Towards Enhanced Performance Thin-film Composite Membranes via Surface Plasma Modification

Advancing the design of thin-film composite membrane surfaces is one of the most promising pathways to deal with treating varying water qualities and increase their long-term stability and permeability. Although plasma technologies have been explored for surface modification of bulk micro and ultrafiltration membrane materials, the modification of thin film composite membranes is yet to be systematically investigated. Here, the performance of commercial thin-film composite desalination membranes has been significantly enhanced by rapid and facile, low pressure, argon plasma activation. Pressure driven water desalination tests showed that at low power density, flux was improved by 22% without compromising salt rejection. Various plasma durations and excitation powers have been systematically evaluated to assess the impact of plasma glow reactions on the physico-chemical properties of these materials associated with permeability. With increasing power density, plasma treatment enhanced the hydrophilicity of the surfaces, where water contact angles decreasing by 70% were strongly correlated with increased negative charge and smooth uniform surface morphology. These results highlight a versatile chemical modification technique for post-treatment of commercial membrane products that provides uniform morphology and chemically altered surface properties

Charge tunable thin-film composite membranes by gamma-ray triggered surface polymerization

Thin-film composite poly(amide) (PA) membranes have greatly diversified water supplies and food products. However, users would benefit from a control of the electrostatic interactions between the liquid and the net surface charge interface in order to benefit wider application. The ionic selectivity of the 100 nm PA semi-permeable layer is significantly affected by the pH of the solution. In this work, for the first time, a convenient route is presented to configure the surface charge of PA membranes by gamma ray induced surface grafting. This rapid and up-scalable method offers a versatile route for surface grafting by adjusting the irradiation total dose and the monomer concentration. Specifically, thin coatings obtained at low irradiation doses between 1 and 10 kGy and at low monomer concentration of 1 v/v% in methanol/water (1:1) solutions, dramatically altered the net surface charge of the pristine membranes from-25 mV to +45 mV, whilst the isoelectric point of the materials shifted from pH 3 to pH 7. This modification resulted in an improved water flux by over 55%, from 45.9 to up 70 L.m -2 .h -1 , whilst NaCl rejection was found to drop by only 1% compared to pristine membranes

Structure-Based Analysis of Five Novel Disease-Causing Mutations in 21-Hydroxylase-Deficient Patients

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is the most frequent inborn error of metabolism, and accounts for 90–95% of CAH cases. The affected enzyme, P450C21, is encoded by the CYP21A2 gene, located together with a 98% nucleotide sequence identity CYP21A1P pseudogene, on chromosome 6p21.3. Even though most patients carry CYP21A1P-derived mutations, an increasing number of novel and rare mutations in disease causing alleles were found in the last years. In the present work, we describe five CYP21A2 novel mutations, p.R132C, p.149C, p.M283V, p.E431K and a frameshift g.2511_2512delGG, in four non-classical and one salt wasting patients from Argentina. All novel point mutations are located in CYP21 protein residues that are conserved throughout mammalian species, and none of them were found in control individuals. The putative pathogenic mechanisms of the novel variants were analyzed in silico. A three-dimensional CYP21 structure was generated by homology modeling and the protein design algorithm FoldX was used to calculate changes in stability of CYP21A2 protein. Our analysis revealed changes in protein stability or in the surface charge of the mutant enzymes, which could be related to the clinical manifestation found in patients

Controlled biocide release from hierarchically-structured biogenic silica: surface chemistry to tune release rate and responsiveness.

Biocides are essential for crop protection, packaging and several other biosystem applications. Therein, properties such as tailored and controlled release are paramount in the development of sustainable biocide delivery systems. We explore the self-similar nano-organized architecture of biogenic silica particles to achieve high biocide payload. The high surface area accessibility of the carrier allowed us to develop an efficient, low energy loading strategy, reaching significant dynamic loadings of up to 100 mg·g-1. The release rate and responsiveness were tuned by manipulating the interfaces, using either the native hydroxyl surfaces of the carrier or systems modified with amines or carboxylic acids in high density. We thoroughly evaluated the impact of the carrier-biocide interactions on the release rate as a function of pH, ionic strength and temperature. The amine and carboxyl functionalization strategy led to three-fold decrease in the release rate, while higher responsiveness against important agro-industrial variables. Key to our discoveries, nanostructuring thymol in the biogenic silica endowed systems with controlled, responsive release promoting remarkable, high and localized biocidal activity. The interfacial factors affecting related delivery were elucidated for an increased and localized biocidal activity, bringing a new light for the development of controlled release systems from porous materials

Self-Assembled Stimuli-Responsive Polyrotaxane Core-Shell Particles

Thermodynamically assembled core-shell nanocarriers are potential candidates for drug delivery applications due to their submicrometer size and the ability to load drugs into their hydrophobic core. Herein, we describe the formation of core-shell particles that consist of noncovalent polymers, that is, polyrotaxanes (PRXs), that form an α-cyclodextrin (αCD) core surrounded by a corona of low-fouling poly(ethylene glycol) (PEG). The PRX core-shell particles are able to sequester small organic molecules, such as pyrene and calcein, releasing these small molecules during degradation. The small, cellular peptide, glutathione, was used to degrade the particles through the reductive cleavage of disulfide bonds that stabilize the individual PRX polymers. Cleavage of a single bond allows for the degradation of the supramolecular-polymer, making these PRX core-shell particles highly responsive. Furthermore, these particles demonstrate negligible cytotoxicity in mammalian cells, making them promising carriers for future drug delivery research

Nanoparticles assembled via pH-responsive reversible segregation of cyclodextrins in polyrotaxanes

Supramolecular polymers with monomers bound together by secondary interactions, such as polyrotaxanes (PRXs), consisting of alpha cyclodextrin (αCD) threaded onto poly(ethylene glycol) (PEG), have attracted interest as a result of their ability to overcome physical limitations present in conventional, covalently structured polymers. Herein, we describe the formation of pH-responsive supramolecular assemblies from carboxyethylester bearing αCD and PEG PRXs. These PRXs were formed using PEG of Mw 20 kDa and a threading degree of 28%. Upon charge neutralisation the threaded αCDs co-localise, resulting in aggregation of the PRXs and the formation of a suspension by self-assembly. This process is shown to be reversible and possible via the mobility of CDs along the PEG guest chain. As a result of the inherent properties of PRXs, such as enhanced multivalent interactions and degradation, these responsive supramolecular polymers are expected to be of interest in fields where PRX-based materials have already found application, including paints, self-healing materials, surface coatings, and polymer therapeutics

Protein Adsorption and Coordination-Based End-Tethering of Functional Polymers on Metal-Phenolic Network Films

Metal-phenolic network (MPN) coatings have generated increasing interest owing to their biologically inspired nature, facile fabrication, and near-universal adherence, especially for biomedical applications. However, a key issue in biomedicine is protein fouling, and the adsorption of proteins on tannic acid-based MPNs remains to be comprehensively studied. Herein, we investigate the interaction of specific biomedically relevant proteins in solution (e.g., bovine serum albumin (BSA), immunoglobulin G (IgG), fibrinogen) and complex biological media (serum) using layer-by-layer-assembled tannic acid/FeIII MPN films. When FeIII was the outermost layer, galloyl-modified poly(2-ethyl-2-oxazoline) (P(EtOx)-Gal) could be grafted to the films through coordination bonds. Protein fouling and bacterial adhesion were greatly suppressed after functionalization with P(EtOx)-Gal and the mass of adsorbed protein was reduced by 79%. Interestingly, larger proteins adsorbed more on both the MPNs and P(EtOx)-functionalized MPNs. This study provides fundamental information on the interactions of MPNs with single proteins, mixtures of proteins as encountered in serum, and the noncovalent, coordination-based, functionalization of MPN films

Boronate-Phenolic Network Capsules with Dual Response to Acidic pH and cis-Diols

Dual-responsive boronate-phenolic network (BPN) capsules are fabricated by the complexation of phenylborate and phenolic materials. The BPN capsules are stable in the presence of competing carbohydrates, but dissociate at acidic pH or in the presence of competing cis-diols at physiological pH. This engineered capsule system provides a platform for a wide range of biological and biomedical applications