[pt] O surfactante pulmonar é um sistema lipo-proteico que atua na interface alveolar com vital importância para manter funcional a mecânica respiratória. Os comprometimentos na sua função estão associados a diversas infecções pulmonares. Os sistemas de administração de fármacos baseados em surfactantes pulmonares derivados de animais são complexos, dificultando a compreensão do papel individual das moléculas hóspedes nas suas interações com a membrana. Aqui apresentamos uma caracterização de um extrato surfactante de pulmão porcino de grau clínico misturado com os antibióticos Levofloxacina e Claritromicina, usando uma abordagem multi-técnica – em conjunto com a metodologia de monocamadas de Langmuir– consistindo de isotermas de pressão de superfície-area, microscopia de ângulo de Brewster (BAM), espectroscopia de reflexão-absorção do infravermelho com modulação da polarização (PM-IRRAS), reflectometria de nêutrons (NR), ensaios in vitro e simulações de dinâmica molecular. Avaliou-se o efeito de ambos os antibióticos na estrutura das monocamadas de surfactantes de origem porcino bem como em monocamadas de DPPC. Foi revelado que a estabilidade / integridade das monocamadas é preservada na presença de ambas as drogas. Os sistemas mistos de antibiótico / surfactante pulmonar aumentam a atividade antibacteriana contra bactérias Gram-positivas (Bacillus cereus) e Gram-negativas (Escherichia coli). Essas descobertas fornecem novas percepções sobre a otimização de sistemas eficientes de administração de medicamentos para o tratamento de condições patológicas no nível respiratório. / [en] The lipo-proteic surfactant system acting at the alveolar interface is of vital importance for keeping functional the respiratory mechanics. Its impairments are associated with several pulmonary infections. Drug delivery systems based on animal-derived lung surfactants are complex making it difficult to understand the individual role of guest molecules in membrane interactions. Here we present a characterization of a clinical-grade porcine lung surfactant extract mixed with the antibiotics Levofloxacin and Clarithromycin, using a multi-technique approach –in conjunction with the Langmuir-monolayer methodology– consisting of surface pressure-area isotherms, Brewster angle microscopy (BAM), polarization modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS), neutron reflectometry (NR), in vitro assays, and molecular dynamics simulations. The effect of both antibiotics in the structure of porcine lung surfactant monolayers as well as in DPPC monolayers was examined. It was revealed that the stability/integrity of the monolayers is preserved in the presence of both drugs. The mixed antibiotic/lung surfactant systems enhance the antibacterial activity against Gram-positive (Bacillus cereus) and Gram-negative (Escherichia coli) bacteria. These findings provide new insights into the optimization of efficient drug delivery systems for the treatment of pathological conditions at the respiratory level.

Les particules fines émises par l'activité humaine sont la cause de diverses pathologies pulmonaires et cardiaques. Les particules de taille inférieure à 100 nm, appelées nanoparticules, sont particulièrement nocives car une fois inhalées, elles peuvent atteindre les alvéoles pulmonaires, lieux des échanges gazeux. Dans les alvéoles, les nanoparticules entrent d'abord en contact avec le surfactant pulmonaire. Ce fluide biologique tapisse les cellules épithéliales des alvéoles sur une épaisseur de quelques centaines de nanomètres et est composé de phospholipides et de protéines, les phospholipides étant assemblés sous forme de vésicules et corps multi-lamellaires. Dans ce travail, nous avons sélectionné des nanoparticules modèles de nature différente connues pour leur toxicité cellulaire (latex, oxydes métalliques, silice). Leur interaction avec un fluide pulmonaire mimétique administré aux prématurés (Curosurf®) a été étudiée en détail par microscopie optique et électronique, et par diffusion de la lumière. Nous avons mis en évidence que cette interaction est non spécifique et d'origine électrostatique. La diversité des structures hybrides obtenues entre particules et vésicules témoigne cependant de la complexité de cette interaction. En contrôlant cette interaction, nous avons formulé des particules couvertes d’une bicouche supportée de Curosurf® qui possèdent des propriétés remarquables de stabilité et de furtivité en milieu biologique.Dans une seconde partie, nous avons étudié le rôle du surfactant pulmonaire sur l’interaction entre particules et cellules épithéliales alvéolaires (A459). A l'aide d'expériences de biologie cellulaire réalisées in vitro, nous avons observé que la présence de surfactant diminue de manière significative le nombre de particules internalisées par les cellules. Dans le même temps, nous avons constaté une augmentation importante de la viabilité cellulaire. Une conclusion majeure de notre travail concerne la mise en évidence du rôle protecteur joué par le surfactant pulmonaire dans les mécanismes d'interaction des nanoparticules avec l'épithélium alvéolaire / Particulate matter emitted by human activity are the cause of various pulmonary and cardiac diseases. After inhalation, nanoparticles (ie particles smaller than 100 nm) can reach the pulmonary alveoli, where the gas exchanges take place. In the alveoli, the nanoparticles first encounter the pulmonary surfactant which is the fluid that lines the epithelial cells. Of a few hundreds of nanometers in thickness, the pulmonary fluid is composed of phospholipids and proteins, the phospholipids being assembled in multilamellar vesicles. In this work, we considered model nanoparticles of different nature (latex, metal oxides, silica). Their interaction with a mimetic pulmonary fluid administered to premature infants (Curosurf®) was studied by light scattering and by optical and electron microscopy. We have shown that the interaction is non-specific and mainly of electrostatic origin. The wide variety of hybrid structures found in this work attests however of the complexity of the phospholipid/particle interaction. In addition, we succeeded in formulating particles covered with a Curosurf® supported bilayer. These particles exhibit remarkable stability and stealthiness in biological environment. In a second part, we studied the role of the pulmonary surfactant on the interactions between nanoparticles and alveolar epithelial cells (A459). With cellular biology assays, we observed that the number of internalized particles decreases dramatically in presence of surfactant. At the same time, we found a significant increase in the A459 cell viability. Our study shows the importance of the pulmonary surfactant in protecting the alveolar epithelium in case of nanoparticle exposure