Natural Dyes Are Making a Comeback

For decades, synthetic dyes have dominated scientific industries. However, a growing awareness of the environmental impact and potential health hazards associated with these artificial dyes/pigments is fueling a resurgence of interest in natural dyes. The global market for natural dyes is showing a growth rate of 11% in 2024 (Arizton, 2021).  Among these, logwood, derived from the Haematoxylum campechianum L. tree, stands out for its rich history, vibrant colors, and crucial role in histology.

The Logwood Tree Legacy

Native to Central America, the Logwood tree holds a significant place in dyeing history. Its heartwood contains haematoxylin, a compound that, when oxidized, yields haematein, the active coloring agent. Logwood’s rise to prominence began in the 17th century, becoming a highly sought-after commodity in Europe for dyeing textiles, especially for dark shades. Beyond textiles, logwood has found a vital application in histology. When combined with a mordant, typically aluminum salts, hematoxylin stains cell nuclei a characteristic blue-purple color. This technique is most utilized in Hematoxylin and Eosin (H&E) staining.

Significance in Staining

Hematoxylin’s significance in scientific staining cannot be overstated. Its ability to selectively stain nuclear components makes it an indispensable tool for:

• Education: H&E staining provides a clear and easily interpretable view of cellular structures, making it an excellent teaching tool in histology and pathology courses.
• Diagnosis of Diseases: Pathologists rely heavily on H&E staining to identify abnormal cellular structures indicative of disease, including cancer.
• Research: Researchers use hematoxylin staining to study tissue architecture, cellular organization, and the effects of various treatments on tissues.

The Future of Hematoxylin

Despite its long history, hematoxylin continues to be a vital tool in modern science. Interestingly, the base technique remains unchanged since its inception, demonstrating how robust the staining process is. What has changed, however, is how we interpret the staining information.

• Cancer Diagnosis: Digitalized histological sections with H&E staining and deep analysis of images by convolutional neural networks are used to recognize structures in the image, producing a more robust evaluation in less time (Kobayashi et al., 2021; Litjens et al., 2016; Xiao et al., 2019).
• Organ Morphogenesis: H&E staining is also applied in studies regarding human organ morphogenesis, using serial images from H&E stain to make 3D reconstructions; this application of hematoxylin has been useful in monitoring the development of tissues and structures that form the kidney (Sims-Lucas, 2012).

New Applications for Hematoxylin

• Biosensors: Hematoxylin’s electrochemical properties are used in biosensors to detect substances like NADH, hydrazine, acetaminophen, HPV, DNA mutations, GMOs, and pathogens. ​
• Textile Industry: Hematoxylin is a promising natural dye, with new eco-friendly mordants being developed to reduce environmental pollution. ​
• Replacement: Hematoxylin could be investigated as a replacement for synthetically made blue nuclei dyes.

Hematoxylin, with its rich history and enduring relevance, stands as a testament to the power of simple yet effective scientific tools. From its origins in the heartwood of a tropical tree to its indispensable role in modern diagnostics and research, hematoxylin continues to shape our understanding of the microscopic world.

References

Arizton. (2021). Natural dyes market – global outlook and forecast 2019–2024. Retrieved 9/20 from https://www.researchandmarkets.com/research/zdhzms/the_global_market?w=4

Kobayashi, S, Saltz, JH, & Yang, VW. (2021). State of machine and deep learning in histopathological applications in digestive diseases. World J Gastroenterol, 27(20), 2545-2575. https://doi.org/10.3748/wjg.v27.i20.2545

Litjens, G, Sanchez, CI, Timofeeva, N, et al. (2016). Deep learning as a tool for increased accuracy and efficiency of histopathological diagnosis. Sci Rep, 6, 26286. https://doi.org/10.1038/srep26286

Sims-Lucas, S. (2012). Analysis of 3d branching pattern: Hematoxylin and eosin method. Methods Mol Biol, 886, 73-86. https://doi.org/10.1007/978-1-61779-851-1_7

Xiao, QE, Chung, PC, Tsai, HW, et al. (2019). Hematoxylin and eosin (h&e) stained liver portal area segmentation using multi-scale receptive field convolutional neural network. IEEE Journal on Emerging and Selected Topics in Circuits and Systems, 9(4), 623-634. https://doi.org/10.1109/JETCAS.2019.2952063

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