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Physical factors affecting chloroquine binding to melanin
R L Schroeder1, P Pendleton1, J P Gerber1
1School of Pharmacy and Medical Sciences, University of South Australia, North Terrace, Adelaide 5000, Australia.
This study reveals how temperature, pH, and melanin type affect chloroquine binding to melanin, a key factor in drug-induced retinopathy. Understanding these interactions is crucial for managing long-term chloroquine therapy risks.
Area of Science:
- Biochemistry
- Materials Science
- Pharmacology
Background:
- Chloroquine, an antimalarial, is used for rheumatoid arthritis.
- Long-term use risks retinopathy due to chloroquine accumulation on ocular melanin.
Purpose of the Study:
- Investigate factors influencing chloroquine adsorption by melanin.
- Determine the impact of pH, temperature, melanin type, and particle size on chloroquine-melanin interactions.
Main Methods:
- Compared chloroquine adsorption on Sepia and bovine eye melanins.
- Analyzed adsorption isotherms and isosteric heat.
- Evaluated the influence of pH, temperature, and buffer cations.
Main Results:
- Increased pH (4.7 to 7.4) enhanced chloroquine affinity for all melanins.
- Isosteric heat analysis indicated competitive interactions, not solely strong binding.
- Buffer cations competed with chloroquine at low surface coverage.
- Temperature influenced melanin structure, promoting chloroquine adsorption via cation displacement.
Conclusions:
- Melanin's interaction with chloroquine is complex and influenced by environmental factors.
- pH and temperature significantly modulate chloroquine binding to melanin.
- Understanding these factors is vital for predicting and mitigating chloroquine-induced retinopathy.
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