The Hill equation: a review of its capabilities in pharmacological modelling

Gated Organonanoclays for Large Biomolecules: Controlled Release Triggered by Surfactant Stimulus

The low toxicity and high adsorption capacities of clay minerals make them attractive for controlled delivery applications. However, the number of controlled-release studies in the literature using clay minerals is still scarce. In this work, three different clays from the smectite group (Kunipia F, montmorillonite; Sumecton SA, saponite; and Sumecton SWN, hectorite) were successfully loaded with rhodamine B dye and functionalized with oleic acid as a gatekeeper to produce organonanoclays for active and controlled payload-release. Moreover, hematin and cyanocobalamin have also been encapsulated in hectorite gated clay. These organonanoclays were able to confine the entrapped cargos in an aqueous environment, and effectively release them in the presence of surfactants (as bile salts). A controlled delivery of 49 ± 6 μg hematin/mg solid and 32.7 ± 1.5 μg cyanocobalamin/mg solid was reached. The cargo release profiles of all of the organonanoclays were adjusted to three different release-kinetic models, demonstrating the Korsmeyer-Peppas model with release dependence on (i) the organic-inorganic hybrid system, and (ii) the nature of loaded molecules and their interaction with the support. Furthermore, in vitro cell viability assays were carried out with Caco-2 cells, demonstrating that the organonanoclays are well tolerated by cells at particle concentrations of ca. 50 μg/mL.

Preparations of Terminal Oxidase Cytochrome bd-II Isolated from Escherichia coli Reveal Significant Hydrogen Peroxide Scavenging Activity

Cytochrome bd-II is one of the three terminal quinol oxidases of the aerobic respiratory chain of Escherichia coli. Preparations of the detergent-solubilized untagged bd-II oxidase isolated from the bacterium were shown to scavenge hydrogen peroxide (H2O2) with high rate producing molecular oxygen (O₂). Addition of H2O2 to the same buffer that does not contain enzyme or contains thermally denatured cytochrome bd-II does not lead to any O2 production. The latter observation rules out involvement of adventitious transition metals bound to the protein. The H2O2-induced O2 production is not susceptible to inhibition by N-ethylmaleimide (the sulfhydryl binding compound), antimycin A (the compound that binds specifically to a quinol binding site), and CO (diatomic gas that binds specifically to the reduced heme d). However, O2 formation is inhibited by cyanide (IC₅₀ = 4.5 ± 0.5 µM) and azide. Addition of H2O2 in the presence of dithiothreitol and ubiquinone-1 does not inactivate cytochrome bd-II and apparently does not affect the O2 reductase activity of the enzyme. The ability of cytochrome bd-II to detoxify H2O2 could play a role in bacterial physiology by conferring resistance to the peroxide-mediated stress.

Modeling synergistic effects by using general Hill-type response surfaces describing drug interactions

The classification of effects caused by mixtures of agents as synergistic, antagonistic or additive depends critically on the reference model of 'null interaction'. Two main approaches to describe co-operative effects are currently in use, the Additive Dose (ADM) or concentration addition (CA) and the Multiplicative Survival (MSM) or independent action (IA) models. Recently we proposed an approach which describes 'zero-interaction' surfaces based on the only requirement that simultaneous administration of different drugs leads to Hill-type response surfaces, which are solutions of the underlying logistic differential equations. No further assumptions, neither on mechanisms of action nor on limitations of parameter combinations are required. This defines-and limits-the application range of our approach. Resting on the same principle, we extend this ansatz in the present paper in order to describe deviations from the reference surface by generalized Hill-type functions. To this end we introduce two types of parameters, perturbations of the pure drug Hill-parameters and interaction parameters that account for n-tuple interactions between all components of a mixture. The resulting 'full-interaction' response surface is a valid solution of the basic partial differential equation (PDE), satisfying appropriate boundary conditions. This is true irrespective of its actual functional form, as within our framework the number of parameters is not fixed. We start by fitting the experimental data to the 'full-interaction' model with the maximum possible number of parameters. Guided by the fit-statistics, we then gradually remove insignificant parameters until the optimum response surface model is obtained. The 'full-interaction' Hill response surface ansatz can be applied to mixtures of n compounds with arbitrary Hill parameters including those describing baseline effects. Synergy surfaces, i.e., differences between full- and null-interaction models, are used to identify dose-combinations showing peak synergies. We apply our approach to binary and ternary examples from the literature, which range from mixtures behaving according to the null-interaction model to those showing strong synergistic or antagonistic effects. By comparing 'null-' and 'full-response' surfaces we identify those dose-combinations that lead to maximum synergistic or antagonistic effects. In one example we identify both synergistic and antagonistic effects simlutaneously, depending on the dose-ratio of the components. In addition we show that often the number of parameters necessary to describe the response can be reduced without significantly affecting the accuracy. This facilitates an analysis of the synergistic effects by focussing on the main factors causing the deviations from 'null-interaction'.

Overt and occult hypoxemia in patients hospitalized with novel coronavirus disease 2019

Background

Progressive hypoxemia is the predominant mode of deterioration in COVID-19. Among hypoxemia measures, the ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen (P/F ratio) has optimal construct validity but poor availability because it requires arterial blood sampling. Pulse oximetry reports oxygenation continuously, but occult hypoxemia can occur in Black patients because the technique is affected by skin color. Oxygen dissociation curves allow non-invasive estimation of P/F ratios (ePFR) but this approach remains unproven.

Research Question

Can ePFRs measure overt and occult hypoxemia?

Study Design and methods

We retrospectively studied COVID-19 hospital encounters (n=5319) at two academic centers (University of Virginia [UVA] and Emory University). We measured primary outcomes (death or ICU transfer within 24 hours), ePFR, conventional hypoxemia measures, baseline predictors (age, sex, race, comorbidity), and acute predictors (National Early Warning Score (NEWS) and Sepsis-3). We updated predictors every 15 minutes. We assessed predictive validity using adjusted odds ratios (AOR) and area under receiver operating characteristics curves (AUROC). We quantified disparities (Black vs non-Black) in empirical cumulative distributions using the Kolmogorov-Smirnov (K-S) two-sample test.

Results

Overt hypoxemia (low ePFR) predicted bad outcomes (AOR for a 100-point ePFR drop: 2.7 [UVA]; 1.7 [Emory]; p<0.01) with better discrimination (AUROC: 0.76 [UVA]; 0.71 [Emory]) than NEWS (AUROC: 0.70 [UVA]; 0.70 [Emory]) or Sepsis-3 (AUROC: 0.68 [UVA]; 0.65 [Emory]). We found racial differences consistent with occult hypoxemia. Black patients had better apparent oxygenation (K-S distance: 0.17 [both sites]; p<0.01) but, for comparable ePFRs, worse outcomes than other patients (AOR: 2.2 [UVA]; 1.2 [Emory], p<0.01).

Interpretation

The ePFR was a valid measure of overt hypoxemia. In COVID-19, it may outperform multi-organ dysfunction models like NEWS and Sepsis-3. By accounting for biased oximetry as well as clinicians’ real-time responses to it (supplemental oxygen adjustment), ePFRs may enable statistical modelling of racial disparities in outcomes attributable to occult hypoxemia.

Antibody-Mediated Screening of Peptide Inhibitors for Monoamine Oxidase-B (MAO-B) from an Autodisplayed FV Library

Inhibitors for monoamine oxidase-B (MAO-B) were screened from an F_V library with a randomized complementarity-determining region 3 (CDR3) region using a monoclonal antibody against dopamine. As the first step, the F_V library was expressed on the outer membrane of E. coli by site-directed mutagenesis of the randomized CDR3 region. Among the F_V library, variants with a binding affinity to monoclonal antibodies against dopamine were screened and cloned. From the comparison of the binding activity of the screened clones to a control clone with a modified F_V antibody (only with CDR1 and CDR2), the CDR3 regions of screened clones were determined to directly interact with the monoclonal antibody against dopamine. These CDR3 sequences were then synthesized as mimotopes (mimicking peptides) of dopamine. The inhibitory activity of two mimotopes against MAO-B was analyzed using HeLa cells overexpressing MAO-B, as well as using activated human astrocytes; their inhibitory activity was compared to that of a commercial inhibitor of MAO-B, selegiline. The inhibition efficiency of the two mimotopes (in comparison with selegiline) was estimated to be 67.2% and 69.4% in the HeLa cells and 64.4% and 58.0% in the human astrocytes. The gene expression pattern in astrocytes after treatment with the two mimotopes was also analyzed and compared with that in the human astrocytes treated with selegiline. Finally, the interaction between two mimotopes and MAO-B was analyzed using docking simulation, and the candidate regions of MAO-B for the interaction with each mimotope were explored through the docking simulation.

Understanding the combined effects of multiple stressors: A new perspective on a longstanding challenge

Wildlife populations and their habitats are exposed to an expanding diversity and intensity of stressors caused by human activities, within the broader context of natural processes and increasing pressure from climate change. Estimating how these multiple stressors affect individuals, populations, and ecosystems is thus of growing importance. However, their combined effects often cannot be predicted reliably from the individual effects of each stressor, and we lack the mechanistic understanding and analytical tools to predict their joint outcomes. We review the science of multiple stressors and present a conceptual framework that captures and reconciles the variety of existing approaches for assessing combined effects. Specifically, we show that all approaches lie along a spectrum, reflecting increasing assumptions about the mechanisms that regulate the action of single stressors and their combined effects. An emphasis on mechanisms improves analytical precision and predictive power but could introduce bias if the underlying assumptions are incorrect. A purely empirical approach has less risk of bias but requires adequate data on the effects of the full range of anticipated combinations of stressor types and magnitudes. We illustrate how this spectrum can be formalised into specific analytical methods, using an example of North Atlantic right whales feeding on limited prey resources while simultaneously being affected by entanglement in fishing gear. In practice, case-specific management needs and data availability will guide the exploration of the stressor combinations of interest and the selection of a suitable trade-off between precision and bias. We argue that the primary goal for adaptive management should be to identify the most practical and effective ways to remove or reduce specific combinations of stressors, bringing the risk of adverse impacts on populations and ecosystems below acceptable thresholds.

Ice crystal recrystallization inhibition of type I antifreeze protein, type III antifreeze protein, and antifreeze glycoprotein: effects of AF(G)Ps concentration and heat treatment

This study compared ice recrystallization behaviors of frozen dessert model systems containing type I antifreeze protein (AFP I), type III antifreeze protein (AFP III), and antifreeze glycoprotein (AFGP) at -10 °C. Specifically, effects of AF(G)P concentration and heat treatment (95 °C for 10 min) were examined. The concentration dependence of the ice recrystallization rate constant reasonably well fit a sigmoidal function: the fitting procedure was proposed, along with cooperative coefficient α, and a new index of AF(G)P ice recrystallization inhibition (IRI) activity (C50). After 95 °C heat treatment for 10 min, AFP III lost its ice crystal recrystallization inhibitory activity the most: AFP I was less affected; AFGP was almost entirely unaffected. These different thermal treatment effects might reflect a lower degree of protein aggregation because of hydrophobic interaction after heat treatment or might reflect the simplicity and flexibility of the higher order structures of AFP I and AFGP.

Preclinical and randomized phase I studies of plitidepsin in adults hospitalized with COVID-19

Plitidepsin, a marine-derived cyclic-peptide, inhibits SARS-CoV-2 replication at nanomolar concentrations by targeting the host protein eukaryotic translation elongation factor 1A. Here, we show that plitidepsin distributes preferentially to lung over plasma, with similar potency against across several SARS-CoV-2 variants in preclinical studies. Simultaneously, in this randomized, parallel, open-label, proof-of-concept study (NCT04382066) conducted in 10 Spanish hospitals between May and November 2020, 46 adult hospitalized patients with confirmed SARS-CoV-2 infection received either 1.5 mg (n = 15), 2.0 mg (n = 16), or 2.5 mg (n = 15) plitidepsin once daily for 3 d. The primary objective was safety; viral load kinetics, mortality, need for increased respiratory support, and dose selection were secondary end points. One patient withdrew consent before starting procedures; 45 initiated treatment; one withdrew because of hypersensitivity. Two Grade 3 treatment-related adverse events were observed (hypersensitivity and diarrhea). Treatment-related adverse events affecting more than 5% of patients were nausea (42.2%), vomiting (15.6%), and diarrhea (6.7%). Mean viral load reductions from baseline were 1.35, 2.35, 3.25, and 3.85 log10 at days 4, 7, 15, and 31. Nonmechanical invasive ventilation was required in 8 of 44 evaluable patients (16.0%); six patients required intensive care support (13.6%), and three patients (6.7%) died (COVID-19-related). Plitidepsin has a favorable safety profile in patients with COVID-19.

Defect-controlled halogenating properties of lanthanide-doped ceria nanozymes

Marine organisms combat bacterial colonization by biohalogenation of signaling compounds that interfere with bacterial communication. These reactions are catalyzed by haloperoxidase enzymes, whose activity can be emulated by nanoceria using milli- and micromolar concentrations of Br^- and H₂O₂. We show that the haloperoxidase-like activity of nanoceria can greatly be enhanced by Ln substitution in Ce_1-xLn_xO_2-x/2. Non-agglomerated nanosized Ce_1-xLn_xO_2-x/2 (Ln = Pr, Tb, particle size < 10 nm) was prepared mechanochemically from CeCl₃ and Na₂CO₃ followed by short calcination. Lanthanide metals could be incorporated into the CeO₂ host without solubility limit, as shown for Tb. The distribution of the Ln³⁺ defect sites in the CeO₂ host structure was analyzed by electron spin resonance spectroscopy. Ce³⁺ and superoxide O₂^- species are present at surface sites. Their formation is promoted by increasing dopant concentration. Ce_1-xLn_xO_2-x/2 was prepared in copious amounts by ball-milling. This energy-saving and residue-free method can be upscaled to industrial scale. The surface defect chemistry of Ce_1-xLn_xO_2-x/2 was unravelled by vibrational spectroscopy. It is associated with the mechanochemical preparation and leads to enhanced catalytic activity. Although Ce_0.9Pr_0.1O_1.95 had a lower BET surface area than pure CeO₂, its catalytic activity, calibrated by oxidative bromination of phenol red, was much higher because the ζ-potential increased from 15 mV (for CeO₂) to 30 mV (for Ce_0.9Pr_0.1O_1.95). This facilitates adsorption of Br^- in aqueous conditions and explains the high catalytic activity of the Ln-substituted CeO₂. Ce_1-xLn_xO_2-x/2 is an effective and "green" nanoparticle haloperoxidase mimic for antifouling applications, as no chemicals other than the ubiquitous Br^- and H₂O₂ (generated in daylight) are required, and only natural metabolites are released into the environment.

Kinetics of bactericidal potency with synergistic combination of allicin and selected antibiotics

Synergistic therapy against the resurgence of bacterial pathogenesis is a modern trend for antibacterial chemotherapy. The phytochemical allicin, found in garlic extract is a commendable antimicrobial agent that can be used in synergistic combination with modern antibiotics. Determination of optimal antibacterial combination for the target species is vital for maximizing efficacy, lowering toxicity, total eradication of the bacterial cells and minimization of the risk of resistance generation. In this present investigation, Hill function-based pharmacodynamics models were employed to elaborate various time-kill kinetics parameters. The bactericidal potency of the synergistic combinations of allicin and individual antibiotic was assessed in comparison to their monotherapy application viz. using sole allicin and sole antibiotics (levofloxacin, ciprofloxacin, oxytetracycline, rifaximin, ornidazole and azithromycin) on actively growing Bacillus subtilis and Escherichia coli bacteria. Here, all the synergistic combinations showed significantly better (t-test p-value < 0.05) killing effect and biofilm reduction potential compared to their respective monotherapy application, where the highest killing effect was observed with rifaximin-allicin combination (kill rate was more than 5.5 h^-1). Moreover, the average inhibition potential to protein denaturation by the synergistic combination group was significantly higher (3.4 fold) than the sole antibiotic's group manifests reduction in the dose-related toxicity. The potential of synergism between antibiotics and allicin combination demonstrated greater killing efficiency at significantly lower concentration compared to monotherapy with increased kill rates in all cases.

Modelling the impact of nucleolin expression level on the activity of F3 peptide-targeted pH-sensitive pegylated liposomes containing doxorubicin

Strategies targeting nucleolin have enabled a significant improvement in intracellular bioavailability of their encapsulated payloads. In this respect, assessment of the impact of target cell heterogeneity and nucleolin homology across species (structurally and functionally) is of major importance. This work also aimed at mathematically modelling the nucleolin expression levels at the cell membrane, binding and internalization of pH-sensitive pegylated liposomes encapsulating doxorubicin and functionalized with the nucleolin-binding F3 peptide (PEGASEMP), and resulting cytotoxicity against cancer cells from mouse, rat, canine, and human origin. Herein, it was shown that nucleolin expression levels were not a limitation on the continuous internalization of F3 peptide-targeted liposomes, despite the saturable nature of the binding mechanism. Modeling enabled the prediction of nucleolin-mediated total doxorubicin exposure provided by the experimental settings of the assessment of PEGASEMP's impact on cell death. The former increased proportionally with nucleolin-binding sites, a measure relevant for patient stratification. This pattern of variation was observed for the resulting cell death in nonsaturating conditions, depending on the cancer cell sensitivity to doxorubicin. This approach differs from standard determination of cytotoxic concentrations, which normally report values of incubation doses rather than the actual intracellular bioactive drug exposure. Importantly, in the context of development of nucleolin-based targeted drug delivery, the structural nucleolin homology (higher than 84%) and functional similarity across species presented herein, emphasized the potential to use toxicological data and other metrics from lower species to infer the dose for a first-in-human trial.

Modelling the antimicrobial pharmacodynamics for bacterial strains with versus without acquired resistance to fluoroquinolones or cephalosporins

OBJECTIVES

Antimicrobial resistance threatens therapeutic options for human and animal bacterial diseases worldwide. Current antimicrobial treatment regimens were designed against bacterial strains that were fully susceptible to them. To expand the useable lifetime of existing antimicrobial drug classes by modifying treatment regimens, data are needed on the antimicrobial pharmacodynamics (PD) against strains with reduced susceptibility. In this study, we generated and mathematically modelled the PD of the fluoroquinolone ciprofloxacin and the cephalosporin ceftriaxone against non-typhoidal Salmonella enterica subsp. enterica strains with varying levels of acquired resistance.

METHODS

We included Salmonella strains across categories of reduced susceptibility to fluoroquinolones or cephalosporins reported to date, including isolates from human infections, food-animal products sold in retail, and food-animal production. We generated PD data for each drug and strain via time-kill assay. Mathematical models were compared in their fit to represent the PD. The best-fit model's parameter values across the strain susceptibility categories were compared.

RESULTS

The inhibitory baseline sigmoid I_max (or E_max) model was best fit for the PD of each antimicrobial against a majority of the strains. There were statistically significant differences in the PD parameter values across the strain susceptibility categories for each antimicrobial.

CONCLUSION

The results demonstrate predictable multiparameter changes in the PD of these first-line antimicrobials depending on the Salmonella strain's susceptibility phenotype and specific genes conferring reduced susceptibility. The generated PD parameter estimates could be used to optimise treatment regimens against infections by strains with reduced susceptibility.

Double-Resonant Nanostructured Gold Surface for Multiplexed Detection

A novel double-resonant plasmonic substrate for fluorescence amplification in a chip-based apta-immunoassay is herein reported. The amplification mechanism relies on plasmon-enhanced fluorescence (PEF) effect. The substrate consists of an assembly of plasmon-coupled and plasmon-uncoupled gold nanoparticles (AuNPs) immobilized onto a glass slide. Plasmon-coupled AuNPs are hexagonally arranged along branch patterns whose resonance lies in the red band (∼675 nm). Plasmon-uncoupled AuNPs are sprinkled onto the substrate, and they exhibit a narrow resonance at 524 nm. Numerical simulations of the plasmonic response of the substrate through the finite-difference time-domain (FDTD) method reveal the presence of electromagnetic hot spots mainly confined in the interparticle junctions. In order to realize a PEF-based device for potential multiplexing applications, the plasmon resonances are coupled with the emission peak of 5-carboxyfluorescein (5-FAM) fluorophore and with the excitation/emission peaks of cyanine 5 (Cy5). The substrate is implemented in a malaria apta-immunoassay to detect Plasmodium falciparum lactate dehydrogenase (PfLDH) in human whole blood. Antibodies against Plasmodium biomarkers constitute the capture layer, whereas fluorescently labeled aptamers recognizing PfLDH are adopted as the top layer. The fluorescence emitted by 5-FAM and Cy5 fluorophores are linearly correlated (logarithm scale) to the PfLDH concentration over five decades. The limits of detection are 50 pM (1.6 ng/mL) with the 5-FAM probe and 260 fM (8.6 pg./mL) with the Cy5 probe. No sample preconcentration and complex pretreatments are required. Average fluorescence amplifications of 160 and 4500 are measured in the 5-FAM and Cy5 channel, respectively. These results are reasonably consistent with those worked out by FDTD simulations. The implementation of the proposed approach in multiwell-plate-based bioassays would lead to either signal redundancy (two dyes for a single analyte) or to a simultaneous detection of two analytes by different dyes, the latter being a key step toward high-throughput analysis.

The legacy of A. V. Hill's Nobel Prize winning work on muscle energetics

A. V. Hill was awarded the 1922 Nobel Prize, jointly with Otto Meyerhof, for Physiology or Medicine for his work on energetic aspects of muscle contraction. Hill used his considerable mathematical and experimental skills to investigate the relationships among muscle mechanics, biochemistry and heat production. The main ideas of the work for which the Nobel Prize was awarded were superseded within a decade and the legacy of Hill and Meyerhof's Nobel work was not a set of persistent, influential ideas but rather was a prolonged period of extraordinary activity that advanced the understanding of how muscles work far beyond the concepts that led to the Nobel Prize. Hill pioneered the integration of mathematics into the study of physiology and pharmacology. Particular aspects of Hill's own work that remain in common use in muscle physiology include mathematical descriptions of the relationships between muscle force output and shortening velocity and between force output and calcium concentration and the model of muscle as a contractile element in series with an elastic element. We describe some of the characteristics of Hill's broader scientific activities and then outline how Hill's work on muscle energetics was extended after 1922, as a result of Hill's own work and that of others, to the present day. Abstract figure legend. A. V. Hill's scientific legacy. Vertical from the base. A. V. Hill (pictured) and his colleague Otto Meyerhof shared the 1922 Nobel Prize for Physiology or Medicine. Seven enduring elements of Hill's legacy to muscle physiology are shown. Arrows link concepts and approaches to related disciplines where they have been foundational and highly influential. This article is protected by copyright. All rights reserved.

Mathematical Modeling for an MTT Assay in Fluorine-Containing Graphene Quantum Dots

The paper reports on a new mathematical model, starting with the original Hill equation which is derived to describe cell viability (V) while testing nanomaterials (NMs). Key information on the sample's morphology, such as mean size (⟨s⟩) and size dispersity (σ) is included in the new model via the lognormal distribution function. The new Hill-inspired equation is successfully used to fit MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) data from assays performed with the HepG2 cell line challenged by fluorine-containing graphene quantum dots (F:GQDs) under light (400-700 nm wavelength) and dark conditions. The extracted "biological polydispersity" (light: ⟨sMTT⟩=1.77±0.02&nbsp;nm and σMTT=0.21±0.02); dark: ⟨sMTT⟩=1.87±0.02&nbsp;nm and σMTT=0.22±0.01) is compared with the "morphological polydispersity" (⟨sTEM⟩=1.98±0.06&nbsp;nm and σTEM=0.19±0.03), the latter obtained from TEM (transmission electron microscopy). The fitted data are then used to simulate a series of V responses. Two aspects are emphasized in the simulations: (i) fixing σ, one simulates V versus ⟨s⟩ and (ii) fixing ⟨s⟩, one simulates V versus σ. Trends observed in the simulations are supported by a phenomenological model picture describing the monotonic reduction in V as ⟨s⟩ increases (V~pa/(s)p-a; p and a are fitting parameters) and accounting for two opposite trends of V versus σ: under light (V~σ) and under dark (V~1/σ).

Experimental Determination of Cancer Drug Targets with Independent Mechanisms of Resistance

Mathematical modelling of tumour mutation dynamics has suggested that cancer drug targets that have different resistance mechanisms should be good candidates for combination treatment. This is because the development of mutations that cause resistance to all drugs at once should arise relatively infrequently. However, it is difficult to identify drug targets fulfilling this requirement for particular cancers. Here we present four experimental criteria that we argue are necessary (but not sufficient) conditions that drug combinations should meet in order to be considered for combination drug treatment aimed at delaying or overcoming cancer drug resistance. We present the results of our own experiments - guided by these criteria - using anaplastic lymphoma kinase mutated lung cancer cells. Each set of experiments demonstrate results for different drug combinations. We conclude that the combination of ALK and MEK inhibitors come closest to meeting all our criteria.

Seawater activates l-amino acid oxidase from the serum of the red-spotted grouper Epinephelusakaara

l-amino acid oxidases (LAOs) catalyze the oxidative deamination of l-amino acid and generate α-keto acid, ammonia, and hydrogen peroxide as byproducts. LAOs showed the variety of bioactivity by the resulting hydrogen peroxide. The serum of the red-spotted grouper Epinephelus akaara contains an LAO (Ea-LAO) with the potential to kill bacterial pathogens Aeromonas salmonicida and Vibrio anguillarum via hydrogen peroxide. However, it is unknown how the grouper tolerates the harmful effects of the serum Ea-LAO byproducts. In this study, we analyzed the kinetics of fish LAOs to understand how they escape the toxicity of byproducts. The LAO activity of grouper serum was suppressed in low-salt solutions such as NaCl, CaCl₂, MgCl₂, and diluted seawater. The activity was non-linearly increased and fitted to the four-parameter log-logistic model. The EC₅₀ of the seawater was calculated to have a 0.72-fold concentration. This result suggested that the Ea-LAO could be activated by mixing with seawater. The results of circular dichroism spectroscopy showed that the α helix content was estimated to be 12.1% and 5.3% in a salt-free buffer (inactive condition) and the original concentration of seawater (active condition), respectively, indicating that the secondary structure of the Ea-LAO in the active condition was randomized. In addition, the Ea-LAO showed reversible LAO activity regulation according to the salt concentration in the environment. Taken together, this indicates that the Ea-LAO is normally on standby as an inactive form, and it could activate as a host-defense molecule to avoid pathogen invasion via a wound when mixed with seawater.

Transparent polycarbonate coated with CeO2 nanozymes repel Pseudomonas aeruginosa PA14 biofilms

Highly transparent CeO₂/polycarbonate surfaces were fabricated that prevent adhesion, proliferation, and the spread of bacteria. CeO₂ nanoparticles with diameters of 10-15 nm and lengths of 100-200 nm for this application were prepared by oxidizing aqueous dispersions of Ce(OH)₃ with H₂O₂ in the presence of nitrilotriacetic acid (NTA) as the capping agent. The surface-functionalized water-dispersible CeO₂ nanorods showed high catalytic activity in the halogenation reactions, which makes them highly efficient functional mimics of haloperoxidases. These enzymes are used in nature to prevent the formation of biofilms through the halogenation of signaling compounds that interfere with bacterial cell-cell communication ("quorum sensing"). Bacteria-repellent CeO₂/polycarbonate plates were prepared by dip-coating plasma-treated polycarbonate plates in aqueous CeO₂ particle dispersions. The quasi-enzymatic activity of the CeO₂ coating was demonstrated using phenol red enzyme assays. The monolayer coating of CeO₂ nanorods (1.6 μg cm^-2) and the bacteria repellent properties were demonstrated by atomic force microscopy, biofilm assays, and fluorescence measurements. The engineered polymer surfaces have the ability to repel biofilms as green antimicrobials on plastics, where H₂O₂ is present in humid environments such as automotive parts, greenhouses, or plastic containers for rainwater.

Pharmacokinetic-pharmacodynamic modelling of the anti-FcRn monoclonal antibody rozanolixizumab: Translation from preclinical stages to the clinic

Rozanolixizumab is a fully humanized high‐affinity anti‐human neonatal Fc receptor (FcRn) monoclonal antibody (mAb) that accelerates the removal of circulating immunoglobulin G (IgG), including pathogenic IgG autoantibodies, via the natural lysosomal degradation pathway. The aim of this study was to develop a pharmacokinetic/pharmacodynamic (PK/PD) model characterizing the effect of rozanolixizumab on IgG levels in cynomolgus monkeys, translate it into humans to support the first‐in‐human (FIH) rozanolixizumab clinical trial study design, and, ultimately, develop a PK/PD model in humans. Simulations from the preclinical model were performed to predict IgG responses in humans and select clinically relevant doses in the FIH study. Good alignment was observed between predicted and observed reductions in IgG, which increased with increasing dose in the FIH study. The model successfully described the PK of the 4 and 7 mg/kg intravenous (i.v.) dose groups, although the PKs were underpredicted for the 1 mg/kg i.v. dose group. Updating the model with subsequent human data identified parameters that deviated from preclinical assumptions. The updated PK/PD model was able to effectively characterize the PK FcRn‐IgG nonlinear system in response to rozanolixizumab in the FIH data.

Positive Sorption Behaviors in the Ligand Exchanges for Water-Soluble Quantum Dots and a Strategy for Specific Targeting

N,N,N',N'-Tetramethylethylenediamine (TMEDA) and ethylenediamine (EDA) were investigated in-depth in the ligand exchanges for water-soluble CdSe quantum dots (QDs). TMEDA could assist the phase transfer of QDs from apolar solvents to the aqueous solutions as stabilized by mercaptopropionic acid (MPA). We successfully maintained the stability of a series of MPA-capped QDs of different ligand densities for NMR characterizations in aqueous solutions. The proton NMR spectroscopies of MPA of the binding state were used to analyze the ligand densities on the surface of QDs, which were not explored in the past. The binding thermodynamics of the surface ligands of QDs, as analyzed using the Hill equation, demonstrated a positive promoting effect and possible interactions between ligands. EDA in the purification process underwent a spontaneous adsorption with two-stage thermodynamic behaviors as characterized by isothermal titration calorimetry. Due to the positive role of the already adsorbed ligands, excess EDA would further attach to the surface of QDs in the form of non-bonded physisorption, greatly improving the quantum yield (QY) of QDs, and the ligand of this part would almost not change the stability of QDs. We proposed a strategy for the preparation of aqueous QDs with a high QY, followed by fluorescence quenching-enhancement cycles caused by purification-adsorption operations. The strategy made it possible for the preparation of functional QDs with small molecules after purification operations. Kinetics of the sorption of ligands on the surface of QDs were determined by fluorescence spectroscopy. Modified pseudo-second-order kinetics after consideration of the ligand-ligand interaction effect could well analyze the kinetic data. This kinetic model had advantages over the previous ligand exchange model in terms of accuracy, reproducibility, and physical significance. Finally, we used the above strategy for the design of fluorescent QDs for bioimaging of lysosomes, mitochondria, and cancer cells. This work can simplify the preparation of multifunctional fluorescent QDs and avoid complicated ligand design.

Fluorescein and Rhodamine B-Binding Domains from Autodisplayed Fv-Antibody Library

In this study, the binding domains for fluorescent dyes were presented that could be used as synthetic peptides or fusion proteins. Fv-antibodies against two fluorescent dyes (fluorescein and rhodamine B) were screened from the Fv-antibody library, which was prepared on the outer membrane of Escherichia coli using the autodisplay technology. Two clones with binding activities to each fluorescent dye were screened separately from the library using flow cytometry. The binding activity of the screened Fv-antibodies on the outer membrane was analyzed using fluorescent imaging with the corresponding fluorescent dyes. The CDR3 regions of the screened Fv-antibodies (11 amino acid residues) were synthesized into peptides, and each peptide was analyzed for its binding activity to each fluorescent dye using fluorescence resonance energy transfer (FRET) experiments. These CDR3 regions were demonstrated to have a binding activity to each fluorescent dye when the regions were co-expressed as a fusion protein with Z-domain.

Dose- and Sex-Dependent Changes in Hemoglobin Oxygen Affinity by the Micronutrient 5-Hydroxymethylfurfural and α-Ketoglutaric Acid

5-Hydroxymethylfurfural (5-HMF) is known to increase hemoglobin oxygen affinity (Hb–O₂ affinity) and to induce a left shift of the oxygen dissociation curve (ODC). It is under investigation as a therapeutic agent in sickle cell anemia and in conditions where pulmonary oxygen uptake is deteriorated or limited (e.g., various clinical conditions or altitude exposure). The combination of 5-HMF and α-ketoglutaric acid (αKG) is commercially available as a nutritional supplement. To further elucidate dose effects, ODCs were measured in vitro in venous whole blood samples of 20 healthy volunteers (10 female and 10 male) after the addition of three different doses of 5-HMF, αKG and the combination of both. Linear regression analysis revealed a strong dose-dependent increase in Hb–O₂ affinity for 5-HMF (R² = 0.887; p < 0.001) and the commercially available combination with αKG (R² = 0.882; p < 0.001). αKG alone increased Hb–O₂ affinity as well but to a lower extent. Both the combination (5-HMF + αKG) and 5-HMF alone exerted different P50 and Hill coefficient responses overall and between sexes, with more pronounced effects in females. With increasing Hb–O₂ affinity, the sigmoidal shape of the ODC was better preserved by the combination of 5-HMF and αKG than by 5-HMF alone. Concerning the therapeutic effects of 5-HMF, this study emphasizes the importance of adequate dosing in various physiological and clinical conditions, where a left-shifted ODC might be beneficial. By preserving the sigmoidal shape of the ODC, the combination of 5-HMF and αKG at low (both sexes) and medium (males only) doses might be able to better maintain efficient oxygen transport, particularly by mitigating potentially deteriorated oxygen unloading in the tissue. However, expanding knowledge on the interaction between 5-HMF and Hb–O₂ affinity in vitro necessitates further investigations in vivo to additionally assess pharmacokinetic mechanisms.

Rational design of a new antibiotic class for drug-resistant infections

The development of new antibiotics to treat infections caused by drug-resistant Gram-negative pathogens is of paramount importance as antibiotic resistance continues to increase worldwide¹. Here we describe a strategy for the rational design of diazabicyclooctane inhibitors of penicillin-binding proteins from Gram-negative bacteria to overcome multiple mechanisms of resistance, including β-lactamase enzymes, stringent response and outer membrane permeation. Diazabicyclooctane inhibitors retain activity in the presence of β-lactamases, the primary resistance mechanism associated with β-lactam therapy in Gram-negative bacteria^2,3. Although the target spectrum of an initial lead was successfully re-engineered to gain in vivo efficacy, its ability to permeate across bacterial outer membranes was insufficient for further development. Notably, the features that enhanced target potency were found to preclude compound uptake. An improved optimization strategy leveraged porin permeation properties concomitant with biochemical potency in the lead-optimization stage. This resulted in ETX0462, which has potent in vitro and in vivo activity against Pseudomonas aeruginosa plus all other Gram-negative ESKAPE pathogens, Stenotrophomonas maltophilia and biothreat pathogens. These attributes, along with a favourable preclinical safety profile, hold promise for the successful clinical development of the first novel Gram-negative chemotype to treat life-threatening antibiotic-resistant infections in more than 25 years.

Needle-free iontophoresis-driven β-adrenergic sweat rate test

OBJECTIVES

Two CFTR-dependent β-adrenergic sweat rate tests applying intradermal drug injections were reported to better define diagnosis and efficacy of CFTR-directed therapies. The aim of this work was to develop and test a needle-free image-based test and to provide an accurate analysis of the responses.

METHODS

The modified method was conducted by applying two successive iontophoresis sessions using the Macroduct device. Efficiency of drug delivery was tested by evaporimetry. Cholinergically stimulated sweating was evoked by pilocarpine iontophoresis. β-adrenergically stimulated sweating was obtained by iontophoresis of isoproterenol and aminophylline in the presence of atropine and ascorbic acid. A nonlinear mixed-effects (NLME) approach was applied to model volumes of sweat and subject-specific effects displaying inter- and intra-subject variability.

RESULTS

Iontophoresis provided successful transdermal delivery of all drugs, including almost neutral isoproterenol and aminophylline. Pilocarpine was used at a concentration ∼130-times lower than that used in the classical Gibson and Cooke sweat test. Addition of ascorbic acid lowered the pH of the solution, made it stable, prevented isoproterenol degradation and promoted drug iontophoresis. Maximal secretory capacity and kinetic rate of β-adrenergic responses were blunted in CF. A cutoff of 5.2 minutes for ET50, the time to reach the half maximal secretion, discriminated CF from controls with a 100% sensitivity and specificity. Heterozygous showed an apparently reduced kinetic rate and a preserved secretory capacity.

CONCLUSION

We tested a safe, well-tolerated needle-free image-based sweat test potentially applicable in children. Modelling responses by NLME allowed evaluating metrics of CFTR-dependent effects reflecting secretory capacity and kinetic rate.

Photoreactive Molecular Glue for Enhancing the Efficacy of DNA Aptamers by Temporary-to-Permanent Conjugation with Target Proteins

We developed a photoreactive molecular glue, ^BPGlue-N₃, which can provide a universal strategy to enhance the efficacy of DNA aptamers by temporary-to-permanent stepwise stabilization of their conjugates with target proteins. As a proof-of-concept study, we applied ^BPGlue-N₃ to the SL1 (DNA aptamer)/c-Met (target protein) conjugate system. ^BPGlue-N₃ can adhere to and temporarily stabilize this aptamer/protein conjugate multivalently using its guanidinium ion (Gu⁺) pendants that form a salt bridge with oxyanionic moieties (e.g., carboxylate and phosphate) and benzophenone (BP) group that is highly affinitive to DNA duplexes. ^BPGlue-N₃ is designed to carry a dual-mode photoreactivity; upon exposure to UV light, the temporarily stabilized aptamer/protein conjugate reacts with the photoexcited BP unit of adhering ^BPGlue-N₃ and also a nitrene species, possibly generated by the BP-to-N₃ energy transfer in ^BPGlue-N₃. We confirmed that SL1, covalently conjugated with c-Met, hampered the binding of hepatocyte growth factor (HGF) onto c-Met, even when the SL1/c-Met conjugate was rinsed prior to the treatment with HGF, and suppressed cell migration caused by HGF-induced c-Met phosphorylation.

Advances in antimicrobial activity analysis of fluoroquinolone, macrolide, sulfonamide, and tetracycline antibiotics for environmental applications through improved bacteria selection

The widespread use of antibiotics has led to their ubiquitous presence in water and wastewater and raised concerns about antimicrobial resistance. Clinical antibiotic susceptibility assays have been repurposed to measure removal of antimicrobial activity during water and wastewater treatment processes. The corresponding protocols have mainly employed growth inhibition of Escherichia coli. The present work focused on optimizing bacteria selection to improve the sensitivity of residual antimicrobial activity measurements by broth microdilution assays. Thirteen antibiotics from four classes (i.e., fluoroquinolones, macrolides, sulfonamides, tetracyclines) were investigated against three gram-negative organisms, namely E. coli, Mycoplasma microti, and Pseudomonas fluorescens. The minimum inhibitory concentration (MIC) and half-maximal inhibitory concentration (IC₅₀) were calculated for each antibiotic-bacteria pair. P. fluorescens produces a fluorescent siderophore, pyoverdine, that was used to assess sublethal effects and further enhance the sensitivity of antimicrobial activity measurements. The optimal antibiotic-bacteria pairs were as follows: fluoroquinolone-E. coli (growth inhibition); macrolide- and sulfonamide-M. microti (growth inhibition); and, tetracycline-P. fluorescens (pyoverdine inhibition). Compared to E. coli growth inhibition, the sensitivity of antimicrobial activity analysis was improved by up to 728, 19, and 2.7 times for macrolides (tylosin), sulfonamides (sulfamethoxazole), and tetracyclines (chlortetracycline), facilitating application of these bioassays at environmentally-relevant conditions.

High-throughput determination of oxygen dissociation curves in a microplate reader-A novel, quantitative approach

In vitro determination of the hemoglobin oxygen dissociation curve (ODC) requires highly elaborate, specialized, and costly technical equipment. In addition, there is a lack of methods that combine reliable ODC recordings with high throughput in small blood samples for routine analysis. We here introduce a modified, commercial 96-well plate with an integrated unidirectional gas flow system specifically adapted for use in fluorescence microplate readers. Up to 92 samples of whole or hemolyzed, buffered or unbuffered blood, including appropriate controls or internal standard hemoglobin solutions, can be analyzed within ~25 min. Oxygen saturation is measured in each well with dual wavelength spectroscopy, and oxygen partial pressure using fluorescence lifetime of commercial oxygen sensors at the in- and outlet ports of the gas-flow system. Precision and accuracy of this method have been determined and were compared with those of a standard method. We further present two applications that exemplarily highlight the usefulness and impact of this novel approach for clinical diagnostics or basic research.

A Validated Mathematical Model of the Cytokine Release Syndrome in Severe COVID-19

By June 2021, a new contagious disease, the Coronavirus disease 2019 (COVID-19), has infected more than 172 million people worldwide, causing more than 3.7 million deaths. Many aspects related to the interactions of the disease's causative agent, SAR2-CoV-2, and the immune response are not well understood: the multiscale interactions among the various components of the human immune system and the pathogen are very complex. Mathematical and computational tools can help researchers to answer these open questions about the disease. In this work, we present a system of fifteen ordinary differential equations that models the immune response to SARS-CoV-2. The model is used to investigate the hypothesis that the SARS-CoV-2 infects immune cells and, for this reason, induces high-level productions of inflammatory cytokines. Simulation results support this hypothesis and further explain why survivors have lower levels of cytokines levels than non-survivors.

Diversified amino acid-mediated allosteric regulation of phosphoglycerate dehydrogenase for serine biosynthesis in land plants

The phosphorylated pathway of serine biosynthesis is initiated with 3-phosphoglycerate dehydrogenase (PGDH). The liverwort Marchantia polymorpha possesses an amino acid-sensitive MpPGDH which is inhibited by l-serine and activated by five proteinogenic amino acids, while the eudicot Arabidopsis thaliana has amino acid-sensitive AtPGDH1 and AtPGDH3 as well as amino acid-insensitive AtPGDH2. In this study, we analyzed PGDH isozymes of the representative land plants: the monocot Oryza sativa (OsPGDH1–3), basal angiosperm Amborella trichopoda (AmtriPGDH1–2), and moss Physcomitrium (Physcomitrella) patens (PpPGDH1–4). We demonstrated that OsPGDH1, AmtriPGDH1, PpPGDH1, and PpPGDH3 were amino acid-sensitive, whereas OsPGDH2, OsPGDH3, AmtriPGDH2, PpPGDH2, and PpPGDH4 were either sensitive to only some of the six effector amino acids or insensitive to all effectors. This indicates that PGDH sensitivity to effectors has been diversified among isozymes and that the land plant species examined, except for M. polymorpha, possess different isozyme types in terms of regulation. Phylogenetic analysis suggested that the different sensitivities convergently evolved in the bryophyte and angiosperm lineages. Site-directed mutagenesis of AtPGDH1 revealed that Asp⁵³⁸ and Asn⁵⁵⁶ residues in the ACT domain are involved in allosteric regulation by the effectors. These findings provide insight into the evolution of PGDH isozymes, highlighting the functional diversification of allosteric regulation in land plants.

Rifampicin exposure reveals within-host Mycobacterium tuberculosis diversity in patients with delayed culture conversion

Mycobacterium tuberculosis (Mtb) genetic micro-diversity in clinical isolates may underline mycobacterial adaptation to tuberculosis (TB) infection and provide insights to anti-TB treatment response and emergence of resistance. Herein we followed within-host evolution of Mtb clinical isolates in two cohorts of TB patients, either with delayed Mtb culture conversion (> 2 months), or with fast culture conversion (< 2 months). We captured the genetic diversity of Mtb isolates obtained in each patient, by focusing on minor variants detected as unfixed single nucleotide polymorphisms (SNPs). To unmask antibiotic tolerant sub-populations, we exposed these isolates to rifampicin (RIF) prior to whole genome sequencing (WGS) analysis. Thanks to WGS, we detected at least 1 unfixed SNP within the Mtb isolates for 9/15 patients with delayed culture conversion, and non-synonymous (ns) SNPs for 8/15 patients. Furthermore, RIF exposure revealed 9 additional unfixed nsSNP from 6/15 isolates unlinked to drug resistance. By contrast, in the fast culture conversion cohort, RIF exposure only revealed 2 unfixed nsSNP from 2/20 patients. To better understand the dynamics of Mtb micro-diversity, we investigated the variant composition of a persistent Mtb clinical isolate before and after controlled stress experiments mimicking the course of TB disease. A minor variant, featuring a particular mycocerosates profile, became enriched during both RIF exposure and macrophage infection. The variant was associated with drug tolerance and intracellular persistence, consistent with the pharmacological modeling predicting increased risk of treatment failure. A thorough study of such variants not necessarily linked to canonical drug-resistance, but which are prone to promote anti-TB drug tolerance, may be crucial to prevent the subsequent emergence of resistance. Taken together, the present findings support the further exploration of Mtb micro-diversity as a promising tool to detect patients at risk of poorly responding to anti-TB treatment, ultimately allowing improved and personalized TB management.

Tuberculosis (TB) is caused by Mycobacterium tuberculosis (Mtb), bacteria that are able to persist inside the patient for many months or years, thus requiring long antibiotic treatments. Here we focused on TB patients with delayed response to treatment and we performed genetic characterization of Mtb isolates to search for sub-populations that may tolerate anti-TB drugs. We found that Mtb cultured from 9/15 patients contained different sub-populations, and in vitro drug exposure revealed Mtb sub-populations in 6/15 isolates, none related to known drug-resistance mechanisms. By contrast, drug exposure revealed Mtb sup-populations in 2/20 isolates in the control cohort of patients with fast culture conversion. Furthermore, we characterized a Mtb variant isolated from a sub-population growing in the presence of rifampicin (RIF), a major anti-TB drug. We found that this variant featured a modified lipidic envelope, and that it was able to develop in the presence of RIF and inside human macrophage cells. We performed pharmacological modelling and found that this kind of variant may be related to a poor response to treatment. In conclusion, searching for particular Mtb sub-populations may help to detect patients at risk of treatment failure and provide additional guidance for TB management.

Nonspecific Binding-Fundamental Concepts and Consequences for Biosensing Applications

Nature achieves differentiation of specific and nonspecific binding in molecular interactions through precise control of biomolecules in space and time. Artificial systems such as biosensors that rely on distinguishing specific molecular binding events in a sea of nonspecific interactions have struggled to overcome this issue. Despite the numerous technological advancements in biosensor technologies, nonspecific binding has remained a critical bottleneck due to the lack of a fundamental understanding of the phenomenon. To date, the identity, cause, and influence of nonspecific binding remain topics of debate within the scientific community. In this review, we discuss the evolution of the concept of nonspecific binding over the past five decades based upon the thermodynamic, intermolecular, and structural perspectives to provide classification frameworks for biomolecular interactions. Further, we introduce various theoretical models that predict the expected behavior of biosensors in physiologically relevant environments to calculate the theoretical detection limit and to optimize sensor performance. We conclude by discussing existing practical approaches to tackle the nonspecific binding challenge in vitro for biosensing platforms and how we can both address and harness nonspecific interactions for in vivo systems.

Interaction between extracellular ATP5A1 and LPS alleviates LPS-induced neuroinflammation in mice

Neuroinflammation is one of the main causes of Alzheimer's disease (AD). The presence of Lipopolysaccharide (LPS) in senile plaques (SP) of AD suggests that it plays a role in AD pathogenesis. ATP5A1 (F1F0-ATP synthase F1 α subunit) is abundant in SP. Further, the protein has recently been found to have an anti-infection role in zebrafish embryos. In the present study, we observed that LPS levels were higher in the brains of APP/PS1 mice than in control mice, and LPS co-localised with ATP5A1 in amyloid plaques. The interaction of recombinant ATP5A1(rATP5A1) and LPS was evidenced by cellular thermal shift assay and enzyme-linked immunosorbent assay-based binding assay in vitro. Neuroinflammation in the brain of a mouse model was induced by intracerebroventricular injection of LPS. The addition of rATP5A1 relieved LPS-induced reduction of spontaneous locomotor ability, depressive-like behaviour, and working memory impairment. Furthermore, rATP5A1 suppressed the activation of astrocytes and microglia, IL-1β accumulation, and tau phosphorylation induced by LPS. Taken together, findings suggest that ATP5A1 is involved in the regulation of LPS-mediated neuroinflammation in AD.

A Cytotoxic Bis(1,2,3-triazol-5-ylidene)carbazolide Gold(III) Complex Targets DNA by Partial Intercalation

The syntheses of bis(triazolium)carbazole precursors and their corresponding coinage metal (Au, Ag) complexes are reported. For alkylated triazolium salts, di- or tetranuclear complexes with bridging ligands were isolated, while the bis(aryl) analogue afforded a bis(carbene) AuI -CNC pincer complex suitable for oxidation to the redox-stable [AuIII (CNC)Cl]+ cation. Although the ligand salt and the [AuIII (CNC)Cl]+ complex were both notably cytotoxic toward the breast cancer cell line MDA-MB-231, the AuIII complex was somewhat more selective. Electrophoresis, viscometry, UV-vis, CD and LD spectroscopy suggest the cytotoxic [AuIII (CNC)Cl]+ complex behaves as a partial DNA intercalator. In silico screening indicated that the [AuIII (CNC)Cl]+ complex can target DNA three-way junctions with good specificity, several other regular B-DNA forms, and Z-DNA. Multiple hydrophobic π-type interactions involving T and A bases appear to be important for B-form DNA binding, while phosphate O⋅⋅⋅Au interactions evidently underpin Z-DNA binding. The CNC ligand effectively stabilizes the AuIII ion, preventing reduction in the presence of glutathione. Both the redox stability and DNA affinity of the hit compound might be key factors underpinning its cytotoxicity in vitro.

Dose estimation for bivalirudin during pediatric cardiopulmonary bypass

AIM

A typical adult-based bivalirudin regimen during cardiopulmonary bypass uses a loading dose of 1 mg kg^-1 and a circuit prime (volume L × 13 mg) with a subsequent intravenous infusion 2.5 mg h^-1  kg^-1 . Dose in children remains unknown. We wished to determine a practical bivalirudin dosing schedule for children undergoing surgery with cardiopulmonary bypass.

METHODS

Published pharmacokinetic parameters in children who were anticoagulated for cardiac catheterization using bivalirudin were compared to adult by scaling for size using allometry. An infusion regimen suitable for children was determined using a bivalirudin target concentration (13 mg L^-1 ) common in adults for effect during cardiopulmonary bypass. Predicted bivalirudin infusion rates in children were compared to regimens published as case reports.

RESULTS

Current pediatric bivalirudin infusion rates are based on those used in adults with titration during cardiopulmonary bypass to achieve activated clotting times longer than 400 s. Bivalirudin clearance (mL min^-1  kg^-1 ) can be estimated in children by scaling adult parameters using allometry. Clearance decreases through childhood and higher infusion rates in children would achieve target concentration rapidly without the need to titrate initial infusion rate. An infusion rate of 4.5 mg h^-1  kg^-1 in a 10 kg infant, 4 mg h^-1  kg^-1 in a 20 kg child and 3.5 mg h^-1  kg^-1 in a child 30-40 kg will target an activated clotting time slower than 400 s. Adult regimens could be used in those children heavier than 50 kg.

CONCLUSION

Bivalirudin infusion in children should be started after loading dose at rates greater than those used in adults. Dose in neonates remains uncertain because neither pharmacokinetics nor coagulation pharmacodynamics have been adequately characterized.

Cardiac myosin-binding protein C interaction with actin is inhibited by compounds identified in a high-throughput fluorescence lifetime screen

Cardiac myosin-binding protein C (cMyBP-C) interacts with actin and myosin to modulate cardiac muscle contractility. These interactions are disfavored by cMyBP-C phosphorylation. Heart failure patients often display decreased cMyBP-C phosphorylation, and phosphorylation in model systems has been shown to be cardioprotective against heart failure. Therefore, cMyBP-C is a potential target for heart failure drugs that mimic phosphorylation or perturb its interactions with actin/myosin. Here we have used a novel fluorescence lifetime-based assay to identify small-molecule inhibitors of actin-cMyBP-C binding. Actin was labeled with a fluorescent dye (Alexa Fluor 568, AF568) near its cMyBP-C binding sites; when combined with the cMyBP-C N-terminal fragment, C0-C2, the fluorescence lifetime of AF568-actin decreases. Using this reduction in lifetime as a readout of actin binding, a high-throughput screen of a 1280-compound library identified three reproducible hit compounds (suramin, NF023, and aurintricarboxylic acid) that reduced C0-C2 binding to actin in the micromolar range. Binding of phosphorylated C0-C2 was also blocked by these compounds. That they specifically block binding was confirmed by an actin-C0-C2 time-resolved FRET (TR-FRET) binding assay. Isothermal titration calorimetry (ITC) and transient phosphorescence anisotropy (TPA) confirmed that these compounds bind to cMyBP-C, but not to actin. TPA results were also consistent with these compounds inhibiting C0-C2 binding to actin. We conclude that the actin-cMyBP-C fluorescence lifetime assay permits detection of pharmacologically active compounds that affect cMyBP-C-actin binding. We now have, for the first time, a validated high-throughput screen focused on cMyBP-C, a regulator of cardiac muscle contractility and known key factor in heart failure.

Atypical kinetics of cytochrome P450 2J2: Epoxidation of arachidonic acid and reversible inhibition by xenobiotic inhibitors

Extrahepatic CYP2J2 metabolism of arachidonic acid (AA) to bioactive regioisomeric epoxyeicosatrienoic acids (EETs) is implicated in both physiological and pathological conditions. Here, we aimed to characterize atypical substrate inhibition kinetics of this endogenous metabolic pathway and its reversible inhibition by xenobiotic inhibitors when AA is used as the physiologically-relevant substrate vis-à-vis conventional probe substrate astemizole (AST). As compared to typical Michaelis-Menten kinetics observed for AST, complete substrate inhibition was observed for CYP2J2 metabolism of AA to 14,15-EET whereby velocity of the reaction declined significantly at concentrations of AA above 20-30 µM with an estimated substrate inhibition constant (K_s) of 31 µM. In silico sequential docking of two AA substrates to orthosteric (OBS) and adjacent secondary binding sites (SBS) within a 3-dimensional homology model of CYP2J2 revealed favorable and comparable binding poses of glide-scores -3.1 and -3.8 respectively. Molecular dynamics (MD) simulations ascertained CYP2J2 conformational stability with dual AA substrate binding as time-dependent root mean squared deviation (RMSD) of protein Cα atoms and ligand heavy atoms stabilized to a plateau in all but one trajectory (n=6). The distance between heme-iron and ω6 (C14, C15) double bond of AA in OBS also increased from 7.5 ± 1.4 Å to 8.5 ± 1.8 Å when CYP2J2 was simulated with only AA in OBS versus the presence of AA in both OBS and SBS (p<0.001), supporting the observed in vitro substrate inhibition phenomenon. Poor correlation was observed between inhibitory constants (K_i) determined for a panel of nine competitive and mixed mode xenobiotic inhibitors against CYP2J2 metabolism of AA as compared to AST, whereby 4 out of 9 drugs had a greater than 5-fold difference between K_i values. Nonlinear Eadie-Hofstee plots illustrated that complete substrate inhibition of CYP2J2 by AA was not attenuated even at high concentrations of xenobiotic inhibitors which further corroborates that CYP2J2 may accommodate three or more ligands simultaneously. In light of the atypical kinetics, our results highlight the importance of using physiologically-relevant substrates in in vitro enzymatic inhibition assays for the characterization of xenobiotic-endobiotic interactions which is applicable to other complex endogenous metabolic pathways beyond CYP2J2 metabolism of AA to EETs. The accurate determination of K_i would further facilitate the association of xenobiotic-endobiotic interactions to observed therapeutic or toxic outcomes.

Coagulation-Inspired Direct Fibrinogen Assay Using Plasmonic Nanoparticles Functionalized with Red Blood Cell Membranes

The fast measurement of fibrinogen is essential in evaluating life-threatening sepsis and cardiovascular diseases. Here, we aim to utilize biomimetic plasmonic Au nanoparticles using red blood cell membranes (RBCM-AuNPs) and demonstrate nanoscale coagulation-inspired fibrinogen detection via cross-linking between RBCM-AuNPs. The proposed biomimetic RBCM-AuNPs are highly suitable for fibrinogen detection because hemagglutination, occurring in the presence of fibrinogen, induces a shift in the localized surface plasmon resonance of the NPs. Specifically, when the two ends of the fibrinogen protein are bound to receptors on separate RBCM-AuNPs, cross-linking of the RBCM-AuNPs occurs, yielding a corresponding plasmon shift within 10 min. This coagulation-inspired fibrinogen detection method, with a low sample volume, high selectivity, and high speed, could facilitate the diagnosis of sepsis and cardiovascular diseases.

Do we really understand how drug eluted from stents modulates arterial healing?

The advent of drug-eluting stents (DES) has revolutionised the treatment of coronary artery disease. These devices, coated with anti-proliferative drugs, are deployed into stenosed or occluded vessels, compressing the plaque to restore natural blood flow, whilst simultaneously combating the evolution of restenotic tissue. Since the development of the first stent, extensive research has investigated how further advancements in stent technology can improve patient outcome. Mathematical and computational modelling has featured heavily, with models focussing on structural mechanics, computational fluid dynamics, drug elution kinetics and subsequent binding within the arterial wall; often considered separately. Smooth Muscle Cell (SMC) proliferation and neointimal growth are key features of the healing process following stent deployment. However, models which depict the action of drug on these processes are lacking. In this article, we start by reviewing current models of cell growth, which predominantly emanate from cancer research, and available published data on SMC proliferation, before presenting a series of mathematical models of varying complexity to detail the action of drug on SMC growth in vitro. Our results highlight that, at least for Sodium Salicylate and Paclitaxel, the current state-of-the-art nonlinear saturable binding model is incapable of capturing the proliferative response of SMCs across a range of drug doses and exposure times. Our findings potentially have important implications on the interpretation of current computational models and their future use to optimise and control drug release from DES and drug-coated balloons.

The Roles of Membrane Technology in Artificial Organs: Current Challenges and Perspectives

The recent outbreak of the COVID-19 pandemic in 2020 reasserted the necessity of artificial lung membrane technology to treat patients with acute lung failure. In addition, the aging world population inevitably leads to higher demand for better artificial organ (AO) devices. Membrane technology is the central component in many of the AO devices including lung, kidney, liver and pancreas. Although AO technology has improved significantly in the past few decades, the quality of life of organ failure patients is still poor and the technology must be improved further. Most of the current AO literature focuses on the treatment and the clinical use of AO, while the research on the membrane development aspect of AO is relatively scarce. One of the speculated reasons is the wide interdisciplinary spectrum of AO technology, ranging from biotechnology to polymer chemistry and process engineering. In this review, in order to facilitate the membrane aspects of the AO research, the roles of membrane technology in the AO devices, along with the current challenges, are summarized. This review shows that there is a clear need for better membranes in terms of biocompatibility, permselectivity, module design, and process configuration.

Modeling and Parameter Subset Selection for Fibrin Polymerization Kinetics with Applications to Wound Healing

During the hemostatic phase of wound healing, vascular injury leads to endothelial cell damage, initiation of a coagulation cascade involving platelets, and formation of a fibrin-rich clot. As this cascade culminates, activation of the protease thrombin occurs and soluble fibrinogen is converted into an insoluble polymerized fibrin network. Fibrin polymerization is critical for bleeding cessation and subsequent stages of wound healing. We develop a cooperative enzyme kinetics model for in vitro fibrin matrix polymerization capturing dynamic interactions among fibrinogen, thrombin, fibrin, and intermediate complexes. A tailored parameter subset selection technique is also developed to evaluate parameter identifiability for a representative data curve for fibrin accumulation in a short-duration in vitro polymerization experiment. Our approach is based on systematic analysis of eigenvalues and eigenvectors of the classical information matrix for simulations of accumulating fibrin matrix via optimization based on a least squares objective function. Results demonstrate robustness of our approach in that a significant reduction in objective function cost is achieved relative to a more ad hoc curve-fitting procedure. Capabilities of this approach to integrate non-overlapping subsets of the data to enhance the evaluation of parameter identifiability are also demonstrated. Unidentifiable reaction rate parameters are screened to determine whether individual reactions can be eliminated from the overall system while preserving the low objective cost. These findings demonstrate the high degree of information within a single fibrin accumulation curve, and a tailored model and parameter subset selection approach for improving optimization and reducing model complexity in the context of polymerization experiments.

Optimizing Aminoglycoside Dosing Regimens for Critically Ill Pediatric Patients with Augmented Renal Clearance: a Convergence of Parametric and Nonparametric Population Approaches

Augmented renal clearance (ARC) can occur in critically ill pediatric patients receiving aminoglycosides such as gentamicin and tobramycin, yet optimal dosing strategies for ARC are undefined. We evaluated the probability of achieving efficacious or toxic exposures in pediatrics. Parallel population modeling of concentration strategies were pursued using Pmetrics v1.5.2 (nonparametric) and Monolix v2019R2 (parametric). Bayesian exposures were used to classify ARC based on total clearance (CL). The effects of serum creatinine (SCR), creatinine clearance (CRCL), total body weight (TBW), postnatal age (PNA), and ARC were explored as covariates. The probabilities of target attainment (PTA) (i.e., maximum concentration [C _max]/MIC, area under the concentration-time curve [AUC]/MIC) and of toxic exposure (PTE) (i.e., minimum concentration [C _min] > 2 μg/ml) were calculated according to PNA and ARC. A total of 123 patients (1 to 21 years old, 56% female) contributed 304 concentrations. A two-compartment model was superior to a one-compartment model in both approaches. Bayesian posterior predicted concentrations from the nonparametric base model fit the data well (R ² = 0.96) and classified 34 patients as having ARC (28%). Both the nonparametric and parametric approaches resulted in allometrically scaling of TBW on volume (V) and clearance (CL). ARC modified CL and central V. CRCL and a maturation function modified CL. ARC was associated with a 1.49- versus 1.66-fold increase in CL and a 1.56- versus 1.66-fold increase in the central V (nonparametric versus parametric). A high dose of 12 mg/kg of body weight/day was required to achieve adequate PTA when MICs were 1 to 2 μg/ml; ARC lowered achievable MICs. When PNA was <2 years, PTE was increased. Aminoglycoside monotherapy should be avoided in critically ill pediatric patients with ARC when MICs exceed 1 μg/ml, as optimal exposures are unachievable with standard dosing.

Synthesis of a High Affinity Complementary Peptide-Polymer Nanoparticle (NP) Pair Using Phage Display

Peptide-polymer complementary pairs can provide useful tools for isolating, organizing, and separating biomacromolecules. We describe a procedure for selecting a high affinity complementary peptide-polymer nanoparticle (NP) pair using phage display. A hydrogel copolymer nanoparticle containing a statistical distribution of negatively charged and hydrophobic groups was used to select a peptide sequence from a phage displayed library of >1010 peptides. The NP has low nanomolar affinity for the selected cyclic peptide and exhibited low affinity for a panel of diverse proteins and peptide variants. Affinity arises from the complementary physiochemical properties of both NP and peptide as well as the specific peptide sequence. Comparison of linear and cyclic variants of the peptide established that peptide structure also contributes to affinity. These findings offer a general method for identifying polymer-peptide complementary pairs. Significantly, precise polymer sequences (proteins) are not a requirement, a low information statistical copolymer can be used to select for a specific peptide sequence with affinity and selectivity comparable to that of an antibody. The data also provides evidence for the physiochemical and structural contributions to binding. The results confirm the utility of abiotic, statistical, synthetic copolymers as selective, high affinity peptide affinity reagents.