Video narration script:

Hi everyone. Welcome to this Arraymold video on preparing an array block for cutting.

Once the Arraymold is warmed up in a paraffin bath, place it on an ice plate or ice tray and add the cassette.

I am using freeze spray to spray around the cassette so I can create a paraffin seal. Fill the cassette to the top with paraffin. This will give you a solid paraffin block for creating your Tissue Microarray.

Always use infiltration/embedding type paraffin. When people ask me what is the best brand of paraffin to use I always tell them to use what you are use to cutting with. Since cutting is the most important part of TMA construction, getting a good section is most critical.

Before I pull the Arraymold from the paraffin block, I like to wait till they are both at room temperature. Reason being, is the Arraymold will be softer and more flexible and the cores will last longer. Pulling them apart when the rubber is stiff and cold could break some of the core rods out of the Arraymold.

The Arraymold we are using here is one of our first created, as you can see it came to us with one short core rod in it. Since we couldn’t sell it, we have been using it for testing. In the last three years I believe we have made around 40 to 50 paraffin arrays from this single Arraymold.

Filling your Array block once it is at room block is at room temperature will reduce the chance of it cracking. You can flatten the punches out from time to time by either pressing a glass slide on the array block surface or flipping the block over and pressing it gently on the surface of a counter top.

Now we can begin to set the punches. Warm an oven to around 43 degrees Celsius. Place the Array block on a glass slide face down. It doesn’t matter if it’s a charged or a non-charged slide.

Some people leave the Array block in the oven over night to soften and set the paraffin and tissue cores, but we have found that 2 to 4 hours works just as well. You may want to test this for yourself because some tissue might need more setting time.

Now you will need to remove the Array block and slide from the oven. Do not separate the block and slide yet. You will need to heat up another slide to around 70 to 80 degrees Celsius by its self. I’ll explain why in a moment.

Since I only have one oven, the Array block needso stay warm and soft while the singe slide is heating up in the oven. I’m placing the array block and slide together on the edge of my water bath. It’s warm enough to keep the block soft while the single slide is heating up. Don’t put the array block too close to the glass dish. This area is extremely hot and will definitely melt your Arrayblock. Please test this procedure with a blank paraffin block on a slide if you are going to use this technique to make sure it works for you.

Carefully remove the hot slide from the oven and place it on top of the slide stuck to the Array bock. You will see the surface of the Array block paraffin liquefy. The two slides will be able to move around together. This sets the surface of the Arrayblock and gets rid of any air pockets. Once liquefied, quickly remove the hot slide and flip the Array block and slide over on a counter top to cool together to room temperature, which take approximately 10 to 15 minutes. Once at room temperature, place them together on a cold plate or Ice tray for at least 15 more minutes to cool. Now the slide should come away from the array block easily.

Trim the edges of your Array block to make them clean and even.

I’m not going to cover cutting procedures because there are as many techniques as there are histologists. First trim into the Array block to get a flat surface. If your microtome chuck is at a different angle then your Arrayblock, you may want to adjust your chuck so it is flat with the block. You don’t want to cut away valuable tissue facing into the Array block. Once you have trimmed into the block, put the block back on your ice tray and move the blade to a new area or change the blade.

You can see in the tissue ribbon some of the punch cores are missing. Actually they have curled. This is common when cutting an Array block. When you lay the ribbon on a water bath they usually flatten back out.

Thanks for watching I hope these techniques help with your Tissue Microarray construction. And thank you for choosing The Arraymold.

Video Corrections:

Since producing this video we have learned from Histologists and TMA Techs that Paraplast X-Tra is a better paraffin for constructing and cutting TMAs. We do not recommend the paraffin shown in this video for TMA constuction and sectioning.

Richard Allen Type 3 or 9 are excellent paraffins for normal sectioning but not for TMA construction and sectioning.

Here are some comments regarding paraffins recommended by Histologist and TMA Technicians.

Paraplast X-TRA from Leica. "Sticky for better punch setting and cuts nicely."

Blue Ribbon from Surgipath. "Handles the post arraying steps better and I like the contrast color while punching. It cuts nicely too."