Increased demand for highly selective and energy-efficient separations processes has stimulated substantial interest in emerging two-dimensional (2D) nanomaterials as a potential platform for next-generation membranes. However, persistently poor separation performance continues to hinder the viability of many novel 2D-nanosheet membranes in desalination applications. In this study, we examine the role of the lamellar structure of 2D membranes on their performance. Using self-fabricated molybdenum disulfide (MoS2) membranes as a platform, we show that the separation layer of 2D nanosheet frameworks not only fails to demonstrate water-salt selectivity but also exhibits low rejection toward dye molecules. Moreover, the MoS2 membranes possess a molecular weight cutoff comparable to its underlying porous support, implying negligible selectivity of the MoS2 layer. By tuning the nanochannel size through intercalation with amphiphilic molecules and analyzing mass transport in the lamellar structure using Monte Carlo simulations, we reveal that small imperfections in the stacking of MoS2 nanosheets result in the formation of catastrophic microporous defects. These defects lead to a precipitous reduction in the selectivity of the lamellar structure by negating the interlayer sieving mechanism that prevents the passage of large penetrants. Notably, the imperfect stacking of nanosheets in the MoS2 membrane was further verified using 2D X-ray diffraction measurements. We conclude that developing a well-controlled fabrication process, in which the lamellar structure can be carefully tuned, is critical to achieving defect-free and highly selective 2D desalination membranes.

Relating Selectivity and Separation Performance of Lamellar Two-Dimensional Molybdenum Disulfide (MoS2) Membranes to Nanosheet Stacking Behavior.

A metal-chelating polymer (MCP) with a polyglutamide (PGlu) backbone presenting on average 13 DOTA (tetraazacyclododecane-1,4,7,10-tetraacetic acid) chelators for complexing 111In or 177Lu and 10 polyethylene glycol (PEG) chains to minimize liver and spleen uptake was conjugated to antiepidermal growth factor receptor (EGFR) monoclonal antibody (mAb), panitumumab. Because panitumumab-MCP may be dual-labeled with 111In and 177Lu for SPECT, or radioimmunotherapy (RIT) exploiting the Auger electrons or β-particle emissions, respectively, we propose that panitumumab-MCP could be a useful theranostic agent for EGFR-positive PnCa. Bioconjugation was achieved by reaction of a hydrazine nicotinamide (HyNIC) group on the MCP with an aryl aromatic aldehyde introduced into panitumumab by reaction with succinimidyl-4-formylbenzamide (S-4FB). The conjugation reaction was monitored by measurement of the chromophoric bis-aryl hydrazone bond formed (e350 nm = 24 500 M–1 cm–1) to achieve two MCPs/panitumumab. Labeling of ...

Panitumumab Modified with Metal-Chelating Polymers (MCP) Complexed to 111In and 177Lu-An EGFR-Targeted Theranostic for Pancreatic Cancer.

The solution behavior originating from molecular characteristics of synthetic macromolecules plays a pivotal role in many areas, in particular the life sciences. This situation necessitates the use of complementary hydrodynamic analytical methods as the only means for a complete structural understanding of any macromolecule in solution. To this end, we present a combined hydrodynamic approach for studying in-house prepared, low dispersity poly(ethylene glycols)s (PEGs), also known as poly(ethylene oxide)s (PEOs) depending on the classification used, synthesized from varying initiation sites by the living anionic ring opening polymerization. The series of linear PEGs in the molar mass range of only a few thousand to 50 000 g mol–1 have been studied in detail via viscometry and sedimentation-diffusion analysis by analytical ultracentrifugation. The obtained estimations for intrinsic viscosity, diffusion coefficients, and sedimentation coefficients of the macromolecules in the solution-based analysis clearly...

Hydrodynamic Analysis Resolves the Pharmaceutically-Relevant Absolute Molar Mass and Solution Properties of Synthetic Poly(ethylene glycol)s Created by Varying Initiation Sites.

Analytical ultracentrifugation was performed on poly(methacrylic acid) (PMAA) with a series of weight average molar masses (Mw) in aqueous solutions as a function of pH. The scales of the sedimentation coefficient (s) and the diffusion coefficient (D) to Mw at infinite dilutions were obtained at different pH values, indicating that PMAA chains adopt a collapsed structure at low pH values, and stretch at pH higher than 5.2. Our results show that the sedimentation coefficient exhibits a minimum at pH ∼ 6.0, presumably due to the effect of the conformational change and the hydration state of PMAA chains. When pH increases from 6.0 to 8.5, PMAA chains with high molar mass shrink a little bit, presumably because the sodium ions act as a bridging agent between nonadjacent carboxylate groups. Furthermore, the weight average molar mass of PMAA at pH 8.5 increases by one fold than that at pH 4.0, indicating the condensation of sodium ions and the increase in the number of hydration water molecules around carboxylate groups at high pH values.

Investigation of pH-induced conformational change and hydration of poly(methacrylic acid) by analytical ultracentrifugation

Poly(2-ethyl-2-oxazoline) (PEtOx), as an alternative polymer to poly(ethylene glycol), has potential applications in biomedical fields. The hydrodynamic parameters, such as the hydrodynamic radius and sedimentation coefficient, are important to understand its dynamics and properties, including its effect on the interactions between proteins and cells. In this study, we have investigated the hydrodynamic properties and thermodynamic parameters of a series of narrowly distributed PEtOx polymers with molecular weights ranging from 1.3 × 103 to 3.1 × 105 g mol−1, and the scaling laws between them by the use of a combination of analytical ultracentrifugation and laser light scattering. It is found that the sedimentation coefficient (s20,w) and hydrodynamic radius (Rh,0) at infinite dilution scale with molecular weight (Mw) as s20,w = Ks × Mαw = 0.0071 (S) × M0.462±0.019w and Rh,0 = KRh × Mβw = 0.0179 (nm) × M0.539±0.012w, respectively.

Scaling laws between the hydrodynamic parameters and molecular weight of linear poly(2-ethyl-2-oxazoline)

The sedimentation and diffusion of poly(ethylene glycol) (PEG) with weight average molecular weight (M(w)) from 5 x 10(2) to 2 x 10(5) g/mol have been investigated by use of an analytical ultracentrifuge (AUC). The sedimentation velocity analysis based on the Lamm equation gives the sedimentation coefficient (s) and diffusion coefficient (D). Our study reveals that the sedimentation coefficient (s(0)) and diffusion coefficient (D(0)) at infinite dilution scale to molecular weight (M(w)), namely, s(0) = K(s)M(w)(alpha), with K(s) = 6.14 x 10(-3) and alpha = 0.469 +/- 0.008, and D(0) = K(D)M(w)(-beta), with K(D) = 1.43 x 10(-8) and beta = 0.576 +/- 0.007.

Scaling for sedimentation and diffusion of poly(ethylene glycol) in water.

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Scaling for sedimentation and diffusion of poly(ethylene glycol) in water.