Biodetection Devices Research Articles

Polystyrene microsphere monolayer assembled on glass slide for label-free OIRD immunoassay with enhanced sensitivity

Oblique-incidence reflectivity difference (OIRD) is a newly established method to monitor various surface processes and shows great prospect for real-time and label-free immunoassay, yet its sensitivity needs essential improvement to meet the requirement of practical applications. In this work, a label-free OIRD immunoassay biochip was developed with improved sensitivity by using standard glass slide coated with polystyrene (PS) microsphere monolayer as the substrate. The immunoassay sensitivity of this biochip was found to be greatly improved compared with the conventional biochip built on glass slide. Further on-chip ELISA and optical calculation suggests that the improvement is not only associated with high capture efficiency of this biochip towards its target, but is also benefited from the porous PS monolayer enhanced intrinsic OIRD sensitivity via optical interference enhancement and effective dielectric constant effect. This work may provide valuable insight into the development of high performance label-free OIRD bio-detection devices.

Plasmonic nanoassemblies for surface-enhanced Raman scattering-based biodetection and biomedical theranostics

Plasmonic nanoassemblies are well-defined organizing of elementary metallic nanocrystal building blocks into ordered architectures across multiple scales, which constituents an exciting route to engineer nanomaterials structures with novel properties. Such nanoassemblies can accurately enhance, guide, and switch electromagnetic field at the nanoscale, which is shaping new-generation technologies with a plethora of applications, such as ultrasensitive bimolecular sensors, cancer diagnostics, and photothermal therapy (PTT), to name a few. In this review, we mainly focus on the plasmonic nanoassemblies, including the structure design, property control, and biomedical applications. The guiding principles have been first clarified with design rules being suggested. Then, the methodologies for fabrication of surface-enhanced Raman scattering-based (SERS-based) biodetection devices have been discussed. Finally, we summarized the PTT by using the plasmonic nanoassemblies as bioprobes for theranostics. Based on the facile yet efficient fabrication methods, high-efficient optoelectronic properties, and high performance in biomedical applications, we firmly believe that the plasmonic nanoassemblies can be integrated with portable devices for next-generation biosensors and biomedical theranostics.

Microdisk resonators as high-sensitive devices for biodetection

The single mode lasing of microdisks (MDs) with attached antibodies in aqueous medium is demonstrated. MDs comprise quantum dot active region emitting in the vicinity of 1.3 μm. The presence of antibodies on a MD surface leads to a number of effects, including the increase of threshold power of laser generation, likewise, changes in the linewidth of the resonance peak.

Precise Control of Interfacial Charge Transport for Building Functional Optoelectronic Devices

AbstractOptoelectronic devices and interfaces therein have captured great attention in both scientific and industrial communities because of the wide variety of their unique properties. From a materials chemistry point of view, each layer and individual component of an optoelectronic device possesses the possibility of flexible chemical modification, making it feasible to dope, mix, and physically/chemically modify the interface. Exploiting the novel properties in optoelectronic devices with diverse layerings of metals, semiconductors, and insulators, along with the interfaces between them, leads to new electronic device designs, including functional transistors, biodetection devices, and flexible electronics, as well as other types of traditional optoelectronic devices, such as photodetectors, photovoltaic devices, and light‐emitting devices, with unprecedented characteristics or unique functionalities. This article reviews the recent developments and challenges and provides a perspective on the exploration of interface‐engineered organic optoelectronic devices for future applications in electronics and optoelectronics.

Photofocusing of microorganisms swimming in a flow with shear

Some swimming microorganisms are sensitive to light, and this can affect the way in which they negotiate their environment. In particular, photophobic cells are repelled from unfavourable light conditions, and in a quiescent fluid environment this can be observed as elevated cell levels in regions away from these light conditions. This photoresponsive effect is of interest due to its potential technological applications. For example, the use of light to focus and direct cells could be used as a convenient means to separate out the algae used in biofuel production (for example, hydrogen), or exploited within devices for biodetection of environmental contaminants. However, in these types of situations the swimming cells will usually be suspended in a flow with shear. In this environment, it has previously been shown that cells can become hydrodynamically trapped in regions of high fluid shear, and so the extent to which photofocusing can occur under these conditions is not immediately clear. Moreover, in applications where the light must pass through appreciable volumes of the suspension, cells will typically absorb light and so shade each other from the illumination. As such, the intensity at any point in the flow is dependent upon the global cell concentration. Hence, in this study we model the coupled influence of fluid shear and cell photosensitivity on a suspension of swimming microorganisms, and ask under what circumstances a suspension of photophobic cells might be focused into high concentration regions. doi:10.1017/S1446181118000123

PHOTOFOCUSING OF MICROORGANISMS SWIMMING IN A FLOW WITH SHEAR

Some swimming microorganisms are sensitive to light, and this can affect the way in which they negotiate their environment. In particular, photophobic cells are repelled from unfavourable light conditions, and in a quiescent fluid environment this can be observed as elevated cell levels in regions away from these light conditions. This photoresponsive effect is of interest due to its potential technological applications. For example, the use of light to focus and direct cells could be used as a convenient means to separate out the algae used in biofuel production (for example, hydrogen), or exploited within devices for biodetection of environmental contaminants. However, in these types of situations the swimming cells will usually be suspended in a flow with shear. In this environment, it has previously been shown that cells can become hydrodynamically trapped in regions of high fluid shear, and so the extent to which photofocusing can occur under these conditions is not immediately clear. Moreover, in applications where the light must pass through appreciable volumes of the suspension, cells will typically absorb light and so shade each other from the illumination. As such, the intensity at any point in the flow is dependent upon the global cell concentration. Hence, in this study we model the coupled influence of fluid shear and cell photosensitivity on a suspension of swimming microorganisms, and ask under what circumstances a suspension of photophobic cells might be focused into high concentration regions.

Characterization and bio-binding ability study on size-controllable highly monodisperse magnetic nanoparticles

With the advances in micro-/nano-electronic technology, the development of portable lab-on-chip biodetection device by utilizing magnetic nanoparticles as bio-probes and magnetic field sensor as signal detector has attracted considerable interests in healthcare area. Magnetic probes with required sizes are crucial in quantitative magnetic bio-detection for specific bio-analytes. The objective of this study was to synthesize and characterize amphiphilic co-polymer coated magnetic iron oxide nanoparticles with tunable sizes and study their bio-binding ability. Transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared spectrometer (FT-IR), thermogravimetric analyzer (TGA), and vibrating sample magnetometer (VSM) were employed to investigate the particle dimension, hydrodynamic size, surface property, mass ratio of surface surfactants, and magnetic behavior. The investigation on their biologically binding ability with bovine serum protein was carried out on thin gold film. The results showed iron oxide nanoparticles with controllable sizes were coated by amphiphilic co-polymer successfully and could be completely transferred and well-dispersed in aqueous solutions. The final products with magnetic core sizes ranging from 6nm to 17nm showed superparamagnetic behavior, stable hydrodynamic sizes in aqueous suspensions, and binding ability with bio-molecules, making them promising candidates as magnetic tags for the development of bio-detection devices.

Microcantilever based on flavoenzyme monoamine oxidase (MAO) as a bioprobe

Microcantilevers (MCLs) are cost-effective and highly sensitive devices for biodetection. Adsorption of specific analytes on the microcantilever surface causes the bending of MCL through changing of the surface characteristics. These new bioprobes designed in a way that one side of the microcantilever surface is coated with a selective receptor that absorbs particular molecules. After surface absorption of target, the microcantilever deflects under nano – Newton forces and results in microcantilever bending. In the following work, we have proposed a modifed microcantilever through immobilization of monoamine oxidase (MAO) as a Flavin–Adenosine-Dinucleotide (FAD)-containing enzyme. This enzyme catalyzes the oxidative deamination of amine groups, so interaction between compounds with amine functional group and enzyme is based on biodetection with monoamine oxidase modified microcantilever. In the present study, MAO was immobilized on the microcantilever surface through a cross linker to a monolayer on the gold surface. Following, the Kynuramine solution was used as substrate. The comparative results showed that the enzyme is activated in immobilized state in order to oxidize amine groups and is inhibited in the presence of Methamphethamine as an enzyme inhibitor. Since all processes are performing at room temperature, therefore the design of bioprobe based on modified microcantilever would be highly significant for biodetection.

Optical and dielectric sensors based on antimicrobial peptides for microorganism diagnosis.

Antimicrobial peptides (AMPs) are natural compounds isolated from a wide variety of organisms that include microorganisms, insects, amphibians, plants, and humans. These biomolecules are considered as part of the innate immune system and are known as natural antibiotics, presenting a broad spectrum of activities against bacteria, fungi, and/or viruses. Technological innovations have enabled AMPs to be utilized for the development of novel biodetection devices. Advances in nanotechnology, such as the synthesis of nanocomposites, nanoparticles, and nanotubes have permitted the development of nanostructured platforms with biocompatibility and greater surface areas for the immobilization of biocomponents, arising as additional tools for obtaining more efficient biosensors. Diverse AMPs have been used as biological recognition elements for obtaining biosensors with more specificity and lower detection limits, whose analytical response can be evaluated through electrochemical impedance and fluorescence spectroscopies. AMP-based biosensors have shown potential for applications such as supplementary tools for conventional diagnosis methods of microorganisms. In this review, conventional methods for microorganism diagnosis as well new strategies using AMPs for the development of impedimetric and fluorescent biosensors are highlighted. AMP-based biosensors show promise as methods for diagnosing infections and bacterial contaminations as well as applications in quality control for clinical analyses and microbiological laboratories.

Application perspectives of localization microscopy in virology

Localization microscopy approaches allowing an optical resolution down to the single-molecule level in fluorescence-labeled biostructures have already found a variety of applications in cell biology, as well as in virology. Here, we focus on some perspectives of a special localization microscopy embodiment, spectral precision distance/position determination microscopy (SPDM). SPDM permits the use of conventional fluorophores or fluorescent proteins together with standard sample preparation conditions employing an aqueous buffered milieu and typically monochromatic excitation. This allowed superresolution imaging and studies on the aggregation state of modified tobacco mosaic virus particles on the nanoscale with a single-molecule localization accuracy of better than 8 nm, using standard fluorescent dyes in the visible spectrum. To gain a better understanding of cell entry mechanisms during influenza A virus infection, SPDM was used in conjunction with algorithms for distance and cluster analyses to study changes in the distribution of virus particles themselves or in the distribution of infection-related proteins, the hepatocyte growth factor receptors, in the cell membrane on the single-molecule level. Not requiring TIRF (total internal reflection) illumination, SPDM was also applied to study the molecular arrangement of gp36.5/m164 glycoprotein (essentially associated with murine cytomegalovirus infection) in the endoplasmic reticulum and the nuclear membrane inside cells with single-molecule resolution. On the basis of the experimental evidence so far obtained, we finally discuss additional application perspectives of localization microscopy approaches for the fast detection and identification of viruses by multi-color SPDM and combinatorial oligonucleotide fluorescence in situ hybridization, as well as SPDM techniques for optimization of virus-based nanotools and biodetection devices.

Unique temporal and spatial biomolecular emission profile on individual zinc oxide nanorods

Zinc oxide nanorods (ZnO NRs) have emerged in recent years as extremely useful, optical signal-enhancing platforms in DNA and protein detection. Although the use of ZnO NRs in biodetection has been demonstrated so far in systems involving many ZnO NRs per detection element, their future applications will likely take place in a miniaturized setting while exploiting single ZnO NRs in a low-volume, high-throughput bioanalysis. In this paper, we investigate temporal and spatial characteristics of the biomolecular fluorescence on individual ZnO NR systems. Quantitative and qualitative examinations of the biomolecular intensity and photostability are carried out as a function of two important criteria, the time and position along the long axis (length) of NRs. Photostability profiles are also measured with respect to the position on NRs and compared to those characteristics of biomolecules on polymeric control platforms. Unlike the uniformly distributed signal observed on the control platforms, both the fluorescence intensity and photostability are position-dependent on individual ZnO NRs. We have identified a unique phenomenon of highly localized, fluorescence intensification on the nanorod ends (FINE) of well-characterized, individual ZnO nanostructures. When compared to the polymeric controls, the biomolecular fluorescence intensity and photostability are determined to be higher on individual ZnO NRs regardless of the position on NRs. We have also carried out finite-difference time-domain simulations the results of which are in good agreement with the observed FINE. The outcomes of our investigation will offer a much needed basis for signal interpretation for biodetection devices and platforms consisting of single ZnO NRs and, at the same time, contribute significantly to provide insight in understanding the biomolecular fluorescence observed from ZnO NR ensemble-based systems.

Ultraviolet surface plasmon polariton propagation for ZnO semiconductor-insulator-metal waveguides

Ultraviolet surface plasmon polariton propagation for ZnO semiconductor-insulator-metal waveguide is investigated by means of the finite-element method. The field distribution, effective refractivity, propagation distance, and mode area of the hybrid mode supported by the waveguides were detailed analyzed, which are dependent on the dielectric constant and geometrical parameters. In order to achieve low propagation loss and subwavelength field confinement, several materials are calculated. Our investigation indicated that air and aluminum are better, which act as the insulator and metal respectively, and the effective mode area of such a waveguide can be as small as λ2/100. The results can help the development of nano-sized light sources which can enhance the sensitivity for bio-detection devices and diagnostic equipments.

Direct patterning of probe proteins on an antifouling PLL-g-dextran coating for reducing the background signal of fluorescent immunoassays

The limit of detection of advanced immunoassays, biochips and micro/nano biodetection devices is impacted by the non-specific adsorption of target molecules at the sample surface. In this paper, we present a simple and versatile low cost method for generating active surfaces composed of antibodies arrays surrounded by an efficient anti-fouling layer, capable to decrease drastically the fluorescence background signal obtained after interaction with a solution to be analyzed. The technological process involves the direct micro-contact printing of the antibodies probe molecules on a pre-coated PLL-g-dextran thin layer obtained by contact printing using a flat PDMS stamp. Compared to other blocking strategies (ethanolamine blocking treatment, PLL-g-PEG incubation, PLL-g-dextran incubation, printing on a plasma-deposited PEO layer), our surface chemistry method is more efficient for reducing non-specific interactions responsible for a degraded signal/noise ratio.

Speciation of l-DOPA on Nanorutile as a Function of pH and Surface Coverage Using Surface-Enhanced Raman Spectroscopy (SERS)

The adsorption configuration of organic molecules on mineral surfaces is of great interest because it can provide fundamental information for both engineered and natural systems. Here we have conducted surface-enhanced Raman spectroscopy (SERS) measurements to probe the attachment configurations of DOPA on nanorutile particles under different pH and surface coverage conditions. The Raman signal enhancement arises when a charge transfer (CT) complex forms between the nanoparticles and adsorbed DOPA. This Raman signal is exclusively from the surface-bound complexes with great sensitivity to the binding and orientation of the DOPA attached to the TiO(2) surface. Our SERS spectra show peaks that progressively change with pH and surface coverage, indicating changing surface speciation. At low pH and surface coverage, DOPA adsorbs on the surface lying down, with probably three points of attachment, whereas at higher pH and surface coverage DOPA stands up on the surface as a species involving two attachment points via the two phenolic oxygens. Our results demonstrate experimentally the varying proportions of the two surface species as a function of environmental conditions consistent with published surface complexation modeling. This observation opens up the possibility to manipulate organic molecule attachment in engineered systems such as biodetection devices. Furthermore, it provides a perspective on the possible role of mineral surfaces in the chemical evolution of biomolecules on the early Earth. Adsorbed biomolecules on mineral surface in certain configurations may have had an advantage for subsequent condensation reactions, facilitating the formation of peptides.

Giant magnetoimpedance for biosensing: Advantages and shortcomings

Biosensors are an important area of modern sensor applications. Magnetoimpedance (MI) phenomenon was proposed for biosensing in 2003. Since that MI biosensor prototypes based on amorphous ribbons, multilayered structures, amorphous rapidly quenched wires and glass covered microwires were designed and tested. In this paper the advantages and shortcomings of MI-based devices for magnetic labels or label-free biodetection are discussed in view of recent results.

Nanoelectrode-based devices for electrical biodetection in liquid solution

The fabrication of nanosystems for the electrical detection of biomolecular interactions is reported. Using a planar process on silicon involving high-resolution electron beam lithography and lift-off, we have demonstrated the reliable fabrication of nanoelectrode-based devices with controlled gap dimensions ranging from 100 nm down to 20 nm. These devices were used to achieve the electrical detection of gold colloids. We show that binding events can occur in inter-electrode gaps, leading to a drastic modification of the electrical transport through the nanojunction. Using a similar approach, electrical measurements in solution were performed by developing Poly(dimetylsiloxane) molded microtanks. First experiments involving gold colloids in solution have shown the possibility of detecting individual nanoparticles. The versatility and the very high sensitivity of these devices added to the simplicity of implementation make this approach very attractive for the fabrication of efficient nanobiosensors.

Nanoelectrode-based devices for electrical biodetection in liquid solution

The fabrication of nanosystems for the electrical detection of biomolecular interactions is reported. Using a planar process on silicon involving high-resolution electron beam lithography and lift-off, we have demonstrated the reliable fabrication of nanoelectrode-based devices with controlled gap dimensions ranging from 100 nm down to 20 nm. These devices were used to achieve the electrical detection of gold colloids. We show that binding events can occur in inter-electrode gaps, leading to a drastic modification of the electrical transport through the nanojunction. Using a similar approach, electrical measurements in solution were performed by developing Poly(dimetylsiloxane) molded microtanks. First experiments involving gold colloids in solution have shown the possibility of detecting individual nanoparticles. The versatility and the very high sensitivity of these devices added to the simplicity of implementation make this approach very attractive for the fabrication of efficient nanobiosensors.