# High-quality histochemistry, immunohistochemistry, and immunofluorescence on xylene- and formalin-free paraffin-embedded tissues

## TL;DR

This paper introduces a safer tissue embedding method using supercritical CO2, avoiding toxic chemicals like xylene and formalin while maintaining high-quality pathology results.

## Contribution

The novel use of supercritical CO2 enables xylene- and formalin-free tissue embedding without compromising diagnostic quality.

## Key findings

- Supercritical CO2 embedding produces high-quality tissues suitable for histochemistry.
- The method supports immunohistochemistry and immunofluorescence without toxic chemicals.
- This technique could replace traditional methods involving carcinogenic substances.

## Abstract

Pathology is a vital part of modern medicine, playing an essential role in disease diagnosis, prognosis, and therapy choice. The field of pathology depends on traditional tissue embedding techniques, still routinely using toxic and even carcinogenic substances to process tissues for diagnostics. Chronic exposure of humans to xylene and/or formalin, two essential components in the process, may result in severe health problems. Accumulating insights resulted in a ban of formalin in Europe for multiple applications and tight restrictions for almost all other uses since its toxicity levels were upgraded to carcinogen grade 1B and mutagen grade 2. A remarkable exception to these regulations is the use of formalin in the field of pathology, because of the existing lack of formalin-free tissue embedding methods that produce high-quality pathology specimens. Here we show that a novel embedding technique employing supercritical Carbon dioxide (CO2), used in a xylene- and formalin-free manner, results in high-quality tissue samples, suitable for the fundamental techniques used in pathology: histochemistry, immunohistochemistry, and immunofluorescence.