Enzyme-free electrochemical immunosensor based on methylene blue and the electro-oxidation of hydrazine on Pt nanoparticles

Abstract

Enzyme-free electrochemical sensors enable rapid, high sensitivity measurements without the limitations associated with enzyme reporters. However, the performance of non-enzymatic electrochemical sensors tends to suffer from slow electrode kinetics and poor signal stability. We report a new enzyme-free electrochemical immunosensor based on a unique competitive detection scheme using methylene blue (MB), hydrazine and platinum nanoparticles (Pt NPs). This scheme is coupled with a robust immunosandwich format employing a MB-labelled detection antibody as a non-enzymatic reporter. In the presence of the target antigen, surface-immobilized MB consumes interfacial hydrazine thereby diminishing the electro-oxidation of hydrazine on Pt NPs. Thus, the concentration of the antigen is directly proportional to the reduction in the electrochemical signal. For proof-of-concept, this sensor was used to detect Plasmodium falciparum histidine-rich protein 2 (PfHRP2), an important malaria biomarker, in unadulterated human saliva samples. Chronocoulometric measurements showed that this platform exhibits pM-range sensitivity, high specificity and good reproducibility, making it well suited for many biosensing applications including noninvasive diagnostic testing.

Development of Electrochemical Impedance Spectroscopy Based Malaria Aptasensor Using HRP‐II as Target Biomarker

“…There has been report on the aptamer based detection of malaria using Plasmodium lactate dehydrogenase as target biomarker ; whereas, similar report for detection of HRP‐II using aptamers as biorecognition element is not yet widely known. A plethora of HRP‐II based sensors are available, which however, rely mostly on antibody and chemical techniques as the sensing systems. Our underlying motivation for substituting antibody with other recognition elements in the sensor platforms for malaria detection has already been explained elsewhere.…”

“…The developed aptasensor was found to be suitable for an impedimetric measurement of signal generated from its binding with the target HRP‐II protein as no additional label is essential for this electrochemical technique. Notably, EIS is known as highly sensitive signal transduction technique that has already been validated for aptamer based detection of other protein–based antigens . The Faradic impedance technique we used here could detect HRP‐II down to a picomolar level which can detect asymptomatic malaria patients.…”

Saliva, a Magic Biofluid Available for Multilevel Assessment and a Mirror of General Health—A Systematic Review

“…Other biochemical sensors for glucose included spectrophotometric detection using a low-cost colorimeter (Dominguez et al 2017) [21]; using a colloidal AgNPs/MoS2-based nonenzymatic glucose biosensor (Anderson et al 2017) [22]; tested on both saliva and sweat with similar performances; using randomly oriented CuO nanowire networks (Bell et al 2017) [23]; using CuO-modified screen-printed carbon electrodes (SPCE; Velmurugan et al 2017) [24]; using molecularly imprinted polymer binding on a conducting polymer layer (Kim et al 2017) [25]; tested on both saliva and blood, methylene blue, hydrazine and platinum nanoparticles (Dutta et al 2017); and using paper-based sensors (Santana-Jiménez et al 2018) [26,27], standing to prove a high interest in the development of these medical devices.…”

Ultrasensitive Bioaffinity Electrochemical Sensors: Advances and New Perspectives

“…Another enzyme-free electrochemical immunosensor was constructed based on methylene blue and the electrooxidation of hydrazine on Pt nanoparticles [44]. The strategy of this immunosensor is based on the competitive detection scheme using methylene blue (MB), hydrazine and platinum nanoparticles (Pt NPs).…”

“…Reproduced from[44] with permission from Elsevier. Photographs of solutions containing (d) 10 mM MB and 5 mM hydrazine in 1 mL of PBS, (e) 10 mM MB and 0.001 % (w/v) Pt NPs in 1 mL of PBS, (f) 10 mM MB, 0.001 % (w/v) Pt NPs and 5 mM hydrazine in 1 mL of PBS, and (g) 10 mM MB, 0.001 % (w/v) Pt NPs and 5 mM hydrazine in 1 mL of PBS after 15 min in air.…”