Organic Solvent Environments Research Articles

Fouling behavior of protein in mixed solvent systems: A combined experimental and simulation study

Membrane fouling in organic solvent environments remains poorly explored despite its significance in chemical and pharmaceutical industries. This study uses molecular dynamics (MD) simulations and experiments to explore lysozyme fouling in water, as well as four organic solvent environments, namely, 30 % v/v and 50 % v/v isopropyl alcohol (IPA), and 30 % v/v and 50 % v/v dimethyl sulfoxide (DMSO). Experimentally, flux declines were least with IPA and worst with DMSO. Biased simulations indicate the worst fouling in DMSO is tied to the most attractive lysozyme-membrane energy in the presence of DMSO. However, the relative attractive energies for IPA and water do not agree with the relative flux declines, indicating other factors are more influential when the interaction energies are similar. To understand the gentler flux decline for IPA despite the more attractive lysozyme-membrane energy, radial distribution functions (RDFs) were obtained from unbiased simulations. Analyses of the water and solvent films around both the membrane and the lysozyme molecule reveal that the denser water film around both entities induced by the presence of IPA serves as a barrier for fouling and thus leads to less flux decline. The results underscore the complexity of fouling in organic solvent systems, cautioning against direct use of the understanding based on aqueous systems.

Scalable and adaptable two-ligand co-solvent transfer methodology for gold bipyramids to organic solvents.

Large and faceted nanoparticles, such as gold bipyramids, presently require synthesis using alkyl ammonium halide ligands in aqueous conditions to stabilize the structure, which impedes subsequent transfer and suspension of such nanoparticles in low polarity solvents despite success with few nanometer gold nanoparticles of shapes such as spheres. Phase transfer methodologies present a feasible avenue to maintain colloidal stability of suspensions and move high surface energy particles into organic solvent environments. Here, we present a method to yield stable suspensions of gold bipyramids in low-polarity solvents, including methanol, dimethylformamide, chloroform, and toluene, through the requisite combination of two capping agents and the presence of a co-solvent. By utilizing PEG-SH functionalization for stability, dodecanethiol (DDT) as the organic-soluble capping agent, and methanol to aid in the phase transfer, gold bipyramids with a wide-range of aspect ratios and sizes can be transferred between water and chloroform readily and maintain colloidal stability. Subsequent transfer to various organic and low-polarity solvents is then demonstrated for the first time.

Recent advances in the fabrication of organic solvent nanofiltration membranes using covalent/metal organic frameworks.

Organic solvent nanofiltration (OSN) has evolved as a vital technological frontier with paramount significance in the separation and purification of organic solvents. Its implication is particularly prominent in industries such as pharmaceuticals, petrochemicals, and environmental remediation. This comprehensive review, meticulously navigates through the current state of research in OSN membranes, unveiling both the critical challenges and promising opportunities that beckon further exploration. The central focus of this review is on the unique utilization of covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) in OSN membrane design, leveraging their distinctive structural attributes-tunable porosity, robust chemical stability, and molecular sieving capabilities. These qualities position them as exceptional candidates for crafting membranes tailored to the intricacies of organic solvent environments. Our investigation extends into the fundamental principles that render COFs and MOFs adept in OSN applications, dissecting their varied fabrication methods while offering insights into the advantages and limitations of each. Moreover, we address environmental and sustainability considerations in the use of COF and MOF-based OSN membranes. Furthermore, we meticulously present the latest advancements and innovations in this burgeoning field, charting a course toward potential future directions and emerging research areas. By underscoring the challenges awaiting exploration, this review not only provides a panoramic view of the current OSN landscape but also lays the groundwork for the evolution of efficient and sustainable OSN technologies, specifically harnessing the unique attributes of COFs and MOFs.

Effects of Microfluidic Shear on the Plasmid DNA Structure: Implications for Polymeric Gene Delivery Vectors.

Microfluidic manufacturing of advanced gene delivery vectors necessitates consideration of the effects of microfluidic shear forces on the structural integrity of plasmid DNA (pDNA). In this paper, we expose pDNA to variable shear forces in a two-phase, gas-liquid microfluidic reactor and apply gel electrophoresis to analyze the products of on-chip shear-induced degradation. The effects of shear rate, solvent environment, pDNA size, and copolymer complexation on shear-induced degradation are investigated. We find that small naked pDNA (pUC18, 2.7 kb) exhibits shear rate-dependent shear degradation in the microfluidic channels in a mixed organic solvent (dioxane/water/acetic acid; 90/10/<0.1 w/w/w), with the extents of both supercoil isoform relaxation and complete fragmentation increasing as the maximum shear rates increase from 4 × 105 to 2 × 106 s-1. However, over the same range of shear rates, the same pDNA sample shows no evidence of microfluidic shear-induced degradation in a pure aqueous environment. Quiescent control experiments in the same mixed organic solvent prove that a combination of solvent and shear forces is involved in the observed shear-induced degradation. Furthermore, we show that shear degradation effects in mixed organic solvents can be significantly attenuated by complexation of pDNA with the block copolymer polycaprolactone-block-poly(2-vinylpyridine) prior to exposure to microfluidic shear. Finally, we demonstrate that medium (pDSK519, 8.1 kb) and large (pRK290, 20 kb) naked pDNA are more sensitive to shear-induced microfluidic degradation in the mixed organic solvent environment than small pDNA, with both plasmids showing complete fragmentation even at the lowest shear rate, although we found no evidence of shear-induced damage in water for the largest investigated naked pDNA even at the highest flow rate. The resulting understanding of the interplay of the solvent and shear effects during microfluidic processing should inform microfluidic manufacturing routes to new gene therapy formulations.

One-step synthesis of low-dimensional copper-based nanomaterials with intrinsic antioxidant properties

Copper nanomaterials have remarkable application potential in electronic devices, catalysis, biological materials, and other fields, but their easy oxidation characteristics have become a problem in their practical application. Many antioxidant technologies have been developed. However, these technologies are usually accompanied by changes in physicochemical properties, complicated operations, and high costs. Here, we describe a method for simultaneously achieving controllable morphology synthesis and antioxidative preparation of copper nanomaterials through a single solvothermal reaction in a polar organic solvent environment with formate groups. The stability of one-step copper nanomaterials in different environments is monitored and compared with traditional copper nanomaterials. Notably, the two-dimensional copper nanomaterial Cu NSs-FA prepared by one-step method has a low initial resistance of 48 × 10−3 Ω/sq, and the resistance only rises to 221 × 10−3 Ω/sq after treatment in a harsh alkaline environment for 12 h, which is comparable to that of ordinary Cu NSs (379 ×10−3 Ω/sq). The ratio reflects good environmental stability. This antioxidation strategy, which is suitable for a variety of copper nanomaterials, is simple to operate and has low cost, showing broad prospects in the practical application of copper nanomaterials.

Topology-Directed Self-Locking of Colloidal Suprastructures

The robustness and stability of self-assembled colloidal suprastructures are pivotal and challenging in the field of soft condensed matter and nanotechnology. Herein, we develop a novel approach to “self-locking” the colloidal suprastructures to achieve excellent stability by taking advantage of the topology of polymer brushes on nanoparticles. Compared to linear polymer brushes, looped polymer brushes can significantly improve the structural stability of the suprastructures. A combination of experiments and simulations reveals that the suprastructures achieve their significant stabilities through a “self-locking” mechanism by forming folded entanglement between looped polymer molecules. The stabilized suprastructures can stay intact in various organic solvent environments or under heating and mechanical oscillations. Furthermore, the interparticle spacing of suprastructures can be modulated by controlling polymer conformations in an aqueous solution through varying salt concentrations. This new approach of “self-locking” provides an easy-to-operate strategy to stabilize suprastructures and modulate interparticle distances without adding chemicals, which allows the potentially wide applications of colloidal suprastructures under harsh environments.

Atomic insights into the mechanism of trace water influence on lipase catalysis in organic media

Lipase catalysis plays an important role in bioengineering and food science and is widely used in the organic solvent environment. The addition of trace water to organic media can significantly change lipase activity, and the reason is essential to understand. In this study, by combining experiments and molecular dynamics simulations, we studied solvent-free acidolysis of the tripalmitin (PPP) with different water contents and revealed the mechanism of the water effect on lipase activity from atomic insight. Enzyme activity experimentally exhibited an increasing but subsequently decreasing trend with the rise of water content. Through molecular dynamics (MD) simulations, we found that the reaction activity was affected by three aspects: lipase flexibility, substrate diffusion and substrate spatial distribution. Lipase flexibility, as the structural basis of catalytic activity, increased with water content. At lower water content, the diffusion ability of the substrate around the lipase was dominant. With water content increasing, water molecules on the protein surface gradually shielded hydrogen bonds (HBs) between the oleic acids (OA) and the lipase, which improved the diffusion ability of the substrate near the enzyme surface and thus beneficial to the reaction occurring. At higher water content, the spatial distribution dominated the reaction, where the thicker water layer on the lipase surface acted as a spatial barrier hindering the access of substrate OA to the enzyme and thus harmful to the reaction. Our work helps to provide guidance on controlling enzyme activities in organic solvent systems.

Lanthanum-doped carbon quantum dots (La-CQDs) for detection of Fe3+ in colorimetric test paper and information anti-counterfeiting

Based on the fluorescence quenching principle, a novel lanthanum-doped carbon quantum dots (La-CQDs) fluorescence probe was successfully developed for ion detection of Fe3+. La-CQDs with a fluorescence quantum yield of 29.93% was prepared in ethanol solution using ammonium citrate as the carbon source and lanthanum nitrate as the dopant. The luminescence performance of La-CQDs was enhanced by La doping and maintained over 90% of the maximum fluorescence intensity in different anions, water content and organic solvent environments. In the range of 25–200 μM, the fluorescence intensity of La-CQDs displayed a good linear relationship (Y = 0.00675X+ 1.07679, R2 = 0.9888) with the concentration of Fe3+ and its limit of detection (LOD) was calculated to be 6.78 μM. The method was successfully applied to the detection of Fe3+ in green tea and the measurement error was less than 3%. In addition, La-CQDs was developed for fluorescent colorimetric test paper and information anti-counterfeiting, while the fluorescence quenching effect was observed intuitively on the paper.

Amphiphilic Nanointerface: Inducing the Interfacial Activation for Lipase.

Graphene-based materials are widely used in the field of immobilized enzymes due to their easily tunable interfacial properties. We designed amphiphilic nanobiological interfaces between graphene oxide (GO) and lipase TL (Thermomyces lanuginosus) with tunable reduction degrees through molecular dynamics simulations and a facile chemical modulation, thus revealing the optimal interface for the interfacial activation of lipase TL and addressing the weakness of lipase TL, which exhibits weak catalytic activity due to an inconspicuous active site lid. It was demonstrated that the reduced graphene oxide (rGO) after 4 h of ascorbic acid reduction could boost the relative enzyme activity of lipase TL to reach 208%, which was 48% higher than the pristine GO and 120% higher than the rGO after 48 h of reduction. Moreover, TL-GO-4 h's tolerance against heat, organic solvent, and long-term storage environment was higher than that of free TL. The drawbacks of strong hydrophobic nanomaterials on lipase production were explored in depth with the help of molecular dynamics simulations, which explained the mechanism of enzyme activity enhancement. We demonstrated that nanomaterials with certain hydrophilicity could facilitate the lipase to undergo interfacial activation and improve its stability and protein loading rate, displaying the potential of the extensive application.

Deprotonated tannic acid regulating pyrrole polymerization to enhance nanofiltration performance for molecular separations under both aqueous and organic solvent environments

Nanofiltration with precise separation ability demonstrates the increasing importance in water treatment and high-value substance recycling compared with traditional energy-intensive separation technologies. Nevertheless, nanofiltration membranes still suffer from the permeance-selectivity “trade-off” issue. Herein, we designed the de novo nanofiltration membrane with enhanced separation performance by adopting deprotonated tannic acid (TA) as intermediate layer to tune pyrrole polymerizaiton for forming the polypyrrole selective layer. TA were coated followed by in-situ polymerization of pyrrole and they assembled based on the strong electrostatic and hydrogen bonding interaction. The deprotonation of phenolic hydroxyl groups in TA effectively regulated the polymerization process of pyrrole to obtain the synthesized nanofiltration membrane with the average pore diameter of 0.45 nm. The optimized nanofiltration membrane exhibited a 3.7-fold increase in permeance and almost complete rejection for various dyes with different molecular weights and charges, which breaks the permance-selectivity “trade-off”. In addition, the synthesized membrane possessed the excellent structural stability even in polar organic solvent of tetrahydrofuran. Our new strategy for constructing high-performance nanofiltration membrane via intermediate-layer-tuned formation/polymerization of the selective layer can provide an alternative potential avenue to fabricate next-generation molecular separation membranes towards environmental remediation and resource recovery.

Enzymatic modification of triglycerides in conventional and surfactant-free microemulsions and in olive oil

Modification of the acylglycerol profile by interesterification of triacyglycerols (TAGs) can improve certain properties of food products. TAGs enriched in palmitic acid (PA) at the sn-2 position and in unsaturated fatty acids at the sn-1,3 position of the glycerol backbone are an important source of nutrients and energy for humans. In the present study, commercially available lipases have been used for the enzymatic interesterification of TAGs to form lipids containing PA and oleic acid (OA). Lipases A and B from Candida antarctica (CaL A and CaL B) and Thermomyces lanuginosus lipase (TLL) were tested in different environments from organic solvents to non-conventional systems such as w/o microemulsions (in the absence and presence of surfactants) and olive oil. The effects of reaction temperature, substrate molar ratio, and external energy were investigated. AOT microemulsions offered an excellent microenvironment for the interesterification reaction, while lecithin microemulsion affected TLL specificity. Surfactant-free microemulsions were also tested in terms of optimization of production process, however lower reaction yields were obtained. For the commercial immobilized CaL B, the ratio PA:triolein affected the reaction yield with the 2:1 ratio showing promising results in organic solvent environment. The main purpose of the present study was to elucidate the appropriate conditions for the enzymatic modification of olive oil. Several factors were tested such as substrates’ ratio, enzyme’s concentration, reaction temperature and external energy input. Overall, the ideal conditions for the formulation of the desired TAGs included the use of 50 mM free PA as substrate, 3 mg of immobilized CaL B/mL of olive oil while the reaction temperature was set at 40 °C and the duration was 72 h.

Enantiomeric Separation of Racemic Mixtures Using Chiral-Selective and Organic-Solvent-Resistant Thin-Film Composite Membranes.

Membrane-based chiral separation has emerged as a promising method for the efficient separation of chiral molecules. Ideally, the membranes should be able to achieve good enantioselectivity, while maintaining high stability in harsh solvents. However, engineering membranes for chiral molecular separation in harsh organic solvent environments is still a big challenge. In this study, we fabricated a novel thin-film composite nanofiltration membrane composed of (2-hydroxypropyl)-beta-cyclodextrin (HP-β-CD) as the chiral selector for the enantiomeric separation of racemic 1-phenylethanol chiral compounds in organic solvents. The fabricated membrane achieved 60-80% enantioselectivity of R-phenylethanol over S-phenylethanol in nonpolar n-hexane. It was found that HP-β-CD played a critical role in the enantioselective performance, as the membrane without HP-β-CD showed no chiral selectivity. Molecular docking calculations substantiate the experiments by showing that the average free binding energy of S-phenylethanol with HP-β-CD is stronger than that of R-phenylethanol, indicating that the complex of S-phenylethanol with HP-β-CD has a higher thermodynamic stability and greater interaction. Furthermore, the crosslinked network between HP-β-CD and the polyamide layer conferred the membrane with solvent stability in nonpolar solvents. Moreover, this new membrane exhibited good solvent permeance and a molecular weight cutoff of around 650 g mol-1.

Towards the Application of Supramolecular Self-Associating Amphiphiles as Next-Generation Delivery Vehicles.

Herein, we present a series of supramolecular self-associating amphiphilic (SSA) salts and establish the potential for these molecular constructs to act as next-generation solution-state molecular delivery vehicles. We characterise the self-association of these SSAs, both alone and when co-formulated with a variety of drug(like) competitive guest species. Single crystal X-ray diffraction studies enable the observation of hydrogen-bonded self-association events in the solid state, whilst high resolution mass spectrometry confirms the presence of anionic SSA dimers in the gas-phase. These same anionic SSA dimeric species are also identified within a competitive organic solvent environment (DMSO-d6/0.5% H2O). However, extended self-associated aggregates are observed to form under aqueous conditions (H2O/5.0% EtOH) in both the absence and presence of these competitive guest species. Finally, through the completion of these studies, we present a framework to support others in the characterisation of such systems.

Link between interfacial interaction and membrane fouling during organic solvent ultrafiltration of colloidal foulants

Membrane fouling is inevitable for liquid membrane-filtration processes. While the relationship between surface free energy and membrane fouling is now well-established for aqueous feeds, such a link remained missing for the emerging organic solvent applications. In this study, three organic solvents (namely, methanol, ethyl acetate and acetonitrile) and three colloidal foulants (namely, silicon dioxide (SiO2), titanium dioxide (TiO2) and aluminum (Al)) were investigated using the same polyacrylonitrile (PAN) ultrafiltration membrane at five transmembrane pressures (100–500 kPa). The zeta potentials were measured, and the Gibbs free energy of interfacial interactions for both foulant – membrane and foulant – foulant were quantified via the DLVO and XDLVO models to correlate with the fouling trends. Surprisingly, although the XDLVO-based interaction energy is generally acknowledged to correlate well with membrane fouling trends for aqueous feeds, the results here indicate that qualitative agreement with flux decline, cake resistance and cake compressibility was poor. Zeta potentials also exhibited poor predictive capability. Only the DLVO-based interaction energy values agreed with the flux decline trends, but nonetheless failed for cake compressibility trends. This study underscore the different fouling behaviors between aqueous versus organic solvent environments, particularly in the limited capacity of the XDLVO model and zeta potential values to provide insights on the fouling mechanisms.

Robust natural nanocomposites realizing unprecedented ultrafast precise molecular separations

Synthetic polymer membranes can potentially reduce the large energy and carbon footprints that are typically associated with traditional chemical separation technologies. Unfortunately, current production protocols negate the green benefits of membrane separation. To address this bottleneck, here we report the use of natural materials monosaccharide – glucose and polydopamine and Zr-based metal organic frameworks (MOFs) to fabricate ultrathin nanocomposite membranes via interfacial polymerization reaction. The synergistic effect of these three materials on angstrom-scale molecular transport both in organic solvent and aqueous environment was elucidated using a series of complementary techniques. We demonstrate such nature-inspired nanocomposite membranes enable structural stability even in polar aprotic solvents, and unparalleled ultra-fast, low-pressure, precise separations in both nanofiltration modes, which easily surpass state-of-the-art membranes relying on unsustainable materials. The multi-functionality of saccharide nanocomposites was elegantly harnessed to impact separation applications that contribute towards a better living environment.

Complexes of glucose oxidase with chitosan and dextran possessing enhanced stability

In this study, the different mole ratios of glucose oxidase/chitosan/dextran–aldehyde and glucose oxidase/chitosan/dextran–sulfate complexes were synthesized. The modification of glucose oxidase by non-covalent complexation with dextran and chitosan in different molar ratios was studied in order to increase the enzyme activity. The enzyme/polymer complexes obtained were investigated by UV spectrophotometer and dynamic light scattering. Activity determination of synthesized complexes and free enzyme were performed at a temperature range. The best results were obtained by Cchitosan/Cdextran–aldehyde = 10/1 ratio and Cchitosan/Cdextran–sulfate = 1/5 ratio that were used in thermal stability, shelf life, salt stress, and ethanol effect experiments. The results demonstrated that both complexes were thermally stable at 60 °C and had superior storage stability compared to the free glucose oxidase. Complexes showed higher enzymatic activity than free enzyme in the organic solvent environment using 10% ethanol. The complexes were resistant to salt stress containing 0.1 M NaCl or CaCl2. The particle size distribution results of the triple complex evaluated the complexation of the chitosan, dextran derivative, and glucose oxidase. The average size of the triple complex in diameter was found to be 325.8 ± 9.3 nm. Overall findings suggest that the complexes of glucose oxidase, chitosan, and dextran showed significant enhancement in the enzyme activity.

Transparent conductive elastomers with excellent autonomous self-healing capability in harsh organic solvent environments

A new type of transparent conductive elastomer with excellent autonomous self-healing capability in harsh organic solvent environments is reported.

Supramolecular chemistry assisted construction of ultra-stable solvent-resistant membranes for angstrom-sized molecular separation

Organic solvent nanofiltration (OSN) membrane is an embryonic technology in chemical engineering for simultaneously purifying organic solvents and recycling nano-scale molecules. Although the inherent nano-cavity cyclodextrins (CDs) as powerful molecular hosts in supramolecular science ensure promise for separation technology, the limited synthesis toolbox and material choice impede the CDs deployment in membrane separations, especially for OSN applications. Herein, biocompatible β-cyclodextrin (β-CD) and mussel-inspired polydopamine (pDA) were discovered as the building blocks to simultaneously construct OSN membranes assisted by the host-guest interactions of supramolecular chemistry and hydrogen-bonds via one-step “green” process. Honeycomb microstructures were formed in this process, which adds the molecular transportation pathways. Such biopolymer membranes can remain extraordinarily stable in organic solvent environments, whilst achieving high rejection against angstrom-sized molecule with different charges toward environmental and energy benefits.

Unravelling protein -organic solvent interaction of organic solvent tolerant elastase from Pseudomonas aeruginosa strain K crystal structure

The utilization of organic solvents as reaction media for enzymatic reactions provides numerous industrially attractive advantages. However, an adaptation of enzyme towards organic solvent is unpredictable and not fully understood because of limited information on the organic solvent tolerant enzymes. To understand how the enzyme can adapt to the organic solvent environment, structural and computational approaches were employed. A recombinant elastase from Pseudomonas aeruginosa strain K was an organic solvent tolerant zinc metalloprotease was successfully crystallized and diffracted up to 1.39 Å. Crystal structure of elastase from strain K showed the typical, canonical alpha-beta hydrolase fold consisting of 10-helices (118 residues), 10- β-strands (38 residues) and 142 residues were formed other secondary structure such as loop and coil to whole structure. The elastase from Pseusomonas aeruginosa strain K possess His-140, His-144 and Glu-164 served as a ligand for zinc ion. The conserved catalytic triad was composed of Glu-141, Tyr-155 and His-223. Three-dimensional structure features such as calcium-binding and presence of disulphide-bridge contribute to the stabilizing the elastase structure. Molecular dynamic (MD) simulation of elastase revealed that, amino acid residues located at the surface area and disulphide bridge in Cys-30 to Cys-58 were responsible for enzyme stability in organic solvents.

Symmetrically recombined nanofibers in a high-selectivity membrane for cation separation in high temperature and organic solvent

Symmetrically recombining poly(p-phenylene terephthalamide) nanofibers and 2,5-diaminobenzenesulfonic acid based on amide hydrolysis and amide condensation reaction for ion separation in high temperature and organic solvent environment.