Guifang Chen

Interaction between curcumin and mimetic biomembrane

Curcumin, a major bioactive compound in turmeric, has a broad spectrum of antioxidant, anticarcinogenic, antimutagenic and anti-inflammatory properties. At the molecular level, curcumin modulates many structurally unrelated membrane proteins through several signaling pathways. Curcumin has been suggested to change the properties of cell membranes and affect the membrane-bound proteins indirectly; however, the detailed mechanism has yet to be investigated. In this paper, self-assembled bilayer lipid membranes are artificially constructed on the surface of a gold electrode to mimic biomembranes, and interaction between the supported membranes and curcumin is studied electrochemically. Results show that curcumin interacts with the membranes strongly, in a concentration-dependent manner. At low concentrations, curcumin tends to insert into the outer monolayer only, while at high concentrations, it may also begin to penetrate the inner monolayer. The results obtained in this work may enhance our understanding of the effect of curcumin, and possibly flavonoids, on cell membranes and membrane proteins.

Direct application of gold nanoparticles to one-pot electrochemical biosensors

Gold nanoparticles (AuNPs) have been widely employed for the fabrication of electrochemical biosensors. In most cases, AuNPs are immobilized on the surface of an electrode, so they are difficult to be regenerated, making the use of the biosensor unfriendly. In this work, by adopting AuNPs directly as the electrolytes, we have developed a novel AuNPs-based electrochemical detection system. In brief, AuNPs-catalyzed oxidation of glucose is combined with a HRP-catalyzed reaction as well as an electrocatalytic reaction to compose cascade reactions in the electrolyte. Thus, the intensity of the electrocatalytic signals has quantitative relation with the concentration of glucose, and favors the sensitive detection of glucose. Furthermore, because the catalysis of AuNPs may be blocked under the interaction with single-stranded DNA and unblocked in the presence of a complementary sequence, detection of DNA and even single-nucleotide polymorphism can thereby been achieved. This one-pot detection system can be operated and regenerated very easily, since all the components are integrated in the electrolytes of AuNPs, and the unmodified electrode can be reused after being rinsed. This concept by integrating the advantages of sensitive electrochemical detection with the easy-to-operate nanocolloidal system may also promote the development of other kinds of electrochemical biosensors.

Fabrication of nanozyme@DNA hydrogel and its application in biomedical analysis

Nanozymes have received great attention owing to the advantages of easy preparation and low cost. Unlike natural enzymes that readily adapt to physiological environments, artificial nanozymes are apt to passivate in complex clinical samples (e.g., serum), which may damage the catalytic capability and consequently limit the application in biomedical analysis. To conquer this problem, in this study, we fabricated novel nanozyme@DNA hydrogel architecture by incorporating nanozymes into a pure DNA hydrogel. Gold nanoparticles (AuNPs) were adopted as a model nanozyme. Results indicate that AuNPs incorporated in the DNA hydrogel retain their catalytic capability in serum as they are protected by the hydrogel, whereas AuNPs alone totally lose the catalytic capability in serum. The detection of hydrogen peroxide and glucose in serum based on the catalysis of the AuNPs@DNA hydrogel was achieved. The detection limit of each reaches 1.7 and 38 μM, respectively, which is equal to the value obtained using natural enzymes. Besides the mechanisms, some other advantages, such as recyclability and availability, have also been explored. This nanozyme@DNA hydrogel architecture may have a great potential for the utilization of nanozymes as well as the application of nanozymes for biomedical analysis in complex physiological samples.

Synthesis of ovalbumin-stabilized highly fluorescent gold nanoclusters and their application as an Hg2+ sensor

Biomolecule-functionalized fluorescent gold nanoclusters (AuNCs) have attracted a lot of attention because of their good biocompatibility and considerable environmental/cost advantages. Recently, some proteins rich in tyrosine and cysteine have been proven to work as templates for the direct synthesis of AuNCs under alkaline conditions. However, the low quantum yield (QY) of AuNCs is still a restraining factor, which constrains its wide applications. In this study, highly fluorescent AuNCs have been synthesized in a basic aqueous solution using ovalbumin (OVA) as both a reducing and stabilizing agent. The QY of the ovalbumin-stabilized AuNCs (OVA@AuNCs) was found to be twice that of the reported BSA-stabilized AuNCs (BSA@AuNCs) under the same conditions. Moreover, the good pH stability and time stability of the OVA@AuNCs were examined. These properties will be helpful for AuNCs-based sensing and imaging. Further research revealed that the fluorescence of the OVA@AuNCs could be quenched by Hg2+ and it can be used as a sensor for sensitive Hg2+ detection with a detection limit of 10 nM.

Research progresses on the functional polypeptides in the detection and imaging of breast cancer

Breast cancer is a serious threat to the health of women all over the world. The precise diagnosis and treatment of breast cancer are of great importance to control the development of breast cancer as well as to improve survival rates of the patients. Nowadays, polypeptides are widely applied in breast cancer-related research, benefiting from lower immunogenicity, better biodegradability, higher penetration, and easier synthesis and modification. In this review, we have summarized recent applications of functional polypeptides in the detection and imaging of breast cancer, in which polypeptides work not only as a recognition element and signal source for detecting and imaging breast tumours, but also a building block and a therapeutic drug to assist image-guided treatment of breast cancer.

Catalytic hairpin assembly-programmed formation of clickable nucleic acids for electrochemical detection of liver cancer related short gene

DNA amplification usually takes place in an aqueous system to facilitate a highly efficient reaction. Therefore, it is a challenge to connect the DNA amplification with popular dry chemical methods, whose signal outputs usually come from a solid-liquid interface. Here, by linking catalytic hairpin assembly (CHA) with electrochemical biosensors through clickable nucleic acids, we develop a facile method for the detection of liver cancer related short gene MXR7. On one hand, the method maintains the advantages of CHA especially its high efficiency by performing the whole process of CHA in aqueous phase. On the other hand, the method realizes electrochemical detection of MXR7 by transferring a clickable double-helix production of MXR7-triggerd CHA to a dibenzocyclooctyne-functionalized electrode quickly through copper-free click chemistry. In comparison with traditional biotin-streptavidin or hybridization-assisted conjugation, the click chemistry allows quick response in a quarter of an hour, shortening the detection time greatly. In addition, owing to the lower steric hindrance as compared with streptavidin, the signal intensity is strong, making a sensitive detection possible. The detection limit reaches 125 fM, better than previous electrochemical methods. Results also reveal that CHA in solution has much better efficiency than that on interface, allowing two orders of magnitude improvement in detection limit (125 fM vs. 50 pM) with a shorter detection time (135 min vs. 165 min). This work also provides a novel concept to connect aqueous amplification system with interfacial detection method for other bio-analysis.