Hydrophobically Modified Pullulans:  Characterization and Physicochemical Properties

Abstract

Pullulan was hydrophobically modified by reaction with dodecanoic acid, modulating the polymer-to-acid ratio. The resulting products, termed PULAU N , have been characterized, and their physicochemical properties in aqueous solution, at 25 °C, are reported. The hydrophobic substitution was determined by Fourier transform infrared, FTIR, and NMR analyses. NMR also quantifies the substitution degree, N. Viscosity, surface tension, quasi-elastic light scattering, QELS, and gel permeation chromatography, GPC, methods were used to characterize the solution properties of PULAU N . Depending on the polymer concentration and N, PULAU N form micelle-like aggregates. The critical micelle concentration, cmc, decreases with increasing N. Addition of sodium dodecyl sulfate, SDS, results in the formation of mixed micelles. In the investigated concentration range, no polymer−surfactant-based gels are formed by mixing PULAU N and SDS. According to NMR self-diffusion and QELS findings, the number-average aggregation numbers of PULAU N micelles, 〈Z〉, depend on the concentration and substitution degree. Large 〈 Z〉 values are observed in the more substituted PULAU5.0. A very slow kinetics of adsorption at the air−solution interface (some days long) is observed for PULAU5.0. The effect, observed at concentrations below the cmc, is modulated by the concentration of hydrophobically modified polymer. The kinetics of adsorption is related to the combination of different effects. A thermodynamic model was developed to account for the above behavior. The process was rationalized by taking into account terms due to the surface spreading, self-diffusion, and elastic properties of the PULAU5.0 chains.

In vitro and in vivo evaluation of docetaxel-loaded stearic acid-modified Bletilla striata polysaccharide copolymer micelles

“…The BSPs (5.774 g) were dissolved in 20 mL of DMSO under stirring condition. The BSPs solution was then added dropwise to the mixed solution (15 mL) at 25°C and kept for 48 h at 38°C, as described [23]. The reaction solution was diluted 10-fold with cold ethanol.…”

Polymer–surfactant and protein–surfactant interactions

“…When the HMP chain is elastic, the intramolecular segregation cannot be ruled out a priori. It is well known, in fact, that alkyl polyacrylates (polysoaps) [86] and HMpullulans [87] form both micelle-like aggregates and mixed micelles with common ionic surfactants. Sometimes the aggregates formed by HMP require significant time to reach the equilibrium configuration [88].…”

“…Sometimes the aggregates formed by HMP require significant time to reach the equilibrium configuration [88]. Some of them show very slow kinetics of adsorption at the air-water interface, presumably due to the combination of surface spreading and elastic constraints on the polymer conformation [87]. …”

Cholesterol-Modified Amino-Pullulan Nanoparticles as a Drug Carrier: Comparative Study of Cholesterol-Modified Carboxyethyl Pullulan and Pullulan Nanoparticles

“…Because pullulan has a large amount of hydroxyl groups, it can graft small molecules such as cholesterol for hydrophobic modification and forming amphiphilic polymers [29]. As a drug carrier, cholesterol-modified pullulan (CHP) NPs can improve therapeutic efficiency because of high drug-loading and tumor-targeting [30].…”

“…Only with an appropriate range of cholesterol substitution can polymer assemble into a core-shell structured NP [29]; within this range, the greater the substitution degree, the higher the drug-loading amount [32]. We synthesized cholesterol-modified carboxyethyl pullulan (CHCP) polymer in the early stage; under the condition that the cholesterol substitution degree is suitable for CHP polymer, carboxyethyl can affect the size and drug-loading and drug-release amount of NPs [32].…”