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Author

Darius G. Rackus

Other affiliations: Durham University, ETH Zurich
Bio: Darius G. Rackus is an academic researcher from University of Toronto. The author has contributed to research in topics: Medicine & Microfluidics. The author has an hindex of 10, co-authored 13 publications receiving 494 citations. Previous affiliations of Darius G. Rackus include Durham University & ETH Zurich.

Papers
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Journal ArticleDOI
TL;DR: The basic concepts and recent histories of electrochemistry, biosensors, and microfluidics are introduced, and how they are combining to form new application-areas, including so-called "point-of-care" systems in which measurements traditionally performed in a laboratory are moved into the field.
Abstract: Electrochemistry, biosensors and microfluidics are popular research topics that have attracted widespread attention from chemists, biologists, physicists, and engineers. Here, we introduce the basic concepts and recent histories of electrochemistry, biosensors, and microfluidics, and describe how they are combining to form new application-areas, including so-called “point-of-care” systems in which measurements traditionally performed in a laboratory are moved into the field. We propose that this review can serve both as a useful starting-point for researchers who are new to these topics, as well as being a compendium of the current state-of-the art for experts in these evolving areas.

274 citations

Journal ArticleDOI
TL;DR: A compact and portable, field-deployable, point-of-care system relying on digital microfluidics that can rapidly test a small volume of capillary blood for disease-specific antibodies for measles and rubella is described.
Abstract: Serosurveys are useful for assessing population susceptibility to vaccine-preventable disease outbreaks. Although at-risk populations in remote areas could benefit from this type of information, they face several logistical barriers to implementation, such as lack of access to centralized laboratories, cold storage, and transport of samples. We describe a potential solution: a compact and portable, field-deployable, point-of-care system relying on digital microfluidics that can rapidly test a small volume of capillary blood for disease-specific antibodies. This system uses inexpensive, inkjet-printed digital microfluidic cartridges together with an integrated instrument to perform enzyme-linked immunosorbent assays (ELISAs). We performed a field validation of the system’s analytical performance at Kakuma refugee camp, a remote setting in northwestern Kenya, where we tested children aged 9 to 59 months and caregivers for measles and rubella immunoglobulin G (IgG). The IgG assays were determined to have sensitivities of 86% [95% confidence interval (CI), 79 to 91% (measles)] and 81% [95% CI, 73 to 88% (rubella)] and specificities of 80% [95% CI, 49 to 94% (measles)] and 91% [95% CI, 76 to 97% (rubella)] (measles, n = 140; rubella, n = 135) compared with reference tests (measles IgG and rubella IgG ELISAs from Siemens Enzygnost) conducted in a centralized laboratory. These results demonstrate a potential role for this point-of-care system in global serological surveillance, particularly in remote areas with limited access to centralized laboratories.

112 citations

Journal ArticleDOI
TL;DR: The integration of NMEs with the versatile fluid-handling system digital microfluidics (DMF), for eventual application to distributed diagnostics outside of the laboratory, was reported.
Abstract: Nanostructured microelectrodes (NMEs) are three-dimensional electrodes that have superb sensitivity for electroanalysis. Here we report the integration of NMEs with the versatile fluid-handling system digital microfluidics (DMF), for eventual application to distributed diagnostics outside of the laboratory. In the new methods reported here, indium tin oxide DMF top plates were modified to include Au NMEs as well as counter and pseudoreference electrodes. The new system was observed to outperform planar sensing electrodes of the type that are typically integrated with DMF. A rubella virus (RV) IgG immunoassay was developed to evaluate the diagnostic potential for the new system, relying on magnetic microparticles coated with RV particles and analysis by differential pulse voltammetry. The limit of detection of the assay (0.07 IU mL−1) was >100× below the World Health Organization defined cut-off for rubella immunity. The sensitivity of the integrated device and its small size suggest future utility for distributed diagnostics.

56 citations

Journal ArticleDOI
TL;DR: This work designs a platform featuring a three-electrode electrochemical cell integrated in a microfabricated DMF device, removing the need for external electrodes and allowing for complete droplet control, and proposes that this platform and variations thereof may be a useful new tool for microscale electroanalysis.
Abstract: Digital microfluidics (DMF) is an emerging technique for manipulating small volumes of liquids. DMF is particularly well suited for analytical applications as it allows automated handling of discrete samples, and it has been integrated with several inline analysis techniques. However, examples of the integration of DMF with electroanalytical methods are notably scarce, and those that have been reported rely on external electrodes that impose limitations on complexity. To combine the full capabilities of DMF with voltammetry, we designed a platform featuring a three-electrode electrochemical cell integrated in a microfabricated DMF device, removing the need for external electrodes and allowing for complete droplet control. The performance of the DMF/voltammetry system is comparable to that of a commercial screen printed electrode, and the new platform was applied to generating a calibration series for acetaminophen with a limit of detection of 76 μM and good precision (4% average RSD), all with minimal hum...

51 citations

Journal ArticleDOI
TL;DR: DMF-IP and P-CLIP-DMF-IP are rapid, automated, and multiplexed methods that have the potential to reduce the time and effort required for IP sample preparations with applications in the fields of pharmacy, biomarker discovery, and protein biology.
Abstract: Immunoprecipitation (IP) is a common method for isolating a targeted protein from a complex sample such as blood, serum, or cell lysate. In particular, IP is often used as the primary means of target purification for the analysis by mass spectrometry of novel biologically derived pharmaceuticals, with particular utility for the identification of molecules bound to a protein target. Unfortunately, IP is a labor-intensive technique, is difficult to perform in parallel, and has limited options for automation. Furthermore, the technique is typically limited to large sample volumes, making the application of IP cleanup to precious samples nearly impossible. In recognition of these challenges, we introduce a method for performing microscale IP using magnetic particles and digital microfluidics (DMF-IP). The new method allows for 80% recovery of model proteins from approximately microliter volumes of serum in a sample-to-answer run time of approximately 25 min. Uniquely, analytes are eluted from these small samp...

33 citations


Cited by
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01 Jan 1994
TL;DR: Micromachining technology was used to prepare chemical analysis systems on glass chips that utilize electroosmotic pumping to drive fluid flow and electrophoretic separation to distinguish sample components with no moving parts.
Abstract: Micromachining technology was used to prepare chemical analysis systems on glass chips (1 centimeter by 2 centimeters or larger) that utilize electroosmotic pumping to drive fluid flow and electrophoretic separation to distinguish sample components. Capillaries 1 to 10 centimeters long etched in the glass (cross section, 10 micrometers by 30 micrometers) allow for capillary electrophoresis-based separations of amino acids with up to 75,000 theoretical plates in about 15 seconds, and separations of about 600 plates can be effected within 4 seconds. Sample treatment steps within a manifold of intersecting capillaries were demonstrated for a simple sample dilution process. Manipulation of the applied voltages controlled the directions of fluid flow within the manifold. The principles demonstrated in this study can be used to develop a miniaturized system for sample handling and separation with no moving parts.

1,412 citations

Journal ArticleDOI
TL;DR: This Review summarizes advances from the past 5 years in the development of electrochemical sensors for clinically relevant biomolecules, including small molecules, nucleic acids, and proteins and addresses the remaining challenges and opportunities.
Abstract: Rapid progress in identifying biomarkers that are hallmarks of disease has increased demand for high-performance detection technologies. Implementation of electrochemical methods in clinical analysis may provide an effective answer to the growing need for rapid, specific, inexpensive, and fully automated means of biomarker analysis. This Review summarizes advances from the past 5 years in the development of electrochemical sensors for clinically relevant biomolecules, including small molecules, nucleic acids, and proteins. Various sensing strategies are assessed according to their potential for reaching relevant limits of sensitivity, specificity, and degrees of multiplexing. Furthermore, we address the remaining challenges and opportunities to integrate electrochemical sensing platforms into point-of-care solutions.

639 citations

Journal ArticleDOI
TL;DR: The potential of immunosensors destined for application in food and environmental analysis, and cancer biomarker diagnosis is addressed and emphasis is given to the approaches that have been used for construction of electrochemical immunosensing.

373 citations

Journal ArticleDOI
TL;DR: The most recent advances in the DMF platforms are discussed, and the feasibility of developing multifunctional packages for performing complete sets of processes of biochemical assays, particularly for point-of-care applications is evaluated.
Abstract: Following the development of microfluidic systems, there has been a high tendency towards developing lab-on-a-chip devices for biochemical applications. A great deal of effort has been devoted to improve and advance these devices with the goal of performing complete sets of biochemical assays on the device and possibly developing portable platforms for point of care applications. Among the different microfluidic systems used for such a purpose, digital microfluidics (DMF) shows high flexibility and capability of performing multiplex and parallel biochemical operations, and hence, has been considered as a suitable candidate for lab-on-a-chip applications. In this review, we discuss the most recent advances in the DMF platforms, and evaluate the feasibility of developing multifunctional packages for performing complete sets of processes of biochemical assays, particularly for point-of-care applications. The progress in the development of DMF systems is reviewed from eight different aspects, including device fabrication, basic fluidic operations, automation, manipulation of biological samples, advanced operations, detection, biological applications, and finally, packaging and portability of the DMF devices. Success in developing the lab-on-a-chip DMF devices will be concluded based on the advances achieved in each of these aspects.

337 citations

Journal ArticleDOI
16 Aug 2017-Polymers
TL;DR: This review considers bioreceptors to be immobilized on hydrogel based biosensors, their advantages and disadvantages, and immobilization techniques, and identifies the hydrogels that are most favored for this type of biosensor, as well as the predominant transduction strategies.
Abstract: Biosensors that detect and convert biological reactions to a measurable signal have gained much attention in recent years. Between 1950 and 2017, more than 150,000 papers have been published addressing the applications of biosensors in different industries, but to the best of our knowledge and through careful screening, critical reviews that describe hydrogel based biosensors for biomedical applications are rare. This review discusses the biomedical application of hydrogel based biosensors, based on a search performed through Web of Science Core, PubMed (NLM), and Science Direct online databases for the years 2000⁻2017. In this review, we consider bioreceptors to be immobilized on hydrogel based biosensors, their advantages and disadvantages, and immobilization techniques. We identify the hydrogels that are most favored for this type of biosensor, as well as the predominant transduction strategies. We explain biomedical applications of hydrogel based biosensors including cell metabolite and pathogen detection, tissue engineering, wound healing, and cancer monitoring, and strategies for small biomolecules such as glucose, lactate, urea, and cholesterol detection are identified.

276 citations