Microspheres and microcapsules prepared from natural or modified natural macromolecules and biopolymers are in progress to be used for isolation, protection, storage, regeneration, or delivery purposes in various areas including biotechnology, nutrition, and medicine. The requirements concerning the final properties of the materials vary strongly. The dominant characteristics range from size, stability, permeability, durability, non-toxicity, bio-safety to biocompatibility. The requirements, in particular for biological, pharmaceutical and medical applications, are very high and often unique. Such applications are, for example, cell immobilization, immunoprotection, tissue engineering, and targeted drug delivery. Here, microspheres and microcapsules, predominantly consisting of hydrogels ranging from millimeter to sub-micron scale, form the interface between artificial and natural structures. Due to the limited possibility to engineer the biological side the adaptation must be achieved on the material’s site. The lack of fundamental structure-property-function relationships as well as insufficient material adaptation for cell encapsulation has motivated the submission of the project.
The project intends research with materials in the micro-scale range.
•Microspheres will be constructed by, primarily, physical/electrostatic network formation employing natural and/or modified natural macromolecules.
•Structure-property-function relationships will be established both in regards to the properties of the hydrogel and to possible applications as implants and for local drug delivery.
•Specific focus will be on surface characteristics as a function of chemical composition and preparation conditions, as well as application-oriented functionality.
In this context it will be studied, specifically but systematically,
•how surface morphology, surface local properties, stability, and durability are influenced by the chemical composition and the preparation conditions of the hydrogel microspheres and microcapsules,
•to which extent the microsphere and microcapsule matrix properties can be adapted to requirements of specific cell types,
•to which extend goal-directed surface design and functionalization can minimize host immune response.
The project has basic character and is materials-oriented. It is expected to establish for spherical homogeneously and heterogeneously structured hydrogels fundamental composition-preparation-properties-function relationships based on the use of highly purified comprehensively characterized already existing as well as with novel functionally equipped macromolecules, reproducible preparation conditions, and appropriately designed in vitro and in vivo experiments. These relationships may contribute to progress in cell transplantation based therapy of diseases. Materials adaptation to the requirements of microencapsulation of hepatocytes was selected as an exemplary application.
The project is collaboration between the EPFL and the University Hospital Geneva (HUG).