Bioassay Devices Research Articles

Supramolecular Hydrogels for 3D Biosensors and Bioassays.

Supramolecular hydrogels play a pivotal role in many fields of biomedical research, including emerging applications in designing advanced tools for point-of-care testing, clinical diagnostics, and lab-on-chip analysis. This review outlines the growing relevance of supramolecular hydrogels in biosensing and bioassay devices, highlighting recent advancements that deliver increased sensitivity, real-time monitoring, and multiplexing capabilities through the distinctive properties of these nanomaterials. Furthermore, the exploration extends to additional applications, such as using hydrogels as three-dimensional matrices for cell-based assays.

High-performance self-powered photoelectrochemical bioassay system with a triphase oxidase enzymatic interface

In the field of biomolecule detection, self-powered photoelectrochemical (PEC) bioassay devices have gained considerable interest with no demand for an external voltage but rather solar energy consumption. In this study, we present a self-powered PEC bioassay system that consists of a nanoporous BiVO4 photoanode coupled to a biophotocathode with a solidliquidair triphase oxidase enzymatic interface. The triphase biophotocathode was assembled by immobilizing oxidase on superhydrophobic Cu2O@TiO2 nanowire arrays. A high and steady interfacial oxygen concentration can be ensured by the triphase biophotocathode with much increased gas mass transport capability, which consequently enhance the kinetics of the oxidase enzymatic reaction as well as the sensing performance of self-powered PEC bioassay system. For the diphase biophotocathode based system, the low solubility and slow diffusion rate of oxygen restrict the kinetics of the oxidase catalytic reaction. As a result, the proposed triphase self-powered PEC bioassay platform exhibits excellent performance with a linear range up to 20 mM for glucose (a model analyst) detection, which is 20 times higher than that of the diphase one. Furthermore, an exceptional anti-interface is obtained by the cathodic bioanalysis approach in the self-powered PEC bioassay system.

Versatile FeMoOv nanozyme bipolar electrode electrochemiluminescence biosensing and imaging platform for detection of H2O2 and PSA

In this work, a unique FeMoOv nanozyme-bipolar electrode (NM-BPE) electrochemiluminescence (ECL) biosensing and imaging platform was proposed for the first time to realize sensitive detection of target hydrogen peroxide (H2O2) and prostate specific antigen (PSA). Considering the advantage that the cathode and anode poles of the bipolar electrode (BPE) can be modified respectively, this work was carried out using anode equipped with ECL reagent bipyridine ruthenium (Ru(bpy)32+), and cathode equipped with the Fe-doped molybdenum oxide/Au nanoparticles (FeMoOv/AuNPs) with excellent peroxidase (POD) and catalase (CAT)-like activity. Because FeMoOv/AuNPs show efficient enzyme catalysis effect and can greatly promote the decomposition of H2O2, thus the electron transfer rate in the NM-BPE system would be much accelerated to enhance the ECL signal of Ru(bpy)32+. Based on this principle, this work not only realized sensitive detection of H2O2, but also ingeniously designed an sandwich immunosensor using FeMoOv/AuNPs as recognition probe to mediate the ECL response on the anode, achieving highly sensitive detection of PSA. Furthermore, a unique mobile phone ECL imaging system was developed for assay of PSA at different concentrations, which opened a new portable imaging sensing device for bioassays. This work was the first time to combine nanozymes with bipolar electrodes for ECL analysis and imaging, which not only broadened the applications of nanozymes, but also pioneered the new joint ECL research technique of bipolar electrode and ECL imaging in bioassays, showing great application prospect for multiple detection of proteins, nucleic acids and cancer cells.

A Portable Magnetic Particle Spectrometer for Future Rapid and Wash-Free Bioassays.

Nowadays, there is an increasing demand for more accessible routine diagnostics for patients with respect to high accuracy, ease of use, and low cost. However, the quantitative and high accuracy bioassays in large hospitals and laboratories usually require trained technicians and equipment that is both bulky and expensive. In addition, the multistep bioassays and long turnaround time could severely affect the disease surveillance and control especially in pandemics such as influenza and COVID-19. In view of this, a portable, quantitative bioassay device will be valuable in regions with scarce medical resources and help relieve burden on local healthcare systems. Herein, we introduce the MagiCoil diagnostic device, an inexpensive, portable, quantitative, and rapid bioassay platform based on the magnetic particle spectrometer (MPS) technique. MPS detects the dynamic magnetic responses of magnetic nanoparticles (MNPs) and uses the harmonics from oscillating MNPs as metrics for sensitive and quantitative bioassays. This device does not require trained technicians to operate and employs a fully automatic, one-step, and wash-free assay with a user friendly smartphone interface. Using a streptavidin-biotin binding system as a model, we show that the detection limit of the current portable device for streptavidin is 64 nM (equal to 5.12 pmole). In addition, this MPS technique is very versatile and allows for the detection of different diseases just by changing the surface modifications on MNPs. Although MPS-based bioassays show high sensitivities as reported in many literatures, at the current stage, this portable device faces insufficient sensitivity and needs further improvements. It is foreseen that this kind of portable device can transform the multistep, laboratory-based bioassays to one-step field testing in nonclinical settings such as schools, homes, offices, etc.

Inkjet Printing-Based Immobilization Method for a Single-Step and Homogeneous Competitive Immunoassay in Microchannel Arrays.

In this study, we report an inkjet printing-based method for the immobilization of different reactive analytical reagents on a single microchannel for a single-step and homogeneous solution-based competitive immunoassay. The immunoassay microdevice is composed of a poly(dimethylsiloxane) microchannel that is patterned using inkjet printing by two types of reactive reagents as dissolvable spots, namely, antibody-immobilized graphene oxide and a fluorescently labeled antigen. Since nanoliter-sized droplets of the reagents could be accurately and position-selectively spotted on the microchannel, different reactive reagents were simultaneously immobilized onto the same microchannel, which was difficult to achieve in previously reported capillary-based single-step bioassay devices. In the present study, the positions of the reagent spots and amount of reagent matrix were investigated to demonstrate the stable and reproducible immobilization and a uniform dissolution. Finally, a preliminary application to a single-step immunoassay of C-reactive protein was demonstrated as a proof of concept.

An Additive Manufacturing Approach that Enables the Field Deployment of Synthetic Biosensors

Abstract The tools of synthetic biology can be used to engineer living biosensors that report the presence of analytes. Although these engineered cellular biosensors have many potential applications for deployment outside of the lab, they are genetically modified organisms (GMOs) and are often considered dangerous. Mitigating the risk of releasing GMOs into the environment while enabling their use outside a laboratory is critical. Here, we describe the development of a biosensing system consisting of a synthetic biological circuit, which is engineered in Escherichia coli that are contained within a unique 3D-printed device housing. These GMOs detect the chemical quorum signal of Pseudomonas aeruginosa, an opportunistic pathogen. Using this device, the living biosensor makes contact with a specimen of interest without ever being exposed to the environment. Cells can be visually analyzed in the field within culture tubes, or returned to the lab for further analysis. Many biosensors lack the versatility required for deployment in the field, where many diseases can go undiagnosed due to a lack of resources and equipment. Our bioassay device utilizes 3D printing to create a portable, modular, and inexpensive device for the field deployment of living biosensors.

3D Multilayered paper- and thread/paper-based microfluidic devices for bioassays.

In this paper we describe the fabrication of novel 3D microfluidic paper-based analytical devices (3D-μPADs) and a 3D microfluidic thread/paper-based analytical device (3D-μTPAD) to detect glucose and BSA through colorimetric assays. The 3D-μPAD and 3D-μTPAD consisted of three (wax, heat pressed wax-printed paper, single-sided tape) and four (hole-punched single-sided tape, blank chromatography circles, heat-pressed wax-printed paper, hole-punched single-sided tape containing trifurcated thread) layers, respectively. The saturation curves for each assay were generated for all platforms. For the glucose assay, a solution of glucose oxidase (GOx), horseradish peroxidase, and potassium iodide was flowed through each platform and, upon contact with glucose, generated a yellow-brown color indicative of the oxidation of iodide to iodine. For the protein assay, BSA was flowed through each device and, upon contact with citrate buffer and tetrabromophenol blue, resulted in a color change from yellow to blue. The devices were dried, scanned, and analyzed yielding a correlation between either yellow intensity and glucose concentration or cyan intensity and BSA concentration. A similar glucose assay, using unknown concentrations of glucose in artificial urine, was conducted and, when compared to the saturation curve, showed good correlation between the theoretical and actual concentrations (percent differences <10%). The development of 3D-μPADs and 3D-μTPADs can further facilitate the use of these platforms for colorimetric bioassays.

New paper-based microfluidic tools for the analysis of blood serum protein and creatinine builtviaaerosolized deposition of polycaprolactone

Aerosolized deposition of a polymer solution to a substrate allows for rapid, low-cost fabrication of 3D microfluidic devices for bioassays.

Pt-Decorated Magnetic Nanozymes for Facile and Sensitive Point-of-Care Bioassay.

Development of facile and sensitive bioassays is important for many point-of-care applications. In this study, we fulfilled such demand by synthesizing Pt-decorated magnetic nanozymes and developing a bioassay based on unique properties of the newly synthesized nanozymes. Fe3O4-Pt/core-shell nanoparticles (MPt/CS NPs) with various compositions were synthesized and characterized. Fe3O4 NP itself is a good nanozyme with catalytic activity superior to that of natural enzymes, but catalytic activity can be further improved by incorporating Pt to the outer layers of the Fe3O4 NPs and building heterogeneous nanostructures. Magnetic properties of MPt/CS NPs enable magnetic enrichment of liquid samples, whereas catalytic properties of MPt/CS NPs allow signal amplification by enzyme-like reactions. By integrating MPt/CS NPs in lateral flow immunoassay strips, one of the widely used point-of-care bioassay devices, and harnessing magnetic and enzyme-like properties of MPt/CS NPs, an increase in sensitivity of two orders of magnitude was achieved compared to the sensitivity of conventional lateral flow immunoassay based on Au nanoparticles.

Fabrication of optomicrofluidics for real-time bioassays based on hollow sphere colloidal photonic crystals with wettability patterns

An optomicrofluidic device for real-time bioassays was constructed by introducing 3D superhydrophilic channels into superhydrophobic hollow SiO2 colloidal photonic crystals.

Creating compact and microscale features in paper-based devices by laser cutting.

In this work we describe a fabrication method to create compact and microscale features in paper-based microfluidic devices using a CO2 laser cutting/engraving machine. Using this method we are able to produce the smallest features with the narrowest barriers yet reported for paper-based microfluidic devices. The method uses foil backed paper as the base material and yields inexpensive paper-based devices capable of using small fluid sample volumes and thus small reagent volumes, which is also suitable for mass production. The laser parameters (power and laser head speed) were adjusted to minimize the width of hydrophobic barriers and we were able to create barriers with a width of 39 ± 15 μm that were capable of preventing cross-barrier bleeding. We generated channels with a width of 128 ± 30 μm, which we found to be the physical limit for small features in the chromatography paper we used. We demonstrate how miniaturizing of paper-based microfluidic devices enables eight tests on a single bioassay device using only 2 μL of sample fluid volume.

Paper-based 3D microfluidic device for multiple bioassays

This study investigates a new paper-based 3D microfluidic analytical device for analyzing multiple biological fluids. A wax-printed and -impregnated device was operated using tip-pinch manipulation of the thumb and index fingers and applied the chemical reaction of a preloaded colorimetric indicator and biological solutions. Chemical sensing of protein and glucose concentrations was quantitatively analyzed by changes in the color intensity of the image taken from three image readout devices including scanner (Epson Perfection V700), microscope (USB-embedded handheld digital microscope), and smartphone (LG Optimus Vu). Paper-based 3D microfluidic analytic device with three image analyzers successfully quantified 1.5–75μM protein concentrations and 0–900mg/dL glucose concentrations. Paper-based 3D microfluidic device combined with the smartphone showed the performance in protein bioassay (1.5–75μM) and glucose bioassay (0–50mM) including clinically relevant ranges comparable to other devices. An origami-driven paper-based 3D microfluidic analytic is a useful platform with great potential for application in point-of-care diagnostics.

Simple and Sensitive Point-of-Care Bioassay System Based on Hierarchically Structured Enzyme-Mimetic Nanoparticles.

An enzyme-mimetic nanoparticle-based point of care bioassay device is developed for rapid and sensitive detection of analytes. Digital images acquired by smart cellular phones allow quantifying the amounts of analytes. Using this new device, quantitative analysis of liquid sample is performed within 15 min with an order of magnitude enhancement of sensitivity compared with conventional Au nanoparticle-based devices.

Low-cost photolithographic fabrication of nanowires and microfilters for advanced bioassay devices.

Integrated microfluidic devices with nanosized array electrodes and microfiltration capabilities can greatly increase sensitivity and enhance automation in immunoassay devices. In this contribution, we utilize the edge-patterning method of thin aluminum (Al) films in order to form nano- to micron-sized gaps. Evaporation of high work-function metals (i.e., Au, Ag, etc.) on these gaps, followed by Al lift-off, enables the formation of electrical uniform nanowires from low-cost, plastic-based, photomasks. By replacing Al with chromium (Cr), the formation of high resolution, custom-made photomasks that are ideal for low-cost fabrication of a plurality of array devices were realized. To demonstrate the feasibility of such Cr photomasks, SU-8 micro-pillar masters were formed and replicated into PDMS to produce micron-sized filters with 3–4 µm gaps and an aspect ratio of 3. These microfilters were capable of retaining 6 µm beads within a localized site, while allowing solvent flow. The combination of nanowire arrays and micro-pillar filtration opens new perspectives for rapid R&D screening of various microfluidic-based immunoassay geometries, where analyte pre-concentration and highly sensitive, electrochemical detection can be readily co-localized.

Femtosecond laser fabrication of monolithically integrated microfluidic sensors in glass.

Femtosecond lasers have revolutionized the processing of materials, since their ultrashort pulse width and extremely high peak intensity allows high-quality micro- and nanofabrication of three-dimensional (3D) structures. This unique capability opens up a new route for fabrication of microfluidic sensors for biochemical applications. The present paper presents a comprehensive review of recent advancements in femtosecond laser processing of glass for a variety of microfluidic sensor applications. These include 3D integration of micro-/nanofluidic, optofluidic, electrofluidic, surface-enhanced Raman-scattering devices, in addition to fabrication of devices for microfluidic bioassays and lab-on-fiber sensors. This paper describes the unique characteristics of femtosecond laser processing and the basic concepts involved in femtosecond laser direct writing. Advanced spatiotemporal beam shaping methods are also discussed. Typical examples of microfluidic sensors fabricated using femtosecond lasers are then highlighted, and their applications in chemical and biological sensing are described. Finally, a summary of the technology is given and the outlook for further developments in this field is considered.

Fabrication of a gel particle array in a microfluidic device for bioassays of protein and glucose in human urine samples

This paper describes a simple method for fabricating a series of poly(ethylene glycol) diacrylate (PEG-DA) hydrogel microstructures inside microfluidic channels as probe for proteins and glucose. In order to demonstrate the feasibility of this newly developed system, bovine serum albumin (BSA) was chosen as a model protein. PEG microcolumns were used for the parallel detection of multiple components. Using tetrabromophenol blue (TBPB) and the horseradish peroxidase/glucose oxidase reaction system, bovine serum albumin (BSA) and glucose in human urine were detected by color changes. The color changes for BSA within a concentration range of 1-150 μM, and glucose within a range of 50 mM-2 M could be directly distinguished by eyes or precisely identified by optical microscope. To show the practicability of the gel particle array, protein and glucose concentrations of real human urine samples were determined, resulting in a good correlation with hospital analysis. Notably, only a 5 µL sample was needed for a parallel measurement of both analytes. Conveniently, no special readout equipment or power source was required during the diagnosis process, which is promising for an application in rapid point-of-care diagnosis.

D-2-1 ナノインプリントリソグラフィとUVリソグラフィの融合によるバイオアッセイ用サブマイクロ灌流デバイスの作製(D-2 設計・プロセス,口頭発表:マイクロナノメカトロニクス)

D-2-1 ナノインプリントリソグラフィとUVリソグラフィの融合によるバイオアッセイ用サブマイクロ灌流デバイスの作製(D-2 設計・プロセス,口頭発表:マイクロナノメカトロニクス)

Total internal reflection ellipsometry as a label-free assessment method for optimization of the reactive surface of bioassay devices based on a functionalized cycloolefin polymer

We report a label-free optical detection technique, called total internal reflection ellipsometry (TIRE), which can be applied to study the interactions between biomolecules and a functionalized polymer surface. Zeonor (ZR), a cycloolefin polymer with low autofluorescence, high optical transmittance and excellent chemical resistance, is a highly suitable material for optical biosensor platforms owing to the ease of fabrication. It can also be modified with a range of reactive chemical groups for surface functionalization. We demonstrate the applications of TIRE in monitoring DNA hybridization assays and human chorionic gonadotrophin sandwich immunoassays on the ZR surface functionalized with carboxyl groups. The Ψ and Δ spectra obtained after the binding of each layer of analyte have been fitted to a four-layer ellipsometric model to quantitatively determine the amount of analytes bound specifically to the functionalized ZR surface. Our proposed TIRE technique with its very low analyte consumption and its microfluidic array format could be a useful tool for evaluating several crucial parameters in immunoassays, DNA interactions, adsorption of biomolecules to solid surfaces, or assessment of the reactivity of a functionalized polymer surface towards a specific analyte.

Toner and paper‐based fabrication techniques for microfluidic applications

The interest in low-cost microfluidic platforms as well as emerging microfabrication techniques has increased considerably over the last years. Toner- and paper-based techniques have appeared as two of the most promising platforms for the production of disposable devices for on-chip applications. This review focuses on recent advances in the fabrication techniques and in the analytical/bioanalytical applications of toner and paper-based devices. The discussion is divided in two parts dealing with (i) toner and (ii) paper devices. Examples of miniaturized devices fabricated by using direct-printing or toner transfer masking in polyester-toner, glass, PDMS as well as conductive platforms as recordable compact disks and printed circuit board are presented. The construction and the use of paper-based devices for off-site diagnosis and bioassays are also described to cover this emerging platform for low-cost diagnostics.

Liquid dielectrophoresis and surface microfluidics

Liquid dielectrophoresis (L-DEP), when deployed at microscopic scales on top of hydrophobic surfaces, offers novel ways of rapid and automated manipulation of very small amounts of polar aqueous samples for microfluidic applications and development of laboratory-on-a-chip devices. In this article we highlight some of the more recent developments and applications of L-DEP in handling and processing of various types of aqueous samples and reagents of biological relevance including emulsions using such microchip based surface microfluidic (SMF) devices. We highlighted the utility of these devices for on-chip bioassays including nucleic acid analysis. Furthermore, the parallel sample processing capabilities of these SMF devices together with suitable on- or off-chip detection capabilities suggest numerous applications and utility in conducting automated multiplexed assays, a capability much sought after in the high throughput diagnostic and screening assays.