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Titanium dioxide (TiO2) shows significant potential as a self-cleaning material to inactivate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and prevent virus transmission. This study provides insights into the impact of UV-A light on the photocatalytic inactivation of adsorbed SARS-CoV-2 virus-like particles (VLPs) on a TiO2 surface at the molecular and atomic levels. X-ray photoelectron spectroscopy, combined with density functional theory calculations, reveals that spike proteins can adsorb on TiO2 predominantly via their amine and amide functional groups in their amino acids blocks. We employ atomic force microscopy and grazing-incidence small-angle X-ray scattering (GISAXS) to investigate the molecular-scale morphological changes during the inactivation of VLPs on TiO2 under light irradiation. Notably, in situ measurements reveal photoinduced morphological changes of VLPs, resulting in increased particle diameters. These results suggest that the denaturation of structural proteins induced by UV irradiation and oxidation of the virus structure through photocatalytic reactions can take place on the TiO2 surface. The in situ GISAXS measurements under an N-2 atmosphere reveal that the virus morphology remains intact under UV light. This provides evidence that the presence of both oxygen and UV light is necessary to initiate photocatalytic reactions on the surface and subsequently inactivate the adsorbed viruses. The chemical insights into the virus inactivation process obtained in this study contribute significantly to the development of solid materials for the inactivation of enveloped viruses.

Titanium dioxide nanotubes (TNT) have been extensively studied because of their unique properties, which make such systems ideal candidates for biomedical application, especially for the targeted release of drugs. However, knowledge about the properties of TiO2 nanotubes with typical dimensions of the order of the nanometer is limited, especially concerning the adsorption of molecules that can be potentially loaded in actual devices. In this work, we investigate, by means of simulations based on hybrid density functional theory, the adsorption of Vitamin C molecules on different nanotubes through a comparative analysis of the properties of different structures. We consider two different anatase TiO2 surfaces, the most stable (101) and the more reactive (001)A; we evaluate the role of the curvature, the thickness and of the diameter as well as of the rolling direction of the nanotube. Different orientations of the molecule with respect to the surface are studied in order to identify any trends in the adsorption mechanism. Our results show that there is no preferential functional group of the molecule interacting with the substrate, nor any definite spatial dependency, like a rolling orientation or the concavity of the nanotube. Instead, the adsorption is driven by geometrical factors only, i.e., the favorable matching of the position and the alignment of any functional groups with undercoordinated Ti atoms of the surface, through the interplay between chemical and hydrogen bonds. Differently from flat slabs, thicker nanotubes do not improve the stability of the adsorption, but rather develop weaker interactions, due to the enhanced curvature of the substrate layers.

In the field of nanomedicine, significant attention is directed toward near-infrared (NIR) light-responsive inorganic nanosystems, primarily for their applications in photodynamic therapy and fluorescence bioimaging. The crucial role of the NIR range lies in enabling optimal tissue penetration, which is essential for both irradiating and detecting nanoparticles deep within the human body. In this study, we employed density functional theory (DFT) and time-dependent DFT (TDDFT) calculations to explore the structural and electronic properties of cyanine-functionalized TiO2 spherical nanoparticles (NPs) with a realistic diameter of 2.2 nm. We revealed that different adsorption configurations of cyanine (VG20-C1) on the TiO2 NP surface exhibit distinct features in the optical spectra. These cyanine dyes, serving as bifunctional linkers with two carboxylic end groups, can adsorb in either a side-on mode (binding with both end groups) or an end-on mode (binding only one end group). In end-on adsorption structures, low-energy excitations are exclusive to dye-to-dye electronic transitions, while side-on structures exhibit electron charge transfer excitations from the dye to the TiO2 NP at low energy. This thorough analysis provides a rational foundation for designing cyanine-functionalized TiO2 nanosystems with optimal optical characteristics tailored for specific nanomedical applications such as photodynamic therapy or fluorescence bioimaging.

Experimental and theoretical studies have demonstrated that the use of single atom catalysts (SACs) for energy conversion processes is very promising. However, their stability under catalytic conditions is the main issue that hinders their commercial use. In this work, we report an oxygen evolution catalyst based on single nickel atoms stabilized in triazine-based carbon nitride (CN) and a detailed study of the evolution of the Ni centers under catalytic conditions. The nanostructured materials have been characterized by combining experimental techniques, such as X-ray diffraction, transmission electron microscopy, X-ray absorption and X-ray photoemission spectroscopy, with DFT theoretical calculations to determine the CN structure, the metal adsorption sites, the coordination of the Ni atoms, and the changes undergone under catalytic conditions. Electrochemical characterization showed a linear increase of the catalytic activity with Ni loading. The stability of the materials was studied by HR-TEM and XAS post-catalysis measurements and DFT simulations. Results indicated a partial chemical restructuring of the single Ni atoms under catalytic conditions with the formation of Ni-O-Ni moieties, stabilized in the CN cavities, which are the real catalytic species.

Nanoparticles' (NPs) permeation through cell membranes, whether it happens via passive or active transport, is an essential initial step for their cellular internalization. The NPs' surface coating impacts the way they translocate through the lipid bilayer and the spontaneity of the process. Understanding the molecular details of NPs' interaction with cell membranes allows the design of nanosystems with optimal characteristics for crossing the lipid bilayer: computer simulations are a powerful tool for this purpose. In this work, we have performed coarse-grained molecular dynamics simulations and free energy calculations on spherical titanium dioxide NPs conjugated with polymer chains of different chemical compositions. We have demonstrated that the hydrophobic/hydrophilic character of the chains, more than the nature of their terminal group, plays a crucial role in determining the NPs' interaction with the lipid bilayer and the thermodynamic spontaneity of NPs' translocation from water to the membrane. We envision that this computational work will be helpful to the experimental community in terms of the rational design of NPs for efficient cell membrane permeation.By coarse-grained molecular dynamics simulations, we have unveiled that nanoparticles coated with mixed hydrophobic/hydrophilic polymer chains spontaneously penetrate lipid membranes, unlike those covered with chains of hydrophilic character only.

Molecular dynamics simulation techniques have been in the spotlight of recent nanomedicine research, becoming an indispensable tool for unveiling complex molecular mechanisms that are sometimes unreachable by experimental methods. Here, we demonstrate how MD simulations can complement existing experimental knowledge or provide new mechanistic insights into relevant aspects of nanoscale devices designed for nanomedicine. Through some case studies - from how thermodynamic variables (e.g., pH and ionic strength) affect the protein corona formation onto organic-functionalized nanoparticles to the impact of lipid composition in the permeation process of anti-tumoral drugs in membranes - this work compilation illustrates how classical MD simulations can be helpful bridging the simulated microscopic behaviors to their corresponding macroscopic manifestation.

Molecular dynamics simulation techniques have been in the spotlight of recent nanomedicine research, becoming an indispensable tool for unveiling complex molecular mechanisms that are sometimes unreachable by experimental methods. Here, we demonstrate how MD simulations can complement existing experimental knowledge or provide new mechanistic insights into relevant aspects of nanoscale devices designed for nanomedicine. Through some case studies - from how thermodynamic variables (e.g., pH and ionic strength) affect the protein corona formation onto organic-functionalized nanoparticles to the impact of lipid composition in the permeation process of anti-tumoral drugs in membranes - this work compilation illustrates how classical MD simulations can be helpful bridging the simulated microscopic behaviors to their corresponding macroscopic manifestation.