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DNA assembly has provided new opportunities for the development of a novel drug delivery system (DDS) for real-time monitoring and precision treatment of cancer lesions. Herein, we propose mRNA-responsive DNA nanospheres (DNA-NS), whose self-assembly can be triggered by products of rolling circle amplification and functional hairpins and deliver anticancer drug doxorubicin (DOX) for bioimaging and cancer therapy. It has been demonstrated that DNA-NS exhibited good stability in biological environments. Hence, DNA-NS can serve as a universal platform of detections of mRNA related to various tumor cells. DNA-NS can also be applied in the mRNA-dependent DDS. For drug-resistant cells, which are widely present in actual cancer models, DNA-NS can effectively overcome the efflux action of drug-resistant cells to improve the therapeutic efficacy of DOX. In summary, this study provides a potential strategy for constructing the endogenous mRNA-responsive DDS for cancer diagnosis and chemotherapy in vivo.

With the development of biotechnology, the detection of cancer biomarkers has been a promising approach for cancer diagnosis and therapy. Herein, we reported a DNA octahedron-based fluorescence nanoprobe, which was capable of detecting and imaging of two kinds of tumor-related mRNAs in living cells simultaneously. The DNA nanoprobe was constructed of eight single-stranded DNAs, in which two oligonucleotides (recognition sequences) were modified with quenchers (BHQ2 and BHQ3) and the adjacent sequences were modified with fluorophores (Cy3 and Cy5), respectively. In the presence of targets, the recognition sequences could dissociate from the nanoprobe skeleton by strand displacement reaction and the fluorescence was recovered accordingly. With the modification of AS1411 aptamer, the nanoprobe could internalize cancer cells more efficiently and distinguish cancer cells from normal cells. In addition, the nanoprobe exhibited good stability, biocompatibility, selectivity, and responded quickly to the targets as well. The DNA nanoprobe was designed in the formation of octahedron and may provide an inspiration for multidetection of cancer biomarkers based on the DNA nanotechnology.

Non-invasive early diagnosis of breast cancer is the most effective way to improve the survival rate and increase more chances of breast-conserving. In this paper, we developed a label-free fluorescent biosensor based on nuclease assisted target recycling and Thioflavin T-induced quadruplex formation for short DNA species of c-erbB-2 detection in saliva. By employing the strategy, the sensor can detect as low as 20fM target DNA with high discrimination ability even against single-base mismatch sequence. To the best of our knowledge, the proposed sensor is the first attempt to apply Thioflavin T that possesses outstanding structural selectivity for G-quadruplex in DNA amplification techniques, which may represent a promising path toward direct breast cancer detection in saliva at the point of care., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Herein, a signal magnification electrochemical aptasensor for the detection of breast cancer cell via free-running DNA walker is constructed. Theoretically, just one DNA walker, released by target cell-responsive reaction, can automatically cleave all D-RNA (a chimeric DNA/RNA oligonucleotide with a cleavage point rArU) anchored on electrode into shorter produces, giving rise to considerably detectable signal finally. Under the optimal conditions, the electrochemical signal decreased linearly with the concentration of MCF-7 cell. The linear range is from 0 to 500 cells mL −1 with a detection limit of 47 cells mL −1 . In a word, this approach may have advantages over traditional reported DNA machines for bioassay, particularly in terms of ease of operation, cost efficiency, free of labeling and of complex track design, which may hold great potential for wide application. [ABSTRACT FROM AUTHOR]

In this paper, we describe a novel label-free fluorescence method for microRNA-21 (miR-21) detection based on terbium (Tb3+) and duplex-specific nuclease (DSN) assisted target recycling. Capture probes (Cps), containing a target-binding part and a signal-output part, are immobilized on magnetic beads (MBs). In the presence of the target miR-21, it hybridizes with the target-binding part of a Cp to form a DNA–RNA heteroduplex. Due to the considerable cleavage preference for DNA in DNA–RNA hybrids, DSN hydrolyzes the target-binding part of the Cp while liberating the intact target miR-21 to hybridize with a new Cp and initiate the second cycle of hydrolysis. Eventually, through magnetic separation, only the signal-output part of the Cp could remain in solution and function as a signalling flare to increase the fluorescence intensity of Tb3+ dramatically. By employing the above strategy, this approach can gain an amplified fluorescent signal and detect as low as 8 fM miR-21 under the optimized conditions. Moreover, due to the high selectivity of DSN, the method shows little cross-hybridization among the closely related miRNA family members even at the single-base-mismatched level. Successful attempts were made in applying the approach to detect miR-21 in human cell lysate samples of breast cancer patients. [ABSTRACT FROM AUTHOR]