When ordering factors such as SCF and TPO for stem cell culture, how do you convert the units, and how do you confirm the shelf life?

<p>For non-clinical expansion of CD34+ cells, research-grade cytokines are generally sufficient, but the downstream application must be considered. If the purpose is only in vitro expansion, flow cytometry characterization, or functional assays, research-grade cytokines with low endotoxin levels will suffice; if the cells may subsequently be used in animal models or preclinical translation, products that are at least animal-component-free and low-endotoxin should be selected, with endotoxin levels kept as low as possible.</p>

Unit conversion cannot be done using a fixed formula; it must be calculated based on the specific activity in each batch's COA. For example, SCF and TPO datasheets often list both μg and IU, with specific activity expressed as IU/μg, which may vary between batches. When purchasing, clearly specify the reference catalog number, specifications, required total μg and total activity units, as well as endotoxin and purity requirements. It is not a fixed relationship like "1 μg = how many U." Require the supplier to provide a COA with the shipment, and verify the batch number and specific activity; the COA is a necessary document for incoming inspection and experimental records. In particular, CD34+ expansion is sensitive to activity and cannot be assessed based on protein amount alone.

Pay special attention to lead time and cold chain. Such factors are mostly shipped on dry ice; upon arrival, check the remaining dry ice, outer packaging, and temperature records. Some suppliers include a temperature indicator card. After receipt, do not repeatedly freeze-thaw the entire vial; dissolve it in the solvent recommended by the COA, aliquot into single-use portions, and store at -80°C. Imported research-grade products are commonly in stock with a lead time of 1-4 weeks, while GMP-grade may be substantially longer. The purchase order must state "cold chain shipping required and temperature records provided." During incoming inspection, verify the catalog number, lot number, and expiration date; do not put into inventory if there is any discrepancy. After dissolution, avoid long-term storage at 4°C or -20°C and use as soon as possible.

Don't just look at µg for factor units; IU conversion must be based on specific activity, which can vary from batch to batch.

Upon receipt, check the COA and expiration date first. After aliquoting and freezing, avoid repeated freeze-thaw cycles—we've learned this the hard way.