Monodisperse Suspensions Research Articles

Polydisperse Versus Monodisperse Microbubbles: A Simulation Study for Contrast-Enhanced Ultrasound Imaging

ObjectiveContrast-enhanced ultrasound (CEUS) presents distinct advantages in diagnostic echography. Utilizing microbubbles (MBs) as conventional contrast agents enhances vascular visualization and organ perfusion, facilitating real-time, non-invasive procedures. There is a current tendency to replace traditional polydisperse MBs with novel monodisperse formulations in an attempt to optimize contrast enhancement and guarantee consistent behavior and reliable imaging outcomes. This study investigates the contrast enhancement achieved using various-sized monodisperse MBs and their influence on non-linear imaging artifacts observed in traditional CEUS. MethodsTo explore the differences between monodisperse and polydisperse populations without excessive experimentation, numerical simulations are employed for delivering precise, objective and expeditious results. The iterative non-linear contrast source (INCS) method has previously demonstrated efficacy when simulating ultrasound propagation in large populations in which each bubble has individual properties and several orders of multiple scattering are significant. Therefore, this method is employed to realistically simulate both monodisperse and polydisperse MBs. ResultsOur findings in CEUS imaging indicate that scattering from resonant monodisperse MBs is 11.8 dB stronger than scattering from polydisperse MBs. Furthermore, the amplitude of non-linear imaging artifacts downstream of the monodisperse population is 19.4 dB stronger compared with polydisperse suspension. ConclusionInvestigating the impact of multiple scattering on polydisperse populations compared with various monodisperse suspensions has revealed that monodisperse MBs are more effective contrast agents, especially when at resonance. Despite the strong signal-to-noise ratio of monodisperse populations, imaging artifacts caused by non-linear wave propagation are also enhanced, resulting in further mis-classification of MBs as tissue.

Brownian dynamics simulation of the structural evolution in monodisperse hard-sphere suspensions during drying and sedimentation processes.

The drying behavior of monodisperse colloidal films, with a focus on the influence of process variables on film microstructures, is explored via Brownian dynamics (BD) simulations. In our model, hard-sphere colloidal particles are dispersed in a Newtonian liquid with an initial particle volume fraction of 0.1. The effects of the drying rate and sedimentation on the evolving microstructures are systematically investigated using two dimensionless numbers: the Péclet number (Pe), which represents the competition between evaporation and diffusion, and the sedimentation number (Ns), which reflects the relative influence of sedimentation on evaporation. First, we analyze the local particle volume fraction and film structure at various Pe and Ns. As Pe increases, particle accumulation occurs near the liquid-gas interface, whereas a high Ns promotes dense packing near the substrate owing to sedimentation. The BD simulation results, viz. the local volume fraction profiles and drying regime maps, are in good agreement with those of the continuum model proposed by Wang and Brady. Structural analysis of the dried films reveals that at a low Pe (Pe = 0.1), a face-centered cubic (FCC) structure dominates, primarily independent of the sedimentation effects. In contrast, a high Pe leads to hexagonal close-packed or amorphous structure formation. Notably, at intermediate drying rates (Pe = 10), an increase in Ns promotes additional FCC ordering in the final film structure. Our study provides new insights into the hitherto underexplored role of sedimentation in the structural evolution of drying colloidal films, revealing the mechanisms of drying-induced assembly in colloidal systems.

Influence of concentration on thermophoresis of spherical aerosol particles within a Brinkman medium

Abstract We are examining the thermophoretic movement of a uniform mixture of spherical aerosol particles, all with the same properties, as they are situated within a porous material. These particles can have various thermal conductivity and surface characteristics. This analysis focuses on situations where the Péclet and Reynolds numbers are small. The influence of particle interactions is carefully considered by using a unit cell model, a well-established method known for its accurate predictions in the context of sedimentation for monodisperse suspensions of spherical particles. The porous medium is represented as a Brinkman fluid characterized by a Darcy permeability, which can be determined directly from experimental observations. This medium is considered to be uniform and isotropic, and the solid matrix is in thermal equilibrium with the fluid flowing through the voids of the medium. The Knudsen number is assumed to be low, enabling the description of fluid flow through the porous medium using a continuum model that includes temperature jump, thermal creep, frictional slip, and thermal stress slip at the aerosol particle’s surface. The conservation equations for energy and momentum are individually tackled within each cell. In this model, each cell represents a spherical particle enclosed by a concentric shell of surrounding fluid. The thermophoretic particle migration velocity is determined across different cases. We derive analytical expressions for this average particle velocity, expressing it in terms of the particle volume fraction. It is observed that different cell models yield somewhat varied results for particle velocity. Generally, with a fixed permeability parameter characterizing the porous medium, an increase in the thermal stress slip coefficient tends to decrease the normalized thermophoretic velocity across the different cell models. The results are in good agreement with the available data as documented in the existing literature. Additionally, a parallel examination of aerosol sphere sedimentation is provided.

The manufacturing and characterization of pentamidine-loaded poly(lactic-co-glycolic acid) nanoparticles produced by microfluidic method

In recent years, special attention has been paid to the study of manufacturing processes that can precisely control the physicochemical properties of nanoparticles (NPs) and reduce batch-to-batch variability. Microfluidics has recently emerged as an advanced production method that can manage NP properties by monitoring the diffusion/emulsification mechanism. Pentamidine free base (PTM-B), a diamidine compound positively charged at physiological pH, has already been used as a model drug for incorporation into poly(lactic-co-glycolic acid) (PLGA) via an ion-pairing strategy using a conventional bulk production method. The same formulation was chosen to study the scaling-up process and preparation using the microfluidic technique. The formulation of PLGA NP loaded with PTM-B by the microfluidic technique was optimized by adding 1 % Lutrol F68 as a surfactant agent to stabilize the nanosuspension during the solvent diffusion in the microchannel of the chip, and then, washed away in the final suspension. A thorough investigation of process parameters (i.e., total flow rate, flow rate ratio) was conducted to obtain a monodisperse suspension characterized by a mean diameter of less than 150 nm. In addition, in vitro studies on mammalian cancer cell lines demonstrated the potential antitumor activity of PTM-B-loaded NPs prepared by the microfluidic technique.

Effect of surfactants on the degree of polydispersity of a suspension of polystyrene latex spheres

The problem of satisfying the needs of the domestic market of the Russian Federation for creating domestic particle size standard reference materials in liquids to ensure uniformity in measurements of the granulometric composition of aerosols and powdery substances is considered. It is known that, under various conditions, monodisperse suspensions of polystyrene latex spheres can be synthesized, both monodisperse and polydisperse samples being obtainable. The effect of the composition and solubility of surfactants in a styrene-based water emulsion on the particle size of suspensions obtained as a result of emulsion polymerization, and their polydispersity, has been investigated. The metrological characteristics of polystyrene suspensions based on sodium, potassium, and lithium laureths synthesized in this study were determined using dynamic light scattering and laser diffraction techniques. It has been found that the size and degree of polydispersity of particles in suspensions based on lauric acid salts is primarily influenced by the solubility of the surfactant and the surface tension of the interfacial layer formed between styrene and water at the time of particle formation. The effect of the rate of reaction, as well as the concentration of surfactants, on the size and polydispersity of the synthesized particles, has been studied. It has been found that when potassium persulfate is used as the initiator in the reaction, particle size distributions are monodisperse for suspensions based on sodium or potassium laureate. The polydispersity degree of lithium laureate-based suspensions is approximately 1.5 to 2 times higher compared to other suspension samples. When azoisobutyronitrile is used as an initiator, all suspensions samples are monodisperse. It has been experimentally determined that the achievement of monodisperse samples is due to the polymer-monomer particle formation time, which is comparable to the monomer transformation rate. The results obtained will be utilized in the development and establishment of particle size standard reference materials for storage and reproduction of particle size values within a liquid medium.

Wavenumber-dependent dynamic light scattering optical coherence tomography measurements of collective and self-diffusion

We demonstrate wavenumber-dependent DLS-OCT measurements of collective and self-diffusion coefficients in concentrated silica suspensions across a broad q-range, utilizing a custom home-built OCT system. Depending on the sample polydispersity, either the collective or self-diffusion is measured. The measured collective-diffusion coefficient shows excellent agreement with hard-sphere theory and serves as an effective tool for accurately determining particle sizes. We employ the decoupling approximation for simultaneously measuring collective and self-diffusion coefficients, even in sufficiently monodisperse suspensions, using a high-speed Thorlabs OCT system. This enables particle size and volume fraction determination without the necessity of wavenumber-dependent measurements. We derive a relationship between the particle number-based polydispersity index and the ratio of self and collective mode amplitudes in the autocorrelation function and utilize it to measure the particle number-based polydispersity index. Notably, the polydispersity determined in this manner demonstrates improved sensitivity to smaller particle sizes compared to the standard intensity-based DLS cumulant analysis performed on dilute samples.

Structural and dynamical equilibrium properties of hard board-like particles in parallel confinement.

We performed Monte Carlo and dynamic Monte Carlo simulations to model the diffusion of monodispersed suspensions composed of impenetrable cuboidal particles, specifically hard board-like particles (HBPs), in the presence of parallel hard walls. The impact of the walls was investigated by adjusting the size of the simulation box while maintaining constant packing fractions, fixed at η = 0.150, for systems consisting of HBPs with prolate, dual-shaped, and oblate geometries. We observed that increasing the distance between the walls led to the recovery of an isotropic bulk phase, while local particle organization near the walls remained stable. Due to their shape, oblate HBPs exhibit more efficient anchoring at wall surfaces compared to prolate shapes. The formation of nematic-like particle assemblies near the walls, confirmed by theoretical calculations based on density functional theory, significantly influenced local particle dynamics. This effect was particularly pronounced to the extent that a modest portion of cuboids near the walls tended to diffuse exclusively in planes parallel to the confinement, even more efficiently than observed in the bulk regions.

Growth and static stability of bubble clouds in yield stress fluids

This study explores the growth and static stability of bubble clouds in yield-stress fluids using an experimental approach. Carbopol gels with varying concentrations and initial gas contents as well as Laponite gels are used as model yield stress fluids in our experiments. A vacuum system is exploited to generate the bubbles and control their growth in the gels. The focus of this study is on determining the maximum gas concentration which could be held trapped in the system and the critical yield number, i.e. the ratio of the yield stress to the buoyancy stress at the onset of motion. Our findings demonstrate the effect of the bubbles proximity as well as the gel structure and rheology on both the maximum gas concentration and critical yield number. Our results confirm that for higher gas fractions, the critical yield number is larger. Also, they show that the size and degree of elongation of the bubbles at the onset of motion are controlled by their proximity as well as the gel rheology. Moreover, our results reveal two different scenarios for the bubble release depending on the uniformity of the structure of the gel. In the case of low concentration Carbopol gels, characterized by uniform structures, quasi mono-dispersed bubble suspensions are formed. At a pretty high gas concentration, this might lead to a bubble cloud burst upon static instability onset. Conversely, in the case of high concentration Carbopol gels or Laponite gels, the polydisperse bubble suspensions emerge and the bubble release occurs gradually rather than suddenly. It can be associated with the heterogeneous structure of these gels stemming from their significant shear history dependence.

Facet-dependent dispersion and aggregation of aqueous hematite nanoparticles.

Nanoparticle aggregates in solution controls surface reactivity and function. Complete dispersion often requires additive sorbents to impart a net repulsive interaction between particles. Facet engineering of nanocrystals offers an alternative approach to produce monodisperse suspensions simply based on facet-specific interaction with solvent molecules. Here, we measure the dispersion/aggregation of three morphologies of hematite (α-Fe2O3) nanoparticles in varied aqueous solutions using ex situ electron microscopy and in situ small-angle x-ray scattering. We demonstrate a unique tendency of (104) hematite nanoparticles to maintain a monodisperse state across a wide range of solution conditions not observed with (001)- and (116)-dominated particles. Density functional theory calculations reveal an inert, densely hydrogen-bonded first water layer on the (104) facet that favors interparticle dispersion. Results validate the notion that nanoparticle dispersions can be controlled through morphology for specific solvents, which may help in the development of various nanoparticle applications that rely on their interfacial area to be highly accessible in stable suspensions.

Improving the novel white coconut oil-based metalworking fluid using nano particles for minimum surface roughness and tool tip temperature

At present, nearly 85 % all of the requirement for MWFs are satisfied by the use of mixtures of petroleum by-products and synthetic substances with supplementary additives to enhance their properties. The demand for easily biodegradable, environmental friendly MWFs is a current requirement. COCOTP, a novel biodegradable MWF based on white (refined) coconut oil, developed by authors, had previously shown promising tribological properties for machining mild steel (MS) and stainless steel (SS) when used with the flooding method, but had fallen short of the performance of commercially available, non-biodegradable alternatives with MQL. Therefore in the current investigation, nano-particles were added to improve the performance of novel COCOTP MWF to use it with MQL conditions. Two nanomaterials nano-graphite and nano-Al2O3 were separately added to the base fluid in different concentrations as a monodispersed suspension. These nano enhanced fluids (NEFs) were subsequently used in straight turning experiments of two work materials AISI304 and SS400. Both the nano-enhanced fluids show convincing improvements over both COCOTP and mineral-oil based fluids in terms of surface roughness of the specimens regardless of the material being turned. However when machining SS 400, NEFs perform better only in lower speeds in terms of temperature. SS400 has a much higher thermal conductivity than AISI304 means that the quantity of residual heat remaining at the point of material removal which can be absorbed by the cutting fluid is lower in SS400. During machining SS400 under MQL lubrication 9.8 %, 26.8 % and 24 % reduction of surface roughness values (with respect to soluble oil) and during machining AISI304 55.3 %, 73.7 % and 70.4 % reduction of surface roughness values were obtained at 1175 rpm with COCOTP, NEF A and NEF G respectively. Based on the experimental results, the best-performing nano-enhanced fluids under MQL are 0.3 % (w/w) Al2O3 and 0.3 % (w/w) graphite.

A self-cleaning micro-fluidic chip biospired by the filtering system of manta rays.

Size-based particle filtration has become indispensable in numerous biomedical and environmental applications. In this study, bioinspired by the filter-feeding mechanism (lobe filtration) of manta rays, we designed a U-shaped biomimetic gill rake filter that combined lobe filtration and Dean flow to filter monodisperse suspensions, bi-disperse suspensions and yeast cells. Compared with other equipment using the inertial focusing technology, our equipment can perform high-throughput (up to 8 mL min-1) and high-efficiency filtration of particles (maximum filtration efficiencies of 96.08% and 97.14% for 10 and 15 μm monodisperse suspensions at the optimum flow rate of 6 mL min-1). The complex velocity field of the micro-fluidic flow within the filter is numerically simulated, and in combination with experiments, a threshold for the flow rate is identified. When the inlet flow rate exceeds the threshold value, the efficiency of particle filtration is increased rapidly. Afterwards, by analysing the filtration mechanism, we develop three novel filtration processes. The equilibrium positions of the particles and yeast cells in the main channel are close to the outer wall at high flow rate, which diminishes the likelihood of particles and yeast cells entering the side channel. This configuration establishes a self-cleaning mechanism, ensuring prolonged and efficient operation of the filter with high-throughput processing. Furthermore, the influence of the filter lobe angle and channel width on the filtration efficiency and outlet flow rate ratio are explored, and an optimisation plan is prepared.

Dip coating of shear-thinning particulate suspensions.

Dip coating a planar substrate with a suspension of particles in a shear-thinning liquid will entrain particles in the liquid film, facilitating filtration and sorting of particles. Experiments were performed for both monodisperse and bidisperse particle suspensions of shear-thinning Xanthan Gum solutions. Particle entrainment occurs when the coating thickness at the stagnation point of the thin film flow is larger than the particle diameter. A model is developed to predict the entrainment criteria using lubrication theory applied to an Ostwald power-law fluid which yields a modified Landau-Levich-Derjaguin (LLD) law governing the coating film thickness that depends upon a properly defined capillary number Ca. The critical withdrawal velocity for particle entrainment depends upon the particle size and fluid rheology through a relationship between Ca and the bond number Bo, which agrees well with our model predictions and prior experimental results of A. Sauret et al. Phys. Rev. Fluids, 2019, 4, 054303 for the limiting case of Newtonian suspensions. Single particle entrainment and particle clustering is observed for monodisperse suspensions, which depends on Ca and the particle volume fraction ϕ. In bidisperse suspensions, particle sorting can occur whereby only the smaller particles are entrained in the film over an active filtration range of Ca and Bo, which also agrees well with our model predictions.

Characterizing jamming of dilute and semi-dilute fiber suspensions in a sudden contraction and a T-junction

The clogging or jamming of particle suspensions is a ubiquitous problem, hindering the efficiency of particle–liquid and particle–particle separations. Motivated by pressure screening in the pulp and paper industry, we characterize jamming of dilute and semi-dilute mono-disperse rigid-rod suspensions passing through channels mimicking dead-end and cross-flow filtration membranes, experimentally, using particle-tracking velocimetry. We observe that jams nucleate by either bridging of isolated particles across the constriction, or by localized mechanical entanglement of the particles, i.e., flocculation. Uniquely, we observe floc-formation during acceleration into the aperture and report this as primary mechanism for jamming events. We characterized the accumulation-release cycles of the jamming event using an exponential probability distribution; this distribution is indicative of a Poisson process. For jams nucleated by single-particle bridging, the distribution is (primarily) related to the number of fibers passing through the aperture; this is similar to dry, granular materials. For floc-based nucleation events, the distribution is (primarily) related to the suspension concentration with the average time between jams decreasing inversely with the square-root of the initial suspension concentration. For the conditions tested, the distribution was insensitive to changes in constriction geometry.

The second shear-thinning and strain-stiffening behaviors of bidisperse non-colloidal suspensions

Experimental research is done to determine the shear-thinning behavior of a bidisperse non-colloidal suspension under steady-state shear and the strain-stiffening behavior under oscillatory shear. The second shear-thinning behavior is displayed when the volume fraction of the bidisperse particle suspension is between medium and high. It exhibits with an increase in shear rate, the viscosity drops by approximately three orders of magnitude. At low shear rates, a strong particle size dependence of viscosity is observed, while at high shear rates, the particle size dependence is almost non-existent. To further understand the behavior of the second shear thinning, three sets of oscillatory shear tests and steady-state shear tests (constant shear rate) are carried out at three stopping points in parallel using a unique experimental technique we have developed. The values of modulus and viscosity at the third position are significantly smaller than those at the first and second positions. In the oscillatory shear test, the storage and loss moduli of the bidisperse suspension first decrease and then increase as the strain amplitude increases. The particle volume fraction, not the particle size, is closely related to the bidisperse critical strain amplitude. Compared with monodisperse suspension, bidisperse suspension has low viscosity and larger modulus well under steady-state shear and oscillatory shear operations, which is beneficial to the development of new materials and processes. Moreover, by adding a surfactant of a specific concentration to the bidisperse sample, it is proved that the change in the microstructure of the suspension particle is responsible for the rheological properties of the suspension.

Dip coating of viscous granular suspensions

A solid substrate withdrawn from a liquid bath is coated with a uniform thickness given by the Landau–Levich–Derjaguin (LLD) law. If the bath is a suspension of neutrally buoyant particles, the liquid coating can entrain particles in a process known as capillary filtration that only depends on the capillary number Ca. Experiments were performed using a custom-built dip coating apparatus and gravimetry techniques. The working liquids were monodisperse and bidisperse suspensions with larger particle diameters and higher liquid viscosity than previously reported. The single particle entrainment point for monodisperse suspensions agrees well with the critical capillary number predicted in prior literature. Bidisperse suspensions exhibit active filtration regions where only the smallest particles are entrained with the range of Ca for active filtration consistent with reported models. These experimental results both validate and enhance our understanding of capillary filtration by exploring larger particle-sized granular suspensions of higher viscosity solutions, as relevant to applications in construction, medical care, personal care products, and food science.

Clogging and permeability reduction dynamics in porous media: A numerical simulation study

The dynamics of fine particle entrainment, transport, and deposition within pore systems, and in particular, the capacity for mobile fines to impair permeability within porous media is critical in many industrial applications. Considerable effort has been expended over the past several decades to identify and parametrize the governing factors that control permeability reduction, with studies employing a combination of physical experimentation and numerical simulation toward this aim. The objective of this work was to numerically investigate the impact of pore space geometry and fine sizes on the clogging dynamics of porous media. The clogging dynamics were characterized by the length of clogging zone (LCZ), the critical throat size of clogging (CTZC), the clogged fraction of throats (CFT), and the permeability reduction (PR). We implemented a computational fluid dynamics-discrete element method (CFD-DEM) numerical framework with a four-way coupling scheme to obtain insights into throat clogging and permeability reduction within heterogeneous porous media utilizing four different monodisperse suspensions. Geometries of porous media were extracted from 3D images of sand packs obtained using micro-computed tomography. The geometries had porosity values ranging from 0.35 to 0.57 and initial permeabilities between 1.35 and 26.32 μm2. CFD-DEM simulations were performed on each geometry four times, varying the injected fine particle size from 5 to 15 μm diameters. Findings indicate that pore systems with tortuosity <1.28 and angles of solid grains orientation larger than 46o tend to have shorter length clogging zones and greater permeability reduction. Furthermore, although systems with porosities higher than 0.48 tend to have a relatively high clogged fraction of throats, they undergo lower permeability reduction. It was also observed that within the studied pore systems, injection of fine particles larger than 7 μm into systems with aspect ratios higher than 2.5, results in a lower fraction of clogged throats. Additionally, for the studied pore networks,< 7 μm fine particles injected into porous media with a large pore body (> 66 μm) and throat (> 22 μm) radii tended to result in larger clogging zones and a greater critical throat size of clogging.

In-vitro modeling of intravenous drug precipitation by the optical spatial precipitation analyzer (OSPREY)

Intravenous (IV) administration of poorly water-soluble small molecule therapeutics can lead to precipitation during mixing with blood. This can limit characterization of pharmacological and safety endpoints in preclinical models. Most often, tests of kinetic and thermodynamic solubility are used to optimize the formulation for solubility prior to infusion in animals, but these do not capture the dynamic precipitation processes that take place during in-vivo administration. To better capture the fluid dynamic processes that occur during IV administration, we developed the Optical Spatial PREcipitation analYzer (OSPREY) as a method to quantify the amount and size of compound precipitates in whole blood using a flow-through system that mimics IV administration. Here, we describe the OSPREY device and its underlying imaging processing methods. We then validate the ability to accurately segment particles according to their size using monodisperse suspensions of microspheres (diameter 50 to 425 µm). Next, we use a tool compound, ABT-737, to study the effects of compound concentration, vessel flow rate, compound infusion rate and vessel diameter on precipitation. Finally, we use the physiological diameter and flow rate of rat femoral vein and dog saphenous vein to demonstrate the potential of OSPREY to model in-vivo precipitation in a controlled, dynamic in-vitro assay.

Singularly narrow size distributions of 200 nm polystyrene latex spheres determined by high resolution mobility analysis

A high-resolution differential mobility analyzer (DMA) is used for the first time to study the mobility distribution of Polystyrene Latex (PSL) particles. We investigate in particular some unique, nominally 200 nm and 100 nm PSL particles, known by other methods to be unusually monodisperse. The suspensions are electrosprayed after adding ammonium acetate to a concentration of 10 mmol/L. Mobility analysis is carried out after charge reduction with a second electrospray of the opposite polarity. The 200 nm particles typically produce two narrow peaks, with relative intensities that depend on electrospray parameters. Under the most favorable spraying conditions achieved, the more mobile peak becomes dominant, is narrowest, and has a repeatable mobility; we attribute it provisionally to the unpolluted suspended particles. The less mobile peaks are substantially more variable but never entirely removed. We initially attributed them to attachment of involatile solutes in the suspension to the atomized PSL particles; however, this hypothesis is put in doubt by later observations. The measured relative width of the mobility distribution for the most mobile peak is FWHMZ = (1.65 ± 0.08) %. This translates into a width for the diameter distribution FWHMd = (1.09 ± 0.05) % or standard deviation σd = (0.46 ± 0.02) %, by far the most monodisperse polymeric submicron particle suspension so far reported. Concentrations of ammonium acetate of 100 mmol/L and 40 mmol/L were also tested in order to reduce residue attachment by forming smaller initial electrosprayed drops. These higher salinities, however, led to capillary clogging, apparently because the narrow electrospraying jet precludes the passage of the PSL particles. The 100 nm particles gave a wider variation in mean diameter and size distribution depending on electrospraying parameters, perhaps because of the suspension's considerably larger content of involatile solutes. Unlike the 200 nm particles, no spraying condition was found under which a precisely repeatable size distribution could be achieved for the 100 nm particles. However, the data do point to an estimated upper bound on the size distribution width of FWHMd ≈ 3 % (σd ≈ 1.3 %), which is uniquely narrow for particles of this size.

Ground State Configurations and Metastable Phases of Charged Linear Rods.

This computational study investigates the energy minimum, that is, ground state, of suspensions of monodisperse (single-component) charged linear rods at various densities and screening lengths. We find that closed-packed unidirectional configurations have the lowest energies for all studied cases. We further specify the lattice parameters for these crystalline structures. In addition, we identify a few metastable phases, including heliconical structures. These metastable heliconical phases are composed of hexagonal smectic C layers with particle orientations forming a conical helicoid with a short pitch of three layers. We evidence this by zero-temperature Monte Carlo simulations starting from an energy-minimized hexagonal cholesteric configuration, which rapidly transforms to a heliconical phase. Furthermore, this heliconical phase is remarkably stable even at finite temperatures and melts to a disordered phase at high temperatures. Finally, we conduct simulations at room temperature and conditions typical for cellulose nanocrystal suspensions to study the onset of nematic order and compare our results to available experimental data. Our findings suggest that electrostatics play an important role in the isotropic/anisotropic transition for dense suspensions of charged rods.

Enhanced treatment in cutaneous dermatophytosis management by Zataria multiflora-loaded nanostructured lipid carrier topical gel: A randomized double-blind placebo-controlled clinical trial

The global rising incidence of skin mycosis especially dermatophytes currently affects more than 20–25% of the world population. It is believed that nanotechnology can aid in the efficient treatment of this skin disease. The present study, therefore, aimed to employ nanostructured lipid carriers (NLCs) in a gel formulation for a more effective delivery of Zataria multiflora (ZM) essential oils through the skin to manage mild to moderate cutaneous dermatophytosis. Zataria multiflora-loaded nanostructure lipid carriers (ZM-NLCs) were prepared and optimized by utilizing an ultrasonic probe approach and formulated the ZM-NLCs as a 1% w/w carbopol gel after confirming the NLCs-related characteristics. In vitro antifungal susceptibility testing was performed on 20 common dermatophyte species based on the CLSI M38-A3 guidelines. A total of 80 volunteers (40 volunteers from each gender, equally divided into two groups: ZM-NLCs gel and placebo receivers) participated in this clinical randomized, double-blind placebo-controlled study. Clinical manifestations (itching, scaling, size of lesion and inflammation), as well as mycological findings such as KOH-direct examination test and culture, were evaluated after 2 and 4 weeks of topical application. Molecular identification of the strains isolated from the patient's lesions was also performed to the species level using a PCR-RFLP method. A mono-dispersed suspension of spherical nanoparticles with zeta potential, Z-average and PDI index of −26.6 ± 7.7 mV, 273.5 ± 4 nm and 0.33 ± 0.03, respectively was achieved with no cytotoxicity. Apart from the significant inhibitory effect of ZM-NLCs on fungal growth, the application of the ZM-NLCs gel resulted in an effective diminution in inflammation (87.5%), itching (90%) and scaling (95%) among the volunteers after 4 weeks. The aforementioned signs/symptoms were significant when compared to the patients receiving a placebo (p < 0.005). A reduction/disappearance of the lesion was also significantly reported in the ZM-NLCs gel receivers. Compared with placebo receivers, meaningful negative results for both direct examination and culture were observed (17.5% vs 70% for KOH-direct examination and 12.5% vs 57.5% for culture) for patients who received ZM-NLCs gel after 2 weeks of prescription. PCR-RFLP outputs revealed T. mentagrophytes/interdigitale complex as the predominant isolated species from cutaneous lesions. In conclusion, Zataria multiflora-NLCs gel application displayed a more rapid cure time with no adverse side effects compared to placebo demonstrating the efficacious nature of NLCs.