CO to formaldehyde transformation study on pristine and Au-modified BaTiO3(001) through DFT calculations

CONTEXT

BaTiO3 is one of the most important ferroelectric oxides in electronic applications. Also, it has attractive properties for catalysis that could be used for reducing contamination levels, especially carbon monoxide, CO. CO is one of the main gaseous pollutants generally released from the combustion of fossil fuel. In this work, the CO transformation on pristine and Au-modified BaTiO3 perovskite for H2CO obtention is studied. The CO adsorption and hydrogenation on pristine BaTiO3 leads to formaldehyde synthesis as the most stable product through two possible routes. Furthermore, hydrogenation stages are less probable on pristine BaTiO3. On Au-modified BaTiO3 formaldehyde is the principal product too but Au adatom generates H2CO competition with HCOH. After BaTiO3 modification with Au unpaired electrons were generated. These unpaired electrons are related to the adatom reactivity. According to the obtained results, pristine and Au-modified BaTiO3 can adsorb and hydrogenate CO generating formaldehyde as the principal product. BaTiO3 modifications with Au increase the reactivity of the perovskite in the CO hydrogenation reactions. CO hydrogenation process on Au suggests that further hydrogenation stages beyond formaldehyde are possible.

METHODS

The study was performed through ab initio calculations using the periodic spin-polarized Density Functional Theory (DFT) as implemented in Quantum ESPRESSO. DFT calculations were carried out using the Plane Wave self-consistent field (PWscf). Spin density difference allows us to identify reactive regions related to dangling bonds and unpaired electrons. A plane wave basis set was used to represent the electron states. Vanderbilt pseudopotentials with nonlinear core correction were used to model the ionic cores and valence electrons interaction. Exchange-correlation energies were treated within the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) parameterization.

Cooperative Functionalities in Porous Nanoparticles for Seeking Extracellular DNA and Targeting Pathogenic Biofilms via Photodynamic Therapy

Many pathogenic bacteria are getting more and more resistant against antibiotic treatment and even become up to 1.000× times more resilient in the form of a mature biofilm. Thus, one is currently prospecting for alternative methods for treating microbial infections, and photodynamic therapy is a highly promising approach by creating so-called reactive oxygen species (ROS) produced by a photosensitizer (PS) upon irradiation with light. Unfortunately, the unspecific activity of ROS is also problematic as they are harmful to healthy tissue as well. Notably, one knows that uncontrolled existence of ROS in the body plays a major role in the development of cancer. These arguments create need for advanced theranostic materials which are capable of autonomous targeting and detecting the existence of a biofilm, followed by specific activation to combat the infection. The focus of this contribution is on mesoporous organosilica colloids functionalized by orthogonal and localized click-chemistry methods. The external zone of the particles is modified by a dye of the Hoechst family. The particles readily enter a mature biofilm where adduct formation with extracellular DNA and a resulting change in the fluorescence signal occurs, but they cannot cross cellular membranes such as in healthy tissue. A different dye suitable for photochemical ROS generation, Acridine Orange, is covalently linked to the surfaces of the internal mesopores. The spectral overlap between the emission of Hoechst with the absorption band of Acridine Orange facilitates energy transfer by Förster resonance with up to 88% efficiency. The theranostic properties of the materials including viability studies were investigated in vitro on mature biofilms formed by Pseudomonas fluorescens and prove the high efficacy.

Second harmonic generation nanoparticles enables Near-Infrared Photodynamic Therapy from visible light reactive photosensitizer conjugates

Combination of photosensitizers (PS) with nanotechnology can improve the therapeutic efficiency of clinical Photodynamic Therapy (PDT) by converting visible light reactive PSs into Near-Infrared (NIR) light responsive molecules using Harmonic Nanoparticles (HNP). To test the PDT efficiency of HNP-PS conjugates, pathogenic S. aureus cell cultures were treated with perovskite (Barium Titanate) Second Harmonic Generation (SHG) nanoparticles conjugated to photosensitizers (PS) (we compared both FDA approved Protoporphyrin IX and Curcumin) and subjected to a femtosecond pulsed Near-Infrared (NIR) laser (800 nm, 232-228 mW, 12-15 fs pulse width at repetition rate of 76.9 MHz) for 10 minutes each. NIR PDT using Barium Titanate (BT) conjugated with Protoporphyrin IX as HNP-PS conjugate reduced the viability of S. aureus cells by 77.3 ± 9.7% while BT conjugated with Curcumin did not elicit any significant effect. Conventional PSs reactive only to visible spectrum light coupled with SHG nanoparticles enables the use of higher tissue penetrating NIR light to generate an efficient photodynamic effect, thereby overcoming low light penetration and tissue specificity of conventional visible light PDT treatments.

Barium Titanate (BaTiO3) Nanoparticles Exert Cytotoxicity through Oxidative Stress in Human Lung Carcinoma (A549) Cells

Barium titanate (BaTiO3) nanoparticles (BT NPs) have shown exceptional characteristics such as high dielectric constant and suitable ferro-, piezo-, and pyro-electric properties. Thus, BT NPs have shown potential to be applied in various fields including electro-optical devices and biomedicine. However, very limited knowledge is available on the interaction of BT NPs with human cells. This work was planned to study the interaction of BT NPs with human lung carcinoma (A549) cells. Results showed that BT NPs decreased cell viability in a dose- and time-dependent manner. Depletion of mitochondrial membrane potential and induction of caspase-3 and -9 enzyme activity were also observed following BT NP exposure. BT NPs further induced oxidative stress indicated by induction of pro-oxidants (reactive oxygen species and hydrogen peroxide) and reduction of antioxidants (glutathione and several antioxidant enzymes). Moreover, BT NP-induced cytotoxicity and oxidative stress were effectively abrogated by N-acetyl-cysteine (an ROS scavenger), suggesting that BT NP-induced cytotoxicity was mediated through oxidative stress. Intriguingly, the underlying mechanism of cytotoxicity of BT NPs was similar to the mode of action of ZnO NPs. At the end, we found that BT NPs did not affect the non-cancerous human lung fibroblasts (IMR-90). Altogether, BT NPs selectively induced cytotoxicity in A549 cells via oxidative stress. This work warrants further research on selective cytotoxicity mechanisms of BT NPs in different types of cancer cells and their normal counterparts.

SHG-enhanced NIR-excited in vitro photodynamic therapy using composite nanoparticles of barium titanate and rose Bengal

Near infrared (NIR) light excited photodynamic therapy (PDT) has been considered as a possible way to increase the therapy depth. Besides the traditional two-photon excited PDT and upconversion PDT by rare-earth ion materials, SHG has drawn much attention recently to act as an additional choice to achieve NIR light excited PDT. Herein, by using the electrostatic absorption method, barium titanate and rose Bengal composite nanoparticles (BT@PAH/RB/PAH, BT–RB) were synthesized. Compared with rose Bengal (RB) molecules and a mixture of barium titanate nanoparticles and RB (BT + RB), BT–RB nanoparticles were shown to be able to produce more reactive oxygen species (ROS) ex vivo and in vitro. Afterwards, the SHG-enhanced localized PDT was applied on Hela cells, in which BT–RB nanoparticles showed a better performance than BT + RB. Our work has shown that the SHG-enhanced PDT has good prospects and the close combination of harmonic nanoparticles and photosensitizers may facilitate the development of novel reagents for NIR light excited PDT.

Composite nanoparticles of barium titanate and rose Bengal are used to achieve second harmonic generation (SHG) enhanced photodynamic therapy excited by near infrared (NIR) light.

Self-assembled organic nanorods for dual chemo-photodynamic therapies

Photodynamic therapy (PDT) and chemotherapy have been extensively developed as effective approaches against cancer. Herein, we constructed organic nanorods by rational co-assembly of photosensitizer, di-iodinated borondipyrromethene (BDP-I2), and chemical anticancer drug, paclitaxel (PTX). The physico- and photochemical properties of the obtained nanorods were carefully investigated. BDP-I2 was selected for its high singlet oxygen (1O2) quantum yields. And the corresponding 1O2 generation ability and photodynamic effect were evaluated both in vitro and in vivo. The accelerated endosomal escape of the nanorods induced by the photodynamic effect enhanced the chemotherapeutic efficacy of PTX. We believe that this synergetic nanomedicine represents a new development for antitumor chemophotodynamic therapy.

Mechanochemistry of Chitosan-Coated Zinc Sulfide (ZnS) Nanocrystals for Bio-imaging Applications

The ZnS nanocrystals were prepared in chitosan solution (0.1 wt.%) using a wet ultra-fine milling. The obtained suspension was stable and reached high value of zeta potential (+57 mV). The changes in FTIR spectrum confirmed the successful surface coating of ZnS nanoparticles by chitosan. The prepared ZnS nanocrystals possessed interesting optical properties verified in vitro. Four cancer cells were selected (CaCo-2, HCT116, HeLa, and MCF-7), and after their treatment with the nanosuspension, the distribution of ZnS in the cells was studied using a fluorescence microscope. The particles were clearly seen; they passed through the cell membrane and accumulated in cytosol. The biological activity of the cells was not influenced by nanoparticles, they did not cause cell death, and only the granularity of cells was increased as a consequence of cellular uptake. These results confirm the potential of ZnS nanocrystals using in bio-imaging applications.

Understanding the neurovascular unit at multiple scales: Advantages and limitations of multi-photon and functional ultrasound imaging

Developing efficient brain imaging technologies by combining a high spatiotemporal resolution and a large penetration depth is a key step for better understanding the neurovascular interface that emerges as a main pathway to neurodegeneration in many pathologies such as dementia. This review focuses on the advances in two complementary techniques: multi-photon laser scanning microscopy (MPLSM) and functional ultrasound imaging (fUSi). MPLSM has become the gold standard for in vivo imaging of cellular dynamics and morphology, together with cerebral blood flow. fUSi is an innovative imaging modality based on Doppler ultrasound, capable of recording vascular brain activity over large scales (i.e., tens of cubic millimeters) at unprecedented spatial and temporal resolution for such volumes (up to 10μm pixel size at 10kHz). By merging these two technologies, researchers may have access to a more detailed view of the various processes taking place at the neurovascular interface. MPLSM and fUSi are also good candidates for addressing the major challenge of real-time delivery, monitoring, and in vivo evaluation of drugs in neuronal tissue.

In situ second-harmonic generation mediated photodynamic therapy by micelles co-encapsulating coordination nanoparticle and photosensitizer

NIR-PDT strategy was introduced by employing a nonlinear optical conveyor bearing strong second-harmonic generation (SHG) property. A biocompatible micellic system co-delivered the conveyor and photosensitizer for in situ NIR-PDT.