Good Salt Tolerance Research Articles

Dual-Channel Enzymatic Inhibition Measurement (DEIM) Coupling Isotope Substrate via Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry.

A novel dual-channel enzymatic inhibition measurement (DEIM) method was developed to improve the repeatability with light/heavy isotope substrates, producing reliable relative standard deviations (< 3%) by employing acetylcholinesterase (AChE) as the model enzyme. The matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) was adapted for enzyme-inhibited method due to its good salt-tolerance and high throughput; meanwhile, dual-channel enzymatic reactions were performed to improve the repeatability of each well. The acetylcholinesterase inhibition measurement was conducted by mixing the quenched enzyme reaction solution of blank group (with heavy isotope as substrate) and experimental group (with light isotope as substrate), of which the inhibition rate might be affected by isotope effects. Hence, inverse study and Km measurement were implemented to validate the method. The inverse study shows similar inhibition rate (68.9 and 70.3%) and the Km of isotope substrates are analogous (0.139 and 0.135mM), which demonstrated that the novel method is feasible to AChE inhibition measurement. Finally, the method was applied to herb extracts, half of which exhibit inhibition to AChE. The precise dual-channel enzymatic inhibition measurement (DEIM) method could be regarded as a promising approach to potential enzyme inhibitor screening. Graphical Abstract ᅟ.

Novel Hydrophobic Associating Polymer with Good Salt Tolerance.

A hydrophobic associating polymer named DiPHAM (acrylamide/sodium acrylamide-2-methylpropanesulfonic/sodium acrylate/N,N-di-n-dodecylacrylamide) with good salt tolerance was synthesized via photo-initiation polymerization. The critical association concentration (CAC) of DiPHAM was determined by viscosity changes to be 490 mg/L with different DiPHAM concentrations and particle sizes varied under such dynamic conditions. The influences of aqueous metal ions with different charges on its aqueous solution were investigated by measuring apparent viscosity, viscoelasticity, thixotropy, rheology, and particle size, and by SEM observation. The apparent viscosity of the DiPHAM solution was affected by metal ions to some extent, but the viscosity of the polymer can be still maintained at 55 mPa·s under 20 × 104 mg/L NaCl. Divalent metal ions show greater impact on DiPHAM aqueous solutions, but the polymer solutions showed resistance to the changes caused in viscosity, structure, and viscoelasticity by Ca2+ and Mg2+ ions. The salt tolerance of DiPHAM is due to the combination of hydrophobic association, the electrostatic shield, and double layer compression of the hydration shell. Increasing the ion concentration enhances the dehydration and further compresses the hydration shell, making the non-structural viscosity decrease, even “salting out”. Measurements of rheological properties showed that DiPHAM solutions could maintain a relatively high viscosity (0.6%-71 mPa·s/0.3%-50 mPa·s) after 120 min of continuous shearing (170 s−1) at 140 °C. Under high-salinity (5000 mg/L Ca2+/3000 mg/L Mg2+) conditions, the solution with 0.6 wt% DiPHAM still maintained a high viscosity (50 mPa·s/70 mPa·s) after continuously shearing for 120 min at 120 °C and 170 s−1. The good salt tolerance of DiPHAM can lead to a variety of applications, including in fracturing fluids for enhanced oil recovery (EOR) and in sewage treatment.

Comparison of nutrient uptake and antioxidative response among four Labiatae herb species under salt stress condition

ABSTRACTHerbs of the Labiatae have relatively low salt tolerance. They are widely grown in drylands, but salt stress there is a typical problem and may reduce yields. To examine their salt tolerance mechanisms, we grew basil, sage, thyme, and oregano in nutrient solution containing 50 mM NaCl and determined the biomass; contents of Na, K, and Mg in leaf blades, stems, and roots; contents of total chlorophyll, malondialdehyde (MDA), hydrogen peroxide in leaf blades; and activities of antioxidative enzymes in leaf blades. The salt tolerance decreased in the order of basil ≈ sage > thyme > oregano. The good salt tolerance of basil was explained by a significant increase in the activity of catalase, in addition to the low Na/K ratio of leaf blades due to the retention of Na in stems and roots and of K in leaf blades. The good salt tolerance of sage was explained by the low Na/K ratio in leaf blades and the prevention of lipid peroxidation by high antioxidative enzyme activities, despite its poorer management of nutrient uptake. In thyme, although catalase activity increased significantly to alleviate salt-induced oxidative stress caused by Na influx into all parts, low K and Mg allowed shoot weight in particular to decrease. In oregano, antioxidative responses appeared as significant increases in ascorbate peroxidase and glutathione reductase activity, and K was accumulated in leaf blades, but serious salt-induced oxidative stress caused by high Na influx into all parts reduced the growth of all parts. These results show that despite similar responses among species, salt tolerance is not necessarily the same. In this experiment, we revealed the salt tolerance mechanism of each of four Labiatae herbs by revealing their strengths and weaknesses in nutrient uptake and antioxidative responses.

Interfacial behaviour, wettability alteration and emulsification characteristics of a novel surfactant: Implications for enhanced oil recovery

The application of surfactants in enhanced oil recovery (EOR) processes aids in reducing interfacial tension at the oil-aqueous interface as well as altering the wetting nature of the reservoir rock. However, most commercial surfactants used in the petroleum industry are expensive. In an attempt to solve this issue, an anionic surfactant was synthesized from coconut oil as an alternative during oil recovery. The synthesized sodium ethyl ester sulfonate (SEES) surfactant was characterized by FT-IR, 1H NMR and TGA analyses. The critical micelle concentration (CMC) values of SEES surfactant were determined at different temperatures by electrical conductivity method. The interfacial tension (IFT) at the oil-aqueous interface was found to reduce to ultra-low magnitudes in the presence of salt. Alkali addition also plays a synergistic role in IFT reduction ability of SEES solutions. Surfactant solutions exhibited good salt tolerance levels and long-term thermal stability. SEES surfactant also showed improved wettability alteration property, changing the nature of oil-aged rock from intermediate-wet to water-wet. Synergism in wetting characteristics of SEES solution is achieved by salt addition. Additional recoveries of 20.05% was attained in the presence of 0.80 wt% SEES only, which further increased to 33.49% and 34.79% by the addition of 0.01% and 0.02% PHPA polymer respectively.

Fast swelling behaviors of thermosensitive poly(N‐isopropylacrylamide‐co‐methacryloxyethyltrimethyl ammonium chloride)/Na2WO4 cationic composite hydrogels

ABSTRACTA facile method was explored to synthesize thermosensitive poly[N‐isopropylacrylamide (NIPAM)‐co‐methacryloxyethyltrimethyl ammonium chloride (DMC)]/Na2WO4 cationic hydrogels via copolymerization of NIPAM and DMC in the presence of Na2WO4. Na2WO4 acted as both a physical crosslinking agent and a porogen precursor. The hydrogels were characterized by Fourier transform infrared spectroscopy, energy dispersive X‐ray, thermogravimetry, environmental scanning electron microscopy, and transmission electron microscopy. Effects of various salt solutions, pH solutions on swelling were investigated. Thermosensitivity of the hydrogels were also investigated in various polar solvents at different temperatures. The resultant hydrogel showed a fast swelling rate and good salt tolerance. The hydrogels reached the swelling equilibrium within 10 min. Moreover, the swelling ratio of the hydrogels increased with the increase of the polarity of the solvent. In the water, the swelling ratio decreased with the increasing of temperature, but remained at a high level even at 80 °C since the pore structure weaken the lower critical solution temperature effect of PNIPAM. The swelling ratio increased instead in low polar solvent, while it became negligible in nonpolar solvent with the increasing of temperature. The whole swelling kinetics was fit for Schott's pseudo‐second order model. The hydrogels have a great potential as catalysts and smart materials. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46375.

Facile and Green Approach to the Synthesis of Boron Nitride Quantum Dots for 2,4,6-Trinitrophenol Sensing.

A facile and green approach has been developed for synthesis of boron nitride quantum dots (BNQDs). The obtained BNQDs exhibit strong fluorescence and excellent stabilities, including high thermostability, good salt tolerance stability, pH-independence ability, and excellent antiphotobleaching capability. The strong inner filter effect between 2,4,6-trinitrophenol (TNP) and BNQDs resulted in fluorescence quenching of BNQDs. Thus, TNP can be selectively and sensitively detected in the concentration range of 0.25-200 μM, with a limit detection of 0.14 μM. The BNQD-based turn-off sensor shows potential prospects for rapidly and selectively detecting TNP in natural water samples without tedious sample pretreatment processes.

Covalent organic framework as efficient desorption/ionization matrix for direct detection of small molecules by laser desorption/ionization mass spectrometry

Covalent organic framework (COF) was explored as a novel matrix with a high desorption/ionization efficiency for direct detection of small molecules by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS). By using COF as an LDI MS matrix, we could detect not only biological micro molecules such as amino acids and fatty acids, but also emerging environmental pollutants like bisphenol S (BPS) and pyrene. With COF as the matrix, higher desorption/ionization efficiency, and less background interference were achieved than the conventional organic matrices. Good salt tolerance (as high as 500 mM NaCl) and repeatability allowed the detection limit of amino acids was 90 fmol. In addition, COF matrix performed well for amino acids analysis in the honey sample. The ionization mechanism was also discussed. These results demonstrate that COF is a powerful matrix for small molecules analysis in real samples by MS.

Full-Range pH Stable Au-Clusters in Nanogel for Confinement-Enhanced Emission and Improved Sulfide Sensing in Living Cells.

The sensitive and selective detection of hydrogen sulfide is of great importance due to its crucial role in pathological and physiological processes. Herein, we report a novel fluorescent platform, AuNCs@GC, for selective detection of hydrogen sulfide in living cells by impregnating the Au nanoclusters (AuNCs) into a biocompatible cationic polymer matrix, glycol-chitosan (GC) nanogel. The confinement effect significantly increased the emissive Au(I) units, resulting in a 6-fold enhancement of quantum yield (from 6.38% to 36.42%). In addition, the prepared positively charged AuNCs@GC nanogel exhibits excellent selectivity and improved sensitivity to aqueous sulfides. Moreover, the as-fabricated AuNCs@GC showed very good biocompatibility and super fluorescence stability across the full pH range and good salt tolerance, which demonstrated excellent adaptability toward intracellular sulfide imaging.

Study on the self-assembly properties of surface active hydrophobically associating polyacrylamide with nonionic surfmer units

A novel class of hydrophobic associated copolymers (PASC) with nonionic surfmer was synthesized. These copolymers are the copolymerization product of acrylamide (AM), 2-(acrylamido)-2- methyl propane sulfonic acid (AMPS) and different contents of nonionic surfmer (CP). Macroscopic and microscopic self-assembly associative properties in solutions of PASC, as well as the effects of salt and temperature on the associative behavior were studied via viscosimetry, scanning electron microscope (SEM), atomic force microscope (AFM), rheology and fluorescence spectroscopy (FS). The results show that the introduced nonionic surfmer along polymer chain can lead to a strong intermolecular hydrophobic association in water. The viscosity and surface activity increased with the increase of polymer concentration and nonionic surfmer concentration. Additionally, the polymer showed a good thermal stability and good salt tolerance. Contact angle studies shows that PASC solution has good potential on change of wettability from oil-wet to water-wet. All of these properties indicate that the polymer is an excellent chemical for chemical enhanced oil recovery.

MIL-101(Cr) as matrix for sensitive detection of quercetin by matrix-assisted laser desorption/ionization mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has been proven as a useful and advanced technique in the identification of polymers and proteins. However, MALDI-TOF-MS still has the unavoidable drawback of self-signal interference with traditional organic matrices, which could suppress and overlap with the analyte signals in the low-mass region. In this work, MIL-101(Cr), a kind of metal-organic frameworks which possess high molecular weight, π-conjugated 3-D structure, coordinately unsaturated chromium sites (CUS) and strong absorption in the UV range, was employed to replace traditional organic matrices, and it was found that MIL-101(Cr) can dramatically eliminate the background peaks, showing high signal-to-noise level in the analysis of small molecules. As proof-of-concept, quercetin, daidzein, genistein and naringenin, members of flavonol family which widely exists in food and natural products, were successfully determined by utilizing MIL-101(Cr) as the surface-assisted matrix, and the detection of quercetin was sensitive with good salt tolerance and reproducibility. Under optimal conditions, the mass peak intensity exhibited good linear relationships in the range from 0.25µg/mL-7.00µg/mL for quercetin (R2=0.996) with detection limit 2.11ng/mL (3σ/k), making the identification of quercetin in sophora japonica successfully. With this strategy we have demonstrated the potentiality of MIL-101(Cr) nanomaterials as MALDI-MS matrix for the detection of small molecules.

Screening of Toxic Chemicals in a Single Drop of Human Whole Blood Using Ordered Mesoporous Carbon as a Mass Spectrometry Probe.

Surface-enhanced laser desorption/ionization (SELDI) is a versatile and high-throughput mass spectrometry (MS) technique that uses a probe for extraction, enrichment, desorption, and ionization of target analytes. Here we report ordered mesoporous carbon as a new SELDI probe for rapid screening and identification of trace amount of toxic chemicals in a single drop of human whole blood without complicated sample preparation procedures. We demonstrate that ordered mesoporous carbon not only can selectively enrich a wide variety of low-mass toxic compounds from whole blood samples but also can be used as an excellent matrix to assist the laser desorption/ionization process of small molecules with low background noise, high repeatability, and good salt tolerance. High sensitivity (detection limits at ppt levels) and good reproducibility for typical toxic compounds were obtained. With CMK-8 as a SELDI probe, we successfully identified and screened six perfluorinated compounds in a single drop of whole blood collected from workers in a perfluorochemical plant. The method was also validated with complex samples such as human urine and environmental water samples. With distinct advantages such as simplicity, rapidness, minimal sample requirement, and high reliability, this method keeps great promise for various aspects of application.

Expression and characterization of a new esterase with GCSAG motif from a permafrost metagenomic library.

As a result of construction and screening of a metagenomic library prepared from a permafrost-derived microcosm, we have isolated a novel gene coding for a putative lipolytic enzyme that belongs to the hormone-sensitive lipase family. It encodes a polypeptide of 343 amino acid residues whose amino acid sequence displays maximum likelihood with uncharacterized proteins from Sphingomonas species. A putative catalytic serine residue of PMGL2 resides in a new variant of a recently discovered GTSAG sequence in which a Thr residue is replaced by a Cys residue (GCSAG). The recombinant PMGL2 was produced in Escherichia coli cells and purified by Ni-affinity chromatography. The resulting protein preferably utilizes short-chain p-nitrophenyl esters (C4 and C8) and therefore is an esterase. It possesses maximum activity at 45°C in slightly alkaline conditions and has limited thermostability at higher temperatures. Activity of PMGL2 is stimulated in the presence of 0.25-1.5 M NaCl indicating the good salt tolerance of the new enzyme. Mass spectrometric analysis demonstrated that N-terminal methionine in PMGL2 is processed and cysteine residues do not form a disulfide bond. The results of the study demonstrate the significance of the permafrost environment as a unique genetic reservoir and its potential for metagenomic exploration.

A novel surfactant-, NaCl-, and protease-tolerant β-mannanase from Bacillus sp. HJ14.

A glycoside hydrolase family 5 β-mannanase-encoding gene was cloned from Bacillus sp. HJ14 isolated from saline soil in Heijing town. Coding sequence of mature protein (without the predicted signal peptide from M1 to A30) was successfully expressed in Escherichia coli BL21 (DE3). Purified recombinant mannanase (rMan5HJ14) exhibited optimal activity at pH6.5 and 65°C. The enzyme showed good salt tolerance, retaining more than 56% β-mannanase activity at 3.0-30.0% (w/v) NaCl and more than 94% of the initial activity after incubation with 3.0-30.0% (w/v) NaCl at 37°C for 60min. Almost no mannanase activity was lost after incubation of rMan5HJ14 with trypsin, proteinase K, and Alcalase at 37°C for 60min. Surfactants and chelating agents, namely SDS, CTAB, Tween 80, Triton X-100, EDTA, and sodium tripolyphosphate, showed little or no effect (retaining >82.4% activity) on enzymatic activity. Liquid detergents, namely Tupperware, Walch, Bluemoon, Tide, and OMO, also showed little or no effect (retaining >72.4% activity) on enzymatic activity at 0.5-2.0% (v/v). The enzyme further presents a high proportion (11.97%) of acidic amino acid residues (D and E), which may affect the SDS and NaCl tolerance of the enzyme. Together, the mannanase may be an alternative for potential use in liquid detergent industry.

New insights into the hydroquinone (HQ)–hexamethylenetetramine (HMTA) gel system for water shut-off treatment in high temperature reservoirs

Aiming at water shut-off in high temperature reservoirs, the hydroquinone (HQ)–hexamethylenetetramine (HMTA) gel system was studied. The gelation performance and effects of various parameters were systematically evaluated. With increase of the concentrations and temperature, gelation time decreases and gel strength increases. In addition, gelation rate and gel strength were enhanced on adding acid. Moreover, the gel system shows good salt tolerance. The thermal stability measurement indicates that the gel can maintain stability up to 140°C. Uniformly distributed three-dimensional network structure was formed in the gel. At last, the gelation mechanism was proposed, illuminating the detailed gelation process clearly.

Negative Ion Laser Desorption/Ionization Time-of-Flight Mass Spectrometric Analysis of Small Molecules Using Graphitic Carbon Nitride Nanosheet Matrix.

Ultrathin graphitic carbon nitride (g-C3N4) nanosheets served as a novel matrix for the detection of small molecules by negative ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was described for the first time. In comparison with conventional organic matrices and graphene matrix, the use of g-C3N4 nanosheet matrix showed free matrix background interference and increased signal intensity in the analysis of amino acids, nucleobases, peptides, bisphenols (BPs), and nitropolycyclic aromatic hydrocarbons (nitro-PAHs). A systematic comparison of g-C3N4 nanosheets with positive and negative ion modes revealed that mass spectra produced by g-C3N4 nanosheets in negative ion mode were featured by singly deprotonated ion without matrix interference, which was rather different from the complicated alkali metal complexes in positive ion mode. Good salt tolerance and reproducibility allowed the determination of 1-nitropyrene (1-NP) in sewage, and its corresponding detection limit was lowered to 1 pmol. In addition, the ionization mechanism of the g-C3N4 nanosheets as matrix was also discussed. The work expands its application scope of g-C3N4 nanosheets and provides an alternative approach for small molecules.

Characterization of an exo-inulinase from Arthrobacter: A novel NaCl-tolerant exo-inulinase with high molecular mass

A glycoside hydrolase family 32 exo-inulinase gene was cloned from Arthrobacter sp. HJ7 isolated from saline soil located in Heijing town. The gene encodes an 892-residue polypeptide with a calculated mass of 95.1 kDa and a high total frequency of amino acid residues G, A, and V (30.0%). Escherichia coli BL21 (DE3) cells were used as hosts to express the exo-inulinase gene. The recombinant exo-inulinase (rInuAHJ7) showed an apparently maximal activity at pH 5.0–5.5 and 40–45°C. The addition of 1.0 and 10.0 mM Zn2+ and Pb2+ had little or no effect on the enzyme activity. rInuAHJ7 exhibited good salt tolerance, retaining more than 98% inulinase activity at a concentration of 3.0%–20.0% (w/v) NaCl. Fructose was the main product of inulin, levan, and Jerusalem artichoke tubers hydrolyzed by the enzyme. The present study is the first to report the identification and characterization of an Arthrobacter sp exo-inulinase showing a high molecular mass of 95.1 kDa and NaCl tolerance. These results suggest that the exo-inulinase might be an alternative material for potential applications in processing seafood and other foods with high saline contents, such as marine algae, pickles, and sauces.

Molecular cloning and expression analysis of RrNHX1 and RrVHA-c genes related to salt tolerance in wild Rosa rugosa

Salt stress is one important factor influencing the growth and development of plants, and salt tolerance of plants is a result of combined action of multiple genes and mechanisms. Rosa rugosa is not only an important ornamental plant, but also the natural aromatic plant of high value. Wild R. rugosa which is naturally distributed on the coast and islands of China has a good salt tolerance due to the special living environment. Here, the vacuolar Na+/H+ reverse transporter gene (NHX1) and the vacuolar H+-ATPase subunit C gene (VHA-c) closely related to plant salt tolerance were isolated from wild R. rugosa, and the expression patterns in R. rugosa leaves of the two genes under NaCl stress were determined by real-time quantitative fluorescence PCR. The results showed that the RrNHX1 protein is a constitutive Na+/H+ reverse transporter, the expression of the RrNHX1 gene first increased and then decreased with the increasing salt concentration, and had a time-controlled effect. The RrVHA-c gene is suggestive of the housekeeping feature, its expression pattern showed a similar variation trend with the RrNHX1 gene under the stress of different concentrations of NaCl, and its temporal expression level under 200mM NaCl stress presented bimodal change. These findings indicated that RrNHX1 and RrVHA-c genes are closely associated with the salt tolerance trait of wild R. rugosa.

Physiological responses of Kosteletzkya virginica to coastal wetland soil.

Effects of salinity on growth and physiological indices of Kosteletzkya virginica seedlings were studied. Plant height, fresh weight (FW), dry weight (DW), and net photosynthetic rate (P n) increased at 100 mM NaCl and slightly declined at 200 mM, but higher salinity induced a significant reduction. Chlorophyll content, stomatal conductance (G s), intercellular CO2 concentration (C i), and transpiration rate (E) were not affected under moderate salinities, while markedly decreased at severe salinities except for the increased C i at 400 mM NaCl. Furthermore, no significant differences of F v/F m and ΦPSII were found at lower than 200 mM NaCl, whereas higher salinity caused the declines of F v/F m, ΦPSII, and qP similar to P n, accompanied with higher NPQ. Besides, salt stress reduced the leaf RWC, but caused the accumulation of proline to alleviate osmotic pressure. The increased activities of antioxidant enzymes maintained the normal levels of MDA and relative membrane permeability. To sum up, Kosteletzkya virginica seedlings have good salt tolerance and this may be partly attributed to its osmotic regulation and antioxidant capacity which help to maintain water balance and normal ROS level to ensure the efficient photosynthesis. These results provided important implications for Kosteletzkya virginica acting as a promising multiuse species for reclaiming coastal soil.

N-doped graphene: an alternative carbon-based matrix for highly efficient detection of small molecules by negative ion MALDI-TOF MS.

Gas-phase N-doped graphene (gNG) was synthesized by a modified thermal annealing method using gaseous melamine as nitrogen source and then for the first time applied as a matrix in negative ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for small molecule analysis. Unlike the complicated adducts produced in positive ion mode, MS spectra obtained on gNG matrix in negative ion mode was only featured by deprotonated molecule ion peaks without matrix interference. By the gNG assisted desorption/ionization (D/I) process, some applications were carried out on a wide range of low-molecular weight (MW) analytes including amino acids, fatty acids, peptides, anabolic androgenic steroids as well as anticancer drugs, with an extraordinary laser desorption/ionization (LDI) efficiency over traditional α-cyano-4-hydroxycinnamic acid (CHCA) and other carbon-based materials in the negative ion detection mode. By comparison of a series of graphene-based matrixes, two main factors of matrix gNG were unveiled to play a decisive role in assisting negative ion D/I process: a well-ordered π-conjugated system for laser absorption and energy transfer; pyridinic-doped nitrogen species functioning as deprotonation sites for proton capture on negative ionization. The good salt tolerance and high sensitivity allowed further therapeutic monitoring of anticancer drug nilotinib in the spiked human serum, a real case of biology. Signal response was definitely obtained between 1 mM and 1 μM, meeting the demand of assessing drug level in the patient serum. This work creates a new application branch for nitrogen-doped graphene and provides an alternative solution for small molecule analysis.

Enhanced Salt Tolerance of Polyurethane Based Multilayer Films

AbstractIn our previous study, polyurethane (PU) based multilayer films assembled with weak polyelectrolytes exhibited controllable loading and release properties, but would be decomposed in high salt solution. Herein, a strong polyelectrolyte, poly(styrene sulfonic acid) sodium (PSS), was introduced to fabricate multilayer films. The salt tolerance of the film was investigated by evaluating the loading and release profiles towards model drug in salt solution with different concentrations. Results showed that the release behavior of the film, as well as its loading capacity, can be tuned by varying the salt concentrations. And the film showed a good salt tolerance that can remain integrity even after 6 cycles of drug loading and release in 600 mmol·L−1 NaCl solution. It showed that the salt tolerance of PU based films can be greatly improved through assembling with strong polyelectrolyte.