Questions & Answers
Below you will find answers to most questions people have regarding Tissue Microarray construction. These questions are also addressed in our instructional videos.
IMPORTANT: Do’s and Don’ts
1.Always punch paraffin TMA block at room temperature. Cold paraffin can crack when inserting core samples.
2. Never Snap Freeze the Arraymold. Liquid Nitrogen or other frozen baths will destroy the Arraymold and this type of practice will void the Arraymold warrantee. (Refer to FAQ Q. 7 for details).
3. Never push the dermal needle into a TMA block. This will damage the TMA block.
4. Never leave the Arraymold silicone block in hot paraffin for more than 5 minutes when making a recipient block. (Refer to FAQ Q. 3 for details)
5. Do: Make a practice TMA block first to test your skills before you attempt to cut a real one.
PREPARING ARRAY BLOCK FOR CUTTING (Watch: "Cutting a Tissue Microarray Block".
These simple steps will help you SET the punches in your paraffin Array block and create a flat surface for cutting.
1st - Once punching is complete, set the block on an uncharged slide (face down) in an oven at 37C to 45C for 3 hours up to overnight. (Different paraffins have different melting points and not all become soft at 37C. Test this process for yourself.) Once the block is softened it should be tacky and will stuck to the slide. ( Do not pull the TMA Block and slide apart.)
2nd – With Array paraffin block still warm and tacky, heat another slide in an oven to around 70C for approximately 10 minutes. Take the separate HOT slide and place under the slide stuck to your Array block. The Array paraffin block surface should turn to liquid quickly. Move the two slides around on the Array paraffin block to push any surface air bubbles away and to flatten Array block surface with the slide. This process is quick.
3rd – Remove second hot slide and place Array block with original slide (slide down) on a room temperature counter top for 10 minutes to cool. Once Array block is room temperature, place Array block and slide on an ice tray (no water) to cool for 20 minutes. Slide should remove easily from Array block and slide. Trim edges of block to flatten in needed and it should now be ready to cut.
Method to minimize damage to tissue core when extracting sample from larger needles:
Explained in the "Radical" TMA (R-TMA) Video
The disposable Dermal Needle has a small opening to insert a stylet. The opening in the 2mm is about the same as the 3, 3.5 and 4mm dermal needles. To minimize damage to your sample because of the small stylet size, we recommend using a method we call the Cardboard Punch Technique to protect your samples from damage while extracting the core. The video, Advanced Techniques, "The Radical TMA" describes in detail this technique. Please visit our videos page to watch these instructions.
Q 1. How should I store the Arraymold when it is not in use?
A. One of the unique benefits of the Arraymold is its size. It doesn't take up counter space when not in use. It is best to store the Arraymold in a dark dry place. When not in use keep the Arraymold in its box in a drawer away from chemicals and light. Do not clean the rubber mold with xylene or alcohol. It's OK to store the Arraymold with paraffin still on it.
Q 2. If I don't need the full 60 cores how do I make an array without extra holes?
A. The Arraymold can be customized to any number to whatever size is needed by filling unwanted holes in the paraffin Array block with blank paraffin cores.
Q3. What will happen if I leave the Arraymold silicone mold in paraffin for more than 5 minutes?
A. Over heating the Arraymold silicone mold may cause the small silicone core rods to swell in the hot paraffin. This can cause the cores can become loose when you create your recipient block. When taken care of, the Arraymold can create many recipient blocks. We recommend not submerging the Arraymold for over 5 minutes in 62 C paraffin when creating a recipient block.
Q 4. What is the depth of the Arraymold cores?
A. The 2 mm 60 core Arraymold is 7 mm. The 1.5 mm 150 core is 4 mm deep. The reason why the 1.5 mm core depth is not as deep as the 2 mm is because during testing we found that because 1.5 mm cores are thinner, the shortened depth cores strengthens the rods so they last longer.
Q 5. What type of Dermal Needle is required? Can I use a cheaper brand needle?
A. All needle brands are slightly different in size. We have designed the Arraymold to use a specific brand of needles. Use only Meltex or Integra brand Biopsy Punch needles and please use our stylets when removing the tissue from the needle. The needles that have a plunger inside will not work because the plastic plunger buckles when trying to extract the tissue core that is why we recommend using only our stylets.
Q 6. What is the best way to judge the core depth for creating paraffin array using the Arraymold?
A. If you need to judge your depth, the best way would be to take a Sharpe marking pen and mark the needle to the maximum depth and stay within this distance. This is especially important when punching with the 1.5 mm Arraymold needle.
Q 7. After repeated use, a few of the rubber rods in the Arraymold have broke off. Is it still possible to still use it?
A. Yes, but you will now have a blank spot in your paraffin Array or Cryoarray where the punch rods are missing. Be gentle when pulling the paraffin Array or Cryoarray block out of the array mold. Working slow and gently is the best way to keep the Arraymold rods intact.
Q 8. My Arraymold has cracked or split. Do I need to order another kit or is it possible to continue using it?
A. Yes, the Arraymold can still be used to create Array blocks. If the Arraymold cracks or splits due to repetitive use, a rubber band or tape can be used to keep the Arraymold together when paraffin or frozen embedding medium is poured into the Arraymold. To know if you can exchange your damaged Arraymold block please visit our Contact page
Q 9. How cold can I make the Arraymold before it will brake?
A. The Arraymold is optimal at -10C to -30C. DO NOT SNAP FREEZE the Arraymold instrument in liquid nitrogen or other type of frozen chemical bath. This will crack or damage the Arraymold. During testing, we have placed the Arraymold into a -80C freezer and it did become ridged, but did not crack. Once it thaws to around -30C it was flexible again. The Arraymold is designed to use in a cryostat as well as for paraffin molding. The recommended temperature range for frozen Array construction is between -10C to -30C. Snap Freezing will void your warrantee. Be gentle when pulling the embedding medium out of the Arraymold to prolong its use.
Q 10. How many paraffin arrays have technicians been able to produce from a single Arraymold before it became unusable?
A. The number of uses depends on the technician and how well the Arraymold is treated. Some labs have been able to create up to 40+ molds from one Arraymold. With proper care of the Arraymold it has the potential of giving you many arrays.
Q 11. I had difficulty pushing the stylet into the disposable dermal needle. What is the best way to insert the Stylet into the dermal needle?
A. Before using the needle, gently push and twist the Stylet down the needle before beginning an array. Sometimes plastic will come out of the dermal needle as the Stylet goes through it. This is left over plastic from manufacturing when the metal needle was pressed into the plastic handle. Once the Stylet is through the needle, push it in and out several times. Now you are ready to punch and insert cores.
Q 12. What paraffin do you recommend for paraffin array construction?
A. We have done some field-testing with histologist and found that most Histologists prefer using Paraplast X-tra, Other Histologist have used these paraffins with good results (Formula 'R' Paraffin, Blue Ribbon from Surgipath) for constructing and cutting Tissue Microarrays. These are sticky paraffin which help cores together better than harder paraffins. Some paraffins that people didn't recommend are: Richard Allen Type 9 and 3. (Type 9 and 3 are excellent for normal sectioning but not good for TMA cutting.) This is only a recommendation so please test these paraffins for yourself to know what works best for you and easiest to section.
Q 13. Is there a specific type of cryostat embedding medium you recommend for frozen arrays?
A. The best thing we would recommend is to experiment. Create a frozen array first using hotdog samples and test the embedding medium in your lab. As we hear from technicians we will try to update this section.
Q 14. I need to make an OCT Array, can I clean the Arraymold with xylene to remove the paraffin?
You can use Xylene to clean the paraffin off the Arraymold mold but do not soak it in xylene for more than a few minutes. Prolong exposure to xylene could cause the rubber to dry out and become brittle. After using xylene for cleaning you will need to remove the xylene residue from the Arraymold. This is done by dipping the rubber Arraymold in 100% alcohol, then 95% alcohol several times and eventually rinse the Arraymold in water and dry it off before using it for an OCT mold. Going from paraffin to OCT would be the only time you would need to clean paraffin off an Arraymold. If you want your Arraymold to last for years it's best to keep it chemical free. Storing with paraffin on the Arraymold is OK.
Q 15. When I was cutting my Cryoarray punches became loose. What can I do to eliminate this problem?
A. The punches need to be set into the embedding medium. This is done by melting the surface of the Cryoarray block on a metal plate and then freezing it again before sectioning it in a cryostat. Watch the "The Cryo-Tissue Microarray" video to learn more. This step may need to be repeated as you go deeper into the Cryoarray block. For further clarification review the instructional video to understand this process step by step.