Calibration-Free Active Concentration Analysis via Global Kinetic Fitting
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Solution Overview
Problem
Existing methods for determining the active concentration of bioanalytes, such as proteins, often rely on calibration standards that may not be available or have uncertain activity, and do not distinguish between active and inactive molecules, which is a limitation in biotherapeutics development and production.
Innovation Solution
A method for calibration-free concentration analysis (CFCA) that involves contacting a liquid sample with a solid phase surface at multiple dilutions and varying flow rates, using a kinetic interaction model that includes a term for mass transport to determine the active analyte concentration, allowing for a global fit of binding rate data across different dilutions and flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration standards are used to determine active concentration, then measurement accuracy can be improved, but reliability deteriorates when standards are unavailable or have uncertain activity
Solution Approach 1:
The system uses the analyte's own diffusion properties to determine concentration without external calibration standards. The diffusion coefficient, which is an intrinsic property of the analyte, serves as the reference for calculating active concentration through the relationship between diffusion-limited binding rates and concentration.
Solution Approach 2:
The method changes the flow rate parameter to create different mass transport conditions. By measuring binding rates at multiple flow rates and extrapolating to infinite flow rate (where mass transport is no longer limiting), the system determines the true association rate constant and active concentration without needing calibration standards.
2Ease of operation
If total concentration is measured by UV or NIR absorption spectrometry, then ease of operation is improved, but the ability to distinguish active from inactive molecules deteriorates
Solution Approach 1:
The system introduces a specific ligand as an intermediary that selectively binds only to the active form of the analyte. This ligand acts as a mediator between the analyte and the detection system, enabling differentiation between active and inactive molecules through specific molecular recognition rather than general absorption properties.
Solution Approach 2:
The method replaces the optical absorption mechanism (UV/NIR spectrometry) with a biomolecular interaction mechanism (ligand binding). Instead of measuring general light absorption properties, the system measures the kinetics of specific ligand-analyte interactions, which inherently distinguish active from inactive molecules based on their binding capability.
3Productivity
If single dilution analysis is performed, then productivity is improved, but measurement precision and dynamic range deteriorate
Solution Approach 1:
The system merges multiple dilution analyses into a single global fit procedure. By simultaneously analyzing binding rate data from multiple dilutions with a unified kinetic model that accounts for mass transport effects, the method achieves both improved measurement precision through increased data robustness and maintained productivity through automated integrated analysis.
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
This approach enhances the robustness and dynamic range of active concentration determination, enabling accurate measurement without a calibration standard and distinguishing between active and inactive molecules, thus improving the reliability of bioanalyte concentration analysis.
Implementation Method 1
relies upon measurement of analyte binding at varying flow rates under conditions where the observed rate of binding is partially or completely limited by transport of analyte molecules to the sensor surface, i.e. partially or completely controlled by diffusion
Implementation Method 2
contacting a laminar flow of the sample with a solid phase surface or surface area supporting a ligand capable of specifically binding the analyte
Data Source
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AI summary
A method of determining active concentration of an analyte in a liquid sample, comprises the steps of: (a)contacting a laminar flow of the sample with a solid phase surface or surface area supporting a ligand capable of specifically binding the analyte at at least two different flow rates and under partially or completely mass transport limited conditions; (b)determining the initial binding rate dR/dt of analyte to the ligand at the ligand-supporting surface or surface area, and (c) fitting the initial binding rate data obtained in step (b) to a kinetic interaction model that includes a term for mass transport to obtain the active analyte concentration, wherein steps (a) and (b) are performed at a plurality of different dilutions of the liquid sample, and wherein in step (c) at least several of the plurality of dilutions of the liquid sample are in included in a global fit of initial binding rate data to the kinetic interaction model.