Polyunsaturated fatty acid-derived lipid mediator Resolvin D1 alleviates sepsis-induced disseminated intravascular coagulation via Caspase-1/Gasdermin D pyroptotic pathway.

BACKGROUND & AIMS: Sepsis-induced disseminated intravascular coagulation (DIC) is characterised by abnormal blood clotting resulting from severe infection, contributing to organ dysfunction in sepsis. Resolvin D1 (RvD1) is an endogenous lipid mediator, synthesised from the omega-3 polyunsaturated fatty acid (PUFA) docosahexaenoic acid (DHA) through enzymatic processes involving 15-LOX and 5-LOX. RvD1 is recognised for its protective properties against various inflammatory conditions. This study aims to investigate its potential to modulate coagulation dysfunction in sepsis and to evaluate coagulation disorders in septic patients. METHODS: Sepsis models were established by intraperitoneal injection LPS (20 mg/kg) or cecal ligation and puncture (CLP) followed by injection of RvD1 (10 µg/kg) or saline. The impact of RvD1 on coagulation dysfunction was assessed by clotting time and coagulation indicators such as TAT, D-dimer, PAI-1, and fibrinogen. The activity of the coagulation system in vivo was observed by evaluating dynamic microcirculation, platelets and thrombin in mice using intravital microscopy. The effect of RvD1 on pyroptosis was investigated by measuring NOD-like receptor protein 3 (NLRP3), Caspase-1, Caspase-11, and Gasdermin D (GSDMD) levels via western blot. Caspase-1 knockout mice, GSDMD knockout mice and bone marrow-derived macrophages (BMDMs) were used to elucidate the underlying mechanisms. Lastly, the concentration of RvD1 in plasma from septic patients was quantified to explore its relationship with coagulation and pyroptosis. RESULTS: RvD1 significantly attenuated coagulation dysfunction in septic mice induced by LPS and CLP, and inhibited Caspase-1/GSDMD-dependent pyroptosis in septic mice and bone marrow-derived macrophages. In septic patients, the plasma concentrations of RvD1 was negatively correlated with both coagulation-related indicators and markers of GSDMD activation. CONCLUSION: The results suggest that RvD1 can improve coagulation dysfunction in sepsis by regulating the Caspase-1/GSDMD pyroptotic pathway. Additionally, the concentration of RvD1 in septic patient plasma is related to prognosis and DIC development. RvD1 could be a potential biomarker and a promising therapeutic alternative in sepsis-induced DIC.

Metal telluride nanosheets by scalable solid lithiation and exfoliation.

Transition metal tellurides (TMTs) have been ideal materials for exploring exotic properties in condensed-matter physics, chemistry and materials science1-3. Although TMT nanosheets have been produced by top-down exfoliation, their scale is below the gram level and requires a long processing time, restricting their effective application from laboratory to market4-8. We report the fast and scalable synthesis of a wide variety of MTe2 (M = Nb, Mo, W, Ta, Ti) nanosheets by the solid lithiation of bulk MTe2 within 10 min and their subsequent hydrolysis within seconds. Using NbTe2 as a representative, we produced more than a hundred grams (108 g) of NbTe2 nanosheets with 3.2 nm mean thickness, 6.2 µm mean lateral size and a high yield (>80%). Several interesting quantum phenomena, such as quantum oscillations and giant magnetoresistance, were observed that are generally restricted to highly crystalline MTe2 nanosheets. The TMT nanosheets also perform well as electrocatalysts for lithium-oxygen batteries and electrodes for microsupercapacitors (MSCs). Moreover, this synthesis method is efficient for preparing alloyed telluride, selenide and sulfide nanosheets. Our work opens new opportunities for the universal and scalable synthesis of TMT nanosheets for exploring new quantum phenomena, potential applications and commercialization.

RvD1 improves resident alveolar macrophage self-renewal via the ALX/MAPK14/S100A8/A9 pathway in acute respiratory distress syndrome.

INTRODUCTION: Acute respiratory distress syndrome (ARDS) is a pulmonary inflammatory process primarily caused by sepsis. The resolution of inflammation is an active process involving the endogenous biosynthesis of specialized pro-resolving mediators, including resolvin D1 (RvD1). Resident alveolar macrophages (RAMs) maintain pulmonary homeostasis and play a key role in the resolution phase. However, the role of RAMs in promoting the resolution of inflammation by RvD1 is unclear. OBJECTIVES: Here, we investigated the mechanisms of RvD1 on regulating RAMs to promote the resolution of ARDS. METHODS: Mice were administered lipopolysaccharide and/or Escherichia coli via aerosol inhalation to establish a self-limited ARDS model. Then, RvD1 was administered at the peak inflammatory response. RAMs self-renewal was measured by flow cytometry, RAM phagocytosis was measured by two-photon fluorescence imaging. In addition, plasma was collected from intensive care unit patients on days 0-2, 3-5, and 6-9 to measure RvD1 and S100A8/A9 levels using triple quadrupole/linear ion trap mass spectrometry. RESULTS: RAMs were found to play a pivotal role in resolving inflammation during ARDS, and RvD1 enhanced RAM proliferation and phagocytosis, which was abrogated by a lipoxin A4 receptor (ALX, RvD1 receptor) inhibitor. Both primary RAMs transfected with rS100A8/A9 and/or S100A8/A9 siRNA and S100A9-/- mice (also deficient in S100A8 function) showed higher turnover and phagocytic function, indicating that RvD1 exerted its effects on RAMs by inhibiting S100A8/A9 production in the resolution phase. RvD1 reduced S100A8/A9 and its upstream MAPK14 levels in vivo and in vitro. Finally, in the patients, RvD1 levels were lower, but S100A8/A9 levels were higher. CONCLUSIONS: We propose that RvD1 improved RAM self-renewal and phagocytosis via the ALX/MAPK14/S100A8/A9 signaling pathway. Plasma RvD1 and S100A8/A9 levels were negatively correlated, and associated with the outcome of sepsis-induced ARDS.

CLINICAL VALUE OF SYNDECAN-1 LEVELS IN TRAUMA BRAIN INJURY: A META-ANALYSIS.

ABSTRACT: Background: Traumatic brain injury (TBI) is a head trauma usually associated with death and endothelial glycocalyx damage. Syndecan-1 (SDC-1)-a biomarker of glycocalyx degradation-has rarely been reported in meta-analyses to determine the clinical prognostic value in TBI patients. Methods: We looked into PubMed, EMBASE, Cochrane Library, and Web of Science databases from January 1, 1990, to May 1, 2023, to identify eligible studies. A meta-analysis was conducted using RevMan 5.4 and Stata 16.0 with the search terms "SDC-1" and "traumatic brain injury." Results: The present study included five studies with a total of 640 enrolled patients included. Syndecan-1 concentrations were higher in the isotrauma TBI group than in the non-TBI group (standardized mean difference [SMD] = 0.52; 95% CI: 0.03-1.00; P = 0.04). Subgroup analysis revealed statistical significance when comparing the SDC-1 level of multitrauma TBI (TBI + other injuries) group with the isotrauma TBI group (SMD = 0.74; 95% CI: 0.42-1.05; P < 0.001), and the SDC-1 level of the TBI coagulopathy (+) group (TBI with early coagulopathy) with the TBI coagulopathy (-) group (SMD = 1.75; 95% CI: 0.41-3.10; P = 0.01). Isotrauma TBI patients with higher SDC-1 level were at a higher risk of 30-day in-hospital mortality (odds ratio = 3.32; 95% CI: 1.67-6.60; P = 0.0006). Conclusion: This meta-analysis suggests that SDC-1 could be a biomarker of endotheliopathy and coagulopathy in TBI, as it was increased in isotrauma TBI patients and was higher in multitrauma TBI patients. There is a need for additional research into the use of SDC-1 as a prognostic biomarker in TBI, especially in isotrauma TBI patients.

Protocol for fabrication of Pt/RuO2/graphene bifunctional oxygen catalyst in Li-O2 batteries.

The commercial mass production of bifunctional oxygen catalysts with high activity and stability is critical for constructing high-performance lithium-oxygen (Li-O2) batteries, but remains challenging. Herein, we describe a protocol for the scalable fabrication of a 2D bifunctional electrocatalyst of Pt/RuO2/graphene by spatial confinement strategy and elaborately evaluate its oxygen reduction/evolution reactions for advanced Li-O2 batteries. We then detail the synthesis steps for preparing materials followed by assembly and evaluation of the three-electrode systems and coin-type Li-O2 batteries. For complete details on the use and execution of this protocol, please refer to Li et al. (2023).1.

Enhancing propellant performance through intermolecular interactions: cyclodextrin-based MOF loading in nitrocellulose.

Metal-organic frameworks (MOFs) offer promising opportunities for modifying energetic materials due to their micro-porous structure and high performance. In this study, we present a novel green MOF named cyclodextrin-MOF (CD-MOF), which incorporates potassium ions, synthesized using a simple methanol vapor diffusion approach. The CD-MOF incorporates potassium ions and enhances propellant performance through intermolecular force optimization with nitrocellulose (NC). Molecular dynamics simulations reveal stronger interactions between the CD-MOF and NC. The loading of the CD-MOF within NC forms a stable structure with resistance to migration and defense against crystalline precipitation and water absorption. Notably, in static combustion and pyrolysis tests, the CD-MOF exhibits efficient flame and flash inhibition. The thermal degradation and cauterization of the CD-MOF resulted in the formation of a complex microporous material capable of absorbing flammable and harmful gases such as CO, NO, NO2, and N2O. These findings shed light on the superior performance of the CD-MOF compared to conventional inorganic salts, and the comprehensive characterization and molecular simulations provide insights into the unique properties and applications of the CD-MOF, emphasizing its significant contribution to the field of green propellants.

Unraveling oxygen vacancy site mechanism of Rh-doped RuO2 catalyst for long-lasting acidic water oxidation.

Exploring durable electrocatalysts with high activity for oxygen evolution reaction (OER) in acidic media is of paramount importance for H2 production via polymer electrolyte membrane electrolyzers, yet it remains urgently challenging. Herein, we report a synergistic strategy of Rh doping and surface oxygen vacancies to precisely regulate unconventional OER reaction path via the Ru-O-Rh active sites of Rh-RuO2, simultaneously boosting intrinsic activity and stability. The stabilized low-valent catalyst exhibits a remarkable performance, with an overpotential of 161 mV at 10 mA cm-2 and activity retention of 99.2% exceeding 700 h at 50 mA cm-2. Quasi in situ/operando characterizations demonstrate the recurrence of reversible oxygen species under working potentials for enhanced activity and durability. It is theoretically revealed that Rh-RuO2 passes through a more optimal reaction path of lattice oxygen mediated mechanism-oxygen vacancy site mechanism induced by the synergistic interaction of defects and Ru-O-Rh active sites with the rate-determining step of *O formation, breaking the barrier limitation (*OOH) of the traditional adsorption evolution mechanism.

The role of closed-loop management of fever patients in a county-level medical community for the prevention and control of the post-coronavirus disease 2019 pandemic.

We built a closed-loop management model for patients with fever in a county-level medical community and explored the role of this model in post-coronavirus disease 2019 (COVID-19) epidemic prevention and control. The subjects included 83,791 patients with fever treated in designated hospitals between February 2020 and April 2021. A pre-hospital, in-hospital, and post-hospital management system for patients with fever in the county-level medical community was established to allow the closed-loop management of these patients. SPSS software (version 13.0) was used to analyze the methods of visiting the hospital, nucleic acid detection in the hospital, and location of the patients after the hospital visit. Chi-square tests were used to compare the methods of visiting and location after hospital visits between patients with and without an epidemiological history. The number of patients with fever in the fever clinic showed a logarithm change (R2 = 0.4710), accompanied by seasonal changes. The number of fever patients with an epidemiological history decreased logarithmically monthly (R2 = 0.8876). Among patients with fever, 99.64% sought medical treatment on their own, with relatively low proportions undergoing home quarantine and requiring centralized quarantine special vehicles. After visiting the fever clinics, 98.56% of patients isolated at home or were monitored, with small proportions of patients requiring hospital admission or centralized isolation. However, the proportions of patients with home and centralized isolation with epidemiology were relatively high, accounting for 20.55% and 27.40% of cases, respectively. Compared to the overall population of patients with fever, the difference was statistically significant (χ2 = 48.881, P = .000). The establishment of a closed-loop management model for patients with fever in a county-level medical community strengthened the management of these patients. No local cases occurred in Beilun District between March 2020 and April 2021. In the post-COVID-19 era, all medical institutions in the county-level medical community strengthened infectious disease pre-examination and triage and promoted the formation of a strategic pattern of initial diagnosis at the grassroots level, 2-way referral, upper and lower linkage, and joint epidemic prevention. This management was more conducive to COVID prevention and control by hierarchical management according to the presence or absence of an epidemiological history.

α-MnO2/MWCNTs as an electrocatalyst for rechargeable relatively closed system Li-O2 batteries.

Herein, a new, relatively closed system Li-O2 (RCLO) battery, without extra oxygen being involved in the reaction during the charge and discharge process, is reported. This relatively closed system effectively solves the key issue of poor circulation caused by oxygen generation in conventional Li-O2 batteries.

lncRNA FER1L4 is dysregulated in osteoarthritis and regulates IL-6 expression in human chondrocyte cells.

Osteoarthritis (OA) is the most prevalent joint disease and is one of the major causes of disability in the world. There has been an increase in the incidence of OA, which is associated with an aging population, sedentary lifestyle, and reduced physical activity. Due to the complex OA pathogenesis, there are limited diagnostic tools. OA is a degenerative joint disorder with a recognized inflammatory component, usually described as abnormal expression of inflammatory factors. For instance, interleukin 6 (IL-6) has been shown to be upregulated in serum and synovial fluid among patients with OA. Most of the inflammatory factors have been associated with the expression of long noncoding RNAs (lncRNAs). However, the role of the novel lncRNA Fer-1-like protein 4 (FER1L4) in OA is yet to be determined. Here, we interrogated the expression profile of FER1L4 in patients with OA to define its potential application as a diagnostic marker. We collected synovial fluid and blood samples from both OA cases and normal controls. Using qRT-PCR, we evaluated the expression of FER1L4 in plasma and synovial fluid. On the other hand, the expression of IL-6 in plasma and synovial fluid was assessed using ELISA. Besides, the effect of age, gender or disease stage in the expression of the FER1L4 in plasma was also estimated. Moreover, the receiver operating characteristic (ROC) curves were used to determine the impact of FER1L4 in OA cases compared with the normal controls. In addition, we analyzed the correlation between FER1L4 and IL-6 through Pearson correlation analysis. Also, IL-6 expression in overexpressed FER1L4 samples was detected in chondrocytes through western blot analysis, while FER1L4 expression following endogenous IL-6 exposure was detected by qRT-PCR. Our data showed that whereas lncRNA FER1L4 is downregulated in OA patients, IL-6 is upregulated. The plasma FER1L4 levels among the OA cases were suppressed with disease progression and old age, and the down-regulation could efficiently discriminate OA patients from normal subjects. In addition, upregulation of FER1L4 inhibited IL-6 expression in human chondrocyte cells, and treatment with different concentrations of exogenous IL-6 did not affect the expression of FER1L4. Taken together, our data demonstrates that FER1L4 could efficiently identify OA cases from normal subjects, and can also modulate the expression of IL-6 in human chondrocytes.

Combustion Performance of Spherical Propellants Deterred by Energetic Composite Deterring Agents.

In order to achieve ideal burning progressivity and reduce harmful phenomena such as muzzle flame and smoke, energetic composite deterring agents (ECDAs) deterring spherical propellants were designed and prepared. The combustion performance of ECDA-deterred propellants was characterized by a closed vessel, and the interior ballistic performance was studied by a ballistic gun. High-speed photography and a smoke box were employed to capture muzzle flames and smoke. The results showed that triethylene glycol dinitrate (TEGDN) had a slight deterring effect weaker than that of poly(neopentyl glycol adipate) (PNA) on the propellants. The maximum pressure in the closed vessel bore of the ECDA-deterred propellants was 2.29 MPa higher than that of the dibutyl phthalate (DBP)-deterred propellants, though the L-B curve of the ECDA-deterred propellants was slightly lower and its combustion time was 0.44 ms longer. For ECDA containing 5 wt % PNA and 3.2 wt % TEGDN, 80 °C and 150 min are the best deterring conditions. The average velocity of the bullet propelled by ECDA-deterred propellants was increased by 93.4 m·s-1, while the average maximum pressure in the gun bore was decreased by 19 MPa, compared with the original propellants. The muzzle flame and smoke of the ECDA-deterred propellants were significantly reduced compared with the DBP-deterred propellants, where the smoke concentration was reduced by up to 44.5%.

Theoretical Insights into the Structures and Capacitive Performances of Confined Ionic Liquids.

Room-temperature ionic liquids (RTILs) together with nano-porous electrodes are the most promising materials for supercapacitors and batteries. Many theoretical works have addressed the structures and performances of RTILs inside nanopores. However, only limited attention has been given to how the dispersion forces of RTILs influence the behavior of ions inside the slit pores. Toward this aim, we investigate the effects of various dispersion forces between ions on the macroscopic structures in nanoconfinement and the capacitance performance of supercapacitors by the classical density functional theory (CDFT). The results show that the dispersion force can significantly change the mechanism of the charging process and even the shape of differential capacitance curves. In addition, the voltage-dependent structures of RTILs with appropriate dispersion force appears in a given silt pore, which leads to extremely high capacitance and enhances the energy storage density. We hope that this work could further offer guidance for the optimizing of electrolytes for electrical double layer capacitors, like tuning the dispersion force between ions by adding/removing certain chemical groups on the cations and anions of RTILs.

Sulfhydration of perilipin 1 is involved in the inhibitory effects of cystathionine gamma lyase/hydrogen sulfide on adipocyte lipolysis.

Hydrogen sulfide (H2S) is a novel adipokine mediating glucose uptake, lipid storage and mobilization, thus contributing to the genesis of obesity and associated diseases. Our previous work demonstrated that H2S inhibited isoproterenol-stimulated lipolysis by reducing the phosphorylation of perilipin 1 (plin-1), a lipid-droplet protein blocking lipase access. How H2S modulates plin-1 phosphorylation is still unclear. Our present study found that an H2S donor slightly increased adipose tissue weight and reduced lipolysis in mice; by contrast, deleting the key H2S generation enzyme cystathionine gamma lyase (CSE) in adipocytes lowered adipose accumulation and enhanced lipolysis. Intriguingly, an H2S donor induced sulfhydration of plin-1 but not hormone-sensitive lipase, and CSE deletion abolished the post-translational modification of plin-1. During isoproterenol-stimulated lipolysis, plin-1 sulfhydration was associated with reduced phosphorylation, and removing sulfhydration by dithiothreitol recovered the phosphorylation. Finally, plin-1 knockout abolished the effect of H2S on lipolysis, which indicates that plin-1 sulfhydration is a major direct target of H2S in lipolysis. We have identified a new post-translation modification, sulfhydration (direct action by H2S) of plin-1, causing reduced phosphorylation then decreased lipolysis. This finding also highlights a novel molecular regulatory mechanism of lipolysis.

Size-dependent thermodynamic structural selection in colloidal crystallization.

Nucleation and growth of crystalline phases play an important role in a variety of physical phenomena, ranging from freezing of liquids to assembly of colloidal particles. Understanding these processes in the context of colloidal crystallization is of great importance for predicting and controlling the structures produced. In many systems, crystallites that nucleate have structures differing from those expected from bulk equilibrium thermodynamic considerations, and this is often attributed to kinetic effects. In this work, we consider the self-assembly of a binary mixture of colloids in two dimensions, which exhibits a structural transformation from a non-close-packed to a close-packed lattice during crystal growth. We show that this transformation is thermodynamically driven, resulting from size dependence of the relative free energy between the two structures. We demonstrate that structural selection can be entirely thermodynamic, in contrast to previously considered effects involving growth kinetics or interaction with the surrounding fluid phase.

Drug resistance from preferred antiretroviral regimens for HIV infection in South Africa: A modeling study.

BACKGROUND: Tenofovir-containing regimens comprise the preferred first-line antiretroviral therapy (ART) in many countries including South Africa, where utilization of second-line regimens is limited. Considerable HIV drug resistance has occurred among persons failing tenofovir-containing first-line ART. We evaluated drug resistance at the population level using mathematical modeling. SETTING: Heterosexual HIV epidemic in KwaZulu-Natal, South Africa. METHODS: We constructed a stochastic individual-based model and simulated scenarios of ART implementation, either CD4-based (threshold < 500 cells/mL) or Fast-track (81% coverage by 2020), with consideration of major drug-associated mutations (M184V, K65R and non-nucleoside reverse transcriptase inhibitor (NNRTI)). Using base case and uncertainty analyses, we assessed (majority) drug resistance levels. RESULTS: By 2030, the median total resistance (proportion of HIV-infected persons with drug resistance) is predicted to reach 31.4% (interquartile range (IQR): 16.5%-50.2%) with CD4-based ART, decreasing to 14.5% (IQR: 7.7%-25.8%) with Fast-track implementation. In both scenarios, we find comparably high prevalence (~80%) of acquired NNRTI-associated, M184V and K65R mutations. Over 48% of individuals with acquired resistance harbor dual, 44% triple and 7% just single drug mutations. Drug-resistant HIV is predicted to comprise 40% (IQR: 27%-50%) of incident infections, while 70% of prevalent transmitted resistance is NNRTI-associated. At 2018, the projected total resistance is 15% (IQR: 7.5%-25%), with 18% (IQR: 13%-24%) of incident infections from transmitted drug-resistant HIV. CONCLUSIONS: WHO-recommended preferred first-line ART could lead to substantial drug resistance. Effective surveillance of HIV drug resistance and utilization of second-line as well as alternative first-line regimens is crucial.

Dapivirine vaginal ring for HIV prevention: modelling health outcomes, drug resistance and cost-effectiveness.

INTRODUCTION: A vaginal ring containing dapivirine is effective for HIV prevention as pre-exposure prophylaxis (PrEP). We evaluated the potential epidemiological impact and cost-effectiveness of dapivirine vaginal ring PrEP among 22- to 45-year-old women in KwaZulu-Natal, South Africa. METHODS: Using mathematical modelling, we studied dapivirine vaginal ring PrEP implementation, either unprioritized, or prioritized based on HIV incidence (≥3% per year), age (22 to 29 years) or female sex worker status, alongside the implementation of voluntary medical male circumcision and antiretroviral therapy scaled-up to UNAIDS Fast-Track targets. Outcomes over the intervention (2019 to 2030) and lifetime horizons included cumulative HIV infections, life-years lived, costs and cost-effectiveness. We assessed the incremental cost-effectiveness ratios against the revealed willingness to pay ($500) and the standard (2017 per capita gross domestic product; $6161) cost-effectiveness thresholds for South Africa. RESULTS: Compared to a reference scenario without PrEP, implementation of dapivirine vaginal ring PrEP, assuming 56% effectiveness and covering 50% of 22 to 29-year-old or high-incidence women, prevented 10% or 11% of infections by 2030 respectively. Equivalent, unprioritized coverage (30%) prevented fewer infections (7%), whereas 50% coverage of female sex workers had the least impact (4%). Drug resistance attributable to PrEP was modest (2% to 4% of people living with drug-resistant HIV). Over the lifetime horizon, dapivirine PrEP implementation among female sex workers was cost-saving, whereas incidence-based PrEP cost $1898 per life-year gained, relative to PrEP among female sex workers and $989 versus the reference scenario. In a scenario of 37% PrEP effectiveness, PrEP had less impact, but prioritization to female sex workers remained cost-saving. In uncertainty analysis, female sex worker PrEP was consistently cost-saving; and over the lifetime horizon, PrEP cost less than $6161 per life-year gained in over 99% of simulations, whereas incidence- and age-based PrEP cost below $500 per life-year gained in 61% and 49% of simulations respectively. PrEP adherence and efficacy, and the effectiveness of antiretroviral therapy for HIV prevention, were the principal drivers of uncertainty in the cost-effectiveness of PrEP. CONCLUSIONS: Dapivirine vaginal ring PrEP would be cost-saving in KwaZulu-Natal if prioritized to female sex workers. PrEP's impact on HIV prevention would be increased, with potential affordability, if prioritized to women by age or incidence.

Assembly of three-dimensional binary superlattices from multi-flavored particles.

Binary superlattices constructed from nano- or micron-sized colloidal particles have a wide variety of applications, including the design of advanced materials. Self-assembly of such crystals from their constituent colloids can be achieved in practice by, among other means, the functionalization of colloid surfaces with single-stranded DNA sequences. However, when driven by DNA, this assembly is traditionally premised on the pairwise interaction between a single DNA sequence and its complement, and often relies on particle size asymmetry to entropically control the crystalline arrangement of its constituents. The recently proposed "multi-flavoring" motif for DNA functionalization, wherein multiple distinct strands of DNA are grafted in different ratios to different colloids, can be used to experimentally realize a binary mixture in which all pairwise interactions are independently controllable. In this work, we use various computational methods, including molecular dynamics and Wang-Landau Monte Carlo simulations, to study a multi-flavored binary system of micron-sized DNA-functionalized particles modeled implicitly by Fermi-Jagla pairwise interactions. We show how self-assembly of such systems can be controlled in a purely enthalpic manner, and by tuning only the interactions between like particles, demonstrate assembly into various morphologies. Although polymorphism is present over a wide range of pairwise interaction strengths, we show that careful selection of interactions can lead to the generation of pure compositionally ordered crystals. Additionally, we show how the crystal composition changes with the like-pair interaction strengths, and how the solution stoichiometry affects the assembled structures.

Binary Superlattice Design by Controlling DNA-Mediated Interactions.

Most binary superlattices created using DNA functionalization rely on particle size differences to achieve compositional order and structural diversity. Here we study two-dimensional (2D) assembly of DNA-functionalized micron-sized particles (DFPs), and employ a strategy that leverages the tunable disparity in interparticle interactions, and thus enthalpic driving forces, to open new avenues for design of binary superlattices that do not rely on the ability to tune particle size (i.e., entropic driving forces). Our strategy employs tailored blends of complementary strands of ssDNA to control interparticle interactions between micron-sized silica particles in a binary mixture to create compositionally diverse 2D lattices. We show that the particle arrangement can be further controlled by changing the stoichiometry of the binary mixture in certain cases. With this approach, we demonstrate the ability to program the particle assembly into square, pentagonal, and hexagonal lattices. In addition, different particle types can be compositionally ordered in square checkerboard and hexagonal-alternating string, honeycomb, and Kagome arrangements.

Effect of Nonionic Surfactant on Association/Dissociation Transition of DNA-Functionalized Colloids.

We report the effect of nonionic surfactants (Pluronics F127 and F88) on the melting transition of micron-sized colloids confined in two dimensions, mediated by complementary single-stranded DNA as a function of the surfactant concentration. Micron-sized silica particles were functionalized with single-stranded DNA using cyanuric chloride chemistry. The existence of covalently linked DNA on particles was confirmed by fluorescence spectroscopy. The nonionic surfactant not only plays a significant role in stabilization of particles, with minimization of nonspecific binding, but also impacts the melting temperature, which increases as a function of the nonionic surfactant concentration. These results suggest that the melting transition for DNA-mediated assembly is sensitive to commonly used additives in laboratory buffers, and that these common solution components may be exploited as a facile and independent handle for tuning the melting temperature and, thus, the assembly and possibly crystallization within these systems.

Equilibrium and nonequilibrium dynamics of soft sphere fluids.

We use computer simulations to test the freezing-point scaling relationship between equilibrium transport coefficients (self-diffusivity, viscosity) and thermodynamic parameters for soft sphere fluids. The fluid particles interact via the inverse-power potential (IPP), and the particle softness is changed by modifying the exponent of the distance-dependent potential term. In the case of IPP fluids, density and temperature are not independent variables and can be combined to obtain a coupling parameter to define the thermodynamic state of the system. We find that the rescaled coupling parameter, based on its value at the freezing point, can approximately collapse the diffusivity and viscosity data for IPP fluids over a wide range of particle softness. Even though the collapse is far from perfect, the freezing-point scaling relationship provides a convenient and effective way to compare the structure and dynamics of fluid systems with different particle softness. We further show that an alternate scaling relationship based on two-body excess entropy can provide an almost perfect collapse of the diffusivity and viscosity data below the freezing transition. Next, we perform nonequilibrium molecular dynamics simulations to calculate the shear-dependent viscosity and to identify the distinct role of particle softness in underlying structural changes associated with rheological properties. Qualitatively, we find a similar shear-thinning behavior for IPP fluids with different particle softness, though softer particles exhibit stronger shear-thinning tendency. By investigating the distance and angle-dependent pair correlation functions in these systems, we find different structural features in the case of IPP fluids with hard-sphere like and softer particle interactions. Interestingly, shear-thinning in hard-sphere like fluids is accompanied by enhanced translational order, whereas softer fluids exhibit loss of order with shear. Our results provide a systematic evaluation of the role of particle softness in equilibrium and nonequilibrium transport properties and their underlying connection with thermodynamic and structural properties.