Adsorption of simple fluid on silica surface and nanopore: effect of surface chemistry and pore shape

This paper reports a molecular simulation study on the adsorption of simple fluids (argon at 77 K) on hydroxylated silica surfaces and nanopores. The effect of surface chemistry is addressed by considering substrates with either partially or fully hydroxylated surfaces. We also investigate the effect of pore shape on adsorption and capillary condensation by comparing the results for cylindrical and hexagonal nanopores having equivalent sections (i.e., equal section areas). Due to the increase in the polarity of the surface with the density of OH groups, the adsorbed amounts for fully hydroxylated surfaces are found to be larger than those for partially hydroxylated surfaces. Both the adsorption isotherms for the cylindrical and hexagonal pores conform to the typical behavior observed in the experiments for adsorption/condensation in cylindrical nanopores MCM-41. Capillary condensation occurs through an irreversible discontinuous transition between the partially filled and the completely filled configurations, while evaporation occurs through the displacement at equilibrium of a hemispherical meniscus along the pore axis. Our data are also used to discuss the effect of surface chemistry and pore shape on the BET method. The BET surface for fully hydroxylated surfaces is much larger (by 10-20%) than the true geometrical surface. In contrast, the BET surface significantly underestimates the true surface when partially hydroxylated surfaces are considered. These results suggest that the surface chemistry and the choice of the system adsorbate/adsorbent is crucial in determining the surface area of solids using the BET method.     

Highly selective preconcentration of ultra-trace cadmium by yeast surface engineering

The potential of selective cell-sorption for separation/preconcentration of ultra-trace heavy metals was exploited by surface engineering of Saccharomyces cerevisiae cells. The general idea is to display the cadmium-binding peptide on the cell surface in order to enhance the covalent interaction between cadmium and the yeast cells. By immobilizing the surface-engineered yeast cells onto cytopore(?) microcarrier beads for cadmium adsorption, we demonstrated that with respect to the native yeast 600-fold and 25-1000-fold improvements were observed respectively for the tolerance of ionic strength and the tolerant capability toward various metal cations after surface engineering. Based on these observations, a novel procedure for selective cadmium preconcentration was developed with detection by graphite furnace atomic absorption spectrometry (GFAAS), employing the engineered S. cerevisiae cell-loaded cytopore(?) beads as a renewable sorption medium incorporated into a sequential injection lab-on-valve system. The cadmium retained on the yeast cell surface was eluted with a small amount of nitric acid and quantified with GFAAS. Within a range of 5-100 ng L(-1) and a sample volume of 1 mL, an enrichment factor of 30 was achieved along with a detection limit of 1.1 ng L(-1), a sampling frequency of 20 h(-1) and a precision of 3.3% RSD at 50 ng L(-1). The procedure was validated by analyzing cadmium in certified reference materials and a series of environmental water samples.     

Complex surface engineering meets simple and beautiful surface chemistry

Surface chemistry of solids is the fundamental for processes on solid surfaces and properties of solid surfaces,such as heterogeneous catalysis,electrochemistry,corrosion,thin film growth,sensing,friction and lubrication[1].Understanding surface chemistry of solids is not only of great scientific interest,but also of important technological value for optimizing surface properties and processes.Due to the complexity of solid surface structures,it is challenging to unambiguously elucidate the surface chemistry of surface properties and processes at a molecular level.     

Rigidity versus amphiphilicity in transmembrane nanopore formation by cholate-based macrocycles

Amphiphilic macrocycles consisting of cholates and l-tryptophan were prepared by the copper-catalysed alkyne–azide cycloaddition. The macrocycles helped glucose permeate lipid bilayer membranes. The macrocycle with two cholates was significantly more active in the glucose transport than the one with three cholates. Inclusion of 30–50% cholesterol in the bilayer accelerated the glucose transport monotonously. The unusual cholesterol effect was explained by the hydrophobically driven pore formation, in which the associative interactions of the water molecules inside the macrocycles prompted the macrocycles to stack over one another to avoid unfavourable water–lipid hydrocarbon contact. Fluorescence quenching by water- and oil-soluble quenchers provided additional evidence for the better penetration of the dicholate macrocycle into the bilayers, consistent with the stacking model. Rigidity in the macrocycle structure was hypothesised to be the main reason for the higher transport activity and deeper membrane-penetration of the dicholate macrocycle compared with those of the tricholate.     

High-performance silicon nanopore hemofiltration membranes

Silicon micromachining provides the precise control of nanoscale features that can be fundamentally enabling for miniaturized, implantable medical devices. Concerns have been raised regarding blood biocompatibility of silicon-based materials and their application to hemodialysis and hemofiltration. A high-performance ultrathin hemofiltration membrane with monodisperse slit-shaped pores was fabricated using a sacrificial oxide technique and then surface-modified with poly(ethylene glycol) (PEG). Fluid and macromolecular transport matched model predictions well. Protein adsorption, fouling, and thrombosis were significantly inhibited by the PEG. The membrane retained hydraulic permeability and molecular selectivity during a 90-h hemofiltration experiment with anticoagulated bovine whole blood. This is the first report of successful prolonged hemofiltration with a silicon nanopore membrane. The results demonstrate feasibility of renal replacement devices based on these membranes and materials.     

Confined protein adsorption into nanopore arrays fabricated by colloidal-assisted polymer patterning

A combination of plasma surface modification of polymer thin films and colloidal nanosphere lithography was used to fabricate two-dimensional nanopore arrays as protein nanocontainers.     

Surface functionalization of nanoparticles for nanomedicine

Control of interactions between nanoparticles and biosystems is essential for the effective utilization of these materials in biomedicine. A wide variety of nanoparticle surface structures have been developed for imaging, sensing, and delivery applications. In this research Highlight, we will emphasize advances in tailoring nanoparticle interfaces for implementation in nanomedicine.     

Pore surface engineering of microporous coordination polymers

Pore surface control of microporous coordination polymers is of great interest due to the potentially exciting functionalities it presents, such as highly selective separation, chemisorption, and novel catalysts and sensors. A discussion of our unique strategy aimed at surface engineering using metalloligands, i.e., introduction of coordinatively unsaturated metal centers, is presented.     

Macrophage-targeted nanomedicine for chronic diseases immunotherapy

Macrophage is the key innate immune effector in first-line defense against the pathogens, and can be polarized into different phenotypes to regulate a variety of immunological functions. However, the plasticity of macrophage is extraordinarily recruited, activated, and polarized under pathological conditions,playing paramount roles in occurrence, development, and prognosis of various chronic diseases, such as rheumatoid arthritis(RA), atherosclerosis(AS), and cancer. To this end, macrophage has ...     

New surface improvement techniques for engineering plastics

Sputter etching process and reactive sputter etching process in radio frequency(RF)glow discharge for surface improvement technique of engineering plastics, especially P T F E (polytetrafluoroethylene) were studied. In the case of sputter etching in Ar gas. characteristic cone like structures were developed on the P T F E surface, resulting in improvement of adhesive property. In reactive sputter etching in H₂O gas, the P T F E surface changed chemically and showed wettability.     

Biopolymers for surface engineering of paper-based products

The combination of biopolymer science and technology with surface engineering of paper-based cellulosic materials has a lot of potential in stepping forward to a sustainable future. Various biopolymers such as oxidized starch, carboxymethyl cellulose, and polylatic acid have been commercially used to engineer paper surface. The paper-based cellulosic products are widely used for printing/writing and packaging applications. However, the production of these products are currently dependent mainly upon the use of petroleum-based materials including synthetic pigment coating latexes and barrier coating materials. The major challenges associated with some biopolymers are their relatively high costs and unsatisfactory performances. Continuing efforts are being made to enable the increased and value-added use of various biopolymers in paper surface engineering. These polymers can be based on cellulose, hemicelluloses, chitosan, alginate, protein, polylactic acid, and polyhydroxyalkanoate. The biopolymer-engineered paper products can be tailored for use as substitutes for various non-renewable materials including plastics and metals as well. Future development in the area of biopolymers for paper surface engineering is likely to lead to new possibilities and breakthroughs, paving the way for a substantially sustainable and green future.     

Nanowell-array surfaces prepared by argon plasma etching through a nanopore alumina mask

A method for preparing a glass surface containing an ordered array of nanowells is described. These nanowell arrays are prepared via a plasma-etch method using a nanopore alumina film as the etch mask. A replica of the pore structure of the alumina mask is etched into the glass. We demonstrate that chemical information in the form of negatively charged latex nanoparticles can be selectively stored within these nanowells and not indiscriminately deposited on the surface surrounding the nanowells. To accomplish this, the chemistry of the glass surfaces within these nanowells (walls and bottoms) must be different from the chemistry of the surface surrounding the nanowells. Two different procedures were developed to make the inside vs. surrounding surface chemistries different. Atomic force microscopy (AFM) was used to image the nanowells and, via friction-force measurements, to prove that the inner nanowell surfaces can be made chemically different from the surface surrounding the nanowells.     

MDM2-Associated Clusterization-Triggered Emission and Apoptosis Induction Effectuated by a Theranostic Spiropolymer

Heteroatom-containing spiropolymers were constructed in a facile manner by a catalyst-free multicomponent spiropolymerization route. P1a2b as the most potent of these spiropolymers, demonstrates cluster-triggered emission resulting from strong interactions with the MDM2 protein. By preventing the anti-apoptotic p53/MDM2 interaction, P1a2b triggers apoptosis in cancerous cells, while demonstrating a good biocompatibility and non-toxicity in non-cancerous cells. The combined results from solution and cell-based cluster-triggered emission studies, docking, protein expression experiments and cytotoxicity data strongly support the MDM2-binding hypothesis and indicate a potential application as a fluorescent cancer marker as well as therapeutic for this spiropolymer.     

Error analysis of idealized nanopore sequencing

This numerical study provides an error analysis of an idealized nanopore sequencing method in which ionic current measurements are used to sequence intact single‐stranded DNA in the pore, while an enzyme controls DNA motion. Examples of systematic channel errors when more than one nucleotide affects the current amplitude are detailed, which if present will persist regardless of coverage. Absent such errors, random errors associated with tracking through homopolymer regions are shown to necessitate reading known sequences (Escherichia coli K‐12) at least 140 times to achieve 99.99% accuracy (Q40). By exploiting the ability to reread each strand at each pore in an array, arbitrary positioning on an error rate versus throughput tradeoff curve is possible if systematic errors are absent, with throughput governed by the number of pores in the array and the enzyme turnover rate.     

Cell surface engineering with polyelectrolyte multilayer thin films

Layer-by-layer assembly of polyelectrolyte multilayer (PEM) films represents a bottom-up approach for re-engineering the molecular landscape of cell surfaces with spatially continuous and molecularly uniform ultrathin films. However, fabricating PEMs on viable cells has proven challenging owing to the high cytotoxicity of polycations. Here, we report the rational engineering of a new class of PEMs with modular biological functionality and tunable physicochemical properties which have been engineered to abrogate cytotoxicity. Specifically, we have discovered a subset of cationic copolymers that undergoes a conformational change, which mitigates membrane disruption and facilitates the deposition of PEMs on cell surfaces that are tailorable in composition, reactivity, thickness, and mechanical properties. Furthermore, we demonstrate the first successful in vivo application of PEM-engineered cells, which maintained viability and function upon transplantation and were used as carriers for in vivo delivery of PEMs containing biomolecular payloads. This new class of polymeric film and the design strategies developed herein establish an enabling technology for cell transplantation and other therapies based on engineered cells.     

Hydrogen peroxide-generating nanomedicine for enhanced chemodynamic therapy

Chemodynamic therapy(CDT) is an emerging endogenous stimulation activated tumor treatment approach that exploiting iron-containing nanomedicine as catalyst to convert hydrogen peroxide(H_2O_2)into toxic hydroxyl radical(·OH) through Fenton reaction.Due to the unique characteristics(weak acidity and the high H_2O_2 level) of the tumor microenvironment,CDT has advantages of high selectivity and low side effect.However,as an important substrate of Fenton reaction,the endogenous H_2O_2 in tumor is still insufficient,which may be an important factor limiting the efficacy of CDT.In order to optimize CDT,various H_2O_2-generating nanomedicines that can promote the production of H_2O_2 in tumor have been designed and developed for enhanced CDT.In this review,we summarize recently developed nanomedicines based on catalytic enzymes,nanozymes,drugs,metal peroxides and bacteria.Finally,the challenges and possible development directions for further enhancing CDT are prospected.     

Tuning the release rate of volatile molecules by pore surface engineering in metal-organic frameworks

Encapsulation and controlled release of volatile molecules such as fragrances in a designed manner is important but challenging for the flavor and fragrance industry. Here, we report the tuning release of volatile molecules by postsynthetic modification of an amine-terminated metal-organic framework(MOF) MIL-101-NH_2. By amidation, we obtained three MIL-101 MOFs, the trimethylacetamideterminated TC-MIL-101, the benzamide-terminated BC-MIL-101, and the oxalic acid monoamideterminated OC-MIL-101. All the MOFs can efficiently encapsulate volatile molecules. Moreover, we demonstrate that the release profile of volatiles can be widely tuned to sustain the release in several days to months and even over a year using different modified MIL-101 MOFs. We show that the release profiles are correlated with the binding energies between the guest volatiles and pores in MOFs. The pore diffusion and the synergistic transport are the rate-limiting step of the guest molecules from the modified MOFs.