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Anionic Polyelectrolyte-Induced Aggregation of Basic Orange 21: A Clue toward Metachromasia
Gaurav Singh1, Shrishti P Pandey2,3, Prabhat K Singh3,4
1UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai, Kalina, Santacruz (E), Mumbai 400098, India.
The Journal of Physical Chemistry. B
|June 17, 2021
Summary
Basic Orange 21 (BO21) dye exhibits metachromasia in leukocytes, aiding cell counting. Polystyrene sulfonate (PSS) induces BO21 aggregation, explaining its spectral shifts in biological environments.
Area of Science:
- Photophysics
- Biomedical Optics
- Dye Chemistry
Background:
- Metachromasia, a color change in chromophores within biological tissues, is observed with dyes like Basic Orange 21 (BO21).
- BO21 is a cationic dye used as a supravital stain for leukocyte differential counting due to its metachromatic properties.
- Understanding the spectral shifts of BO21 in cellular environments is crucial for its application in diagnostics.
Purpose of the Study:
- Investigate the impact of synthetic anionic polyelectrolyte, polystyrene sulfonate (PSS), on the photophysical properties of BO21.
- Elucidate the factors contributing to the spectral shift and metachromatic behavior of BO21 in biological contexts.
- Characterize the aggregation behavior of BO21 and its response to external stimuli.
Main Methods:
- Steady-state emission spectroscopy
- Ground-state absorption spectroscopy
- Time-resolved emission spectroscopy
- Fluorescence upconversion spectroscopy (subpicosecond resolution)
Main Results:
- Polystyrene sulfonate (PSS) induces aggregation of Basic Orange 21 (BO21) molecules.
- Aggregation leads to significant alterations in BO21's photophysical properties, including spectral shifts.
- BO21 aggregates demonstrate responsiveness to external stimuli like temperature and salt concentration.
- Excited-state lifetime of BO21 was estimated using fluorescence upconversion spectroscopy.
Conclusions:
- BO21 aggregation is the likely mechanism behind its spectral shifts and metachromatic behavior in cellular environments.
- The sensitivity of BO21 aggregates to external factors supports the proposed aggregation mechanism.
- This study provides insights into the photophysical behavior of BO21, relevant for its use in leukocyte analysis.
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