Influence of porosity and microstructure on compression behavior of methacrylate polymers in flow-through applications.

Mechanical properties of a material play a pivotal role in its performance when such porous material is used in a flow-through mode. This study delves into the effect of porosity and microstructure on the compressibility of methacrylate polymer, focusing on two distinct microstructures: cauliflower and high internal phase emulsion. Samples with various porosities yet identical chemical composition were prepared and their Young's modulus was measured. The effect of porosity on Young's modulus was described by an exponential law model with the cauliflower microstructure exhibiting an exponent of 3.61, while the high internal phase emulsion of only 1.86. A mathematical analysis of the compression caused by a liquid flow unveiled significant disparities in the porosity threshold where minimal compression is observed, being around 0.45 for the cauliflower while there is monotone decrease in compression with porosity increase for the high internal phase emulsion microstructure. Evaluating exponent integer values between 1 and 5 over entire porosity range reveals that the porosity where the minimal compression occurs increases with a decrease in exponent value, being approximately 0.33 for n = 5, 0.4 for n = 4, 0.55 for n = 3, 0.65 for n = 2 while no minimum occurs for n = 1. These findings indicate that lower exponent value results in lower compression under identical experimental conditions.

Heart failure and excess mortality after aortic valve replacement in aortic stenosis.

INTRODUCTION: In aortic stenosis (AS), the heart transitions from adaptive compensation to an AS cardiomyopathy and eventually leads to decompensation with heart failure. Better understanding of the underpinning pathophysiological mechanisms is required in order to inform strategies to prevent decompensation. AREAS COVERED: In this review, we therefore aim to appraise the current pathophysiological understanding of adaptive and maladaptive processes in AS, appraise potential avenues of adjunctive therapy before or after AVR and highlight areas of further research in the management of heart failure post AVR. EXPERT OPINION: Tailored strategies for the timing of intervention accounting for individual patient's response to the afterload insult are underway, and promise to guide better management in the future. Further clinical trials of adjunctive pharmacological and device therapy to either cardioprotect prior to intervention or promote reverse remodeling and recovery after intervention are needed to mitigate the risk of heart failure and excess mortality.

Rapid, Direct, Noninvasive Method to Determine the Amount of Immobilized Protein.

Protein immobilization is of utmost importance in many areas, where various proteins are used for selective detection of target compounds. Despite the importance given to determine the amount of immobilized protein, there is no simple method that allows direct, noninvasive detection. In this work, a method based on pH transition, occurring during change of solution ionic strength, was developed. The method utilized the ionic character of the immobilized protein while implementing biologically compatible buffers. Five different proteins, namely, glucose oxidase, horseradish peroxidase, bovine serum albumin, lysozyme, and protein A, were immobilized in different amounts on a porous polymeric matrix, and their pH transition was measured using lactate buffer of various concentrations and pH values. A linear correlation was found between the amount of immobilized protein and the amplitude of the pH transition, allowing the detection down to 2 nmol of immobilized protein. By changing the buffer concentration and pH, the sensitivity of the method could be tailored. Criteria based on the symmetry of the pH transition peak have been developed to determine if a particular measurement is within a linear range. In addition, a mathematical model was developed enabling prediction of pH transition profiles based solely on the protein amino acid sequence, the buffer pKa value(s), and the amount of immobilized protein.Hence, it can be used to design pH transition method experiments to achieve the required sensitivity for a target sample. Since the proposed method is noninvasive, it can be routinely applied during optimization of the immobilization protocol, for quality control, and also as an in-process monitoring tool.

Simple and Tailorable Synthesis of Silver Nanoplates in Gram Quantities.

Due to plasmonic and catalytic properties, silver nanoplates are of significant interest; therefore, their simple preparation in gram quantities is required. Preferably, the method is seedless, consists of few reagents, enables preparation of silver nanoplates with desired optical properties in high concentration, is scalable, and allows their long-term storage. The developed method is based on silver nitrate, sodium borohydride, polyvinylpyrrolidone, and H2O2 as the main reagents, while antifoam A204 is implemented to achieve better product quality on a larger scale. The effect of each component was evaluated and optimized. Solution volumes from 3 to 450 mL and concentrations of silver nanoplates from 0.88 to 4.8 g/L were tested. Their size was tailored from 25 nm to 8 µm simply by H2O2 addition, covering the entire visible plasmon spectra and beyond. They can be dried and spontaneously dispersed after at least one month of storage in the dark without any change in plasmonic properties. Their potential use in modern art was demonstrated by drying silver colloids on different surfaces in the presence of reagents or purified, resulting in a variety of colors but, more importantly, patterns of varying complexity, from simple multi-coffee-rings structures to dendritic forms and complex multilevel Sierpinski triangle fractals.

Noninvasive method for determination of immobilized protein A.

The pH transition method, developed for the determination of the ion-exchange group density on chromatographic stationary phase, was used for the quantification of immobilized protein A. Monolithic epoxy polyHIPE and particulate CNBr-Sepharose supports were used for immobilization. A lactate buffer was selected, having a buffer capacity peak approximately 0.5 pH units below the maximum buffer capacity of protein A. The pH transition measurements were performed at pH 4.3, where protein A exhibits maximum buffer capacity, with a lactate buffer concentration of 1 mM for protein A immobilized on polyHIPE monoliths and of 5 mM for protein A immobilized on CNBr-Sepharose. The pH transition height and full width at half maximum for the particulate support and the height for the polyHIPE matrix, showed a linear correlation with the amount of immobilized protein A determined from the absorbance difference before and after immobilization for both supports. The developed method allows a simple, non-invasive on-line determination of immobilized protein A using biological buffers, even for chromatographic columns with an amount of immobilized protein A as low as 0.25 mg. In addition, its sensitivity and duration can be easily adjusted by varying the buffer concentration and pH.

Bacteriophage Delivery Systems Based on Composite PolyHIPE/Nanocellulose Hydrogel Particles.

The role of bacteriophage therapy in medicine has recently regained an important place. Oral phage delivery for gastrointestinal treatment, transport through the stomach, and fast release in the duodenum is one of such applications. In this work, an efficient polyHIPE/hydrogel system for targeted delivery of bacteriophages with rapid release at the target site is presented. T7 bacteriophages were encapsulated in low crosslinked anionic nanocellulose-based hydrogels, which successfully protected phages at pH < 3.9 (stomach) and completely lost the hydrogel network at a pH above 3.9 (duodenum), allowing their release. Hydrogels with entrapped phages were crosslinked within highly porous spherical polyHIPE particles with an average diameter of 24 µm. PolyHIPE scaffold protects the hydrogels from mechanical stimuli during transport, preventing the collapse of the hydrogel structure and the unwanted phage release. On the other hand, small particle size, due to the large surface-to-volume ratio, enables rapid release at the target site. As a consequence, a fast zero-order release was achieved, providing improved patient compliance and reduced frequency of drug administration. The proposed system therefore exhibits significant potential for a targeted drug delivery in medicine and pharmacy.

Non-invasive determination of ionizable ligand group density on high internal phase emulsion derived polymer.

Stepwise change between low and high salt concentration buffers of the same pH results in pH transition, the length of which was demonstrated to be proportional to the quantity of ion-exchange groups present on the matrix. In this work, we analyzed the effect of the ligand type, density, and buffer concentration on the pH transition shape for typical ion-exchange groups (QA, DEAE, SO3, and COOH) and ligands acting as metal-chelators, such as IDA, TAEA, and EDA. It was demonstrated that pH transition can occur either as a chromatographic or flat-top peak. pH transition peaks were evaluated by their length, height, and peak center parameters. While no parameter can describe the ligand density accurately with a single linear correlation for both peak types, all parameters can be used for the description of one peak type. Peak length and height exhibited the same accuracy, while their sensitivity depended on the pH transition shape: length being more sensitive for the flat-top peaks, while height for the chromatographic peaks. pH height can be obtained faster, at lower elution volume, and seems to be more suitable for the determination of low amounts of ligand, when typically chromatographic peak type pH transitions occur.

Application of lectin immobilized on polyHIPE monoliths for bioprocess monitoring of glycosylated proteins.

In-process monitoring of glycosylated protein concentration becomes very important with the introduction of perfusion bioprocesses. Affinity chromatography based on lectins allows selective monitoring when carbohydrates are accessible on the protein surface. In this work, we immobilized lectin on polyHIPE type of monoliths and implemented it for bioprocess monitoring. A spacer was introduced to lectin, which increased binding kinetics toward Fc-fusion protein, demonstrated by bio-layer interferometry. Furthermore, complete desorption using 0.25 M galactose was shown. Affinity column exhibited linearity in the range between 0.5 and 8 mg/ml and flow-unaffected binding for the flow-rates between 0.5 and 8 ml/min. Long-term stability over at least four months period was demonstrated. No unspecific binding of culture media components, including host cell proteins and DNA, was detected. Results obtained by affinity column matched concentration values obtained by a reference method.

Flow-Through PolyHIPE Silver-Based Catalytic Reactor.

Catalytic reactors performing continuously are an important step towards more efficient and controllable processes compared to the batch operation mode. For this purpose, homogenous high internal phase emulsion polymer materials with an immobilized silver catalyst were prepared and used as a continuous plug flow reactor. Porous material with epoxide groups was functionalized to bear aldehyde groups which were used to reduce silver ions using Tollens reagent. Investigation of various parameters revealed that the mass of deposited silver depends on the aldehyde concentration as well as the composition of Tollens reagent. Nanoparticles formed on the pore surface showed high crystallinity with a cuboctahedra crystal shape and highly uniform surface coverage. The example of the 4-nitrophenol catalytic reduction in a continuous process was studied and demonstrated to be dependent on the mass of deposited silver. Furthermore, productivity increased with the volumetric silver density and flow rate, and it was preserved during prolonged usage and storage.