Optimization of SERS tag intensity, binding footprint, and emittance

Area of Science:

• Nanotechnology
• Biomolecular assays
• Spectroscopy

Background:

• Nanoparticle surface enhanced Raman scattering (SERS) tags are promising labels for biomolecular assays.
• A lack of standardized methods hinders the comparison of SERS tag brightness across studies and labs.

Purpose of the Study:

• To develop and validate a standardized approach for evaluating SERS tag brightness.
• To compare the brightness and performance of different SERS tag compositions.

Main Methods:

• A novel method was developed using beads with known binding capacities to evaluate SERS tags.
• Key metrics include average intensity, binding footprint, and size-normalized intensity (emittance).
• Four different SERS tag compositions were tested, including aggregated gold nanorods, monodisperse gold nanorods, silver-coated gold nanorods, and silver plates.

Main Results:

• Aggregated gold nanorods yielded brighter SERS tags (2-4x) but were larger, potentially limiting binding.
• Silver-coated gold nanorod SERS tags showed 2-3x greater size-normalized intensity compared to gold nanorod tags.
• Silver plate SERS tags demonstrated bright signals with a small footprint.

Conclusions:

• The developed method provides a generalizable approach for SERS tag brightness evaluation.
• Silver-coated gold nanorod SERS tags offer improved performance for SERS-based imaging and flow cytometry.
• The method is suitable for inter-laboratory comparisons using standard reagents and instruments.