Zonghuang Ye

Combination of cascade chemical reactions with graphene–DNA interaction to develop new strategy for biosensor fabrication

Graphene, a single atom thick and two dimensional carbon nano-material, has been proven to possess many unique properties, one of which is the recent discovery that it can interact with single-stranded DNA through noncovalent π-π stacking. In this work, we demonstrate that a new strategy to fabricate many kinds of biosensors can be developed by combining this property with cascade chemical reactions. Taking the fabrication of glucose sensor as an example, while the detection target, glucose, may regulate the graphene-DNA interaction through three cascade chemical reactions, electrochemical techniques are employed to detect the target-regulated graphene-DNA interaction. Experimental results show that in a range from 5μM to 20mM, the glucose concentration is in a natural logarithm with the logarithm of the amperometric response, suggesting a best detection limit and detection range. The proposed biosensor also shows favorable selectivity, and it has the advantage of no need for labeling. What is more, by controlling the cascade chemical reactions, detection of a variety of other targets may be achieved, thus the strategy proposed in this work may have a wide application potential in the future.

Peptide-based electrochemical biosensor for amyloid β 1–42 soluble oligomer assay

Based on oligopeptide, a novel strategy to fabricate electrochemical biosensor is proposed in this work by fine-tuning the scan pulse frequency of square wave voltammetry (SWV) to synchronize with the surface electron transfer (ET) of the oligopeptide modified on an electrode surface. By using this strategy, the surface ET dynamics of our peptide-based biosensor can show significant difference in the presence and absence of a detection target, thus the proposed strategy has been employed for the assay of amyloid β 1-42 (Aβ 1-42) soluble oligomer, which is among the most neurotoxic species of Aβ peptide. Experimental results reveal that our sensor might be an appropriate candidate for quantitative assay of Aβ 1-42 soluble oligomer. Moreover, the strategy proposed in this work may be extended for the fabrication of more peptide-based biosensors in the future.

A dual-colorimetric signal strategy for DNA detection based on graphene and DNAzyme

In this work, by employing graphene together with a peroxidase-mimic DNAzyme, we have developed a novel dual-colorimetric strategy for DNA detection. In this strategy, a bi-functional probe DNA with both the sequence to have peroxidase activity and the sequence to be complementary to the target DNA is designed. Through π–π stacking, the probe DNA can interact with graphene; however, when the target DNA is present, the graphene-probe DNA interaction will be interrupted, resulting in the peroxidase activity being transferred from the precipitated graphene to the supernatant under centrifugation. Consequently, colorimetric signals can be obtained due to the catalytic reactions by the formed peroxidase-mimic DNAzyme. By observing the changes of the color depth of either the precipitate or the supernate, we are able to detect the target DNA very easily and sensitively with the naked eye. The dual colorimetric signals (signal-off for the precipitate and signal-on for the supernate) can also be integrated through mathematical operations, which may greatly improve the performance of the sensing platform.

Colorimetric copper(II) ion sensor based on the conformational change of peptide immobilized onto the surface of gold nanoparticles

Detection of heavy metal ions has attracted great attention, and the colorimetric assay has remarkable advantages, such as convenient, efficient, free-equipment and always visible. Herein, we report a highly sensitive and selective colorimetric sensor for the determination of copper(II) ions based on the conformational change of Cu2+-binding peptides immobilized onto the surface of gold nanoparticles. In the presence of copper(II) ions, the peptides modified gold nanoparticles (p-AuNPs) will cooperatively bind together, resulting in aggregation and precipitation of the p-AuNPs, thus color change can be observed from wine red to colorless. Nevertheless, other cations like Mg2+, Ca2+, Zn2+, Fe3+, Pb2+, Mn2+, Ba2+, Ni2+, Co2+, K+ and Ag+ cannot have such an effect, so no obvious disturbance occurs in the same concentration to Cu2+. With this well-designed sensing platform, the detection range of copper(II) ions is found to be 10–150 μM, which falls into the maximum accepted level of 1.3 ppm (∼20 μM) as set by the US Environmental Protection Agency. Moreover, modification of AuNPs with differential binding peptides may provide new and simple platforms for the detection of other heavy metal ions, so the strategy proposed for the detection of Cu2+ in this work can be extended for more applications in the future.

Fabrication of magneto-controlled moveable architecture to develop reusable electrochemical biosensors

Electrochemical biosensors have been studied intensively for several decades. Numerous sensing concepts and related interface architectures have been developed. However, all such architectures suffer a trade-off: simple architectures favour usability, whereas complex architectures favour better performance. To overcome this problem, we propose a novel concept by introducing a magneto-controlled moveable architecture (MCMA) instead of the conventional surface-fixed architecture. As a model, human breast cancer cells were used in this study. The results showed that a detection range from 100 to 1 × 106 cells could be achieved. Moreover, the whole detection cycle, including the measurement and the regeneration, could be completed in only 2 min. Thus, usability and excellent performance can be achieved in a single biosensor.

Measurement of intracellular pH changes based on DNA-templated capsid protein nanotubes.

Intracellular pH (pHi) is a fundamental modulator of cell function. Minute changes in pHi may cause great effects in many cellular activities such as metabolism and signal transduction. Herein we report an electrochemical pHi sensor based on viral-coat proteins-DNA nanotubes modified gold electrode. The sensor is pH-sensitive as a result of the pH-dependent electrochemical property of methylene blue (MB) and cell permeable owing to the polyarginine domain of the cowpea chlorotic mottle virus (CCMV) coat protein. Moreover, because the pH sensor can be translocated into cells without any further operations, the measurement of pHi changes can be greatly simplified. The pH sensor has a broad pH spectrum in the pH range from 4.0 to 9.0 and responds rapidly to the pH changes of cells, so it may hold great potential to be a valuable tool to study pH-dependent biological and pathological processes in the future.

Fabrication of a colorimetric biosensing platform for the detection of protein-DNA interaction.

Protein-DNA interaction plays important roles in many cellular processes, and there is an urgent demand for valid methods to monitor the interaction. In view of this, we propose a simple label-free colorimetric platform for the detection of protein-DNA interaction. Protein-DNA couples together with peroxidase-mimicking DNAzyme and exonuclease are elaborately incorporated into an integrated biosensing system. Besides the simplicity and efficiency, the strategy also has a great advantage for its universality in the detection of different protein-DNA couples. In our experiments, effective validation of our approach can be supported by two different protein-DNA couples (estrogen receptor α and nuclear factor kappa B). Experimental results show that the DNAzyme is competent to give rise to evident readout signals to monitor protein-DNA couples. Furthermore, with the substitution of DNA binding sequence in the probe, this method could be extended to a general platform for the detection of protein-DNA interaction.

Electrochemical assay of the relationship between the inhibition of phosphatidylinositol 3-kinase pathway and estrogen receptor expression in breast cancer

Breast cancer has become one of the most threatening diseases to women throughout the world. Emerging evidence implies that estrogen receptor (ER) and phosphatidylinositol 3-kinase (PI3K) pathways play central roles in both breast cancer progression and response to therapy. In this work, we have probed into ER expression related to the PI3K pathway at the protein level with an electrochemical technique based on the detection of ER proteins in nuclear extracts with an Exonuclease III protection-based strategy. Experimental results show that an increased number of ER proteins can be detected upon PI3K inhibition, demonstrating the reversal effect of the PI3K inhibitor on ER expression. Moreover, treatment with different concentrations of the PI3K inhibitor NVP-BEZ235 can result in a dose-dependent alteration of ER protein levels, implying an intimate link between ER and PI3K pathways. This work may be a great help to understand the mysteries underlying PI3K-related endocrine resistance and to evaluate the effect of therapeutic interventions in the future.