Contents lists available at ScienceDirect The Journal of Supercritical Fluids journal homepage: www.elsevier.com/locate/supflu Development of PLGA dry powder microparticles by supercritical CO 2 - assisted spray-drying for potential vaccine delivery to the lungs Márcia Tavares a , Renato P. Cabral a , Clarinda Costa a , Pedro Martins b , Alexandra R. Fernandes b , Teresa Casimiro a, ⁎ , A. Aguiar-Ricardo a, ⁎ a LAQV–REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal b UCIBIO–REQUIMTE Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal ARTICLE INFO Keywords: Dry powder inhalation Pulmonary drug delivery Poly(lactic-co-glycolic acid) Supercritical assisted atomization DOE ABSTRACT In this work, biocompatible and biodegradable poly(D-L-lactide-co-glycolide) (PLGA) composite microparticles with potential use as carrier for vaccines and other drugs to the lungs were developed using supercritical CO 2 - assisted spray-drying (SASD). Bovine serum albumin (BSA) was chosen as model vaccine, and L-leucine as a dispersibility enhancer, and their effects on the particle characteristics were evaluated. The dry powder for- mulations (DPFs) were characterized in terms of their morphology and aerodynamic performance using an in vitro aerosolization study – Andersen cascade impactor (ACI) - to obtain data such as the fine particle fraction (FPF) with percentages up to 43.4%, and the mass median aerodynamic diameter (MMAD) values between the 1.7 and 3.5 μm. Additionally, pharmacokinetic and cytotoxicity studies were performed confirming that the produced particles have all the necessary requirements for potential pulmonary delivery. 1. Introduction The local application of drugs to the respiratory tract via inhalation facilitates a site specific treatment of lung diseases with higher treat- ment efficacy, lower systemic exposure and consequently, reduced side effects [1,2]. It is also an advantageous route for systemic drug delivery since it shows a high solute permeability which facilitates gas exchange via diffusion [3], due to its very thin absorption membrane (0.1–0.2 μm), to its elevated blood flow (5L/min) and to the highly vascularized alveolar epithelium constituted by a single layer of cells, which offers a large absorptive surface (80–100 m 2 ) [4–6]. It also has an easy administration, shows early effects of drugs’ pharmacological actions and has no risk of drug decomposition [7,8]. Furthermore, unlike the oral route, it is not subject to first pass metabolism which is especially important to macromolecules (i.e. peptides and proteins) that are easily degraded by enzymes [9]. Controlled drug release systems composed of polymeric materials with particular characteristics, such as biocompatibility and degradability, have been shown to improve the pharmacokinetic and pharmacodynamic profiles of encapsulated drugs in the lung [1,7,10]. Vaccines are responsible for death prevention associated with nu- merous infection diseases every year, even though there is still a huge amount of children morbidity due to vaccine-preventable diseases [11]. Vaccines administered parenterally require expensive cold chain transport and trained personnel, and they can induce needle-stick in- juries with possible transmission of viruses [12,13]. To treat the in- fectious diseases that affect poor populations the vaccines should be simple, cheap, easy to produce and stable. This is all possible with pulmonary vaccination added to all the advantages for drug delivery already mentioned [14]. Above that is the fact that the lungs have gained a lot of attention given that the respiratory tract is the main entry of pathogens and also it has an extensive dendritic cell network lining the airway epithelium that facilitates a first line of defence for antigens [15]. To efficiently deliver powder formulation to the lungs, an inhaler should generate an aerosol of a suitable size with a reproducible drug dosing while ensuring chemical stability and activity [5]. The dry powder inhaler (DPI), presents all these characteristics, being also propellant-free [16,17]. As for the delivery of vaccines this device is very suitable once macromolecules (polysaccharides, proteins and peptides) tend to degrade when in a liquid solution and so are provided with a greater stability [12]. In order to understand where particles with different size deposit in the respiratory tract, the aerodynamic diameter (d a ) has to be taken into account and is defined by the equation = √ d d ρ ρχ a g p o http://dx.doi.org/10.1016/j.supflu.2017.06.004 Received 5 March 2017; Received in revised form 6 June 2017; Accepted 7 June 2017 ⁎ Corresponding author. E-mail addresses: teresa.casimiro@fct.unl.pt (T. Casimiro), air@fct.unl.pt (A. Aguiar-Ricardo). The Journal of Supercritical Fluids 128 (2017) 235–243 Available online 08 June 2017 0896-8446/ © 2017 Elsevier B.V. All rights reserved. MARK