Binding Membrane
Question: Can I use the SCN membrane from any side or is there a specific side which will give better results?
Answer: Unlike other Nitrocellulose membranes available in the market, our SCN membranes offer uniform surface on both sides and give identical results.
Syringe Filters for Sample Preparation
Question: Are your filters suitable for HPLC sample filtration?
Answer: Yes, our filters are HPLC certified to assure that these do not add artifacts to the sample
Question: My samples are very turbid even after filtration through a 0.2µm syringe filter the downstream is somewhat hazy.
Answer: Use GNNSY25 syringe filters. These are special filters with a microglassfiber pre-filters that retains turbidity causing very fine colloidal particles. This pre-filter also protects the downstream membrane thereby enhancing throughputs.
Sample pads
Question: How should I select a sample pad?
Answer: The sample pad should not bind proteins nonspecifically, should exhibit good flow characteristics, and have adequate volume capacity. Its thickness should be such that it fits in the test device
Question: Are any additives added in the sample pad and why?
Answer: Sample pads may have many additives which a user can add to achieve desired results from the assay. The additives may be blocking agents for the membrane for rapid and uniform movement of conjugate particles, buffers to control the pH and improve specificity, detergents for improved flow and reduction of false positives.
Process Filtration Product
Question: Are your membrane filters validated for microbial retention?
Answer: Our 0.2µm membrane disc filters are validated for retention of Brevandimonas diminuta at a challenge level of 107 org/cm˛ as per HIMA and ASTM F838-83. Other pore sizes like 0.45µm and 0.8µm are also validated with Serratia marcescens (0.5µm) and staphy lococcus aureus (0.9µm).
PES Syringe Filters
Question: What is the protein loss with PES syringe filters?
Answer: PES syringe filters offer protein recovery of > 99.9%.
Question: For serum samples of upto 50µl, I have to use multiple syringe filters and also the hand pressure required is too much.
Answer: SGPESY25 syringe filters are specially designed to incorporate a pre-filter layer of microglassfiber that protects the downstream membrane layer and enhances throughputs at much reduced pressure.
Question: Can I use the SGPESY25 for 1 liter media sterilization using a syringe?
Answer: Normally for volumes more than 200ml, it is recommended to the SGPESY25 with a peristaltic pump, as it would be a little inconvenient to filter large volumes with a syringe.
Membranes
Question: For lateral flow membranes, what is the significance of pore size?
Answer: Pore size is only a name designation. One manufacturer’s pore size designation can be quite different from another’s. Bigger pore size is designated for membranes with faster wicking rates.
Question: If pore size is only a name, how do you differentiate between different membranes?
Answer: The wicking time is an important parameter for lateral flow membranes. Membranes of designated pore size will exhibit highly repeatable wicking time.
Question: Should I block the membrane?
Answer: All membranes exhibit stable wicking rates without blocking. It is possible to make many good assays without blocking. However, should there be a need to wet block the membrane for stabilizing the Ab, reducing nonspecific reaction, or improving the migration of conjugate particles, all membranes can be blocked.
Question: Do you have detergents/wetting agents in the membrane?
Answer: NC is a hydrophobic polymer. To be able to use the NC membrane successfully it is necessary to add a small amount of detergent or a combination of detergents. The amount is so small that it does not affect the binding properties of the membrane.
Question: I got a very faint shadow of false positive. I suspect the membrane. Answer: False positive is primarily due to nonspecific binding of the conjugate particles. Using bigger pore size membrane can help reduce this, usually at the cost of sensitivity. Addition of detergents in the sample pad can also help minimize it.
Question: I get broken lines while printing the reagent line and zones where membrane does not absorb the liquid. How can the problem be resolved?
Answer: If the NC membranes are allowed to stay in the open for a few days they tend to attract hydrophobic dust particles or other moieties, which can cause above problem. Addition of 2-3% Isopropanol in the reagent formulation will help minimize above problem
Question: How much time should I wait for the Antigen/ Antibody to bind on the membrane before an assay is run?
Answer: The binding of the protein to the NC membrane grows stronger as it is dehydrated more and more. Usually, at room temp, (20-30° C), 50-60% RH the binding will reach a maximum in 3-5 days. For development, reasonable results can be expected with overnight drying at room temperature.
Question: My tests are not stable with time. Is the membrane to be suspected?
Answer: Membrane does not affect the stability of the assay. It is related to the chemistry of the assay, and many a times it improves by adding sucrose (0.5-1.0%) to the capture Antibody solutions.
Commercial/Others
Question: What are yours production capacities?
Answer: Nupore Filtration Systems, established in 1987 has the capacity to manufacture thousands of sq.ft. of membrane everyday. Capacities are being further expanded.
Question: In case of problem, what support can I expect?
Answer: We respond very quickly to assist our clients in analyzing the problem and isolating the source. We label and retain a part of dispatched material for a period of 2 years, from all our shipments. This retained material is crucial in replicating the problem and identifying any possible defects in the membrane itself. In the rare case of membrane being found defective, a full replacement of the lot on priority is manufactured and dispatched.
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