Molecular and Structural Design of Nano-Assemblies for Controlled Release: Part A - Production and Characterisation of Nano-assemblies

Principal Investigator: Prof. M. Ghadiri
Co-Investigator(s): Dr A. Samimi, Dr Y. Ding and Dr J. Antony
Sponsor(s): Procter & Gamble
Status: Completed (2001-2004)

Abstract

Nano-particles have attracted a great attention of the industries such as ceramic-processing, coating, paints, inks, drug delivery and food processing due to their unique characteristics. However, they are difficult to be handled especially during production at industrial scale due to their small sizes. To control the handling problem of these materials, an appropriate process to consolidate the nano-particles into macro scale nano-assemblies is of potential interest for variety of industrial applications. On the other hand for many applications such as drug delivery, production of nano-assemblies with well-defined structure and size distribution is of crucial importance. In this context, kinetic and mechanism of dissolution and/or dispersion of these materials highly depends on their size and structural properties.

In view of process design of nano-assemblies with controlled release the main aim of this project is to establish the protocols for design and fabrication of nano-assemblies from primary nano-particles for a variety of applications. Various sized nano-particles are used as model materials in the work to produce 300-600 ?m nano-assemblies.

The specific objectives are:

Establishment of methodology for production of nano-assemblies at both laboratory scale and larger scales (scale-up and/or scale/out).
Investigation of interactions between primary nano-particles and mechanical properties of nano-assemblies.
Establishment of a relationship between the properties and behaviour of nano-assemblies and those of primary particles.
Investigation of the kinetics and mechanisms of disintegration and dispersion of nano-assemblies to make stabilised colloidal solution.

On the experimental side, experimental rigs is constructed, which include a unit for wet production of colloidal droplets containing dispersed nano-particles, and a temperature and pressure controlled chamber for evaporation of the liquid contained in these droplets to produce nano-assemblies. In this context two methods of freeze-drying and hot air drying is employed. The produced nano-assemblies then are subjected to the re-dispersion to investigate the effect of drying process variables (e.g. temperature, pressure of drying and size of droplets), and mechanical and structural characteristics of nano-assemblies on stability of nanoparticles in the colloidal system. Furthermore the effect of the properties of original colloidal solutions is investigated on the characteristics of dried nano-assemblies and consequently on the re-dispersion behaviour of these materials.

Figure: a) schematic drawing of freeze-drying process, b) and c) high-speed video recordings of Latex spray at 0 kV and 6 kV d) and e) tomography of the freeze-dried silica and latex nano-assemblies respectively.