Aggregation behavior of cyclodextrin and cholesterol in simulated human cerebrospinal fluid

• Different beta-cyclodextrin derivatives form aggregates with cholesterol in water.
• Aggregate size depends on the degree of substitution of cyclodextrin.
• Cerebrospinal fluid components may modify the aggregate size distribution.

A systematic study was performed to reveal the effect on the aggregation behavior of cholesterol solubilized by different cyclodextrins in aqueous media containing cerebrospinal fluid (CSF) components such as glucose, urea and inorganic salts. This study intended to mimic physiological conditions regarding concentration and temperature. Co-existing aggregated and non-aggregated structures could be detected in the studied cyclodextrin solutions containing cholesterol. It was found that the CSF components may modify the ratio of the substance being in aggregated or non-aggregated form. By tendency it was recorded that the aggregation state of randomly methylated β-cyclodextrin/cholesterol solutions were susceptible to further aggregation in the presence of CSF components, while 2-hydroxypropyl β-cyclodextrin/cholesterol associates were rather subject to de-aggregation. Larger associates formed from cholesterol and sulfobutylether β-cyclodextrin disintegrated in the presence of the additives, while the non-aggregated complex associates doubled their diameter in the presence of the ionic components of CSF. The results revealed that the interaction of different cyclodextrin derivatives with cholesterol may be modulated by these physiologically present substances.

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