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Microfluidic Based Biosensors and Applications
Published in Sibel A. Ozkan, Bengi Uslu, Mustafa Kemal Sezgintürk, Biosensors, 2023
Münteha Nur Sonuç Karaboğa, Mustafa Kemal Sezgintürk
In their study, Pinto et al. (69) developed a PDMS microfluidic immunosensor integrated into a metal-oxide-semiconductor (CMOS) optical detection system to detect cortisol in saliva rapidly and reliably. Immunosensors are structures in which antibodies are designed as bioreceptors for specific molecular recognition of antigens and a stable immunocomplex is formed as a result of interaction between them (70). Developed rapidly and non-invasively in saliva as an alternative to blood, this study is based on the covalent immobilization of a polyclonal anti-IgG coating antibody (Ab) on a PDMS surface. Coating Ab binds capture Ab, a specific IgG for cortisol. Horseradish peroxidase (HRP)-labeled cortisol was added to the sample to compete with the cortisol in the sample. Cortisol measurement was performed by optical absorption at 450 nm. Researchers have optimized characteristics such as microfluidic geometry, immobilization parameters and immunoassay conditions. Under optimized conditions, cortisol could be analyzed in 35 minutes with a detection range of 0.01–20 ng/mL and a limit of detection (LOD) of 18 pg/mL.
Analytical Applications of Piezoelectric Crystal Biosensors
Published in Loïc J. Blum, Pierre R. Coulet, Biosensor Principles and Applications, 2019
John H. T. Luong, George G. Guilbault
With time, as more anti–IgG-IgG (antibody-antigen) complexes formed, there was a frequency increase. This apparent contradiction of the classic microgravimetric behavior, they explain, represents the interfacial immunochemical reaction, which is different from the bulk antigen-antibody interaction. Based on the experimental data obtained, it was proposed that the frequency response was associated with changes in surface interactions during the immunochemical reaction. Precipitin formation generally leads to increased hydrophilicity, and the viscoelastic properties of proteins under shear stress at interfaces are strongly influenced by cross-binding and intermolecular interactions. Further theoretical and experimental work on nonequilibrium interfacial viscosity effects is required to substantiate these arguments.
Microfluidics-Based Metallic Nanoparticle Synthesis and Applications
Published in Tuhin S. Santra, Microfluidics and Bio-MEMS, 2020
Kavitha Illath, Ashwin Kumar Narasimahan, Moeto Nagai, Syrpailyne Wankhar, Tuhin S. Santra
Apart from other techniques, Raman scattering is a powerful phenomenon used for sensing biological materials. It is a two-photon event, involving absorption of photons and scattering them inelastically. The shift in the wavelength of the scattered photons corresponds to specific vibrational modes present in the molecule, giving rise to a specific Raman signature for each molecule. Raman scattering is a weak process, where only 1 in every 106–108 photons is scattered inelastically. For sensitive detection of this scattered light, different enhancement mechanisms are used, such as resonant Raman scattering and SERS [34, 56]. Between these two techniques, SERS shows efficient enhancement for metallic nanomaterials. When an analyte molecule is attached on a metallic nanomaterial surface, it results in changes in the oscillation of plasmons, increasing the strength of the Raman signals. A scattered perpendicular signal is detected using a detector, which shows an enhancement as large as 9 × 107, reported by Haynes et al. in 2002 [33]. Several similar works have been carried out with different metallic NPs, such as gold, silver, and composite metallic nanomaterials. In 2014, a magnetic iron oxide/silver nanocomposite (Fe3O4@Ag@streptavidin@anti-IgG) was fabricated that can selectively detect human immunoglobulin G (IgG) in blood samples via SERS, as shown in Fig. 10.33a, b [7]. The magnetic property of the nanocomposite enables separation of the composite from a blood sample after anti-IgG antibodies have bound with the target. The spectral peaks at amide I (1650 cm−1 shift) and amide II (1539 cm−1 shift) bands observed show the interaction between antibody and nanocomposite that enables them to capture IgG. The ratio of these peaks was used for the quantification of the IgG target. This method enabled better sensitivity at 0.6 ng L−1 when compared to other similar non-SERS immunoassays.
Hemolysis during short-term mechanical circulatory support: from pathophysiology to diagnosis and treatment
Published in Expert Review of Medical Devices, 2022
Tim Balthazar, Johan Bennett, Tom Adriaenssens
The direct antiglobulin test (DAT) or direct Coombs test is used to detect antibodies or complement factors in RBCs of patients. It is used for diagnosing autoimmune hemolytic anemia (AIHA), where the test shows positivity with anti-IgG and anti-C3d. In case of hemolysis, AIHA should always be excluded with a DAT. In cases of mechanical hemolysis, the DAT is negative (11).