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1.
Food Chem ; 367: 130733, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34375890

RESUMO

We used computational molecular dynamics (MD) to assess molecular conformations of apo- and holo-forms (respectively without and with Ca2+) of bovine α-lactalbumin (α-La) at different temperatures, and to correlate them with the protein's foaming properties. At 4 °C and 25 °C no major protein conformation changes occurred. At 75 °C, lots of changes were evidenced: the Ca2+ depletion triggered the complete loss of h2b, h3c helices and S1, S2 and S3 ß-sheets, and partial losses of H1, H2 and H3 α-helices. The absence of Ca2+ in apo-α-La and its leaving from holo-α-La triggered electrostatic repulsion among Asp82, Asp84 and Asp87, leading to the formation of a hydrophobic cluster involving Phe9, Phe31, Ile1, Va42, Ile55, Phe80 and Leu81. These conformational changes were related to an interfacial tension decrease and to a foaming capacity increase, for both apo-α-La and holo-α-La. This study exemplifies how powerful MD is as a tool to provide a better understanding of the molecular origins of food proteins' techno-functionalities.


Assuntos
Lactalbumina , Simulação de Dinâmica Molecular , Animais , Cátions , Bovinos , Estrutura Secundária de Proteína , Temperatura
2.
Spectrochim Acta A Mol Biomol Spectrosc ; 264: 120242, 2022 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-34358783

RESUMO

In this work, the structures, quantum chemical descriptors, morphologic characterization of the azo-methoxy-calix[4]arene were investigated. The analyses and interpretation of the theoretical and the experimental IR spectroscopy results for the corresponding compounds was performed. The complexation of the azo-methoxy-calix[4]arene with Zn2+,Hg2+ , Cu2+ , Co2+, Ni2+ , Pb2+ and Cd2+metal cations has been calculated by the dispersion corrected density functional theory (DFT-D3). The values of the interaction energies show that the specific molecule is more selective to the Cu2+ cation. The study of the reactivity parameters confirms that the azo-methoxy-calix[4]arene molecule is more reactive and sensitive to the Cu2+ cation than that Co2+ and Cd2+. In addition, the investigation of the electrophilic and nucleophilic sites has been studied by the molecular electrostatic potential (MEP) analysis. The Hirshfeld surface (HS) analysis of the azo-methoxy-calix[4]arene-Cu2+ interaction have been used to understand the Cu⋯hydrogen-bond donors formed between the cation and the specific compound. The Quantum Theory of Atoms in Molecules (QTAIM) via Non covalent Interaction (NCI) analysis was carried out to demonstrate the nature, the type and the strength of the interaction formed between the Cu2+ cation and the two symmetrical ligands and the cavity. Finally, the chemical sensor properties based on the Si/SiO2/Si3N4/Azo-methoxy-calix[4]arene for detection of Cu2+ cation were studied. Sensing performances are determined with a linear range from 10-5.2 to 10-2.2 M. The Si/SiO2/Si3N4/azo-methoxy-calix[4]arene structure is a promoter to have a good performance sensor.


Assuntos
Calixarenos , Dióxido de Silício , Cátions , Fenóis , Teoria Quântica
3.
Talanta ; 237: 122986, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34736705

RESUMO

A highly sensitive cationic polyfluorinated azobenzene/reduced graphene oxide (C3F7-azo+/RGO) nanocomposite electrochemical sensor for simultaneous detection of dopamine (DA), ascorbic acid (AA) and uric acid (UA) was successfully synthesized using a facile exfoliation/restacking method. The nanocomposite is self-assembled from oppositely charged graphene oxide nanosheets (GO) and polyfluorinated azobenzene cations (C3F7-azo+), and then obtained by electrochemical reduction. The structure and electrochemical properties were characterized by X-ray diffraction (XRD), energy dispersive spectrometer analysis (EDS), transmission electron microscope (TEM) and scanning electron microscope (SEM). The electrochemical property of C3F7-azo+/RGO was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). It can be clearly seen from experimental results that C3F7-azo+/RGO-modified electrode (C3F7-azo+/RGO/GCE) can detect DA, AA and UA simultaneously, and has good stability and anti-interference performance. The detection limits are 65 nM, 8 nM and 11 nM for DA, AA and UA in the ranges 57.28-134.28 µM, 0.04-6.01 µM, 9.23-23.45 µM, respectively.


Assuntos
Grafite , Ácido Úrico , Ácido Ascórbico , Compostos Azo , Cátions , Dopamina , Técnicas Eletroquímicas , Eletrodos
4.
J Colloid Interface Sci ; 606(Pt 1): 10-21, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34384962

RESUMO

HYPOTHESIS: Understanding the effect of cations on membrane fouling is crucial for the widespread application of the membrane technology. However, contradictory results have been reported based on different studies. Moreover, although the effect of the ionic strength has been studied extensively, limited information is available on the effect of the ion type on membrane fouling. EXPERIMENTS: The physicochemical properties of the membrane and anionic polyacrylamide (APAM) were evaluated to calculate the APAM-membrane and APAM-APAM interfacial interaction energies under different conditions. Moreover, a series of microfiltration (MF) experiments was conducted to investigate the effects of the ionic conditions on the flux decline, pore blockage and cake layer resistances, and the flux recovery rate of APAM during the MF process. FINDINGS: As the ionic strength increased, the rate of decrease in the normalized flux increased, the total and cake layer resistances increased significantly, the pore blockage resistance was affected slightly, and the recovery rates of the water flux after physical and chemical cleaning decreased gradually, which could be clearly explained using the Derjaguin-Landau-Verwey-Overbeek theory. Furthermore, compared with Na+, Ca2+ could effectively mitigate the membrane fouling at an identical ionic strength, which is attributed to the hydration forces of APAM-membrane and APAM-APAM.


Assuntos
Resinas Acrílicas , Membranas Artificiais , Ânions , Cátions
5.
J Colloid Interface Sci ; 607(Pt 1): 134-144, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34500414

RESUMO

HYPOTHESIS: The synthesis and characterization of aminated nanocrystalline cellulose (ANCC), a new member of the hairy nanocellulose family, is reported. Hairy nanocelluloses consist of a crystalline rod-like body with amorphous cellulose chains ("hairs") at both ends, on which various functional groups can be accommodated. In ANCC these groups are reactive primary amine groups, which are useful for bioconjugation- and Schiff base-centered modifications. We hypothesize that a two-step oxidation-reductive amination of cellulose fibers followed by hydrothermal treatment will result in the formation of rod-like hairy ANCC. EXPERIMENTS: ANCC was prepared by converting the aldehyde groups in cellulose, introduced by a periodate oxidation, to primary amines using ammonia and sodium borohydride, followed by a hot water treatment, during which diamine modified cellulose fibers were converted to ANCC. ANCC was characterized by AFM, TEM, DLS, ELS, FTIR, NMR, XPS and conductometric titration. Antibacterial activity of ANCC was assessed by the viable cell counting method. FINDINGS: ANCC, with an amine content of 5.5 mmol g-1 is a bare nanocolloid (i.e. non-coated, without adsorbed polyelectrolytes or surfactants) which, as far as we know, has a positive charge density larger than any other bare cationic nanocolloid. It was observed that ANCC particles have a needle-like morphology with a width of ~ 5 nm and a length ~ 120 nm. DLS results proof that ANCC is hairy. Spectroscopic analysis confirmed the introduction of surface primary amine groups. ANCC showed promising bactericidal activities, against Gram-negative species due to their thinner and penetrable cell wall.


Assuntos
Celulose , Tensoativos , Aminação , Cátions , Oxirredução
6.
J Colloid Interface Sci ; 607(Pt 1): 488-501, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34509120

RESUMO

HYPOTHESIS: Naturally derived or synthetic anticancer peptides (ACPs) have emerged as a new generation of anticancer agents with higher selectivity for cancer cells and less propensity for drug resistance. Despite the structural diversity of ACPs, α-helix is the most common secondary structure among them. Herein we report the development of a new library of short cationic amphiphilic α-helical ACPs with selective cytotoxicity against colorectal and cervical cancer. EXPERIMENTS: The peptides had a general formula C(XXYY)3 with C representing amino acid cysteine (providing a -SH group for molecular conjugation), X representing hydrophobic amino acids (isoleucine (I) or leucine (L)), and Y representing cationic amino acids (arginine (R) or lysine (K)). Two variants of the peptides were synthesized by adding additional Isoleucine residues to the C-terminal and replacing the N-terminal cysteine with LC-propargylglycine (LC-G) to investigate the effect of N-terminal and C-terminal variation on the anticancer activity. The structure and physicochemical properties of the peptides were determined by RP-HPLC, LC-MS and CD spectroscopy. The cytotoxicity of the peptides in different cell lines was assessed by MTT test, cell proliferation assay and mitochondrial damage assay. The mechanism of cell selectivity of the peptides was investigated by studying their interfacial behaviour at the air/water and lipid/water interface using Langmuir trough. FINDINGS: The peptides consisting of K residues in their hydrophilic domains exhibited more selective anticancer activity whereas the peptides containing R exhibited strong toxicity in normal cells. The anticancer activity of the peptides was a function of their helical content and their hydrophobicity. Therefore, the addition of two I residues at C-terminal enhanced the anticancer activity of the peptides by increasing their hydrophobicity and their helical content. These two variants also exhibited strong anticancer activity against colorectal cancer multicellular tumour spheroids (MCTS). The higher toxicity of the peptides in cancer cells compared to normal cells was the result of higher penetration into the negatively charged cancer cell membranes, leading to higher cellular uptake, and their cytotoxic effect was mainly exerted by damaging the mitochondrial membranes leading to apoptosis. The results from this study provide a basis for rational design of new α-helical ACPs with enhanced anticancer activity and selectivity.


Assuntos
Peptídeos , Cátions , Dicroísmo Circular , Interações Hidrofóbicas e Hidrofílicas , Peptídeos/farmacologia , Conformação Proteica em alfa-Hélice , Estrutura Secundária de Proteína
7.
J Colloid Interface Sci ; 607(Pt 1): 556-567, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34520903

RESUMO

Here, we have developed a novel bilayer hollow amphiphilic biosorbent (BHAB-3) with large adsorption capacity, rapid adsorption kinetics, and cost-effective for the removal of Cr(VI) and Cu(II) from aqueous solutions. The synthesis was based on the clever use of freeze-drying to fix the structure, secondary modification of the carboxymethyl cellulose microspheres with polyethyleneimine and cross-linking by glutaraldehyde. The consequences of pH, initial concentration, contact time and temperature on adsorption were investigated. The Langmuir model fits showed that the maximum adsorption capacities of the two target heavy metal ions reached 835.91 and 294.79 mg/g, respectively. Moreover, BHAB-3 was characterized by SEM, FT-IR, TGA, and XPS synergistically, showing that it exhibits a strong complexation ability for Cu(II) and a strong electrostatic effect for Cr(VI). Adsorption and desorption experiments showed only a slight decrease in the adsorption capacity of the BHAB-3 for Cr(VI) and Cu(II) ions after 5 and 26 cycles, respectively. Given the excellent properties of this adsorbent, it is a promising candidate for heavy metal ion removal.


Assuntos
Poluentes Químicos da Água , Cátions , Cromo , Concentração de Íons de Hidrogênio , Espectroscopia de Infravermelho com Transformada de Fourier
8.
J Hazard Mater ; 421: 126705, 2022 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-34315017

RESUMO

In this study, a novel method-atom surface fragment contribution (ASFC)-was proposed for assessing the properties of compounds. We developed a predictive model using the ASFC method based on the sigma surface areas (Sσ-surface) of fragments/groups for estimating the toxicity of ILs. A toxicity dataset of 140 ILs towards leukemia rat cell line (ICP-81) was gathered and employed to train and validate models. The Sσ-surface values of atoms in each group were firstly calculated from the COSMO profiles of cations and anions for ILs. Then the Sσ-surface values of 26 groups were obtained and used as input descriptors for modelling. The R2 and MSE of the built ASFC model were 0.924 and 0.071, respectively. Results indicate that the ASFC model developed by the new approach possesses great accuracy and reliability. In total, the ASFC method has extensive potential for the application of estimating diverse properties of ILs and other compounds due to its remarkable advantages.


Assuntos
Líquidos Iônicos , Animais , Ânions , Cátions , Líquidos Iônicos/toxicidade , Relação Quantitativa Estrutura-Atividade , Ratos , Reprodutibilidade dos Testes
9.
Food Chem ; 371: 131130, 2022 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-34583179

RESUMO

A quinoline-naphthalene duo-based Schiff base probe (R) was synthesized and characterized by the usual spectroscopic and single-crystal X-ray crystallographic techniques. Probe R detects Al3+ and HSO3- ions via the fluorescent turn-on approach by dual pathways i.e., i) when probe R interacts with Al3+, the restriction of CN single bond rotation, blocking of both photoinduced electron transfer (PET) and CN isomerization were observed, and ii) when the sensor R interacts with HSO3-, imine (CH = N) bond was cleaved via hydrolysis and produced the respective aldehyde and amine behaving as a chemodosimeter. The binding stoichiometric ratio of R + Al3+ (1:1) was confirmed by Job's plot, emission titration profile, NMR, and mass spectrometric analyses. This probe R is highly selective to both Al3+ -ions and HSO3- -ions, without any interference of other potentially competing cations and anions. Limit of detection (LOD) and quantification (LOQ) of R with Al3+ and HSO3- were downed to nanomolar concentrations, which is much lower than the recommended level of drinking water/food fixed by the World Health Organization (WHO). Furthermore, probe R was utilized in the detection of Al3+ and HSO3- ions in highly contaminated real samples, bioimaging in E. coli cells, multiple-targeting molecular logic gate, and in bovine serum albumin (BSA) binding.


Assuntos
Alumínio , Quinolinas , Cátions , Escherichia coli , Corantes Fluorescentes , Naftalenos , Espectrometria de Fluorescência , Sulfitos
10.
Sensors (Basel) ; 21(22)2021 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-34833531

RESUMO

Solution-gated graphene field-effect transistors (SG-GFETs) provide an ideal platform for sensing biomolecules owing to their high electron/hole mobilities and 2D nature. However, the transfer curve often drifts in an electrolyte solution during measurements, making it difficult to accurately estimate the analyte concentration. One possible reason for this drift is that p-doping of GFETs is gradually countered by cations in the solution, because the cations can permeate into the polymer residue and/or between graphene and SiO2 substrates. Therefore, we propose doping sufficient cations to counter p-doping of GFETs prior to the measurements. For the pre-treatment, GFETs were immersed in a 15 mM sodium chloride aqueous solution for 25 h. The pretreated GFETs showed that the charge neutrality point (CNP) drifted by less than 3 mV during 1 h of measurement in a phosphate buffer, while the non-treated GFETs showed that the CNP was severely drifted by approximately 50 mV, demonstrating a 96% reduction of the drift by the pre-treatment. X-ray photoelectron spectroscopy analysis revealed the accumulation of sodium ions in the GFETs through pre-treatment. Our method is useful for suppressing drift, thus allowing accurate estimation of the target analyte concentration.


Assuntos
Grafite , Cátions , Polímeros , Dióxido de Silício , Transistores Eletrônicos
11.
Int J Mol Sci ; 22(19)2021 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-34639095

RESUMO

A 4-nitro-L-phenylalanine scaffold was used to construct effective ion pair receptors capable of binding anions in an enhanced manner with the assistance of alkali metal cations. A benzocrown ether was linked to a receptor platform via the amide function so as to support the squaramide function in anion binding and to allow all three NHs to act simultaneously. The binding properties of the receptors were determined using UV-vis, 1H NMR, 2D NMR, and DOSY spectroscopy in MeCN and in the solid state by X-ray measurements. Ion pair receptor 2 was found to interact with the most strongly with salts, and the removal of its key structural elements was shown to hinder the receptor action. The amide proton was recognized to switch from having involvement in an intramolecular hydrogen bond to interacting with anions upon complexation. Apart from carboxylates, which promote deprotonation, and other monovalent salts creating 1:1 complexes with the receptor, more complex equilibria were established upon the complexation of 2 with sulfates. Receptor 2 was shown to be capable of the extraction of ion pairs from the aqueous to organic phase and of the cation-enhanced transport chloride and sulfate anions across a bulk chloroform membrane. These features may open the door for its use in regulating ion concertation under interfacial conditions and acting as a potential drug to treat channelopathies.


Assuntos
Aminoácidos/metabolismo , Ânions/metabolismo , Cátions/metabolismo , Sais/metabolismo , Sulfatos/metabolismo , Aminoácidos/química , Ânions/química , Cátions/química , Cristalografia por Raios X , Ligação de Hidrogênio , Modelos Moleculares , Estrutura Molecular , Sais/química , Sulfatos/química
12.
Phys Chem Chem Phys ; 23(40): 23203-23213, 2021 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-34622888

RESUMO

Electrostatic interactions are central to the structure and function of nucleic acids, including their folding, condensation, and interaction with proteins and other charged molecules. These interactions are profoundly affected by ions surrounding nucleic acids, the constituents of the so-called ion atmosphere. Here, we report precise Fourier Transform-Terahertz/Far-Infrared (FT-THz/FIR) measurements in the frequency range 30-500 cm-1 for a 24-bp DNA solvated in a series of alkali halide (NaCl, NaF, KCl, CsCl, and CsF) electrolyte solutions which are sensitive to changes in the ion atmosphere. Cation excess in the ion atmosphere is detected experimentally by observation of cation modes of Na+, K+, and Cs+ in the frequency range between 70-90 cm-1. Based on MD simulations, we propose that the magnitude of cation excess (which is salt specific) depends on the ability of the electrolyte to perturb the water network at the DNA interface: In the NaF atmosphere, the ions reduce the strength of interactions between water and the DNA more than in case of a NaCl electrolyte. Here, we explicitly take into account the solvent contribution to the chemical potential in the ion atmosphere: A decrease in the number of bound water molecules in the hydration layer of DNA is correlated with enhanced density fluctuations, which decrease the free energy cost of ion-hydration, thus promoting further ion accumulation within the DNA atmosphere. We propose that taking into account the local solvation is crucial for understanding the ion atmosphere.


Assuntos
DNA/química , Água/química , Cátions/química , Simulação de Dinâmica Molecular , Cloreto de Potássio/química , Cloreto de Sódio/química , Eletricidade Estática , Espectroscopia Terahertz
13.
Se Pu ; 39(11): 1273-1278, 2021 Nov.
Artigo em Chinês | MEDLINE | ID: mdl-34677023

RESUMO

Hemoglobin A1c (HbA1c) is a major component of glycated hemoglobin in human red blood cells. It has been proven to be a significant biomarker for the diagnosis of diabetes; its content in fresh red cells in diabetes blood reflects the average level of blood glucose over the previous three months. Thus, HbA1c level has been used for the assessment of long-term glycemic control in diabetes; the level of 6.5% HbA1c has been certified as a critical cut-off for the diabetes diagnosis. The current commonly used method for HbA1c quantification is based on cation-exchange high performance liquid chromatography (CX-HPLC). The method has advantages such as high stability, rapidity, and automation, but there are still some unidentified peaks of Hb species in CX-HPLC (VARIANT Ⅱ system); in particular, the presence of HbA3 (a glutathiolated Hb) affects the accurate determination of HbA1c. HbA3 is usually present in healthy adult blood samples at 2%-4%, but the concentration of HbA3 increases due to the protection of erythrocytes from oxidation, resulting in decreased HbA1c. However, the relative location of the HbA3 peak in the CX-HPLC clinical chromatogram has not been established. To address this issue, we extracted Hb species from fresh blood samples obtained from a hospital in an anaerobic environment to avoid possible redox reactions of Hb and glutathione. After the extraction, the Hb samples were analyzed using two methods: a low-resolution CX-HPLC (5/50 mm column) currently used for diabetes diagnosis and a high-resolution cationic exchange HPLC (Mono-S 5/50 mm column), to identify the peak corresponding to HbA3. The CX-HPLC analysis of fresh blood samples indicated that the unknown peak P3 located between HbA1c and HbA0 peaks corresponded to the HbA3 peak between HbA1c and HbA0 in the Mono-S-HPLC. Microarray isoelectric focusing (IEF) was used for the micro-preparation of HbA3, HbA1c, and HbA0 in healthy blood samples; then, the micro-prepared species of HbA3, HbA1c, and HbA0 were individually identified via Mono-S-HPLC. The results of the CX-HPLC, Mono-S-HPLC, and microarray IEF experiments indicated that the P3 peak might correspond to HbA3. To confirm this, glutathiolated Hb samples were synthesized via acetylphenylhydrazine and analyzed using both the Mono-S- and CX-HPLC systems. The results showed that the content of both glutaminated hemoglobin of HbA3 in Mono-S-HPLC and P3 in CX-HPLC increased, implying the peak of P3 with the retention time of 1.50 min in CX-HPLC was the peak corresponding to HbA3 in Mono-S-HPLC and microarray IEF. Based on the above experiments and our previous results, the influence of HbA3 on both the analysis of HbA1c in blood samples and the diabetes diagnosis needs to be considered and discussed. The study results are significant for the tentative assignment of peak P3 and for offering more information on diabetes diagnosis using CX-HPLC in the clinical setting.


Assuntos
Diabetes Mellitus , Hemoglobina A , Cátions , Diabetes Mellitus/diagnóstico , Hemoglobina Falciforme , Humanos , Focalização Isoelétrica
14.
Anal Chem ; 93(43): 14365-14368, 2021 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-34670079

RESUMO

Gas phase ion/ion reactions between singly charged radical reagent anions and multiply charged cation precursors primarily result in either proton or electron transfer. These ion/ion reactions have been extensively studied for bioanalysis, and many reagent anions have been tested and reported. Here, nitrogen-containing aromatic radical anions were tested for the ability to conduct proton or electron transfer by their reaction with the ubiquitin [M + 13H]+13 precursor. The singly charged anion of 2,2'-biquinoline was found to undergo charge inversion to singly protonated cations via near-simultaneous proton and electron transfers while reactants were bound in a single ion/ion reaction complex. Although the focus of this paper was 2,2'-biquinoline, all three nitrogen-containing aromatic compounds tested produced similar results.


Assuntos
Nitrogênio , Prótons , Ânions , Cátions , Elétrons
15.
Environ Sci Technol ; 55(21): 14863-14875, 2021 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-34677944

RESUMO

While polyamide reverse osmosis and nanofiltration membranes have been extensively utilized in water purification and desalination processes, the molecular details governing water and solute permeation in these membranes are not fully understood. In this study, we apply transition-state theory for transmembrane permeation to systematically break down the intrinsic permeabilities of water and small ions in loose and tight polyamide nanofiltration membranes into enthalpic and entropic components using an Eyring-type equation. We analyze trends in these components to elucidate molecular phenomena that induce water-salt, monovalent-divalent, and monovalent-monovalent selectivity at different pH values. Our results suggest that in pores that are either too small or contain an electrostatically repelling mouth, the thermal activation of ions in the form of ion dehydration is less likely, promoting entropically driven selectivity with steric exclusion of hydrated ions. Instead, larger uncharged pores enable ion dehydration, inducing enthalpic selectivity that is driven by differences in the ion hydration properties. We also demonstrate that electrostatic interactions between cations and intrapore carboxyl groups hinder salt permeability, increasing the enthalpic barrier of the transport. Last, permeation tests of monovalent cations in the loose and tight polyamide membranes expose opposite rejection trends that further support the phenomenon of ion dehydration in large subnanopores.


Assuntos
Nylons , Purificação da Água , Cátions , Filtração , Membranas Artificiais , Água
16.
Part Fibre Toxicol ; 18(1): 37, 2021 10 14.
Artigo em Inglês | MEDLINE | ID: mdl-34649580

RESUMO

BACKGROUND: Precisely how silver nanoparticles (AgNPs) kill mammalian cells still is not fully understood. It is not clear if AgNP-induced damage differs from silver cation (Ag+), nor is it known how AgNP damage is transmitted from cell membranes, including endosomes, to other organelles. Cells can differ in relative sensitivity to AgNPs or Ag+, which adds another layer of complexity to identifying specific mechanisms of action. Therefore, we determined if there were specific effects of AgNPs that differed from Ag+ in cells with high or low sensitivity to either toxicant. METHODS: Cells were exposed to intact AgNPs, Ag+, or defined mixtures of AgNPs with Ag+, and viability was assessed. The level of dissolved Ag+ in AgNP suspensions was determined using inductively coupled plasma mass spectrometry. Changes in reactive oxygen species following AgNP or Ag+ exposure were quantified, and treatment with catalase, an enzyme that catalyzes the decomposition of H2O2 to water and oxygen, was used to determine selectively the contribution of H2O2 to AgNP and Ag+ induced cell death. Lipid peroxides, formation of 4-hydroxynonenol protein adducts, protein thiol oxidation, protein aggregation, and activation of the integrated stress response after AgNP or Ag+ exposure were quantified. Lastly, cell membrane integrity and indications of apoptosis or necrosis in AgNP and Ag+ treated cells were examined by flow cytometry. RESULTS: We identified AgNPs with negligible Ag+ contamination. We found that SUM159 cells, which are a triple-negative breast cancer cell line, were more sensitive to AgNP exposure less sensitive to Ag+ compared to iMECs, an immortalized, breast epithelial cell line. This indicates that high sensitivity to AgNPs was not predictive of similar sensitivity to Ag+. Exposure to AgNPs increased protein thiol oxidation, misfolded proteins, and activation of the integrated stress response in AgNP sensitive SUM159 cells but not in iMEC cells. In contrast, Ag+ cause similar damage in Ag+ sensitive iMEC cells but not in SUM159 cells. Both Ag+ and AgNP exposure increased H2O2 levels; however, treatment with catalase rescued cells from Ag+ cytotoxicity but not from AgNPs. Instead, our data support a mechanism by which damage from AgNP exposure propagates through cells by generation of lipid peroxides, subsequent lipid peroxide mediated oxidation of proteins, and via generation of 4-hydroxynonenal (4-HNE) protein adducts. CONCLUSIONS: There are distinct differences in the responses of cells to AgNPs and Ag+. Specifically, AgNPs drive cell death through lipid peroxidation leading to proteotoxicity and necrotic cell death, whereas Ag+ increases H2O2, which drives oxidative stress and apoptotic cell death. This work identifies a previously unknown mechanism by which AgNPs kill mammalian cells that is not dependent upon the contribution of Ag+ released in extracellular media. Understanding precisely which factors drive the toxicity of AgNPs is essential for biomedical applications such as cancer therapy, and of importance to identifying consequences of unintended exposures.


Assuntos
Nanopartículas Metálicas , Prata , Animais , Cátions , Morte Celular , Peróxido de Hidrogênio/toxicidade , Nanopartículas Metálicas/toxicidade , Prata/toxicidade
17.
Biomater Sci ; 9(22): 7636-7647, 2021 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-34676384

RESUMO

The delivery of therapeutic genes to a specific organ has drawn significant research attention. Among the pool of various delivery vectors, cationic liposomes (non-viral) are potential candidates for delivering therapeutic genes due to their low immunogenic response. Here, we have developed novel ferrocene-conjugated cationic tocopheryl aggregates as non-viral vectors. These formulations can transfer a reporter gene (pGL3; encoded for luciferase protein) specifically to liver cancer cells (HepG2 and Huh7) instead of non-hepatic cancer cells, such as Caco-2 (human colon carcinoma) and HeLa (cervical cancer) cells. The transfection efficiency (TE) of the optimum liposomal formulation is more significant than commercially available Lipofectamine 2000 (L2K). Notably, it retains its TE under high serum conditions (up to 50% FBS). A coupled effect from conjugated ferrocene and tocopherol in the cationic liposomal formulation might be responsible for the cell-specific delivery and higher serum compatibility. Therefore, the present proposed delivery system may provide a platform for further progress in terms of developing hepatotropic gene delivery systems.


Assuntos
Neoplasias Hepáticas , alfa-Tocoferol , Células CACO-2 , Cátions , Técnicas de Transferência de Genes , Humanos , Lipossomos , Neoplasias Hepáticas/genética , Metalocenos , Transfecção , Transgenes
18.
Water Res ; 206: 117761, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34678698

RESUMO

The combined fouling effect prevalent in the nanofiltration (NF) process severely limits its use. In this study, cation exchange membrane (CEM) electrolysis was performed to alleviate NF membrane fouling by controlling interface characteristics. The results revealed that CEM electrolysis (hydraulic retention time with 0.24 or 0.36 h) effectively improved NF membrane permeability by 201%-211% and achieved a stability of > 8 LMH/bar. The divalent cations were removed through CEM electrolysis, with a decrease in Ca2+ and Mg2+ by approximately 68.8% and 30.9%, respectively, which was related to scaling potential reduction. This softening function reduced the possibility of bridging of organics with divalent cations, which contributed to the lower molecular weight of organic matter (mainly humic substances) distributed in 1.4-23 kDa. The improved organic indicators of the NF membrane permeate quality implied that the membrane interface characteristics improved. The foulant layer on the NF membrane dominated humic substances, and biopolymers exhibited hydrophobic, smooth, and porous characteristics. The self-aggregation of foulants on the NF membrane surface stimulated the interface characteristics with high water permeability. Energy consumption confirmed the feasibility of CEM electrolysis on NF application. Thus, CEM electrolysis as a chemical-free approach that can be combined with NF and can provide guidance for NF membrane fouling in urban water treatment and water reclamation.


Assuntos
Ultrafiltração , Purificação da Água , Cátions , Eletrólise , Estudos de Viabilidade , Membranas Artificiais
19.
Soft Matter ; 17(41): 9315-9325, 2021 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-34605526

RESUMO

DNA-assisted assembly of ligand-stabilized gold nanoparticles is studied using Monte Carlo simulations with coarse-grained models for DNA and AuNP. Their interaction in a periodic simulation box is described by a combination of electrostatic and pairwise hard core potentials. We first probe the self-assembly of AuNPs resulting in an ordered distribution on a single fixed DNA strand. Subsequently, the effective force calculated between a pair of parallel DNA in the presence of AuNPs shows the attraction between them at short distance associated to a stable equilibrium position. Finally, the osmotic pressure calculated in a compact DNA-AuNP lattice with various amounts of monovalent salt ions shows that an increasing amount of salt prevents aggregate formation.


Assuntos
Ouro , Nanopartículas Metálicas , Cátions , DNA , Método de Monte Carlo
20.
Int J Mol Sci ; 22(19)2021 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-34638799

RESUMO

Bone-forming cells or osteoblasts play an important role in bone modeling and remodeling processes. Osteoblast differentiation or osteoblastogenesis is orchestrated by multiple intracellular signaling pathways (e.g., bone morphogenetic proteins (BMP) and Wnt signaling pathways) and is modulated by the extracellular environment (e.g., parathyroid hormone (PTH), vitamin D, transforming growth factor ß (TGF-ß), and integrins). The regulation of bone homeostasis depends on the proper differentiation and function of osteoblast lineage cells from osteogenic precursors to osteocytes. Intracellular Ca2+ signaling relies on the control of numerous processes in osteoblast lineage cells, including cell growth, differentiation, migration, and gene expression. In addition, hyperpolarization via the activation of K+ channels indirectly promotes Ca2+ signaling in osteoblast lineage cells. An improved understanding of the fundamental physiological and pathophysiological processes in bone homeostasis requires detailed investigations of osteoblast lineage cells. This review summarizes the current knowledge on the functional impacts of K+ channels and Ca2+-permeable channels, which critically regulate Ca2+ signaling in osteoblast lineage cells to maintain bone homeostasis.


Assuntos
Canais de Cálcio/metabolismo , Osteoblastos/metabolismo , Osteogênese , Canais de Potássio/metabolismo , Transdução de Sinais , Animais , Cálcio/química , Cálcio/metabolismo , Cátions/metabolismo , Humanos , Osteoblastos/fisiologia , Potássio/química , Potássio/metabolismo
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