Examination of time reduction method using microwave in azan staining

Abstract

Background and Aim: The azan–Mallory (azan) stain is used for identifying collagen fibers. There are two conventional methods for azan staining, namely, method I using mordants containing deleterious substances and method II without using a mordant. However, the problem with both staining methods is that the staining time is long, approximately 1 h. To reduce the time required for conventional method II, the effects of staining with microwave (MW) treatment on entering the dye were examined, while maintaining useful staining results for pathological diagnoses. Methods: Using a MW oven (output 700 W), we examined the MW treatment and staining time for each staining solution, and the staining results were compared between conventional methods I and II. Results: For staining with azocarmine G, the staining solution was allowed to stand for 5 min (shaking every 30 s) after MW treatment for 15 s. Mordanting with phosphotungstic acid was achieved after MW treatment for 10 s. For staining with aniline blue-orange G, the staining solution was allowed to stand for 7 min for liver tissue samples and 3 min for kidney tissue samples after MW treatment for 10 s. Staining results of conventional I and II methods were the same, and good staining was obtained. Conclusion: Azan staining that usually takes ≥ 1 h was reduced to approximately 10 min. This is the shortest time among the presently reported azan staining methods. This suggests that with MW treatment, the effects of enhanced molecular motion on the tissue and heating by molecular friction were obtained. In addition, this time reduction method can be used in clinical settings by obtaining rapid staining results useful for pathological diagnoses.