Heavy-Metal Adsorption Behavior of Two-Dimensional Alkalization-Intercalated MXene by First-Principles Calculations

The two-dimensional (2D) layered MXene (Ti₃C₂(OH)_<i>x</i>F_2–<i>x</i>) material can be alkalization intercalated to achieve heavy-metal ion adsorption. Herein the adsorption kinetics of heavy-metal ions and the effect of intercalated sites on adsorption have been interpreted by first-principles with density functional theory. When the coverage of the heavy-metal ion is larger than 1/9 monolayer, the two-dimensional alkalization-intercalated MXene (alk-MXene: Ti₃C₂(OH)₂) exhibits strong heavy-metal ion absorbability. The hydrogen atoms around the adsorbed heavy-metal atom are prone to form a hydrogen potential trap, maintaining charge equilibrium. In addition, the ion adsorption efficiency of alk-MXene decreases due to the occupation of the F atom but accelerates by the intercalation of Li, Na, and K atoms. More importantly, the hydroxyl site vertical to the titanium atom shows a stronger trend of removing the metal ion than other positions

Synthesis of MXene/Ag Composites for Extraordinary Long Cycle Lifetime Lithium Storage at High Rates

A new MXene/Ag composite was synthesized by direct reduction of a AgNO₃ aqueous solution in the presence of MXene (Ti₃C₂(OH)_0.8F_1.2). The as-received MXene/Ag composite can be deemed as an excellent anode material for lithium-ion batteries, exhibiting an extraordinary long cycle lifetime with a large capacity at high charge–discharge rates. The results show that Ag self-reduction in MXene solution is related to the existence of low-valence Ti. Reversible capacities of 310 mAh·g^–1 at 1 C (theoretical value being ∼320 mAh·g^–1), 260 mAh·g^–1 at 10 C, and 150 mAh·g^–1 at 50 C were achieved. Remarkably, the composite withstands more than 5000 cycles without capacity decay at 1–50 C. The main reasons for the long cycle life with high capacity are relevant to the reduced interface resistance and the occurrence of Ti­(II) to Ti­(III) during the cycle process

Unique Lead Adsorption Behavior of Activated Hydroxyl Group in Two-Dimensional Titanium Carbide

The functional groups and site interactions on the surfaces of two-dimensional (2D) layered titanium carbide can be tailored to attain some extraordinary physical properties. Herein a 2D alk-MXene (Ti₃C₂(OH/ONa)_<i>x</i>F_2–<i>x</i>) material, prepared by chemical exfoliation followed by alkalization intercalation, exhibits preferential Pb­(II) sorption behavior when competing cations (Ca­(II)/Mg­(II)) coexisted at high levels. Kinetic tests show that the sorption equilibrium is achieved in as short a time as 120 s. Attractively, the alk-MXene presents efficient Pb­(II) uptake performance with the applied sorption capacities of 4500 kg water per alk-MXene, and the effluent Pb­(II) contents are below the drinking water standard recommended by the World Health Organization (10 μg/L). Experimental and computational studies suggest that the sorption behavior is related to the hydroxyl groups in activated Ti sites, where Pb­(II) ion exchange is facilitated by the formation of a hexagonal potential trap

Process Development and Structural Characterization of an Anti-Notch 3 Antibody–Drug Conjugate

The development of a process for the preparation of a conventional anti-Notch 3 antibody–drug conjugate (ADC) is described. The initial reaction conditions used for the conjugation of an auristatin payload to an anti-Notch 3 monoclonal antibody led to the formation of an ADC mixture with a significant level of aggregates. Further process optimization studies resulted in the identification of reaction conditions for formation of the conjugate with a low level of aggregates. The temperature of the antibody reduction step was found to have an impact on the formation of aggregates in the ADC mixture. Differences in the antibody reduction temperatures also caused changes in the distribution of conjugated payload on the ADC species. Stability studies of anti-Notch 3 ADCs prepared by two processes differing in the antibody reduction temperature showed subtle differences in their aggregation propensities. The aggregates produced in the crude ADC reaction mixture could be separated from the desired monomer on the hydroxyapatite column under mild conditions without significantly impacting the average drug loading of the purified ADC

Characterization and Higher-Order Structure Assessment of an Interchain Cysteine-Based ADC: Impact of Drug Loading and Distribution on the Mechanism of Aggregation

The impact of drug loading and distribution on higher order structure and physical stability of an interchain cysteine-based antibody drug conjugate (ADC) has been studied. An IgG1 mAb was conjugated with a cytotoxic auristatin payload following the reduction of interchain disulfides. The 2-D LC-MS analysis shows that there is a preference for certain isomers within the various drug to antibody ratios (DARs). The physical stability of the unconjugated monoclonal antibody, the ADC, and isolated conjugated species with specific DAR, were compared using calorimetric, thermal, chemical denaturation and molecular modeling techniques, as well as techniques to assess hydrophobicity. The DAR was determined to have a significant impact on the biophysical properties and stability of the ADC. The C_H2 domain was significantly perturbed in the DAR6 species, which was attributable to quaternary structural changes as assessed by molecular modeling. At accelerated storage temperatures, the DAR6 rapidly forms higher molecular mass species, whereas the DAR2 and the unconjugated mAb were largely stable. Chemical denaturation study indicates that DAR6 may form multimers while DAR2 and DAR4 primarily exist in monomeric forms in solution at ambient conditions. The physical state differences were correlated with a dramatic increase in the hydrophobicity and a reduction in the surface tension of the DAR6 compared to lower DAR species. Molecular modeling of the various DAR species and their conformers demonstrates that the auristatin-based linker payload directly contributes to the hydrophobicity of the ADC molecule. Higher order structural characterization provides insight into the impact of conjugation on the conformational and colloidal factors that determine the physical stability of cysteine-based ADCs, with implications for process and formulation development