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Simple questions we add here on a regular basis, difficult questions, complex problems that occur more then once... all gathered here below on this page.
We have just started our dr.Fish series of frequent asked questions answerred in a short video by dr. Fish, the alter ego of dr. Michel Fischbach.
This page is continuesly under constuctrion, we are adding new information on a regular basis. From now every frequent question we get will be added.
Q: is XerumFree™ fully defined?
A: Yes, it does not contain any variable materials
Q: is XerumFree™ animal-derived component free?
A: Yes, it does not contain any animal derived component, nor are animal components used during production and on top there were no animal derived components used at the production plant
Q: is there difference between XerumFree™ batches?
A: No, every singles batch is exactly the same as a previous one, so no need for storing large batches
Q: At what temperature is XerumFree™ to be stored?
A: Storage is done at 4 °C (+/- 2°), however, a few days out of the fridge doesn't harm
Q: Can XerumFree™ be frozen ?
A: Yes, but we do not reccomend it and you can only do it once
Q: Is XerumFree™ available in cGMP?
A: We have recently decided to produce only a cGMP versions.
Q: Can XerumFree™ be used for stem cells?
A: Yes, it has been tested succefully with various stem cells at external institutes
Q: Is XF available in bigger packsizes than stated on the website?
Q: Is there a risk of interference from XerumFree™ in proteomic studies of kidney expressed proteins ?
A: No, for al main established proteins secreted by the kidney the interferance is not anticipated and improbable
Q: Why should I use serum-free media?
A: The implementation of serum-free cell culture processes allows for better consistency of results since fewer undefined components are used, which translates into a much higher control of the cell culture conditions. This is particularly true when chemically-defined culture media are operated. Serum-free means also no need to qualify FBS batches for your specific applications, no storage problems and last not least, no animal welfare issues.
Q: What are the differences between serum-free, chemically-defined media and animal-component-free media ?
A: During the history of serum-free media development the first generation consisted of products that didn’t make use of animal sera but contained many animal-derived products like serum proteins, hormones and peptides from various hydrolysates; the second generation of serum-free products consisted of low protein-content products and chemically defined formulations that were devised to address the problems of interferences from undefined factors and also to facilitate purification processes in bioproduction processes. Ultimately, regulatory pressures have induced a shift to completely animal component-free cell culture media in order to mitigate all possible contamination risks, especially the risks of TSE / prion transmission.
Q: Why should I consider animal component-free media?
A: The use of animal component-free formulations concerns above all the biotechnological production of human therapeutic products, such as recombinant proteins, vaccines and monoclonal antibodies. In this industry sector, regulators are pressing to eliminate the threat of contamination from adventitious agents that are potentially present in animal-derived proteins. This regulatory advantage of ACF media (Animal Component-Free), coupled with a fully controlled cell culture environment qualifies these products as the highest standard in cell culture today .
Q: What products does TNC BIO offer as alternatives to animal sera ?
A: TNC BIO offers one single universal serum replacement, Xerum-free, which satisfies the nutritional requirements of virtually any cell type. Xerum-free has been developed without the addition of growth factors or hormones because at TNC BIO we hold to the principle that it is easy to add a factor, but almost impossible to take it out. The presence of bioactive agents, such as growth factor cocktails and hormones in many serum-free products obstructs again the full control of the cell culture conditions, a problem that is all the more accentuated by the fact that most commercial formulations are kept secret, a fact that works against the meaning of chemically-defined media. The scientists at TNC BIO are committed to providing their suggestions regarding the use of growth factors or hormones, whenever indicated for specific cell types and applications.
Q: Why is the recommended seeding density important?
A: During cell culture, cells secrete a host of factors into the culture medium that control cell attachment, growth and proliferation. However, during the seeding step these factors are absent in the fresh serum-free medium and a critical level of cell density is essential to induce an immediate and sufficient production of these autocrine/paracrine factors. In our experience, the use of conditioned medium from a previous passage can substitute for the lack of these factors at the cell plating stage. Please see also our Technical Note regarding the application of TNC BIO’s ACGS principle (ACGS - Autocrine Cell Growth Supplementation).
Q: Which enzyme do you recommend for the dissociation of adherent cell monolayers ?
A: The use of standard trypsin preparations can become somewhat problematic in the absence of serum, which contains trypsin inhibitors. Thus, in serum-free conditions it is important to minimize the proteolytic activity of residual trypsin in order to avoid irreversible damage to the cells. This can be best achieved by the use of trypsin inhibitors (e.g. from soybean) or by employing a non-mammalian dissociation reagent such as Accutase™ which does not require inactivation or removal during passaging. Alternatively an additional wash step of the cell pellet will remove most of the remaining trypsin. However, this procedure implies an extra centrifugation step that can be damaging for some cell types. Please do not hesitate to contact us for additional suggestions regarding your specific cell type.
Q: I am in academic research. Why should I abandon the use of serum in my cell cultures ?
A: serum is ill-defined and variable from lot-to-lot so that you are uncertain of all factors that impact your culture environment. Serum may contain elements that mask or inhibit normal biological functions you plan to study. Moreover, certain cell types are unable to grow with serum supplementation because of overgrowth by contaminating fibroblasts or inhibitory or differentiating serum factors. Also, if your research generates results that could ultimately be transferred to pilot or production scale environments for biopharmaceutical applications, then you should seriously consider to discard the option of using serum.
Q: Do I need to add growth factors along with XerumFree™ ?
A: The cellular requirements and culture procedures for cells employed in serum-free medium diverge in several important ways from those suitable for cells maintained in traditional serum-containing cell culture. The long-term use of serum changes the phenotype of the cell. Information from serum signaling molecules is transduced, processed, and physiologic response motifs are mediated by interaction with the paracellular microenvironment. In normal tissues, in the absence of local or systemic injury, cells never encounter the biologically active products of the clotting cascade and/or mediators of pathology produced by leukocyte degranulation or platelet lysate. Those factors are a characteristic of serum, not blood plasma, and stem from an indiscriminate cellular “response to injury”. A good serum-free medium will not contain those factors released by the clotting process, including the platelet lysates. In specific situations the addition of a limited number of factors and hormones may be considered to optimize the cell culture growth dynamics, but in general most cell types are competent for auto-regulating the cell culture growth and proliferation by means of autocrine and paracrine factors released by the very same cells. Please consult our Application Notes for specific requirements of the main cell types.
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