Multi-Wavelength Optical pH Measurement for Cell Culture
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Solution Overview
Problem
Existing methods for measuring the pH of cell culture solutions, such as those containing fetal bovine serum (FBS), face errors due to visual checks and contamination risks with pH electrodes, and fail to accurately account for unknown FBS concentrations, leading to incorrect pH readings.
Innovation Solution
A pH measuring method using multiple light beams of specific wavelengths to illuminate the solution, measuring absorbances, and calculating pH based on these measurements, accounting for the absorbance characteristics of both phenol red and FBS, with expressions that include absorption coefficients and concentration calculations to correct for FBS influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If visual check of phenol red color change is used to measure pH, then the measurement can be performed without specialized equipment, but measurement precision deteriorates due to errors and interference from serum yellow coloration
Solution Approach 1:
The patent replaces the visual/mechanical checking method with an optical measurement system using light emitting elements and light receiving elements. This substitution enables objective, quantitative pH measurement by detecting absorbance changes at specific wavelengths, eliminating both the simplicity of visual inspection and its associated errors and color interference issues.
2Measurement precision
If pH electrodes are immersed in cell culture solution for measurement, then measurement precision can be improved with direct electrical measurement, but reliability deteriorates due to contamination risks from insufficient sterilization
Solution Approach 1:
The patent replaces the electrical measurement system (pH electrodes requiring sterilization) with an optical measurement system using light emitting and light receiving elements. This substitution maintains measurement precision while eliminating the sterilization requirements and contamination risks associated with immersing physical electrodes in the cell culture solution.
3Device complexity
If conventional optical measurement at single wavelength is used, then device complexity can be reduced, but measurement precision deteriorates because FBS absorbance cannot be distinguished from phenol red absorbance
Solution Approach 1:
The patent segments the optical measurement into multiple discrete wavelength channels (411 nm for FBS, 430/560 nm for phenol red peaks, and reference wavelengths). By measuring absorbance at multiple separated wavelengths and processing the data separately, the system can distinguish and subtract FBS absorbance from phenol red absorbance, achieving accurate pH measurement while maintaining reasonable device complexity.
Solution Approach 2:
The patent extends the measurement from a single wavelength dimension to multiple wavelength dimensions. By adding the wavelength dimension and measuring absorbance spectra across multiple discrete wavelengths, the system creates an additional degree of freedom that enables separation of the overlapping absorbance signals from FBS and phenol red through spectral analysis.
4Measurement precision
If multiple light beams of different wavelengths are used to illuminate the solution, then measurement precision can be improved by accounting for FBS absorbance, but device complexity increases due to multiple light emitting elements and filtering requirements
Solution Approach 1:
The patent segments the optical system into distinct wavelength-specific components: light emitting elements for specific wavelengths (411 nm, 430 nm, 560 nm, and reference wavelengths), corresponding light receiving elements, and filters. This segmentation allows each component to be optimized for its specific wavelength range, achieving high measurement precision while keeping the overall device complexity manageable through modular design.
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 accurate pH measurement in cell culture solutions regardless of FBS concentration, reducing errors and contamination risks, and providing reliable pH readings within the suitable range for cell proliferation.
Implementation Method 1
measuring absorbances at the wavelengths of the received transmitted or reflected light beams of the first to fourth light beams respectively
Data Source
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AI summary
A pH measuring method includes: illuminating a medium solution, which includes: a first material; and a second material, with a plurality of light beams, which includes: a first light beam, a wavelength of which corresponds to a first absorption peak; a second light beam, a wavelength of which corresponds to a second absorption peak or a second convergence point; a third light beam, a wavelength of which corresponds to a third absorption peak or a third convergence point; and a fourth light beam, a wavelength of the fourth light beam at which an absorbance of at least one of the first and second materials is converged irrespective of a pH; receiving transmitted or reflected light beams of the first to fourth light beams; measuring absorbances at the wavelengths of the received light beams respectively; and calculating a pH of the medium solution based on the absorbances.