Mixed poly (ethylene glycol) and oligo (ethylene glycol) layers on gold as nonfouling surfaces created by backfilling

Lokanathan, Arcot R.; Zhang, Shuai; Regina, Viduthalai R.; Cole, Martin A.; Ogaki, Ryosuke; Dong, Mingdong; Besenbacher, Flemming; Kingshott, Peter

doi:10.1116/1.3647506

Cited by 25 publications

(19 citation statements)

References 33 publications

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“…35,36 Unlike the "brush" conformation of ODT on gold, PEG chains sometimes arrange in "island" or "mushroom" conformations. 37,38 In addition, the PEG used in this study had a much larger molecular weight (M n = 2000) than ODT (M w = 286.56), indicating that PEG had longer, disorganized chains, which might further prevent the formation of a uniform and dense monolayer. 35,36 Magnetite nanoparticles were synthesized by the coprecipitation method on ODT, PEG, and bare gold surfaces.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Effect of Surface Hydrophobicity on the Function of the Immobilized Biomineralization Protein Mms6

Liu

Zhang

Nayak

et al. 2015

Ind. Eng. Chem. Res.

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Magnetotactic bacteria produce magnetic nanocrystals with uniform shapes and sizes in nature, which has inspired in vitro synthesis of uniformly sized magnetite nanocrystals under mild conditions. Mms6, a biomineralization protein from magnetotactic bacteria with a hydrophobic N-terminal domain and a hydrophilic C-terminal domain, can promote formation of magnetite nanocrystals in vitro with well-defined shape and size in gels under mild conditions. Here we investigate the role of surface hydrophobicity on the ability of Mms6 to template magnetite nanoparticle formation on surfaces. Our results confirmed that Mms6 can form a protein network structure on a monolayer of hydrophobic octadecanethiol (ODT)-coated gold surfaces and facilitate magnetite nanocrystal formation with uniform sizes close to those seen in nature, in contrast to its behavior on more hydrophilic surfaces. We propose that this hydrophobicity effect might be due to the amphiphilic nature of the Mms6 protein and its tendency to incorporate the hydrophobic Nterminal domain into the hydrophobic lipid bilayer environment of the magnetosome membrane, exposing the hydrophilic C-terminal domain that promotes biomineralization. Supporting this hypothesis, the larger and well-formed magnetite nanoparticles were found to be preferentially located on ODT surfaces covered with Mms6 as compared to control samples, as characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy studies. A C-terminal domain mutant of this protein did not form the same network structure as wild-type Mms6, suggesting that the network structure is important for the magnetite nanocrystal formation. This study provides valuable insights into the role of surface hydrophilicity on the action of the biomineralization protein Mms6 to synthesize magnetic nanocrystals and provides a facile route to controlling bioinspired nanocrystal synthesis in vitro. ABSTRACT: Magnetotactic bacteria produce magnetic nanocrystals with uniform shapes and sizes in nature, which has inspired in vitro synthesis of uniformly sized magnetite nanocrystals under mild conditions. Mms6, a biomineralization protein from magnetotactic bacteria with a hydrophobic N-terminal domain and a hydrophilic C-terminal domain, can promote formation of magnetite nanocrystals in vitro with well-defined shape and size in gels under mild conditions. Here we investigate the role of surface hydrophobicity on the ability of Mms6 to template magnetite nanoparticle formation on surfaces. Our results confirmed that Mms6 can form a protein network structure on a monolayer of hydrophobic octadecanethiol (ODT)-coated gold surfaces and facilitate magnetite nanocrystal formation with uniform sizes close to those seen in nature, in contrast to its behavior on more hydrophilic surfaces. We propose that this hydrophobicity effect might be due to the amphiphilic nature of the Mms6 protein and its tendency to incorporate the hydrophobic N-terminal domain into the hydroph...

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Section: ■ Results and Discussionmentioning

confidence: 99%

Effect of Surface Hydrophobicity on the Function of the Immobilized Biomineralization Protein Mms6

Liu

Zhang

Nayak

et al. 2015

Ind. Eng. Chem. Res.

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“…The selective aptasensing interface was prepared by modifying the gold with a Poly Ethylene Glycol (PEG) Self Assembled Monolayer (SAM) 16 so to provide the highest accessibility for the analyte to the aptamer immobilized at the plasmonic surface, while decreasing the non specific adsorption. The PEG-SAMs are known to decrease the non specific protein adsorption, given their “brush” conformation, that is dependent both on the PEG chain density and on the molecular weight 17,18 . PEG-SAMs have been demonstrated to be effective of limiting the deposition of interferents at the plasmonic interface and in avoiding the consequent changes in the refractive-index that impair the sensing performance 19 .…”

Section: Introductionmentioning

confidence: 99%

D-shaped plastic optical fibre aptasensor for fast thrombin detection in nanomolar range

Cennamo

Pasquardini²,

Arcadio

et al. 2019

Sci Rep

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The development of optical biosensors for the rapid and costless determination of clinical biomarkers is of paramount importance in medicine. Here we report a fast and low-cost biosensor based on a plasmonic D-shaped plastic optical fibre (POF) sensor derivatized with an aptamer specific for the recognition of thrombin, the target marker of blood homeostasis and coagulation cascade. In particular, we designed a functional interface based on a Self Assembled Monolayer (SAM) composed of short Poly Ethylene Glycol (PEG) chains and biotin-modified PEG thiol in ratio 8:2 mol:mol, these latter serving as baits for the binding of the aptamer through streptavidin-chemistry. The SAM was studied by X-ray Photoelectron Spectroscopy (XPS) analysis, static contact angle (CA), Surface Plasmon Resonance (SPR) in POFs, and fluorescence microscopy on gold surface. The optimized SAM composition enabled the immobilization of about 112 ng/cm2 of aptamer. The thrombin detection exploiting POF-Aptasensor occurred in short times (5–10 minutes), the reached Limit of Detection (LOD) was about 1 nM, and the detection range was 1.6–60 nM, indicating the POF-Aptasensor well addresses the needs for a low-cost, simple to use and to realize, rapid, small size and portable diagnostic platform.

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“…The backfilling approach is another very useful technique, instead of PEG and oEG grafting, wherein the spaces present in the long PEG chain are filled with shorter PEG chains serving as a protective layer to backfill the surface and suppress NSB [140]. Lokanathan et al in 2011 used the backfilling approach for the self-assembled monolayer (SAM) of a mix of PEG thiol filled with oEG terminated alkane thiol molecules resulting in underbrush formation, causing a better protein resistance and less desorption of PEG compared to alkane thiol [141].…”

Section: Strategies To Suppress Non-specific Binding Of Antibodiesmentioning

confidence: 99%

Suppressing Non-Specific Binding of Proteins onto Electrode Surfaces in the Development of Electrochemical Immunosensors

Contreras-Naranjo

Aguilar

2019

Biosensors

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Electrochemical immunosensors, EIs, are systems that combine the analytical power of electrochemical techniques and the high selectivity and specificity of antibodies in a solid phase immunoassay for target analyte. In EIs, the most used transducer platforms are screen printed electrodes, SPEs. Some characteristics of EIs are their low cost, portability for point of care testing (POCT) applications, high specificity and selectivity to the target molecule, low sample and reagent consumption and easy to use. Despite all these attractive features, still exist one to cover and it is the enhancement of the sensitivity of the EIs. In this review, an approach to understand how this can be achieved is presented. First, it is necessary to comprise thoroughly all the complex phenomena that happen simultaneously in the protein-surface interface when adsorption of the protein occurs. Physicochemical properties of the protein and the surface as well as the adsorption phenomena influence the sensitivity of the EIs. From this point, some strategies to suppress non-specific binding, NSB, of proteins onto electrode surfaces in order to improve the sensitivity of EIs are mentioned.

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Mixed poly (ethylene glycol) and oligo (ethylene glycol) layers on gold as nonfouling surfaces created by backfilling

Cited by 25 publications

References 33 publications

Effect of Surface Hydrophobicity on the Function of the Immobilized Biomineralization Protein Mms6

Effect of Surface Hydrophobicity on the Function of the Immobilized Biomineralization Protein Mms6

D-shaped plastic optical fibre aptasensor for fast thrombin detection in nanomolar range

Suppressing Non-Specific Binding of Proteins onto Electrode Surfaces in the Development of Electrochemical Immunosensors

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