Pre-Pulled Microcapillary Needles (10/pack)

MINJ-PP:  $64.86 - In Stock

Filament Options

Tritech Research offers high-quality pre-pulled microcapillary needles suitable for injection of C. elegans, Drosophila, Zebrafish, Xenopus, mammalian cells, or any other application requiring fine tipped injection needles.

Our pre-pulled injection needles have an outside diameter of 1.0mm O.D. and an inside diameter of 0.6mm I.D. along the shaft. The actual tip diameter of our microinjection needles is less than 1 micron (< 1 µm). We offer the needles with two options: containing an internal glass filament for easy back-loading, and without.

The option with filament is super convenient for applications requiring less than 1 microliter in the tip. The back of the needle can be placed in a microcentrifuge tube with a drop of injection solution (for example DNA) in it, and the solution will climb up the interface between the filament and the ID of the microcapillary tube. Unless you watch with a microscope, it seems like magic as the solution starts filling from the tip backwards (after 1-5 minutes of the solution climbing up the fllament)! The option without filament may be more convenient for application where more than 1 µl is backloaded into the needle using a loading needle. Both types are available in packs of 10.

If you are interested in other sizes/types of pre-pulled needles, please contact our sales department.

image of needle cross-section
Cross-section of micro-capillary needles


Q: How do I open the tip of a pre-pulled needle without compromising the sharpness of the needle or using razor blades to cut the tip?
A: You can follow this simple procedure to etch the tip of your borosilicate microcapillary needle with hydrofluoric acid (HF):

1) Firmly secure your pre-pulled needle in the MINJ-4 needle holder attached to your MINJ-D (or other pressure driven microinjector.)
2) Adjust the MINJ-D to the following settings: Time= Manual (0.0 sec); injP=70 kPa; holdP=0 kPa; aspiration thumbscrew should be set fully clockwise;
3) Place a 200-microliter drop of concentrated HF into a lid from a 100ml plastic (not glass as the HF acid will damage / eat through it) Petri dish and place it under your dissecting scope.
4) Have a 500 mL beaker (or similar vessel) half-full of sterile water nearby.
5) Begin an injection with the microinjector (by holding down the foot pedal) and carefully stick the needle tip into the acid drop.
6) The acid will begin etching away the tip of the needle. As soon as you see bubbles coming from the needle tip, remove it from the acid and place it into the beaker of water to dilute/neutralize/stop the acid reaction.
7) After removing the needle from the water, stop the air injection by releasing the foot pedal.
You should now have a really fine, sharp, open needle.

Q: What are the tip sizes of your MINJ-PP needles? Do you make needles with different tip sizes?
A: Our MINJ-PP needles are capillaries that we have already pre-pulled into injection needles with a tip size of less than 1 micron. If a different sized opening or beveling is required, you can do that by either breaking the tip, etching with hydrofluoric acid, or by using one of our microgrinders or microforges. We can also custom make needles for you at a significant additional cost. The set up charge is quite a bit. We might be able to save you some money if you can order at least 100 needles of the same specification at the same time.

Q: What are the differences between the MINJ-PP with internal filament and without and which version of would you recommend?
A: If the total injection volume is less than 1 µl, then we recommend the MINJ-PP pre-pulled needles with Internal Filament. The needles will be able to load themselves by back-loading and dipping the back end of the needle into the injection solution.
However, if the total volume needed for your injection session is significantly greater than 1 microliter, the needle itself won't be able to draw up enough solution by mere capillary action. You will need to use a loading pipette to fill the needle from the back, and using the MINJ-PP pre-pulled needles without Internal Filament may be safer to make sure nothing interferes with the loading pipette. However, you can use the MINJ-PP with Internal Filament in this case as well.

Q: When I backfill my needles by allowing it to lay diagonally with the back of the needed in a drop of my injection solution, I see the tip has some solution, but when I look at the needle under a microscope the main body isn't full of liquid. What's going on?
A: What you are seeing is normal. A vertical or diagonal angle are both fine. There is only enough capillary action to fill the tip of MINJ-PP (maybe 1 microliter or less) by this method, not very far back, although you could wait up to 15+ minutes to see if it fills a little more. To fill the main body of the needle, one has to insert a very thin loading pipette in the back and squirt it in. These can be made by flame-drawing a 100 micro-liter glass capillary tube, and there are premade plastic pipetteman tips that will work, too.

Q: What are the ID and OD of the tip of the MINJ-PP needles?
A: Since our needle tips are very sharp (sub-microscopic with respect to the wavelengths of visible light), one way to confirm the dimensions of glass needles pulled to a sharp tip is to examine them by electron microscopy, which we do not do, so there is likely some variability. Based on literature regarding this topic, we will guess that our tip's OD is ~500 nm and the ID is ~250 nm. These dimensions are probably within 50% of the true value of our MINJ-PP.

Q: What concentration of Hydrofluoric Acid would you recommend using for etching needles?
A: Our suggestion is to buy 500 ml or 1 liter (whatever is the smallest / cheapest bottle) of 49% HF (a commonly available concentrate). Then you can dilute it however you want to slow things down if you find that full strength eats the glass faster than you can control. For each session you should need less than 1 ml, so 500 ml will last a long time.

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