Soft Matter Technology at KIT: Chemical Perspective from Nanoarchitectures to Microstructures

Highly flexible elastomer microfluidic chip for single cell manipulation

New materials and fabrication technologies have significantly boosted the development of lab-on-a-chip technologies and functionalities. In this work, we developed a highly flexible elastomer microfluidic chip with a microchannel with a minimum width of ∼5 μm manufactured by imprinting onto an SU-8 template. We found that the deformation induced in the microstructures by manual stretching of the chip is higher than that for the chip itself, which we attribute to the stress concentration of microstructures. Here, we demonstrate that the elastomer enables the manipulation of single cells, such as dynamic trapping-releasing operations, by simply stretching and releasing the elastomer chip.

Diversity-Oriented Synthesis of [2.2]Paracyclophane-derived Fused Imidazo[1,2-a]heterocycles by Groebke-Blackburn-Bienaymé Reaction: Accessing Cyclophanyl Imidazole Ligands Library

This report describes the synthesis of a [2.2]paracyclophane-derived annulated 3-amino-imidazole ligand library through a Groebke-Blackburn-Bienaymé three-component reaction (GBB-3CR) approach employing formyl-cyclophanes in combination with diverse aliphatic and aromatic isocyanides and heteroaromatic amidines. The GBB-3CR process gives access to skeletally-diverse cyclophanyl imidazole ligands, namely 3-amino-imidazo[1,2-a]pyridines and imidazo[1,2-a]pyrazines. Additionally, a one-pot protocol for the GBB-3CR by an in situ generation of cyclophanyl isocyanide is demonstrated. The products were analyzed by detailed spectroscopic techniques, and the cyclophanyl imidazo[1,2-a]pyridine was confirmed unambiguously by single-crystal X-Ray crystallography. The cyclophanyl imidazole ligands can be readily transformed to showcase their useful utility in preparing N,C-palladacycles through regioselective ortho-palladation.

Controlling Regioselectivity in Palladium-Catalyzed C-H Activation/Aryl-Aryl Coupling of 4-Phenylamino[2.2]paracyclophane

Selective activation/functionalization of C-H bonds has emerged as an atom- and step-economical process at the forefront of modern synthetic chemistry. This work reports palladium-catalyzed exclusively para-selective C-H activation/aryl-aryl bond formation with a preference over N-arylation under the Buchwald-Hartwig amination reaction of 4-phenylamino[2.2]paracyclophane. This innovative synthetic strategy allows a facile preparation of [2.2]paracyclophane derivatives featuring disparate para-substitutions at C-4 and C-7 positions in a highly selective manner, gives access to a series of potential candidates for [2.2]paracyclophane-derived new planar chiral ligands. The unprecedented behavior in reactivity and preferential selectivity of C-C coupling over C-N bond formation via C-H activation is unique to the [2.2]paracyclophane scaffold compared to the non-cyclophane analogue under the same reaction conditions. Selective C-H activation/aryl-aryl bond formation and sequential C-N coupling product formation is evidenced unambiguously by X-ray crystallography.

Multi-triggered and enzyme-mimicking graphene oxide/polyvinyl alcohol/G-quartet supramolecular hydrogels

Supramolecular hydrogels with stimuli-responsive behaviors under aqueous environments are attractive for their potential applications in controlled drug delivery, clinical diagnostics, and tissue engineering. However, there still remain challenges in developing multicomponent hydrogels as a new generation of "smart" soft materials with multiple intelligent functions toward complex biochemical stimuli. In this work, a three dimensional (3D)-nanostructured supramolecular hydrogel was fabricated using a simple and facile strategy via the self-assembly of graphene oxide (GO) nanosheets, poly(vinyl alcohol) (PVA) chains, and G-quartet/hemin (G4/H) motifs. The as-prepared GO/PVA/G4/H hydrogel exhibited a honeycomb-like 3D GO network architecture as well as excellent mechanical properties. Importantly, the hydrogel demonstrated pH-inducing reversible and cyclic phase transitions between solution and hydrogel states, which could be used as "ink" for injectable 3D printing of different shaped patterns. Also, binary AND and OR logic gates were successfully built by encapsulating enzymes into the hydrogels, which responded to a variety of biochemicals. In addition, the hydrogels showed excellent peroxidase-like activity, achieving the ultrasensitive detection of H2O2 at a concentration as low as 100 nM by their deposition on an electrochemical electrode. The design of multicomponent hydrogels opens up an avenue to fabricate novel "smart" soft matter for biological and medical applications.