Polymer Microspheres Copolymerized with Deep Red Fluorescent Molecules as a Label for Lateral Flow...

Area of Science:

• Materials Science
• Biotechnology
• Analytical Chemistry

Background:

• Nitrocellulose membranes in lateral flow immunochromatography (LFIA) can cause background fluorescence, limiting detection sensitivity.
• Fluorescent microspheres are crucial for LFIA but require strategies to mitigate interference.
• Developing novel fluorescent labels is key to advancing sensitive and accurate biological detection.

Purpose of the Study:

• To synthesize novel rhodamine-based dye molecules (RB2) with extended π-conjugation and asymmetric structures.
• To create carboxyl group-functionalized fluorescent microspheres using RB2 via soap-free emulsion polymerization.
• To evaluate the performance of these microspheres as fluorescent labels in LFIA for sensitive biological detection.

Main Methods:

• Synthesis of RB2 dye molecules with enhanced photoluminescence quantum yield (PLQY).
• Two-step soap-free emulsion polymerization to prepare carboxyl-functionalized fluorescent microspheres.
• Characterization using SEM, TEM, DLS, FTIR, UV-Vis, and fluorescence spectrophotometry.
• Application of microspheres in a lateral flow immunoassay for SARS-CoV-2 N protein detection.

Main Results:

• RB2 dye achieved an absolute PLQY of 30.01% in ethanol.
• Successfully synthesized stable, well-dispersed fluorescent microspheres with high red fluorescence intensity (λabs ∼ 610 nm, λem ∼ 660 nm).
• Demonstrated successful copolymerization of RB2 into the microspheres.
• Achieved a low detection limit of 2.5 pg/mL for SARS-CoV-2 N protein in LFIA, with linearity from 2.5 pg/mL to 10 ng/mL.

Conclusions:

• The developed RB2-based fluorescent microspheres effectively function as labels in LFIA.
• These microspheres overcome background fluorescence interference, significantly improving detection sensitivity.
• The findings support the use of these novel fluorescent microspheres for advanced biological detection applications.