General Filtration Procedures for AcroPrep™ and AcroWell™ Filter Plates 6.4

General Filtration Procedures for AcroPrep and AcroWell Filter Plates

As samples get smaller and more numerous, the need for novel methods to purify proteins and improve assays has led Pall to develop a broad line of multi-well filter plates that target specific application challenges. AcroPrep and AcroWell filter plates feature individually sealed membranes that eliminate crosstalk and solution weeping. The proprietary sealing technology allows us to seal virtually any type of membrane or media configuration into a device platform to meet ever-changing industry needs.     

The unique nature of protein science results in a variety of device requirements for each application type. Pall understands this need and has a full portfolio of 96- and 384-well filter plates that can be optimized for your assay. Our portfolio includes a selection of single- and multi-layer membranes, plate colors, well volumes, and outlet tips.

Pall’s filter plate product line includes two platforms that address different application needs:

1. AcroPrep filter plates are engineered with special outlet tips and splash guards, and can be used for both filtrate- and retentate-based applications. Membranes are individually cut, placed, and sealed in the wells using a proprietary sealing process that ensures seal integrity. A distinctive valve technology eliminates sample leaking.
2. AcroWell filter plates are designed to support retentate and hybridization-based binding applications. These plates are constructed of two membrane layers; the bottom layer protects the upstream functional membrane and acts as a barrier to passive flow. Using a plate optimized for your application will reduce sample loss, make automation easy, and add consistency and reliability throughout your entire process.

Automation Compliant

Pall’s plates are designed in accordance with the standards of the ANSI/SBS X-2004. Rigid construction enables the plates to be easily maneuvered by robotic instrumentation and assures that the plates will seal properly on vacuum manifolds, wash stations, hotel carousels, and deck platforms. Plates are compatible with industry leading workstations including: Tecan, Qiagen Inc., Tomtec, PerkinElmer Life and Analytical Sciences, Beckman Coulter Inc., Caliper Life Sciences, Inc., Waters, Proteodyne, and Hamilton Company.

Mass Spec Friendly, Chemically Resistant, and Low Binding

The polypropylene housing assembly has been tested to ensure that the materials of construction do not contribute to ion suppression/enhancement. In addition, the housing materials and media have been optimized and tested to reduce extractables, ensuring that unwanted materials are not introduced to your sample. The housing is compatible with a broad range of aqueous and organic liquids, and is noted for its low biomolecule binding that minimizes nonspecific adsorption of samples to the plates. 

No Crosstalk

Specially engineered fluid directors and outlet tips on the bottom of the AcroPrep plate are designed to reduce the potential for downstream crosstalk. Elimination of crosstalk upstream is assured through individually sealing a membrane in each well using Pall’s proprietary sealing technology. Pall understands the critical nature of each sample, and we know that seal failure will cause sample loss. To ensure integral sealing of each well, we test each lot of product for seal integrity prior to release. You can be assured that AcroPrep and AcroWell filter plates will provide a robust platform that will eliminate concerns of sample loss and cross-contamination.

Figure 6.6

Methodology: Filtration vs. Retention

 

1. Place plate on vacuum manifold or hold the plate so the outlets on the bottom of the plate are not touched.
2. Add sample and incubate. Apply vacuum (or centrifuge).
3A. Release vacuum from the manifold. Remove filter plate and retained sample for further processing. (Or, 3B)
3B. Release vacuum from the manifold. Remove filter plate. Remove collection (receiver) plate and utilize collected filtrate in downstream applications.

Protocol for General Filtration Procedures for AcroPrep and AcroWell Filter Plates

A. Vacuum Manifold Filtration

1. During use, hold the filter plate so the membrane at the bottom is not touched or scratched. (Avoid contact between the membrane and other surfaces during incubation to prevent liquid flow due to contact wicking.)
2. Place a collection plate into the vacuum manifold sized to receive the volume of filtrate expected from the filter plate
3. Place the filter plate on the vacuum manifold.
   Tip: Plates with BioTrace™ PVDF membrane (PN 5023, 5026, 5027) require pre-wetting with 0.1 mL pure methanol, 2-propanol, or 70% ethanol. Do not let the membrane dry or pre-wetting will need to be repeated. Adaptors exists for fitting non-Pall filter plates onto the Pall manifold, as well as, adaptors for fitting Pall filter plates onto non-Pall manifolds. Please contact Pall for more information.
4. After wetting, apply vacuum and rinse with 0.1 mL water or buffer.
5. Add the sample to be filtered to the plate. Incubate if required.
6. Apply vacuum to manifold to initiate liquid flow. Recommended vacuum is 25.4 cm Hg (10 in. Hg); DO NOT exceed 38.1 cm Hg (10 in. Hg); most house vacuum and aspirators do not exceed 38.1 cm Hg (15 in. Hg).
7. Gently tap the plate to remove any hanging droplets.
8. Release vacuum from the manifold. DO NOT RELEASE VACUUM BY PULLING THE CORNER OF PLATE AS IT WILL DEGRADE THE MANIFOLD GASKET.
9. If needed, add wash solutions and filter as needed.

B. Filtration Facilitated by Centrifugation in a Swinging Bucket Rotor

1. Place the filter plate on top of a suitably sized receiver plate.
2. Insert the plates into a standard multi-well plate swinging bucket rotor assembly.
3. Place a duplicate pair of plates matching the weight of the test plate (add water to the receiver plate and match weight of the test plate).
   Tip: An imbalance can result with a single test plate if no counter-balancing plate is used. If different volumes of sample are used in multiple plates, they will need to be balanced in pairs by addition of water to empty wells.
4. Centrifuge at 500-3,000 x g for 1-2 minutes.
   Tip: The g and time parameters can be varied to optimize the residence time of fluids in contact with the material in the well of the plate.
5. If needed, add wash solution(s) and repeat. Ensure that plates are in balance before centrifugation.

Figure 6.7

AcroPrep or AcroWell Filter Plate... What's the Difference?

AcroPrep Filter Plate	AcroWell Filter Plate
Membranes are individually cut, placed, and sealed in the wells.	Constructed of two membrane layers–the bottom layer of membrane protects the upstream membrane and acts as a barrier to passive flow.
Plate can be used in both filtrate and retentate-based applications.	Designed for use in retentate-based applications such as hybridization-based binding assays and time-resolved fluorescence.
Plates have either long or short fluid directors to direct the flow of the filtrate without cross-contamination.	Plate and membrane contruction allows for extended or elevated temperature incubations without solution weeping and crosstalk.
Proprietary sealing process allows flexibility in sealing a wide range of membranes both single and multiple layers.
Available in a wide range of configurations to meet various application challenges.

Figure 6.8

Various Outlet Tips

AcroWell 96	AcroPrep 96	AcroPrep 96 1 mL	AcroPrep 384 Long Tip	AcroPrep 384 Short Tip
Used for retentate based applications. Not recommended for filtrate collection.	Used for both filtrate and retentate based applications. Outlet tips are recessed beneath the skirt of the plate.	Used for both filtrate and retentate based assays. Outlet tips extend beyond the skirt of the plate and pilot into the wells of a receiving plate.	Can be used for both filtrate and retentate based applications. Outlet tips extend beyond the skirt of the plate and pilot into the wells of a receiving plate.	Can be used for both filtrate and retentate based applications. Outlet tips are recessed beneath the skirt of the plate.