Carbohydrate Polymers 89 (2012) 740–748 Contents lists available at SciVerse ScienceDirect Carbohydrate Polymers j ourna l ho me pag e: www.elsevier.com/locate/carbpol Piroxicam loaded alginate beads obtained by prilling/microwave tandem technique: Morphology and drug release Rita P. Aquino, Giulia Auriemma, Matteo d’Amore, Anna Maria D’Ursi, Teresa Mencherini, Pasquale Del Gaudio ∗ Department of Pharmaceutical and Biomedical Sciences, University of Salerno, I-84084 Fisciano (SA), Italy a r t i c l e i n f o Article history: Received 19 January 2012 Received in revised form 28 March 2012 Accepted 2 April 2012 Available online 9 April 2012 Keywords: Alginate beads Prilling Microwave treatments Drug release Drying rate Piroxicam a b s t r a c t This paper presents a tandem technique, based on the combination of prilling and microwave (MW) assisted treatments, to produce biodegradable alginate carriers of piroxicam with different drug controlled release behaviours. Results showed that alginate/piroxicam beads demonstrated high encap- sulation efficiency and very narrow dimensional distribution. Beads dried by MW retained shape and size distribution of the hydrated particles while drying rate was strongly increased compared to con- vective drying processes. Moreover, different MW irradiation regimes promoted interactions between the drug and alginate matrix, affected drug polymorphism as well as inner and surface matrix struc- ture leading to different piroxicam release profiles. High level MW irradiation led to beads with highly porous and swellable matrix able to release piroxicam in few minutes in the intestine while convective drying produced gastro-resistant beads that exhibit sustained piroxicam release (total release in 5.5 h) in intestinal environment. On these results the tandem technique prilling/MW irradiation appears to be promising to obtain alginate carrier with tailored NSAIDs release depending on drug characteristics and MW irradiation. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Polysaccharides polymers such as alginates have been investi- gated in the last years as carrier for controlled drug release (Arica et al., 2005; Del Gaudio, Russo, Rosaria Lauro, Colombo, & Aquino, 2009), cell encapsulation (Tostões et al., 2011), tissue engineering material (Aguado, Mulyasasmita, Su, Lampe, & Heilshorn, 2011), or for taste masking in paediatric formulations (Chiappetta et al., 2009). The encapsulation property of alginate is due to its ability to move from sol to gel state by ionotropic gelation under mild condi- tions through interactions with bivalent or trivalent cations (Josef, Zilberman, & Bianco-Peled, 2010). The resulting particles are able to protect drugs from environmental stress or, based on alginate pH dependent solubility, from chemical/enzymatic digestion in gas- tric fluids (Gong et al., 2011). Moreover, mucoadhesive properties of the alginate may lead to an increase in residence time and reduc- tion of drug metabolism (Elzatahry, Eldin, Soliman, & Hassan, 2009; Patil & Sawant, 2009). However, physical properties (mechanical strength, wettability, pore size and distribution) of particles are strongly influenced by both polymer characteristics and production ∗ Corresponding author. Tel.: +39 089969247; fax: +39 089969602. E-mail address: pdelgaudio@unisa.it (P. Del Gaudio). technology as well as by curing/drying step (Del Gaudio, Colombo, Colombo, Russo, & Sonvico, 2005; Hegedus & Pintye-Hódi, 2007; Wong, Chan, Kho, & Sia Heng, 2002). Alginate based beads are commonly manufactured by dropping drug–polymer solutions into a bivalent cations aqueous solution. Recently, prilling or laminar jet break-up has been applied for the beads production. This mild and easy scalable microencapsulation technique is based on the breaking apart of a laminar jet of poly- mer solution into a row of mono-sized drops by means of a vibrating nozzle device (Brandenberg & Widmer, 1998; Sakai, Sadataka, Saito, & Matsushita, 1985) that results in hydrated particles. Hydrated beads can be used as self-consistent dosage form or as building blocks in the production of controlled drug release platforms. How- ever, beads need to be dried in order to stabilize the dosage forms and to avoid microbiological degradation. Thus, the drying process has a crucial role to assure the quality of the final product. Among various drying technique, irradiation with microwaves (MW) has gained great interest in the last few years for its peculiar way of heating materials over conventional methods by inter- action of the electromagnetic waves with the irradiated matter. MW has been mainly applied in the synthesis of organic com- pounds reducing time of reactions and solvent (Kappe & Dallinger, 2006; Lidström, Tierney, Wathey, & Westman, 2001), as much as in pharmaceutical formulation design as drying or curing pro- cess (McMinn, McLoughlin, & Magee, 2005) of solid dispersions, 0144-8617/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carbpol.2012.04.003