Optical detection enhancement in porous volumetric microfluidic capture elements using refractive index matching...

Area of Science:

• Analytical Chemistry
• Microfluidics
• Optical Sensing

Background:

• Porous capture elements offer higher reaction site density and shorter diffusion paths in microfluidic sensors.
• Refractive index mismatches in porous matrices cause light scattering, reducing optical detection sensitivity.

Purpose of the Study:

• To demonstrate index-matching fluid perfusion for minimizing light scattering in porous microfluidic sensors.
• To enhance optical signal detection by enabling full probing of the porous capture element volume.

Main Methods:

• Perfusion of index-matching fluid within porous polymer monoliths and packed glass beads.
• Optical signal enhancement evaluated using fluorescence and absorbance detection methods.
• Assessed signal improvement for direct fluorescence measurement and a direct immunoassay.

Main Results:

• Minimized light scattering by using index-matching fluid.
• Achieved 3.5× fluorescence signal enhancement for directly attached compounds.
• Improved immunoassay signal by up to 2.6×.
• Demonstrated a detection limit of 0.1 ng mL(-1) human IgG with silver enhancement.

Conclusions:

• Index-matching fluid perfusion is a simple and effective method to enhance optical sensitivity in porous microfluidic sensors.
• Enables realization of the full benefits of porous detection elements in miniaturized analytical systems.
• Broad applicability for various optical detection assays.