Tim Sharifsoltani

Abstract

Encapsulation of liquid bioactive ingredient formulations requires precise control of capsule size, shell thickness and mechanical stability. Conventional manufacturing techniques face limitations in achieving uniform capsules with homogeneous shells at high production rates. This project investigates an encapsulation process combining coaxial multi-fluid nozzles and the vibrating jet technique with subsequent drying. The aim is to develop a model linking material attributes, process conditions and capsule properties, enabling the rational design of capsules with non-ionic hydrocolloid shells.

Description

Capsules enclose bioactive ingredients within a shell that separates them from the surrounding environment and determines properties relevant to storage and application. For pharmaceutical dosage forms, uniform core and shell masses are essential to control the bioactive ingredient dose and shell thickness. This project aims to produce spherical capsules in the size range of 0.5–5 mm, containing lipid-based formulations within homogeneous shells.
A first step is investigating shell formulations consisting of non-ionic hydrocolloids, plasticizers and water as alternatives to gelatin-based materials. The influence of composition on viscosity, surface and interfacial tension, and the mechanical properties of the dried shell is investigated. Particular attention is given to water content, which affects both shell solidification and storage stability.
This formulation is then used to investigate capsule formation using vibrating coaxial multi-fluid nozzles. Periodic excitation induces the breakup of concentric liquid jets into core–shell droplets. The effects of material properties, nozzle geometry, excitation frequency and flow rates are studied systematically to identify conditions for uniform droplet formation. Solidification of these droplets into capsules is achieved by infrared drying.
Finally, the resulting capsules are characterized with respect to core and shell weight uniformity, mechanical strength and storage stability. Combining these investigations, the project aims to establish a comprehensive process model following the quality-by-design concept, allowing formulation and process conditions to be selected according to the desired capsule properties.