Chemically modified inulin as encapsulation material for pharmaceutical substances by spray-drying

There is an increasing interest for adjusting release profiles for parental drug applications, oral administration and formulations. The continuous release of a drug is desirable since it is safer reference to less medications and reduced drug concentrations. This is known to enhance treatment compliance with regards to side effects, particularly for cancer treatment. The materials used for such drug delivery systems must be biocompatible particularly for in vivo applications. The drugs are normally encapsulated in biopolymers and biomaterials. Irrespective of the continuous drug delivery, the particles of the material must be biodegradable in a bid to avoid the build-up of micro and nanoparticles that can led to cytotoxic effects.

Coming up with new formulations calls for different encapsulation methods is dictated by the substance targeted attributes, material used, and application. A number of methods for particle formulation and encapsulation such as evaporation, polymerization and coacervation have been developed. Unfortunately, most of these approaches are solvent-based, which demands expensive preparation as well as purification procedures in order to realize the desired product. In addition, the use of polymers has been limited by the process parameters in the encapsulation method.

Spray-drying is a better method that allows for the processing of biopolymers in aqueous solution. In the last few years, bio-based polymers have attracted more interest owing to sustainability, economical aspects, and compliance. A few of these bio-based polymers such as casein, polyhydroxybutyrate, chitosan, and cellulose derivatives have been processed implementing the spray-drying method.

Michael Walz at University of Stuttgart, Professor Thomas Hirth at Karlsruhe Institute of Technology and Achim Weber at Fraunhofer IGB in Germany encapsulated dexpanthenol as a representative low molecular pharmaceutical component with inulin as a bio-based, biodegradable polymer implementing the spray-drying method. They also investigated the effect of inulin modifications in the release characteristic of dexpanthenol. Their research work is published in journal, Colloids and Surfaces A.

The research team first chemically modified inulin by esterification of the free hydroxyl groups with acetic anhydride and propionic anhydride. They purified the resulting polymers through precipitations and analyzed them. In the subsequent process, the authors investigated spray-drying and particle formation of native inulin, propionylated and acetylated inulin in an attempt to optimize the parameters.

The authors observed that each material delivered smooth and spherical particles with sizes ranging from 0.7 to 10 µm. Approximately 1% dexpanthenol was observed to have been encapsulated in each material and the authors compared their release characteristics in relation to chemical modification. The researchers determined the release behavior of dexpanthenol implementing the flow through cell with a dialysis adapter for micro particles.

The authors observed that inulin particles released 100% dexpanthenol after 6 hours while the implementation of chemically modified inulin derivatives gave an extended drug release. After the end of 24h, approximately 60% had been released from particles with acetylated inulin and about 10% from those with propionylated inulin.

The main objective of this study was the analysis of the side-chain modification consistent with the release profile. The authors were able to synthesize acetylated and propionylated inulin, which had high yield as well as degree of substitution.