Investigation of the Atmospheric Moisture Effect on the Molecular Behavior of an Isocyanate-Based Primer Surface.

A primer coating is engineered to facilitate compatibility between products like adhesives, sealants, and potting compounds and targeted substrates. Prolonged exposure of isocyanate-based primer surfaces to the environment is known to negatively affect the interfacial adhesion between itself and the products subsequently applied on top of it. However, the molecular behavior behind this observed phenomenon remained to be further investigated.

pH-Responsive Cellulose Nanocrystal Gels and Nanocomposites.

We show that functionalization of the surface of cellulose nanocrystals (CNCs) with either carboxylic acid (CNC-COH) or amine (CNC-NH) moieties renders the CNCs pH-responsive. At low pH, where the amine groups are protonated, CNC-NH forms aqueous dispersions in water on account of electrostatic repulsions of the ammonium moieties inhibiting aggregation. However, a transition to hydrogels is observed at higher pH where the CNC-NH are neutral and the attractive forces based on hydrogen bonding dominate.

Micropatterning of bioactive self-assembling gels.

Microscale topographical features have been known to affect cell behavior. An important target in this area is to integrate top down techniques with bottom up self-assembly to create three-dimensional (3D) patterned bioactive mimics of extracellular matrices. We report a novel approach toward this goal and demonstrate its use to study the behavior of human mesenchymal stem cells (hMSCs).

Peptide amphiphile nanofibers with conjugated polydiacetylene backbones in their core.

The coupling of electronic and biological functionality through self-assembly is an interesting target in supramolecular chemistry. We report here on a set of diacetylene-derivatized peptide amphiphiles (PAs) that react to form conjugated polydiacetylene backbones following self-assembly into cylindrical nanofibers. The polymerization reaction yields highly conjugated backbones when the peptidic segment of the PAs has a linear, as opposed to a branched, architecture.

Presentation of RGDS epitopes on self-assembled nanofibers of branched peptide amphiphiles.

Branched peptide amphiphile (PA) molecules bearing biological epitopes were designed and synthesized using orthogonal protecting group chemistry on amine groups at lysine residues. These molecules self-assemble into high-aspect-ratio cylindrical nanofibers, and their branched architecture enhances accessibility of epitopes for protein binding and also allows the presentation of more than one epitope in a single molecule. The RGDS cell adhesion epitope was used as a model bioactive signal on PA molecules for potential biomedical applications.

Synthesis and characterization of thermoreversible biopolymer microgels based on hydrogen bonded nucleobase pairing.

We describe the synthesis and characterization of a thermoreversibly cross-linked biopolymer microgel based on protein, DNA, and peptide nucleic acid (PNA) components. The DNA assembles into a trifunctional three-way junction (TWJ) with single-stranded overhangs. PNA oligomers complementary to these overhangs and bearing terminal biotin groups hybridize to the DNA TWJ and simultaneously bind to the tetrafunctional protein avidin, leading to a cross-linked system.