Toward Automatic Label-Free Whispering Gallery Modes Biodetection with a Quantum Dot-Coated Microsphere Population

Area of Science:

• Optics and Photonics
• Biotechnology
• Materials Science

Background:

• Traditional biosensing often requires precise calibration and fixed sensor positions.
• Surface-based methods can limit analyte-sensor interaction.
• Whispering gallery modes (WGMs) offer high sensitivity but often need specific coupling techniques.

Purpose of the Study:

• To develop a calibration-free biodetection method using freely moving microspheres.
• To enable remote sensing of analytes without reference measures.
• To enhance analyte-microsphere interaction for improved biodetection.

Main Methods:

• Utilized fluorophore-doped polystyrene microspheres as sensing resonators.
• Employed whispering gallery modes (WGMs) for detection.
• Developed algorithmic analysis to determine solution refractive index from unknown microsphere radii.
• Tested with alcohol-water solutions and bacterial spore suspensions.
• Explored quantum dot coatings for extended fluorescence range.

Main Results:

• Achieved 3 x 10(-4) precision on refractive index measurements for alcohol-water solutions.
• Demonstrated clear evidence of biodetection of bacterial spores via WGM analysis of microsphere populations.
• Successfully enabled remote sensing without evanescent light coupling.
• Presented preliminary results on quantum dot-coated microspheres for broader spectral detection.

Conclusions:

• The developed calibration-free WGM microsphere approach is effective for biodetection.
• Freely moving microspheres enhance analyte interaction and simplify sensing protocols.
• The method shows promise for sensitive and remote detection of biological targets.