Dendritic polyglycerol-poly(ethylene glycol)-based polymer networks for biosensing application.

This work describes the formation of a new dendritic polyglycerol-poly(ethylene glycol)-based 3D polymer network as a matrix for immobilization of the redox enzyme periplasmatic aldehyde oxidoreductase to create an electrochemical biosensor. The novel network is built directly on the gold surface, where it simultaneously stabilizes the enzyme for up to 4 days. The prepared biosensors can be used for amperometric detection of benzaldehyde in the range of 0.8-400 µM.

Multivalent anchoring and cross-linking of mussel-inspired antifouling surface coatings.

In this work, we combine nature's amazing bioadhesive catechol with the excellent bioinert synthetic macromolecule hyperbranched polyglycerol (hPG) to prepare antifouling surfaces. hPG can be functionalized by different amounts of catechol groups for multivalent anchoring and cross-linking because of its highly branched architecture. The catecholic hPGs can be immobilized on various surfaces including metal oxides, noble metals, ceramics, and polymers via simple incubation procedures. The effect of the catechol amount on the immobilization, surface morphology, stability, and antifouling performance of the coatings was studied. Both anchoring and cross-linking interactions provided by catechols can enhance the stability of the coatings. When the catechol groups on the hPG are underrepresented, the tethering of the coating is not effective; while an overrepresentation of catechol groups leads to protein adsorption and cell adhesion. Thus, only a well-balanced amount of catechols as optimized and described in this work can supply the coatings with both good stability and antifouling ability.

Polyglycerol-derived amphiphiles for the solubilization of single-walled carbon nanotubes in water: a structure-property study.

A series of nonionic amphiphiles derived from polyglycerol dendrons were studied for their ability to solubilize and isolate single-walled carbon nanotubes. The amphiphiles possessed differently sized polar head groups, hydrophobic tail units, and various aromatic and non-aromatic groups between the head and tail groups. Absorbance analysis revealed that amphiphiles with anchor groups derived from pyrene were far inferior to those that possessed simple linear aliphatic tail groups. Absorbance and near-infrared fluorescence analyses revealed a weak dependence on the dendron size of the head group, but a strong positive trend in suspended nanotube density and fluorescence intensity for amphiphiles with longer tail units. Variations in the moieties linking the head and tail groups led to a range of effects on the suspensions, with linkers imparting flexibility and a bent shape that gave improved performance overall. This was illustrated most dramatically by a pair of benzamide-containing amphiphiles, the para isomer of which showed evidence in the fluorescence data of increased nanotube aggregate formation when compared with the meta isomer. In addition, statistical AFM was used to illustrate more directly the microscopic differences between amphiphiles that were effective at nanotube bundle disruption and those that were not.

Phase transition broadening due to interfacial premelting: a new quantitative access to intermolecular interactions within submonolayer films at solid/vapor interfaces.

Investigations of submonolayer films show that phase transition broadening due to interfacial premelting is a general phenomenon. Its experimental observation and thermodynamic interpretation is particularly simple for molecules, which form solid monolayer domains of uniform thickness. This is demonstrated with submonolayer films of two classes of molecules: long chain alkanes and alcohols. The investigations yield quantitative data on the intermolecular interactions within the films at the interface between silica and air for molecular coverages extending over several orders of magnitude. At low surface coverages, we find for the two classes of substances a similar behavior. They behave like 2-dimensional gases. For higher coverages, when the molecules form closed films, the behavior is very different. This is explained by the different molecular organization within the films at higher coverages. The alkanes form a homogeneous, van der Waals-like liquid film with randomly oriented molecules. The alcohols are organized as a closed film with the OH groups oriented toward the silica surface. Thus, the OH group density at the silica/film interface changes with varying coverage. This leads to a change in the OH group hydration, which dominates the interactions between the alcohol molecules. The results demonstrate that the interface-induced premelting can be used as a new and quite universal tool to measure intermolecular interactions within molecularly thin films at solid/vapor interfaces.