Intramolecular micellization and nanopatterning in pH- and thermo-responsive molecular brushes.

Conformational transitions and nanoscale self-organization triggered in double pH- and thermo-responsive molecular brushes by varying environmental conditions are studied by means of analytical mean-field theory and numerical Scheutjens-Fleer self-consistent field modelling. Such molecular brushes are composed of multiple thermo-responsive side chains end-grafted onto the main chain (backbone) and are capable of acquiring ionic charges via reversible (de)protonation of the monomer units. Competition of long-range Coulomb repulsion with short-range solvophobic interactions leads to complex patterns in the intramolecular self-organization of molecular brushes. In particular, we observed formation of pearl necklace-like structures with multiple dense nanodomains formed by weakly ionized collapsed side chains and stabilized by a fraction protruding into the solution and strongly ionized ones. Such structures are thermodynamically stable in a certain parameter range and can be termed as intramolecular micelles. The stimuli-induced intramolecular nanopatterning occurs via a sequence of quasi-first order phase transitions corresponding to splitting/fusion of collapsed domains accompanied by jumps in the average degree of ionization and macromolecular dimensions. A re-entrant sequence of transitions is observed when the salt concentration is used as a control parameter. These theoretical predictions provide guidelines for design of smart unimolecular devices, for example multicompartment nanocarriers of active substances or nanosensors.

Simulations of ionization equilibria in weak polyelectrolyte solutions and gels.

This article recapitulates the state of the art regarding simulations of ionization equilibria of weak polyelectrolyte solutions and gels. We start out by reviewing the essential thermodynamics of ionization and show how the weak polyelectrolyte ionization differs from the ionization of simple weak acids and bases. Next, we describe simulation methods for ionization reactions, focusing on two methods: the constant-pH ensemble and the reaction ensemble. After discussing the advantages and limitations of both methods, we review the existing simulation literature. We discuss coarse-grained simulations of weak polyelectrolytes with respect to ionization equilibria, conformational properties, and the effects of salt, both in good and poor solvent conditions. This is followed by a discussion of branched star-like weak polyelectrolytes and weak polyelectrolyte gels. At the end we touch upon the interactions of weak polyelectrolytes with other polymers, surfaces, nanoparticles and proteins. Although proteins are an important class of weak polyelectrolytes, we explicitly exclude simulations of protein ionization equilibria, unless they involve protein-polyelectrolyte interactions. Finally, we try to identify gaps and open problems in the existing simulation literature, and propose challenges for future development.

A self-consistent mean-field model for polyelectrolyte gels.

We present a novel approach to modeling polyelectrolyte gels, exploiting the analogy between star-branched polymers and polymer networks as a computationally inexpensive yet reliable alternative to full-scale simulations. In the numerical mean-field model of a star-like polymer we modify the boundary conditions to represent an infinite network. We validate the predictions of our new model against a coarse-grained simulation model. We also validate it against a phenomenological analytical model which has been previously shown to agree with simulations in a limited range of parameters. The mean-field model explicitly considers local density gradients and agrees with the simulation results in a broad range of parameters, beyond that of the analytical model. Finally, we use the mean-field model for predictions of the swelling behaviour of weak polyelectrolyte gels under different pH conditions. We demonstrate that the local density gradients are important and that the ionization of the weak polyelectrolyte gel is significantly suppressed. Under the studied conditions the effective pKA is about one unit higher than that of the free monomer. This shift in the effective pKA stems from the different pH values inside and outside the gel.

Interaction of a hydrophobic weak polyelectrolyte star with an apolar surface.

We consider star-like polymers with weak, that is, pH-dependent, hydrophobic polyelectrolyte arms. For low ionic strength conditions, a microphase-segregated quasimicellar structure is found, for which the star features a compact apolar core and a charged and swollen corona. This state is jump-like lost when the ionic strength is increased, i.e., at some intermediate ionic strength value. Using numerical self-consistent field modeling, we focus on the adsorption characteristics of these objects onto hydrophobic surfaces as a function of the ionic strength. In the quasimicellar state, the stars are attracted to the surface, albeit that, typically, an adsorption barrier is present. The strongest repulsion is found at intermediate ionic strength, where the star-like molecule is in a single-phase state and the barrier remains modest at both low and high ionic strength cases. Remarkably, it is possible that a star in a single swollen phase state is pushed into the quasimicellar state.

Prospective evaluation of intra-observer variability of the hydronephrosis index in sonographic examination of 44 patients with acute renal colic.

PURPOSE: The aim of our prospective designed study was to confirm the intra-observer agreement of assessments of the hydronephrosis index (HI) with a sonographic technique that potentially provides additional information in patients with acute renal colic (ARC). METHODS: Sonographic measurement of HI and valuation of common clinical criteria were performed in 44 consecutive patients presenting with unilateral stone-related ARC. HI of colic side was recorded twice in predefined time intervals. Intra-observer agreement was evaluated with the Spearman's rank correlation/rho (ρ) for attributive-metric characteristics. Data of HI-measurement on the colic side were compared with data of the unaffected side using t test. RESULTS: Intra-observer agreement was significant for HI in the colic side (ρ = 0.918, p < 0.001) and in the unaffected side (ρ = 0.826, p < 0.001). The mean HI between colic and unaffected side differed significantly on the first evaluation (85.2 vs. 93.7, respectively; p < 0.001) and on the second evaluation (85.1 vs. 93.6, respectively; p < 0.001) as well. CONCLUSIONS: The HI method is a slightly feasible examination method in patients presenting with stone-related renal colic. Moreover, it offers a solid discrimination between obstruction and non-obstruction. Our prospective trial illustrates HI as a reproducible method with a high-grade intra-observer agreement. However, potential change of values under medical expulsive therapy and coherency with the functionality of the obstructed kidney may lead to bias and therefore remain to be analyzed. Further studies to specify exact thresholds for this method and to state our findings are required.

Modeling the Phase Transition in Hydrophobic Weak Polyelectrolyte Gels under Compression.

One of the emerging water desalination techniques relies on the compression of a polyelectrolyte gel. The pressures needed reach tens of bars, which are too high for many applications, damage the gel and prevent its reuse. Here, we study the process by means of coarse-grained simulations of hydrophobic weak polyelectrolyte gels and show that the necessary pressures can be lowered to only a few bars. We show that the dependence of applied pressure on the gel density contains a plateau indicating a phase separation. The phase separation was also confirmed by an analytical mean-field theory. The results of our study show that changes in the pH or salinity can induce the phase transition in the gel. We also found that ionization of the gel enhances its ion capacity, whereas increasing the gel hydrophobicity lowers the pressure required for gel compression. Therefore, combining both strategies enables the optimization of polyelectrolyte gel compression for water desalination purposes.

Prospective evaluation of interobserver variability of the hydronephrosis index and the renal resistive index as sonographic examination methods for the evaluation of acute hydronephrosis.

OBJECTIVE: To confirm the reliability of assessements of the renal resistive index (RRI) and the hydronephrosis index (HI) comprising two sonographic techniques providing additional information in patients with acute renal colic. PATIENTS AND METHODS: Sonographic measurement of hydronephrosis and assessment of common clinical criteria was performed in 22 consecutive patients presenting with unilateral stone-related renal colic. RRI and HI were separately recorded by two investigators within a prospective study. Interobserver agreement and comparison of sonographic with computed tomography (CT) findings were assessed with the Cohen's kappa statistic (κ) for attributive ordinal characteristics and Spearman's rank correlation/rho (ρ) for attributive metric characteristics. RESULTS: There was a significant correlation between HI and the sonographically-evaluated grade of hydronephrosis, although not between RRI and the grade of hydronephrosis. For all procedures (RRI, HI, sonography and CT), significant differences between the symptomatic and the asymptomatic kidney were assessed. Interobserver agreement was excellent for the grade assessment of hydronephrosis by conventional sonography (κ = 0.82; P < 0.001), good to very good for HI (ρ = 0.60; P = 0.003) and acceptable to good for RRI (ρ = 0.49; P = 0.021). CONCLUSIONS: The RRI and HI methods are both easily practicable as stageless examination methods in patients presenting with stone-related renal colic, and both also reliably distinguish between obstruction and non-obstruction. Exact thresholds for both methods must still be defined based on further successive studies. Additionally, changes of values under medical expulsive therapy and correlation with the functional status of the obstructed kidney remain to be examined.

Water Desalination Using Polyelectrolyte Hydrogel: Gibbs Ensemble Modeling.

Polyelectrolyte hydrogels can absorb a large amount of water across an osmotic membrane as a result of their swelling pressure. On the other hand, the insoluble cross-linked hydrogel network enables dewatering under the influence of external (thermal and/or mechanical) stimuli. Moreover, from a thermodynamic perspective, a polyelectrolyte hydrogel is already an osmotic membrane. These properties designate hydrogels as excellent candidates for use in desalination, at the same time avoiding the use of expensive membranes. In this article, we present our recent theoretical study of polyelectrolyte hydrogel usage for water desalination. Employing a coarse-grained model and the Gibbs ensemble, we modeled the thermodynamic equilibrium between the coexisting gel phase and the supernate aqueous salt solution phase. We performed a sequence of step-by-step hydrogel swellings and compressions in open and closed systems, i.e., in equilibrium with a large and with a comparably small reservoir of aqueous solution. The swelling in an open system removes ions from the large reservoir, whereas the compression in a closed system decreases the salt concentration in the small reservoir. We modeled this stepwise process of continuous decrease of water salinity from seawater up to freshwater concentrations and estimated the energy cost of the process to be comparable to that of reverse osmosis.

Hairy Gels: A Computational Study.

We present results of MD and MC simulations of the equilibrium properties of swelling gels with comb-like or bottlebrush subchains and compare them to scaling-theory predictions. In accordance with theory, the simulation results demonstrate that swelling coefficient of the gel increases as a function of the polymerization degree of the main chains and exhibits a very weak maximum (or is virtually constant) as a function of the polymerization degree and grafting density of side chains. The bulk osmotic modulus passes through a shallow minimum as the polymerization degree of the side chains increases. This minimum is attributed to the onset of overlap of side chains belonging to different bottlebrush strands in the swollen gel.

Reversible multilayered vesicle-like structures with fluid hydrophobic and interpolyelectrolyte layers.

Hydrophobic blocks of amphiphilic block copolymers often form glassy micellar cores at room temperature with a rigid structure that limits their applications as nanocapsules for targeted delivery. Nevertheless, we prepared and analyzed core/shell micelles with a soft core, formed by a self-assembled block copolymer consisting of a hydrophobic block and a polycation block, poly(lauryl acrylate)-block-poly(trimethyl-aminoethyl acrylate) (PLA-QPDMAEA), in aqueous solution. By light and small-angle neutron scattering, by transmission electron microscopy and by fluorescence spectroscopy, we showed that these core/shell micelles are spherical and cylindrical with a fluid-like PLA core and a positively charged outer shell and that they can encapsulate and release hydrophobic solutes. Moreover, after mixing these PLA-QPDMAEA core/shell micelles with another diblock copolymer, consisting of a hydrophilic block and a polyanion block, namely poly(ethylene oxide)-block-poly(methacrylic acid) (PEO-PMAA), we observed the formation of novel vesicle-like multicompartment structures containing both soft hydrophobic and interpolyelectrolyte (IPEC) layers. By combining small-angle neutron scattering with self-consistent field modeling, we confirmed the formation of these complex vesicle-like structures with a swollen PEO core, an IPEC inner layer, a PLA soft layer, an IPEC outer layer and a loose PEO corona. Thus, these multicompartment micelles with fluid and IPEC layers and a hydrophilic corona may be used as nanocapsules with several tunable properties, including the ability to control the thickness of each layer, the charge of the IPEC layers and the stability of the micelles, to deliver both hydrophobic and multivalent solutes.

Subcapsular orchiectomy in the primary therapy of patients with bone metastasis in advanced prostate cancer: an anachronistic intervention?

Background. The therapeutic impact of palliative androgen deprivation in metastatic prostate cancer is indisputable. Bilateral orchiectomy represents the traditional method of AD but was reduced during the last years in favor for treatment with LHRH analogues. Due to limited economic resources of the health care system, the economically priced definite surgical castration might experience a renaissance. Methods. In this single-center retrospective study, 83 consecutive patients with osseous metastasized prostate cancer were evaluated, who had primarily been treated by subcapsular bilateral orchiectomy. Response to therapy, time until therapy failure, overall survival time, psychological disorders due to loss of organ, and disease-associated and postoperative surgical complications were recorded. The median followup was 35 months (IQR: 26-46). Results. Patients' mean age at surgery was 72.1 (54-91) years. Six patients (7.2%) displayed immediate tumor progression after orchiectomy. Median time of tumor remission and overall survival time were 29 and 36 months, respectively. 14% of the study group showed minor postoperative complications. No psychological problems occurred following bilateral orchiectomy. Conclusion. Due to an effective and persistent oncological effectiveness, less morbidity, and absence of psychological implications, bilateral subcapsular orchiectomy seems to be a practicable and advisable alternative in the first-line therapy of metastasized PCa.

[Value of radical oncological surgery in bilateral synchronous renal cell cancer and coincidental simultaneous prostate cancer]. / Die operative Strategie bei koinzidentem Auftreten eines bilateral synchronen Nierenzellkarzinoms und simultanen Prostatakarzinoms.

To date, the current literature does not report on oncological surgery in bilateral renal cell cancer and coincidental simultaneous prostate cancer. We present the case of a 66-year-old patient presenting as a challenge due to this oncological-surgical constellation. Based on the present case study and the postoperative follow-up, we discuss possible surgical strategies and demonstrate that, even in the case of multiple tumour locations, a satisfying oncological and functional long-term result is achievable.