Peripheral Blood Mononuclear Cells (PBMCs) play an essential role in immunology, cell therapy development, and many disease research models. Isolating these cells from bone marrow can be a demanding task, requiring careful sample preparation to ensure high cell viability and purity. The early steps — removing debris, filtering particulates, and reducing clumping — directly influence the yield and quality of the final PBMC population.
In many laboratories, Lab Cell Strainers are a standard part of this workflow, helping prepare samples before density gradient centrifugation or other separation techniques. However, bone marrow presents unique challenges: it is highly viscous, contains variable particle sizes, and often has fibrous components that can clog conventional filtration devices. This is where the ÜberStrainer offers a clear advantage.
With its modular design, multiple mesh sizes, and compatibility with different tube formats, the ÜberStrainer can be tailored to specific bone marrow processing needs. It enables efficient filtration under a range of pressure conditions, making it ideal for scaling up PBMC isolations while maintaining reproducibility and sample integrity.
This article explores how the ÜberStrainer works, why it is particularly suited for PBMC isolation from bone marrow, and how it fits seamlessly into research and clinical laboratory workflows.
Understanding PBMC Isolation from Bone Marrow
PBMCs include lymphocytes (T cells, B cells, NK cells) and monocytes, all of which are critical for immune function studies. Bone marrow, however, is not a straightforward source material. Compared to peripheral blood, it contains more heterogeneous components:
– Red blood cells and platelets
– Granulocytes and immature precursor cells
– Fibrous connective tissue and bone fragments
– Protein-rich plasma that can increase viscosity
When isolating PBMCs, the primary objective is to separate them from other cell types and debris while minimizing damage. A standard approach involves:
1. Collection of bone marrow aspirate in anticoagulant-treated tubes.
2. Initial filtration to remove clumps, fibrous tissue, and large debris.
3. Density gradient separation to isolate the PBMC fraction.
4. Washing and counting to prepare for downstream assays or culture.
The first filtration step is critical. Inefficient or inconsistent filtration can lead to:
– Lower PBMC yield due to trapped cells.
– Increased debris in the gradient, reducing separation quality.
– Extended processing times due to clogs or slow flow rates.
The ÜberStrainer was designed to overcome these issues, offering greater flexibility and precision than standard filter devices.
What Is the ÜberStrainer?
The ÜberStrainer is a sample preparation device optimized for mesh-based filtration in cell separation workflows. Unlike fixed-format strainers, it offers multiple interchangeable components that make it adaptable to a wide range of volumes, tube formats, and mesh sizes.
Key Design Features:
– Screw Cap with Luer-Lock Adaptor
Allows secure connection to syringes or other devices, enabling both gravity-based and pressure-assisted filtration.
– 6 mL Housing with Integrated Mesh
Available in 15 mesh sizes, from 1 μm to 500 μm, making it suitable for coarse debris removal or fine particulate filtration.
– Connector Ring with Luer-Lock Port
Attaches directly to standard 50 mL tubes for efficient large-volume sample handling.
– Tube Adaptors
Allows compatibility with 15 mL, 2 mL, and 1.5 mL standard laboratory tubes for smaller volume processing.
Why This Matters for Bone Marrow Processing:
Bone marrow samples can vary widely in composition. Having the ability to choose mesh size and adapt to different tube formats ensures optimal sample preparation regardless of the initial volume or debris content.
How the ÜberStrainer Supports PBMC Isolation
The ÜberStrainer enhances PBMC isolation in bone marrow workflows by addressing three core needs: efficient debris removal, adaptability to sample variability, and compatibility with downstream separation steps.
1. Efficient Debris Removal Without Losing Target Cells
During bone marrow filtration, large particles and fibrous tissue must be removed without discarding PBMCs. By choosing an appropriate mesh size — for example, 70 μm for coarse debris or 40 μm for finer filtering — researchers can retain a high percentage of mononuclear cells while eliminating material that would interfere with density gradient separation.
2. Adaptability to Sample Variability
Bone marrow aspirates differ in viscosity and particle load, especially between donors or collection sites. The ÜberStrainer’s modular mesh options and pressure-assisted capability mean filtration can be tailored in real time, avoiding bottlenecks in sample prep.
3. Seamless Integration into Standard PBMC Workflows
Whether using Ficoll-Paque, Lymphoprep, or similar separation media, the ÜberStrainer fits into the early stages without requiring additional equipment changes. The Luer-lock system also allows connection to syringes for precise sample handling.
Step-by-Step: Using the ÜberStrainer for Bone Marrow PBMC Isolation
Step 1: Select Mesh Size
The first decision in using the ÜberStrainer is choosing the right mesh size. This directly affects both the clarity of the sample and the number of PBMCs recovered. For bone marrow, a 70 μm mesh is a common starting point as it effectively removes fibrous tissue, bone fragments, and large clumps without losing a significant number of mononuclear cells. In cases where the sample still contains fine debris after the first pass, a secondary filtration step with a smaller mesh (40 μm or 20 μm) can be performed to further clean the sample before separation.
Step 2: Pre-Rinse the Device
Even though the ÜberStrainer is manufactured under clean conditions, small particles from the production process can remain on the mesh. Rinsing with sterile phosphate-buffered saline (PBS) or another compatible buffer ensures these particles are removed, reducing the risk of contamination or interference with downstream assays. This is especially important in sensitive applications like flow cytometry or cell culture.
Step 3: Load the Sample
Attach the ÜberStrainer securely to the appropriate collection tube. For larger bone marrow aspirates, a 50 mL conical tube is ideal, while smaller adaptors make it possible to work with 15 mL or even microcentrifuge tubes. Pour or pipette the sample directly into the strainer housing, taking care not to overflow.
Step 4: Filter Under Gravity or Low Pressure
For most samples, gravity alone will provide adequate filtration speed. However, bone marrow can be thick and slow-moving. In these cases, the built-in Luer-lock adaptor allows gentle pressure-assisted filtration using a syringe or pump. This approach speeds up processing without damaging delicate PBMCs, provided excessive pressure is avoided.
Step 5: Proceed to Density Gradient Separation
Once filtration is complete, the clean, debris-free sample can be directly layered onto the density gradient medium (such as Ficoll-Paque) for centrifugation. The absence of large particles improves separation efficiency and ensures a higher-quality PBMC fraction, ready for counting, analysis, or culture.
How ÜberStrainer Compares to Standard Lab Cell Strainers
Standard Lab Cell Strainers are a staple in many laboratories, providing quick, reliable filtration for a wide range of cell suspensions. However, most are fixed-format devices — typically available in just a few mesh sizes and designed to fit only one or two tube types. While this simplicity works for routine samples like cultured cells or peripheral blood, bone marrow presents unique challenges. It is often viscous, heterogeneous, and filled with fibrous tissue and bone fragments that can clog standard strainers or reduce filtration speed.
Mesh Flexibility
The ÜberStrainer addresses this limitation by offering 15 different mesh sizes, ranging from 1 μm to 500 μm. This allows researchers to select the precise mesh that best suits the sample type and desired outcome. For bone marrow PBMC isolation, larger meshes (70 μm) can be used for initial debris removal, followed by finer meshes for secondary cleanup — all within the same device housing.
Tube Compatibility
Whereas traditional strainers are usually designed for a specific tube size, the ÜberStrainer includes adaptors for 50 mL conical tubes, 15 mL tubes, and even 1.5–2 mL microcentrifuge tubes. This versatility means the same device can be used across different stages of sample preparation, from bulk processing to small-volume refinement.
Pressure Options
One major advantage is the built-in Luer-lock ports, which allow gentle pressure-assisted filtration. This feature is particularly useful for viscous bone marrow, where gravity filtration alone may be too slow. Gentle pressure can improve throughput while minimizing cell stress, and it also helps prevent clogging when working with debris-rich samples.
Reusable Housing
Instead of being fully disposable, the ÜberStrainer has a durable housing with replaceable mesh inserts. This reduces waste and lowers long-term costs, especially in high-throughput labs where filtration devices are used daily.
In short, the ÜberStrainer takes the proven benefits of standard Lab Cell Strainers and expands their capabilities. It offers the flexibility, adaptability, and efficiency needed for complex samples like bone marrow, while still supporting standardized workflows — a combination that is especially valuable in high-volume research and clinical environments.
Benefits of Using ÜberStrainer in PBMC Isolation from Bone Marrow
Isolating peripheral blood mononuclear cells (PBMCs) from bone marrow can be challenging due to the sample’s complexity — it often contains fibrous material, bone fragments, and high cell density. The ÜberStrainer is specifically designed to address these issues, offering several key benefits for laboratories aiming to improve efficiency and yield.
1. Higher Cell Yields – By selecting the optimal mesh size for the initial filtration step — for example, 70 μm to remove large debris without excluding PBMCs — the ÜberStrainer minimizes cell loss. Fine-tuning mesh selection to match the sample’s characteristics ensures that more target cells make it through to the density gradient stage.
2. Reduced Processing Time – Bone marrow aspirates can be thick and slow to filter through standard gravity-based devices. The ÜberStrainer’s option for gentle, pressure-assisted filtration through its built-in Luer-lock ports keeps flow rates high without damaging cells. Combined with an appropriate mesh choice, this can cut filtration time significantly, even for difficult samples.
3. Improved Reproducibility – Consistency is critical in PBMC isolation, particularly in research or clinical environments. The ÜberStrainer’s ability to maintain standardized filtration conditions — mesh size, pressure level, and tube type — reduces variability between batches. This results in more predictable PBMC yield and purity across multiple experiments.
4. Lower Risk of Contamination – Each extra handling step introduces a contamination risk. The ÜberStrainer integrates directly with common lab tubes (50 mL, 15 mL, 2 mL), using closed connections that minimize sample transfers. This reduces the potential for microbial or cross-sample contamination during PBMC isolation.
5. Cost Efficiency- Unlike disposable Lab Cell Strainers, the ÜberStrainer’s housing is built for repeated use, with only the mesh component being swapped as needed. This modular approach not only reduces plastic waste but also lowers the per-sample cost in high-throughput labs, especially when processing multiple bone marrow samples per day.
Overall, the ÜberStrainer combines adaptability, durability, and precision, making it a strong choice for PBMC isolation workflows where speed, consistency, and cell recovery are all high priorities.
Best Practices for Optimal Results
– Start Coarse, Then Go Fine: Use a larger mesh first to remove big debris, then a finer mesh if needed.
– Avoid Excessive Pressure: Gentle pressure prevents cell damage while still improving flow.
– Keep Samples Cold: Maintain 4°C when possible to preserve cell viability during filtration.
– Rinse Retained Material: A quick rinse can recover PBMCs that might adhere to debris.
– Document Mesh Use: Record mesh sizes and sample conditions for reproducibility.
Conclusion
Isolating PBMCs from bone marrow is a process that demands both precision and adaptability. The ÜberStrainer addresses the limitations of traditional filtration devices by offering customizable mesh sizes, compatibility with multiple tube formats, and the option for gentle pressure-assisted flow. These features help maintain high PBMC yields, reduce processing times, and improve reproducibility — all critical for research and clinical applications.
For labs already using Lab Cell Strainers in other workflows, the ÜberStrainer offers a natural upgrade for challenging samples like bone marrow. By combining versatility with user-friendly operation, it becomes not just a filtration tool, but a key enabler of high-quality cell isolation.
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