International Journal of Pharmaceutics 292 (2005) 43–52 PLA-PEG particles as nasal protein carriers: the influence of the particle size A. Vila a , A. S´ anchez a , C. ´ Evora b , I. Soriano b , O. McCallion c , M.J. Alonso a,∗ a Department of Pharmacy and Pharmaceutical Technology, School of Pharmacy, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain b Department of Pharmaceutical Technology, School of Pharmacy, University of La Laguna, Tenerife, Spain c Bespak Europe Ltd., Bergen Way, King’s Lynn, Norfolk PE30 2JJ, UK Received 22 July 2003; received in revised form 18 August 2004; accepted 5 September 2004 Available online 18 January 2005 Abstract Previous studies have shown that PLA-PEG nanoparticles (NP) are able to enhance the transport of the encapsulated model protein, tetanus toxoid (TT), across the rat nasal mucosa. The aim of this work was to study if the size of PLA-PEG particles affects the nasal transport of the encapsulated protein and, also, the potential contribution of blank nanoparticles to the transport of the free protein. To achieve this purpose, 125 I-TT was encapsulated into PLA-PEG particles of different sizes (200 nm, 1.5, 5 and 10 m) prepared by the water-in-oil-in-water solvent evaporation technique. Firstly, in order to investigate the carrier role of the particles, two series of either conscious or anaesthetized rats were nasally treated with 125 I-TT-loaded NP, free 125 I-TT, and a physical mixture of blank NP and free 125 I-TT. Secondly, the influence of the particle size on the nasal transport of TT encapsulated into PLA-PEG particles was evaluated in conscious rats. The amount of radioactivity recovered in the blood compartment, lymph nodes and other relevant tissues was monitored for up to 24 h. Finally, the nasal bioavailability of 125 I-TT-loaded PLA-PEG NP was calculated. The results indicated that the use of anaesthesia enhances the transport of 125 I-TT and that the physical presence of PLA-PEG NP does not affect the transport of the toxoid. In contrast, when TT was encapsulated into the particles its transport across the nasal mucosa of conscious rats was significantly enhanced. Furthermore, the efficacy of this transport was related to the particle size, reaching the most important transport for the smallest particle size. The intensity of this transport was also illustrated by the high nasal bioavailability of TT encapsulated into nanoparticles (200 nm) (F = 70–80%). These results led us to conclude that PLA-PEG NP can be accepted as nasal protein carriers for nasal administration. © 2004 Elsevier B.V. All rights reserved. Keywords: PLA-PEG; Microparticles (MP); Nanoparticles (NP); Nasal administration; Protein delivery; Vaccine delivery ∗ Corresponding author. Tel.: +34 981 594 627; fax: +34 981 547 148. E-mail address: ffmjalon@usc.es (M.J. Alonso). 1. Introduction At the beginning of the nineties, Gref et al. (1994) presented PLA-PEG nanoparticles (NP) as long 0378-5173/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ijpharm.2004.09.002