A review of curcumin as a biological stain and as a self-visualizing pharmaceutical agent

Abstract

Curcumin has been widely used to color textiles but, unlike other natural dyes such as hematoxylin or saffron, it rarely has been discussed as a biological stain. Aspects of the physicochemistry of curcumin relevant to biological staining and self-visualization, i.e., its acidic properties, lipophilicity, metal and pseudometal complexes, and optical properties, are summarized briefly here. Reports of staining of non-living biological specimens in sections and smears, both fixed and unfixed, including specimens embedded in resin, are summarized here. Staining of amyloid, boron and chromatin are outlined and possible reaction mechanisms discussed. Use of curcumin as a vital stain also is described, both in cultured monolayers and in whole organisms. Staining mechanisms are considered especially for the selective uptake of curcumin into cancer cells. Staining with curcumin labeled nanoparticles is discussed. Toxicity and safety issues associated with the dye also are presented.

Key words:

• amyloid
• boron
• cancer cells
• curcumin
• history
• lipophilic weak acid
• resin section
• review
• selective uptake
• staining mechanisms
• turmeric

Acknowledgment

RWH acknowledges the provision of facilities by Prof. Graeme Cooke, School of Chemistry, University of Glasgow, Scotland UK.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this paper.