Immunoassay employing surface-enhanced Raman spectroscopy.

Area of Science:

• Analytical Chemistry
• Biochemistry
• Spectroscopy

Background:

• Surface-enhanced Raman scattering (SERS) amplifies Raman signals of molecules near nanostructured metal surfaces.
• SERS has shown potential for detecting biomolecular binding, such as antigen-antibody interactions.
• Resonance enhancement can further improve SERS sensitivity for specific dye molecules.

Purpose of the Study:

• To investigate the utility of surface-enhanced resonance Raman scattering (SERRS) for biomolecular detection.
• To develop a sensitive and rapid immunoassay for human thyroid stimulating hormone (TSH).
• To explore SERRS as a readout for a one-step, no-wash immunoassay system.

Main Methods:

• Conjugation of nitro groups to bovine serum albumin to enhance SERS activity.
• Utilizing avidin-coated silver films to capture a resonance dye (HABA) for SERRS measurement.
• Covalent attachment of a resonance dye (DAB) to an anti-TSH antibody for a sandwich immunoassay.
• Measuring TSH concentration using SERRS signal intensity in a sandwich immunoassay format.

Main Results:

• Nitro group conjugation enhanced SERS activity by 10^4-fold.
• A logarithmic relationship was observed between HABA concentration and SERRS peak intensity (10^-8 to 10^-5 M).
• A linear relationship was found between TSH concentration and SERRS signal intensity (4 to 60 microIU/ml).

Conclusions:

• SERRS is a viable technique for sensitive biomolecular detection.
• The developed sandwich immunoassay for TSH is effective and rapid.
• SERRS has significant potential as a readout for one-step, no-wash immunoassay systems.