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    The role of PEG conformation in mixed layers: from protein corona substrate to steric stabilization avoiding protein adsorption

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        Abstract

        Although nanoparticles (NPs) have been traditionally modified with a single ligand layer, mixture of ligands might help to combine different functionalities and to further engineer the NP surface. A detailed study of the competition between an alkanethiol (11-mercaptoundecanoic acid) and SH-PEG for the surface of AuNPs and the resultant behaviors of this model nanoconjugate is presented here. As a result, the physicochemical properties of these conjugates can be progressively tuned by controlling the composition and especially the conformation of the mixed monolayer. This has implications in the physiological stability. The controlled changes on the SH-PEG conformation rather than its concentration induce a change in the stabilization mechanism from electrostatic repulsion to steric hindrance, which changes the biological fate of NPs. Importantly, the adsorption of proteins on the conjugates can be tailored by tuning the composition and conformation of the mixed layer.

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        Most cited references 41

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        Opsonization, biodistribution, and pharmacokinetics of polymeric nanoparticles.

        The process of opsonization is one of the most important biological barriers to controlled drug delivery. Injectable polymeric nanoparticle carriers have the ability to revolutionize disease treatment via spatially and temporally controlled drug delivery. However, opsonin proteins present in the blood serum quickly bind to conventional non-stealth nanoparticles, allowing macrophages of the mononuclear phagocytic system (MPS) to easily recognize and remove these drug delivery devices before they can perform their designed therapeutic function. To address these limitations, several methods have been developed to mask or camouflage nanoparticles from the MPS. Of these methods, the most preferred is the adsorption or grafting of poly(ethylene glycol) (PEG) to the surface of nanoparticles. Addition of PEG and PEG-containing copolymers to the surface of nanoparticles results in an increase in the blood circulation half-life of the particles by several orders of magnitude. This method creates a hydrophilic protective layer around the nanoparticles that is able to repel the absorption of opsonin proteins via steric repulsion forces, thereby blocking and delaying the first step in the opsonization process.
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          Understanding the nanoparticle-protein corona using methods to quantify exchange rates and affinities of proteins for nanoparticles.

          Due to their small size, nanoparticles have distinct properties compared with the bulk form of the same materials. These properties are rapidly revolutionizing many areas of medicine and technology. Despite the remarkable speed of development of nanoscience, relatively little is known about the interaction of nanoscale objects with living systems. In a biological fluid, proteins associate with nanoparticles, and the amount and presentation of the proteins on the surface of the particles leads to an in vivo response. Proteins compete for the nanoparticle "surface," leading to a protein "corona" that largely defines the biological identity of the particle. Thus, knowledge of rates, affinities, and stoichiometries of protein association with, and dissociation from, nanoparticles is important for understanding the nature of the particle surface seen by the functional machinery of cells. Here we develop approaches to study these parameters and apply them to plasma and simple model systems, albumin and fibrinogen. A series of copolymer nanoparticles are used with variation of size and composition (hydrophobicity). We show that isothermal titration calorimetry is suitable for studying the affinity and stoichiometry of protein binding to nanoparticles. We determine the rates of protein association and dissociation using surface plasmon resonance technology with nanoparticles that are thiol-linked to gold, and through size exclusion chromatography of protein-nanoparticle mixtures. This method is less perturbing than centrifugation, and is developed into a systematic methodology to isolate nanoparticle-associated proteins. The kinetic and equilibrium binding properties depend on protein identity as well as particle surface characteristics and size.
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            Gold nanoparticles in delivery applications.

            Gold nanoparticles (AuNPs) provide non-toxic carriers for drug and gene delivery applications. With these systems, the gold core imparts stability to the assembly, while the monolayer allows tuning of surface properties such as charge and hydrophobicity. An additional attractive feature of AuNPs is their interaction with thiols, providing an effective and selective means of controlled intracellular release.
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              Author and article information

              Affiliations
              [1 ]Insitut Català de Nanociència i Nanotecnologia, Campus UAB, 08193 Barcelona, Spain
              [2 ]Institut Català de Recerca i Estudis Avançats, 08010 Barcelona, Spain
              [3 ]Vall d Hebron Research Insitute, 08035 Barcelona, Spain
              Author notes
              [* ]Corresponding author's e-mail address: victor.puntes@ 123456icn.cat

              Present address: Joan Comenge, Institute of Integrative Biology, University of Liverpool, L69 7ZB Liverpool, UK

              Contributors
              Journal
              SOR-MATSCI
              ScienceOpen Research
              ScienceOpen
              2199-1006
              23 March 2015
              : 0 (ID: fc4bce98-862b-415a-9f28-d891d214535c )
              : 0
              : 1-10
              2676:XE
              10.14293/S2199-1006.1.SOR-MATSCI.A0Z6OM.v1
              © 2015 J. Come and V.F. Puntes.

              This work has been published open access under Creative Commons Attribution License CC BY 4.0 , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com .

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