Aggregation of hydrophobically modified polysaccharides in solution and at the air–water interface

Enhancement of the Solubility and Efficacy of Poorly Water-Soluble Drugs by Hydrophobically-Modified Polysaccharide Derivatives

“…1a) were synthesized in two steps according to the previously described procedure (20). The degree of modification (t=12 or 49) is the number of alkyl chains per 100 anhydroglucose units.…”

“…Their pH was adjusted to 7.5, corresponding to the full ionization of carboxylate groups (20). To ensure complete solubilization of the polysaccharide derivatives, the solutions were stirred at room temperature for at least 48 h. Before the experiments, they were diluted to obtain samples with concentrations ranging from 14 to 1.4Â10 j6 mg/mL.…”

“…This phenomenon was observed in a previous study and was attributed to the formation of monomolecular aggregates of the associative polysaccharides that would adsorb at the air/solution interface in a more or less condensed conformation depending on the hydrophobic chains substitution rate. At a high substitution rate such as that of CMP 49 C 8 , it is believed that most of the hydrophobic grafted chains interact within the hydrophobic core of nanoaggregates and that only few of them are able to reach the interface (20).…”

“…The advantage of the latter compared to the former, is that the hydrophobic interaction can operate not solely between different polymeric chains (intermolecular interactions) but also within a same polymer chain (intramolecular interactions) (19). It is worth noting that the balance between inter-and intramolecular interactions may easily be controlled by adjusting the size and/ or number of the hydrophobic grafted side-chains (7,20).…”

“…Pullulan is a water-soluble polysaccharide with a linear flexible chain formed from glucose and maltotriose units. Its hydrophobically modified derivatives were shown to develop spontaneous intra and/or intermolecular interactions depending on the content and length of grafted hydrophobic chains (7,8,20,28). The self-assembling properties of two hydrophobized carboxymethylpullulans (CMP 12 C 8 and CMP 49 C 8 ) varying in the substitution rate of grafted C 8 alkyl chains were characterized by fluorescence spectroscopy and by surface tension measurements.…”