In situ coating?An approach for particle modification and encapsulation of proteins during spray-drying

In situ coating?An approach for particle modification and encapsulation of proteins during spray-drying
Received 24 November 2005; revised 19 May 2006; accepted 24 May 2006. Available online 22 June 2006.
Jessica Elverssona, b and Anna Millqvist-Furebya
International Journal of Pharmaceutics
Volume 323, Issues 1-2 , 12 October 2006
Copyright ? 2006 Elsevier B.V. All rights reserved.
aYKI, Institute for Surface Chemistry, PO Box 5607, SE-114 86 Stockholm, Sweden
bDepartment of Pharmacy, Uppsala University, PO Box 580, SE-751 23 Uppsala, Sweden
In this paper, we present a method for in situ coating of individual protein particles in a respirable size. The aim of the coating was to influence the particle/powder properties, and to reduce or prevent surface-induced conformational changes of the protein, during spray-drying, which was the method used for simultaneously preparing and coating particles. The investigated formulations included bovine serum albumin (BSA), trehalose and either of the two non-ionic polymers, hydroxypropyl methylcellulose (HPMC) and poly(ethylene oxide)?poly(propylene oxide) triblock co-polymer (Poloxamer 188). Complete protein coating as measured by electron spectroscopy for chemical analysis (ESCA) was achieved at a polymer concentration of approximately 1% of the total solids weight, and could be predicted from the dynamic surface tension at the air/water interface, as measured by the pendant drop method. Further, particle properties such as: size, dissolution time, powder flowability, and apparent particle density, as measured by gas pycnometry, were affected by the type and concentration of the polymer. In addition, the particle surface morphology could possibly be correlated to the surface elasticity of the droplet surface during drying. Moreover, an extensive investigation (Fourier transform infrared spectroscopy, circular dichroism and size exclusion chromatography) of the structural effects of protein encapsulated in a polymeric coating suggested that in situ coating provide particulate formulations with preserved native conformation and with a high stability during rehydration.
Keywords: Polymeric particle coating; Spray-drying; Competitive surface adsorption; Dynamic surface tension; Surface morphology
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