Dongzhi Wu

A fluorescent aptasensor based on DNA-scaffolded silver-nanocluster for ochratoxin A detection.

The selective detection of ultratrace amounts of ochratoxin A (OTA) is extremely important for food safety since it is one of the most toxic and widespread mycotoxin. Here we develop a signal-on fluorescent biosensor for detection of OTA based on fluorescent DNA-scaffolded silver-nanocluster (AgNCs), structure-switching of anti-OTA aptamer (Ap) and magnetic beads (MBs), and demonstrate its feasibility in the application of detecting OTA in real samples of wheat. The method exhibits superior sensitivity with a detection limit as low as 2 pg/mL OTA with high specificity. To the best of our knowledge, this is the first attempt to detect OTA based on DNA-scaffolded AgNCs, which possesses relatively high fluorescence quantum yield and photostability with regard to traditional organic dyes and quantum dots. Moreover, combined with the merits of MBs and aptamer, the proposed sensor has many advantages such as fabrication easiness, operation convenience, low cost, and being fast and portable, which may represent a promising path toward routine OTA control.

An immobilization-free electrochemical impedance biosensor based on duplex-specific nuclease assisted target recycling for amplified detection of microRNA.

An immobilization-free electrochemical impedance biosensor for microRNA detection was developed in this work, which was based on both the duplex-specific nuclease assisted target recycling (DSNATR) and capture probes (Cps) enriched from the solution to electrode surface via magnetic beads (MBs). In the absence of miR-21, Cps cannot be hydrolyzed due to the low activity of duplex-specific nuclease (DSN) against ssDNA. Therefore, the intact Cps could be attached to the surface of magnetic glass carbon electrode (MGCE), resulting in a compact negatively charged layer as well as a large charge-transfer resistance. While in the presence of miR-21, it hybridized with Cp to form a DNA-RNA heteroduplex. Due to the considerable cleavage preference for DNA in DNA-RNA hybrids, DSN hydrolyzed the target-binding part of the Cp while liberating the intact miR-21 to hybridize with a new Cp and initiate the second cycle of hydrolysis. In this way, a single miR-21 was able to trigger the permanent hydrolysis of multiple Cps. Finally, all Cps were digested. Thus, the negatively charged layer could not be formed, resulting in a small charge-transfer resistance. By employing the above strategy, the proposed biosensor achieved ultrahigh sensitivity toward miR-21 with a detection limit of 60aM. Meanwhile, the method showed 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 serum samples of breast cancer patients.

A signal amplification electrochemical aptasensor for the detection of breast cancer cell via free-running DNA walker

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 cellsmL(-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.

Label-free fluorescent biosensor based on the target recycling and Thioflavin T-induced quadruplex formation for short DNA species of c-erbB-2 detection

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.

Label-free electrochemical biosensor using home-made 10-methyl-3-nitro-acridone as indicator for picomolar detection of nuclear factor kappa B.

A new acridone derivative 10-methyl-3-nitro-acridone (MNA) with excellent electrochemical activity was synthesized in this paper. Using it as an electrochemical indicator, a signal-on and label-free electrochemical biosensor was developed for picomolar determination of nuclear factor kappa B (NF-κB) in serum. Initially, linear double-stranded DNA (dsDNA) probes, which contain a protein-binding site specific to NF-κB, were self-assembled on the surface of a glass carbon electrode (GCE). If the NF-κB was absent, the dsDNA probes were cut into ss-DNA fragments by the digestion of ExoIII, resulting in a low electrochemical signal of MNA due to the weak binding affinity of MNA to ss-DNA. On the contrary, in the presence of NF-κB, it could bind with the dsDNA probes at the specific site and hinder the digestion of ExoIII, resulting in a significant increase of electrochemical response due to the intercalation of MNA into the dsDNA probes. By employing the above strategy, this sensor could detect as low as 40 pM NF-κB with high specificity. To the best of our knowledge, the proposed sensor is the first attempt to use acridone derivative as an electrochemical indicator for NF-κB detection, which may represent a promising path toward clinical diagnosis and drug developments.

Enzyme-free and label-free fluorescence sensor for the detection of liver cancer related short gene.

Non-invasive early diagnosis of liver cancer is the most effective way to improve the survival rate. In this paper, we developed a label-free and enzyme-free fluorescent biosensor based on target recycling and Thioflavin T (ThT) induced G-quadruplex formation for MXR7 (liver cancer related short gene) detection in human serum. The proposed sensor can detect the target DNA in the concentration range of 0-350fM with the detection limit as low as 10fM. Due to the outstanding structural selectivity of ThT for G-quadruplex, this sensor possesses better discrimination ability and higher sensitivity. Furthermore, this enzyme-free and label-free fluorescence sensor has demonstrated to be capable of detecting target DNA in human serum samples because of its high selectivity and sensitivity. The mechanism employed in this study represents a promising path toward directing liver cancer detection in human serum. In addition, this strategy may be extended to detect other cancer related genes by choosing a rational DNA probe according to different sequences of targets.

A signal-on fluorescent aptasensor based on single-stranded DNA-sensitized luminescence of terbium (III) for label-free detection of breast cancer cells.

Breast cancer is the most common type of malignant tumor in women. Recently, it has been shown that detection of breast cancer tumor cells outside the primitive tumor is an effective early diagnosis with great prognostic and clinical utility. For this purpose, we developed a signal-on fluorescence aptasensor for label-free, facile and sensitive detection of MCF-7 breast cancer cells. Due to target-aptamer specific recognition and single-stranded DNA-sensitized luminescence of terbium (III), the proposed aptasensor exhibits excellent sensitivity with detection limit as low as 70 cells mL(-1). Compared with common organic dyes and the emerging nano-technological probes, the combination of terbium (III) and single-stranded DNA signal probe (Tb(3+)-SP) serves as a more powerful bio-probe because of its stable optical property, good biocompatibility and free from complex synthesis. The feasibility investigations have illustrated the potential applicability of this aptasensor for selective and sensitive detection of MCF-7 breast cancer cells. Moreover, this proposed aptasensor can be also extended for the determination of other tumor cancers or bio-molecules by altering corresponding aptamers. Taken together, this easy-to-perform aptasensor may represent a promising way for early screening and detection of tumor cancers or other bio-molecules in clinical diagnosis.

A photoluminescent biosensor based on long-range self-assembled DNA cascades and upconversion nanoparticles for the detection of breast cancer-associated circulating microRNA in serum samples

A photoluminescent biosensor was developed for the detection of microRNA (miRNA) combined signal amplification of long-range self-assembled DNA cascades with upconversion nanoparticles. The sensor exhibited superior sensitivity with a detection limit of microRNA-21 (miR-21) as low as 1 fM, which may represent the potential of being used in miRNA analysis and clinical diagnosis of breast cancer.