Chip-Scale Aptamer Sandwich Assay Using Optical Waveguide-Assisted Surface-Enhanced Raman Spectroscopy.

Area of Science:

• Nanophotonics and Spectroscopy
• Biosensing and Diagnostics
• Materials Science

Background:

• Surface-enhanced Raman spectroscopy (SERS) offers high sensitivity for molecular detection.
• Integrating SERS with optical waveguides can enhance signal excitation and confinement.
• Miniaturized sensing platforms are crucial for point-of-care diagnostics.

Purpose of the Study:

• To demonstrate a chip-scale optical waveguide-assisted SERS device.
• To investigate the excitation of Raman reporter molecules using waveguide evanescent fields.
• To develop a miniaturized platform for detecting small molecules and large proteins.

Main Methods:

• Fabrication of chip-scale optical waveguides.
• Integration of nanoparticles (NPs) for plasmonic enhancement.
• Finite difference method (FDM) for optical mode and field enhancement calculations.
• Experimental characterization using various Raman reporters (e.g., 4-MBA, DTNB, MGITC).
• Application of an aptamer sandwich assay for biomarker detection (cardiac troponin I).

Main Results:

• Efficient excitation of Raman signals via waveguide evanescent field.
• Significant Raman signal enhancement due to NP plasmon resonance.
• Achieved a low detection limit of 1 nM for small molecules.
• Successful detection of cardiac troponin I (cTnI) using the aptamer assay.
• Demonstrated potential for multiplexed detection.

Conclusions:

• Optical waveguide-integrated SERS provides a highly sensitive and miniaturized sensing platform.
• The device is suitable for detecting both small molecules and large proteins.
• This technology holds promise for developing advanced diagnostic tools for clinical applications.