I've been using Lenti-X recently and have got v poor yields (10%) so think ultra-centrifugation may be a better option for me. Does anyone have any thoughts?
I have had excellent results with PEG-it, a similar product form System Biosciences. However I have only used it in vitro. SBI claims their product is nontoxic and safe to use on embryonic stem cells, they also claim that there is "No accumulation of cellular debris like with ultracentrifugation—avoid toxic and immunogenic reactions by using PEG-it™ instead" It may be worth contacting the company to ask about its safety in vivo.
I fail to spot any difference between these "optimized proprietary" commercial mixes and a simple PEG 6k solution that you can make for a penny. I suspect all these products are simply identical to PEG 6k, which is non-toxic in vivo, unless you transfer a very high concentration. I'd just go with PEG 6k that you dilute yourself. Saves you completely unnecessary expenses, plus you're sure what you've got.
When using PEG concentration, technique is important. It helps to spin extra hard (>4k, >30 min or more if you can). The pellet is often invisible -- know where it is, and don't hit it with the pipette. It's really easy to lose the virus at this step. PEG is viscous. Pipet slowly and carefully. If you're too fast, you can easily drag the pellet out along with the PEG. After you removed most of the liquid, and spin them a second time, to flush residual PEG off the tube walls. Remove the remaining PEG after the second spin with a suitably small pipet tip, again, carefully avoiding the space where you suspect the pellet to be.
In my hands, it is possible to transfer enough PEG to harm the cells in culture. Residual PEG seems to cause loosely adherent cells to wash off even more easily. The second spin step should get rid of this problem.
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