Hi
Recently, I have had this trouble of clogging needles during microinjcetion which has become worse with each passing day. I am unable to fix this. I always spin my sample for half hour and try to take the uppermost layer for loading the needle but it hasnt really helped. Any suggestions??
Thanks
Joan
How do you break your needle? Often times a slightly bigger opening will prevent clogging (it’s a balance between having a needle point small enough to minimize damage to the worm and one large enough to avoid clogging).
I use needle puller to make needles from glass capillary and then gently slide it along side of a small capillary piece placed in oil to break it to have enough opening. I know what you mean by having the right balance but more often than not, I end up having either too small or too big of an opening:( I was wondering if I could do something to improve this.
it might also have something to do with how you are loading your needles. if you load by putting a tiny drop into the butt-end of the needle and let the capillary wick the liquid down to the tip then the dna solution can pick up debris along the way. if you use a drawn out pasteur pipette (or micro capillary, or one of those thin plastic pipette tips) to load the solution right down to the tip this is less likely. if your injection needle has an abrupt taper it is going to be harder to get it to break off without winding up too big. if you are pulling your own needles, then just increase the heat a little to get a longer taper (if you us a flaming-brown puller it would be useful to read the manual, which explains what all those settings actually do).
It sounds like the clogging is a recent phenomenon, which suggests there might be something different about what you’re doing now. Make sure there is no food transferred when you move the worm to the pad. This can be very difficult with unc-119 worms, for example, because they can’t leave the food and you’re stuck with it. You can try to use the halocarbon oil to pull it away from the animal. You can also do a little pre and post-injection injection to flush any associated debris. Lastly, I’ve found that sometimes the best way to clear a weakly clogged needle is to try to inject another animal. There’s something about the needle going in that works as well or better than the clearing protocol.
-Kevin.