2'-Fluoro ribonucleic acid modified DNA dual-probe sensing strategy for enzyme-amplified electrochemical detection of double-strand DNA of PML/RARα related fusion gene.

In the study, a novel sensing strategy based on dual-probe mode, which involved two groups of 2'-fluoro ribonucleic acid (2'-F RNA) modified probes, was designed for the detection of synthetic target double-strand DNA (dsDNA) of PML/RARα fusion genes in APL. And each pair of probes contained a thiolated capture probe (C1 or C2) immobilized on one of electrode surfaces in the dual-channel electrochemical biosensor and a biotinylated reporter probe (R1 or R2). The two groups of 2'-F RNA modified probes were separately complementary with the corresponding strand (Sa or Sb) from target dsDNA in order to prevent renaturation of target dsDNA. Through flanking target dsDNA, two "sandwitch" complexes (C1/Sa/R1 and C2/Sb/R2) were separately shaped by capture probes (C1 and C2) and free reporter probes (R1 and R2) in hybridization solution on the surfaces of different electrodes after the thermal denaturation. The biotin-modified enzyme which produced the measurable electrochemical current signal was localized to the surface by affinity binding between biotin with streptavidin. Under the optimal condition, the biosensor was able to detect 84 fM target dsDNA and showed a good specificity in PBS hybridization solution. Otherwise, the investigations of the specificity and sensitivity of the biosensor were carried out further in the mixed hybridization solution containing different kinds of mismatch sequences as interference background. It can be seen that under a certain interference background, the method still exhibited excellent selectivity and specificity for the discrimination between the fully-complementary and the mismatch sequences. The results of our research laid a good basis of further detection research in practical samples.

Dual-probe electrochemical DNA biosensor based on the "Y" junction structure and restriction endonuclease assisted cyclic enzymatic amplification for detection of double-strand DNA of PML/RARα related fusion gene.

Taking advantage of "Y" junction structure and restriction endonuclease assisted cyclic enzymatic amplification, a dual-probe electrochemical DNA (DE-DNA) biosensor was designed to detect double-stranded DNA (dsDNA) of acute promyelocytic leukemia (APL) related gene. Two groups of detection probes were designed, and each group was composed of a biotinylated capture probe and an assisted probe. They were separately complementary with two strands of target dsDNA in order to prevent the reannealing of the two separate strands from target dsDNA. First, thiol functionalized capture probes (C1 and C2) were severally assembled onto two different gold electrodes, followed by hybridizing with target dsDNA (S1a-S1b) and assistant probes to form two Y-junction-structure ternary complexes. Subsequently, restriction sites on the ternary complexes were digested by Rsa I, which can release S1a, S1b and biotins from the electrode surfaces. Meanwhile, the released S1a and S1b can further hybridize with the unhybridized corresponding detection probes and then initiate another new hybridization-cleavage-separation cycle. Finally, the current signals were produced by the enzyme-catalyzed reaction of streptavidin-horse reddish peroxidase (streptavidin-HRP). The distinct difference in current signals between different sequences allowed detection of target dsDNA down to a low detection limit of 47 fM and presented excellent specificity with discriminating only a single-base mismatched dsDNA sequence. Moreover, this biosensor was also used for assay of polymerase chain reaction (PCR) samples with satisfactory results. According to the results, the power of the DE-DNA biosensor as a promising tool for the detection of APL and other diseases.

Sequence-specific electrochemical detection of double-strand PCR amplicons of PML/RARα fusion gene in acute promyelocytic leukemia.

A novel electrochemical method for the sequence-specific detection of double-stranded polymerase chain reaction (PCR) products of PML/RARα fusion gene in acute promyelocytic leukemia (APL) was described in detail. Based on a "sandwich" sensing mode involving a pair of locked nucleic acids probes (capture probe and reporter probe), this DNA sensor exhibited excellent selectivity and specificity. The direct and quantitative analysis of double-stranded complementary was firstly performed by our sensor without the use of alkali, helicase enzymes, or denaturants. Finally, combining PCR technique with electrochemical detection scheme, PCR amplicons (191 bp) of the PML/RARα fusion gene were obtained and rapidly identified with a low detection limit of 79 fmol in the 100-µL hybridization system. The results clearly showed the power of sensor as a promising tool for the sensitive, specific, and portable detection of APL and other diseases.

Electrochemical biosensor based on nanoporous gold electrode for detection of PML/RARα fusion gene.

In this study, a kind of nanoporous gold electrode (NPG) prepared with repetitive square-wave oxidation reduction cycle (SWORC) was reported. The active surface area of the proposed NPG electrode was 9.9 times larger than that of a bare flat one characterized by cyclic voltammetry (CV). An electrochemical DNA biosensor based on NPG electrode was fabricated for detection of promyelocytic leukemia/retinoic acid receptor α (PML/RARα) fusion gene in acute promyelocytic leukemia (APL) by using Methylene Blue (MB) as an electroactive indicator. Differential pulse voltammetry (DPV) was employed to monitor the hybridization reaction on the probe modified electrode. The decrease of the peak current of MB was observed upon hybridization of the probe with target DNA. The results indicated that the peak current was linear with the concentration of complementary strand in the range of 60 pM to 220 pM with a detection limit of 6.7 pM. This new biosensor exhibited excellent sensitivity and selectivity and had been used for an assay of PCR real sample with a satisfactory result.

Design of a sandwich-mode amperometric biosensor for detection of PML/RARα fusion gene using locked nucleic acids on gold electrode.

In this study, a novel DNA electrochemical probe (locked nucleic acid, LNA) was designed and involved in constructing an electrochemical DNA biosensor for detection of promyelocytic leukemia/retinoic acid receptor alpha (PML/RARα) fusion gene in acute promyelocytic leukemia for the first time. This biosensor was based on a 'sandwich' sensing mode, which involved a pair of LNA probes (capture probe immobilized at electrode surface and biotinyl reporter probe as an affinity tag for streptavidin-horseradish peroxidase (streptavidin-HRP). Since biotin can be connected with streptavidin-HRP, this biosensor offered an enzymatically amplified electrochemical current signal for the detection of target DNA. In the simple hybridization system, DNA fragment with its complementary DNA fragment was evidenced by amperometric detection, with a detection limit of 74 fM and a linear response range of 0.1-10 pM for synthetic PML/RARα fusion gene in acute promyelocytic leukemia (APL). Otherwise, the biosensor showed an excellent specificity to distinguish the complementary sequence and different mismatch sequences. The new pattern also exhibited high sensitivity and selectivity in mixed hybridization system.

An electrochemical biosensor for detection of PML/RARA fusion gene using capture probe covalently immobilized onto poly-calcon carboxylic acid modified glassy carbon electrode.

In this article, the poly-calcon carboxylic acid (poly-CCA) film modified electrode was prepared by cyclic voltammetry (CV). Then, an electrochemical DNA biosensor was developed for detection of PML/RARA fusion gene in acute promyelocytic leukemia (APL) by using 18-mer single-stranded deoxyribonucleic acid as the capture probe. The capture probe was covalently attached through free amines on the DNA bases using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydrosulfosuccinimide (NHS) cross-linking reaction on a carboxylate-terminated poly-CCA monolayer modified glassy carbon electrode (GCE). The covalent immobilized capture probe could selectively hybridize with its target DNA to form double-stranded DNA (dsDNA) on GCE surface. The aim of this work is to provide a well-defined recognition interface for the detection of DNA. Differential pulse voltammetry (DPV) was used to monitor the hybridization reaction on the capture probe electrode. The decrease of the peak current of methylene blue (MB), an electroactive indicator, was observed upon hybridization of the probe with the target DNA. The results indicated that in pH 7.0 phosphate buffer solution (PBS), the oxidation peak current was linear with the concentration of complementary strand in the range of 1.0 x 10(-12) to 1.0 x 10(-11)M with a detection limit of 6.7 x 10(-13)M. This new method demonstrates its excellent specificity for single-base mismatch and complementary sequence (dsDNA) after hybridization, and it would be proposed to use in real sample.

[Selective effect of nispex in inhibiting human cancer cell proliferation and inducing cell apoptosis].

OBJECTIVE: To observe the in vitro anticancer effect of Nispex, the total flavonoids extract from Scurrula parasitic L. METHODS: The cell proliferation inhibitory effects of Nispex on various kinds of tumor cells or non-tumor cells in human and rats were detected with MTT assay and colony forming assay respectively, the cell apoptosis induced by Nispex was detected by AO/EB fluorescence staining, TUNEL assay and AnnexinV-FITC/PI flow cytometry. RESULTS: Nispex could significantly inhibit human cancer cell proliferation and induce human cancer cell apoptosis, especially to the proliferative cell group, but its inhibition on human non-tumor cell was insignificant, and showed no effect on murine cancer cells in the tested scope. CONCLUSION: Nispex is a nature plant extract which shows good selectivity for killing human cancer cell.

[Study on cytotoxic activities on human leukemia cell line HL-60 by flavonoids extracts of Scurrula parasitica from four different host trees].

OBJECTIVE: To compare the anticancer effects of flavonoids extracts of Scurrula parasitica from different host trees in vitro. METHOD: 80% ethanol extracts of S. parasitica parasitizing on Nernium indicum, Morus alba, Opsmanthus fragrans, and Sapindus mulorossi were purified by polyamides column chromatography, and the eluates of 30%, 50%, 70% and 90% ethanol were mixed as flavonoids extracts. Human acute myeloid leukemia cell line HL-60 was used to evaluate the cytotoxicity induced by flavonoids extracts of S. parasitica L with MTT assay. Apoptosis was detected by AO/EB fluorescence staining and DNA fragmentation analysis, apoptosis rates and cell cycle distribution were detected by flow cytometry analysis. RESULT: Extract of S. parasitica parasitizing on N. indicum (NISPEX) was the most sensitive to HL-60 cells of the 4 different host trees, the IC50 value being 0.60 mg x L(-1); and extract of S. parasitica parasitizing on M. alba took the second place, the IC50 value, being 2.49 mg x L(-1); extract of S. parasitica parasitizing on O. fragrans had no effectiveness as high as 50 mg x L(-1) concentration. NISPEX induced HL-60 cell apoptosis and inhibited the cell proliferation in dose and time-dependent manner. Cell cycles were arrested at G0-G1 phase after treated with NISPEX. CONCLUSION: Anticancer effects of S. parasitica correlated with the host trees. Flavonoids extracts of S. parasitica parasitizing on N. indicum exhibited comparatively better anticancer activity in vitro among the host trees studied. NISPEX is found to be a good candidate for anticancer.