title: Structural analysis of nanosystems: Solid Sorbitan esters Nanoparticles (SSN) as a case study.
abstract: Innovative approaches in nanotechnology can provide drug delivery systems with a high potential in different fields. To avoid trial and error assays as a main driving force governing new designs and, furthermore, to develop successful nanosystem optimization strategies, it is of the greatest importance to develop specific characterisation techniques beyond conventional determinations of size, zeta potential and morphology. However, the application of techniques able to determine some key characteristics, such as nanostructure (i.e., solid structure vs vesicular), and the way in which the reorganization of components takes place on these structures has been scarcely explored. The present work has been devoted to provide some insights about the potential offered by some NMR techniques to those scientists working on nanotechnological approaches. For this purpose, we selected our nanosystems based on sorbitan monooleate as a case study. We used (1)H NMR methods, including a recently proposed method relying in the well-known Saturation Transfer Difference (STD) experiment for the observation of 'invisible signals' in large aggregates (Invisible State STD or ISSTD). Overall, these techniques revealed the presence in these nanosystems of a gradient of flexibility from an internal rigid core towards a more flexible region located on their surface, as well as the absence of water content in both regions. Such structure, corresponding to a solid nanostructure rather than a vesicular one, can explain some of the interesting properties previously observed for these innovative nanosystems, such as their high stability, and allows us to refer to these nanosystems with the term "Solid Sorbitan esters Nanoparticles" (SSN). On the basis of the valuable information provided by the mentioned characterisation techniques, it is our understanding that they could facilitate the future design of new drug delivery nanosystems as well as the improvement of existing ones and/or the development of new applications for classical drug delivery concepts.
authors.affiliation: Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, Universidade de Santiago de Compostela, Campus Vida, 15782 Santiago de Compostela, Spain.
authors.forename: Andrea
authors.initials: A
authors.lastname: Pensado
authors.affiliation: Nuclear Magnetic Resonance Unit, RIADT, Universidade de Santiago de Compostela, Campus Vida, 15706 Santiago de Compostela, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Martín-Pastor
authors.affiliation: Faculty of Pharmacy, Federal University of Rio Grande do Sul (UFRGS), Av. Ipiranga 2752, 90610-000 Porto Alegre, RS, Brazil.
authors.forename: Giovanni K
authors.initials: GK
authors.lastname: Zorzi
authors.affiliation: Faculty of Pharmacy, Federal University of Rio de Janeiro, Av. Aluisio da Silva Gomes 50, 27930-560 Macaé, Brazil.
authors.forename: Edison S
authors.initials: ES
authors.lastname: Carvalho
authors.affiliation: Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, Universidade de Santiago de Compostela, Campus Vida, 15782 Santiago de Compostela, Spain; Genetics and Biology of the Development of Kidney Diseases Unit, Sanitary Research Institute (IDIS) of the University Hospital Complex of Santiago de Compostela (CHUS), Travesía da Choupana, s/n, 15706 Santiago de Compostela, Spain. Electronic address: alejandro.sanchez@usc.es.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Sanchez
mesh_terms: D004952:Esters; D009682:Magnetic Resonance Spectroscopy; D046529:Microscopy, Electron, Transmission; D015394:Molecular Structure; D053758:Nanoparticles / Q000737:chemistry*; D011136:Polysorbates / Q000737:chemistry*
chemical_list: D004952:Esters; D011136:Polysorbates
keywords: ISSTD; Invisible State STD; Nanoparticles; Saturation Transfer Difference; Sorbitan esters; Sorbitan monooleate; WaterLOGSY