Length-Sorted, Large-Diameter, Polyfluorene-Wrapped Semiconducting Single-Walled Carbon Nanotubes for High-Density, Short-Channel Transistors

Samples of highly enriched semiconducting SWCNTs with average diameters of 1.35 nm have been prepared by combining PODOF polymer wrapping with size-exclusion chromatography. The purity of the material was determined to be >99.7% from the transfer characteristics of short-channel transistors comprising densely aligned sc-SWCNTs. The transistors have a hole mobility of up to 297 cm²V^–1 s^–1 and an On/Off ratio as high as 2 × 10⁸

Self-Assembled DNA Nanocentipede as Multivalent Drug Carrier for Targeted Delivery

An idea drug carrier, with good binding affinity, selectivity, drug payload capacity, and cellular internalized capability, will greatly improve the efficiency of target delivery. Herein a self-assembled and multivalent DNA nanostructure was developed as drug carrier for efficient and targeted delivery. The DNA structure was similar to that of a centipede, composed of trunk and legs: The trunk was a self-assembled DNA scaffold via hybridization chain reaction (HCR) from two biotinylated hairpin monomers created upon initiation by a trigger DNA, and the legs were biotinylated aptamers conjugated to the trunk via streptavidin–biotin affinity interaction. The long trunk of the “DNA nanocentipede” was loaded with doxorubicin (Dox), and the legs were SMMC-7721 cell-binding aptamers (Zy1) which functioned as targeting moieties to firmly and selectively grasp target cells. The results of agarose gel electrophoresis and fluorescence anisotropy confirmed that Zy1-based DNA nanocentipedes (Zy1-Nces) were successfully constructed. Flow cytometric analyses demonstrated that Zy1-Nces were more effective than free Zy1 in binding affinity and selectivity due to a multivalent effect. Confocal microscopy studies demonstrated that the internalization was highly dependent on the higher valences of DNA nanocentipedes without the loss of selectivity. Meanwhile, Zy1-Nces exhibited high drug-loading capacity and selective drug transport. The results of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed enhanced cellular cytotoxicity of the Dox-loaded Zy1-Nces (Zy1-Nces-Dox) to the target SMMC-7721 cells but not negative control L02 cells. This approach is applicable to prepare drug carriers for other targets by construction of the nanocentipedes with relevant nucleic acid fragments

Self-Assembled Supramolecular Nanoprobes for Ratiometric Fluorescence Measurement of Intracellular pH Values

Self-assembly of small building blocks into functional supramolecular nanostructure has opened prospects for the design of novel materials. With this molecular engineering strategy, we have developed self-assembled supramolecular nanoprobes (SSNPs) for ratiometric fluorescence measurement of pH values in cells. The nanoprobes with a diameter of ∼30 nm could be formulated just by mixing pH-sensitive adamantane–fluorescein (Ad-F) and pH-insensitive adamantane–Rhodamine B (Ad-R) with β-cyclodextrin polymer (poly-β-CD) at one time. The nanoprobes with good biocompatibility have been successfully applied to measure intracellular pH in the pH range of 4–8 and estimate pH fluctuations associated with different stimuli in cells. Moreover, we expect that this self-assembled approach is applicable to the construction of nanoprobes for other targets in cells just by replacing the respective indicator dyes with relevant indicators

Detection of Nucleic Acids in Complex Samples via Magnetic Microbead-Assisted Catalyzed Hairpin Assembly and “DD–A” FRET

Nucleic acids, as one kind of significant biomarker, have attracted tremendous attention and exhibited immense values in fundamental studies and clinical applications. In this work, we developed a fluorescent assay for detecting nucleic acids in complex samples based on magnetic microbead (MMB)-assisted catalyzed hairpin assembly (CHA) and a donor donor–acceptor fluorescence resonance energy transfer (“DD–A” FRET) signaling mechanism. Three types of DNA hairpin probes were employed in this system, including Capture, H1 (double FAM-labeled probe as FRET donor), and H2 (TAMRA-labeled probe as FRET acceptor). First, the Captures immobilized on MMBs bound to targets in complex samples, and the sequences in Captures that could trigger catalyzed hairpin assembly (CHA) were exposed. Then, target-enriched MMB complexes were separated and resuspended in the reaction buffer containing H1 and H2. As a result, numerous H1–H2 duplexes were formed during the CHA process, inducing an obvious FRET signal. In contrast, CHA could not be triggered, and the FRET signal was weak, while target was absent. With the aid of magnetic separation and “DD–A” FRET, errors from background interference were effectively eliminated. Importantly, this strategy realized amplified detection in buffer, with detection limits of microRNA as low as 34 pM. Furthermore, this method was successfully applied to detect microRNA-21 in serum and cell culture media. The results showed that our method has the potential for biomedical research and clinical application