Hydrophobic Length Research Articles

New Putative Antimicrobial Candidates: In silico Design of Fish-Derived Antibacterial Peptide-Motifs.

Antimicrobial resistance remains a great threat to global health. In response to the World Health Organizations’ global call for action, nature has been explored for novel and safe antimicrobial candidates. To date, fish have gained recognition as potential source of safe, broad spectrum and effective antimicrobial therapeutics. The use of computational methods to design antimicrobial candidates of industrial application has however, been lagging behind. To fill the gap and contribute to the current fish-derived antimicrobial peptide repertoire, this study used Support Vector Machines algorithm to fish out fish-antimicrobial peptide-motif candidates encrypted in 127 peptides submitted at the Antimicrobial Peptide Database (APD3), steered by their physico-chemical characteristics (i.e., positive net charge, hydrophobicity, stability, molecular weight and sequence length). The best two novel antimicrobial peptide-motifs (A15_B, A15_E) with the lowest instability index (−28.25, −22.49, respectively) and highest isoelectric point (pI) index (10.48 for each) were selected for further analysis. Their 3D structures were predicted using I-TASSER and PEP-FOLD servers while ProSA, PROCHECK, and ANOLEA were used to validate them. The models predicted by I-TASSER were found to be better than those predicted by PEP-FOLD upon validation. Two I-TASSER models with the lowest c-score of −0.10 and −0.30 for A15_B and A15_E peptide-motifs, respectively, were selected for docking against known bacterial-antimicrobial target-proteins retrieved from protein databank (PDB). Carbapenam-3-carboxylate synthase (PDB ID; 4oj8) yielded the lowest docking energy (−8.80 and −7.80 Kcal/mol) against motif A15_B and A15_E, respectively, using AutoDock VINA. Further, in addition to Carbapenam-3-carboxylate synthase, these peptides (A15_B and A15_E) were found to as well bind to membrane protein (PDB ID: 1by3) and Carbapenem synthetase (PDB: 1q15) when ClusPro and HPEPDOCK tools were used. The membrane protein yielded docking energy scores (DES): −290.094, −270.751; coefficient weight (CW): −763.6, 763.3 for A15_B and A15_E) whereas, Carbapenem synthetase (PDB: 1q15) had a DES of −236.802, −262.75 and a CW of −819.7, −829.7 for peptides A15_B and A15_E, respectively. Motif A15_B of amino acid positions 2–19 in Pleurocidin exhibited the strongest in silico antimicrobial potentials. This segment could be a good biological candidate of great application in pharmaceutical industries as an antimicrobial drug candidate.

Impact of hydrophobic tails of new phospho-zwitterionic surfactants on the structure, catalytic, and biological activities of AgNPs

In this study, three anionic-cationic zwitterionic Gemini surfactants containing three different hydrophobic tails were prepared and their chemical structures were confirmed by Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (NMR) spectroscopy. The hydrophobic tail of the synthesized phospho-zwitterionic Gemini surfactants significantly affected the morphological structure of silver nanoparticles (AgNPs) prepared using a photochemical reduction method, which utilized sunlight as a surplus source of a reducing agent. Increasing the hydrophobic tail length of the surfactant promoted the formation of AgNPs exhibiting smaller particle sizes with a uniform structure. Moreover, as confirmed by ultraviolet-visible (UV-Vis) spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM), these AgNPs displayed higher stability in solution than those synthesized in the presence of Gemini surfactants with a shorter hydrocarbon tail. The impact of tail variation on the catalytic and antimicrobial performance of AgNPs was also examined. The synthesized surfactant/AgNP systems showed remarkable catalytic activity in the removal of certain toxic pollutants, including para-nitrophenol (p-NP) and methylene blue (MB), which were converted into less toxic compounds in the presence of NaBH4. Notably, the surfactant exhibiting the longest chain hydrocarbon, i.e., ZGH, produced AgNPs with the highest catalytic activity. This is the first study concerning the effects of the surfactant tail on the catalytic activity of NPs. The good biological performance of the synthesized Gemini surfactants against sulfate-reducing bacteria (SRB) demonstrated their potential for application in mitigating the growth of SRB during petroleum treatment processes. The combination of the synthesized surfactants with AgNPs significantly enhanced their biological performance.

Effects of Hydrophobic Tail Length Variation on Surfactant-Mediated Protein Stabilization.

Recently, protein therapeutics have gained significant attention as a result of their enhanced selectivity and diminished side effects compared to traditional small-molecule drugs. Despite their advantages, protein formulations typically suffer from stability issues because of aggregation and denaturation during production and storage, often resulting in detrimental immune responses. Surfactants can be used to stabilize and protect proteins in solution by preventing protein adsorption onto interfaces or by forming protective structures in solution. Herein, a detailed structure-activity relationship study is described, demonstrating the role that hydrophobic tail length plays in surfactant-mediated stabilization of the model therapeutic protein IgG. The FM1000 series, originating from a surfactant scaffold that allows for easy structure modulation, was synthesized by a simple 2-step procedure. First, phenylalanine was acylated with a variety of acyl chlorides of differing lengths to yield n-acyl phenylalanine, which was then coupled to Jeffamine M1000, a polyethylene glycol-based amine, to yield the final surfactant. With this FM1000 series, it was observed that the 14 carbon-long tail surfactant (14FM1000) was optimal at preventing IgG aggregation compared to surfactants with tails that were longer or shorter. Using a combination of dynamic surface tensiometry and quartz crystal microbalance with dissipation, it was hypothesized that 14FM1000 was able to prevent IgG adsorption, and therefore aggregation, by adsorbing appreciably onto surfaces quickly. 14FM1000 had the fastest rate of initial adsorption compared to the other surfactants studied. Short-tail surfactants were slow to and did not adsorb appreciably onto surfaces, allowing IgG adsorption. Although long-tail surfactants were also slow to adsorb, allowing IgG to adsorb and aggregate, their equilibrium adsorption was strong. Additionally, 14FM1000 was the most reversibly adsorbed surfactant, likely improving its ability to desorb and adsorb quickly to transient surfaces, therefore protecting the IgG at each new hydrophobic surface and preventing aggregation. By understanding the structure-activity relationship between surfactants and protein stabilization, we move toward more efficient design of future surfactants increasing the stability and utility of important protein therapeutics.

Folate-Targeted Curcumin-Encapsulated Micellar Nanosystem for Chemotherapy and Curcumin-Mediated Photodynamic Therapy.

Curcumin (CUR) is a natural phenolic product used as a high-efficiency and low-toxicity anticancer drug and photosensitizer. However, it has a poor aqueous solubility and a lack of target specificity, which limits its clinical applications. Hence, we developed a folate-conjugated polymeric micelle to enhance the efficient delivery of CUR for effective cancer cell targeting and anticancer efficiency. A series of biocompatible folate-conjugated poly(2-(methacryloyloxy)ethylphosphoryl- choline)-b-poly(ε-caprolactone) (FPM) was synthesized with different hydrophobic lengths and folate contents. The prepared CUR-loaded micelles (CUR-FPM) possessed several superior properties, including an excellent drug loading capacity (6.3 ± 1.2%), improved CUR aqueous stability, fast-sustained CUR release in an acidic environment, and efficient intracellular production of reactive oxygen species. The in vitro cytotoxicity demonstrated that the CUR-FPM micelles efficiently suppressed the growth of HeLa cells (folate-receptor overexpression) compared to that of HT-29 cells, and a competition study showed less cytotoxic effect when free folic acid blocked the folate receptor, indicating the folate conjugation played the role of targeting the specific cells well. Moreover, the CUR-mediated photodynamic therapy (PDT) by CUR-FPM micelles under irradiation further inhibited the proliferation of cancer cells. All these results indicate that the CUR-FPM micelles could be a promising delivery system for folate-overexpressing cancer cells, complementary chemotherapy, and CUR-mediated photodynamic therapy.

Biotin-decorated all-HPMA polymeric micelles for paclitaxel delivery

To avoid poly(ethylene glycol)-related issues of nanomedicines such as accelerated blood clearance, fully N-2-hydroxypropyl methacrylamide (HPMAm)-based polymeric micelles decorated with biotin for drug delivery were designed. To this end, a biotin-functionalized chain transfer agent (CTA), 4-cyano-4-[(dodecylsulfanylthiocarbonyl)-sulfanyl]pentanoic acid (biotin-CDTPA), was synthesized for reversible addition–fragmentation chain-transfer (RAFT) polymerization. Amphiphilic poly(N-2-hydroxypropyl methacrylamide)-block-poly(N-2-benzoyloxypropyl methacrylamide) (p(HPMAm)-b-p(HPMAm-Bz)) with molecular weights ranging from 8 to 24 kDa were synthesized using CDTPA or biotin-CDTPA as CTA and 2,2′-azobis(2-methylpropionitrile) as initiator. The copolymers self-assembled in aqueous media into micelles with sizes of 40–90 nm which positively correlated to the chain length of the hydrophobic block in the polymers, whereas the critical micelle concentrations decreased with increasing hydrophobic block length. The polymer with a molecular weight of 22.1 kDa was used to prepare paclitaxel-loaded micelles which had sizes between 61 and 70 nm, and a maximum loading capacity of around 10 wt%. A549 lung cancer cells overexpressing the biotin receptor, internalized the biotin-decorated micelles more efficiently than non-targeted micelles, while very low internalization of both types of micelles by HEK293 human embryonic kidney cells lacking the biotin receptor was observed. As a consequence, the paclitaxel-loaded micelles with biotin decoration exhibited stronger cytotoxicity in A549 cells than non-targeted micelles. Overall, a synthetic pathway to obtain actively targeted poly(ethylene glycol)-free micelles fully based on a poly(HPMAm) backbone was established. These polymeric micelles are promising systems for the delivery of hydrophobic anticancer drugs.

Regulation Mechanism of Bubbling Deformation and Fracture Toughness of the Membrane by Asymmetric Phospholipids: A Model System Study.

Dynamic regulation of the deformation modulus and fracture toughness of a membrane is critical to organelles and cells for matching their conflicting needs of resilient and fractured behaviors. These properties implement the protection of the function in the normal condition and the fission function in the endocytosis condition of a membrane. Naturally, a membrane contains phospholipids that have different hydrophilic and hydrophobic group length. The diffusion and aggregation of the phospholipids with asymmetry of the hydrophilic-hydrophobic ratio on the membrane play a key role in regulating the mechanical behaviors passively to the external force. In present work, the effects of the asymmetry of phospholipids on the bubbling deformation and fracture toughness of the membrane to external stretching are investigated in a model system. A disk-shaped micelle formed from the blend of symmetric and asymmetric diblock copolymers in a selective solvent is considered as the membrane sheet. Its mechanically responsive behaviors are investigated by self-consistent field theory. By analyzing the evolution of different components during the stretching process, the mechanism of formation of the bubbling structure is revealed. Moreover, the fracture toughness depending on the asymmetry of the phospholipids is determined quantitatively.

Studying surface and thermodynamic behavior of a new multi-hydroxyl Gemini cationic surfactant and investigating their performance as corrosion inhibitor and biocide

Some of commercial materials, like monoethanolamine, chloroacetic acid, triethanolamine amine and vanillin have been used for constructing three Gemini cationic surfactants with different hydrophobic tail length labelled CMTC, LMTC & PMTC. The chemical structure of the new Gemini was confirmed by FTIR &1HNMR. The hydrophobic tail of the synthesized Gemini controls their behavior in solution at the three studied temperatures as studied by surface tension measurements. The PMTC Gemini cationic surfactants with longest tail length showed lowest critical micelle concentration; which also showed a decreasing trend with raising the solution temperature. The thermodynamics insight refer the higher tendency of the synthesized surfactants toward adsorption and micellization with both increasing the hydrophobicity and temperature. The prepared electronic rich surfactant showed good inhibiting against the steel corrosion in the aggressive 1.0 M HCl; which is correlated with the surfactant structure and the temperature. The PMTC surfactant showed highest inhibition efficiency 92.09% at 55 °C, due the longer hydrophobic tail exhibit higher adsorption affinity compared to shorter surfactant tail CMTC. The polarization measurement revealed that the three surfactants behave as mixed type inhibitors. The synthesized three electronic rich Gemini surfactants showed high antimicrobial activity against bacteria & fungi, which was found correlated with the surfactant hydrophobic behaviors.

A Comprehensive Study Based on the Application of Different Genre of Surface-Active Ionic Liquid and Alkali Combination Systems in Surfactant Flooding

In the present study, four surface-active ionic liquids (SAILs) having different head groups (phosphonium, pyridinium, pyrrolidinium, and imidazolium) but the same hydrophobic tail length and same ...

Light-responsive surfactants: Photochromic properties of water-soluble azobenzene derivatives

Light-responsive self-assembly systems have emerged as a promising tool for controlling a multitude of molecular and macroscopic processes. A number of sophisticated applications of surfactants based on the azobenzene moiety have already been demonstrated including drug delivery and induction of functional changes in biologically active compounds. In most of these applications the switching time between the two compound states is substantial. However, a small number of systematic studies on the relationship between the chemical structure of the compound on the kinetics of photoisomerization and the influence of experimental conditions led us to undertake the studies described in this paper. Changes in the spectral characteristics resulting from reversible photoinduced trans-cis isomerization reaction of selected azobenzene-based surfactants, differing in the hydrophobic tail length, were determined in aqueous solutions employing UV–Vis absorption spectroscopy. The effect of the hydrophobic tail length, surfactant concentration, molecular environment and light intensity on the efficiency and kinetics of photoisomerization were investigated. Due to the thermal stability of both photochromic forms, it is possible to reversibly switch between two different photostationary states of the light-responsive surfactant in a controlled manner using light of two wavelengths (ultraviolet and blue). The results demonstrates that both the increasing concentration of azobenzene amphiphile and the increasing hydrophobic pendant tail length slow down the trans-cis photoisomerization, while the photochromic efficiency remains constant.

Drug-Directed Morphology Changes in Polymerization-Induced Self-Assembly (PISA) Influence the Biological Behavior of Nanoparticles.

The effect of the hydrophobic block length on the morphologies of polymerization-induced self-assembled (PISA) nanoparticles is well understood. However, the influence of drug loading on the phase morphology of the nanoparticles during the PISA process, and the resulting biological function of PISA nanoparticles, has barely been investigated. In this work, we show that the addition of a drug, curcumin, during the PISA process shifts the phase diagram toward different morphologies. The PISA system was based on hydrophilic poly(2-(methacryloyloxy)ethylphosphorylcholine) (PMPC), which was chain extended with hydrophobic methyl methacrylate (MMA) in various concentrations of curcumin. According to transmission electron microscopy, the presence of curcumin led to the transition of, for example, worms to polymersome and micelles to worms analysis. To understand the interaction between polymer particles and drug, small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS), and fluorescence lifetime measurements were carried out. These measurements show that curcumin is predominantly located in the core in the case of micelles and worms while it is found in the shell of polymersomes. The change in morphology influences the cellular uptake by MCF-7 cells and the movement of the particles in multicellular cancer spheroids (3D model). With the increasing amount of drug, the cellular uptake of micelles and worms was enhanced with the increasing grafting density of MPC chains, which contrasts the decreasing cellular uptake in the higher drug-loaded polymersomes due to the lower shell hydration.

Chain-End Modifications and Sequence Arrangements of Antimicrobial Peptoids for Mediating Activity and Nano-Assembly.

Poly(N-substituted glycine) “peptoids” are an interesting class of peptidomimics that can resist proteolysis and mimic naturally found antimicrobial peptides (AMPs), which exhibit wide spectrum activity against bacteria. This work investigates the possibility of modifying peptoid AMP mimics (AMPMs) with aliphatic lipid “tails” to generate “lipopeptoids” that can assemble into micellar nanostructures, and evaluates their antimicrobial activities. Two families of AMPMs with different distributions of hydrophobic and cationic residues were employed—one with a uniform repeating amphiphilicity, the other with a surfactant-like head-to-tail amphiphilicity. To further evaluate the interplay between self-assembly and activity, the lipopeptoids were variously modified at the AMPM chain ends with a diethylene glycol (EG2) and/or a cationic group (Nlys-Nlys dipeptoid) to adjust amphiphilicity and chain flexibility. Self-assembly was investigated by critical aggregation concentration (CAC) fluorescence assays and dynamic light scattering (DLS). The structure of a key species was also verified by small-angle X-ray scattering (SAXS) and cryo-electron microscopy (cryo-EM). To screen for antibacterial properties, we measured the minimum inhibitory concentrations (MIC) against S. aureus, E. coli, and P. aeruginosa. We found that certain combinations of lipid tail and AMPM sequences exhibit increased antibacterial activity (i.e., decreased MICs). Perhaps counter-intuitively, we were particularly interested in increased MICs in combination with low CACs. Concealing antimicrobial interactions due to packing of AMPMs in nano-assemblies could pave the way to AMPMs that may be “inert” even if unintentionally released and prevent microbes from gaining resistance to the lipopeptoids. Overall, incorporation of EG2 significantly improved lipopeptoids packing while the hydrophobic tail length was found to have a major influence over the MIC. One particular sequence, which we named C15-EG2-(kss)4, exhibited a very low CAC of 34 μM (0.0075 wt.%) and a significantly increased MIC above values for the unmodified AMPM. With the sequence design trends uncovered from this study, future work will focus on discovering more species such as C15-EG2-(kss)4 and on investigating release mechanisms and the potency of the released lipopeptoids.

Curcumin loaded polymeric micelles of variable hydrophobic lengths by RAFT polymerization: Preparation and in-vitro characterization

Curcumin is a prominent natural anticancer drug candidate accompanied by major limitations such as remarkable hydrophobicity, instability, and poor bioavailability. In the present study, polymeric micelle encapsulation was addressed to improve the solubility and stability of curcumin. Methoxy poly (ethylene glycol)-b-poly (methyl methacrylate) (mPEG-b-PMMA) amphiphilic block copolymers with variable hydrophobic lengths were synthesized using the reversible addition-fragmentation chain transfer (RAFT) polymerization method. Block copolymers can be effectively self-assembled in the aqueous medium due to their amphiphilic nature giving rise to micellar nanoparticles. The assembly of the copolymers was evaluated in terms of critical micelle concentration (CMC) and particle size distribution, which indicated a very low CMC value. Afterward, curcumin was successfully loaded into the mPEG-b-PMMA micelles resulting in a significant 400-fold solubility enhancement. Moreover, the cytotoxicity assay revealed that curcumin-loaded mPEG-b-PMMA micelles notably inhibited the growth of SW-48 colorectal cancer cells, A2780 ovarian carcinoma cells, and HepG2 human hepatoma cells in a dose-dependent manner. The free radical scavenging activity of curcumin-loaded mPEG-b-PMMA micelles demonstrated that the encapsulation of curcumin led to greater stability, particularly in alkaline pH. Taking all together, the results suggest that mPEG-b-PMMA micelles, prepared at optimum hydrophobic length, can serve as a promising nanocarrier system in curcumin delivery.

Synthesis and Self-Assembly of Hydroxypropyl Methyl Cellulose-block-Poly(ε-caprolactone) Copolymers as Nanocarriers of Lipophilic Drugs

A series of amphiphilic diblock copolymers with different hydrophilic and hydrophobic block lengths were synthesized by reductive amination of hydroxypropyl methyl cellulose (HPMC) and end-function...

Interaction of bovine serum albumin with cationic imidazolium-containing amphiphiles bearing urethane fragment: Effect of hydrophobic tail length

Abstract Complexation ability of homologous series of amphiphiles bearing imidazolium and urethane moieties (IAC-n, n = 14, 16, 18) toward bovine serum albumin (BSA) has been investigated by various physico-chemical methods (tensiometry, fluorescence spectroscopy, spectrophotometry, dynamic and electrophoretic light scattering, circular dichroism, and transmission electron microscopy). It has been revealed, that aggregation thresholds of systems based on IAC-n could be 5–8-fold reduced by BSA addition. Fluorescent analysis allows to estimate that binding of components is favorably mediated by tryptophan amino acid residues and is driven by different forces depending on the length of amphiphile hydrophobic tail. In particular, dominate contribution of Van der Waals interactions to the complexation has been shown in the case of IAC-14 and IAC-16, while hydrophobic interactions prevailed for IAC-18. It has been demonstrated that amphiphile addition causes reversible unfolding of protein macromolecules in all cases. Spectrophotometry assay exhibits that amphiphile/BSA complexes have more significant solubilization capacity toward hydrophobic guest in comparison with individual IAC-n systems.

Protein Structure Prediction and Design in a Biologically Realistic Implicit Membrane

Protein design is a powerful tool for elucidating mechanisms of function and engineering new therapeutics and nanotechnologies. Although soluble protein design has advanced, membrane protein design remains challenging because of difficulties in modeling the lipid bilayer. In this work, we developed an implicit approach that captures the anisotropic structure, shape of water-filled pores, and nanoscale dimensions of membranes with different lipid compositions. The model improves performance in computational benchmarks against experimental targets, including prediction of protein orientations in the bilayer, ΔΔG calculations, native structure discrimination, and native sequence recovery. When applied to de novo protein design, this approach designs sequences with an amino acid distribution near the native amino acid distribution in membrane proteins, overcoming a critical flaw in previous membrane models that were prone to generating leucine-rich designs. Furthermore, the proteins designed in the new membrane model exhibit native-like features including interfacial aromatic side chains, hydrophobic lengths compatible with bilayer thickness, and polar pores. Our method advances high-resolution membrane protein structure prediction and design toward tackling key biological questions and engineering challenges.

Self-assembled micelles prepared from bio-based hydroxypropyl methyl cellulose and polylactide amphiphilic block copolymers for anti-tumor drug release

Fully bio-based amphiphilic diblock copolymers were synthesized from hydroxypropyl methyl cellulose (HPMC) and amino-terminated poly(l-lactide) (PLLA) or poly(l-lactide-co-dl-lactide) (PLA) by reductive amination. The resulting HPMC-PLLA and HPMC-PLA copolymers with various hydrophobic block lengths were characterized by NMR, DOSY-NMR and FT-IR. Micelles were obtained by self-assembly of copolymers in aqueous medium. The micelles are spherical in shape, and the micelle size ranges from 150 to 180 nm with narrow distribution. The critical micelle concentration decreases with increasing PLA block length. Paclitaxel was loaded in micelles. Enhanced drug loading is obtained with increase of PLA block length. A biphasic release profile is observed with a burst of 40% followed by slower release up to 80%. MTT assay indicates the good cytocompatibility of HPMC-PLA micelles. SRB assay shows a significant cytotoxicity of paclitaxel-loaded micelles against SK-BR-3cells. It is thus concluded that bio-based HPMC-PLA block copolymers could be promising nano-carrier of anti-tumor drugs.

Formation of Asymmetric and Symmetric Hybrid Membranes of Lipids and Triblock Copolymers.

Hybrid membranes formed by co-assembly of AxByAx (hydrophilic-hydrophobic-hydrophilic) triblock copolymers into lipid bilayers are investigated by dissipative particle dynamics. Homogeneous hybrid membranes are developed as lipids and polymers are fully compatible. The polymer conformations can be simply classified into bridge- and loop-structures in the membranes. It is interesting to find that the long-time fraction of loop-conformation () of copolymers in the membrane depends significantly on the hydrophilic block length (x). As x is small, an equilibrium always results irrespective of the initial conformation distribution and its value depends on the hydrophobic block length (y). For large x, tends to be time-invariant because polymers are kinetically trapped in their initial structures. Our findings reveal that only symmetric hybrid membranes are formed for small x, while membranes with stable asymmetric leaflets can be constructed with large x. The effects of block lengths on the polymer conformations, such as transverse and lateral spans ( and ) of bridge- and loop-conformations, are discussed as well.

Accumulation and associated phytotoxicity of novel chlorinated polyfluorinated ether sulfonate in wheat seedlings

Novel alternatives of perfluorooctane sulfonate (PFOS), chlorinated polyfluorinated ether sulfonates (Cl-PFAESs) are increasingly being detected in the aquatic and terrestrial environment. Previous studies mainly focused on aquatic biota; however, the knowledge about the ecotoxicological risk they pose to terrestrial plants was still lacking. In this study, the accumulation of two Cl-PFAES (6:2 and 8:2 Cl-PFAES) and PFOS in wheat seedlings at environmentally relevant levels (50 and 100 μg L−1) was investigated. Concentrations of Cl-PFAESs in the roots were an order of magnitude higher than those in shoots, indicating that they were primarily accumulated in the roots. The values of root and shoot bioconcentration factor was comparable between 6:2 Cl-PFAES and PFOS. However, these indexes of 8:2 Cl-PFAES were 42–91% higher and 70–76% lower than PFOS, respectively. As a result, 6:2 Cl-PFAES had a similar accumulation pattern as PFOS, whereas 8:2 Cl-PFAES was predominantly restricted to the roots, which might be attributed to their hydrophobicity and carbon chain length. In addition, at 250 mg L−1 of Cl-PFAESs, plant biomass and pigment content were 24–30% and 0.4–18%, respectively, which were lower than those of PFOS. As compared with PFOS, Cl-PFAESs induced higher levels of root membrane permeability, reactive oxygen species and malondialdehyde content, as well as reduced the activities of antioxidant enzymes and glutathione content. These suggested the occurrence of a severer oxidative damage and the breakdown of the antioxidant defence system in wheat cells. Therefore, we conclude that Cl-PFAESs might pose a higher potential threat to the environment than PFOS.

Interface crosslinked mPEG-b-PAGE-b-PCL triblock copolymer micelles with high stability for anticancer drug delivery

The stability of polymeric micelles is a key property for anticancer drug delivery. In this study, a novel amphiphilic triblock copolymer, methoxy poly(ethylene glycol)-b-poly(allyl glycidyl ether)-b-poly(ε-caprolactone) (mPEG-b-PAGE-b-PCL), with different hydrophobic lengths was designed and synthesized using the combination of two successive ring-opening polymerizations. The products were characterized using 1H NMR and gel permeation chromatography (GPC). The triblock copolymers could self-assemble into micelles to encapsulate doxorubicin (DOX). The diameter of the DOX-loaded micelles increased from 63 to 92 nm with increasing PCL block length in the copolymer composition. The interface of the mPEG-b-PAGE-b-PCL micelles was crosslinked by a thiol-ene reaction with 1,4-butanedithiol. The stability, drug release and in vitro cytotoxicity of the DOX-loaded micelles were studied. The results showed that the DOX-loaded micelles could be effectively endocytosed by cancer cells and have good antitumor efficacy. In addition, the crosslinked micelles (CLMs) had better tumor accumulation than the noncrosslinked micelles (NCLMs) after intravenous injection using the lipophilic dye DiR.

Monovalent anion selective anion-exchange membranes with imidazolium salt-terminated side-chains: Investigating the effect of hydrophobic alkyl spacer length

Ion-conductive polymers having highly ordered and well-defined phase-separated structures are potential materials for use as monovalent anion-selective membranes (MASMs). In this work, to investigate the effect of hydrophobic spacers, four side-chain-type imidazolium salt-tethered poly(arylene ether sulfone) anion-exchange membranes (AEMs) with different alkyl spacer lengths (–CH2– number: 3, 6, 9, and 12) were fabricated for use in electrodialysis (ED). Our investigations using atomic force microscopy, small angle X-ray scattering and X-ray diffraction demonstrate that the extended alkyl spacers change the nano-phase-separated structures, with an increased ion cluster space ranging from 3.29 nm to 7.76 nm, resulting from increased immiscibility between the additional hydrophobic alkyl spacers and (i) the hydrophobic aromatic backbones and (ii) the hydrophilic ion-conductive groups. In addition, with the extension of the alkyl spacer, chloride (Cl−) ion conductivity at 25 °C decreases from 16.4 mS cm−1 to 11.4 mS cm−1 and water uptake is reduced to 12.8% (20 °C). It is found that the as-prepared AEM with a hexyl alkyl spacer shows the superior perm-selectivity (Cl−/SO42−) of 7.10 (separation efficiency: 70.3%), as compared with three others (3.48, 6.81, and 4.26). This work thus presents an efficient strategy to guide the architectural design of novel MASMs.