RESUMO
Microfiltration (MF) has been widely adopted as an advanced treatment process to reduce suspended solids and turbidity in treated wastewater effluents designated for potable reuse. Although microfilter pores are much larger than viruses, the addition of a coagulant upstream of a microfilter system can achieve stable virus removal. Ceramic membranes have a narrow pore size distribution to achieve the high removal of contaminants. This study aims to evaluate virus log reduction using bench-scale coagulation and ceramic membrane MF. To investigate the effects of differences in net surface hydrophobicity, 18 sewage-derived F-specific RNA phages (FRNAPHs) were used for batch hydrophobicity and coagulation-MF tests. The capability of bench-scale coagulation and ceramic membrane MF under continuous automated long-term operation was tested to remove the lab reference strain MS2 and three selected FRNAPH isolates which varied by surface property. Median virus log reduction values (LRVs) exceeding 6.2 were obtained for all three isolates and MS2. Although coagulation and hydrophobicity were positively correlated, the virus isolate demonstrating the lowest level of hydrophobicity and coagulation (genogroup I) still exhibited a high LRV. Thus, coagulation and ceramic membrane MF systems may serve as viable options for virus removal during water reclamation and advanced treatment.
Assuntos
Fagos RNA , Vírus , Purificação da Água , Ultrafiltração , Cerâmica/química , Membranas ArtificiaisRESUMO
Hydroxyapatite (HA) is the main inorganic component of human bones and teeth. It has good biocompatibility and bioactivity, which promotes its good application prospects in the field of bone drug carriers. In this study, tetraethylenepentamine-graphene (rGO-TEPA)/CaCO3:HA composite microspheres were prepared via microwave hydrothermal synthesis using rGO-TEPA/CaCO3 solid microspheres as intermediates. Furthermore, the incompletely transformed CaCO3 was removed by soaking in a citric acid buffer to obtain rGO-TEPA/HA hollow composite microspheres. The two types of as-prepared composite microspheres exhibited sea urchin-like structures, large BET surface areas, and good dispersibility. Mouse preosteoblast cells (MC3T3-E1) were used for in vitro cytotoxicity experiments. The in vitro cell viability test showed that the two composite drug carriers exhibited noncytotoxicity. Moreover, the doxorubicin (DOX) loading and releasing investigations revealed that the two types of prepared carriers had mild storage-release behaviors and good pH responsiveness. Hence, these rGO-TEPA/HA hollow microspheres have promising applications as bone drug carriers.
Assuntos
Materiais Biomiméticos , Osso e Ossos/metabolismo , Portadores de Fármacos/química , Portadores de Fármacos/metabolismo , Durapatita , Grafite , Microesferas , Ouriços-do-Mar , Animais , Osso e Ossos/citologia , Sobrevivência Celular/efeitos dos fármacos , Portadores de Fármacos/farmacologia , Etilenodiaminas , Concentração de Íons de Hidrogênio , Camundongos , Osteoblastos/citologia , Osteoblastos/efeitos dos fármacos , Células-Tronco/efeitos dos fármacosRESUMO
To obtain high quality of drinking water free from biocontaminants is especially important issue. A new strategy employing smectic liquid-crystalline ionic membranes exhibiting 2D structures of layered nanochannels for water treatment is proposed for efficient virus removal and sufficient water flux. The smectic A (SmA) liquid-crystalline membranes obtained by in situ polymerization of an ionic mesogenic monomer are examined for removal of three distinct viruses with small size: Qß bacteriophage, MS2 bacteriophage, and Aichi virus. The semi-bilayer structure of the SmA significantly obstructs the virus penetration with an average log reduction value of 7.3 log10 or the equivalent of reducing 18 million viruses down to 1. Furthermore, the layered nanochannels of the SmA liquid crystal allow efficient water permeation compared to other types of liquid-crystalline membrane consisting of nanopores.
Assuntos
Cristais Líquidos , Nanoestruturas , Vírus , Purificação da Água , Membranas ArtificiaisRESUMO
Three new cardenolides (3, 9 and 10), along with eight known ones, were isolated from the latex of Calotropis procera. The structural determination was accomplished by the 1D- and 2D-NMR spectra as well as HRESIMS analysis. The growth inhibitory activity of the latex and its sub-fractions as well as isolated compounds was evaluated against human A549 and Hela cell lines. The results exhibited that latex had strong growth inhibitory activity with IC50s of (3.37 µM, A-549) and (6.45 µM, Hela). Among the four extracts (hexane, chloroform, ethyl acetate and aqueous), chloroform extract displayed the highest potential cytotoxic activity, with IC50s of (0.985 µM, A-549) and (1.471 µM, Hela). All the isolated compounds displayed various degrees of cytotoxic activity and the highest activity was observed by calactin (1) with IC50s values of (0.036 µM, A-549) and (0.083 µM, Hela). None of these isolated compounds exhibited good antimicrobial activity evaluated by determination of their MICs using the broth microdilution method against various infectious pathogens. The structure-activity relationships for cytotoxic activity were also discussed.
Assuntos
Antibacterianos/farmacologia , Antifúngicos/farmacologia , Antineoplásicos Fitogênicos/farmacologia , Calotropis/química , Cardenolídeos/farmacologia , Látex/química , Antibacterianos/química , Antibacterianos/isolamento & purificação , Antifúngicos/química , Antifúngicos/isolamento & purificação , Antineoplásicos Fitogênicos/química , Antineoplásicos Fitogênicos/isolamento & purificação , Bactérias/efeitos dos fármacos , Cardenolídeos/química , Cardenolídeos/isolamento & purificação , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Fungos/efeitos dos fármacos , Células HeLa , Humanos , Testes de Sensibilidade Microbiana , Estrutura Molecular , Relação Estrutura-AtividadeRESUMO
The clinical effectiveness of the erbium-doped yttrium-aluminum-garnet (Er:YAG) laser in patients with peri-implantitis remains unclear. The aim of this meta-analysis was to investigate the efficacy and safety of Er:YAG laser (ERL) compared to subgingival mechanical debridement (SMD) for the treatment of peri-implantitis. A systematic electronic literature search was conducted to identify randomized clinical trials (RCTs), followed by a manual search. Results were expressed as weighted mean differences (WMDs) with accompanying 95 % confidence intervals (CIs). The primary outcome measurements were changes in clinical attachment level (CAL) and probing depth (PD). Secondary outcome measurements included changes in gingival recession (GR). The meta-analysis was performed with fixed-effect or random-effect model according to the heterogeneity assessed by I (2) test. Visual asymmetry inspection of the funnel plot, Egger's regression test, and the trim-and-fill method were used to investigate publication bias. At 6 months, significant difference in PD reduction (p = 0.018) was observed for Er:YAG laser compared to SMD treatment, while no significant differences were detected in CAL gain and GR change; at 12 months, no significant difference was observed for any investigated outcome. The findings of this meta-analysis suggest that use of the Er:YAG laser as alternative to SMD could potentially provide short-time additional benefits, while there is no evidence of long-time superior effectiveness. As all included studies were not at low risk of bias, and only four studies were included in the meta-analysis, future long-term and well-designed RCTs reporting clinical and microbiological outcomes, considering the cost/effectiveness ratio, and having a high methodological quality are needed to clarify the effectiveness of Er:YAG laser.
Assuntos
Lasers de Estado Sólido/uso terapêutico , Terapia com Luz de Baixa Intensidade , Peri-Implantite/radioterapia , Humanos , Ensaios Clínicos Controlados Aleatórios como Assunto , Resultado do TratamentoRESUMO
Huangqi Liuyi Decoction, a famous classical Chinese prescription, shows significant curative effect on diabetes and its complications, in which calycosin-7-glucoside, liquiritin and glycyrrhizic acid are the main components that playing these mentioned pharmacological activity, under the synergistic action of various other ingredients in the decoction. However, there are significant differences in the content of active compounds in Chinese medicinal materials, which mainly due to origin, picking seasons, and processing methods. Hence, the accurate content of the glycosides is the prerequisite for ensuring the pharmacological efficacy. Aiming at establishing an efficient extraction and determination method for accurate quantitative analysis of calycosin-7-glucoside, liquiritin and glycyrrhizic acid in Huangqi Liuyi Decoction, an on line solid-phase extraction-high-performance liquid chromatography method was developed, using a homemade bio-based monolithic adsorbent. The bio-based adsorbent was prepared in a stainless steel tube, using bio-monomers of methyleugenol and S-allyl-L-cysteine, which effectively reduced the dependence of the polymer field on non-renewable fossil resources and reduced carbon emissions. Furthermore, the prepared adsorbent owned abundant chemical groups, which can produce interactions of hydrogen bond, dipole-dipole, π-π and hydrophobic force with the target glycosides, thus improving the specific recognition ability of the adsorbent. The experiments were carried out on an LC-3000 HPLC instrument with a six-way valve. Methodology validation indicates that the recovery is in the range of 97.0%-103.4% with the RSD in the range of 1.6%-4.0%, due to the specific selectivity of the bio-based monolithic adsorbent for these three glycosides, and good matrix-removal ability for Huangqi Liuyi decoction. The limit of detection is 0.17, 0.50 and 0.33 µg/mL for calycosin-7-glucoside, liquiritin and glycyrrhizic acid, respectively, and the limit of quantitation is 0.50, 1.50 and 1.00 µg/mL, respectively, with the linear range of 2-200 µg/mL for calycosin-7-glucoside, and 5-500 µg/mL for liquiritin and glycyrrhizic acid. The present work provided a simple and efficient method for the extraction and determination of glycosides in complex medicinal plants.
Assuntos
Astragalus propinquus , Medicamentos de Ervas Chinesas , Glicosídeos , Polímeros/análise , Ácido Glicirrízico , Medicamentos de Ervas Chinesas/química , Glucosídeos/análise , Cromatografia Líquida de Alta Pressão/métodosRESUMO
The decrease of cellulase activity and unproductive adsorption of lignin are important obstructive factors for inefficient enzymatic hydrolysis. This paper applied five different kinds of biosurfactants including rhamnolipid, sophorolipid, chitin, tea saponin, and sodium lignosulfonate in the enzymatic hydrolysis process of alkali-pretreated reed straw (RS) to enhance the saccharification efficiency. When 8 g/L sophorolipid is added, the efficiency of enzymatic hydrolysis is 91.68 %, which is 30.65 % higher than that without using any biosurfactant. The efficiency of enzymatic hydrolysis can be further increased to 99.56 % when 7.5 g/L sophorolipid and 1.5 g/L tea saponin are added together. This is because the sophorolipid, rhamnolipid, and chitin can synergistically hamper the enzymatic inactivation during enzymatic hydrolysis, while tea saponin and sodium lignosulfonate can inhibit the non-productive adsorption of lignin. This work proposed a very effective method to improve the efficiency of enzymatic hydrolysis and reduce the dosage of the enzyme by adding biosurfactants.
Assuntos
Celulase , Lignina , Álcalis , Hidrólise , Quitina , CháRESUMO
Food-borne methicillin-resistance Staphylococcus aureus (MRSA) has caused significant health threats and economic loss in livestock and poultry products. Garlic essential oil (GEO) is an effective antibacterial agent but presents strong instability and hydrophobicity. In this study, GEO in water nanoemulsion (GEON) with good stability was produced by emulsification technique of high-power ultrasound. Its antibacterial activity and underlying mechanism against MRSA isolated from retailed pork were investigated. Results showed that ultrasonic treatment significantly reduced the particle size of GENO from 820.3 to 215.0 nm as time increased from 0 to 10 min. Comparatively, GEON of 10 min ultrasound was more stable than other GEONs (0, 1, 5 min) during 30 d storage. It also displayed good thermal stability and relatively good ion stability (NaCl, MgCl2, and glucose). Antibacterial analysis showed that GEON (10 min) exhibited the best anti-MRSA activity among all GEONs, and the minimum inhibitory concentration of GEO in this nanoemulsion was 0.125 % (1.25 mg/mL). Treatment of GEON (10 min) significantly suppressed the cell proliferation of MRSA, which was mainly achieved by damaging the cell membrane as evidenced by membrane depolarization and considerable leakage of intracellular nucleic acids and protein. Laser scanning confocal microscope and scanning electron microscopy showed that treatment of GEON (10 min) significantly altered the membrane integrity and severely damaged the cellular membrane and structure. The present work illustrated that GEON produced by ultrasonic emulsification is a promising alternative to inhibit the contamination and spread of MRSA in livestock and poultry products.
Assuntos
Alho , Staphylococcus aureus Resistente à Meticilina , Óleos Voláteis , Carne de Porco , Carne Vermelha , Suínos , Animais , Óleos Voláteis/química , Água/farmacologia , Cloreto de Polivinila , Antibacterianos/química , Testes de Sensibilidade MicrobianaRESUMO
Microplastics (MPs) can adsorb antibiotics to form complex pollutants, which seriously threatens the health of freshwater ecosystems. Few studies have examined the combined pollution characteristics of microplastics (MPs) and antibiotics in restored freshwater ecosystems and their effects on the growth traits of the aquatic primary producers. We studied both the ecotoxicological effects of polyethylene (PE) MPs and the antibiotics sulfanilamide (sulfa, SA) on the structural (diversity etc.,) and functional (nutrient cycling etc.,) properties of water-plant-sediment ecosystems. The synergistic toxic effects of PE and SA resulted in a reduction in the chlorophyll content and chloroplast fluorescence. Meanwhile, PE and SA single/combined pollution stress inhibits the radial oxygen loss in roots, and activates the antioxidant defense system in leaves. The change in the growth response characteristics of Vallisneria natans (V. natans) under oxidative stress induced by single/combined pollution showed a dosage effect. The microbial compositions of the overlying water and sediment were significantly changed by the pollution exposure, as evidenced by the increased microbial diversity and altered microbial taxa distribution. An increase in the total concentrations of sulfa in the overlying water was accompanied by an increase in the relative abundances of resistance genes. PE-MPs significantly affected the removal of total nitrogen and antibiotics from the overlying water. The interaction between PE and SA affects ammonia and nitrite nitrogen exchange in water-sediment systems. Thus, this study investigated the effects of combined MP and antibiotics pollution on the growth state, metabolic function, microbial community structure and microbial diversity of the freshwater ecosystems. The mechanism underlying of the combined polyethylene-sulfanilamide (PE-SA) effect on the V. natans was revealed. In addition, the correlation between different environmental factors was analyzed, and a structural equation model was constructed. This study provides primary data for evaluating the ecological and environmental effects of combined PE-SA pollution and its possible risks. Moreover, it provides a reference index for the study of ecological wetland environments and phytoremediation.
Assuntos
Hydrocharitaceae , Poluentes Químicos da Água , Microplásticos , Ecossistema , Plásticos , Antibacterianos , Poluentes Químicos da Água/análise , Água Doce , Polietileno , Nitrogênio , Água , SulfanilamidasRESUMO
Enterovirus infections can cause hand, foot, and mouth disease (HFDM), aseptic meningitis, encephalitis, myocarditis, and acute flaccid myelitis, leading to death of infants and young children. However, no specific antiviral drug is currently available for the treatment of this type of infection. The Unites States and United Kingdom health authorities recently approved a new antiviral drug, molnupiravir, for the treatment of COVID-19. In this study, we reported that molnupiravir (EIDD-2801) and its active form, EIDD-1931, have broad-spectrum anti-enterovirus potential. Our data showed that EIDD-1931 could significantly reduce the production of EV-A71 progeny virus and the expression of EV-A71 viral protein at non-cytotoxic concentrations. The results of the time-of-addition assay suggest that EIDD-1931 acts at the post-entry step, which is in accordance with its antiviral mechanism. The intraperitoneal administration of EIDD-1931 and EIDD-2801 protected 1-day-old ICR suckling mice from lethal EV-A71 challenge by reducing the viral load in various tissues of the infected mice. The pharmacokinetics analysis indicated that the plasma drug concentration overwhelmed the EC50 for enteroviruses, suggesting the clinical potential of molnupiravir against enteroviruses. Thus, molnupiravir along with its active form, EIDD-1931, may be a promising drug candidate against enterovirus infections.
Assuntos
COVID-19 , Enterovirus Humano A , Infecções por Enterovirus , Enterovirus , Animais , Antígenos Virais/metabolismo , Antivirais/metabolismo , Antivirais/farmacologia , Antivirais/uso terapêutico , Pré-Escolar , Citidina/análogos & derivados , Enterovirus/metabolismo , Infecções por Enterovirus/tratamento farmacológico , Humanos , Hidroxilaminas , Camundongos , Camundongos Endogâmicos ICRRESUMO
ß-Amyloid (Aß) fibrillogenesis is closely associated with the pathogenesis of Alzheimer's disease (AD), so detection and inhibition of Aß aggregation are of significance for the theranostics of AD. In this work, the coassembled nanoparticles of chitosan and hyaluronic acid cross-linked with glutaraldehyde (CHG NPs) were found to work as a theranostic agent for imaging/probing and inhibition of Aß fibrillization both in vitro and in vivo. The biomass-based CHG NPs of high stability exhibited a wide range of excitation/emission wavelengths and showed binding affinity toward Aß aggregates, especially for soluble Aß oligomers. CHG NPs displayed weak emission in the monodispersed state, while they remarkably emitted increased red fluorescence upon interacting with Aß oligomers and fibrils, showing high sensitivity with a detection limit of 0.1 nM. By comparing the different fluorescence responses of CHG NPs and Thioflavin T to Aß aggregation, the Aß oligomerization rate during nucleation can be determined. Moreover, the fluorescence recognition behavior of CHG NPs was selective. CHG NPs specifically bind to negatively charged amyloid aggregates but not to positively charged amyloids and negatively charged soluble proteins. Such enhancement in fluorescence emission is attributed to the clustering-triggered emission effect of CHG NPs after interaction with Aß aggregates via various electronic conjugations and hydrogen bonding, electrostatic, and hydrophobic interactions. Besides fluorescent imaging/probing, CHG NPs over 360 µg/mL could almost completely inhibit the formation of Aß fibrils, exhibiting the capability of regulating Aß aggregation. In-vivo assays with Caenorhabditis elegans CL2006 demonstrated the potency of CHG NPs as an effective theranostic nanoagent for imaging Aß plaques and inhibiting Aß deposition. The findings proved the potential of CHG NPs for development as a potent agent for the diagnosis and treatment of AD.
Assuntos
Peptídeos beta-Amiloides/antagonistas & inibidores , Antibacterianos/farmacologia , Materiais Biocompatíveis/farmacologia , Quitosana/farmacologia , Ácido Hialurônico/farmacologia , Nanopartículas/química , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Animais , Antibacterianos/química , Materiais Biocompatíveis/química , Caenorhabditis elegans/efeitos dos fármacos , Linhagem Celular Tumoral , Quitosana/química , Fluorescência , Humanos , Ácido Hialurônico/química , Testes de Sensibilidade Microbiana , Tamanho da Partícula , Agregados Proteicos/efeitos dos fármacos , Propriedades de Superfície , Nanomedicina TeranósticaRESUMO
The launch of China's new national urbanization plan, coupled with increasing concerns about air pollution, calls for better understandings of the nexus between urbanization and the air pollution-related health. Based on refined estimates of PM2.5 related mortality in China, we developed an Urbanization-Excess Deaths Elasticity (U-EDE) indicator to measure the marginal PM2.5 related mortality caused by urbanization. We then applied statistical models to estimate U-EDE and examined the modification effects of income on U-EDE. Urbanization in China between 2004 and 2012 led to increased PM2.5 related mortality. A 1% increase in urbanization was associated with a 0.32%, 0.14%, and 0.50% increase in PM2.5 related mortality of lung cancer, stroke, and ischemic heart disease. U-EDEs were modified by income with an inverted U curve, i.e., lower marginal impacts at the lowest and highest income levels. In addition, we projected the future U-EDE trend of China as a whole and found that China had experienced the peak of U-EDE and entered the second half of the inverted U-shaped curve. In the near future, national average U-EDE in China will decline along with the improvement of income level if no dramatic changes happen. However, the decreased U-EDE only implies that marginal PM2.5-related mortality brought by urbanization would decrease in China. Total health damage of urbanization will keep going up in the predictable future because the U-EDE is always positive.
Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/estatística & dados numéricos , Exposição Ambiental/estatística & dados numéricos , Mortalidade/tendências , Material Particulado/análise , Poluição do Ar/análise , China , Previsões , Humanos , Neoplasias Pulmonares , Cimentos de Resina , Urbanização/tendênciasRESUMO
INTRODUCTION: Recently, hantaviruses have been discovered in insectivores in Europe, Asia, Africa, and North America. Imjin virus (MJNV) was first isolated from the lung tissues of Ussuri white-toothed shrew (Crocidura lasiura) from South Korea in 2009. We aim to detect the species and prevalence of insectivore- and rodent-borne hantaviruses in shrews and rodents. MATERIALS AND METHODS: Shrews and rodents were captured in Jiaonan County of Shandong Province, China, in 2014. RT-PCR was used to amplify viral RNA of Hantavirus species, including insectivore-borne Imjin virus (MJNV), rodent-borne Hantaan virus (HTNV), and Seoul virus (SEOV) from shrews and rodents. RESULTS AND DISCUSSION: We found that MJNV infected 10.7% (19/178) of Crocidura shrews, but it infected none of rodents (0/475); we also found that 2 of 178 (1.1%) Crocidura shrews were PCR positive to SEOV. This study indicated that the major animal hosts of Imjin virus are shrews, and rodent-borne SEOV can infect shrews.
Assuntos
Orthohantavírus/isolamento & purificação , Musaranhos/virologia , Animais , China , Reservatórios de Doenças , Feminino , Orthohantavírus/genética , Masculino , Filogenia , Roedores/virologia , ZoonosesRESUMO
Plastoquinone (PQ) and ubiquinone (UQ) are two important prenylquinones, functioning as electron transporters in the electron transport chain of oxygenic photosynthesis and the aerobic respiratory chain, respectively, and play indispensable roles in plant growth and development through participating in the biosynthesis and metabolism of important chemical compounds, acting as antioxidants, being involved in plant response to stress, and regulating gene expression and cell signal transduction. UQ, particularly UQ10, has also been widely used in people's life. It is effective in treating cardiovascular diseases, chronic gingivitis and periodontitis, and shows favorable impact on cancer treatment and human reproductive health. PQ and UQ are made up of an active benzoquinone ring attached to a polyisoprenoid side chain. Biosynthesis of PQ and UQ is very complicated with more than thirty five enzymes involved. Their synthetic pathways can be generally divided into two stages. The first stage leads to the biosynthesis of precursors of benzene quinone ring and prenyl side chain. The benzene quinone ring for UQ is synthesized from tyrosine or phenylalanine, whereas the ring for PQ is derived from tyrosine. The prenyl side chains of PQ and UQ are derived from glyceraldehyde 3-phosphate and pyruvate through the 2-C-methyl-D-erythritol 4-phosphate pathway and/or acetyl-CoA and acetoacetyl-CoA through the mevalonate pathway. The second stage includes the condensation of ring and side chain and subsequent modification. Homogentisate solanesyltransferase, 4-hydroxybenzoate polyprenyl diphosphate transferase and a series of benzene quinone ring modification enzymes are involved in this stage. PQ exists in plants, while UQ widely presents in plants, animals and microbes. Many enzymes and their encoding genes involved in PQ and UQ biosynthesis have been intensively studied recently. Metabolic engineering of UQ10 in plants, such as rice and tobacco, has also been tested. In this review, we summarize and discuss recent research progresses in the biosynthetic pathways of PQ and UQ and enzymes and their encoding genes involved in side chain elongation and in the second stage of PQ and UQ biosynthesis. Physiological functions of PQ and UQ played in plants as well as the practical application and metabolic engineering of PQ and UQ are also included.
RESUMO
Poly(2-(methacryloyloxy)ethyltrimethyl ammonium chloride) (PMATAC) modified magnetic nanoparticles (NPs) with a high zeta potential of ca. 50mV were synthesized by atom transfer radical polymerization (ATRP). The prepared NPs consist of a magnetic core around 13nm and a PMATAC shell around 20nm attached on the surface of magnetic nanoparticles. Thermodynamic binding parameters between ß-lactoglobulin and these polycationic NPs were investigated at different ionic strengths by high-resolution turbidimetry, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC). Both turbidity and ITC show that binding affinities for BLG display a non-monotonic ionic strength dependence trend and a maximum appears at ionic strength of 50mM. Such observation should arise from the coeffects of protein charge anisotropy visualized by DelPhi electrostatic modeling and the strong electrostatic repulsion among highly charged NPs at a variety of ionic strengths.