Auto-assemblies of Alpha-Cyclodextrin and Grafted Polysaccharides: Crystal Structure and Specific Properties of the Platelets

TL;DR

This study investigates the crystal structure and properties of auto-assembled platelets formed from alpha-cyclodextrin and grafted polysaccharides, revealing layered crystalline structures and potential biomedical applications.

Contribution

It provides detailed structural and thermal characterization of novel alpha-cyclodextrin-polysaccharide platelets, highlighting their layered crystalline arrangement and properties.

Findings

Layered crystalline structures intercalate polysaccharide backbones and CD complexes.

Crystals exhibit monoclinic symmetry with head-to-tail CD arrangement.

Platelets have variable sizes, shapes, and melting temperatures exceeding 100°C.

Abstract

Cyclodextrins (CD) are a family of oligosaccharides with a toroid shape, which exhibit a remarkable ability to include guest molecules in their internal cavity providing a hydrophobic environment for poorly soluble molecules. Recently new types of inclusions of alpha CD with alkyl grafted polysaccharide chains (pullulan, chitosan, dextran, amylopectin, chondroitin sulfate) have been prepared which are auto assembled into micro and nano platelets. We report in this paper an extensive investigation of platelets with different compositions, including their reversible hydration (Thermo Gravimetric Analysis), crystalline structure (Powder X Rays Diffraction), dimensions and shapes, (Scanning Electron Microscopy Field Emission Gun), thermal properties, solubility and melting (Micro Differential Scanning Calorimetry). The crystalline platelets exhibit layered structures intercalating the polysaccharide backbones and CD complexes hosting the grafted alkyl chains. The monoclinic symmetry of columnar type crystals suggests a head to tail arrangement of the CDs. The platelets have a preferentially hexagonal shape with sharp edges, variable sizes, and thicknesses and sometimes show incomplete layers (terraces). The crystal parameters change upon dehydration. Melting temperatures of platelets in aqueous solutions exceeds 100 degree. Finally, we discuss the potential relation between the platelet structure and applications for mucoadhesive devices.