Attractive Electrostatic Interactions Research Articles

Efficient and Stable Mesoporous CsSnI3 Perovskite Solar Cells via Imidazolium‐Based Ionic Liquid Additive

Inorganic tin halide perovskite compound with its eco‐friendly property has attracted tremendous attention of researchers in the field of lead‐free perovskite solar cells. However, the trap‐assisted nonradiative recombination caused by deep‐level defects originating from surface undercoordinated Sn2+ cations significantly deteriorates the CsSnI3 device's performance. Herein, adding low concentrations of an ionic liquid 1‐ethyl‐3‐methylimidazolium acetate (EMIMAc) shows promise in controlling deep‐level defects in CsSnI3 perovskites. Both experimental observation and theoretical simulation reveal that EMIMAc can have strong electrostatic attraction and coordination interaction with the surface undercoordinated Sn2+ through the lone electron pairs of carboxyl functional groups and the donated π electrons from electron‐rich imidazole moieties, leading to a reduced deep‐level defect density and a restrained nonradiative recombination. Consequently, the processed CsSnI3 perovskite solar cells based on a printable fluorine‐doped tin oxide/compact‐TiO2/mesoporous‐TiO2/Al2O3/NiO/carbon framework achieve a power conversion efficiency as high as 8.54%, which is the champion efficiency among all the reported CsSnI3 mesoporous perovskite solar cells up to now. In addition, the unencapsulated devices have shown an impressive long‐term stability with only ≈6% efficiency degradation after over 2000 h aging under nitrogen atmosphere.

Effective flotation separation of malachite from quartz with a selective collector: Collection ability, separation performance and adsorption mechanism

In this study, we focused on the collecting features and sorption mechanism of stearyl diethanolamine (SDA) used as a novel collector towards the surfaces of quartz and malachite, to recover efficiently malachite from quartz. The flotation results demonstrated that DSA displayed an excellent collection performance for quartz but not for malachite. At pH 6.50, with 8 mg/L SDA, effectively recovering malachite from quartz was achieved by reverse flotation, in which 92.71 % of malachite was recovered and 91.91 % of quartz was removed, coupled with a high separation efficiency (SE) of 84.63 % and a high concentrate Cu grade of 52.52 %. Surface wettability studies suggested that SDA significantly improved the surface hydrophobicity of quartz but not malachite, as evidenced by the significantly increased contact angle of quartz (from 24.16° to 97.16°), which resulted in the excellent floatability of quartz. Adsorption amount detection results revealed that the adsorption density of SDA on quartz was much higher than that on malachite, namely 0.065 mg/g for quartz and 0.0049 mg/g for malachite, which enhanced the hydrophobicity of quartz. Zeta potential characterization and FTIR detection evidenced that apart from the strong electrostatic attraction interaction of the positively charged SDA+ with the quartz surface with negative charge, the strong adsorption of SDA onto quartz also depended much on the hydrogen bonding interaction between quartz’s Si-OH groups and SDA’s hydroxyl groups. Therefore, SDA can be regarded as a highly selective quartz collector to realize the effective recovery of malachite.

Effects of Charged Polyelectrolytes on Amyloid Fibril Formation of a Tau Fragment.

The microtubule-associated protein tau is involved in more than 20 different neurological disorders characterized by aberrant intracellular aggregation of tau in the brain. Here, we investigated the aggregation of a novel 20-residue model peptide, tau298-317, which is derived from the key microtubule binding domain of the full sequence tau. Our results show that tau298-317 highly mimics the physical and aggregation properties of tau. Under normal physiological conditions, the peptide maintains a disordered random coil without aggregation. The presence of polyanionic heparin (Hep) significantly promotes the aggregation of this peptide to form amyloid fibrils. The Hep-induced aggregation is sensitive to the ionic strength of the solution and the introduction of the negatively charged phosphate group on a serine (Ser305) residue in the sequence, suggesting an important role of electrostatic interactions in the mechanism of Hep-mediated aggregation. In addition, two positively charged polysaccharides, chitosan (CHT) and its quaternary derivative N-trimethyl chitosan (TMC), were found to effectively inhibit Hep-induced aggregation of tau298-317 in a concentration-dependent manner. Attractive electrostatic interactions between the positively charged moieties in CHT/TMC and the negatively charged residues of Hep play a critical role in inhibiting Hep-peptide interactions and suppressing peptide aggregation. Our results suggest that positively charged polyelectrolytes with optimized charged groups and charge distribution patterns can serve as effective molecular candidates to block tau-Hep interactions and prevent aggregation of tau induced by Hep and other polyanions.

Dibenzo-18-crown-6-functionalized organic nanotubes for the synergistic adsorption of dyes and phenols from aqueous solutions

Toxic organic pollutants including dyes and phenols in effluent have not be treated efficiently by traditional wastewater methods. Herein, a novel nanotubular material was prepared successfully via supramolecular self-assembly of N,N′,N″-(3-methylpyridine) benzenetriamide (TMPTA) and further modified with dibenzo-18-crown-6 groups to obtain crown-ether-functionalized nanotubes (TMPTA-CE). The crown-ether-based TMPTA-CE shows a unique cavity structure, positively charged pyridinium groups and especially favorite crown ether-cation host-guest interactions. The crown-ether-based material as an adsorbent exhibits superior synergistic adsorption ability towards anionic dyes and phenols. The maximum adsorption capacities of MO, BPA and PNP for TMPTA-CE reached 802.23, 105.69 and 98.03 mg/g, respectively, with the removal efficiency of >99 %. The existence of K+ ions can improve the adsorption capacities of BPA and PNP by about 28.14 % and 42.82 %, respectively. Notably, no significant change in adsorption efficiency was observed after 5 repeated adsorption-desorption cycles. Mechanism studies shows that synergistic effect of π-π interaction, electrostatic attraction and hydrogen-bond interaction played a significant role for the adsorption of anionic dyes and phenols. The results shows that the as-synthesized TMPTA-CE adsorbent with a simple, efficient and low-cost synthetic process has potential application in practical wastewater treatment.

(Invited) Structure and Reactivity of Ruthenium-Substituted Prussian-Blue-Type Oxo-Cyanide Bridged Networks: Prospects for Electrocatalysis and Analytical Determinations

Electrochemical deposition of crosslinked oxo-cyanoruthenate, Ru-O/CN-O, from a mixture of RuCl3 and K4Ru(CN)6 is known to yield a film on glassy carbon that promotes oxidations by a combination of the electron and oxygen transfers. The initial suggestion that the film could be a simple ruthenium analogue of Prussian Blue, in which the Ru ions reach higher then III oxidation state, was later clarified using Auger electron spectroscopy and X-ray photoelectron spectroscopy. It was postulated that the electrochemical deposition process yielded the -Ru-O-Ru- network with cyano-groups crosslinks, Ru-O/CN-O, where the ruthenium could exist in mixed oxidation states. Such mixed-valent conditions, facilitated the overall charge distribution and conductivity of the catalytic material. In addition, contrary to iron ions in Prussian Blue, ruthenium can be readily oxidized to higher oxidation states to form catalytically active ruthenium(IV,III) oxo species that include Ru3O2 6+ or Ru2O5 + groups immobilized within the cyanide-bridged network. Furthermore, at pH = 2, the hexacyanoruthenate anions tended to transformation to dinuclear anionic species, [(CN)5-RuIICN-RuIII-(CN)5]6 −. Strong electrostatic attractive interactions as well as the polynuclear character of deposits led to the overall stabilization of the system. Films of Ru-O/CN-O were demonstratedto have low ohmic resistances as a result of effective charge transport involving hydrogen and/or potassium ions.Numerous applications of Ru-O/CN-O, which have been reported or recently demonstrated, will be considered during presentation. The oxidation of alcohols, inorganic and organic sulfur compounds, glucose, hydrazine, aldehydes, nitrosamines, insulin, and tetracycline are representative examples. From the electrochemical analysis point of view, as it is typical with electrode reactions involving mediated electron transfers, the signal-to-background ratios with amperometry under potentiostatic conditions are preferred over potentiodynamic methodology for analytical applications. By the former approach, detection limits of nmol dm− 3 in an injection are achieved. For example, a linear calibration curve has been obtained over the range 8–200 ng insulin in a 7.5 µL injection into a flow system with measurement of current under potentiostatic conditions . Analogous to mixed metal oxides as modifiers, the efficacy of this catalyst should be related to the combination of fast electron displacements and specific oxygen transfers. The system’s resistance to interfacial passivation should be mentioned here. Finally, the carefully designed multicomponent systems provide a route to improving electrocatalytic efficiency over that at single-component materials because of electronic, geometric or stability factors. Combination of Ru-O/CN-O with silica sol-gels as solid electrolytes expands the scope of electrochemical applications and adapts electrocatalysis to chemical analysis of complex samples.

Colourful organic afterglow materials with super-wide color gamut and scaled processability from cellulose

Multi-colour afterglow materials have attracted widespread attention recently, because they not only can eliminate the interference of scattered light and background fluorescence, but also store the richer information. In this work, the phosphorescence emission of cellulose-based nitrogen-doped carbon dots (CDs) was transferred to the rhodamine derivatives via an efficient radiative energy transfer process, because of the strong electrostatic attraction interactions between the positive charged CDs and the negative charged rhodamine derivatives. As a result, multi-color afterglow luminescence with tunable emission and wide color gamut was realized from blue-green to green, yellow, orange and red. With the contribution of the excellent processability of polymer materials, multi-color afterglow films, coatings, fibers and patterns were readily obtained, indicating a practical application in advanced anti-counterfeiting and multiple-mode information encryption. Such a facile, universal and efficient strategy to construct multi-colour afterglow materials inspires us to understand the luminescence process and design novel afterglow materials.

A novel carbon adsorbent derived from iron-poisoned waste resin for phosphate removal from wastewater: Performance and mechanism

In this study, a new Fe-rich carbon composite derived from iron-poisoned waste resin (WRC) was successfully prepared via pyrolysis-activation to remove phosphate from wastewater. The physicochemical properties of WRC were characterized using multiple characterization tools. The results showed that the WRC had a large specific surface area and was rich in metal loading for adsorption. Batch and fixed-bed experiments investigated the adsorption performance of WRC. The maximum adsorption capacity calculated from the Langmuir model was 17.43 mg/g at 298 K. Kinetics experiments showed that the adsorption of phosphate by WRC accorded with pseudo-second-order kinetic model. The WRC could maintain excellent adsorption performance in a wide pH range of 2–12, suitable for various wastewater conditions. Meanwhile, the WRC had well anti-interference of common anions and humic acids on phosphate adsorption and WRC reuse performance. The mechanisms of phosphate adsorption by WRC were confirmed to be electrostatic attraction, ligand exchange and Lewis acid-base interaction. Fixed bed experiments were conducted for dynamic treatment of synthetic wastewater and actual wastewater, and the results indicated that WRC had potential application prospect. This study provides an economically feasible method for the phosphate removal from wastewater and achieves the reuse of waste resin.

Biomolecular Complexation on the "Wrong Side": A Case Study of the Influence of Salts and Sugars on the Interactions between Bovine Serum Albumin and Sodium Polystyrene Sulfonate.

In the protein purification, drug delivery, food industry, and biotechnological applications involving protein–polyelectrolyte complexation, proper selection of co-solutes and solution conditions plays a crucial role. The onset of (bio)macromolecular complexation occurs even on the so-called “wrong side” of the protein isoionic point where both the protein and the polyelectrolyte are net like-charged. To gain mechanistic insights into the modulatory role of salts (NaCl, NaBr, and NaI) and sugars (sucrose and sucralose) in protein–polyelectrolyte complexation under such conditions, interaction between bovine serum albumin (BSA) and sodium polystyrene sulfonate (NaPSS) at pH = 8.0 was studied by a combination of isothermal titration calorimetry, fluorescence spectroscopy, circular dichroism, and thermodynamic modeling. The BSA–NaPSS complexation proceeds by two binding processes (first, formation of intrapolymer complexes and then formation of interpolymer complexes), both driven by favorable electrostatic interactions between the negatively charged sulfonic groups (−SO3–) of NaPSS and positively charged patches on the BSA surface. Two such positive patches were identified, each responsible for one of the two binding processes. The presence of salts screened both short-range attractive and long-range repulsive electrostatic interactions between both macromolecules, resulting in a nonmonotonic dependence of the binding affinity on the total ionic strength for both binding processes. In addition, distinct anion-specific effects were observed (NaCl < NaBr < NaI). The effect of sugars was less pronounced: sucrose had no effect on the complexation, but its chlorinated analogue, sucralose, promoted it slightly due to the screening of long-range repulsive electrostatic interactions between BSA and NaPSS. Although short-range non-electrostatic interactions are frequently mentioned in the literature in relation to BSA or NaPSS, we found that the main driving force of complexation on the “wrong side” are electrostatic interactions.

PH sensitive double-layered emulsions stabilized by bacterial cellulose nanofibers/soy protein isolate/chitosan complex enhanced the bioaccessibility of curcumin: In vitro study

In this work, double-layered emulsions stabilized by bacterial cellulose nanofibers/soy protein isolate/chitosan complex were prepared using layer-by-layer self-assembly technology and used for the delivery of curcumin, and the physical and delivery properties of the prepared double-layered emulsions were investigated. The zeta-(ζ) potential of colloidal particles confirmed that the chitosan was adsorbed on surface of the single-layered emulsion droplets by attractive electrostatic interactions. Meanwhile, the physical properties showed that the double-layered emulsions displayed high pH-sensitivity and showed relatively higher stability under acid environment. Furthermore, the in vitro digestion result showed that the curcumin loaded by double-layered emulsions were more stable during simulated gastric digestion as compared with that loaded by single-layered emulsions. Especially, the bioaccessibility of curcumin delivered by the double-layered emulsions (77.4 ± 3.25%) was significantly higher than that of curcumin delivered by single-layered emulsions (32.8 ± 2.56%). Therefore, it can be concluded that the prepared double-layered emulsions showed a great potential application in the delivery of fat-soluble bioactive compounds.

A historical biophysical dogma vs. an understanding of the structure and function of voltage-gated tetrameric ion channels. A review

The outstanding work of several eminent biophysicists has allowed the functional features of voltage-gated tetrameric ion channels to be disclosed using ingenious and sophisticated electrophysiological techniques. However, the kinetics and mechanism underlying these functions have been heavily conditioned by an arbitrary interpretation of the groundbreaking results obtained by Hodgkin and Huxley (HH) in their investigation of sodium and potassium currents using the voltage clamp technique. Thus, the heavy parametrization of their results was considered to indicate that any proposed sequence of closed states terminates with a single open state. This ‘dogma’ of HH parametrization has influenced the formulation of countless mechanistic models, mainly stochastic, requiring a high number of free parameters and of often unspecified conformational states. This note aims to point out the advantages of a deterministic kinetic model that simulates the main features of tetrameric ion channels using only two free parameters by assuming their stepwise opening accompanied by a progressively increasing cation flow. This model exploits the electrostatic attractive interactions stemming from the charge distribution shared by all tetrameric ion channels, providing a close connection between their structure and function. Quite significantly, a stepwise opening of all ligand-gated tetrameric ion channels, such as glutamate receptors (GluRs), with concomitant ion flow, is nowadays generally accepted, not having been influenced by this dogma. This provides a unified picture of both voltage-gated and ligand-gated tetrameric ion channels.

Removal of perfluorooctanoic acid via polyethyleneimine modified graphene oxide: Effects of water matrices and understanding mechanisms

This research aimed to evaluate the adsorption behaviors and mechanisms of perfluorooctanoic acid (PFOA) onto polyethyleneimine modified graphene oxide (GO-PEI) from aqueous solutions. The adsorption capacity was significantly improved by doping polyethyleneimine (PEI) onto graphene oxide (GO). The Brunauer-Emmett-Teller (BET) isotherm model was considered as the best isotherm model in describing the PFOA adsorption onto GO-PEI3 (wPEI/wGO = 3). GO-PEI3 exhibited high adsorption capacity (qe = 368.2 mg/g, calculated from BET isotherm model) and excellent stability. The maximum monolayer amount of PFOA adsorption onto GO-PEI3 (qm = 231.2 mg/g) was successfully evaluated. The calculated saturated concentration (Cs = 169.9 mg/L) of PFOA on GO-PEI3 closely agrees with its critical micelle concentration (CMC = 157.0 mg/L), suggesting the formation of multilayer hemi-micelles or micelles PFOA structures on the surface of GO-PEI3. PFOA adsorption onto GO-PEI3 was inhibited by several factors including: the presence of humic acid (HA) by competing with the adsorption sites, background salts through the double-layer compression effect, and the competition from soluble ions for the amine or amide functional groups on GO-PEI3. Finally, both the FT-IR and XPS results confirmed that the adsorption of PFOA onto GO-PEI3 was through electrostatic attraction and hydrophobic interaction (physical adsorption), but not chemical adsorption. This work provides fundamental knowledge both in understanding the adsorption behavior through the BET isotherm model and in developing a stable adsorbent for PFOA adsorption. In addition, the findings highlight the potential of PFOA remediation from wastewater systems using GO-PEI in engineering applications.

Reconstruction and Removal Mechanisms of Gel-like Membrane Fouling for Seawater Desalination: Experiments and Molecular Dynamics Simulations.

Anti-gel fouling is a key problem faced by membrane desalination, especially for applications in organic acid-rich seawater. In this paper, a chemical crosslinking-based method was used to reconstruct and characterize the gel pollutants produced under the actual operating conditions of seawater desalination. In addition to the calcium alginate/calcium humate three-dimensional network skeleton, salt ions (K+, Na+, Mg2+, Cl−) in solution were also considered to ensure that the reconstructed gel was similar to pollutant gels on membranes under practical operating conditions. Characterizations showed that the reconstructed gel has high thermal insulation and stability, thus adjusting the temperature has no removal effect. Two detergents (sodium citrate and sodium hydroxide) were investigated, and their gel-removal mechanism was elucidated by molecular dynamics simulation. Numerical analysis showed that the electrostatic attraction interaction had a significant role in the gel cleaning process. Owing to the attraction of the lower electrostatic potential region in the cleaning agent, the ion exchange between Na+ in the cleaning agent and Ca2+ in the gel led to the breaking of the Ca2+-induced intermolecular bridge in the complex. As the adhesion of fouling gels decreased, the gel water solubility was increased, resulting in a decrease in weight and strength of the gel. Therefore, the integrity of the gel fouling layer was weakened and can be effectively removed. This study provides a theoretical basis for the removal of gel-like membrane fouling during actual seawater desalination.

Ultra-High Modulus Hydrogels Mimicking Cartilage of the Human Body.

The human body is comprised of numerous types of cartilage with a range of high moduli, despite their high hydration. Owing to the limitations of cartilage tissue healing and biological grafting procedures, synthetic replacements have emerged but are limited by poorly matched moduli. While conventional hydrogels can achieve similar hydration to cartilage tissues, their moduli are substantially inferior. Herein, triple network (TN) hydrogels are prepared to synergistically leverage intra-network electrostatic repulsive and hydrophobic interactions, as well as inter-network electrostatic attractive interactions. They are comprised of an anionic 1st network, a neutral 2nd network (capable of hydrophobic associations), and a cationic 3rd network. Collectively, these interactions act synergistically as effective, yet dynamic crosslinks. By tuning the concentration of the cationic 3rd network, these TN hydrogels achieve high moduli of ≈1.5 to ≈3.5MPa without diminishing cartilage-like water contents (≈80%), strengths, or toughness values. This unprecedented combination of properties poises these TN hydrogels as cartilage substitutes in applications spanning articulating joints, intervertebral discs (IVDs), trachea, and temporomandibular joint disc (TMJ).

Structural and Dynamical Studies of a Lipid-Nanoclay Composite Layer at the Air-Water Interface.

We modulate the adsorption affinities of nanoclay particles for the air-water interface by changing the cationic surface charge composition of the lipid monolayer and thereby tune the attractive electrostatic interaction between the positively charged lipid layer and the zwitterionic nanoclay particles in the water subphase. Our findings emphasize the significance of electrostatic interaction between lipids and the nanoclay, as well as its impact on the structural and viscoelastic features of the composite layer. We use surface pressure (Π)-mean molecular area (A) isotherms, atomic force microscope (AFM), Brewster angle microscopy (BAM), and energy dispersive X-ray spectrsocopy (EDXS) measurements to analyze the structure phases of lipid and lipid-nanoclay composite interfacial layer. The Π-A isotherm curve shows that the lipid-nanoclay composite layer has a larger lift-off area than the neat lipid layer, indicating that nanoparticles adsorb at the lipid layer via electrostatic interaction between lipid and nanoclay molecules. The surface density of the adsorbed nanoclay particles increases with an increase in the composition of the cationic lipid molecules. The stress relaxation response of the composite layer, measured using step compression measurements, exhibits exponential decay and ubiquitous dependence on the cationic dimyristoy-trimethylammonium propane (DMTAP) composition in the lipid layer with crossover to faster relaxation dynamics at DMTAP > 0.75. The power-law study of the frequency-dependent dynamic viscoelastic responses of the interfacial layer, measured using the barrier oscillation method, reveals a transition from glass-like response from neat lipid layer to gel-like dynamic response for the lipid-nanoclay composite layer. A solid-like behavior is evident for all the interface layers with dilation elastic modulus (E') > dilational viscous modulus (E″); however, the dynamic response of the neat layer is largely frequency-independent, whereas lipid-nanoclay composite layers with DMTAP > 0.75 reveal a frequency-dependent dynamic responses. The frequency-dependent power-law exponent of E', E″ increases on increasing the fractional composition of cationic DMTAP from 0.1 to 1.0, which forms a saturated interface of laponite particles and behaves as a viscoelastic gel in 2D.

In-situ synthesis of phosphorus-doped graphene paper with adenosine triphosphate and its application for intelligent fire warning

Design of intelligent sensors for detecting early fire warning before combustion is a challenging for the fire safety. Herein, a nacre-biomimetic paper based on graphene oxide (GO) and adenosine triphosphate (ATP) was fabricated via a low-temperature evaporation assembly approach. Then the fire-alarm sensor was designed according to the high temperature thermal reduction properties of GO. The GO-ATP paper exhibited a well-organized ‘‘brick and mortar” structure due to the presence of hydrogen bonds and electrostatic attraction interaction between GO and ATP molecules. The paper containing 50 wt% of ATP presented a rapid flame detection response (1.36 s) and a long continuous alarm time (1300 s) due to in-situ phosphorus doping and the honeycomb-like char forming during fire exposure. Moreover, the GO-ATP-50 also exhibited flexibility, flame retardant performance, heat insulation ability and char-forming properties. This work provides a bright application prospect for fire safety and prevention of combustible materials.

Thermo-Responsive Polyion Complex of Polysulfobetaine and a Cationic Surfactant in Water

Poly(4-((3-methacrylamidopropyl)dimethylammonium)butane-1-sulfonate) (PSBP) was prepared via controlled radical polymerization. PSBP showed upper critical solution temperature (UCST) behavior in aqueous solutions, which could be controlled by adjusting the polymer and NaCl concentrations. Owing to its pendant sulfonate anions, PSBP exhibited a negative zeta potential of −7.99 mV and formed a water-soluble ion complex with the cationic surfactant cetyltrimethylammonium bromide (CTAB) via attractive electrostatic interaction. A neutral PSBP/CTAB complex was formed under equimolar concentrations of the pendant sulfonate group in PSBP and the quaternary ammonium group in CTAB. Transmittance electron microscopic images revealed the spherical shape of the complex. The stoichiometrically neutral-charge PSBP/CTAB complex exhibited UCST behavior in aqueous solutions. Similar to PSBP, the phase transition temperature of the PSBP/CTAB complex could be tuned by modifying the polymer and NaCl concentrations. In 0.1 M aqueous solution, the PSBP/CTAB complex showed UCST behavior at a low complex concentration of 0.084 g/L, whereas PSBP did not exhibit UCST behavior at concentrations below 1.0 g/L. This observation suggests that the interaction between PSBP and CTAB in the complex was stronger than the interpolymer interaction of PSBP.

PDA-Based Drug Delivery Nanosystems: A Potential Approach for Glioma Treatment.

Glioma is characterized by high mortality and low postoperative survival. Despite the availability of various therapeutic approaches and molecular typing, the treatment failure rate and the recurrence rate of glioma remain high. Given the limitations of existing therapeutic tools, nanotechnology has emerged as an alternative treatment option. Nanoparticles, such as polydopamine (PDA)-based nanoparticles, are embodied with reliable biodegradability, efficient drug loading rate, relatively low toxicity, considerable biocompatibility, excellent adhesion properties, precisely targeted delivery, and strong photothermal conversion properties. Therefore, they can further enhance the therapeutic effects in patients with glioma. Moreover, polydopamine contains pyrocatechol, amino and carboxyl groups, active double bonds, catechol, and other reactive groups that can react with biofunctional molecules containing amino, aldehyde, or sulfhydryl groups (main including, self-polymerization, non-covalent self-assembly, π-π stacking, electrostatic attraction interaction, chelation, coating and covalent co-assembly), which form a reversible dynamic covalent Schiff base bond that is extremely sensitive to pH values. Meanwhile, PDA has excellent adhesion capability that can be further functionally modified. Consequently, the aim of this review is to summarize the application of PDA-based NPs in glioma and to acquire insight into the therapeutic effect of the drug-loaded PDA-based nanocarriers (PDA NPs). A wealthy understanding and argument of these sides is anticipated to afford a better approach to develop more reasonable and valid PDA-based cancer nano-drug delivery systems. Finally, we discuss the expectation for the prospective application of PDA in this sphere and some individual viewpoints.

Luminescent Gold Nanoclusters Interacting with Synthetic and Biological Vesicles.

According to their high electron density and ultrasmall size, gold nanoclusters (AuNCs) have unique luminescence and photoelectrochemical properties that make them very attractive for various biomedical fields. These applications require a clear understanding of their interaction with biological membranes. Here we demonstrate the ability of the AuNCs as markers for lipidic bilayer structures such as synthetic liposomes and biological extracellular vesicles (EVs). The AuNCs can selectively interact with liposomes or EVs through an attractive electrostatic interaction as demonstrated by zetametry and fluorescence microscopy. According to the ratio of nanoclusters to vesicles, the lipidic membranes can be fluorescently labeled without altering their thickness until charge reversion, the AuNCs being located at the level of the phosphate headgroups. In presence of an excess of AuNCs, the vesicles tend to adhere and aggregate. The strong adsorption of AuNCs results in the formation of a lamellar phase as demonstrated by cryo-transmission electron microscopy and small-angle X-ray scattering techniques.

Structural Characteristics of Micro-nano Particle Size Biochar and Its Adsorption Mechanism for Cd2

The aim of this study was to investigate the structural characteristics of biochar with different micro/nano particle sizes and its effect on the adsorption performance of Cd2+. Corn stalk biochar with different particle sizes (180-250 μm, 50-75 μm, and ≤ 20 μm, denoted as BC-1, BC-2, and BC-3, respectively) were prepared using the sieving and ball milling method. The structural properties of different particle sizes of biochar were analyzed via elemental analysis, laser particle size analysis, SEM, BET, FTIR, and XPS. Additionally, the adsorption mechanisms of Cd2+ by three particle sizes of biochar under initial Cd2+ concentrations, adsorption times, and pH conditions were comparatively studied using static adsorption experiments. The results showed that with the decrease in particle size, the pH and zeta potential of biochar were reduced; the aromaticity and polarity decreased; the specific surface area and pore volume increased; and the intensity of the characteristic peaks containing OH, C[FY=,1]C/C[FY=,1]O, and C-O groups increased. The adsorption kinetics of Cd2+ with different particle diameters of biochar were in accordance with the pseudo-secondary kinetic model, with chemisorption dominating. The equilibrium times were in the decreasing order of BC-1 (540 min)>BC-2 (360 min)>BC-3 (80 min). The Langmuir model could better fit the adsorption isotherm process of Cd2+ on biochar of different particle sizes (R2>0.97), and the maximum adsorption capacity of Cd2+ increased with the decrease in particle size, which was expressed as BC-3 (74.43 mg·g-1)>BC-2 (45.71 mg·g-1)>BC-1 (44.59 mg·g-1). The main mechanisms of Cd2+adsorption by biochar were electrostatic attraction, surface complexation, and cation-π interaction.

Dynamics of Human Serum Transferrin in Varying Physicochemical Conditions Explored by Using Molecular Dynamics Simulations.

Conformational stability of human serum transferrin (Tf) at varying pH values and salt and excipient concentrations were investigated using molecular dynamics (MD) simulations, and the results are compared with previously published small-angle X-ray scattering (SAXS) experiments. SAXS study showed that at pH 5, Tf is predominantly present in a partially open (PO) form, and the factions of PO differ based on the physicochemical condition and drift toward the closed form (HO) as the pH increases. Tf is a bilobal glycoprotein that is composed of homologous halves termed the N- and C-lobes. The current study shows that the protonation of Y188 and K206 at pH 5 is the primary conformational drive into PO, which shifts toward the closed (HO) conformer as the pH increases. Furthermore, at pH 6.5, PO is unfavorable due to negative charge-charge repulsion at the N/C-lobe interface linker region causing increased hinge distance when compared to HO, which has favorable attractive electrostatic interactions in this region. Subsequently, the effect of salt concentration was studied at 70 and 140 mM NaCl. At 70 mM NaCl and pH 5, chloride ions bind strongly in the N-lobe iron-binding site, whereas these interactions are weak at pH 6.5. With increasing salt concentration at pH 5, the regions surrounding the N-lobe iron-binding site are saturated, and as a consequence, sodium and chloride ions accumulate into the bulk. Additionally, protein-excipient interactions were investigated. At pH 5, the excipients interact in similar loop regions, E89-T93, and D416-D420, located in the N- and C-lobes of the HO conformer, respectively. It is anticipated that interactions of additives in these two loop regions cause conformational changes that lead to iron-coordinating residues in the N-lobe to drift away from iron and thus drive HO to PO conversion. Furthermore, at pH 6.5 and 140 mM histidine, these interactions are negligible leading to the stabilization of HO.