Protein Catalyzed Capture Agents with Tailored Performance for In Vitro and In Vivo Applications

We report on peptide-based ligands matured through the protein catalyzed capture (PCC) agent method to tailor molecular binders for in vitro sensing/diagnostics and in vivo pharmacokinetics parameters. A vascular endothelial growth factor (VEGF) binding peptide and a peptide against the protective antigen (PA) protein of Bacillus anthracis discovered through phage and bacterial display panning technologies, respectively, were modified with click handles and subjected to iterative in situ click chemistry screens using synthetic peptide libraries. Each azide-alkyne cycloaddition iteration, promoted by the respective target proteins, yielded improvements in metrics for the application of interest. The anti-VEGF PCC was explored as a stable in vivo imaging probe. It exhibited excellent stability against proteases and a mean elimination in vivo half-life (T_(1/2)) of 36 min. Intraperitoneal injection of the reagent results in slow clearance from the peritoneal cavity and kidney retention at extended times, while intravenous injection translates to rapid renal clearance. The ligand competed with the commercial antibody for binding to VEGF in vivo. The anti-PA ligand was developed for detection assays that perform in demanding physical environments. The matured anti-PA PCC exhibited no solution aggregation, no fragmentation when heated to 100°C, and  > 81% binding activity for PA after heating at 90°C for 1 h. We discuss the potential of the PCC agent screening process for the discovery and enrichment of next generation antibody alternatives

Protein Catalyzed Capture Agents with Tailored Performance for In Vitro and In Vivo Applications

We report on peptide-based ligands matured through the protein catalyzed capture (PCC) agent method to tailor molecular binders for in vitro sensing/diagnostics and in vivo pharmacokinetics parameters. A vascular endothelial growth factor (VEGF) binding peptide and a peptide against the protective antigen (PA) protein of Bacillus anthracis discovered through phage and bacterial display panning technologies, respectively, were modified with click handles and subjected to iterative in situ click chemistry screens using synthetic peptide libraries. Each azide-alkyne cycloaddition iteration, promoted by the respective target proteins, yielded improvements in metrics for the application of interest. The anti-VEGF PCC was explored as a stable in vivo imaging probe. It exhibited excellent stability against proteases and a mean elimination in vivo half-life (T_(1/2)) of 36 min. Intraperitoneal injection of the reagent results in slow clearance from the peritoneal cavity and kidney retention at extended times, while intravenous injection translates to rapid renal clearance. The ligand competed with the commercial antibody for binding to VEGF in vivo. The anti-PA ligand was developed for detection assays that perform in demanding physical environments. The matured anti-PA PCC exhibited no solution aggregation, no fragmentation when heated to 100°C, and  > 81% binding activity for PA after heating at 90°C for 1 h. We discuss the potential of the PCC agent screening process for the discovery and enrichment of next generation antibody alternatives

Cellulose Nanofibrils and Diblock Copolymer Complex: Micelle Formation and Enhanced Dispersibility

A great challenge to the utilization of bioderived cellulose nanofibrils (CNFs) is related to dispersion, where the hydrophilic nature makes them difficult to disperse in both organic solvents and hydrophobic polymers. In this study, an amphiphilic diblock copolymer, poly­(methyl methacrylate-<i>b</i>-acrylic acid) (PMMA-<i>b</i>-PAA), which contains a short interactive block of PAA and a long hydrophobic block of PMMA, was utilized to modify the surface of CNFs covered with carboxylic acid groups (CNF-COOH). The PAA block binds to the surface carboxylic acid groups on the CNFs through the formation of multiple hydrogen bonds, while the hydrophobic PMMA block enables better dispersion of the CNFs as well as interfacial adhesion with the matrix polymer. The attachment of PMMA-<i>b</i>-PAA to the CNFs was confirmed through Fourier transform infrared spectroscopy. Micelles were observed to form from a dispersion of CNF-COOH/PMMA-<i>b</i>-PAA complex in H₂O. Good dispersion with individualized nanofibrils has been achieved in dimethylformamide, dimethyl sulfoxide, ethanol, and methanol even when a low amount of block copolymer was functionalized on the CNF surface. The dispersion level of CNF-COOH/PMMA-<i>b</i>-PAA correlates well with the dielectric constant of the solvents, where solvents with high dielectric constants are better able to disperse the PMMA-<i>b</i>-PAA modified nanofibrils

Impact of Stereo- and Regiochemistry on Energetic Materials

The synthesis, physical properties and calculated performances of six stereo- and regioisomeric cyclobutane nitric ester materials is described. While the calculated performances of these isomers, as expected, were similar, their physical properties were found to be extremely different. By altering the stereo- and regiochemistry, complete tunability in the form of low-or high-melting solids, standalone melt-castable explosives, melt-castable explosive eutectic compounds, and liquid propellant materials were obtained. This study demonstrates that theoretical calculations should not be the main factor in driving the design and synthesis of new materials, and that stereo- and regiochemistry offer a new dimension to consider when designing compounds of potential relevance to energetic formulators.<br /

Polydopamine and Polydopamine–Silane Hybrid Surface Treatments in Structural Adhesive Applications

Numerous studies have focused on the remarkable adhesive properties of polydopamine, which can bind to substrates with a wide range of surface energies, even under aqueous conditions. This behavior suggests that polydopamine may be an attractive option as a surface treatment in structural bonding applications, where good bond durability is required. Here, we assessed polydopamine as a surface treatment for bonding aluminum plates with an epoxy resin. A model epoxy adhesive consisting of diglycidyl ether of bisphenol A (DGEBA) and Jeffamine D230 polyetheramine was employed, and lap shear measurements (ASTM D1002 10) were made (i) under dry conditions to examine initial bond strength and (ii) after exposure to hot/wet (63 °C in water for 14 days) conditions to assess bond durability. Surprisingly, our results showed that polydopamine alone as a surface treatment provided no benefit beyond that obtained by exposing the substrates to an alkaline solution of tris buffer used for the deposition of polydopamine. This implies that polydopamine has a potential Achilles’ heel, namely, the formation of a weak boundary layer that was identified using X-ray photoelectron spectroscopy (XPS) of the fractured surfaces. In fact, for longer deposition times (2.5 and 18 h), the tris buffer-treated surface outperformed the polydopamine surface treatments, suggesting that tris buffer plays a unique role in improving adhesive performance even in the absence of polydopamine. We further showed that the use of polydopamine–3-aminopropyltriethoxysilane (APTES) hybrid surface treatments provided significant improvements in bond durability at extended deposition times relative to both polydopamine and an untreated control

Highly Transparent and Toughened Poly(methyl methacrylate) Nanocomposite Films Containing Networks of Cellulose Nanofibrils

Cellulose nanofibrils (CNFs) are a class of cellulosic nanomaterials with high aspect ratios that can be extracted from various natural sources. Their highly crystalline structures provide the nanofibrils with excellent mechanical and thermal properties. The main challenges of CNFs in nanocomposite applications are associated with their high hydrophilicity, which makes CNFs incompatible with hydrophobic polymers. In this study, highly transparent and toughened poly­(methyl methacrylate) (PMMA) nanocomposite films were prepared using various percentages of CNFs covered with surface carboxylic acid groups (CNF-COOH). The surface groups make the CNFs interfacial interaction with PMMA favorable, which facilitate the homogeneous dispersion of the hydrophilic nanofibrils in the hydrophobic polymer and the formation of a percolated network of nanofibrils. The controlled dispersion results in high transparency of the nanocomposites. Mechanical analysis of the resulting films demonstrated that a low percentage loading of CNF-COOH worked as effective reinforcing agents, yielding more ductile and therefore tougher films than the neat PMMA film. Toughening mechanisms were investigated through coarse-grained simulations, where the results demonstrated that a favorable polymer-nanofibril interface together with percolation of the nanofibrils, both facilitated through hydrogen bonding interactions, contributed to the toughness improvement in these nanocomposites