(527g) Spray Drying of Uniform Silica Microencapsulates: Implications for Controlled Release

Spray
drying is a scalable route for particle formation with easy product recovery.
Conventional spray drying produces broad distributions of particles with
various morphologies in a single batch, due to non-uniform distribution of
droplets / spray trajectories and different residence times [1]. This renders
any interpretation of particle behaviour in relation to their physico-chemical
properties virtually impossible. Here, uniform silica microparticles
encapsulating vitamin B₁₂, which was homogenously distributed within
each particle, were synthesised in a single step via a micro-fluidic-jet-spray-dryer
(Figure 1). The dryer utilised a micro-fluidic-aerosol-nozzle for continuous
generation of monodisperse droplets from complex precursors [2]. The uniformity
of the particles allowed direct correlations between their properties and the
release behaviour of vitamin B₁₂ to be investigated, without the
complications of wide size distribution or non-uniform shapes. The effects of
additives in the forms of lactose and Na-alginate to the properties of these
microparticles were demonstrated. Spherical particles with relatively smooth
surface were obtained with lactose addition, while incorporation of Na-alginate
resulted in noticeably increasing surface roughness with higher amount added
(Figure 2). Lactose addition also accelerated the release of the encapsulated
vitamin B₁₂, due to the relatively fast lactose dissolution that
allowed buffer to penetrate into the matrix to facilitate diffusion and silica
erosion. On the contrary, Na-alginate slowed down the release considerably by
serving as an additional barrier to decelerate silica matrix erosion. Release
kinetics data indicated diffusion as the main release mechanism independent of
the additives. The release profiles from different compositions of the
synthesized particles demonstrated good agreement with computational results,
highlighting the reproducibility of particles produced with this technique and
the ability to modulate the release behaviour directly from the precursor
compositions.

References:

1.    Woo, M.W., Rogers, S., Lin,
S.X.Q., Selomulya, C., Chen, X. D., 2011, Numerical probing of a low velocity
concurrent pilot scale spray drying tower for mono-disperse particle production
- unusual characteristics and possible improvements, Chemical Engineering and Processing: Process Intensification, doi:10.1016/j.cep.2011.02.007

2.   
Wu, W., Amelia, R., Hao, N, Selomulya, C., Zhao, D.,
Chiu, Y., Chen, X. D., 2010, Assembly of Uniform Photoluminescent
Microcomposites Using a Novel Micro-Fluidic-Jet-Spray-Dryer, AIChE Journal, DOI 10.1002/aic.12489.