Smart Drug Delivery Using PMDA-Crosslinked β-Cyclodextrin Carriers

Introduction

Cyclodextrins (CDs), a family of cyclic oligosaccharides produced from starch via enzymatic conversion, possess a unique structure composed of a hydrophobic inner cavity and a hydrophilic exterior. Among them, β-cyclodextrin (β-CD) is widely used due to its cost-effectiveness and favorable inclusion complexation properties. Despite their beneficial features, native CDs often exhibit limitations such as poor aqueous solubility, low complexation stability, and rapid clearance in biological systems. To overcome these challenges, researchers ^[1] have developed crosslinked β-CD-based polymers—often referred to as cyclodextrin nanosponges—which provide improved drug encapsulation efficiency, stability, and controlled release profiles.

Polymer Design and Crosslinking Strategy

The synthesis of β-cyclodextrin polymers (CDPs)was achieved using pyromellitic dianhydride (PMDA) as a bifunctional crosslinker^[1]. PMDA contains two anhydride groups capable of reacting with hydroxyl groups on β-CD, leading to the formation of ester linkages and the development of a three-dimensional polymeric network. The reaction was carried out in a dimethyl sulfoxide (DMSO) medium in the presence of triethylamine (TEA), which facilitated the esterification process.

Through this crosslinking reaction, β-CD units become interconnected, forming a porous, hyperbranched polymer matrix capable of both inclusion and non-inclusion interactions with drug molecules. The resulting CDPs exhibit enhanced aqueous dispersibility and structural integrity compared to native CDs, thus presenting a suitable platform for drug delivery applications.

Structural Features and General Properties

The polymerization process leads to structural changes in the CD matrix, including a reduction in crystallinity and the introduction of more accessible interaction sites for guest molecules. These features contribute to the superior performance of CDPs as drug carriers.

Preliminary observations revealed that CDPs synthesized under selected conditions possessed nanometric dimensions with stable colloidal behavior. Their porous morphology facilitates high surface area interactions, which is particularly advantageous for drug loading and release. Furthermore, the presence of abundant hydroxyl and carboxyl functionalities within the polymer matrix enhances hydrophilicity and provides potential sites for hydrogen bonding with guest molecules.

Application as a Drug Carrier: Ketoprofen Loading

To evaluate the potential of CDPs as drug carriers, ketoprofen (KP)—a poorly water-soluble, non-steroidal anti-inflammatory drug—was used as a model compound ^[1]. The loading process was carried out by mixing CDPs with KP in an isopropanol–water system under controlled stirring and temperature conditions. Drug loading was primarily achieved through adsorption and inclusion within the polymer network.

The results demonstrated that CDPs could effectively encapsulate ketoprofen, with encapsulation efficiency influenced by several experimental factors. Among them, the mass ratio of KP to CDP played a notable role, with optimal performance observed at a moderate loading ratio. Moreover, the loading process was found to be time-dependent, suggesting a gradual establishment of equilibrium between free and encapsulated drug fractions.

Alfa Chemistry specializes in the supply of high-quality cyclodextrins and cyclodextrin-based compounds, including β-cyclodextrin, crosslinked cyclodextrin polymers, and functionalized derivatives. If you are interested in sourcing cyclodextrins or exploring custom solutions for complex formulation challenges, please feel free to contact us for product details, technical support, and collaboration opportunities.

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