Development of a label-free microfluidic impedimetric immunoassay for anti-SPAG16 antibody

ABSTRACTA recently found biomarker regarding multiple sclerosis, namely the anti-SPAG16 antibody (Ab), could be a potential way for early detection, prognosis and diagnosis of said autoimmune disease. Merging electrochemical analysis with a microfluidic system is a novel approach, which avoids the use of labelling steps as seen in traditional ELISA immunoassays. In this study, aluminium interdigitated electrodes on polystyrene-coated PET foils were implemented in a microfluidic flow cell to bind and detect SPAG16 Abs by impedimetric measurements. The coated PET foils showed a clear affinity for the fusion protein SPAG16-THIO and thioredoxin (THIO). Determining sensitivity and specificity of antibody-antigen binding using a microfluidic ELISA immunoassay has revealed the test to be unreliable by showing no linear pattern of a dilution series of the standard and producing skewed inconsistent results. The impedimetric analysis showed opposite results of what one would expect. The systems efficiency is in need to be revised and optimised before undergoing actual diagnostic tests. Further advancement could be done by reducing leakage, securing a more stable entrance for injection and circumventing the occurence of air bubbles in the wells.SAMENVATTINGMultiple sclerosis (MS) is een auto-immune ziekte, gekenmerkt door inflammatie van het centraal zenuwstelsel en demyelinisatie van axonen. Een recent gevonden proteïne, namelijk het anti-SPAG16 antilichaam, is bewezen een biomerker te zijn voor MS. Met behulp van een elektrochemisch analytisch systeem gecombineerd met microfluidica zou men anti-SPAG16 antilichamen kunnen opsporen voor vroegtijdige detectie, prognose en diagnose. Het grote voordeel tegenover traditionele ELISA testen is het elimineren van labelling stappen waardoor de immunoassay goedkoper en gebruiksvriendelijk wordt. In deze studie werden overlappende aluminium elektrodes op polystyreen-gecoate PET-plaatjes geïmplementeerd in een microfluidische flow cell voor binding en detectie van anti-SPAG16 antilichamen door middel van impedimetrische metingen. De gecoate PET-plaatjes vertonen een duidelijke affiniteit voor 0,1 μg/ml SPAG16 en THIO. Het bepalen van sensitiviteit en specificiteit van antilichaam-antigen binding, gebruikmakende van een ELISA immunoassays, gaf aan dat de test onbetrouwbaar is doordat geen duidelijk patroon voor standaardoplossingen zichtbaar was en resultaten vertekend en inconsistent bleken te zijn. De impedimetrische analyse vertoonde tevens onbetrouwbare resultaten, waarbij een omgekeerd effect werd geobserveerd van wat er in theorie zou moeten gebeuren. De efficiëntie van het systeem moet herzien en geoptimaliseerd worden voordat men het voor diagnostische testen kan gebruiken. Verdere vorderingen zouden gerealiseerd kunnen worden door lekkages te reduceren, steviger bevestigen van de PDMS-ingang en de ontwikkeling van luchtbellen in de wells te vermijden.

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Integrated impedance sensing of liquid sample plug flow enables automated high throughput NMR spectroscopy

Microsystems & Nanoengineering ◽

10.1038/s41378-021-00253-2 ◽

2021 ◽

Vol 7 (1) ◽

Cited By ~ 1

Author(s):

Omar Nassar ◽

Mazin Jouda ◽

Michael Rapp ◽

Dario Mager ◽

Jan G. Korvink ◽

...

Keyword(s):

Nmr Spectroscopy ◽

High Throughput ◽

Plug Flow ◽

Microfluidic System ◽

High Resolution Spectroscopy ◽

Dead Volume ◽

Absolute Difference ◽

Immiscible Fluid ◽

Flow Sensors ◽

Novel Approach

AbstractA novel approach for automated high throughput NMR spectroscopy with improved mass-sensitivity is accomplished by integrating microfluidic technologies and micro-NMR resonators. A flow system is utilized to transport a sample of interest from outside the NMR magnet through the NMR detector, circumventing the relatively vast dead volume in the supplying tube by loading a series of individual sample plugs separated by an immiscible fluid. This dual-phase flow demands a real-time robust sensing system to track the sample position and velocities and synchronize the NMR acquisition. In this contribution, we describe an NMR probe head that possesses a microfluidic system featuring: (i) a micro saddle coil for NMR spectroscopy and (ii) a pair of interdigitated capacitive sensors flanking the NMR detector for continuous position and velocity monitoring of the plugs with respect to the NMR detector. The system was successfully tested for automating flow-based measurement in a 500 MHz NMR system, enabling high resolution spectroscopy and NMR sensitivity of 2.18 nmol s1/2 with the flow sensors in operation. The flow sensors featured sensitivity to an absolute difference of 0.2 in relative permittivity, enabling distinction between most common solvents. It was demonstrated that a fully automated NMR measurement of nine individual 120 μL samples could be done within 3.6 min or effectively 15.3 s per sample.

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Tethered Lipid Membranes as a Nanoscale Arrangement Towards Non-Invasive Analysis of Acute Pancreatitis

Biomedicines ◽

10.3390/biomedicines9070755 ◽

2021 ◽

Vol 9 (7) ◽

pp. 755

Author(s):

Rima Budvytyte ◽

Akvile Milasiute ◽

Dalius Vitkus ◽

Kestutis Strupas ◽

Aiste Gulla ◽

...

Keyword(s):

Acute Pancreatitis ◽

Lipid Membranes ◽

Electrochemical Impedance ◽

Membrane Integrity ◽

Electrochemical Technique ◽

Label Free ◽

Non Invasive ◽

Novel Approach ◽

Analytical System ◽

Shock Proteins

Extracellular heat shock proteins (HSPs) mediate immunological functions and are involved in pathologies such as infection, stress, and cancer. Here, we demonstrated the dependence of an amount of HSP70 and HSP90 in serum vs. severity of acute pancreatitis (AP) on a cohort of 49 patients. Tethered bilayer lipid membranes (tBLMs) have been developed to investigate HSPs’ interactions with tBLMs that can be probed by electrochemical impedance spectroscopy (EIS). The results revealed that HSP70 and HSP90 interact via different mechanisms. HSP70 shows the damage of the membrane, while HSP90 increases the insulation properties of tBLM. These findings provide evidence that EIS offers a novel approach for the study of the changes in membrane integrity induced by HSPs proteins. Herein, we present an alternative electrochemical technique, without any immunoprobes, that allows for the monitoring of HSPs on nanoscaled tBLM arrangement in biologics samples such us human urine. This study demonstrates the great potential of tBLM to be used as a membrane based biosensor for novel, simple, and non-invasive label-free analytical system for the prediction of AP severity.

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Mercury Electrodes in Nucleic Acid Electrochemistry: Sensitive Analytical Tools and Probes of DNA Structure. A Review

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20040715 ◽

2004 ◽

Vol 69 (4) ◽

pp. 715-747 ◽

Cited By ~ 40

Author(s):

Miroslav Fojta

Keyword(s):

Nucleic Acid ◽

Nucleic Acids ◽

Double Helix ◽

Dna Structure ◽

Electrochemical Analysis ◽

Label Free ◽

Helix Formation ◽

Mercury Electrodes ◽

Dna Strand ◽

Dna Double Helix

This review is devoted to applications of mercury electrodes in the electrochemical analysis of nucleic acids and in studies of DNA structure and interactions. At the mercury electrodes, nucleic acids yield faradaic signals due to redox processes involving adenine, cytosine and guanine residues, and tensammetric signals due to adsorption/desorption of polynucleotide chains at the electrode surface. Some of these signals are highly sensitive to DNA structure, providing information about conformation changes of the DNA double helix, formation of DNA strand breaks as well as covalent or non-covalent DNA interactions with small molecules (including genotoxic agents, drugs, etc.). Measurements at mercury electrodes allow for determination of small quantities of unmodified or electrochemically labeled nucleic acids. DNA-modified mercury electrodes have been used as biodetectors for DNA damaging agents or as detection electrodes in DNA hybridization assays. Mercury film and solid amalgam electrodes possess similar features in the nucleic acid analysis to mercury drop electrodes. On the contrary, intrinsic (label-free) DNA electrochemical responses at other (non-mercury) solid electrodes cannot provide information about small changes of the DNA structure. A review with 188 references.

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Label-free biosensors based on in situ formed and functionalized microwires in microfluidic devices

The Analyst ◽

10.1039/c5an01240f ◽

2015 ◽

Vol 140 (23) ◽

pp. 7896-7901 ◽

Cited By ~ 16

Author(s):

Yanlong Xing ◽

Andreas Wyss ◽

Norbert Esser ◽

Petra S. Dittrich

Keyword(s):

Microfluidic Devices ◽

Microfluidic System ◽

Label Free ◽

System P

Label-free biosensors based on in situ formed and functionalized TTF–Au wires were developed using an integrated microfluidic system.

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Application of a Terahertz System Combined with an X-Shaped Metamaterial Microfluidic Cartridge

Micromachines ◽

10.3390/mi11010074 ◽

2020 ◽

Vol 11 (1) ◽

pp. 74

Author(s):

Shih-Ting Huang ◽

Shen-Fu Hsu ◽

Kai-Yuan Tang ◽

Ta-Jen Yen ◽

Da-Jeng Yao

Keyword(s):

Far Infrared ◽

Infrared Region ◽

Microfluidic System ◽

Electromagnetic Response ◽

Thz Radiation ◽

Similar Species ◽

Label Free ◽

Plasmonic Sensor ◽

Molecular Fingerprint ◽

Highly Sensitive Detection

Terahertz (THz) radiation has attracted wide attention for its ability to sense molecular structure and chemical matter because of a label-free molecular fingerprint and nondestructive properties. When it comes to molecular recognition with terahertz radiation, our attention goes first towards the absorption spectrum, which is beyond the far infrared region. To enhance the sensitivity for similar species, however, it is necessary to apply an artificially designed metamaterial sensor for detection, which confines an electromagnetic field in an extremely sub-wavelength space and hence receives an electromagnetic response through resonance. Once the resonance is caused through the interaction between the THz radiation and the metamaterial, a minute variation might be observed in the frequency domain. For a geometric structure of a metamaterial, a novel design called an X-shaped plasmonic sensor (XPS) can create a quadrupole resonance and lead to sensitivity greater than in the dipole mode. A microfluidic system is able to consume reagents in small volumes for detection, to diminish noise from the environment, and to concentrate the sample into detection spots. A microfluidic device integrated with an X-shaped plasmonic sensor might thus achieve an effective and highly sensitive detection cartridge. Our tests involved not only measurements of liquid samples, but also the performance of a dry bio-sample coated on an XPS.

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