Custom-made Microdialysis Probe Design
July 21st, 2015
Microdialysis is a commonly used technique in neuroscience research. Therefore commercial probes are in great demand.In this work a probe assembly is explained in detail to build a reliable, concentric, custom-made microdialysis probe for less than $10.
The overall goal of this procedure is to describe the manufacturer of a custom made microdialysis probe. This is accomplished by first cutting polytetrafluoroethylene tubing and fused silica into the correct dimensions. The second step is to insert the fused silica into the tubing using a cannula as guidance.
Next, a dialysis membrane is positioned over the fused silica. The final step is to pull the metal sleeve onto the remaining part of the fused silica and to use epoxy to close off joints and to ensure an exchange length of two millimeters. Ultimately, the instructions in this video will show how to build a sturdy and reliable custom-made microdialysis probe as an alternative to a commercial probe, which can accurately measure in vitro recovery of neuropeptides and small molecules.
The main advantage of this technique is that this microdialysis probe assembly presented in detail can be adapted to any application and can be manufactured for less than 10. To begin, cut a piece of 1.6 millimeter thick polytetrafluoroethylene tubing with a 350 micron inner diameter into 2.5 centimeter long sections. Cut one end of the section at a 45 degree angle in order to make it easier to connect the outlet tubing.
Next, use sandpaper to roughen the outer surface of the PTFE tubing to promote adhesion of an epoxy glue. Cut a section of fused silica into a 2.25 centimeter long piece. Insert a 30 gauge needle into the hollow PTFE fiber one centimeter from the flat end.
Bend the PTFE and pierce the sheath at the bend. Insert the fused silica into the PTFE tubing using the needle cannula as guidance. Then gently remove the needle cannula and position the fused silica so that five millimeters project out the flat end of the PTFE tubing.
Use a drop of cyanoacrylate glue to secure the fused silica in place at the puncture site and allow it to harden overnight. Prepare the epoxy glue by adding 30 parts of yellow hardener to 70 parts of black epoxy glue and mixing gently. Then pull a 30 kilodalton cutoff polysulfone dialysis membrane with an inner diameter of 210 microns and an outer diameter of 245 microns.
Carefully over the fused silica. Pull the membrane into the PTFE tubing and adjust the membrane to 5.5 millimeters using a sharp scalpel. Mark a point on the membrane with a fine pen to define the exchange length of two millimeters from the end of the membrane.
Then use a fine needle to apply a small amount of epoxy glue to cover the tip of the membrane. Next, use epoxy glue to close off the joint between the dialysis membrane and the PTFE fiber. Now go back and add enough epoxy glue onto the membrane up to the marking point.
To ensure a diffusion exchange length of only two millimeters, allow the epoxy glue to harden overnight. Use a pair of pliers to carefully break off one centimeter pieces of a 25 gauge needle in order to create metal sleeves. Then pull the metal sleeve onto the remaining part of the fused silica and use the remaining epoxy glue to seal the joint between the metal sleeve and the PTFE tubing.
The metal sleeve later enables the connection of the inlet tubing with a microdialysis probe. Finally, apply hot glue around the bifurcation of the probe for additional fixation and stabilization of the device. This schematic shows a closeup of the inner workings of the microdialysis probe.
Two millimeters of the polysulfone dialysis membrane is exposed at the end of the probe, which allows for the recovery of small molecular weight metabolites such as glucose a TP, and acetylcholine. The ability of the probe to recover small, low molecular weight molecules such as glucose, lactate, acetylcholine, and a TP in vitro is shown here. The percent recovery is much higher with these molecules, which are around 500 Daltons than larger molecules such as angiotensin two, substance p, and somatostatin, which are above 1000 Daltons.
After watching this video, you should have a good understanding how to build sturdy and reliable microdialysis probes as an alternative to commercial ones.
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Overview
This article describes the process of manufacturing a custom-made microdialysis probe, which is a cost-effective alternative to commercial probes. The procedure outlines the steps necessary to create a reliable probe capable of measuring neuropeptides and small molecules in vitro.
Key Study Components
Area of Science
- Neuroscience
- Microdialysis Techniques
- Probe Manufacturing
Background
- Microdialysis is widely used in neuroscience research.
- There is a high demand for reliable microdialysis probes.
- Custom-made probes can be more cost-effective than commercial options.
- Understanding the construction of these probes can enhance research capabilities.
Purpose of Study
- To provide detailed instructions for building a custom microdialysis probe.
- To offer an affordable alternative to commercial probes.
- To ensure accurate measurement of neuropeptides and small molecules.
Methods Used
- Cutting polytetrafluoroethylene tubing and fused silica to specific dimensions.
- Inserting fused silica into the tubing with a cannula for guidance.
- Positioning a dialysis membrane over the fused silica.
- Securing the assembly with a metal sleeve and epoxy to ensure durability.
Main Results
- A reliable and sturdy custom-made microdialysis probe can be constructed.
- The probe is capable of accurately measuring in vitro recovery of neuropeptides.
- The total cost of the probe assembly is less than $10.
Conclusions
- Custom microdialysis probes are a viable alternative to commercial options.
- Detailed instructions can empower researchers to create their own probes.
- This method can enhance the accessibility of microdialysis techniques in neuroscience research.
Frequently Asked Questions
Executive Industry Relevance
Custom microdialysis probe fabrication offers a cost-effective solution for neuroscience research, enabling precise monitoring of neurochemical dynamics in cerebrospinal fluid. By reducing probe expenses below $10, this method enhances accessibility for public institutions and supports scalable deployment across preclinical studies. The approach facilitates target validation and mechanistic de-risking by providing reliable recovery data for small molecules and neuropeptides, informing go/no-go decisions in early discovery pipelines.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of therapeutic hypotheses through quantitative recovery of glucose, lactate, acetylcholine, ATP, and neuropeptides in the 100-1,600 Da range.
- Operational Value: Supports biological de-risking by delivering reproducible in vitro recovery metrics (~20% for small molecules, 2-6% for neuropeptides) to clarify target engagement and pathway modulation.
- Predictive Value: Generates mechanistic insights that improve portfolio triage by differentiating compound effects based on molecular weight and physicochemical properties.
Screening & Assay Development
- Scientific Value: Prepares validated biological systems for downstream workflows by establishing a dialysis membrane with defined molecular cut-off (30 kDa) and exchange length (2 mm).
- Operational Value: Promotes assay standardization and reproducibility through consistent probe dimensions and membrane performance across substance classes.
- Scalability: Enables platform reuse and adaptation to larger exchange lengths for diverse animal models, supporting high-throughput screening readiness.
Translational & Preclinical Research
- Translational Continuity: Connects discovery-phase neurochemical measurements to preclinical validation by monitoring substances relevant to disease pathology.
- Risk-Adjusted Advancement: Informs preclinical go/no-go decisions through quantitative recovery data that reflect blood-brain barrier permeability and target accessibility.
- Biomarker Alignment: Supports translational biomarker development by enabling detection of neuropeptides and metabolites in extracellular fluid.
Pipeline & Workflow Integration
The method integrates into the discovery continuum from hypothesis testing through lead identification, providing quantitative neurochemical readouts that support mechanistic understanding and compound prioritization.
- Discovery Biology: Facilitates hypothesis testing and pathway clarification by measuring in vitro recovery of endogenous neurotransmitters and metabolites.
- Screening: Delivers assay-ready systems with reproducible outputs for evaluating compound effects on neurochemical flux.
- Analytics: Provides quantitative dependent variable measurements (recovery percentages) that enable cross-condition comparison and structure-activity relationship analysis.
- Translational Research: Bridges discovery to preclinical work by generating data relevant to target engagement in disease-relevant systems.
- Enterprise Reuse: Establishes a reusable capability for neurochemical monitoring that can be adapted across projects and model systems.
Operational & Enterprise Impact
- Scientific Value: Enhances predictive confidence in target validation by reducing mechanistic ambiguity through direct neurochemical measurement.
- Operational Value: Ensures standardization, reproducibility, and scalability via low-cost, customizable probe assembly.
- Strategic Value: Improves go/no-go decisions and capital efficiency by enabling early biological de-risking in discovery.
- Portfolio Impact: Supports risk-adjusted prioritization through reliable recovery data that inform advancement criteria.
Implementation Considerations
- Requires expertise in microdialysis principles, membrane handling, and adhesive bonding techniques.
- Needs instrumentation for precision cutting (scalpel, pliers), surface preparation (sandpaper), and curing (overnight epoxy/hot glue).
- Demands cross-team standardization of probe dimensions, exchange length, and membrane preparation for reproducible results.
- Involves adaptation considerations for different molecular weight cut-offs, membrane materials, and exchange lengths across model systems.
- Includes practical limitations such as manual assembly time, skill-dependent reproducibility, and need for in vitro validation per batch.
