First-passage time analysis of diffusion-controlled reactions in single-molecule detection

Area of Science:

• Biosensing
• Analytical Chemistry
• Physical Chemistry

Background:

• Single-molecule detection (SMD) aims for ultimate limit-of-detection (LOD) in biosensing.
• Molecule diffusion, capturing, and identification dynamics critically impact SMD efficiency and accuracy.
• Understanding these dynamics is crucial for advancing biosensor technology.

Purpose of the Study:

• Investigate diffusion-controlled reaction processes in SMD using the first-passage time method.
• Analyze the influence of detection conditions on incubation time and coefficient of variation (CV).
• Compare the efficiency of different molecule capturing strategies in SMD.

Main Methods:

• Applied the first-passage time method to model diffusion-controlled reactions in SMD.
• Analyzed three molecule capturing strategies: solid-phase, magnetic bead (MB) liquid-phase, and direct fluorescence pair liquid-phase labeling.
• Evaluated the impact of reaction chamber size and reaction time on incubation time and CV.

Main Results:

• A finite average reaction time exists for all three capturing strategies within a finite reaction chamber.
• Liquid-phase capturing strategies (MB and fluorescence pair) are generally more efficient than solid-phase capturing.
• Coefficient of variation (CV) can be estimated from first-passage time, and reduction is achievable with extended reaction times.

Conclusions:

• Theoretical framework supports SMD design for optimized measurement time and CV.
• Zeptomolar detection requires advanced strategies like high-diffusion-rate liquid-phase labels or larger sensing areas.
• Liquid-phase strategies offer advantages in efficiency for single-molecule detection.