Single electrode biosensor for simultaneous determination of interferon gamma and lysozyme

Aptamer-Based Electrochemical Sensing of Lysozyme

“…To ensure that K d is not affected upon aptamer immobilization, the effective dissociation constant of the immobilized aptamer-lysozyme complex should remain constant. For instance, in [90], for the immobilized aptamer, a K d value of 30 nM was measured, which compared well with that measured in solution, namely 31 nM [68].…”

“…Provided that their oxidation/reduction potentials are separated enough so that their electrochemical signals can be resolved, several electroactive labels have been used to detect multiple proteins with the same sensor. For instance, aptasensors for dual detection of lysozyme and interferon gamma [90] or thrombin [89,94] have been developed based on this principle. [63]; (C) sandwich assay for lysozyme analysis using amplification with a lysozyme antibody labeled with alkaline phosphatase [44]; (D) competitive assay where free lysozyme in solution displaces quantum dot-tagged lysozyme, previously bound to surfaceimmobilized aptamer (e.g., as illustrated in [94]).…”

“…The gain in sensitivity comes with a cost in complexity, price per assay and inconvenience associated with limited enzyme stability; these should be all considered before choosing the "right" aptasensor design for a particular application. resulting in a conformational change of methylene blue-tagged DNA into a hairpin structure; this brings methylene blue closer to the electrode surface, leading to an increase of its signal (signal-on sensor) [90] 4. displacement of LBA from its complex with DNA upon lysozyme addition (signal-off sensor) [46,62,95] 5. electrochemical stripping of lysozyme/quantum-dots complex [94] Although simple, practical and label-free, these aptasensors lack the required sensitivity for more demanding applications, such as the detection of lysozyme in biological samples or of trace amounts of lysozyme in wine. Moving forward from the above direct assay, a sandwich between the surface linked aptamer, the captured lysozyme and a biotinylated anti-lysozyme antibody has been recently proposed to enhance the sensitivity of the sensor ( Figure 4C) [44].…”

“…The sensing principles applied rely on: displacement of LBA from its methylene blue-tagged DNA complex in the presence of lysozyme, resulting in a conformational change of methylene blue-tagged DNA into a hairpin structure; this brings methylene blue closer to the electrode surface, leading to an increase of its signal (signal-on sensor) [90] 4. displacement of LBA from its complex with DNA upon lysozyme addition (signal-off sensor) [ desorption of lysozyme aptamer from rGO/Orange II-modified GCE, reversing the blocking effect and reestablishing efficient electron transfer from graphene-adsorbed aromatic dye Orange II [85] Competitive detection schemes are typically used with regenerable sensors, where in order to revert to the characteristics of the original interface, the aptasensor needs simply to be re-incubated in fresh aptamer solution at the end of each measurement [62,89]. An ingenious detection strategy for multiple protein detection relied on immobilization of dabcyl-labeled-aptamer-modified metal nanoparticles (DLAPs) on a β-cyclodextrin-modified electrode by host-guest affinity [89].…”

“…All multi-analyte detection schemes developed so far that include lysozyme detection are based on competitive testing [89,90,94,95]. One of the most interesting approaches makes use simultaneously of both a "signal-on" and a "signal-off' mechanism for dual detection of lysozyme and interferon gamma (IFN-γ) [90]. The aptasensor is intended as an analytical tool in the diagnosis of acute leukemia and is built by immobilizing on a Au electrode two reporter DNA probes, one labeled with ferrocene (Fc) and the other one with methylene blue (MB).…”