Recent advancements in chemical luminescence-based lab-on-chip and microfluidic platforms for bioanalysis

Improving "lab-on-a-chip" techniques using biomedical nanotechnology: a review

Nanotechnology and its applications in biomedical sciences principally in molecular nanodiagnostics are known as nanomolecular diagnostics, which provides new options for clinical nanodiagnostic techniques. Molecular nanodiagnostics are a critical role in the development of personalized medicine, which features point-of care performance of diagnostic procedure. This can to check patients at point-of-care facilities or in remote or resource-poor locations, therefore reducing checking time from days to minutes. In this review, applications of nanotechnology suited to biomedicine are discussed in two main class: biomedical applications for use inside (such as drugs, diagnostic techniques, prostheses, and implants) and outside the body (such as "lab-on-a-chip" techniques). A lab-on-a-chip (LOC) is a tool that incorporates numerous laboratory tasks onto a small device, usually only millimeters or centimeters in size. Finally, are discussed the applications of biomedical nanotechnology in improving "lab-on-a-chip" techniques.

Depth position detection for fast moving objects in sealed microchannel utilizing chromatic aberration

This research reports a novel method for depth position measurement of fast moving objects inside a microfluidic channel based on the chromatic aberration effect. Two band pass filters and two avalanche photodiodes (APD) are used for rapid detecting the scattered light from the passing objected. Chromatic aberration results in the lights of different wavelengths focus at different depth positions in a microchannel. The intensity ratio of two selected bands of 430 nm-470 nm (blue band) and 630 nm-670 nm (red band) scattered from the passing object becomes a significant index for the depth information of the passing object. Results show that microspheres with the size of 20 μm and 2 μm can be resolved while using PMMA (Abbe number, V = 52) and BK7 (V = 64) as the chromatic aberration lens, respectively. The throughput of the developed system is greatly enhanced by the high sensitive APDs as the optical detectors. Human erythrocytes are also successfully detected without fluorescence labeling at a high flow velocity of 2.8 mm/s. With this approach, quantitative measurement for the depth position of rapid moving objects inside a sealed microfluidic channel can be achieved in a simple and low cost way.

A microfluidic multiplex proteomic immunoassay device for translational research

Objective

Microfluidic technology has the potential to miniaturize and automate complex laboratory procedures. The objective of this study was to assess a microfluidic immunoassay device, Simple Plex, which simultaneously measured IL-1β, TNF-α, IL-6, and IL-10 in serum samples. This assessment is important to understanding the potentials of this microfluidic device as a valuable tool in translational research efforts.

Methods

We studied the operational characteristics of Simple Plex, and compared to other immunoassay systems including bead-based (i.e., Bio-Plex^® from Bio-Rad) and planar micro-spot based (i.e., Multi-Array from Meso Scale Discovery) multiplex assays. We determined imprecisions for each of the Simple Plex assays and evaluated the ability of Simple Plex to detect IL-1β, TNF-α, IL-6, and IL-10 in serum samples.

Results

Simple Plex assays required 25 µL serum, and 1.5 h to run 16 samples per cartridge per instrument. Assay imprecisions, evaluated by measurement of 6 replicates in duplicate from a serum pool using three different cartridges, were less than 10 % for all 4 cytokine protein biomarkers, comparable to the imprecisions of traditional ELISAs. The Simple Plex assays were able to detect 32, 95, 97, and 100 % [i.e., percentages of the results within the respective analytical measurement ranges (AMRs)] of IL-1β, TNF-α, IL-6, and IL-10, respectively, in 66 serum samples.

Conclusions

Simple Plex is a microfluidic multiplex immunoassay device that offers miniaturized, and automated analysis of protein biomarkers. Microfluidic devices such as Simple Plex represent a promising platform to be used in translational research to measure protein biomarkers in real clinical samples.

Electrochemiluminescence on digital microfluidics for microRNA analysis

Electrochemiluminescence (ECL) is a sensitive analytical technique with great promise for biological applications, especially when combined with microfluidics. Here, we report the first integration of ECL with digital microfluidics (DMF). ECL detectors were fabricated into the ITO-coated top plates of DMF devices, allowing for the generation of light from electrically excited luminophores in sample droplets. The new system was characterized by making electrochemical and ECL measurements of soluble mixtures of tris(phenanthroline)ruthenium(II) and tripropylamine (TPA) solutions. The system was then validated by application to an oligonucleotide hybridization assay, using magnetic particles bearing 21-mer, deoxyribose analogues of the complement to microRNA-143 (miRNA-143). The system detects single nucleotide mismatches with high specificity, and has a limit of detection of 1.5 femtomoles. The system is capable of detecting miRNA-143 in cancer cell lysates, allowing for the discrimination between the MCF-7 (less aggressive) and MDA-MB-231 (more aggressive) cell lines. We propose that DMF-ECL represents a valuable new tool in the microfluidics toolbox for a wide variety of applications.

Label-free bead-based metallothionein electrochemical immunosensor

A novel microfluidic label-free bead-based metallothionein immunosensors was designed. To the surface of superparamagnetic agarose beads coated with protein A, polyclonal chicken IgY specifically recognizing metallothionein (MT) were immobilized via rabbit IgG. The Brdicka reaction was used for metallothionein detection in a microfluidic printed 3D chip. The assembled chip consisted of a single copper wire coated with a thin layer of amalgam as working electrode. Optimization of MT detection using designed microfluidic chip was performed in stationary system as well as in the flow arrangement at various flow rates (0-1800 μL/min). In stationary arrangement it is possible to detect MT concentrations up to 30 ng/mL level, flow arrangement allows reliable detection of even lower concentration (12.5 ng/mL). The assembled miniature flow chip was subsequently tested for the detection of MT elevated levels (at approx. level 100 μg/mL) in samples of patients with cancer. The stability of constructed device for metallothionein detection in flow arrangement was found to be several days without any maintenance needed.

An integrated closed-tube 2-plex PCR amplification and hybridization assay with switchable lanthanide luminescence based spatial detection

Switchable lanthanide luminescence is a binary probe technology that inherently enables a high signal modulation in separation-free detection of DNA targets. A luminescent lanthanide complex is formed only when the two probes hybridize adjacently to their target DNA. We have now further adapted this technology for the first time in the integration of a 2-plex polymerase chain reaction (PCR) amplification and hybridization-based solid-phase detection of the amplification products of the Staphylococcus aureus gyrB gene and an internal amplification control (IAC). The assay was performed in a sealed polypropylene PCR chip containing a flat-bottom reaction chamber with two immobilized capture probe spots. The surface of the reaction chamber was functionalized with NHS-PEG-azide and alkyne-modified capture probes for each amplicon, labeled with a light harvesting antenna ligand, and covalently attached as spots to the azide-modified reaction chamber using a copper(i)-catalyzed azide-alkyne cycloaddition. Asymmetric duplex-PCR was then performed with no template, one template or both templates present and with a europium ion carrier chelate labeled probe for each amplicon in the reaction. After amplification europium fluorescence was measured by scanning the reaction chamber as a 10 × 10 raster with 0.6 mm resolution in time-resolved mode. With this assay we were able to co-amplify and detect the amplification products of the gyrB target from 100, 1000 and 10,000 copies of isolated S. aureus DNA together with the amplification products from the initial 5000 copies of the synthetic IAC template in the same sealed reaction chamber. The addition of 10,000 copies of isolated non-target Escherichia coli DNA in the same reaction with 5000 copies of the synthetic IAC template did not interfere with the amplification or detection of the IAC. The dynamic range of the assay for the synthetic S. aureus gyrB target was three orders of magnitude and the limit of detection of 8 pM was obtained. This proof-of-concept study shows that the switchable lanthanide luminescent probes enable separation-free array-based multiplexed detection of the amplification products in a closed-tube PCR which can enable a higher degree of multiplexing than is currently feasible by using different spectrally separated fluorescent probes.

Confined chemiluminescence detection of nanomolar levels of H2O2 in a paper–plastic disposable microfluidic device using a smartphone

We report the design and characterization of a disposable light shielded paper–plastic microfluidic device that can detect nanomolar levels of H₂O₂ using a smartphone camera and a light sealed accessory.

A multiplex chemiluminescent biosensor for type B-fumonisins and aflatoxin B1 quantitative detection in maize flour

A multiplex chemiluminescence biosensor based on a lateral flow immunoassay was developed for on-site quantitative detection of fumonisins and aflatoxin B1 in maize.

A single-step enzyme immunoassay capillary sensor composed of functional multilayer coatings for the diagnosis of marker proteins

A single-step, easy-to-use enzyme immunoassay capillary sensor, composed of substrate-immobilized hydrophobic coating, hydrogel coating, and soluble coating containing an enzyme-labeled antibody, was developed.

Layer-by-layer generation of PEG-based regenerable immunosensing surfaces for small-sized analytes

Small molecules (haptens) like pharmaceuticals or peptides can serve as targets for antibody binding in competitive immunoassay-based flow-through assays. In this work, a strategy for preparing polyethylene glycol (PEG) coatings for subsequent hapten immobilization on glass-type silica surfaces is presented and characterized in detail. Two substrates bearing terminal silanol groups were utilized, a glass slide and a silicon wafer. First, surfaces were thoroughly cleaned and pretreated to generate additional silanol groups. Then, a silane layer with terminal epoxy groups was created using 3-glycidyloxypropyltrimethoxysilane (GOPTS). Epoxy groups were used to bind a layer of diamino-poly(ethylene glycol) (DAPEG) with terminal amino groups. Finally, the low molecular weight compound diclofenac was bound to the surface to be used as model ligand for competitive biosensing of haptens. The elementary steps were characterized using atomic force microscopy (AFM), water contact angle measurement, grazing-angle attenuated total reflection (GA-ATR) FT-IR spectroscopy, and X-ray photoelectron spectroscopy (XPS). The data collected using these techniques have confirmed the successive grafting of the molecular species, evidencing, that homogeneous monolayers were created on the silica surfaces and validated the proposed mechanism of functionalization. The resulting surfaces were used to investigate polyclonal anti-diclofenac antibodies recognition and reversibility using quartz crystal microbalance with dissipation (QCM-D) measurements or an automated flow-through immunoassay with chemiluminescence (CL) read-out. For both techniques, recognition and reversibility of the antibody binding were observed. The stability of sensors over time was also assessed and no decrease in CL response was observed upon 14 days in aqueous solution. The herein presented strategy for surface functionalization can be used in the future as reproducible and reusable universal platform for hapten biosensors.