Real-time investigation of interactions between nanoparticles and cell membrane model

Light on the interactions between nanoparticles and lipid membranes by interface-sensitive vibrational spectroscopy

Nanoparticles are produced in natural phenomena or synthesized artificially for technological applications. Their frequent contact with humans has been judged potentially harmful for health, and numerous studies are ongoing to understand the mechanisms of the toxicity of nanoparticles. At the macroscopic level, the toxicity can be established in vitro or in vivo by measuring the survival of cells. At the sub-microscopic level, scientists want to unveil the molecular mechanisms of the first interactions of nanoparticles with cells via the cell membrane, before the toxicity cascades within the whole cell. Unveiling a molecular understanding of the nanoparticle-membrane interface is a tricky challenge, because of the chemical complexity of this system and its nanosized dimensions buried within bulk macroscopic environments. In this review, we highlight how, in the last 10 years, second-order nonlinear optical (NLO) spectroscopy, and specifically vibrational sum frequency generation (SFG), has provided a new understanding of the structural, physicochemical, and dynamic properties of these biological interfaces, with molecular sensitivity. We will show how the intrinsic interfacial sensitivity of second-order NLO and the chemical information of vibrational SFG spectroscopy have revealed new knowledge of the molecular mechanisms that drive nanoparticles to interact with cell membranes, from both sides, the nanoparticles and the membrane properties.

In situ study of structural changes: Exploring the mechanism of protein corona transition from soft to hard

HYPOTHESIS

The process of protein corona changes has been widely believed to follow the Vroman effect, while protein structural change during the process is rarely reported, due to the lack of analytical methods. In-situ interpretation for protein structural change is critical to processes such as the recognition and transport of nanomaterials.

EXPERIMENTS

Molecular dynamics (MD) simulation was used to predict the deflection and twist of the protein tertiary structure. The structural changes of the surface protein corona during the interaction of nanoparticles (NPs) with lipid bilayer were probed in situ and real-time by sum frequency generation (SFG) spectroscopy.

FINDINGS

The ring tertiary structure of the protein corona is altered from vertical to horizontal on particle surface, a process of the soft-to-hard structural transition, which is contributed by the hydrogen bonding force between the protein and water molecules. The negatively charged protein corona can induce the redistribution of interfacial charge, leading to a more stable hydrogen bond network of the interfacial water. Our findings suggest that the structural change from flexible to rigid is a crucial process in the soft-to-hard transition of the protein corona, which will be a beneficial supplement to the Vroman effect of protein adsorption.

Linking nanomaterial properties to biological outcomes: analytical chemistry challenges in nanotoxicology for the next decade

This article provides our perspective on the analytical challenges in nanotoxicology as the field is entering its third decade.