Lending color to dead cells -- A novel natural dye for screening cell viability: Scientists discover a natural food pigment that can distinguish between living and dead cells in cell cultures

4 min read
Synthetic dyes are commonly used to assess the toxicity of chemical compounds in cell cultures. However, these dyes damage cells, rendering the cultures useless for long-term experiments. Recently, scientists discovered that a natural food pigment can replace synthetic dyes in cell viability assays for three widely varied types of cells -- and performs better. Their approach is also environment-friendly and inexpensive, and opens up possibilities in a range of fields including drug discovery.
Conducting studies in vitro -- a Latin term that literally means "in the glass" -- is essential in the fields of medicine and biology. Working with in vitro cultures is a relatively cost-effective and easily repeatable way of gaining insight into the interactions between cells or microorganisms and specific chemical compounds, such as drugs, nutrients, and toxins. However, to properly assess the toxicity of a compound, a reliable and efficient way to distinguish live cells from cells killed due to toxicity is necessary.

Researchers have elucidated several methods to tell live and dead cells apart, and one popular approach is the "dye exclusion test (DET)" using synthetic dyes. In conventional DET, a dye such as trypan blue or methylene blue selectively permeates and stains dead cells, distinguishing them from live cells. This seems simple enough, but these synthetic dyes have been known to damage living cells in the culture as well. This renders them unusable for long-term studies with a single culture.

Fortunately, as is described in their study published in MDPI Biology, a team of scientists from the Tokyo University of Science, Japan?comprising Assistant Professor Ryoma Tagawa, Professor Yoshikazu Higami, Professor Eiji Tokunaga, and Assistant Professor Kyohei Yamashita?recently discovered an alternative to DET with synthetic dyes: DET using a natural pigment made from Monascus purpureus (MP), a mold species traditionally used in Asia for the production of fermented foods. According to Dr Yamashita, lead author of this and two other studies on MP, its discovery as a tool for distinguishing dead cells was a case of serendipity.

Dr Yamashita and a colleague were working alongside Dr Koji Yamada and Dr Kengo Suzuki from euglena Co., Ltd. to find effective ways of culturing Euglena gracilis, a type of single-cell algae, in foods, when they stumbled upon the usefulness of MP and another natural dye called anthocyanin pigment for studying…
Read full article