Design and fabrication of flexible DNA polymer cocoons to encapsulate live cells.

The capability to encapsulate designated live cells into a biologically and mechanically tunable polymer layer is in high demand. Here, an approach to weave functional DNA polymer cocoons has been proposed as an encapsulation method. By developing in situ DNA-oriented polymerization (isDOP), we demonstrate a localized, programmable, and biocompatible encapsulation approach to graft DNA polymers onto live cells. Further guided by two mutually aided enzymatic reactions, the grafted DNA polymers are assembled into DNA polymer cocoons at the cell surface. Therefore, the coating of bacteria, yeast, and mammalian cells has been achieved. The capabilities of this approach may offer significant opportunities to engineer cell surfaces and enable the precise manipulation of the encapsulated cells, such as encoding, handling, and sorting, for many biomedical applications.

Rhodopsin-Like Ionic Gate Fabricated with Graphene Oxide and Isomeric DNA Switch for Efficient Photocontrol of Ion Transport.

Rhodopsin, composed of opsin and isomeric retinal, acts as the primary photoreceptor by converting light into electric signals. Inspired by rhodopsin, we have fabricated a light-regulated ionic gate on the basis of the design of a graphene oxide (GO)-biomimetic DNA-nanochannel architecture. In this design, photoswitchable azobenzene (Azo)-DNA is introduced to the surface of porous anodic alumina (PAA) membrane. With modulation of the interaction between the GO blocker and Azo-DNA via flexibly regulating trans and cis states of Azo under the irradiation of visible and ultraviolet light, alternatively, the ionic gate is switched between ON and OFF states. This newly constructed ionic gate can possess high efficiency for the control of ion transport because of the high blocking property of GO and the rather tiny path within the barrier layer which are both first employed to fabricate ionic gate. We anticipate that this rhodopsin-like ionic gate may provide a new model and method for the investigation of ion channel, ion function, and ion quantity. In addition, because of the advantages of simple fabrication, good biocompatibility, and universality, this bioinspired system may have potential applications as optical sensors, in photoelectric transformation, and in controllable drug delivery.

DNA nanoflower blooms in nanochannels: a new strategy for miRNA detection.

By employing DNA nanoflower blooming in the nanochannels of porous anodic alumina (PAA), a nanochannel platform for microRNA (miRNA) detection has been proposed. Significant steric and electrostatic hindrance of the miRNA-initiated DNA-nanoflower growth may also amplify the signal readout for miRNA detection to give excellent sensitivity, selectivity and reproducibility.

Embedding Capture-Magneto-Catalytic Activity into a Nanocatalyst for the Determination of Lipid Kinase.

The use of emerging nanocatalysts to investigate the activity of biocatalysts (protein enzymes, catalytic RNAs, etc.) is increasingly receiving attention from material, analytic, and biomedical scientists. Here, we have first fabricated a three-in-one nanocatalyst, the nitrilotriacetic acid (NTA)-modified magnetite nanoparticle (NTA-MNP), to develop an integrated magneto-colorimetric (MagColor) assay for lipid kinase activity so as to solve the inherent problems in a lipid kinase assay. On the basis of three integrated functions of the NTA-MNPs (capture, magnetic separation, and peroxidase activity), the catalytic activity of lipid kinase is directly converted to colorimetric signals. Therefore, the assay procedure is significantly simplified such that in one step the visual detection of lipid kinase activity is possible. Moreover, the whole system responds sensitively in the case that NTA-MNPs recognize a few numbers of the reaction sites, which efficiently initiates the chromogenic reaction of a large amount of chromogens; thus, the detection limit decreases to 6.5 ± 5.8 fM, about three orders of magnitude lower as compared to that of enzyme-linked immune-sorbent assay. So, by embedding desired functions into nanocatalysts, the assay for biocatalysts becomes easy, which may promisingly provide useful tools for biomedical and clinical research in the future.

One-step detection for two serological biomarker species to improve the diagnostic accuracy of hepatocellular carcinoma.

At present, the accuracy of clinical hepatocellular carcinoma (HCC) diagnosis needs to be further improved. In this work, two kinds of serological biomarker species, microRNA and protein biomarker, have been detected simultaneously to identify HCC. Herein, a dual-aptamer hairpin DNA oligonucleotide is designed as the electrochemical sensing probe (ESP) to achieve this goal. The hairpin-structured DNA probe consists microRNA-16 (miR-16) complementary sequence and alpha fetoprotein (AFP) aptamer sequence, so it can both capture miR-16 and AFP. Once it hybridizes with miR-16, the hairpin structure is unlocked so that the terminal modified signal molecule (methylene blue, MB) would give a decreased electrochemical signal. Meanwhile, once it recognizes AFP, concanavalin A (ConA) modified silver nanoparticles (AgNPs) can bind to AFP at the sensing surface. An obvious electrochemical signal of AgNPs can thus be generated for AFP detection. In this way, one-step and simultaneous detection of miRNA-16 and AFP can easily be realized by collecting the two sensitive and non-interfering electrochemical signals. Compared with traditional single biomarker detection methods, this assay strategy can improve the accuracy of HCC by monitoring two kinds of serological biomarkers species. Besides, this novel electrochemical biosensor based on ESP is simple, low-cost and efficient, which make it promising to improve the accuracy and specificity for the diagnosis HCC in the future.

Assay of DNA methyltransferase 1 activity based on uracil-specific excision reagent digestion induced G-quadruplex formation.

DNA methylation catalyzed by DNA methyltransferase plays an important role in many biological processes including gene transcription, genomic imprinting and cellular differentiation. Herein, a novel and effective electrochemical method for the assay of DNA methyltransferase 1(DNMT1) activity has been successfully developed by using uracil-specific excision reagent (USER) induced G-quadruplex formation. Briefly, double stranded DNA containing the recognition sequence of DNMT1 is immobilized on the electrode. Among them, one strand (DNA S1) contains G-rich sequence and a cytosine base, while the supplement strand (DNA S2) cotains C-rich sequence and a methylated cytosine. Through the activity of DNMT1, the hemimethylated CG recognition sequence of the double stranded DNA are methylated and DNA S2 strand is cleaved and removed after the subsequently treatment with EpiTect fast bisulfite conversion kits and USER, leaving the DNA S1 to form the G-quadruplex-hemin DNAzyme for signal amplification. Under optimal-conditions, the method shows wide linear range of 0.1-40 U mL-1 with a detection limit of 0.06 U mL-1. Furthermore, the inhibition assay study demonstrates that SGI-1027 can inhibit the DNMT 1 activity with the IC50 values of 6 µM in the presence of 160 µM S-adenosylmethionine. Since this method can detect human DNMT1 activity effectively and has successfully been applied in complex biological samples, it may have great potential in the applications in DNA methylation related clinical practices and biochemical researches.