Bulk Affinity Assays in Aptamer Selection: Challenges, Theory, and Workflow.

Area of Science:

• Biotechnology and Molecular Biology
• Biophysical Chemistry

Background:

• Oligonucleotide aptamer selection relies on iterative affinity isolation to enrich target-binding sequences.
• Assessing aptamer enrichment progress typically involves bulk affinity assays measuring the fraction of unbound library (R) or equilibrium dissociation constant (Kd).
• The theoretical suitability of R and Kd for these assays remains unexplored, leading to intuitive choices by researchers.

Purpose of the Study:

• To provide a theoretical foundation for bulk affinity assays in aptamer selection.
• To propose a scientifically justified and practical approach for bulk affinity assays.
• To address limitations of the fraction of unbound library (R) parameter.

Main Methods:

• Theoretical analysis of quantitative parameters used in bulk affinity assays.
• Postulation of the principle of superposition as a criterion for parameter suitability.
• Development and demonstration of an improved algorithm for R-based assays using simulations and experiments.

Main Results:

• The fraction of unbound library (R) satisfies the principle of superposition, unlike the equilibrium dissociation constant (Kd), indicating R's theoretical preference.
• A novel approach is proposed to overcome R's dependence on target concentration and narrow dynamic range.
• The proposed algorithm was successfully validated through computer simulations and experimental aptamer selection.

Conclusions:

• This work establishes a theoretical basis for bulk affinity assays, favoring the fraction of unbound library (R).
• The study introduces a practical, scientifically sound method for conducting bulk affinity assays, enhancing aptamer selection efficiency.
• The findings provide researchers with a robust framework for making informed decisions during aptamer discovery.