Roberto Magalhães Paniago

Amongst metallic nanoparticles, gold is commonly used for bioconjugation due to its remarkable characteristics which allow its use for nanomedicine. Regarding in vitro studies, physiological pH, standard cell culture medium and temperature have often been considered for experimental design. However, it is also necessary to understand the impact of different pH, temperature, buffers and protein-enriched media on the stability of bare and functionalized gold nanoparticles to simulate non-physiological conditions. In this work, we dispersed uncovered gold nanoparticles (AuNP), PEGylated (AuNPPEG) and cetuximab-gold nanoparticles (AuNPCet) in different solutions, acidic and alkaline media and three different temperatures. Next, a series of characterization techniques was applied to measure the level of aggregation and the formation of protein corona as well. To investigate whether non-physiological conditions impair AuNPCet effectiveness, binding affinity and apoptosis assays were performed using A431 cells. Our results demonstrated that covered and uncovered gold nanoparticles lose stability when dispersed in salt-rich buffers and saliva is not a good medium for AuNPCet dispersion. Nevertheless, this nanoplatform preserves its function integrity across acidic or alkaline environments resulting in the induction of apoptosis in tumor cells. Moreover, the formation of the protein corona did not interfere with the EGFR binding. Taken together, our findings elucidate the behavior of gold nanoparticles under non-physiological conditions and tumor microenvironment-like settings, providing a route for the rational planning of future clinical trials in head and neck cancer.

In this work, flower-like molybdenum disulfide (MoS₂) microspheres were produced with polyethylene glycol (PEG) to form MoS₂-PEG. Likewise, gold nanoparticles (AuNPs) were added to form MoS₂-PEG/Au to investigate its potential application as a theranostic nanomaterial. These nanomaterials were fully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), photoelectron X-ray spectroscopy (XPS), Fourier-transformed infrared spectroscopy (FTIR), cyclic voltammetry and impedance spectroscopy. The produced hierarchical MoS₂-PEG/Au microstructures showed an average diameter of 400 nm containing distributed gold nanoparticles, with great cellular viability on tumoral and non-tumoral cells. This aspect makes them with multifunctional characteristics with potential application for cancer diagnosis and therapy. Through the complete morphological and physicochemical characterization, it was possible to observe that both MoS₂-PEG and MoS₂-PEG/Au showed good chemical stability and demonstrated noninterference in the pattern of the cell nucleus, as well. Thus, our results suggest the possible application of these hybrid nanomaterials can be immensely explored for theranostic proposals in biomedicine.

Naturally occurring van der Waals crystals have brought unprecedented interest to nanomaterial researchers in recent years. So far, more than 1800 layered materials (LMs) have been identified but only a few insulating and naturally occurring LMs were deeply investigated. Phyllosilicate minerals, which are a class of natural and abundant LMs, have been recently considered as a low-cost source of insulating nanomaterials. Within this family an almost barely explored material emerges: phlogopite (KMg ₃ (AlSi ₃ )O ₁₀ (OH) ₂ ). Here we carry out a high throughput characterization of this LM by employing several experimental techniques, corroborating the major findings with first-principles calculations. We show that monolayers (1L) and few-layers of this material are air and temperature stable, as well as easily obtained by the standard mechanical exfoliation technique, have an atomically flat surface, and lower bandgap than its bulk counterpart, an unusual trend in LMs. We also systematically study the basic properties of ultrathin phlogopite and demonstrate that natural phlogopite presents iron impurities in its crystal lattice, which decreases its bandgap from about 7 eV to 3.6 eV. Finally, we combine phlogopite crystals with 1L-WS ₂ in ultrathin van der Waals heterostructures and present a photoluminescence study, revealing a significant enhancement on the 1L-WS ₂ optical quality (i.e. higher recombination efficiency through neutral excitons) similarly to that obtained on 1L-WS ₂ /hexagonal boron nitride heterostructures. Our proof-of-concept study shows that phlogopite should be regarded as a good and promising candidate for LM-based applications as a low-cost layered nanomaterial.

Gold nanoparticles enhance antibody-fluorescence detection by flow cytometry reducing the signal to noise ratio and improving cell biology assessments.

Hematite (α-Fe₂O₃) thin films were prepared by sol-gel route and investigated for application in H₂ generation by photo-assisted water splitting. The photoelectrochemical (PEC) performance was shown to increase significantly for films deposited on SnO₂:F/glass subjected to high temperature (T) annealing (>750 °C). Strong correlation was found between photogenerated current, donor concentration, and Sn concentration as determined by Mott-Schottky analysis and X-ray photoelectron spectroscopy. The effects of thermal annealing and Sn addition in the resulting microstructure and optical properties of hematite films deposited on fused silica substrates were determined by a combination of structural characterization techniques and spectroscopic ellipsometry. Thermal annealing (>600 °C) induces a higher optical absorption that is associated directly to film densification and grain growth; however, it promotes no changes in the energy positions of the main Fe₂O₃ electronic transitions. The band gap energy was found to be 2.21 eV and independent of microstructure and of Sn concentration for all studied films. On the other hand, Sn can be incorporated in the Fe₂O₃ lattice for concentration up to Sn/Fe ∼2%, leading to an increase in energy split of the main absorption peak, attributed to a distortion of the Fe₂O₃ lattice. For higher concentrations, Sn incorporation leads to a reduction in absorption, associated with higher porosity and the formation of a secondary Sn-rich phase. In summary, the variation in the optical properties induced by thermal annealing and Sn addition cannot account for the order of magnitude increase of the current density generated by photoanodes annealed at high T (>750 °C); thus, it is concluded that the major contribution for the enhanced PEC performance comes from improved electronic properties induced by the n-type doping caused by Sn diffusion from the SnO₂:F substrate.