Critical coagulation concentration-based salt titration for visual quantification in gold nanoparticle-based...

Area of Science:

• Nanotechnology
• Analytical Chemistry
• Biomedical Engineering

Background:

• Gold nanoparticle (GNP)-based colorimetric biosensors typically require UV-vis spectrometry for accurate quantification.
• Gradual color shifts in GNP sensors correlate with target molecule concentration, necessitating analytical instruments.

Purpose of the Study:

• To develop a generic and simple quantification method for GNP-based colorimetric biosensors.
• To eliminate the need for analytical equipment in GNP biosensor quantification.
• To enable accurate quantification using visual inspection via salt titration.

Main Methods:

• A critical coagulation concentration (CCC)-based salt titration method was developed.
• The method involves stepwise addition of salt to a mixture of sample and GNPs until a rapid color change (red to blue) is observed.
• Quantification is based on the number of titration steps or final salt concentration (CCC) required for the color shift.

Main Results:

• The CCC-based salt titration method was successfully demonstrated with two existing GNP-based colorimetric biosensors.
• Visual quantification using the rapid color shift in salt titration showed comparable performance (sensitivity and accuracy) to spectrometer-based methods.
• The developed method eliminates the need for analytical equipment.

Conclusions:

• Salt titration provides a simple, equipment-free, and accurate quantification method for GNP-based colorimetric biosensors.
• This approach is highly suitable for point-of-care diagnostics and applications in low-resource settings.
• The CCC method offers a robust alternative to traditional spectroscopic quantification.