Research paper New spray congealing atomizer for the microencapsulation of highly concentrated solid and liquid substances Beatrice Albertini a, * , Nadia Passerini a , Franco Pattarino b , Lorenzo Rodriguez a a Dipartimento di Scienze Farmaceutiche, Universita ` di Bologna, Bologna, Italy b DISCAFF, Universita ` del Piemonte Orientale, Novara, Italy Received 19 July 2007; accepted in revised form 20 September 2007 Available online 24 October 2007 Abstract A new pneumatic atomizer for spray congealing, called wide pneumatic nozzle (WPN), was developed. To evaluate its performance, microparticles containing highly concentrated either solid drug (Propafenone hydrochloride, PRF) or liquid nutraceutical (Vitamin E, VE) have been prepared and characterized. The results showed that the spray congealing nozzle enabled the production of spherical and not aggregated microparticles with high yields (95% w/w) and relatively narrow size distributions; moreover, increasing the viscosity of the suspension from 50 to 500 mPa s, the particle size increased. The loading of the drug was high for microspheres (50% for PRF and 30% for VE) and the encapsulation efficiency was good for all formulations. The drug release was easily modified according to the nature of the used excipients, as both lipophilic (carnauba wax, cetearyl and stearyl alcohols) and hydrophilic (PEG 4000) carriers were employed. Moreover the results evidenced that it was possible to encapsulate actives (VE) that are in a liquid form and to enhance their availability. In conclusion the developed spray congealing nozzle was able to nebulize very viscous systems that are usually not processed by conventional apparatus and to produce microspheres with high and uniform drug content. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Spray congealing; Air pressure nozzle; Microparticles; Propafenone hydrochloride; Vitamin E acetate 1. Introduction In recent years, microencapsulation has been used in several fields such as pharmaceutical, veterinary, cosmetic and agricultural as well as in food and food additives [1]. The most popular technologies used to prepare microparti- cles are coacervation, solvent evaporation, fluid bed coat- ing, extrusion coating, spray drying and spray congealing [2]. Actually, the spray congealing technique (alternatively called spray chilling or spray cooling) is gaining consider- able attention, especially from the view point of safety and of rapidity. In fact the spray congealing technique atomizing a solution or a dispersion of the drug into a mol- ten carrier, which melts at a relatively low temperature (45– 75 °C), overcomes the problem of residual solvents and the atomized droplets quickly solidify due to their exposure to an ambient air flow. Recent developments in spray con- gealing apparatus include the use of congealing chambers with integrated bag filters for cooling and separation of product in one unit. This design is very compact and thus space-saving [3]. In the last decade, several papers focused the attention on the possibility of producing solid lipid microparticles (SLMs) by spray congealing [4] to form sus- tained-release matrices [5–8] and to mask the bitter taste of some antibiotics [9–11]. Recently a spray congealing pro- cess for the preparation of protein loaded SLM was devel- oped, showing that this technology is also a promising approach for the microencapsulation of proteins sensible to degradation, as for instance insulin [12]. The performance of the spray congealing process strictly depends on the atomization efficiency of the molten mix- ture, which may be sprayed using different types of devices, traditionally divided into rotary (or centrifugal) atomizers, 0939-6411/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.ejpb.2007.09.011 * Corresponding author. Dipartimento di Scienze Farmaceutiche, Uni- versita ` di Bologna, Via San Donato 19/2, 40127 Bologna, Italy. Tel.: +39 0512095607; fax: +39 051245082. E-mail address: beatrice.albertini@unibo.it (B. Albertini). www.elsevier.com/locate/ejpb Available online at www.sciencedirect.com European Journal of Pharmaceutics and Biopharmaceutics 69 (2008) 348–357