Exploring the Potentiality of a SERS-Active pH Nano-Biosensor.

Area of Science:

• Analytical Chemistry
• Nanotechnology
• Biophysics

Background:

• Surface-Enhanced Raman Spectroscopy (SERS) offers high sensitivity for molecular detection.
• SERS-based nanosensors are valuable for localized pH measurements but require optimization for stability and calibration.
• Understanding the behavior of molecular probes on nanostructured surfaces is crucial for sensor development.

Purpose of the Study:

• To characterize and optimize a SERS-active pH nanosensor using gold nanoparticles and 4-mercaptobenzoic acid (4MBA).
• To investigate and improve the stability, calibration, and responsiveness of the nanosensor for accurate pH measurements.
• To demonstrate the nanosensor's capability in discriminating between normal and cancer cells via extracellular pH detection.

Main Methods:

• Conjugation of gold nanoparticles with the pH-sensitive molecular probe 4-mercaptobenzoic acid (4MBA).
• Optimization of synthesis and operating conditions to enhance sensor stability and pH responsiveness.
• Derivation of a calibration curve by analyzing the SERS spectrum's dependence on 4MBA protonation degree.
• Demonstration of nanosensor application in measuring extracellular pH of normal and cancer cells.

Main Results:

• A stable and highly responsive SERS-based pH nanosensor was developed.
• The nanosensor's working point, corresponding to the pKa of 4MBA on the nanoparticle surface, was determined to be pH 5.6.
• A shift in the pKa of 4MBA was observed on the nanostructured interface compared to its bulk form, enabling tunable sensitivity.
• The nanosensor successfully discriminated between normal and cancer cells by measuring their extracellular pH.

Conclusions:

• The study successfully developed and characterized a SERS-based pH nanosensor with tunable sensitivity.
• The findings highlight the potential of manipulating molecular probe confinement on nanostructured surfaces to optimize sensor performance.
• The developed nanosensor shows promise for applications in biological and medical diagnostics, particularly in distinguishing cell types based on pH differences.