What should you consider when selecting a plasma separation membrane?
Generating high-quality plasma from whole blood samples without the use of a centrifuge is a focus in the quest to develop point-of-care (POC) diagnostic assays that address end-user requirements for simplicity and speed, as well as accuracy. Many assays cannot accept the inherent variation of whole blood and require a reliable method for separating plasma from whole blood. Using the right separation membrane can efficiently produce a plasma of equivalent quality to utilizing centrifugation and support optimization of diagnostic applications such as microfluidic and lateral flow format POC devices.
Consider the following factors when selecting a plasma separation membrane to meet the sensitivity and reproducibility needs of your application:
- Blood volume – Not all plasma separation materials can accept the same amount of whole blood. For optimal separation, select a membrane of the correct grade for your application.
- Plasma volume – The amount of plasma generated from lateral filtration through a membrane varies depending on the polymer type. The two most commonly used substrates for plasma generation are asymmetric polysulfone and glass fiber. Glass fiber materials typically generate less plasma per microliter of blood than other materials.
- Hemolysis – Some materials can cause red blood cells to burst during filtration, which can impact downstream analysis. It is important to understand the amount of hemolysis your assay can handle as you approach the selection of a plasma separation material. Glass fiber is difficult to fabricate into devices. Over-compression causes glass fiber cracking which increases the chance of sample hemolysis.
- Separation time – If your assay has time constraints, you should consider the time taken by the media in separating plasma from whole blood.
- Non-specific binding – Although glass fiber materials are commonly used in blood separation applications, they present certain performance limitations. It is common for these materials to bind target analytes such as lipids (e.g., cholesterol). It is imperative that the binding characteristics of the blood separation material are evaluated to ensure that the biomarker of interest is not bound by the filter matrix thereby potentially reducing assay sensitivity.
One Step Plasma Separation from Whole Blood - Vivid™ Plasma Separation membranes
Pall’s patented Vivid Plasma Separation membranes are robust materials for the rapid and efficient separation of plasma from whole blood. The membrane can separate > 80% of the theoretical plasma available from the whole blood sample with minimal hemolysis in less than two minutes. Multiple grades of the membrane are available to support the blood volume requirements of your assay.
- Dependable performance - The highly asymmetric nature of the Vivid Plasma Separation (PS) membrane allows efficient removal of the cellular components of blood without centrifugation. Red cells, white cells and platelets are captured within the larger pores on the upstream side of the membrane. Cells do not lyse, and the plasma flows through the smaller pores on the downstream side of the membrane. This rapid separation process yields plasma similar in HPLC and SDS-PAGE profiles to traditional centrifuged plasma.
- Low hemolysis - Hemolysis levels are significantly lower than glass fiber media-generated plasma.
Vivid™ Plasma Separation membrane
- High plasma yield - Vivid PS membrane can yield ≥ 80% of the theoretical plasma available, while comparable glass fiber yields are typically in the region of 30-50%. The percent of plasma recovered from different volumes of blood does not depend on the blood volume applied to the Vivid PS membrane (Graph 1).
- Low sample volumes - High plasma yields, mean a lower volume of starting whole blood is needed. This is advantageous for POC, and POU diagnostic applications as smaller amounts of blood are needed from patients or animals.
- Low analyte binding - Whole blood processed through the Vivid PS membrane has shown equivalent 2D SDS-PAGE protein profiles for the cardiac biomarker Troponin I as compared to centrifuged plasma. This data indicates that the protein concentration of clinical biomarkers is not reduced when processed through the membrane, thus making it an ideal material for diagnostic applications (Graph 2). All plasma samples were generated from the same sample of fresh EDTA blood spiked with Troponin I at 1 ng/mL. Protein concentration in each sample was measured in triplicate.
- Device integration - Compatible with point of care (POC) and point of use (POU) diagnostic platforms such as lateral flow test strips and microfluidics.
Vivid membrane for separating plasma from whole bloodis available in three grades designed for specific applications:
|GF||Small blood volume applications, such as finger sticks in microfluidic and lateral flow format POC devices. This material is untreated and may exhibit higher hemolysis levels than other grades.|
|GX||Small blood volume applications, such as finger sticks in microfluidic and lateral flow format POC devices. Also compatible with electrochemical analyte detection. Post-treatment helps to minimize hemolysis.|
|GR||Larger blood volume applications, such as lateral flow immunochromatographic devices. Post-treatment facilitates larger blood volumes with reduced hemolysis.|