Silver nanoparticles in Langmuir films and their interaction with model biomembranes

MARTÍN E. VILLANUEVA; NATALIA L. PACIONI; RITA H. DE ROSSI; BRUNO MAGGIO; RAQUEL V. VICO

Carlos Paz, Córdoba

Conferencia; 13ª Conferencia Latinoamericana de Físico-Química Orgánica; 2015

Comité Latinoamericano de Fisicoquímica Orgánica

The growing number of innovations in nanomedicine and nanobiotechnology are posing new challenges to understand the full spectrum of interactions between nanomateriales and biomolecules at nano-biointerfaces. Although considerable achievements have been accomplished in vivo applications, many issues regarding the molecular nature of these interactions are far from being well-understood. In this work, we synthesized hydrophobic silver nanoparticles coated by oleic acid (AgNP-OA)1 and characterized the Langmuir films formed at the air/water interface. In addition we studied their interaction with natural saturated and unsaturated phospholipids as model biomembranes present in Langmuir monolayers. Langmuir monolayers have a rich history providing key insights into biomembranes. We use them to evaluate the interactions established between the AgNPs-OA and the phospholipids. Langmuir isotherms, compressibility modulus and compression-expansion cycles were performedto characterize the AgNP-OA films and the AgNP-OA/phospholipid mixed films. In order to access information regarding topographic features Brewster angle microscopy (BAM) was employed at the air/water interface.The films formed by spreading of AgNP-OA are stable under successive compression−decompression cycles. Furthermore, in consecutive cycles similar limiting particle areas and collapse pressures are reached indicating that negligible amount of particles are lost from the film into the aqueous subphase.In order to investigate the effects of AgNP-OA on the phospholipid monolayers a solution containing AgNP-OA and lipid was spread at the air/water interface. In all experiments, the mole fraction of nanoparticles used was XAgNP-OA = 0.0002. The phospholipids employed were 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). Interestingly, AgNP-OA mixed ideally with both phospholipids contrary to that observed for oleic acid capped magnetic nanoparticles of similar size.2 Regarding the topography, the presence of AgNP-OA induces a shape disruption of characteristic liquid-condensed domains of DPPC. In addition, With both phospholipids it is observed that nanoparticles tend to interact among themselves being segregated from the lipids in accord with the ideal thermodynamic behavior observed by Langmuir isotherms experiments.