Microfluidic Protein Binding Assays Using Split Fluorescent Tags
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Solution Overview
Problem
Existing methods for real-time detection of proteins in cell-free protein synthesis reactions on microfluidic devices face challenges due to high concentrations of other proteins and biomolecules, leading to non-specific detection issues, and prolonged luminescent complementation approaches are limited by O2 consumption and substrate exhaustion.
Innovation Solution
A method for detecting protein binding using fluorescent protein sub-components on a digital microfluidic device, where expressed proteins and binding partners form a fully assembled fluorescent protein, allowing for real-time detection through fluorescent signal measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard protein staining methods (e.g., Coomassie Brilliant Blue, SYPRO Ruby) are used for real-time detection, then protein detection is achieved, but non-specific detection occurs due to high concentrations of other proteins and biomolecules
Solution Approach 1:
The fluorescent protein is divided into two separate sub-components (first and second sub-components) that are incorporated into different fusion proteins. These sub-components only assemble into a functional fluorescent protein when the two fusion proteins bind together, providing specific detection signal. This segmentation prevents non-specific detection because the fluorescent signal only forms when both specific binding partners are present.
Solution Approach 2:
The first and second sub-components of the fluorescent protein act as intermediaries that mediate the detection process. These sub-components are incorporated into fusion proteins but remain non-fluorescent until they assemble together upon specific binding of the fusion proteins. The assembly of sub-components into functional fluorescent protein serves as a specific indicator of binding, eliminating non-specific detection interference.
2Measurement precision
If luminescent complementation approaches are used for real-time detection, then detection is achieved, but detection duration is limited due to O2 consumption and substrate exhaustion
Solution Approach 1:
The invention changes the detection parameter from luminescence (which consumes O2 and substrate) to fluorescence (which does not). The fluorescent protein system allows prolonged real-time detection because fluorescent proteins are stable, do not consume oxygen or substrates during detection, and can maintain fluorescence signal for extended periods without exhaustion, overcoming the duration limitations of luminescent systems.
3Measurement precision
If fluorescent protein tags (e.g., GFP) are used for protein expression monitoring, then real-time detection is achieved, but the total size of the protein of interest significantly increases
Solution Approach 1:
The fluorescent protein is segmented into two sub-components that are distributed between two separate fusion proteins. Each fusion protein contains only a portion of the fluorescent protein (either the first or second sub-component), so the size addition to each protein of interest is minimal compared to using a complete fluorescent protein tag. The segmentation reduces the burden on individual proteins while enabling detection through assembly.
4Measurement precision
If immunostaining or affinity-based purification followed by non-specific protein staining is used, then specific protein detection is achieved, but significant washing on solid support must be performed to prevent background interference
Solution Approach 1:
The invention replaces the mechanical washing system (required in immunostaining to remove unbound antibodies and reduce background) with a biochemical assembly system. The fluorescent signal forms automatically through the assembly of fluorescent protein sub-components when fusion proteins bind specifically, eliminating the need for washing steps. The specific binding event itself triggers the fluorescent signal formation, substituting mechanical separation with biochemical specificity.
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
Enables efficient and prolonged real-time detection of protein binding by forming a fluorescent signal upon interaction, overcoming non-specific detection and O2 limitations in microfluidic environments.
Implementation Method 1
the sub-components form a fluorescent protein... determining the level of fluorescent signal within the droplets
Data Source
AI summary
Provided herein are methods, and compositions for the synthesis of proteins. The methods are applicable to synthesis of proteins on a microfluidic device and assays using the expressed proteins.