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a) Custom-made chip holder for the electrical and fluidic connection and the sealing of the individual inlets. b) Photograph of the chip holder connected to the compact potentiostat. Flow is induced by a syringe pump via the silicone tubing.
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We present an electrochemical lab-on-a-chip (LOC) platform for the simultaneous detection of up to four different analytes. The possibility to separately immobilize different assays in a channel network, without active valves, was successfully demonstrated using a model assay linked to glucose oxidase. This enables the detection of various analytes...
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... 500 μm) are connected in a set of T-junctions to the common in-and outlet. A cross-sensitivity can only occur when hydrogen peroxide diffuses back to a junction point. Therefore, a safety diffusion path length of 6.3 mm prevents this effect. Common microfluidic and electrical connection are carried out through a custom-made chip holder (see fig. 2). The fluidic connection block is actuated by magnetic force and allows a fast and easy chip loading. Vacuum cups (Nordson Corp., Germany) and silicone tubing are used to connect the chip to the syringe pump (Harvard Apparatus, USA) to induce a constant volume flow through the channel network. Amperometric readout is carried out with a ...
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A lab-on-a-chip (LOC)-based non-invasive optical sensor for measuring glucose in saliva was fabricated. Existing glucose sensors utilizing blood require acquisition of a blood sample by pricking the finger, which is painful and inconvenient. To overcome these limitations, we propose a non-invasive glucose sensor with LOC, micro-electro-mechanical s...
Citations
... Later, the acid treated sensor probes were directly utilized for the immobilization of capture antibodies. In the second strategy, the sensor probes were incubated in methanol:HCl (1:1) for 1 hr at RT (anticipating generation of carboxyl groups) followed by a freshly prepared mixture of EDC (100 mM) and NHS (200 mM) (prepared in 0.1 M MES buffer in 0.9% NaCl, pH 6) for another 1 hr [21]. Then, they were heated in a hot air oven at 60 • C for 20 mins and subsequently washed in MES buffer. ...
SARS-CoV-2 nucleocapsid protein-based COVID-19 diagnosis is a promising alternative to the high-priced, time-consuming, and labor-intensive RT-PCR tests. Here, we developed a rapid, dip-type, wash-free plasmonic fiber optic absorbance biosensor (P-FAB) strategy for the point-of-care detection of SARS-CoV-2 N-protein, expressed abundantly during the infection. P-FAB involves a sandwich assay with plasmonic labels on the surface of a U-bent fiber optic sensor probe with a high evanescent wave absorbance (EWA) sensitivity. The SARS-CoV-2 N-protein is quantified in terms of the change in the intensity of the light propagating through the U-bent sensor probe coupled to a green LED and a photodetector. Firstly, the optical fiber material (silica vs. polymeric optical fiber), was evaluated to realize a sensitive sensor platform. The optimal size of AuNP labels (20, 40, and 60 nm) to achieve high sensitivity and a lower limit of detection (LoD) was investigated. Following the P-FAB strategy, fused silica/glass optical fiber (GOF) U-bent senor probe and citrate-capped AuNP labels (size ~40 nm) gave rise to an LoD down to ~2.5 ng/mL within 10 mins of read-out time. Further, studies on development and validation of a point of care (PoC) read-out device, and preclinical studies are in progress.
... The channel width of the so far employed miLab chip and the published parallel approach of the MulitLab is 500 µm [113,220,221]. The channel width mainly influences the ratio of SU-8 surface area (bottom of the chip) to dry-film photoresist (DFR) surface area (walls and cover). ...
Für die effektive Behandlung einer Krankheit ist eine genaue und frühzeitige Diagnose lebenswichtig, insbesondere bei Krebs. Allerdings werden Krankheiten oft nur dann diagnostiziert, wenn der Patient symptomatisch ist. Treten die Symptome erst in einem sehr späten Stadium der Erkrankung auf, kann dies zu einer höheren Sterblichkeit führen. In der Regel werden Untersuchungen aus Kostengründen nicht routinemäßig durchgeführt und Symptome auch gelegentlich falsch interpretiert. Um regelmäßige Untersuchungen für die breite Bevölkerung zugänglich zu machen, ist ein kostengünstiges, schnelles und zuverlässiges Diagnosesystem nötig. Hierfür könnte eine so genannte Lab-on-a-Chip (LOC)-Plattform zur On-Chip Diagnose ein vielversprechender Kandidat sein.
Diese Arbeit konzentriert sich auf die Entwicklung einer solchen LOC-Plattform für den Nachweis von miRNAs als Biomarker für Hirnkrebs. Darüber hinaus kann das entwickelte Sensorprinzip auf verschiedene Krebsarten oder andere Krankheiten wie Herz-Kreislauf-Erkrankungen oder Störungen des Nervensystems übertragen werden. Für den Nachweis der miRNAs wird ein elektrochemischer, mikrofluidischer Biosensor mit verschiedenen Assay-Typen kombiniert, die die Detektion nahezu jeder RNA ermöglicht. Darüber hinaus basiert die Biochip-Plattform auf einer kostengünstigen, polymerbasierten Fertigung.
Für die Implementierung eines Assays zur miRNA Detektion wird eine neuartige Methode, basierend auf der kürzlich entdeckten CRISPR/Cas-Technologie, mit klassischen Assay-An-sätzen in Bezug auf Sensitivität, Selektivität und Flexibilität verglichen. Aufgrund seiner Überlegenheit in allen Bereichen wird das innovative CRISPR/Cas-basierte Assay als Detektionsprinzip gewählt. Für eine klinische Validierung werden verschiedene Serumproben von Kindern mit Medulloblastom (einer aggressiven Form von Hirnkrebs) mit der entwickelten LOC-Plattform analysiert. Die Resultate werden mit Messergebnissen einer qRT-PCR, dem aktuellen Goldstandard, verglichen, welche die Ergebnisse der LOC-Platform erfolgreich verifiziert.
Zur Diagnose vieler Krankheiten reicht oft ein Biomarker als Nachweis nicht aus. Um eine Patientenprobe gleichzeitig auf mehrere Analyten hin zu untersuchen, wird die entwickelte LOC-Plattform in Richtung Multiplexing erweitert. Hierzu wird eine einkanalige Multianalyten-Lab-on-a-Chip-Plattform, genannt SCMultiLab, konzipiert. Für die Multianalytenmessung ist der Kanal in mehrere Detektionsstellen aufgeteilt, die durch inaktive Abschnitte getrennt sind. Zur Optimierung des Tetektionsprinzips wird der Einkanalbiosensor in ein Simulationsmodell überführt und verschiedene Designstudien durchgeführt. Aus den daraus hergeleiteten Designregeln werden verschiedene Versionen der SCMultiLab-Plattform hergestellt. Anschließend werden Grundsatzmessungen durchgeführt und schließlich miRNAs in verschiedenen Konzentrationen gemessen. Dies zeigt, dass der SCMultiLab-Chip ein sensibles und einfach zu skalierendes Diagnosewerkzeug ist, das den Weg für einen amplifikationsfreien Nukleinsäurenachweis ebnet.
... Furthermore, miniaturized electrochemical sensors have also been proved as an efficient tool for biomolecule detection [1]. For example, integrating lab-on-a-chip technology with microfluidics result into simpler, portable and automated biosensing platforms for efficient onsite analysis of target molecules [1,117,118]. The integrated detection systems have contributed significantly to the field of biosensing by scaling down the dimensions and volumes of analytes required for analysis with fast diffusion. ...
Biomolecules are integral constituents of living beings which regulate numerous biochemical functions of the body. Analysis of various small molecules (metabolites, neurotransmitters, amino acids, vitamins) and macromolecules (nucleic acids, proteins) is of prime importance in modern time due to increasing disbalance in natural metabolism of human body. Irregularities and alteration in concentration of biomolecules lead to different kinds of genetic, metabolic and cancerous diseases which have created a great requirement of highly sensitive, accurate and stable detection systems for their quick and specific screening. In this review, redox interactions of biomolecules at carbon based electrode interfaces have been discussed using voltammetry. It is divided into subsections, starting with an introduction into the field and a description of its current state. This is followed by a large section describing carbon nanomaterials (CNs) based voltammetric sensors for different small biomolecules and macromolecules. The next section of the review gives conclusion, challenges and future perspectives in sensing biomolecules at CNs based electrodes. Advanced approaches for fabrication of portable integrated electrochemical devices for various point of care diagnostic applications have also been included at the end.
... To meet these challenges facing POCT devices, DFR technology has been recently employed for the fabrication of disposable and low-cost biosensors [9][10][11][12][13][14] . Compared to soft and liquid lithographic materials, such as PDMS or SU-8, DFRs present many benefits: they (i) are available in a variety of compositions and thicknesses (from a few microns to several millimeters); (ii) have a very rough surface area, which facilitates adhesion to various materials; (iii) feature excellent thickness uniformity; (iv) offer cheap, facile, and high-throughput fabrication for mass production; (v) are easy to cut with various low-cost tools, like a simple pair of scissors; and (vi) allow for the creation of three-dimensional structures, such as microfluidic channels, by stacking multiple DFR layers on top of each other. ...
In recent years, biomarker diagnostics became an indispensable tool for the diagnosis of human disease, especially for the point-of-care diagnostics. An easy-to-use and low-cost sensor platform is highly desired to measure various types of analytes (e.g., biomarkers, hormones, and drugs) quantitatively and specifically. For this reason, dry film photoresist technology-enabling cheap, facile, and high-throughput fabrication-was used to manufacture the microfluidic biosensor presented here. Depending on the bioassay used afterwards, the versatile platform is capable of detecting various types of biomolecules. For the fabrication of the device, platinum electrodes are structured on a flexible polyimide (PI) foil in the only clean-room process step. The PI foil serves as a substrate for the electrodes, which are insulated with an epoxy-based photoresist. The microfluidic channel is subsequently generated by the development and lamination of dry film photoresist (DFR) foils onto the PI wafer. By using a hydrophobic stopping barrier in the channel, the channel is separated into two specific areas: an immobilization section for the enzyme-linked assay and an electrochemical measurement cell for the amperometric signal readout. The on-chip bioassay immobilization is performed by the adsorption of the biomolecules to the channel surface. The glucose oxidase enzyme is used as a transducer for electrochemical signal generation. In the presence of the substrate, glucose, hydrogen peroxide is produced, which is detected at the platinum working electrode. The stop-flow technique is applied to obtain signal amplification along with rapid detection. Different biomolecules can quantitatively be measured by means of the introduced microfluidic system, giving an indication of different types of diseases, or, in regard to therapeutic drug monitoring, facilitating a personalized therapy.
... Our approach driving force behind the flexibility of this microfluidic chip. Thus, this biosensor system allows to combine not only di erent assay formats, such as competitive or sandwich, but also di erent advanced "omics" techniques like proteomics and genomics with each other simultaneously [39]. In this thesis, glucose oxidase (GOx) is used as the labeling enzyme with glucose for its appropriate substrate. ...
... This H 2 O 2 cloud is subsequently flushed over the electrochemical cell by restarting the flow. The longer the stop-time is, the higher will be the signal response [39,40]. ...
... Therewith, this approach enables to overcome technical and non-technical limitations of LOC platforms in corporation with new functional features. Thus, it o ers (i) simple and low-cost fabrication allowing mass-production, (ii) easy handling, (iii) reagent loading by capillary actions, (iv) low sample/reagent consumption, (v) adequacy with various biomolecules immobilization, and (vi) the possibility for simultaneous multi-analyte detection [39,40]. ...
Early and accurate diagnosis of a specific disease plays a decisive role for its effective treatment. However, in many cases the clinical findings, based on a single biomarker detection alone, are not sufficient for the appropriate diagnosis as well as monitoring of its treatment. Furthermore, it is highly desirable to screen multi-analytes (e.g. various diseases and drugs) at the same time enabling a low-cost, quick and reliable quantification. Thus, multiplexing, simultaneous detection of different analytes from a single sample, has become in recent years essential for diagnostics, especially for point-of-care testing (POCT). This thesis focuses on the scientific issue regarding the sensitivity enhancement of microfluidic biosensor platforms. Simulations, design studies and experiments are employed to investigate the interplay between the immobilization area and the resulting sensitivity. Thereby, a novel concept comprising design rules for microfluidic biosensors using the stop-flow technique has been introduced. In combination with different technical measures it allows the realization of an electrochemical lab-on-a-chip (LOC) platform for the fast, sensitive and simultaneous POCT in clinically relevant samples. This system employs a universally applicable, bioaffinity based biomolecule immobilization along with an amperometric readout. By means of the dry film photoresist technology, the fabrication of disposable microfluidic biosensors is enabled with high yield on wafer-level. The presented LOC platform offers three different biosensors with a microfluidic channel network of two, four or eight discrete immobilization sections, each with a volume of 680 nl. They can be actuated by individual channel inlets allowing a high flexibility in the assay design with respect to its format (e.g. competitive) and its technology (e.g. genomics). The feasibility for multiplexing is successfully demonstrated with DNA-based antibiotic assays for tetracycline and streptogramin, both important growth promoters in livestock breeding. The extensive usage of antibiotics is one of the major causes of the multi-drug-resistant bacteria and so, it has to be kept under surveillance. This platform allows the simultaneous POCT of different antibiotics from human plasma along with a limit of detection of less than 10 ng ml⁻¹, a wide working range up to 1,600 ng ml⁻¹ and inter-assay precisions of about 10 %. Moreover, the microfluidic LOC system provides a low consumption of reagent and sample, reduces the total assay time drastically with a sample-to-result time of only 10 min. The shelf-life of the biosensors is proven to be at least 3 months at +4 °C. The introduced design concept with specific technical measures facilitates the implementation of microfluidic multiplexed biosensors in a low-cost, compact, and at the same time sensitive manner. This platform targets the POCT in the first place, yet, owing to its multiplexing approach it can be expanded for in vitro diagnostics.
This review provides a detailed literature survey on microfluidics and its road map toward kidney-on-chip technology. The whole review has been tailored with a clear description of crucial milestones in regenerative medicine, such as bioengineering, tissue engineering, microfluidics, microfluidic applications in biomedical engineering, capabilities of microfluidics in biomimetics, organ-on-chip, kidney-on-chip for disease modeling, drug toxicity, and implantable devices. This paper also presents future scope for research in the bio-microfluidics domain and biomimetics domain.
Utilizing biosensors for multiplexed detection can greatly increase analysis throughput and thus, the amount of information obtained in a single assay. The microfluidic chip, a type of micro-total analysis system (µTAS), has provided a necessary platform for portable and high-throughput biosensors. Biosensors and microfluidic chips are powerful individually, and their super combination is very meaningful for analytical especially for biological applications. In this paper, every kind of microfluidic-chip-integrated electronic biosensors including some emerging technologies for simultaneous detection of multiple analytes are reviewed. Different ways to reduce or avoid cross-talking and more efforts to achieve lab on chip multisensors were also introduced to help readers form a general idea of current developments in different angles.
Fast and easy-to-handle multi-analyte single-use sensors are of increasing interest for many fields such as medical analysis or environmental and food control. This report presents an electrochemical and universally applicable microfluidic platform enabling the simultaneous readout of up to eight enzyme-linked assays. For this purpose, microfluidic channel networks are designed each comprising distinct numbers of immobilization sections with a very low volume of 680 nl each. These immobilization sections can be actuated separately for an individual functionalization and assay procedure. To demonstrate the applicability of this platform in the context of surveillance and monitoring of different antibiotics, the simultaneous detection of the two commonly employed antibiotics tetracycline and pristinamycin is investigated. The limits of detection (LOD) are determined to 6.33 and 9.42 ng ml-1 for tetracycline and pristinamycin, respectively, with inter-assay coefficients of variation (CV) below 10 %. The device provides a shelf-life of at least three months. The ability for multi-analyte measurements in a complex medium is demonstrated by the simultaneous detection of both antibiotics in spiked human plasma within a sample-to-result time of 15 minutes.
