Microfluidic Sensor for Mitochondrial Membrane Potential
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Solution Overview
Problem
Current methods for measuring mitochondrial membrane potential require large sample sizes, limiting the evaluation of mitochondrial function in clinical biopsy samples and certain cell lines, and are not suitable for smaller sample quantities.
Innovation Solution
A microfluidic sensor device with a substrate having a reference electrode and a working electrode, separated by a TPP+ ion-selective membrane, allowing for the measurement of mitochondrial membrane potential using nanogram quantities of mitochondria, with the device comprising multiple layers of PDMS and ion-selective membranes for precise voltage measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional methods (fluorescent probes, electrochemical methods with large volume chambers) are used to measure mitochondrial membrane potential, then measurement capability is achieved, but large sample sizes are required which limits application to clinical biopsy samples and certain cell lines
Solution Approach 1:
The device segments the measurement chamber into multiple compartments separated by ion-selective membranes, allowing the working electrode to measure TPP+ concentration in a small volume (nanogram quantities of mitochondria) while the reference electrode is isolated in a separate compartment. This segmentation enables precise measurement with minimal sample consumption.
Solution Approach 2:
The patent uses TPP+ (tetraphenylphosphonium) ions as an intermediary substance to indirectly measure mitochondrial membrane potential. TPP+ ions diffuse across the mitochondrial membrane according to the Nernst equation, and their concentration ratio is used to calculate ΔΨm. This intermediary approach enables measurement with small sample sizes.
2Measurement precision
If TPP+ selective electrode technology is used to measure mitochondrial membrane potential, then measurement sensitivity is improved, but device complexity increases due to multiple layers of PDMS and ion-selective membranes
Solution Approach 1:
The device employs a nested structure where multiple layers of PDMS membranes and ion-selective membranes are stacked together. The working electrode is positioned behind a first PDMS layer with a TPP+ ion-selective membrane, while the reference electrode is positioned behind a second PDMS layer with a protective membrane. This nested arrangement achieves high measurement sensitivity while maintaining a compact, integrated structure.
Solution Approach 2:
The patent uses thin films of PDMS (polydimethylsiloxane) and ion-selective membranes as flexible barriers to separate the electrode chambers. These thin film structures provide the necessary ion selectivity and physical separation while maintaining device compactness and reducing overall complexity compared to rigid multi-component systems.
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 the determination of mitochondrial membrane potential with significantly reduced sample sizes, facilitating the analysis of mitochondrial bioenergetics in smaller samples and providing a more efficient and accurate method for clinical and research applications.
Implementation Method 1
the sample chamber separated from the first solution holding region by a polyvinyl chloride (PVC) protective member, the sample chamber separated from the second solution holding region by a TPP+ ion selective membrane
Implementation Method 2
By measuring the concentration of TPP outside the mitochondria (referred to as '[TTP]out') using electrochemical ion selective electrode technology one can infer the amount of cation taken up into the mitochondria, (hence termed '[TPP+]in') to determine the membrane potential
Data Source
AI summary
A microfluidic sensor device includes a substrate having patterned thereon at least one Ag/AgCl electrode (working electrode) and an inner chamber overlying the at least one Ag/AgCl electrode. The device includes an ion selective permeable membrane permeable to TPP+ disposed on one side of the first chamber and a sensing chamber overlying the ion selective permeable membrane. A separate reference electrode is inserted into the sensing chamber. The working electrode and reference electrode are coupled to a voltmeter to measure voltage. This voltage can then be translated into a TPP+ concentration which is used to determine the mitochondrial membrane potential (ΔΨm).