Sokolka went through electron microscopy, and serratia tests.

How do we know that?

I found a Polish newspaper article suggesting the research was amateurishly performed and should have been more extensive. I used the auto-translate feature that my browser has, I can't guarantee accuracy.

https://www.rp.pl/kosciol/art7471901-co-sie-naprawde-stalo-w-sokolce

What kind of research did Professor Sulkowski perform? It's unclear exactly. He enigmatically replies that it fell within the scope of his specialty.

However, he refuses to say how the nuclei were arranged in the fiber of the tissue he examined. "Such questions fall within the purview of the appropriate commission investigating the miracle," he says, cutting the conversation short.

DNA testing would precisely indicate whether the tissue being examined is human or animal, and whether it's male or female. "We would determine with a high degree of probability what region of the world it comes from. We would dispel any doubts," assures Professor Śliwka.

Prof. Chyczewski: – The Archbishop was not interested in conducting such research. I was told that since the material was believed to be of miraculous origin, there was no need to bother with it any further.

Did he even publish his results? There should be images, evidence. So far we still just have claims.