Slow Off-Rate Aptamer Selection for Stable Target Binding
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Solution Overview
Problem
Existing SELEX processes do not effectively discriminate between aptamers with fast association kinetics and slow dissociation kinetics, leading to a need for aptamers with improved slow off-rate properties for better binding affinity and functionality.
Innovation Solution
The development of slow off-rate aptamers through methods such as dilution and competitor addition, combined with modified nucleotides, to enrich for nucleic acid-target complexes with slow dissociation rates, and the incorporation of photoreactive functional groups for enhanced binding and crosslinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SELEX processes are used to select aptamers, then aptamers with high binding affinity can be obtained, but the off-rate (dissociation rate) remains fast and cannot be sufficiently reduced
Solution Approach 1:
The patent applies parameter changes by systematically varying selection conditions including incubation time, temperature, salt concentration, and competitor concentration to enrich for aptamers with slower off-rates. The selection process parameters are optimized to favor/aptamers that maintain binding over extended periods
Solution Approach 2:
The patent employs preliminary action by performing pre-enrichment steps and preliminary selections before the main selection process. Candidate pools are pre-conditioned and pre-screened to identify sequences with potential for slow off-rates before committing to full selection cycles
2Speed
If selection processes favor fast association kinetics, then binding speed is improved, but slow dissociation kinetics are not achieved
Solution Approach 1:
The patent applies dynamics by making the selection process adaptive and time-dependent. Different phases of selection emphasize different kinetic properties - early phases may favor association while later phases enrich for slow dissociation. The selection conditions are dynamically adjusted throughout the process
Solution Approach 2:
The patent employs periodic action through cyclic selection rounds with varying parameters. Each round alternates between conditions that favor different kinetic properties, allowing gradual enrichment of aptamers that satisfy both fast association and slow dissociation requirements over multiple cycles
3Ease of manufacture
If standard nucleic acid sequences are used, then aptamers can be generated, but binding stability and slow off-rate properties are insufficient
Solution Approach 1:
The patent applies composite materials by incorporating modified nucleotides (such as 2'-O-methyl RNA, phosphorothioate DNA, or other chemically modified bases) into the aptamer sequences. These composite nucleic acid structures combine the ease of synthesis with enhanced binding stability and slower off-rates
Solution Approach 2:
The patent applies local quality by introducing specific modifications at particular positions within the aptamer sequence rather than uniformly throughout. Strategic placement of modified nucleotides at key binding positions enhances local interaction stability without compromising overall sequence synthesizability
4Measurement precision
If conventional aptamers are used in diagnostic applications, then detection is possible, but signal-to-noise ratios are reduced due to fast washout rates
Solution Approach 1:
The patent applies this principle in reverse by creating long-retaining aptamers that function as persistent detection elements. The slow off-rate aptamers maintain binding through washout phases, effectively extending the functional lifetime of the detection signal and reducing background noise
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting aptamers exhibit improved binding specificity and stability, enabling applications in diagnostics, imaging, and therapeutic contexts with enhanced signal-to-noise ratios and reduced washout rates.
Implementation Method 1
The resulting photoreactive aptamers are referred to as photocrosslinking aptamers or photoaptamers
Data Source
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AI summary
The present disclosure describes improved SELEX methods for producing aptamers that are capable of binding to target molecules and improved photoSELEX methods for producing photoreactive aptamers that are capable of both binding and covalently cross linking to target molecules. Specifically, the present disclosure describes methods for producing aptamers and photoaptamers having slower dissociation rate constants than are obtained using prior SELEX and photoSELEX methods. The disclosure further describes aptamers and photoaptamers having slower dissociation rate constants than those obtained using prior methods. In addition, the disclosure describes aptamer constructs that include a variety of functionalities, including a cleavable element, a detection element, and a capture or immobilization element.