Reversible Fluorescent Probes for Biological Redox States

The redox chemistry of the cell is key to its function and health, and the development of chemical tools to study redox biology is important. While fluxes in oxidative state are essential for healthy cell function, a chronically elevated oxidative capacity is linked to disease. It is therefore essential that probes of biological redox states distinguish between these two conditions by the reversible sensing of changes over time. In this review, we discuss the current progress towards such probes, and identify key directions for future research in this nascent field of vital biological interest.     

Boronate Affinity–Molecularly Imprinted Biocompatible Probe: An Alternative for Specific Glucose Monitoring

A biocompatible probe for specific glucose recognition is based on photoinitiated boronate affinity–molecular imprinted polymers (BA‐MIPs). The unique pre‐self‐assembly between glucose and boronic acids creates glucose‐specific memory cavities in the BA‐MIPs coating. As a result, the binding constant toward glucose was enhanced by three orders of magnitude. The BA‐MIPs probe was applied to glucose determination in serum and urine and implanted into plant tissues for low‐destructive and long‐term in vivo continuous glucose monitoring.     

光敏异构化智能生物开关的进展

引出光敏异构化智能生物开关的概念。介绍了可逆光敏异构化生物物质的机制和特点, 并结合这个领域的研究和发展对其进行了较全面的讨论。探讨了可逆异构化开关物质在光记忆、电化学控制、生物传感器等方面的应用, 并对它的未来前景作出展望。     

Design optimization of highly sensitive LSPR enhanced surface plasmon resonance biosensors with nanoholes

For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters.     

Electrically Addressed Fabrication of Aptamer‐Based Array Electrodes

An aptamer immobilization method based electrically addressed fabrication has been developed for the preparation of aptamer‐modified arrayed electrodes, by which the human IgE aptamer was oriented and immobilized on the gold electrode surface. The optimization of the experimental conditions including the applied potential, time and scan rate of potential was investigated. The method was successfully used to immobilize the aptamer onto the desired electrodes, pixel by pixel, based on the electrically addressed approach. Compared to the control electrodes, the resulting aptamer‐modified electrodes showed their specific recognition for human IgE. The present method owns several advantages such as rapid and simple immobilization as well as its automatic addressed capability by the electric approach.     

Highly sensitive amplified electronic detection of DNA by biocatalyzed precipitation of an insoluble product onto electrodes

The amplified detection of a target DNA, based on the alkaline phosphatase oxidative hydrolysis of the soluble 5-bromo-4-chloro-3-indoyl phosphate to the insoluble indigo product as an amplification path, is addressed by two different sensing configurations. The accumulation of the insoluble product on Au electrodes or Au/quartz crystals alters the interfacial electron-transfer resistance at the Au electrode or the mass associated with the piezoelectric crystal, thus enabling the quantitative transduction of the DNA sensing by Faradaic impedance spectroscopy or microgravimetric quartz crystal microbalance measurements, respectively. One sensing configuration involves the association of a complex consisting of the target DNA and a biotinylated oligonucleotide to the functionalized transducers. The binding of the avidin/alkaline phosphatase conjugate to the sensing interface followed by the biocatalyzed precipitation provides the amplification path for the analysis of the target DNA. This analysis scheme was used to sense the target DNA with a sensitivity limit that corresponds to 5 x 10(-14) M. The second amplified detection scheme involves the use of a nucleic-acid-functionalized alkaline phosphatase as a biocatalytic conjugate for the precipitation of the insoluble product. Following this scheme, the functionalized transducers are interacted with the analyzed sample that was pretreated with the oligonucleotide-modified alkaline phosphatase, followed by the biocatalyzed precipitation as the amplification route for the analysis of the target DNA. By the use of this configuration, a detection limit corresponding to 5 x 10(-13) M was achieved. Real clinical samples of the Tay-Sachs genetic disorder were easily analyzed by the developed detection routes.     

Antigen-antibody binding kinetics for biosensor applications

The diffusion-limited binding kinetics of antigen (or antibody) in solution to antibody (or antigen) immobilized on a biosensor surface is analyzed within a fractal framework. The fit obtained by a dual-fractal analysis is compared with that obtained from a single-fractal analysis. In some cases, the dual-fractal analysis provides an improved fit when compared with a single-fractal analysis. This was indicated by the regression analysis provided by Sigmaplot (San Rafael, CA). These examples are presented. It is of interest to note that the state of disorder (or the fractal dimension) and the binding rate coefficient both increase (or decrease, a single example is presented for this case) as the reaction progresses on the biosensor surface. For example, for the binding of monoclonal antibody MAb 49 in solution to surface-immobilized antigen, a 90.4% increase in the fractal dimension (D_f1 toD _f2 ) from 1.327 to 2.527 leads to an increase in the binding rate coefficient (k₁ to k₂) by a factor of 9.4 from 11.74 to 110.3. The different examples analyzed and presented together provide a means by which the antigen-antibody reactions may be better controlled by noting the magnitude of the changes in the fractal dimension and in the binding rate coefficient as the reaction progresses on the biosensor surface.     

Analyte-receptor binding kinetics for different types of biosensors

A fractal analysis is presented for analyte-receptor binding kinetics for different types of biosensor applications. Data taken from the literature may be modeled using a single-fractal analysis, a single- and a dual-fractal analysis, or a dual-fractal analysis. The latter two methods represent a change in the binding mechanism as the reaction progresses on the surface. Predictive relationships developed for the binding rate coefficient as a function of the analyte concentration are of particular value since they provide a means by which the binding rate coefficients may be manipulated. Relationships are presented for the binding rate coefficients as a function of the fractal dimension D _f or the degree of heterogeneity that exists on the surface. When analyte-receptor binding is involved, an increase in the heterogeneity on the surface (increase in D _f ) leads to an increase in the binding rate coefficient. It is suggested that an increase in the degree of heterogeneity on the surface leads to an increase in the turbulence on the surface owing to the irregularities on the surface. This turbulence promotes mixing, minimizes diffusional limitations, and leads subsequently to an increase in the binding rate coefficient. The binding rate coefficient is rather sensitive to the degree of heterogeneity, D _f , that exists on the biosensor surface. For example, the order of dependence on D _f1 is 7.25 for the binding rate coefficient k ₁ for the binding of a Fab fragment of an antiparaquat monoclonal antibody in solution to an antigen in the form of a paraquat analog immobilized on a sensor surface. The predictive relationships presented for the binding rate coefficient and the fractal dimension as a function of the analyte concentration in solution provide further physical insights into the binding reactions on the surface, and should assist in enhancing biosensor performance. In general, the technique is applicable to other reactions occurring on different types of surfaces, such as cell-surface reactions.