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pH-sensitive lipids represent a class of lipids that can be protonated and destabilized in acidic environments, as they become positively charged in response to low-pH conditions. They can be incorporated into lipidic nanoparticles such as liposomes, which are able to change their properties and allow specific drug delivery at the acidic conditions encountered in some pathological microenvironments. In this work, we used coarse-grained molecular-dynamic simulations to study the stability of neutral and charged lipid bilayers containing POPC (1-palmitoyl-2-oleoyl-sn-glycero-3- phosphocholine) and various kinds of ISUCA ((F)2-(imidazol-1-yl)succinic acid)-derived lipids, which can act as pH-sensitive molecules. In order to explore such systems, we used a MARTINIderived forcefield, previously parameterized using all-atom simulation results. We calculated the average area per lipid, the second-rank order parameter and the lipid diffusion coefficient of both lipid bilayers made of pure components and mixtures of lipids in different proportions, under neutral or acidic conditions. The results show that the use of ISUCA-derived lipids disturbs the lipid bilayer structure, with the effect being particularly marked under acidic conditions. Although morein depth studies on these systems must be carried out, these initial results are encouraging and the lipids designed in this research could be a good basis for developing new pH-sensitive liposomes. Sin financiación 6.208 Q1 JCR 2021 1.176 Q1 SJR 2021 No data IDR 2021 UEM

The overuse of antibiotics has led to the flourishment of antibiotic-resistant bacteria and consequently to the need to develop new, more efficient pharmacological compounds. It is well known that graphene oxide (GO) doped with metallic particles exhibits broad-spectrum antimicrobial activity. In addition, in order to improve the pharmacokinetic behavior of these compounds and their solubility in biological media, polyethylene glycol (PEG) is attached to the graphene surface. Among the different available characterization techniques, molecular dynamics simulations (MD) deserve special attention, as they allow the study of different materials from a molecular point of view. In this work, MD simulations of the adsorption of small Ag and Cu clusters on pristine graphene and PEGylated graphene oxide (GO_PEG) surfaces were carried out. The results are presented in terms of adsorption energies, mean equilibrium distances between nanoparticles and graphene surfaces, radial distribution functions and diffusion coefficients of the metallic nanoclusters. These preliminary results show that PEGylation of the surface is critical to strengthen the interaction between the surfaces and the metallic clusters, which, in turn, is a key factor for improving the efficacy of these compounds UEM1915 No data JCR 2020 0.341 SJR (2020) Q3, 306/638 Materials Science (miscellaneous) No data IDR 2019 UEM

Computational modeling of the translational diffusion of water molecules in anisotropic environments entails vital relevance to understand correctly the information contained in the magnetic resonance images weighted in diffusion (DWI) and of the diffusion tensor images (DTI). In the present work we investigated the validity, strengths and weaknesses of a coarse-grained (CG) model based on the MARTINI force field to simulate water diffusion in a medium containing carbon nanotubes (CNTs) as models of anisotropic water diffusion behavior. We show that water diffusion outside the nanotubes follows Fick's law, while water diffusion inside the nanotubes is not described by a Fick's behavior. We report on the influence on water diffusion of various parameters such as length and concentration of CNTs, comparing the CG results with those obtained from the more accurate classic force field calculation, like the all-atom approach. Calculated water diffusion coefficients decreased in the presence of nanotubes in a concentration dependent manner. We also observed smaller water diffusion coefficients for longer CNTs. Using the CG methodology we were able to demonstrate anisotropic diffusion of water inside the nanotube scaffold, but we could not prove anisotropy in the surrounding medium, suggesting that grouping several water molecules in a single diffusing unit may affect the diffusional anisotropy calculated. The methodologies investigated in this work represent a first step towards the study of more complex models, including anisotropic cohorts of CNTs or even neuronal axons, with reasonable savings in computation time., We thank grants CTQ2013-47699-R, 2013/UEM11 and 2014/UEM14.