Papers by Andressa da Cruz Schneid
Journal of the Brazilian Chemical Society, 2015
Thin films containing silver nanoparticles homogeneously dispersed, with narrow size distribution... more Thin films containing silver nanoparticles homogeneously dispersed, with narrow size distribution below 10 nm, were synthesized on flat glass surface, by using an ionic silsesquioxane as stabilizer and crosslinking agent. The films can be prepared without previous functionalization of substrate surfaces and without addition of other components. The films were heat treated up to 200 ºC and characterized by ultraviolet-visible, transmission electron microscopy, atomic force microscopy, thermogravimetric analysis and ellipsometry. The films were thermally stable when heated up to 200 ºC, presenting the same thickness, and maintaining both optical and morphological properties of silver nanoparticles. The antibacterial activity of the films, containing the silver nanoparticles, was evaluated against Staphylococcus aureus by using the film applicator coating method, showing an excellent performance even after the third cycle of sterilization.
The outreach of nanoparticle-based medical treatments has been severely hampered due to the unbal... more The outreach of nanoparticle-based medical treatments has been severely hampered due to the unbalance between the efforts in designing extremely complex materials and the general lack of studies devoted to understanding their colloidal stability in biological environments. Over the years the scientific community has neglected the relevance related to the nanoparticles colloidal state which consequently turned out in very poor bench-to-clinics translation. In this work, we show how mesoporous silica nanoparticles (MSNs-one of the most promising and tested drug delivery platforms) can be efficiently synthesized and prepared resulting in a colloidally-stable system. We first compared three distinct methods of MSNs' template removal and evaluated their ultimate colloidal stability. Then, we also proposed a simple way to prevent aggregation during the drying step by adsorbing BSA onto MSNs. The surface modification resulted in colloidally-stable particles that are successfully re-dispersed in biologically-relevant medium while retaining high hemocompatibility and low cytotoxicity.
Nanomedicine
Aim: This work is focused on obtaining degradable mesoporous silica nanoparticles (DMSNs) which a... more Aim: This work is focused on obtaining degradable mesoporous silica nanoparticles (DMSNs) which are able to maintain their colloidal stability in complex biological media. Materials & methods: DMSNs were synthesized using different ratios of disulfide organosilane (degradable structural moiety) and further functionalized with sulfobetaine silane (SBS) to enhance colloidal stability and improve biological compatibility. Results: There was a clear trade-off between nanoparticle degradability and colloidal stability, since full optimization of the degradation process generated unstable particles, while enhancing colloidal stability resulted in poor DMSNs degradation. It was also shown that acidic pH improved particle degradation which is commonly triggered by reduction stimulus. Conclusion: A chemical composition window was found where DMSNs presented satisfactory colloidal stability in biologically relevant medium, meaningful degradation profiles and high biocompatibility.
Journal of Sol-Gel Science and Technology, 2022
This review shows the most common and promising strategies to generate colloidally stable silica ... more This review shows the most common and promising strategies to generate colloidally stable silica nanoparticles (NPs) in simulated biological fluids and sheds light on the latest advances in producing degradable silica-based structures. Silica NPs can be synthesized in a wide variety of morphologies, porosity levels, and sizes. This versatility makes silica NPs one of the most promising nano-platforms for imaging and disease treatment. Nonetheless, biological barriers can decrease the success of translating them for therapeutic applications since the media composition can induce their colloidal stability loss. It can, consequently, lead to the NPs aggregation and affect their degradation profile. The interplay between NPs aggregation and degradation has been scarcely explored in the literature when biological fluids are seriously taken into account. Herein we discuss the theory behind the colloidal stability of silica NPs, the processes leading to their aggregation, and some strategies to overcome this issue (mainly focused on NPs surface functionalization). Furthermore, we addressed the main issues that affect the degradability of NPs in biological fluids, and explored some strategies, such as chemical surface modification, which are able to tune these degradation-driven profiles. Thus, the understanding of the silica NPs behavior in body fluids is essential for the approval of nanomedicines and, therefore, more investigations concerning the dynamics, thermodynamics, biological response, and structural parameters of silica-based NPs are of utmost importance. We discuss the challenges faced by silica-based nanoparticles in biological media. We address relevant strategies to avoid aggregation of silica nanoparticles in biological fluids. We present the impact of media and particle characteristics on silica nanoparticles degradation. We discuss strategies used to tune silica nanoparticle degradability in the biological environment.
Nanotechnology, 2018
Anatase nanotubes with high surface area (ca. 350 m g), containing gold nanoparticles, were succe... more Anatase nanotubes with high surface area (ca. 350 m g), containing gold nanoparticles, were successfully obtained from trititanate nanotubes, prepared by a template-free hydrothermal method, and calcined at 450 °C. The high surface area and tubular morphology were attained due to the presence of ionic silsesquioxane, which acts as anti-sintering agent for titania during calcination process, by forming a thin silica coating between anatase nanotubes. Additionally, the ionic silsesquioxane also acts as stabilizing and adhesion agent for gold nanoparticles on the surface of anatase nanotubes. The influence of the ionic silsesquioxane on the morphological and textural properties of anatase nanotubes was studied in three different moments during the synthesis: before, after and before/after nanotubes were rolled up. The photocatalytic activity of the nanotube samples was evaluated by hydrogen generation showing remarkable enhancement in hydrogen production and stability of catalyst when compare with the bare anatase sample and commercial P-25.
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Papers by Andressa da Cruz Schneid