Abstract
In the past decades, events occurring at the nano-bio interface (i.e., where engineered nanoparticles (NPs) meet biological interfaces such as biomembranes) have been intensively investigated, to address the cytotoxicity of nanomaterials and boost their clinical translation. In this field, lamellar synthetic model membranes have been instrumental to disentangle non-specific interactions between NPs and planar biological interfaces. Much less is known on nano-biointeractions occurring at highly curved biological interfaces, such as cubic membranes. These non-lamellar architectures play a crucial -but far from understood-role in several biological processes and occur in cells as a defence mechanism against bacterial and viral pathologies, including coronaviruses infections. Despite its relevance, the interaction of cubic membranes with nano-sized objects (such as viral pathogens, biological macromolecules and synthetic NPs) remains largely unexplored to date. Here, we address the interaction of model lipid cubic phase membranes with two prototypical classes of NPs for Nanomedicine, i.e., gold (AuNPs) and silver NPs (AgNPs). To this purpose, we challenged lipid cubic phase membranes, either in the form of dispersed nanoparticles (i.e., cubosomes) or solid-supported layers of nanometric thickness, with citrate-stabilized AuNPs and AgNPs and monitored the interaction combining bulk techniques (UV-visible spectroscopy, Light and Synchrotron Small-Angle X-ray Scattering) with surface methods (Quartz Crystal Microbalance and Confocal Laser Scanning Microscopy). We show that the composition of the metal core of NPs (i.e., Au vs Ag) modulates their adsorption and self-assembly at cubic interfaces, leading to an extensive membrane-induced clustering of AuNPs, while only to a mild adsorption of isolated AgNPs. Such differences mirror opposite effects at the membrane level, where AuNPs induce lipid extraction followed by a fast disruption of the cubic assembly, while AgNPs do not affect the membrane morphology. Finally, we propose an interaction mechanism accounting for the different behaviour of AuNPs and AgNPs at the cubic interface, highlighting a prominent role of NPs’ composition and surface chemistry in the overall interaction mechanism.
Highlights
It is reasonable to assume that, in the present case, the aggregation of AuNPs on the cubic membrane occurs through a similar mechanism, i.e., though a ligand exchange between citrate anions, weakly bonded to the gold surface, and the lipids (GMO) constituting the membrane of cubosomes
This ligand exchange, driven by hydrophobic and Van der Waals forces between the gold surface and the lipid molecules, would initiate the AuNPs aggregation on the surface of cubosomes dispersed in aqueous solution (UV-Vis and SAXS data of Figure 2), and provoke the lipid extraction and substrate removal observed on solid-supported cubosomes films (Figure 6)
The interaction of inorganic NPs and biomimetic membranes has been intensively investigated to increase our fundamental knowledge on nano-bio interfaces, develop novel synthetic smart hybrid nanomaterials and to predict their biological fate
Summary
Inorganic nanoparticles (NPs) have been extensively investigated as possible building blocks for the development of therapeutic/diagnostic systems for biomedical applications: from the diagnosis and treatment of pathologies, to the recovery of damaged tissues, to the targeted, specific delivery of drugs, to the theranostics of serious diseases such as cancer, bacterial and viral infections, (Salvioni et al, 2017; Anees Ahmad et al, 2020; Yaqoob et al, 2020), the designed nanomedicine applications of inorganic NPs and, in particular, of metallic NPs, are countless (Alkilany et al, 2013; Muthu et al, 2014; Lombardo et al, 2019) Despite this extremely promising potential, the clinical translation of NPs is still very limited, due to a lack of comprehension and control of the NPs biological fate once in living organisms (Nel et al, 2009). This membrane organization plays crucial roles in several biological processes, such as membrane fusion and fission
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