Tellurium doped zinc imidazole framework (Te@ZIF-8) for quantitative determination of hydrogen peroxide from serum of pancreatic cancer patients.

The tellurium doped zinc imidazole framework (Te@ZIF-8) is prepared by a two-step hydrothermal strategy for the electrochemical sensing of hydrogen peroxide. Material is characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The electrochemical characterization of the MOF modified electrode is done by a three-electrode system. Electrochemical sensing of hydrogen peroxide is made by cyclic voltammetry, amperometry, and impedance measurements. Results demonstrate that Te@ZIF-8 shows a detection limit of 60 µM with linearity up to 0.98855. Material is stable to 1000 cycles with no significant change in electrochemical response. Amperometry depicts the recovery of hydrogen peroxide from human serum up to 101%. Impedance curve reveals the surface of Te@ZIF-8-GCE (glassy carbon electrode) as porous and rough and an interface is developed between analyte ions and the sensing material. Finally, the modified electrode is used for the quantitative determination of hydrogen peroxide from serum samples of pancreatic cancer patients, diagnosed with CA 19-9.

Improving the reproducibility, accuracy, and stability of an electrochemical biosensor platform for point-of-care use.

Electrochemical biosensors possess numerous desirable qualities for target detection, such as portability and ease of use, and are often considered for point-of-care (POC) development. Label-free affinity electrochemical biosensors constructed with semiconductor manufacturing technology (SMT)-produced electrodes and a streptavidin biomediator currently display the highest reproducibility, accuracy, and stability in modern biosensors. However, such biosensors still do not meet POC guidelines regarding these three characteristics. The purpose of this research was to resolve the limitations in reproducibility and accuracy caused by problems with production of the biosensors, with the aim of developing a platform capable of producing devices that exceed POC standards. SMT production settings were optimized and bioreceptor immobilization was improved through the use of a unique linker, producing a biosensor with exceptional reproducibility, impressive accuracy, and high stability. Importantly, the three characteristics of the sensors produced using the proposed platform all meet POC standards set by the Clinical and Laboratory Standards Institute (CLSI). This suggests possible approval of the biosensors for POC development. Furthermore, the detection range of the platform was demonstrated by constructing biosensors capable of detecting common POC targets, including circulating tumor cells (CTCs), DNA/RNA, and curcumin, and the devices were optimized for POC use. Overall, the platform developed in this study shows high potential for production of POC biosensors.

Target induced framework nucleic acid nanomachine with doxorubicin-spherical nucleic acid tags for electrochemical determination of human telomerase activity.

A stable and enzyme-free method is described for highly sensitive determination of telomerase activity. It is based on the use of a framework nucleic acid (FNA) nanomachine and doxorubicin-spherical nucleic acid (DSNA) tags. Upon incubation with telomerase, the primer-tetrahedron becomes elongated to form the handed swing arm. The extended swing arm autonomously moves along the predefined track consisting of entropy-tetrahedron by consecutive strand displacement under the aid of fuel-tetrahedron. As a result, many (entropy-tetrahedron)-(fuel-tetrahedron) complexes are assembled for combining the DSNA tags. This results in an amplified electrochemical signal, typically measured at around -0.63 V (Ag/AgCl). The use of an enzyme-free FNA nanomachine and of DSNA tags warrants outstandingly high stability and sensitivity. The method shows a broad dynamic correlation of telomerase activity in cell extracts. The analytical range extends from 10 to 1.0 × 104 HeLa cells mL-1 with a lower detection limit of 2 cells mL-1. The differences in telomerase activity between different cancer cells can be easily evaluated. The method was further verified by quantifying telomerase activity of cancer cells in accumulated normal cells. Therefore, the sensing method has great potential for clinical application. Graphical abstractSchematic representation of the electrochemical biosensor based on target induced framework nucleic acid nanomachine with doxorubicin-spherical nucleic acids (DSNA) tags, which can be used to the determination of telomerase activity in accumulated normal cells. dNTP: Deoxynucleotide triphosphates; FT: Fuel-tetrahedron.

Ultrasensitive amperometric immunosensor for the prostate specific antigen by exploiting a Fenton reaction induced by a metal-organic framework nanocomposite of type Au/Fe-MOF with peroxidase mimicking activity.

To increase the sensitivity of electrochemical sensor, Fe-MIL-88B-NH2 (Fe-MOF) with peroxidase-like activity is designed for the construction of immunoprobe. The Fe-MOF was prepared by one-step hydrothermalf method using 2-aminoterephthalic acid and iron(III) chloride. For the immunoprobe, it was fabricated by gold nanocomposite/Fe-MOF (Au/Fe-MOF) for the immobilization of labeling antibody (the antibody was used to conjuncting with label materials). The thin layer of Methylene Blue (MB) covered by reduced graphene oxide-gold nanocomposites (Au-rGO) serves as a substrate to covalently fix coating antibodies. The MB as a redox-active species was modified on the glass carbon electrode that can give a strong amperometric signal at 0.18 V (vs. Ag/AgCl). With the participation of H2O2, Fe-MOF can induce the Fenton reaction which degrades MB covered by Au-rGO on the substrate. The rest of MB on the surface of electrode becomes oxidized thereby generating a current signal. Square wave voltammetry (SWV) was used to quantify PSA. Under optimal conditions, the immunoassay is stable, specific and reproducible. It has a lower detection limit of 0.13 pg mL-1 (S/N = 3) and a wide analytical range that extends from 0.001 to 100 ng mL-1. Graphical abstractA sandwich-type amperometric immunoassay based on Fe-MOF-induced Fenton reaction was designed for sensitive determination of prostate specific antigen.

A quantitative method for detection of circulating fms related tyrosine kinase 3 (FLT-3) in acute myeloid leukemia (AML) patients.

FMS related tyrosine kinase 3 (FLT-3) is a tyrosine kinase expressed in early hematopoietic precursor cells and has roles in survival, proliferation, and differentiation. Bone marrow expression and mutagenic analysis of FLT-3 in Acute Myeloid Leukemia (AML) patients is well-characterized. However, the levels of circulating FLT-3 in serum have not been previously described. In this study we describe a quantitative electrochemiluminescent immunoassay that detects FLT-3 in human serum. Using this method we find that AML patients have elevated levels of circulating FLT-3 and these levels correlated to the percent blast counts in the bone marrow (BM).

Gold nanoparticles conjugated to bimetallic manganese(II) and iron(II) Prussian Blue analogues for aptamer-based impedimetric determination of the human epidermal growth factor receptor-2 and living MCF-7 cells.

An aptamer-based assay is described for the determination of trace levels of the cancer marker human epidermal growth factor receptor-2 (HER2) and living MCF-7 cells. The method is based on the use of a bimetallic MnFe Prussian blue analogue coupled to gold nanoparticles (MnFePBA@AuNP). Compared to pristine MnFe PBA nanocubes, the series of MnFePBA@AuNP exhibits a core-shell spherical nanostructure, and the shell thickness decreases from 99.9 nm down to 49.3 nm on increasing the fraction of AuNPs. The composite was placed on a gold electrode and incubated with the aptamer solution through electrostatic interaction. Then the modified electrode was employed to detect HER2 and MCF-7 cells using [Fe(CN)6]3-/4- as redox probe and displays good responses to both of them. Electrochemical impedance spectroscopy data show that the signal variation between each step during the whole procedure for the HER2 and MCF-7 cells detection can be embodied as the resistance value change between the [Fe(CN)6]3-/4- and electrode surface. The assay has a very low detection limit (0.247 pg∙mL-1) and works in the 0.001-1.0 ng∙mL-1 HER2 concentration range. It was also used to sense HER2 in MCF-7 cells, and this results in an assay that works within the 500-5 × 104 cell∙mL-1 cell concentration range and a 36 cell∙mL-1 detection limit. Furthermore, the aptamer-based assay is selective, acceptably reproducible, stable, and well feasible for the detection of HER2 and living MCF-7 cells in human serum. Graphical abstract Schematic of an electrochemical aptasensor based on the bimetallic MnFe Prussian blue analogue (MnFe PBA) coupling with gold nanoparticles (represented by MnFePBA@AuNPs). It was employed as the aptasensor for human epidermal growth factor receptor-2 (HER2), and living MCF-7 cells.

Light-driven ultrasensitive self-powered cytosensing of circulating tumor cells via integration of biofuel cells and a photoelectrochemical strategy.

Herein, a light-driven, membrane-less and mediator-less self-powered cytosensing platform via integration of biofuel cells (BFCs) and a photoelectrochemical strategy was developed for ultrasensitive detection of circulating tumor cells (CTCs). To construct cytosensors, an elaborately designed SH-Sgc8c aptamer/AuNP/g-C3N4 photoelectrode was used as an alternative anode for glucose oxidation, avoiding the introduction of anodic enzymes. Initially, glucose could favorably reach the photoanode surface and be easily oxidized by the photogenerated holes, while the photogenerated electrons would transfer to the biocathode and achieve biocatalytic reduction of O2, leading to a high EOCV. However, in the presence of CTCs, they could preferentially interact with the Sgc8c aptamer via specific recognition, and then complexes with large steric hindrance were immobilized on the photoanode surface, which could greatly affect the electron transfer between glucose and the photoanode surface. In this case, the EOCV decreased sharply. Encouragingly, this self-powered cytosensor exhibited an ultrasensitive response to the target CTCs in a wide concentration range from 20 to 2 × 105 cells mL-1 with a low detection limit of 10 cells mL-1 (S/N = 3), being superior to those of the reported methods. Moreover, this as-proposed self-powered cytosensor integrated with a photoelectrochemical strategy possessed unique advantages of not requiring an external power source, being anodic enzyme-free, having a simple construction process, facile miniaturization, and high selectivity and sensitivity, providing a promising and powerful tool for fundamental biochemical research and clinical diagnosis.

Electrochemical immunosensor for CDH22 biomarker based on benzaldehyde substituted poly(phosphazene) modified disposable ITO electrode: A new fabrication strategy for biosensors.

A novel label-free impedimetric immunosensor was fabricated for rapid, selective and sensitive detection and quantification of Cadherin-like protein 22 (CDH22), a cancer marker, in human serum by using easy and quickly prepared disposable ITO immunoelectrode. cancer marker, in human serum by using easy and quickly prepared disposable ITO immunoelectrode. The biosensing approach implied the use of ITO electrode coated with poly(phosphazene) polymer including benzaldehyde groups attached with CDH22 antibody and CDH22 antigens. Benzaldehyde side groups containing poly(phosphazene) film coated disposable ITO electrode were utilized as an immunosensing platform and anti-CDH22 antibodies bound to aldehyde groups of benzaldehyde substituted poly(phosphazene) (P-PHP) covalently. The immunosensor modification steps and affinity interaction between anti-CDH22 antibodies and CDH22 antigens were observed by EIS and CV in the presence of the redox couple. Furthermore, antibody immobilization was followed via FTIR and Raman spectroscopy. The morphological analyses of the suggested immunosensor during the fabrication steps were carried out with SEM and AFM monitoring. All the experimental parameters affecting the construction of the immunoelectrodes were optimized. The fabricated immunosensor exhibited an excellent working performance with a wide detection linear range (0.015-2.9 pg/mL) and low limit of detection (4.4 fg/mL). Moreover, the proposed immunosensor had great reproducibility, repeatability and long-term stability. Additionally, the fabricated immunosensor was successfully used in the quantification of CDH22 in human serum without any pretreatment.

An aptamer biosensor for leukemia marker mRNA detection based on polymerase-assisted signal amplification and aggregation of illuminator.

A novel electrochemical luminescence (ECL) aptamer biosensor via polymerase amplification is constructed for label-free detection of leukemia marker mRNA (miR-16). In order to achieve the ultrasensitive detection of the target mRNA, the cyclic target chain displacement polymerization of leukemia marker mRNA assisted with Klenow fragment of DNA polymerase is employed. The determination is carried out by recording the ECL emission of pyridine ruthenium (Ru(bpy)32+) complexes embedded into the assistance DNA (ADNA) loaded on the nanogold surface, after the hybridization reaction between the probe DNA (PDNA) and the remaining sequence of the CP's stem part, and the formation of a core-shell sun-like structure. The mercapto-modified capture DNA (CP) is immobilized on the surface of a magneto-controlled glassy carbon electrode by Au-S bond. The CP is opened and hybridized with the target mRNA to form double-stranded DNA. In the presence of polymerase, primer DNA, and bases (dNTPs), the primer chain gets access to its complementary sequence of the stem part and then triggers a polymerization of the DNA strand, leading to the release of mRNA and starting the next polymerization cycle. Finally, the composite of PDNA-covered and ADNA-covered (embedded with Ru(bpy)32+) gold nanoparticles (hereafter called AuNPs@(PDNA+ADNA-Ru(bpy)32+) is added, and the ECL intensity is recorded. Because of the polymerization cycle and the aggregation of the illuminator of Ru(bpy)32+, the detected signal is amplified significantly. The results showed that the corresponding ECL signal has a good linear relationship with a logarithm of target mRNA concentration in the range of 1 × 10-16 to 1 × 10-7 mol/L, with a detection limit of 4.3 × 10-17 mol/L. The mRNA spiked in the human serum sample is determined, and the recoveries are from 97.2 to 102.0%. This sensor demonstrates good selectivity, stability, and reproducibility. Graphical abstract ᅟ.

Determination of the antioxidant propyl gallate in meat by using a screen-printed electrode modified with CoSe2 nanoparticles and reduced graphene oxide.

A voltammetric sensor is described for the quantitation of propyl gallate (PG). A screen-printed carbon electrode (SPCE) was modified with reduced graphene sheets that were decorated with cobalt diselenide nanoparticles (CoSe2@rGO). The material was hydrothermally prepared and characterized by several spectroscopic techniques. The modified SPCE displays excellent electrocatalytic ability towards PG. Differential pulse voltammetry, with a peak voltage at 0.34 V (vs. Ag/AgCl) has a sensitivity of 12.84 µA·µM-1·cm-2 and a detection limit as low as 16 nM. The method is reproducible, selective, and practical. This method was applied to the determination of PG in spiked meat samples, and the result showed an adequate recovery. Graphical abstract Schematic of a new method for fast and sensitive electrochemical determination of the food additive propyl gallate in meat.

Definition of reference ranges for ß-isomerized carboxy-terminal telopeptide collagen type I for children and adolescents.

BACKGROUND: Bone metabolism involves many complex pathways that are disturbed by several bone diseases. The literature shows some limitations concerning pediatric reference intervals to bone markers, mainly because of the low number of patients included in the studies, the heterogeneity of methods, beyond the fact that it is time-consuming and expensive. The aim of this study was to determine reference values for ß-isomerized carboxy-terminal telopeptides collagen type I (ß-CTX), a marker of bone resorption, for children and adolescents. METHODS: Blood samples from 246 patients were collected and ß-CTX was measured using an electrochemiluminescence immunoassay (ECLI). RESULTS AND CONCLUSIONS: We propose reference ranges for ß-CTX concentration from the 2.5 percentile and 97.5 percentile for each age group. The reference values obtained, concerning children and adolescents, might be useful in the evaluation of diseases such as osteosarcoma and anorexia in both childhood as adolescence.

Evaluation of two strategies for the interpretation of tumour markers in pleural effusions.

BACKGROUND: Pleural effusions present a diagnostic challenge. Approximately 20% are associated with cancer and some 50% require invasive procedures to perform diagnosis. Determination of tumour markers may help to identify patients with malignant effusions. Two strategies are used to obtain high specificity in the differential diagnosis of malignant pleural effusions: a) high cut-off, and b) fluid/serum (F/S) ratio and low cut-off. The aim of this study is to compare these two strategies and to establish whether the identification of possible false positives using benign biomarkers - ADA, CRP and % of polymorphonuclear cells - improves diagnostic accuracy. METHODS: We studied 402 pleural effusions, 122 of them malignant. Benign biomarkers were determined in pleural fluid, and CEA, CA72-4, CA19-9 and CA15-3 in pleural fluid and serum. RESULTS: Establishing a cut-off value for each TM for a specificity of 100%, a joint sensitivity of 66.5% was obtained. With the F/S strategy and low cut-off points, sensitivity was 77% and specificity 98.2%, Subclassifying cases with negative benign biomarkers, both strategies achieved a specificity of 100%; sensitivity was 69.9% for single determination and 80.6% for F/S ratio. CONCLUSIONS: The best interpretation of TM in the differential diagnosis of malignant pleural effusions is obtained using the F/S ratio in the group with negative benign biomarkers.

Impedimetric PSA aptasensor based on the use of a glassy carbon electrode modified with titanium oxide nanoparticles and silk fibroin nanofibers.

This article describes an impedimetric aptasensor for the prostate specific antigen (PSA), a widely accepted prostate cancer biomarker. A glassy carbon electrode (GCE) was modified with titanium oxide nanoparticles (TiO2) and silk fibroin nanofiber (SF) composite. The aptasensor was obtained by immobilizing a PSA-binding aptamer on the AuNP-modified with 6-mercapto-1-hexanol. The single fabrication steps were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The assay has two linear response ranges (from 2.5 fg.mL-1 to 25 pg.mL-1, and from 25 pg.mL-1 to 25 ng.mL-1) and a 0.8 fg.mL -1 detection limit. After optimization of experimental conditions, the sensor is highly selective for PSA over bovine serum albumin and lysozyme. It was successfully applied to the detection of PSA in spiked serum samples. Graphical abstract Schematic of the fabrication of an aptasensor for the prostate specific antigen (PSA). It is based on the use of a glassy carbon electrode modified with gold nanoparticles and titanium oxide-silk fibroin. The immobilization process of aptamer and interaction with PSA were followed by electrochemical impedance spectroscopy technique.

The dopant type and amount governs the electrochemical performance of graphene platforms for the antioxidant activity quantification.

Graphene doped with heteroatoms can show new or improved properties as compared to the original undoped material. It has been reported that the type of heteroatoms and the doping conditions can have a strong influence on the electronic and electrochemical properties of the resulting material. Here, we wish to compare the electrochemical behavior of two n-type and two p-type doped graphenes, namely boron-doped graphenes and nitrogen-doped graphenes containing different amounts of heteroatoms. We show that the boron-doped graphene containing a higher amount of dopants provides the best electroanalytical performance in terms of calibration sensitivity, selectivity and linearity of response for the detection of gallic acid normally used as the standard probe for the quantification of antioxidant activity of food and beverages. Our findings demonstrate that the type and amount of heteroatoms used for the doping have a profound influence on the electrochemical detection of gallic acid rather than the structural properties of the materials such as amounts of defects, oxygen functionalities and surface area. This finding has a profound influence on the application of doped graphenes in the field of analytical chemistry.

Highly sensitive electrochemical detection of DNA hybridisation by coupling the chemical reduction of a redox label to the electrode reaction of a solution phase mediator.

We have described a highly sensitive method for detecting DNA hybridisation using a redox-labeled stem loop probe. The redox labels were poly(styrene-co-acrylic) (PSA) spheres of 454 nm diameter, modified by methylene blue (MB) deposited alternatively with poly(sodium 4-styrene sulphonate) (PSS) in a layer-by-layer process. Each PSA sphere carried approx. 3.7 × 10(5) molecules of MB, as determined optically. DIG-tagged stem loop probes were immobilised on screen printed electrodes bearing anti-DIG antibodies. Binding with the target enabled straightening of the stem loop, which made attachment to the MB-coated PSA spheres possible. For measuring the current from the direct reduction of MB by differential pulse voltammetry, a 30 mer DNA target common to 70 strains of Escherichia coli was calibrated across the range 1.0 fM to 100 pM (gradient = 3.2 × 10(-8) A (log fM)(-1), r(2) = 0.95, n = 60), with an LOD of ∼58 fM. By using Fe(CN)6(3-/4-) as a solution phase mediator for the MB reduction, we were able to lower the LOD to ∼39 aM (gradient = 5.95 × 10(-8) A (log aM)(-1), r(2) = 0.96, n = 30), which corresponds to the detection of 0.76 ag (∼50 molecules) in the 2 µL analyte sample. We hypothesise that the lowering of the LOD was due to the fact that not all the MB labels were able to contact the electrode surface.

Neurochemical measurement of adenosine in discrete brain regions of five strains of inbred mice.

Adenosine (ADO), a non-classical neurotransmitter and neuromodulator, and its metabolites adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP), have been shown to play an important role in a number of biochemical processes. Although their signaling is well described, it has been difficult to directly, accurately and simultaneously quantitate these purines in tissue or fluids. Here, we describe a novel method for measuring adenosine (ADO) and its metabolites using high performance liquid chromatography with electrochemical detection (HPLC-ECD). Using this chromatographic technique, we examined baseline levels of ADO and ATP, ADP and AMP in 6 different brain regions of the C57BL/6J mouse: stratum, cortex, hippocampus, olfactory bulb, substantia nigra and cerebellum and compared ADO levels in 5 different strains of mice (C57BL/6J, Swiss-Webster, FVB/NJ, 129P/J, and BALB/c). These studies demonstrate that baseline levels of purines vary significantly among the brain regions as well as between different mouse strains. These dissimilarities in purine concentrations may explain the variable phenotypes among background strains described in neurological disease models.

Application of graphene-ionic liquid-chitosan composite-modified carbon molecular wire electrode for the sensitive determination of adenosine-5'-monophosphate.

In this paper, a graphene (GR) ionic liquid (IL) 1-octyl-3-methylimidazolium hexafluorophosphate and chitosan composite-modified carbon molecular wire electrode (CMWE) was fabricated by a drop-casting method and further applied to the sensitive electrochemical detection of adenosine-5'-monophosphate (AMP). CMWE was prepared with diphenylacetylene (DPA) as the modifier and the binder. The properties of modified electrode were examined by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical behaviors of AMP was carefully investigated with enhanced responses appeared, which was due to the presence of GR-IL composite on the electrode surface with excellent electrocatalytic ability. A well-defined oxidation peak of AMP appeared at 1.314 V and the electrochemical parameters were calculated by electrochemical methods. Under the selected conditions, the oxidation peak current of AMP was proportional to its concentration in the range from 0.01 µM to 80.0 µM with the detection limit as 3.42 nM (3σ) by differential pulse voltammetry. The proposed method exhibited good selectivity and was applied to the detection of vidarabine monophosphate injection samples with satisfactory results.

Rethinking data collection and signal processing. 2. Preserving the temporal fidelity of electrochemical measurements.

Direct electrochemical measurements of biological events are often challenging because of the low signal relative to the magnitude of the background and noise. When choosing a data processing approach, the frequency and phase content of the data must be considered. Here, we employ a zero-phase (infinite impulse response (IIR)) filter to remove the noise from the analytical signal, while preserving the phase content. In fast-scan cyclic voltammetry, the frequency content of the signal is a function of the scan rate of the applied waveform. Fourier analysis was used to develop a relationship between scan rate and the filter cutoff frequency to maximize the reduction in noise, while not altering the true nature of the analytical signal. The zero-phase filter has the same effect as traditional filters with regards to increasing the signal-to-noise ratio. Because the zero-phase filter does not introduce a change to ΔEpeak, the heterogeneous electron rate transfer constant (0.10 cm/s) for ferrocene is calculated accurately. The zero-phase filter also improves electrochemical analysis of signaling molecules that have their oxidation potential close to the switching potential. Lastly, a quantitative approach to filtering amperometric traces of exocytosis based on the rise time was developed.

An ultrasensitive iron(III)-complex based hydrogen peroxide electrochemical sensor based on a nonelectrocatalytic mechanism.

In this communication, the first nonelectrocatalysis-type hydrogen peroxide electrochemical sensor is reported. The electroactive iron(III) diethylenetriaminepentaacetic acid (DTPA-Fe(III)) complex is immobilized on the cysteamine (cys) modified nanoporous gold (NPG) films by covalent method. The immobilized DTPA-Fe(III) complex quickly communicates an electron with the electrode. Upon addition of hydrogen peroxide, however, hydrogen peroxide inhibits the direct electron transfer of the DTPA-Fe(III) complex due to the generation of nonelectroactive DTPA-Fe(III)-H2O2 complex. Based on quenching mechanism, the first hydrogen peroxide electrochemical sensor based on a nonelectrocatalytic mechanism is developed. The novel hydrogen peroxide electrochemical sensor has the ultralow detection limit (1.0×10(-14) M) and wide linear range (1.0×10(-13) to 1.0×10(-8) M) with excellent reproducibility and stability.

Aptamer based strategy for cytosensing and evaluation of HER-3 on the surface of MCF-7 cells by using the signal amplification of nucleic acid-functionalized nanocrystals.

The electrochemical detection of cell lines of MCF-7 (human breast cancer) has been reported, using magnetic beads for the separation tool and high-affinity DNA aptamers for signal recognition. The high specificity was obtained by using the magnetic beads and aptamers, and the good sensitivity was realized with the signal amplification of DNA capped CdS or PbS nanocrystals. The ASV (anodic stripping voltammetry) technology was employed for the detection of cadmic cation and lead ions, for electrochemical assay of the amount of the target cells and biomarkers on the membrane of target cells, respectively. This electrochemical method could respond to as low as 100 cells mL(-1) of cancer cells with a linear calibration range from 1.0×10(2) to 1.0×10(6) cells mL(-1), showing very high sensitivity. Moreover, the amounts of HER-3 which were overexpressed on MCF-7 cells were calculated correspond to be 3.56×10(4) anti-HER-3 antibody molecules. In addition, the assay was able to differentiate between different types of target and control cells based on the aptamers and magnetic beads used in the assay, indicating the wide applicability of the assay for early and accurate diagnose of cancers.