Encapsulation has been developed as a tool for the transport of cells or proteins into the human organism. The therapeutic potential of encapsulated cells or proteins is promising for treating patients who suffer from tissue loss, neurodegenerative disorders, diabetes, liver failure, and other diseases caused by specific vital cellular dysfunctions.

Because of their hollow structure, such polymeric spheres can encapsulate large quantities of guest molecules or large guests within the empty domain. However, those self-assembly hollow spheres lack biocompatibility and non-biodegradability because the rod-like blocks are π-conjugated long chains formed by synthesis method.

For responding this challenge, Prof Dr LI Bang-Jing’s group at CAS Chengdu Institute of Biology (CIB, CAS) and Prof Dr Sheng Zhang at State Key Laboratory of Polymer Materials Engineering, Sichuan University (SKLPME, SCU) have applied the inclusion complexes of alginate-graft–PEG and a-CD as a rigid block to improve the biocompatibility and biodegradability of such self-assembly hollow spheres in previous reports.

In their systems, a-CD rings are stacked along the graft PEG axis to form a channel-type crystalline structure, meanwhile, since the good water solubility of alginate, the alginate-g-PEG/a-CD complexes have both a rod block (PEG-a-CD) and a coil block (alginate backone), in their selective solvent (water), the rod-like block in the rod-coil system preferred crowded parallel packing and resulted in the formation of hollow spheres for necessary of the efficient space-filling packing.

With the formation of insoluble inclusion blocks, water became a selective solvent, so hollow spheres were formed. This method not only avoided the use of synthesized rod polymers, but also was expected to broaden the list of hollow assemblies because a wide range of polymers have been reported to form rod-like inclusion complexes with CDs.

Thus, Prof Dr Li and Prof Dr Zhang’s research not only enriches the preparation methods of biocompatible hollow nanospheres, but also well demonstrates the relation between the physical properties and the environmental conditions of such hollow sphere system. Main findings of those studies have been published on Langmuir 2011 doi: 10.1021/la2028803.