Yue He

A graphene oxide-based fluorescent aptasensor for the turn-on detection of epithelial tumor marker mucin 1.

Mucin 1 (MUC1) which presents in epithelial malignancies, is a well-known tumor biomarker. In this paper, a highly sensitive and selective fluorescent aptasensor for Mucin 1 (MUC1) detection is constructed, utilizing graphene oxide (GO) as a quencher which can quench the fluorescence of single-stranded dye-labeled MUC1 specific aptamer. In the absence of MUC1, the adsorption of the dye-labeled aptamer on GO brings the dyes in close proximity to the GO surface resulting in high efficiency quenching of dye fluorescence. Therefore, the fluorescence of the designed aptasensor is completely quenched by GO, and the system shows very low background fluorescence. Conversely, and very importantly, upon the adding of MUC1, the quenched fluorescence is recovered significantly, and MUC1 can be detected in a wide range of 0.04-10 μM with a detection limit of 28 nM and good selectivity. Moreover, the results have also been verified for real sample application by testing 2% serum containing buffer solution spiked with a series of concentrations of MUC1.

Graphene Oxide-Based Fluorescent Biosensor for Protein Detection via Terminal Protection of Small-Molecule-Linked DNA

A fluorescence method for protein detection is developed based on terminal protection of small-molecule-linked DNA by target protein and a graphene oxide-assisted DNA assay strategy. This design results in fluorescence-enhanced detection that is sensitive and selective for the target protein.

An ultra-high sensitive platform for fluorescence detection of micrococcal nuclease based on grapheneoxide

Micrococcal nuclease (MNase) is the extracellular nuclease of Staphylococcus aureus (S. aureus). It preferentially digests single-stranded nucleic acids. The existence of MNase can be the standard to identify S. aureus and the content of MNase can be used to evaluate the pathogenicity of S. aureus. Herein, an ultra-high sensitive and selective fluorescent sensing platform for MNase is developed based on MNase-induced DNA strand scission and the difference in affinity of graphene oxide (GO) for single-stranded DNA containing different numbers of bases in length. In the absence of MNase, the adsorption of the dye-labeled ssDNA on GO makes the dyes close proximity to GO surface resulting in high efficiency quenching of fluorescence of the dyes. Conversely, and very importantly, in the presence of MNase, it cleaves the dye-labeled ssDNA into small fragments. The introduction of GO into the sensing solution results in weak quenching of the fluorescence of the dyes due to the weak affinity of the short dye-labeled oligonuleotide fragment to GO, and the fluorescence intensity gradually increases with increasing concentration of MNase. MNase can be detected in a range of 8×10⁻⁵ to 1.6×10⁻³ unit/mL with a detection limit of 2.7×10⁻⁵ unit/mL and good selectivity. The detection limit is of two orders of magnitude lower than those reported fluorescence MNase assays. Moreover, when the GO-based biosensor is used in S. aureus sample assays, preeminent fluorescence signals are obtained, thus the platform of the GO-based biosensor can be used to detect MNase in real-world samples.

In situ spectral imaging of marker proteins in gastric cancer with near-infrared and visible quantum dots probes

This study presents the investigation of bioconjugating ability of near-infrared (NIR) CdSeTe/ZnS quantum dots (QDs) (710 nm) and visible CdSe QDs (595 nm) in immunofluorescent staining for cancer biomarkers in gastric cancer tissues probed with the homemade Hadamard transform (HT) spectral imaging microscope and a commercial multispectral imaging system. The results show that imunostaining ability of NIR QDs probes is stronger than that of visible QDs when the two kinds of QDs are simultaneously used to probe the cancer biomarkers such as cytokeratin 20 (CK20) and proliferating cell nuclear antigen (PCNA) in gastric cancer tissues. Moreover, when the two QDs probes are used for immunostaining successively for the same target molecules, staining order has great influences on the final results due to their different conjugating ability to the marker proteins. The results imply that NIR QDs hold more promise for real-time imaging of tumor tissues due to its higher sensitivity and contrast. In addition, the results also demonstrate the potential of Hadamard transform spectral imaging as a useful tool in biomedical analysis and quantitative evaluation for tumor tissues.

Evaluation of the Bioconjugation Efficiency of Different Quantum Dots as Probes for Immunostaining Tumor-Marker Proteins

The differing bioconjugation efficiencies of quantum dots (QDs) are a practical obstacle to their popularization. Differences in bioconjugation efficiency based on immunostaining the same targeted molecules using different batches of QDs need to be evaluated prior to their application. In this paper, a quantitative method for evaluating the efficiency of QDs in staining tissues has been developed based on Hadamard transform (HT) spectral imaging. Proliferating cell nuclear antigens (PCNA) in breast cancer tissues were labeled with bioconjugated QD bioprobes using a 454 nm laser as the light source for fluorescence spectral imaging. Four-dimensional (4D) spectral imaging analysis of PCNA in cell nuclei was carried out using HT spectral microscopy based on immunostaining with different batches of QDs. The fluorescence intensity distributions in the cell nuclei were collected from the 4D images. Based on the information obtained from microscopic spectra and 4D images, differences in the bioconjugation efficiency among different batches of QDs were evaluated. The results demonstrate that it is possible to maintain uniform bioconjugation efficiencies with different QD bioconjugation processes in order to obtain accurate and reliable results in biomedical analysis and cancer diagnosis.

Analysis of Cancer Marker in Tissues with Hadamard Transform Fluorescence Spectral Microscopic Imaging

Quantum dots (QDs) probes were used to tag and trace cancer biomarkers in cancer tissues based on the system of home-made Hadamard transform (HT) spectral microscopic imaging, which can be applied to provide high-resolution fluorescence spectrum and image of single cells and tissues. In situ fluorescence imaging for cancer marker proteins, such as estrogen receptor (ER), human epidermal growth factor receptor 2 (HER2), proliferating cell nuclear antigen (PCNA) and cytokeratin 20 (CK20) in tumor tissues, were realized by using the HT system to capture quantitative information for these proteins when tumor tissues were immunostained with QDs probes. A method to evaluate tumor malignancy of the specimens based on in situ analysis of distribution of marker proteins was proposed based on the comparative study of positive samples and negative controls. The investigation of ER contents of the cores in breast cancer tissue microarrays (TMAs) shows that the technique of QDs-immunohistochemistry (IHC)/HT spectral imaging is more sensitive than conventional IHC method. The results also demonstrate that the QDs-IHC/HT spectral imaging technique can be applied to visualize and quantitatively measure the subcellular molecules inside tumor tissues, and the coupling of HT spectral imaging to the probing of subcellular molecules with QDs has great potential in biology and medical diagnosis.