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Issue 24, 2011
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On spray drying of uniform silica-based microencapsulates for controlled release

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Although spray drying is a scalable route for particle formation with easy product recovery, a typical spray drier produces broad distributions of particles with various morphologies in a single batch, due to the non-uniform formation of droplets, wide spray trajectories, and various residence times experienced by the droplets during drying. Thus any attempt to interpret the resulting particle functionality directly in relation to their physico-chemical properties is difficult. Here, uniform silica-based microencapsulates encapsulating vitamin B12 homogenously distributed within their matrix were synthesised in a single step via a micro-fluidic-jet-spray-dryer (MFJSD), utilising a micro-fluidic-aerosol-nozzle (MFAN) for continuous generation of monodisperse droplets. We investigated the effects of lactose and Na-alginate to the properties of the silica matrix, as well as the overall particle shapes. The uniform nature of the particles allowed direct correlations between the matrix properties and the release behaviour of vitamin B12 to be observed without the complications of wide size distribution or variety of shapes. Spherical particles with relatively smooth surface were obtained with lactose addition, while incorporation of Na-alginate resulted in increasing surface roughness. Lactose accelerated the release of the encapsulated vitamin B12 (VB12), due to the relatively fast lactose dissolution that allowed buffer to penetrate deep 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 the matrix erosion, as well as due to ionic attraction to the VB12 molecules. Release kinetics data indicated diffusion as the main release mechanism independent of the microencapsulate composition. The release profiles from different compositions of the synthesized particles demonstrated good agreements with the computational predictions, highlighting the ability to modulate the release behaviour directly from the precursor compositions.

Graphical abstract: On spray drying of uniform silica-based microencapsulates for controlled release

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Publication details

The article was received on 12 May 2011, accepted on 19 Jul 2011 and first published on 14 Oct 2011

Article type: Paper
DOI: 10.1039/C1SM05879G
Soft Matter, 2011,7, 11416-11424

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    On spray drying of uniform silica-based microencapsulates for controlled release

    W. D. Wu, W. Liu, C. Selomulya and X. D. Chen, Soft Matter, 2011, 7, 11416
    DOI: 10.1039/C1SM05879G

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