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For the past 2 decades, emerging single-nanopore technologies have opened the route to multiple sensing applications. Besides DNA sensing, the identification of proteins and amyloids is a promising field for early diagnosis. However, the influence of the interactions between the nanopore surface and proteins should be taken into account. In this work, we have selected three proteins (avidin, lysozyme, and IgG) that exhibit different affinities with the SiNx surface, and we have also examined lysozyme amyloid. Our results show that the piranha treatment of SiNx significantly decreases protein adsorption. Moreover, we have successfully detected all proteins (pore diameter 17 nm) and shown the possibility of discriminating between denatured lysozyme and its amyloid. For all proteins, the capture rates are lower than expected, and we evidence that they are correlated with the affinity of proteins to the surface. Our result confirms that proteins interacting only with the nanopore surface wall stay long enough to be detected. For lysozyme amyloid, we show that the use of the nanopore is suitable for determining the number of monomer units even if only the proteins interacting with the nanopore are detected.

The understanding of the interactions between nanomaterials, biomolecules, and polyphenols is fundamental in food chemistry, toxicology, and new emerging fields, such as nanomedicine. Here, we investigated the effect of the resveratrol, a principal actor in drug-delivery application on the interaction between bovine serum albumin (BSA), employed as a vector for the delivery of polyphenol drugs, and gold nanoparticle (gNP), the most promising tool in theranostic applications. Through a combination of experimental techniques, which includes an initial evaluation by dynamic light scattering and surface plasmon resonance spectroscopy, we were able to evaluate the evolution of the gold nanoparticle aggregation with increasing ionic strength and the consequences of the BSA and resveratrol addition. To investigate the mechanisms of the interactions, we pursued at the single-molecule level using solid-state nanopore and fluorescence correlation spectroscopy. Our results show that without resveratrol, the BSA is adsorbed on the gNP in water or saline solution. In the presence of resveratrol, the BSA is normally absorbed on gNP in water, but the salt addition leads to its desorption. The resveratrol clearly plays a fundamental role, changing the protein behavior and making the BSA adsorption a reversible process in the presence of salt.

We investigate the influence of a nanopore surface state and the addition of Mg(2+) on poly-adenosine translocation. To do so, two kinds of nanopores with a low aspect ratio (diameter ∼3-5 nm, length 30 nm) were tailored: the first one with a negative charge surface and the second one uncharged. It was shown that the velocity and the energy barrier strongly depend on the nanopore surface. Typically if the nanopore and polyA exhibit a similar charge, the macromolecule velocity increases and its global energy barrier of entrance in the nanopore decreases, as opposed to the non-charged nanopore. Moreover, the addition of a divalent chelating cation induces an increase of energy barrier of entrance, as expected. However, for a negative nanopore, this effect is counterbalanced by the inversion of the surface charge induced by the adsorption of divalent cations.

Protein adsorption at the liquid–solid interface is an old but not totally solved topic. One challenge is to find an easy way to characterize the protein behavior on nanoparticles and make a correlation with its intrinsic properties. This work aims to investigate protein adsorption on gold nanoparticles and the colloidal properties. The protein panel was chosen from different structural categories (mainly-α, mainly-β or mix-αβ). The result shows that the colloidal stability with salt addition does not depend on the structural category. Conversely, using the single nanopore technique, we show that the mainly-α proteins form a smaller corona than the mainly-β proteins. We assign these observations to the lower internal energy of α-helices, making them more prone to form a homogeneous corona layer.

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