Ultrastiff,Strong, and Highly Thermally Conductive Crystalline Graphitic Films with Mixed Stacking Order

A macroscopic film (2.5 cm × 2.5 cm) made by layer‐by‐layer assembly of 100 single‐layer polycrystalline graphene films is reported. The graphene layers are transferred and stacked one by one using a wet process that leads to layer defects and interstitial contamination. Heat‐treatment of the sample up to 2800 °C results in the removal of interstitial contaminants and the healing of graphene layer defects. The resulting stacked graphene sample is a freestanding film with near‐perfect in‐plane crystallinity but a mixed stacking order through the thickness, which separates it from all existing carbon materials. Macroscale tensile tests yields maximum values of 62 GPa for the Young's modulus and 0.70 GPa for the fracture strength, significantly higher than has been reported for any other macroscale carbon films; microscale tensile tests yield maximum values of 290 GPa for the Young's modulus and 5.8 GPa for the fracture strength. The measured in‐plane thermal conductivity is exceptionally high, 2292 ± 159 W m^?1 K^?1 while in‐plane electrical conductivity is 2.2 × 10⁵ S m^?1. The high performance of these films is attributed to the combination of the high in‐plane crystalline order and unique stacking configuration through the thickness.     

Thin multilayer films and microcapsules containing DNA quadruplex motifs

The assembly of multifunctional nanostructures bearing G-quadruplex motifs broadens the prospects of using G-quadruplexes as therapeutic carriers. Herein, we report the synthesis and characterization of an oligodeoxyguanosine, G15-mer polymer conjugate. We demonstrate that G15-mer oligonucleotides grafted to a polymer chain preserve the ability to self-assemble into ordered structures. The G-quadruplex-polymer conjugates were assembled onto a surface via hybridization with 30-mer cytosine strands, C30-mer, using a layer-by-layer approach to form microcapsules. A mechanism for the sequential assembly of the multilayer films and microcapsules is presented. We further investigate the photophysical behavior of porphyrin TMPyP4 bound to multilayer-coated particles. This study shows that the multilayer films bear residual and functional quadruplex moieties that can be used to effectively bind therapeutic agents.     

Ratiometric Organic Fibers for Localized and Reversible Ion Sensing with Micrometer‐Scale Spatial Resolution

A fundamental issue in biomedical and environmental sciences is the development of sensitive and robust sensors able to probe the analyte of interest, under physiological and pathological conditions or in environmental samples, and with very high spatial resolution. In this work, novel hybrid organic fibers that can effectively report the analyte concentration within the local microenvironment are reported. The nanostructured and flexible wires are prepared by embedding fluorescent pH sensors based on seminaphtho‐rhodafluor‐1‐dextran conjugate. By adjusting capsule/polymer ratio and spinning conditions, the diameter of the fibers and the alignment of the reporting capsules are both tuned. The hybrid wires display excellent stability, high sensitivity, as well as reversible response, and their operation relies on effective diffusional kinetic coupling of the sensing regions and the embedding polymer matrix. These devices are believed to be a powerful new sensing platform for clinical diagnostics, bioassays and environmental monitoring.     

Coupling electrodeposition with layer-by-layer assembly to address proteins within microfluidic channels

Two thin-film assembly methods are coupled to address proteins. Electrodeposition confers programmability and generates a template for layer-by-layer (LbL) assembly. LbL enables precise control of film thickness and the incorporation of labile biological components. The capabilities are demonstrated using glucose oxidase (GOx) based electrochemical biosensing within a microfabricated fluidic device.     

Cell apoptosis control using BMP4 and noggin embedded in a polyelectrolyte multilayer film

Programmed cell death (apoptosis) is a genetically regulated process of cell elimination essential during development. During development, programmed cell death is involved in the specific shaping of organs, in the elimination of cells having achieved their program, and in regulating the number of cells to differentiate. Tooth development includes these three aspects and was used here as a model to study the control of apoptosis. Bone morphogenetic proteins (BMPs) are currently considered as playing a major role in signaling apoptosis. This apoptosis could be stopped by treatments with a BMP antagonist ("Noggin"). We selected a model system made by a layer-by-layer approach using poly-L-glutamic acid (PlGA) and poly-L-lysine (PlL) films into which BMP4 and/or Noggin have been embedded. Our results indicate that in situ control of apoptosis during tooth differentiation mediated by both BMP4 and Noggin embedded in a polyelectrolyte multilayer film is possible. We show here for the first time that in the presence of BMP4 and Noggin embedded in a multilayered film, we can induce or inhibit cell death in tooth differentiation, and conserve their biological effects.