An active cell scaffold based on a graphene-polymer hydrogel has been successfully fabricated. The macroporous hydrogel can efficiently capture cells not only through the bioadhesive ligand RGD but also through on-demand release of cells with an NIR light stimulus. The latter process shows better dynamic control over cells than traditional passive-hydrogel-based cell depots.

The efficient synthesis of high molar mass, first-(G1) and second-generation (G2) dendronized polymethacrylate derivatives PG1 and PG2, respectively, and their thermoresponsive properties in aqueous solution are described. All dendrons are branched 3-fold and were synthesized on the multigram scale using gallic acid as branching point and tri(ethylene glycol) (TEG) units as linker. The corresponding macromonomers carry methoxy groups in the periphery and are water-soluble, which allows polymerizing in aqueous medium. For comparison, PG1 and PG2 were also prepared in DMF solution and in bulk. These polymers are fully soluble in water at room temperature and turn turbid at elevated temperatures (approximately 62-65°C), a phenomenon that is typically referred to as thermoresponsiveness. This phase transition was investigated by 1 H NMR spectroscopy and turbidity measurements using UV/vis spectroscopy. The effect of molar mass and concentration on this transition was examined. In accordance with the normal usage, this transition temperature is referred to as lower critical solution temperature (LCST). Aggregates with sizes in the range of a few micrometers were observed above the LCSTs by conventional optical microscopy. Finally, the thermally induced aggregation and deaggregation processes were video-taped in high resolution.

A series of first (PG 1) and second generation (PG 2) dendronized polymers were synthesized which exhibit fast and sharp phase transitions with negligible hystereses in aqueous solutions and apparent lower critical solution temperatures (LCSTs) in the range of 33-49 degrees C.

The collapse transition of thermoresponsive dendronized polymers was characterized on a molecular scale by CW EPR spectroscopy. Aggregation of the polymer is triggered by dynamic structural inhomogeneities of a few nanometers, and the dehydration of the polymer chains proceeds, despite the sharp phase transition, over a temperature interval of at least 30 °C (see picture).

Triblock copolymers of poly(N‐isopropylacrylamide)‐block‐poly(N,N‐dimethylacrylamide)‐block‐poly(N‐isopropylacrylamide) were synthesised via RAFT polymerisation using a symmetrical bistrithiocarbonate. Keeping the block length of the permanently hydrophilic middle block constant, the length of the poly(N‐isopropylacrylamide) block was varied broadly. The thermoresponsive aggregation of the polymers in water was studied by 1H NMR, turbidimetry, and dynamic light scattering. The complex aggregation behaviour was block length dependent and occurred under kinetic control. Importantly, different information on the hydrophilic‐hydrophobic transition of the poly(N‐isopropylacrylamide) block was obtained using the various analytical methods and could not be directly correlated.magnified image

Here we use functionalized carbon nanodots (C-dots) as novel electrochemiluminescence (ECL) probes and graphene nanosheets as signal amplification agents for highly sensitive and selective cancer cell detection. The ECL cytosensor shows superior cell-capture ability and exhibits a wide linear range and a low detection limit for cancer cells.

Novel first (G1) and second (G2) generation dendrimers based on three-fold branched oligoethylene glycol dendrons are efficiently synthesized which show characteristic thermoresponsive behavior and negligible cytotoxicity (for G2).

With the combination of molecular scale information from electron paramagnetic resonance (EPR) spectroscopy and meso-/macroscopic information from various other characterization techniques, the formation of mesoglobules of thermoresponsive dendronized polymers is explained. Apparent differences in the EPR spectra in dependence of the heating rate, the chemical nature of the dendritic substructure of the polymer, and the concentration are interpreted to be caused by the formation of a dense polymeric layer at the periphery of the mesoglobule. This skin barrier is formed in a narrow temperature range of ~4 K above T(C) and prohibits the release of molecules that are incorporated in the polymer aggregate. In large mesoglobules, formed at low heating rates and at high polymer concentrations, a considerable amount of water is entrapped that microphase-separates from the collapsed polymer chains at high temperatures. This results in the aggregates possessing an aqueous core and a corona consisting of collapsed polymer chains. A fast heating rate, a low polymer concentration, and hydrophobic subunits in the dendritic polymer side chains make the entrapment of water less favorable and lead to a higher degree of vitrification. This may bear consequences for the design and use of thermoresponsive polymeric systems in the fast growing field of drug delivery.