Aptamer-based potentiometric measurements of proteins using ion-selective microelectrodes

Area of Science:

• Analytical Chemistry
• Biotechnology
• Biosensors

Background:

• Aptamer-based assays offer high specificity for biomolecule detection.
• Potentiometric methods provide label-free detection capabilities.
• Sensitive protein quantification is crucial for diagnostics and research.

Purpose of the Study:

• To develop and validate the first aptamer-based potentiometric sandwich assay for protein detection.
• To utilize cadmium sulfide (CdS) quantum dots as labels for secondary aptamers.
• To establish a novel solid-contact cadmium ion-selective electrode for sensitive measurements.

Main Methods:

• A potentiometric sandwich assay format was designed using specific aptamers.
• Cadmium sulfide (CdS) quantum dots were employed as labels for the secondary aptamer.
• A novel solid-contact Cd2+-selective polymer membrane electrode was developed and used for detection.
• The CdS labels were dissolved using hydrogen peroxide to release Cd2+ ions for potentiometric measurement.
• A calcium-selective electrode served as a pseudoreference electrode.

Main Results:

• The developed electrode achieved low cadmium ion detection limits: 100 pM in 100 mL and 1 nM in 200 µL microwells.
• The assay successfully measured thrombin in 200 µL samples with a lower detection limit of 0.14 nM (28 fmol).
• The aptamer-based potentiometric assay demonstrated high sensitivity for protein quantification.

Conclusions:

• The study presents the first aptamer-based potentiometric sandwich assay for protein detection.
• The novel solid-contact Cd2+-selective electrode enables sensitive quantification of proteins at very low concentrations.
• This method shows significant potential for protein analysis in small-volume biological samples.