Thermodynamics of complex coacervation Kayitmazer, A. Basak
Advances in colloid and interface science,
January 2017, 2017-Jan, 2017-01-00, 20170101, Letnik:
239
Journal Article
Recenzirano
Isothermal titration calorimetry has routinely been used to understand the thermodynamic characteristics of complexation and coacervation. Most commonly, built-in models that assume independent ...binding sites have been employed in these studies. However, the non-covalent nature of interactions and steric effects accompanying macromolecules require (i) usage of new models such as overlapping binding sites and Satake–Yang's two-state binding models and (ii) reformed interpretations of the data as two-stage structuring. Fitting data with these models, forces driving the interaction of polyelectrolytes with oppositely charged polyelectrolytes, surfactants, and proteins have been identified as electrostatics and/or counterion release with possible contributions from hydrogen bonding and hydrophobic interactions. Additionally, for surfactant–polyelectrolyte coacervation, ITC signals indicated separate regions for formation of polymer-induced micelles and free micelles. Regardless of the type of the coacervation system, thermodynamics of coacervation is affected by the following parameters: pH and ionic strength of the medium, charge density, molecular weight of the polyelectrolyte, concentration, and mixing order of macroions. Lastly, we present a brief comparison between ITC on one hand and surface plasmon resonance or capillary electrophoresis on the other regarding their application in coacervation.
•Interpretation of endothermic and/or exothermic signals encountered during complexation and coacervation.•Recommendations regarding ITC experimental design.•Various built-in and custom-made models to fit the ITC data are discussed.•Effect of different parameters on thermodynamics of coacervation.•Comparison of ITC with other techniques (surface plasmon resonance and capillary electrophoresis).
Polyelectrolyte-colloid coacervation could be viewed as a sub-category of complex coacervation, but is unique in (1) retaining the structure and properties of the colloid, and (2) reducing the ...heterogeneity and configurational complexity of polyelectrolyte–polyelectrolyte (PE–PE) systems. Interest in protein-polyelectrolyte coacervates arises from preservation of biofunctionality; in addition, the geometric and charge isotropy of micelles allows for better comparison with theory, taking into account the central role of colloid charge density. In the context of these two systems, we describe critical conditions for complex formation and for coacervation with regard to colloid and polyelectrolyte charge densities, ionic strength, PE molecular weight (MW), and stoichiometry; and effects of temperature and shear, which are unique to the PE-micelle systems. The coacervation process is discussed in terms of theoretical treatments and models, as supported by experimental findings. We point out how soluble aggregates, subject to various equilibria and disproportionation effects, can self-assemble leading to heterogeneity in macroscopically homogeneous coacervates, on multiple length scales.
Photothermal‐chemotherapeutic nanoparticles (NPs) are attracting increasing attention and becoming more widely used for cancer therapy in the clinic due to their noninvasiveness, notable tissue ...penetration abilities, and low systemic adverse effects. However, functional ligands are conventionally modified onto photothermal NPs to well stabilize the inorganic particles suffering from complex chemical modifications, low productivity, and batch‐to‐batch inconsistencies, and thus significantly restricting their clinical applications. Herein, flash nanoprecipitation (FNP) is taken advantage of to afford rapid and uniform mixing for generating local supersaturated CuS clusters for small and highly stable CuS NPs effectively stabilized by polyacrylic acid through a continuous strategy. It greatly reduces the complexity for CuS NPs synthesis and functionalization in a facile intensified mixing process. These as‐synthesized particles are high‐drug loading, scalable, and most importantly, it is easy to control their sizes and charges through external conditions. Toxicity and tumor inhibition experiments confirm the high cell toxicity and good suppression of tumor growth under near‐infrared irradiation indicating a promising prospect of FNP in the large‐scale and continuous yielding of highly stable and high‐performing photothermal‐chemotherapeutic NPs for cancer therapy.
The current synthesis methods and chemical functionalization for CuS nanoparticles (NPs) suffer from polydispersity, low yield, uncontrollability, and batch‐to‐batch inconsistency. Here, an emerging novel NP assembly technology‐flash nanoprecipitation is taken advantage of to prepare aqueous PAA‐CuS NPs with high‐DOX loading capacity and stabilized with polyacrylic acid in a continuous and largely scalable way. These particles are highly stable, high‐drug loading, scalable, and most importantly, easy to control.
Abstract
Pesticides are widely used to increase agricultural productivity, however, weak adhesion and deposition lead to low efficient utilization. Herein, we prepare a nanopesticide formulation ...(tebuconazole nanopesticides) which is leaf-adhesive, and water-dispersed via a rapid nanoparticle precipitation method, flash nanoprecipitation, using temperature-responsive copolymers poly-(2-(dimethylamino)ethylmethylacrylate)-
b
-poly(ε-caprolactone) as the carrier. Compared with commercial suspensions, the encapsulation by the polymer improves the deposition of TEB, and the contact angle on foliage is lowered by 40.0°. Due to the small size and strong van der Waals interactions, the anti-washing efficiency of TEB NPs is increased by 37% in contrast to commercial ones. Finally, the acute toxicity of TEB NPs to zebrafish shows a more than 25-fold reduction as compared to commercial formulation indicating good biocompatibility of the nanopesticides. This work is expected to enhance pesticide droplet deposition and adhesion, maximize the use of pesticides, tackling one of the application challenges of pesticides.
•Electrodeposited multilayered gradient coatings were successfully deposited with distinct and uniform layer thickness and subjected to physical and mechanical characterization.•Flow strength of ...multilayered Co-Sn gradient coating is higher than that of sole Co or Sn coating.•After compression, coating structure exhibit four distinctive layers instead of starting seven, due to elemental inter-mixing of intermediate thin layers as a stress accommodating mechanism.
Compositionally modulated multilayer (CMM) Co-Sn coating were successfully deposited with the help of electrodeposition on copper substrate. The coating microstructure was homogeneous, nanostructured in nature with smooth and distinct interfaces as confirmed by SEM and TEM investigation. In this study, micro-mechanical properties of such CMM Co-Sn coatings has been investigated by means of micro-pillar compression. Micro-mechanical properties of electrodeposited monolithic sole Co and sole Sn coatings was also investigated for comparison purpose. CMM Co-Sn coating shows high flow strength of about 330 MPa, which is about 1.2 and 5 times higher than that of sole Co and sole Sn coating, respectively. Such enhanced mechanical properties are the result of intermixing of several thin Co-Sn layers to form a single broad layer to accommodate deformation of material and to minimize system’s energy as evident by detail transmission electron microscopy investigation on deformed micro-pillars.
To delineate the full phenotypic spectrum, discriminative features, piloting longitudinal progression data, and sample size calculations of replication factor complex subunit 1 (RFC1) repeat ...expansions, recently identified as causing cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS).
Multimodal
repeat screening (PCR, Southern blot, whole-exome/genome sequencing-based approaches) combined with cross-sectional and longitudinal deep phenotyping in (1) cross-European cohort A (70 families) with ≥2 features of CANVAS or ataxia with chronic cough (ACC) and (2) Turkish cohort B (105 families) with unselected late-onset ataxia.
Prevalence of RFC1 disease was 67% in cohort A, 14% in unselected cohort B, 68% in clinical CANVAS, and 100% in ACC. RFC1 disease was also identified in Western and Eastern Asian individuals and even by whole-exome sequencing. Visual compensation, sensory symptoms, and cough were strong positive discriminative predictors (>90%) against RFC1-negative patients. The phenotype across 70 RFC1-positive patients was mostly multisystemic (69%), including dysautonomia (62%) and bradykinesia (28%) (overlap with cerebellar-type multiple system atrophy MSA-C), postural instability (49%), slow vertical saccades (17%), and chorea or dystonia (11%). Ataxia progression was ≈1.3 Scale for the Assessment and Rating of Ataxia points per year (32 cross-sectional, 17 longitudinal assessments, follow-up ≤9 years mean 3.1 years) but also included early falls, variable nonlinear phases of MSA-C-like progression (SARA points 2.5-5.5 per year), and premature death. Treatment trials require 330 (1-year trial) and 132 (2-year trial) patients in total to detect 50% reduced progression.
RFC1 disease is frequent and occurs across continents, with CANVAS and ACC as highly diagnostic phenotypes yet as variable, overlapping clusters along a continuous multisystemic disease spectrum, including MSA-C-overlap. Our natural history data help to inform future RFC1 treatment trials.
This study provides Class II evidence that RFC1 repeat expansions are associated with CANVAS and ACC.
Schizophrenia is one of the most common and complex neuropsychiatric disorders, which is contributed both by genetic and environmental exposures. Recently, it is shown that NRG1-mediated ErbB4 ...signalling regulates many important cellular and molecular processes such as cellular growth, differentiation and death, particularly in myelin-producing cells, glia and neurons. Recent association studies have revealed genomic regions of NRG1 and ERBB4, which are significantly associated with risk of developing schizophrenia; however, inconsistencies exist in terms of validation of findings between distinct populations. In this study, we aim to validate the previously identified regions and to discover novel haplotypes of NRG1 and ERBB4 using logistic regression models and Haploview analyses in three independent datasets from GWAS conducted on European subjects, namely, CATIE, GAIN and nonGAIN. We identified a significant 6-kb block in ERBB4 between chromosome locations 212,156,823 and 212,162,848 in CATIE and GAIN datasets (p = 0.0206 and 0.0095, respectively). In NRG1, a significant 25-kb block, between 32,291,552 and 32,317,192, was associated with risk of schizophrenia in all CATIE, GAIN, and nonGAIN datasets (p = 0.0005, 0.0589, and 0.0143, respectively). Fine mapping and FastSNP analysis of genetic variation located within significantly associated regions proved the presence of binding sites for several transcription factors such as SRY, SOX5, CEPB, and ETS1. In this study, we have discovered and validated haplotypes of ERBB4 and NRG1 in three independent European populations. These findings suggest that these haplotypes play an important role in the development of schizophrenia by affecting transcription factor binding affinity.
Abstract Synthetic nerve conduits represent a promising strategy to enhance functional recovery in peripheral nerve injury repair. However, the efficiency of synthetic nerve conduits is often ...compromised by the lack of molecular factors to create an enriched microenvironment for nerve regeneration. Here, we investigate the in vivo response of mono (MC) and bi-component (BC) fibrous conduits obtained by processing via electrospinning poly(ε-caprolactone) (PCL) and gelatin solutions. In vitro studies demonstrate that the inclusion of gelatin leads to uniform electrospun fiber size and positively influences the response of Dorsal Root Ganglia (DRGs) neurons as confirmed by the preferential extensions of neurites from DRG bodies. This behavior can be attributed to gelatin as a bioactive cue for the cultured DRG and to the reduced fibers size. However, in vivo studies in rat sciatic nerve defect model show an opposite response: MC conduits stimulate superior nerve regeneration than gelatin containing PCL conduits as confirmed by electrophysiology, muscle weight and histology. The G-ratio, 0.71 ± 0.07 for MC and 0.66 ± 0.05 for autograft, is close to 0.6, the value measured in healthy nerves. In contrast, BC implants elicited a strong host response and infiltrating tissue occluded the conduits preventing the formation of myelinated axons. Therefore, although gelatin promotes in vitro nerve regeneration, we conclude that bi-component electrospun conduits are not satisfactory in vivo due to intrinsic limits to their mechanical performance and degradation kinetics, which are essential to peripheral nerve regeneration in vivo.
Burr formation and its treatments—a review Jin, Song Yong; Pramanik, A.; Basak, A. K. ...
International journal of advanced manufacturing technology,
03/2020, Letnik:
107, Številka:
5-6
Journal Article
Recenzirano
Burrs, being one of the most undesired obstructions generated during machining, affects work piece quality negatively in many aspects. Although deburring removes burrs, this extra process is time ...consuming, costly and might affect dimensional accuracy. This study investigates mechanisms, effects and variations on burr formation in most common machining processes such as drilling, milling, turning and grinding based on the information available in literature. The problems related to burrs as well as ways and methods to remove burr and control or minimize burr formation has critically discussed. Burrs can be minimised by selecting proper tool geometry, tool materials, coolant, machining parameters, work piece material, process planning and tool path design. As there is no method that can eliminate burr formation, thus deburring is essential to eliminate burrs after machining. Manual tools, abrasive blasting, abrasive flow, magnetic abrasive finishing, centrifugal barrel finishing, thermal melting and electrochemical effect are most commonly used for deburring depending on material, size and precision of parts.
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