Size‐Controlled Nanoassemblies Based on Cyclodextrin‐Modified Dextrans

Abstract

Nanoassemblies formed by host/guest interactions between two polymers in aqueous media are studied. Two types of polymers with the same dextran backbone are modified with adamantyl or βCD groups. The sizes of the spontaneously formed nanoassemblies depend on the βCD:Ada ratio and on the total concentration and composition of the mixtures. The results can be rationalized by assuming a core/shell structure of the nanoassemblies, the core resulting from associative phase separation of the two polymers and being stabilized by an external shell made of Ada-grafted dextran and containing ions adsorbed from the solution. Hydrophobic compounds such as benzophenone can be incorporated efficiently without inducing changes in properties of the nanoassemblies.

Bifunctionalized dextrans for surface PEGylation via multivalent host–guest interactions

“…It might be explained by the presence of relatively long and hydrophilic spacer in D40-GP-Ada-PEG, the latter making adamantyl groups more loosely attached and available for complexation. As in the reference (Wintgens et al, 2011), a slight decrease of K a is observed while increasing the substitution degree by Ada-groups from 5 to 10 mol%, which could be attributed to a gradual loss of their accessibility due to steric effects.…”

“…The different thermodynamic parameters derived from these experiments are given in Table 2. The association constants are as high as 4.0-6.0 × 10 4 L/mol, which is superior to previously described dextrans modified with Adagroups via simple esterification by 1-adamantanecarbonyl chloride (Wintgens et al, 2011). It might be explained by the presence of relatively long and hydrophilic spacer in D40-GP-Ada-PEG, the latter making adamantyl groups more loosely attached and available for complexation.…”

“…However this cannot fully explain the quite large adsorbed amount. As polysaccharides and polysaccharide-based nanoassemblies are typically characterized by slightly negative values of zeta potential (Wintgens et al, 2011), non-specific electrostatic interactions could also be at the origin of the enhanced interpolymer interaction. Given that, the adsorption behavior of D40-GP-Ada-PEG on the positively charged p␤CDN+-layer might be related to interplay between the host-guest and reinforced non-specific interactions in the system.…”

“…In a more recent example membrane fusion between liposomes and cyclodextrin vesicles was used to prepare hybrid assemblies comprised of liposomal core covered with layers of ␤CD amphiphiles (Versluis et al, 2014). Another way for introducing ␤CD in nanoscale drug carriers consists in assembling ␤CD polymers with "guest"-labeled amphiphilic copolymers (Ren, Chen, & Jiang, 2009;Wintgens, Nielsen, Larsen, & Amiel, 2011).…”

Hidrogeles de ciclodextrinas para administración de fármacos

“…La fase gel presenta una alta concentración de ambos polímeros, con valores de G´ y G´´ 400-500 Pa y 1200-1400 Pa, respectivamente [81,82]. Si las concentraciones de polímeros son más bajas (0.1-1% p/p) se forman partículas nanométricas de tamaño variable según el grado de sustitución del polímero con grupos que forman complejos con las CDs [83,84]. Si los polímeros cuentan con grupos ionizables, se pueden conseguir geles de viscosidad variable en función del pH del medio.…”