What Is the Role of Filter Membrane in the Syringe Filter (2)?

2. Hydrophobic membrane material
PTFE membrane is a hydrophobic material membrane that can be used in a variety of routine sample preparation and filtration. PTFE membrane filters can be used when the membrane material is required to exhibit hydrophobic properties to prevent the flow of moisture and allow air or gas to filter through. PTFE membrane has a wide range of applications in filtering gas. The membrane will not allow liquid to filter through until it is “soaked”. PTFE shows an excellent blocking effect on passive fluids, which is very suitable for filtration that requires an incubation step. PTFE membranes are available with 0.2μm, 0.45μm and 1μm pore diameters.

The scope of application includes:
• Molecular synthesis reaction
• Drug synthesis reaction
• Organic sample preparation
• Ventilation of fermentation tanks and fermentation barrels

pvdf membrane filter hydrophobic ptfe membrane filter ptfe membrane filters

3. Pre-filter membrane material
The pre-filtered membrane can be used to increase the flow rate of the filtrate and remove particles for clarification experiments. The large pore size of the pre-filtration membrane helps to remove particles and cell debris. The membrane has the same non-adsorption characteristics as previously described. There are many different configurations of pre-filtration membranes to choose from.

The scope of application includes:
• Clarification of cell lysate
• Plasmid preparation
• Preparation of samples saturated with particles
• Preparation of protein solution

4. Molecular separation (ultrafiltration) membrane material
4.1 Ultrafiltration membrane
It is a modified polyethersulfone membrane designed to reduce the adsorption of proteins and nucleic acids. The membrane is based on the principle of molecular exclusion to separate samples according to their molecular weight. Molecular exclusion can be achieved by selecting a suitable molecular weight cut-off membrane to separate large and small molecules, and then separating samples by vacuum or centrifugal filtration. Modification of the membrane can prevent the adsorption of biomolecules to the membrane and facilitate the concentration of larger molecules on the membrane surface. The low adsorption of the membrane gives it many advantages, including high recovery of low concentrations of biomolecules and lower surface contamination, which may weaken the membrane’s retention.

Generally, choosing the right molecular weight cut-off is consistent with the principle of choosing the right centrifugal concentrated product. The molecular weight cut-off of the membrane should be 1/6 to 1/3 of the molecular weight of the biomolecules that are cut off. For example, if the molecular weight of the protein to be retained is 60K, a membrane with a molecular weight cut-off of 10K should be selected. The available membrane molecular weight cut-offs include 1K, 3K, 5K, 10K, 30K, 50K, 100K, and 300K.

The scope of application includes:
• Concentration, purification, and desalination of peptides, proteins, oligonucleotides, DNA, and RNA
• Labeling reaction and PCR reaction recovery
• Separate DNA from agarose gel
• Size exclusion chromatography

4.2 Filter membrane material combined with biomolecules
Glass fiber membrane filters with polypropylene as the backing layer
The use of glass fibers in the filter plate provides an economical and feasible solution for removing particulate matter in the sample and maintaining the integrity of the sample. This is a good choice for low-cost, crude sample preparation. The glass fiber is made of non-sticky borosilicate glass, which will not cause impurities to dissolve out and contaminate the sample. The glass fiber membrane is supported by a polypropylene layer. The support layer will not have eluted matter and can prevent the glass fiber from falling into the sample. Available aperture specifications include 1.0μm and 3.0μm.

The scope of application of glass fiber membranes includes:
• Cell-based analysis
• Coarse fractionation
• Receptor: ligand binding analysis
• DNA binding
• Plasmid DNA extraction

4.3 Anion exchange membrane
The membrane has super anion exchange capacity, fast sample processing flow rate, and does not affect the binding and recovery, and its binding capacity per well can reach 0.38mg bovine serum albumin/well. There are two product forms for filter plate and syringe filter.

The scope of application includes:
• Removal of virus particles
• Binding and elution of negatively charged proteins
• DNA purification

4.4 Cation exchange membrane
The membrane has a super strong cation exchange capacity to process samples with fast flow rate and does not affect the binding and recovery, and its adsorption capacity per hole can reach 0.29mg lysozyme/well. The membrane is available in two product forms: filter plate and syringe filter.

The scope of application includes:
• Kinase detection
• Binding and elution of positively charged proteins

4.5 Pure nitrocellulose membrane
With a pore size of 0.2μm, it is a 100% pure nitrocellulose membrane with good durability and high binding ability to proteins and nucleic acids. The binding effect of the membrane is based on its hydrophobic and electrostatic effects, which makes it very suitable for spot hybridization of proteins and nucleic acids. The membrane is widely used and can be used for chemiluminescence, fluorescence, colorimetric, and radioisotope detection.

The scope of application includes:
• Nucleic acid transfer and detection
• Solid-phase ELISA (enzyme-linked immunosorbent assay)
• Radioimmunoassay
• Fluorescence or chemiluminescence detection

4.6 PVDF (polyvinylidene fluoride) membrane
PVDF filter has a wide range of uses and can be used for the combination of nucleic acid and protein. The membrane has a pore size of 0.45μm and has wide compatibility with common solvents. The background value of the PVDF membrane is very low when it is used for chemiluminescence detection. It will not fade during use and is durable. The binding reaction of the PVDF membrane is hydrophobic, and biomolecules can be immobilized on the membrane by UV cross-linking and base immobilization. Because PVDF membrane is not easy to fade, it is very suitable for the detection of color reaction.

The scope of application includes:
• Protein: Nucleic Acid Interaction Research
• Western blot
• Solid-phase ELISA (enzyme-linked immunosorbent assay)
• Radioimmunoassay
• Fluorescence or chemiluminescence detection
• Use combined biomolecules for drug development
• ELISA Spot EliSpots

As the saying goes, a good experiment depends on a good sample, a good sample depends on a good filtration, and a good filtration depends on the selection of the right membrane material. Based on the above introduction, HAWACH believes that your experiment has been half successful. With the further development of material technology, filtration technology will play an increasingly important role in our lives and work. Welcome to share more with us.

Please click here to know PVDF vs PTFE