Revealing the Nanoparticle-Protein Corona with a Solid-State Nanopore.

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-ß or mix-αß). 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-ß proteins. We assign these observations to the lower internal energy of α-helices, making them more prone to form a homogeneous corona layer.

The influence of inter-particle forces on diffusion at the nanoscale.

Van der Waals and electrostatic interactions are the dominant forces acting at the nanoscale and they have been reported to directly influence a range of phenomena including surface adhesion, friction, and colloid stability but their contribution on nanoparticle diffusion dynamics is still not clear. In this study we evaluated experimentally the changes in the diffusion coefficient of nanoparticles as a result of varying the magnitude of Van der Waals and electrostatic forces. We controlled the magnitude of these forces by varying the ionic strength of a salt solution, which has been shown to be a parameter that directly controls the forces, and found by tracking single nanoparticles dispersed in solutions with different salt molarity that the diffusion of nanoparticles increases with the magnitude of the electrostatic forces and Van der Waals forces. Our results demonstrate that these two concurrently dynamic forces play a pivotal role in driving the diffusion process and must be taken into account when considering nanoparticle behaviour.

Protein at liquid solid interfaces: Toward a new paradigm to change the approach to design hybrid protein/solid-state materials.

This review gives an overview of protein adsorption at solid/liquid interface. Compared to the other ones, we have focus on three main questions with the point of view of the protein. The first question is related to the kinetic and especially the using of Langmuir model to describe the protein adsorption. The second question is about the concept of hard and soft protein. In this part, we report the protein structural modification induced by adsorption regarding their intrinsic structure. This allows formulating of a new concept to classify the protein to predict their behavior at solid/liquid interface. The last question is related to the protein corona. We give an overview about the soft/hard corona and attempt to make correlation with the concept of hard/soft protein.

Amyloid Growth, Inhibition, and Real-Time Enzymatic Degradation Revealed with Single Conical Nanopore.

Amyloid fibrils are involved in several neurodegenerative diseases. However, because of their polymorphism and low concentration, they are challenging to assess in real-time with conventional techniques. Here, we present a new approach for the characterization of the intermediates: protofibrils and "end-off" aggregates which are produced during the amyloid formation. To do so, we have fashioned conical track-etched nanopores that are functionalized to prevent the fouling. Using these nanopores, we have followed the kinetic of amyloid growth to discriminate the different intermediates protofibrils and "end-off. Then, the nanopore was used to characterize the effect of promoter and inhibitor of the fibrillation process. Finally, we have followed in real-time the degradation of amyloid with peptase. Compare with the SiN nanopore, the track-etched one features exceptionally high success rate via functionalization and detection in "one-pot". Our results demonstrate the potential for a conical nanopore to be used as a routine technique for the characterization of the amyloid growth and/or degradation.

Unexpected Hard Protein Behavior of BSA on Gold Nanoparticle Caused by Resveratrol.

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.

Metal alloy solid-state nanopores for single nanoparticle detection.

Solid-state nanopore technology for nanoparticle sensing is considered for the development of analytical tools to characterise their size, shape or zeta potential. In this field, it is crucial to understand how the nanopore inner surface influences the dynamic of nanoparticle translocation. Here, three single nanopores directly drilled in metal alloys (titanium nitride, titanium-tantalum and tantalum) are considered. The translocation of polystyrene nanoparticles coated with ssDNA is investigated by the resistive pulse method at different concentrations and voltages. The results show that the nanoparticle energy barrier for entrance into the pore decreases for nanopores that exhibits a higher surface energy and hydrophilicity, while the dwell time is found to depend on the nanopore surface state. Overall, this study demonstrates that the control of nanopore surface state must be taken into account for the resistive pulse experiments for nanoparticle detection.

Transition from fractional to classical Stokes-Einstein behaviour in simple fluids.

An optical technique for tracking single particles has been used to evaluate the particle diameter at which diffusion transitions from molecular behaviour described by the fractional Stokes-Einstein relationship to particle behaviour described by the classical Stokes-Einstein relationship. The results confirm a prior prediction from molecular dynamic simulations that there is a particle size at which transition occurs and show it is inversely dependent on concentration and viscosity but independent of particle density. For concentrations in the range 5 × 10-3 to 5 × 10-6 mg ml-1 and viscosities from 0.8 to 150 mPa s, the transition was found to occur in the diameter range 150-300 nm.