superhydrophilic liquid layer surrounding the zwitterionic groups. The combination of the micropore structure of the MOFs and the excellent antifouling properties of the decorated zwitterionic polymer effectively improved separation performances and antifouling ability, which makes these hybrid membranes promising for water purification.

Modulating the Asymmetry of the Active Layer in Pursuit of Nanofiltration Selectivity via Differentiating Interfacial Reactions of Piperazine

Nanofiltration (NF), highly prospective for drinking water treatment, faces a challenge in simultaneously removing emerging contaminants while maintaining mineral salts, particularly divalent cations. To overcome this challenge, NF membranes possessing small pores concomitant with highly negatively charged surfaces were synthesized via a two-step fabrication strategy. The key is to generate a polyamide active layer having a loose and carboxyl group-abundant segment on top and a dense barrier segment underneath. This was achieved by restrained interfacial polymerization between trimesoyl chloride and partly protonated piperazine to form a highly depth-heterogeneous polyamide network, followed by second amidation in an organic environment to remove untethered polyamide fragments and associate malonyl chlorides with reserved amine groups to introduce more negative charges. Most importantly, on first-principle engineering the spatial architecture of the polyamide layer, amplifying asymmetric charge distribution was paired with the thinning of the vertical structure. The optimized membrane exhibits high salt/organic rejection selectivity and water permeance superior to most NF membranes reported previously. The rejections of eight emerging contaminants were in the range of 66.0-94.4%, much higher than the MgCl₂ rejection of 41.1%. This new fabrication strategy, suitable for various diacyl chlorides, along with the new membranes so produced, offers a novel option for NF in potable water systems.

Beyond nylon 6: polyamides via ring opening polymerization of designer lactam monomers for biomedical applications

Ring opening polymerization (ROP) of lactams is a highly efficient and versatile method to synthesize polyamides. Within the last ten years, significant advances in polymerization methodology and monomer diversity are ushering in a new era of polyamide chemistry. We begin with a discussion of polymerization techniques including the most widely used anionic ring opening polymerization (AROP), and less prevalent cationic ROP and enzyme-catalyzed ROP. Next, we describe new monomers being explored for ROP with increased functionality and stereochemistry. We emphasize the relationships between composition, structure, and properties, and how chemists can control composition and structure to dictate a desired property or performance. Finally, we discuss biomedical applications of the synthesized polyamides, specifically as biomaterials and pharmaceuticals, with examples to include as antimicrobial agents, cell adhesion substrates, and drug delivery scaffolds.

Nanofiltration Membranes with Crumpled Polyamide Films: A Critical Review on Mechanisms, Performances, and Environmental Applications

Nanofiltration (NF) membranes have been widely applied in many important environmental applications, including water softening, surface/groundwater purification, wastewater treatment, and water reuse. In recent years, a new class of piperazine (PIP)-based NF membranes featuring a crumpled polyamide layer has received considerable attention because of their great potential for achieving dramatic improvements in membrane separation performance. Since the report of novel crumpled Turing structures that exhibited an order of magnitude enhancement in water permeance ( Science 2018, 360 (6388), 518-521), the number of published research papers on this emerging topic has grown exponentially to approximately 200. In this critical review, we provide a systematic framework to classify the crumpled NF morphologies. The fundamental mechanisms and fabrication methods involved in the formation of these crumpled morphologies are summarized. We then discuss the transport of water and solutes in crumpled NF membranes and how these transport phenomena could simultaneously improve membrane water permeance, selectivity, and antifouling performance. The environmental applications of these emerging NF membranes are highlighted, and future research opportunities/needs are identified. The fundamental insights in this review provide critical guidance on the further development of high-performance NF membranes tailored for a wide range of environmental applications.

Incorporating Ag@RF core-shell nanomaterials into the thin film nanocomposite membrane to improve permeability and long-term antibacterial properties for nanofiltration

Ag@resorcinol-formaldehyde resin (Ag@RF) core-shell nanomaterials were prepared by Stöber method, and introduced into polyamide (PA) selective layer of thin-film nanocomposite (TFN) membranes through the interfacial polymerization (IP) process. Due to the abundant hydroxyl groups on the surface and suitable particle size, Ag@RF nanoparticles (Ag@RFs) could be uniformly dispersed in the piperazine aqueous solution and participate in the IP process to precisely regulate the microstructure of the PA selective layer. The resulting "crater structure" and irregular granular structure enlarged the permeable area and contributed to the surface hydrophilicity. For the nanofiltration application, the water flux of TFN membrane modified by Ag@RFs to Na₂SO₄ solution reached 150 L·m^-2·h^-1 which was 87.5% greater than TFC, and salt rejection was maintained. The antibacterial efficiency of the prepared TFN membrane on E. coli reached 99.6% in the antibacterial experiment. In addition, due to the special structure of Ag@RFs, the TFN membrane also showed an expected slow-release capability of Ag⁺, allowing for long-term anti-biofouling properties. This work demonstrates that Ag@RF core-shell nanoparticles with high compatibility of organic nanoparticles and antibacterial properties of Ag nanoparticles could be used as promising nanofillers for designing functional nanofiltration TFN membranes.

Chlorambucil-conjugated PI-polyamides (Chb-M'), a transcription inhibitor of RUNX family, has an anti-tumor activity against SHH-type medulloblastoma with p53 mutation

Malignancy of medulloblastoma depends on its molecular classification. Sonic Hedgehog (SHH)-type medulloblastoma with p53 mutation was recognized as one of the most aggressive types of tumors. We developed a novel drug, chlorambucil-conjugated PI-polyamides (Chb-M'), which was designed to compete with the RUNX consensus DNA-binding site. Chb-M' specifically recognizes this consensus sequence and alkylates it to inhibit the RUNX transcriptional activity. In-silico analysis showed all the RUNX families were upregulated in the SHH-type medulloblastoma. Thus, we tested the anti-tumor effects of Chb-M' in vitro and in vivo using Daoy cell lines, which belong to SHH with p53 mutation. Chb-M' inhibited tumor growth of Daoy cells by inducing apoptosis. The same inhibitory effect was also observed by knocking down of RUNX1 or RUNX2, but not RUNX3. Apoptosis array analysis showed that Chb-M' treatment induced phosphorylation of p53 serine 15 residues. In a subcutaneous tumor model, intratumoral injection of Chb-M' induced tumor growth retardation. Chb-M' mediated inhibition of RUNX1 and RUNX2 can be a novel therapeutic strategy for SHH-type medulloblastoma with p53 mutation.

Loosely Sandwich-Structured Membranes Decorated with UiO-66-NH2 for Efficient Antibiotic Separation and Organic Solvent Resistance

Thin-film nanocomposite (TFN) membranes with efficient molecular separation and organic solvent resistance are active in demand in wastewater treatment and resource reclamation, meeting the goal of emission peaks and carbon neutrality. In this work, a simple and rational design strategy has been employed to construct a sandwich-structured membrane for removing fluoroquinolone antibiotics and recycling organic solvents. The sandwich-structured membrane is composed of a porous substrate, a hydrophilic tannic acid-polyethyleneimine (TA-PEI) interlayer, and a polyamide (PA) selective layer decorated with metal-organic framework (PA-MOF). Results manifest that the hydrophilic TA-PEI interlayer played a bridging and gutter effect to achieve effective control in amide storage, amine diffusion, and nanomaterial downward leakage at the immiscible interface. The PA-MOF selective layer has been changed to a loosely crumpled surface, endowing functionalities on the sandwich-structured membrane that included limited pores, strengthened electronegativity, and stronger hydrophilicity. Thus, an enhanced water flux of 87.23 ± 7.43 LMH was achieved by the TFN-2 membrane (0.04 mg·mL^-1 UiO-66-NH₂), which is more than five times that of the thin-film composite membrane (17.46 ± 3.88 LMH). The rejection against norfloxacin, ciprofloxacin, and levofloxacin is 92.94 ± 1.60%, 94.62 ± 1.29%, and 96.92 ± 1.05%, respectively, effectively breaking through the "trade-off" effect between membrane permeability and rejection efficiency. Further antifouling results showed that the sandwich-structured membrane had lower flux decay ratios (3.36∼7.07%) and higher flux recovery ratios (93.40∼98.40%), as well as superior long-term stability after 30 days of filtration. Moreover, organic solvent resistance testing confirms that the sandwich-structured membrane maintained stable solvent flux and better recovery rates in ethanol, acetone, isopropanol, and N,N-dimethylformamide. Detailed nanofiltration mechanism studies revealed that these outstanding performances are based on the joint effect of the TA-PEI interlayer and PA-MOF selective layer, proposing a new perspective to break through the bottleneck of nanofiltration application in a complex environment.

Modification Mechanism of Polyamide Reverse Osmosis Membrane by Persulfate: Roles of Hydroxyl and Sulfate Radicals

Oxidative modification is a facile method to improve the desalination performance of thin-film composite membranes. In this study, we comparatively investigated the modification mechanisms induced by sulfate radical (SO₄^• -) and hydroxyl radical (HO^•) for polyamide reverse osmosis (RO) membrane. The SO₄^• -- and HO^•-based membrane modifications were manipulated by simply adjusting the pH of the thermal-activated persulfate solution. Although both of them improved the water permeability of the RO membrane under certain conditions, the SO₄^• --modified membrane notably prevailed over the HO^•-modified one due to higher permeability, more consistent salt rejection rates over wide pH and salinity ranges, and better stability when exposed to high doses of chlorine. The differences of the membranes modified by the two radical species probably can be related to their distinct surface properties in terms of morphology, hydrophilicity, surface charge, and chemical composition. Further identification of the transformation products of a model polyamide monomer using high-resolution mass spectrometry demonstrated that SO₄^• - initiated polymerization reactions and produced hydroquinone/benzoquinone and polyaromatic structures; whereas the amide group of the monomer was degraded by HO^•, generating hydroxyl, carboxyl, and nitro groups. The results will enlighten effective ways for practical modification of polyamide RO membranes to improve desalination performances and the development of sustainable oxidation-combined membrane processes.

A novel ceramic-based thin-film composite nanofiltration membrane with enhanced performance and regeneration potential

The rational design of a ceramic-based nanofiltration membrane remains a significant challenge due to its performance and fabrication cost. Herein, we report a high-performance ceramic-based thin-film composite (TFC) membrane fabricated via a typical interfacial polymerization on an interwoven net substrate assembled by titanium dioxide (TiO₂) nanowires. The chemical properties and morphologies were systematically investigated for ceramic substrates and their corresponding TFC membranes. Due to the significantly improved hydrophilicity of the TiO₂ framework, more reactive amine monomers were uniformly adsorbed on the modified surface of the ceramic substrate, yielding an ultrathin polyamide layer with less resistance. In addition, the smooth surface and decreased pore size of the TiO₂ framework contributed to forming a defect-free polyamide layer. As a result, the obtained ceramic-based TFC membrane evinced high permeance of 26.4 L m^-2 h^-1 bar^-1 and excellent salt rejection efficiency, leading to simultaneous improvements compared with the control TFC membrane without the TiO₂ framework. Notably, the potential regeneration ability of the ceramic-based TFC membrane could be achieved via facile low-temperature calcination and re-polymerization process due to the varied thermostability between the polyamide layer and the robust ceramic substrate. The operation of regeneration helped to prolong the lifetime and decrease the cost for the ceramic-based TFC membrane. This research provides a feasible protocol to fabricate sustainable ceramic-based nanofiltration membranes with enhanced performance for water treatment.

Proteoliposome-Incorporated Seawater Reverse Osmosis Polyamide Membrane: Is the Aquaporin Water Channel Effect in Improving Membrane Performance Overestimated?

The water channel feature of the aquaporin (AQP) is considered to be the key in improving the permselectivity of AQP-based thin-film composite (TFC) polyamide (PA) membranes, yet much less attention has been paid to the physicochemical property changes of the PA layer induced by AQP-reconstituted proteoliposomes. This study systematically investigated the roles of proteoliposome constituents (liposome/detergent/AQP) in affecting the physicochemical properties and performance of the membranes. For the first time, we demonstrated that the constituents in the proteoliposome could facilitate the formation of a PA layer with enlarged protuberances and thinner crumples, resulting in a 79% increase in effective surface area and lowering of hydraulic resistance for filtration. These PA structural changes of the AQP-based membrane were found to contribute over 70% to the water permeability increase via comparing the separation performance of the membranes prepared with liposome, detergent, and proteoliposome, respectively, and one proteoliposome-ruptured membrane. The contribution from the AQP water channel feature was about 27% of water permeability increase in the current study, attributed to only ∼20% vesicle coverage in the PA matrix, and this contribution may be easily lost as a result of vesicle rupture during the real seawater reverse osmosis process. This study reveals that the changed morphology dominates the performance improvement of the AQP-based PA membrane and well explains why the actual AQP-based PA membranes cannot acquire the theoretical water/salt selectivity of a biomimetic AQP membrane, deepening our understanding of the AQP-based membranes.

Eco-friendly surface modification approach to develop thin film nanocomposite membrane with improved desalination and antifouling properties

Introduction

Nanomaterials aggregation within polyamide (PA) layer of thin film nanocomposite (TFN) membrane is found to be a common issue and can negatively affect membrane filtration performance. Thus, post-treatment on the surface of TFN membrane is one of the strategies to address the problem.

Objective

In this study, an eco-friendly surface modification technique based on plasma enhanced chemical vapour deposition (PECVD) was used to deposit hydrophilic acrylic acid (AA) onto the PA surface of TFN membrane with the aims of simultaneously minimizing the PA surface defects caused by nanomaterials incorporation and improving the membrane surface hydrophilicity for reverse osmosis (RO) application.

Methods

The TFN membrane was first synthesized by incorporating 0.05 wt% of functionalized titania nanotubes (TNTs) into its PA layer. It was then subjected to 15-s plasma deposition of AA monomer to establish extremely thin hydrophilic layer atop PA nanocomposite layer. PECVD is a promising surface modification method as it offers rapid and solvent-free functionalization for the membranes.

Results

The findings clearly showed that the sodium chloride rejection of the plasma-modified TFN membrane was improved with salt passage reduced from 2.43% to 1.50% without significantly altering pure water flux. The AA-modified TFN membrane also exhibited a remarkable antifouling property with higher flux recovery rate (>95%, 5-h filtration using 1000 mg/L sodium alginate solution) compared to the unmodified TFN membrane (85.8%), which is mainly attributed to its enhanced hydrophilicity and smoother surface. Furthermore, the AA-modified TFN membrane also showed higher performance stability throughout 12-h filtration period.

Conclusion

The deposition of hydrophilic material on the TFN membrane surface via eco-friendly method is potential to develop a defect-free TFN membrane with enhanced fouling resistance for improved desalination process.

Durable nanocomposite face masks with high particulate filtration and rapid inactivation of coronaviruses

The COVID-19 pandemic presents a unique challenge to the healthcare community due to the high infectivity rate and need for effective personal protective equipment. Zinc oxide nanoparticles have shown promising antimicrobial properties and are recognized as a safe additive in many food and cosmetic products. This work presents a novel nanocomposite synthesis approach, which allows zinc oxide nanoparticles to be grown within textile and face mask materials, including melt-blown polypropylene and nylon-cotton. The resulting nanocomposite achieves greater than 3 log10 reduction (≥ 99.9%) in coronavirus titer within a contact time of 10 min, by disintegrating the viral envelope. The new nanocomposite textile retains activity even after 100 laundry cycles and has been dermatologist tested as non-irritant and hypoallergenic. Various face mask designs were tested to improve filtration efficiency and breathability while offering antiviral protection, with Claros' design reporting higher filtration efficiency than surgical masks (> 50%) for particles ranged 200 nm to 5 µm in size.

Atom transfer radical-polymerized cationic shells on gold nanoparticles for near infrared-triggered photodynamic therapy of tumor-bearing animals

Gold nanoparticles (AuNPs) were surface-engineered with a cationic corona to enhance the incorporation of photosensitizers for photodynamic therapy (PDT). The cationic corona composed of poly(2-(dimethylamino)ethyl methacrylate) was atom transfer radical-polymerized on the surface of the AuNPs. The cationic corona of the engineered surface was characterized by dynamic light scattering, electron microscopy, Raman spectroscopy, and mass spectroscopy. Chlorin-e6 (Ce6) incorporated onto the surface-engineered AuNPs exhibited higher cell incorporation efficiency than bare AuNPs. Ce6-incorporated AuNPs were confirmed to release singlet oxygen upon NIR irradiation. Compared to Ce6, Ce6-incorporated AuNPs exhibited higher cellular uptake and cytotoxicity against cancer cells in an irradiation time-dependent manner. Near-infrared-irradiated animals administered Ce6-incorporated AuNPs exhibited higher levels of tumor suppression without noticeable body weight loss. This result was attributed to the higher localization of Ce6 at the tumor sites to induce cancer cell apoptosis. Thus, we envision that engineered AuNPs with cationic corona can be tailored to effectively deliver photosensitizers to tumor sites for photodynamic therapy.

Preparation and Characterization of Semi-IPN Cryogels Based on Polyacrylamide and Poly(N,N-dimethylaminoethyl methacrylate); Functionalization of Carrier with Monochlorotriazinyl-β-cyclodextrin and Release Kinetics of Curcumin

Curcumin (CCM) is a natural hydrophobic polyphenol known for its numerous applications in the food industry as a colorant or jelly stabilizer, and in the pharmaceutical industry due to its anti-inflammatory, antibacterial, antioxidant, anti-cancer, and anti-Alzheimer properties. However, the large application of CCM is limited by its poor solubility in water and low stability. To enhance the bioavailability of CCM, and to protect it against the external degradation agents, a novel strategy, which consists in the preparation of semi-interpenetrating polymer networks, (s-IPNs) based on poly(N,N-dimethylaminoethyl methacrylate) entrapped in poly(acrylamide) networks, by a cryogelation technique, was developed in this work. All s-IPN cryogels were characterized by SEM, EDX, FTIR, and swelling at equilibrium as a function of pH. Functionalization of semi-IPN cryogel with monochlorotriazinyl-β-cyclodextrin (MCT-β-CD) led to IPN cryogel. The release profile of CCM from the composite cryogels was investigated at 37 °C, in pH 3. It was found that the cumulative release increased with the increase of the carrier hydrophobicity, as a result of increasing the cross-linking degree, the content and the molar mass of PDMAEMA. Fitting Higuchi, Korsmeyer–Peppas, and first order kinetic models on the CCM release profiles indicated the diffusion as the main driving force of drug release from the composite cryogels.

Magnetic Nanoplatforms for Covalent Protein Immobilization Based on Spy Chemistry

Immobilization of proteins on magnetic nanoparticles (MNPs) is an effective approach to improve protein stability and facilitate separation of immobilized proteins for repeated use. Herein, we exploited the efficient SpyTag-SpyCatcher chemistry for conjugation of functional proteins onto MNPs and established a robust magnetic-responsive nanoparticle platform for protein immobilization. To maximize the loading capacity and achieve outstanding water dispersity, the SpyTag peptide was incorporated into the surface-charged polymers of MNPs, which provided abundant active sites for Spy chemistry while maintaining excellent colloidal stability in buffer solution. Conjugation between enhanced green fluorescence protein (EGFP)-SpyCatcher-fused proteins and SpyTag-functionalized MNPs was efficient at ambient conditions without adding enzymes or chemical cross-linkers. Benefiting from the excellent water dispersity and interface compatibility, the surface Spy reaction has fast kinetics, which is comparable to that of the solution Spy reaction. No activity loss was observed on EGFP after conjugation due to the site-selective nature of Spy chemistry. The immobilization process of EGFP on MNPs was highly specific and robust, which was not affected by the presence of other proteins and detergents, such as bovine serum albumin and Tween 20. The MNP platform was demonstrated to be protective to the conjugated EGFP and significantly improved the shelf life of immobilized proteins. In addition, experiments confirmed the retained magnetophoresis of the MNP after protein loading, demonstrating fast MNP recovery under an external magnetic field. This MNP is expected to provide a versatile and modular platform to achieve effective and specific immobilization of other functional proteins, enabling easy reuse and storage.

Recognition and differentiation of dural puncture click sensation: A subjective and objective prospective study of dural puncture forces using fine-gauge spinal needles

BACKGROUND

We hypothesized that the click perceived when puncturing the dura-arachnoid with fine-gauge spinal needles can be subjectively identified, and investigated whether it may be distinguishable among different needle types.

METHODS

Subjective and objective evaluations were performed. First, physicians punctured the polyamide film or porcine dura mater (n = 70 and n = 20, respectively) with seven types of spinal needles and numerically evaluated the perceived click sensations. Using an 11-point numerical rating scale (from "0" for "no click sensation" to "10" for "the strongest click perceived") data, subjective differentiation among needle types was assessed. Second, in the objective part of the study, total forces elicited by polyamide film or porcine dura mater punctures with each needle were measured using a biomechanical testing device, and load-displacement curves evaluated. Third, the results of subjective and objective evaluations were compared.

RESULTS

All participants recognized the click and could discriminate among needles of different tip shape. The load-displacement curves for polyamide film and porcine dura mater were similar and needle-specific. The subjective numerical rating scale values corresponded well with the objectively measured changes in total forces (R2 = 0.862 and R2 = 0.881 for polyamide film and porcine dura mater, respectively), indicating that an increase in the largest drop in total force value of 0.30 N or 0.21 N would produce an increase of numerical rating scale value of 1 for polyamide film and porcine dura mater, respectively.

CONCLUSIONS

We provide an objective proof of the click sensation felt upon dural puncture using different fine-gauge spinal needles. Click recognition could be used as an additional indicator of successful spinal puncture.

Generation of Recombinant Primary Human B Lymphocytes Using Non-Viral Vectors

Although the development of gene delivery systems based on non-viral vectors is advancing, it remains a challenge to deliver plasmid DNA into human blood cells. The current "gold standard", namely linear polyethyleneimine (l-PEI 25 kDa), in particular, is unable to produce transgene expression levels >5% in primary human B lymphocytes. Here, it is demonstrated that a well-defined 24-armed poly(2-dimethylamino) ethyl methacrylate (PDMAEMA, 755 kDa) nano-star is able to reproducibly elicit high transgene expression (40%) at sufficient residual viability (69%) in primary human B cells derived from tonsillar tissue. Moreover, our results indicate that the length of the mitogenic stimulation prior to transfection is an important parameter that must be established during the development of the transfection protocol. In our hands, four days of stimulation with rhCD40L post-thawing led to the best transfection results in terms of TE and cell survival. Most importantly, our data argue for an impact of the B cell subsets on the transfection outcomes, underlining that the complexity and heterogeneity of a given B cell population pre- and post-transfection is a critical parameter to consider in the multiparametric approach required for the implementation of the transfection protocol.

Thermal insulating, light-weight and conductive cellulose/aramid nanofibers composite aerogel for pressure sensing

Conductive nanocellulose aerogels have attracted significant attention in pressure sensing for wearable devices owing to lightweight, sustainability and good chemical stability. Limited by its flammability and weak mechanical properties, aramid nanofiber (ANF) was designed as reinforcement to overcome the shortcoming mentioned above. Herein, the unidirectional freeze casting method was proposed to fabricate nanocellulose/aramid nanofiber (CA) aerogel. Then, the CA/PPy (CAP) aerogel was obtained by using the oriented structure of CA aerogel as a template for inducing conductive polypyrrole (PPy) in-situ formation inside the composite aerogel. The conductive aerogel with the ordered microstructure exhibited the anisotropic mechanical properties and thermal conductivity. And it could withstand high temperature without any destruction phenomenon. Moreover, the aerogel sensor revealed high strain sensitivity and satisfactory electrochemical performance. Lightweight CAP aerogel with controllable alignment, sensitive sensing property and thermal stability is very promising in pressure sensor under some extreme conditions.

Tailoring the Architecture of Cationic Polymer Brush-Modified Carbon Nanotubes for Efficient siRNA Delivery in Cancer Immunotherapy

The facile and controlled fabrication of homogeneously grafted cationic polymers on carbon nanotubes (CNTs) remains poorly investigated, which further hinders the understanding of interactions between functionalized CNTs with different nucleic acids and the rational design of appropriate gene delivery vehicles. Herein, we describe the controlled grafting of cationic poly(2-dimethylaminoethylmethacrylate) brushes on CNTs via surface-initiated atom transfer radical polymerization integrated with mussel-inspired polydopamine chemistry. The binding of nucleic acids with different brush-CNT hybrids discloses the highly architectural-dependent behavior with dense short brush-coated CNTs displaying the highest binding among all the other hybrids, namely, dense long, sparse long, and sparse short brush-coated CNTs. Additionally, different chemistries of the brush coatings were shown to influence the biocompatibility, cellular uptake, and silencing efficiency in vitro. This platform provides great flexibility for the design of polymer brush-CNT hybrids with precise control over their structure-activity relationship for the rational design of nucleic acid delivery systems.

One-step preparation of antimicrobial silicone materials based on PDMS and salicylic acid: insights from spatially and temporally resolved techniques

In this work, we introduce a one-step strategy that is suitable for continuous flow manufacturing of antimicrobial PDMS materials. The process is based on the intrinsic capacity of PDMS to react to certain organic solvents, which enables the incorporation of antimicrobial actives such as salicylic acid (SA), which has been approved for use in humans within pharmaceutical products. By combining different spectroscopic and imaging techniques, we show that the surface properties of PDMS remain unaffected while high doses of the SA are loaded inside the PDMS matrix. The SA can be subsequently released under physiological conditions, delivering a strong antibacterial activity. Furthermore, encapsulation of SA inside the PDMS matrix ensured a diffusion-controlled release that was tracked by spatially resolved Raman spectroscopy, Attenuated Total Reflectance IR (ATR-IR), and UV-Vis spectroscopy. The biological activity of the new material was evaluated directly at the surface and in the planktonic state against model pathogenic bacteria, combining confocal laser scanning microscopy, electron microscopy, and cell viability assays. The results showed complete planktonic inhibition for clinically relevant strains of Staphylococcus aureus and Escherichia coli, and a reduction of up to 4 orders of magnitude for viable sessile cells, demonstrating the efficacy of these surfaces in preventing the initial stages of biofilm formation. Our approach adds a new option to existing strategies for the antimicrobial functionalisation of a wide range of products such as catheters, wound dressings and in-dwelling medical devices based on PDMS.

Ultrasound-assisted production and optimization of mini-emulsions in a microfluidic chip in continuous-flow

The use of ultrasound to generate mini-emulsions (50 nm to 1 μm in diameter) and nanoemulsions (mean droplet diameter < 200 nm) is of great relevance in drug delivery, particle synthesis and cosmetic and food industries. Therefore, it is desirable to develop new strategies to obtain new formulations faster and with less reagent consumption. Here, we present a polydimethylsiloxane (PDMS)-based microfluidic device that generates oil-in-water or water-in-oil mini-emulsions in continuous flow employing ultrasound as the driving force. A Langevin piezoelectric attached to the same glass slide as the microdevice provides enough power to create mini-emulsions in a single cycle and without reagents pre-homogenization. By introducing independently four different fluids into the microfluidic platform, it is possible to gradually modify the composition of oil, water and two different surfactants, to determine the most favorable formulation for minimizing droplet diameter and polydispersity, employing less than 500 µL of reagents. It was found that cavitation bubbles are the most important mechanism underlying emulsions formation in the microchannels and that degassing of the aqueous phase before its introduction to the device can be an important factor for reduction of droplet polydispersity. This idea is demonstrated by synthetizing solid polymeric particles with a narrow size distribution starting from a mini-emulsion produced by the device.

Aptamer-Integrated Multianalyte-Detecting Paper Electrochemical Device

On-site detection of multiple small-molecule analytes in complex sample matrixes would be highly valuable for diverse biosensing applications. Paper electrochemical devices (PEDs) offer an especially appealing sensing platform for such applications due to their low cost, portability, and ease of use. Using oligonucleotide-based aptamers as biorecognition elements, we here for the first time have developed a simple, inexpensive procedure for the fabrication of aptamer-modified multiplex PEDs (mPEDs), which can robustly and specifically detect multiple small molecules in complex samples. These devices are prepared via an ambient vacuum filtration technique using carbon and metal nanomaterials that yields precisely patterned sensing architecture featuring a silver pseudo-reference electrode, a gold counter electrode, and three gold working electrodes. The devices are user-friendly, and the fabrication procedure is highly reproducible. Each working electrode can be readily modified with different aptamers for sensitive and accurate detection of multiple small-molecule analytes in a single sample within seconds. We further demonstrate that the addition of a PDMS chamber allows us to achieve detection in microliter volumes of biological samples. We believe this approach should be highly generalizable, and given the rapid development of small-molecule aptamers, we envision that facile on-site multi-analyte detection of diverse targets in a drop of sample should be readily achievable in the near future.

Smart, Naturally-Derived Macromolecules for Controlled Drug Release

A series of troxerutin-based macromolecules with ten poly(acrylic acid) (PAA) or poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) homopolymer side chains were synthesized by a supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) approach. The prepared precisely-defined structures with low dispersity (M_w/M_n < 1.09 for PAA-based, and M_w/M_n < 1.71 for PDMAEMA-based macromolecules) exhibited pH-responsive behavior depending on the length of the polymer grafts. The properties of the received polyelectrolytes were investigated by dynamic light scattering (DLS) measurement to determine the hydrodynamic diameter and zeta potential upon pH changes. Additionally, PDMAEMA-based polymers showed thermoresponsive properties and exhibited phase transfer at a lower critical solution temperature (LCST). Thanks to polyelectrolyte characteristics, the prepared polymers were investigated as smart materials for controlled release of quercetin. The influence of the length of the polymer grafts for the quercetin release profile was examined by UV–VIS spectroscopy. The results suggest the strong correlation between the length of the polymer chains and the efficiency of active substance release, thus, the adjustment of the composition of the macromolecules characterized by branched architecture can precisely control the properties of smart delivery systems.

Beyond Amphiphilic Balance: Changing Subunit Stereochemistry Alters the Pore-Forming Activity of Nylon-3 Polymers

Amphiphilic nylon-3 polymers have been reported to mimic the biological activities of natural antimicrobial peptides, with high potency against bacteria and minimal toxicity toward eukaryotic cells. Amphiphilic balance, determined by the proportions of hydrophilic and lipophilic subunits, is considered one of the most important features for achieving this activity profile for nylon-3 polymers and many other antimicrobial polymers. Insufficient hydrophobicity often correlates with weak activities against bacteria, whereas excessive hydrophobicity correlates with high toxicity toward eukaryotic cells. To ask whether factors beyond amphiphilic balance influence polymer activities, we synthesized and evaluated new nylon-3 polymers with two stereoisomeric subunits, each bearing an ethyl side chain and an aminomethyl side chain. Subunits that differ only in stereochemistry are predicted to contribute equally to amphiphilic balance, but we observed that the stereochemical difference correlates with significant changes in biological activity profile. Antibacterial activities were not strongly affected by subunit stereochemistry, but the ability to disrupt eukaryotic cell membranes varied considerably. Experiments with planar lipid bilayers and synthetic liposomes suggested that eukaryotic membrane disruption results from polymer-mediated formation of large pores. Collectively, our results suggest that factors other than amphiphilic balance influence the membrane activity profile of synthetic polymers. Subunits that differ in stereochemistry are likely to have distinct conformational propensities, which could potentially lead to differences in the average shapes of polymer chains, even when the subunits are heterochiral. These findings highlight a dimension of polymer design that should be considered more broadly in efforts to improve specificity and efficacy of antimicrobial polymers.

An alginate-PHMB-AgNPs based wound dressing polyamide nanocomposite with improved antibacterial and hemostatic properties

Wound dressing should be impenetrable against microorganisms and it should keep the wound wet. Gauze and polyamide (PA) substrate were treated with various concentrations of AgNPs (25, 50, 75, and 100 ppm), PHMB (0.2, 0.4, 0.6, 0.8, and 1% w/v), and constant concentration of alginate (0.5% W/V) using a simple dipping method. Prepared samples were characterized by various techniques including Fourier transform infrared spectroscopy and scanning electron microscopy. The results indicated that the particles were successfully applied onto both substrates with an average diameter of particle size of 78 nm on gauze and 172 nm on the PA substrate surface (based on 50 nanoparticles). Antibacterial activity of the prepared nanocomposite against Staphylococcus aureus (gram-positive) bacteria on PA substrate and gauze were evaluated using the disc diffusion method. The results indicated that the prepared nanocomposites offer favorable antibacterial properties and bacteria would not grow in culture media. The water uptake capacity test of the treated samples was assessed and the data demonstrated that the water absorption rate significantly increases on both treated substrates (gauze and PA substrate) due to the presence of alginate polymer. Also, observing the results of the coagulation test showed that treated samples caused blood clots on the dressing. This is due to the presence of alginate polymer. The present work demonstrates that the prepared samples offer excellent antibacterial properties and good water uptake capacity that capable of being a potential candidate for wound dressings. Due to the results, the produced PA substrate could be an appropriate replacement for the cotton gauze as a wound dressing.

Bacterial Biofilms on Polyamide Nanofibers: Factors Influencing Biofilm Formation and Evaluation

Electrospun polyamide (PA) nanofibers have great potential for medical applications (in dermatology as antimicrobial compound carriers or surgical sutures). However, little is known about microbial colonization on these materials. Suitable methods need to be chosen and optimized for the analysis of biofilms formed on nanofibers and the influence of their morphology on biofilm formation. We analyzed 11 PA nanomaterials, both nonfunctionalized and functionalized with AgNO₃, and tested the formation of a biofilm by clinically relevant bacteria (Escherichia coli CCM 4517, Staphylococcus aureus CCM 3953, and Staphylococcus epidermidis CCM 4418). By four different methods, it was confirmed that all of these bacteria attached to the PAs and formed biofilms; however, it was found that the selected method can influence the outcomes. For studying biofilms formed by the selected bacteria, scanning electron microscopy, resazurin staining, and colony-forming unit enumeration provided appropriate and comparable results. The values obtained by crystal violet (CV) staining were misleading due to the binding of the CV dye to the PA structure. In addition, the effect of nanofiber morphology parameters (fiber diameter and air permeability) and AgNO₃ functionalization significantly influenced biofilm maturation. Furthermore, the correlations between air permeability and surface density and fiber diameter were revealed. Based on the statistical analysis, fiber diameter was confirmed as a crucial factor influencing biofilm formation (p ≤ 0.01). The functionalization of PAs with AgNO₃ (from 0.1 wt %) effectively suppressed biofilm formation. The PA functionalized with a concentration of 0.1 wt % AgNO₃ influenced the biofilm equally as nonfunctionalized PA 8% 2 g/m². Therefore, biofilm formation could be affected by the above-mentioned morphology parameters, and ultimately, the risk of infections from contaminated medical devices could be reduced.

Biodegradable Plastics: Standards, Policies, and Impacts

Plastics are ubiquitous in our society. They are in our phones, clothes, bottles, and cars. Yet having improved our lives considerably, they now threaten our environment and our health. The associated carbon emissions and persistency of plastics challenge the fragile balance of many ecosystems. One solution is using biodegradable plastics. Ideally, such plastics are easily assimilated by microorganisms and disappear from our environment. This can help reduce the problems of climate change, microplastics, and littering. However, biodegradable plastics are still only a tiny portion of the global plastics market and require further efforts in research and commercialization. Here, a critical overview of the state of the art of biodegradable plastics is given. Using a material flow analysis, the challenges of the plastic market are highlighted, and with it the large market potential of biodegradable plastics. The environmental and socio-economic impact of plastics, government policies, standards and certifications, physico-chemical properties, and analytical techniques are covered. The Review concludes with a personal outlook on the future of bioplastics, based on our own experience with their development and commercialization.

Monolithic digital patterning of polydimethylsiloxane with successive laser pyrolysis

The patterning of polydimethylsiloxane (PDMS) into complex two-dimensional (2D) or 3D shapes is a crucial step for diverse applications based on soft lithography. Nevertheless, mould replication that incorporates time-consuming and costly photolithography processes still remains the dominant technology in the field. Here we developed monolithic quasi-3D digital patterning of PDMS using laser pyrolysis. In contrast with conventional burning or laser ablation of transparent PDMS, which yields poor surface properties, our successive laser pyrolysis technique converts PDMS into easily removable silicon carbide via consecutive photothermal pyrolysis guided by a continuous-wave laser. We obtained high-quality 2D or 3D PDMS structures with complex patterning starting from a PDMS monolith in a remarkably low prototyping time (less than one hour). Moreover, we developed distinct microfluidic devices with elaborated channel architectures and a customizable organ-on-a-chip device using this approach, which showcases the potential of the successive laser pyrolysis technique for the fabrication of devices for several technological applications.

Anisotropic Optical Shock Waves in Isotropic Media with Giant Nonlocal Nonlinearity

Dispersive shock waves in thermal optical media are nonlinear phenomena whose intrinsic irreversibility is described by time asymmetric quantum mechanics. Recent studies demonstrated that the nonlocal wave breaking evolves in an exponentially decaying dynamics ruled by the reversed harmonic oscillator, namely, the simplest irreversible quantum system in the rigged Hilbert spaces. The generalization of this theory to more complex scenarios is still an open question. In this work, we use a thermal third-order medium with an unprecedented giant Kerr coefficient, the m-cresol/nylon mixed solution, to access an extremely nonlinear, highly nonlocal regime and realize anisotropic shock waves with internal gaps. We compare our experimental observations to results obtained under similar conditions but in hemoglobin solutions from human red blood cells, and found that the gap formation strongly depends on the nonlinearity strength. We prove that a superposition of Gamow vectors in an ad hoc rigged Hilbert space, that is, a tensorial product between the reversed and the standard harmonic oscillators spaces, describes the beam propagation beyond the shock point. The anisotropy turns out from the interaction of trapping and antitrapping potentials. Our work furnishes the description of novel intriguing shock phenomena mediated by extreme nonlinearities.

Factors affecting microplastic retention and emission by a wastewater treatment plant on the southern coast of Caspian Sea

Understanding how wastewater treatment plants (WWTPs) process microplastics (MPs) will help informing management practices to reduce MP emissions to the environment. We show that composite 24 h samples taken at three replications from the outflow of the grit chamber, primary settling tank and clarifier of the WWTP of Sari City, on the southern coast of the Caspian Sea, contained 12667 ± 668, 3514 ± 543 and 423 ± 44.9 MP/m³, respectively. Fibers accounted for 94.9%, 89.9% and 77.5% of the total number of MPs, respectively. The MP removal efficiency was 96.7%. MP shape (fiber, particle), size and structure were the most important factors determining their removal in different steps of the wastewater treatment process. The structure of microfibers (polyester, acrylic and nylon) and the consequent higher density than water explained their high removal (72.3%) in the primary settling tank. However, size was more important in microparticle removal with particles ≥500 μm being removed in the primary settling tank and <500 μm in the clarifier unit. The smallest particles (37-300 μm) showed the lowest removal efficiency. The predominant types of fibers and particles were polyester and polyethylene, respectively, which are likely to originate from the washing of synthetic textiles and from microbeads in toothpaste and cosmetics. Despite the efficiency of the Sari WWTP in removing MPs, it remains a major emission source of MPs to the Caspian Sea due to its high daily discharge load.

Polyaramid-Based Flexible Antibacterial Coatings Fabricated Using Laser-Induced Carbonization and Copper Electroplating

A method for the fabrication of flexible electrical circuits on polyaramid substrates is presented based on laser-induced carbonization followed by copper electroplating. Locally carbonized flexible sheets of polyaramid (Nomex), by laser radiation, create rough and highly porous microstructures that show a higher degree of graphitization than thermally carbonized Nomex sheets. The found recipe for laser-induced carbonization creates conductivities of up to ∼45 S cm^-1, thereby exceeding that observed for thermally pyrolyzed materials (∼38 S cm^-1) and laser carbon derived from Kapton using the same laser wavelength (∼35 S cm^-1). The electrical conductivity of the carbonized tracks was further improved by electroplating with copper. To demonstrate the electrical performance, fabricated circuits were tested and improvement of the sheet resistance was determined. Copper films exhibit antimicrobial activity and were used to fabricate customized flexible antibacterial coatings. The integration of laser carbonization and electroplating technologies in a polyaramid substrate points to the development of customized circuit designs for smart textiles operating in high-temperature environments.

Hydrophobic interpenetrating polyamide-PDMS membranes for desalination, pesticides removal and enhanced chlorine tolerance

Hydrophobic membranes for desalination and toxic organic pollutant removal have been fabricated using polyamide - PDMS (polydimethylsiloxane) chemistries in a one-step protocol. The curing of polyamide and PDMS are orthogonal and co-curing both networks imparts hydrophobicity to the thin film composite membranes. The membranes exhibit increased adsorption of pesticides from the feed water along with maintaining excellent salt rejection capability (97% NaCl rejection), thus giving the membranes a multifunctional character. Three toxic pesticides have been used in this study to demonstrate the viability of combining osmosis desalination technology with organic matter adsorption. The membranes also show excellent resistance to fouling by toxic pesticides (85% salt rejection vs 67% for commercial membranes in the presence of pesticides) and significantly improved chlorine tolerance (93.8% salt rejection vs 86.5% for commercial membranes after 20 h of exposure to sodium hypochlorite solution).

A Near-Infrared Fluorogenic Pyrrole-Imidazole Polyamide Probe for Live-Cell Imaging of Telomeres

Telomeres are closely associated with cellular senescence and cancer. Although some techniques have been developed to label telomeres in living cells for study of telomere dynamics, few biocompatible near-infrared probes based on synthetic molecules have been reported. In this study, we developed a near-infrared fluorogenic pyrrole-imidazole polyamide probe (SiR-TTet59B) to visualize telomeres by conjugating a silicon-rhodamine (SiR) fluorophore with a tandem tetramer pyrrole-imidazole polyamide targeting 24 bp in the telomeric double-stranded (ds) DNA. SiR-TTet59B was almost nonfluorescent in water but increased its fluorescence dramatically on binding to telomeric dsDNA. Using a peptide-based delivery reagent, we demonstrated the specific and effective visualization of telomeres in living U2OS cells. Moreover, SiR-TTet59B could be used to observe the dynamic movements of telomeres during interphase and mitosis. This simple imaging method using a synthetic near-infrared probe could be a powerful tool for studies of telomeres and for diagnosis.