Using rice husk ash as a SiO2 source in the preparation of SiO2/Nb2O5 and SiO2/ZnS heterostructures for photocatalytic application.

This work presents the synthesis of SiO2/Nb2O5 and SiO2/ZnS heterostructures using the microwave-assisted hydrothermal (MAH) method, which is fast and has low temperature. The silica used in the synthesis was obtained by burning the rice husk without any pre- or post-treatments. The obtained samples were characterized using various techniques such as X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and UV-visible. The obtained silica was found to be amorphous, and the materials used for modification showed characteristic of the type of synthesis used. SEM images showed that Nb2O5 and ZnS interacted with the SiO2 surface, filling the voids. In the photocatalytic process, the heterostructures showed enhanced decolorization efficiency for dyes such as rhodamine B (RhB) and methylene blue (MB) compared to SiO2. For RhB, the silica decolorized approximately 24%, and for MB, it discolored approximately 27%; SiO2/Nb2O5 showed 91.24% decolorization efficiency for RhB and 72.77% MB, while SiO2/ZnS showed approximately 96% for RhB and 100% for MB. All samples were tested under the same conditions. This demonstrates that the use of rice husk residue not only improves the photocatalytic activity of heterostructures but also promotes the utilization of improperly discarded residues.

Development of a Clioquinol Nanocarrier as a New, Promising Option for the Treatment of Dermatomycosis.

Dermatomycosis is a common fungal infection, and its treatment is limited by few antifungal agents. Clioquinol (CQ) is an antiparasitic agent that has been studied for new uses, such as antifungal and antiviral applications. CQ was incorporated into a lipid-based nanocarrier as a new, promising option for dermatomycosis. This study aimed to develop a CQ-loaded lipid-based nanocarrier for cutaneous application and to evaluate its antifungal activity. CQ-loaded nanoformulation (LBN-CQ) was developed using the ultrasonication method, and the particle size, polydispersity index (PDI), pH, zeta potential, and drug content were monitored for 45 days. To evaluate antifungal activity, broth microdilution and a time-kill assay were performed. LBN-CQ presented a particle size of 91 ± 3 nm and PDI of 0.102 ± 0.009. The zeta potential and pH values were -9.7 ± 2.0 mV and 6.0 ± 0.1, respectively. The drug content was 96.4 ± 2.3%, and the encapsulation efficiency was 98.4%. LBN-CQ was able to reduce the minimum inhibitory concentration (MIC) in a 2-fold or 4-fold manner in most of the tested strains. Additionally, LBN-CQ presented stable fungistatic action that was not concentration- or time-dependent. In conclusion, the developed CQ-loaded nanocarrier is a promising treatment for skin fungal infections and a promising candidate for future randomized clinical trials.

Vortioxetine liposomes as a novel alternative to improve drug stability under stress conditions: toxicity studies and evaluation of antidepressant-like effect.

BACKGROUND: Vortioxetine hydrobromide (VXT), a new therapeutic option in the treatment of major depressive disorder, is a poorly soluble drug, and instability under stress conditions has been reported. The aim of the present study was to prepare VXT liposomes (VXT-Ls) with an antidepressant-like effect, to improve drug stability and reduce toxicity of the free drug. METHODS: Liposomes were prepared using the thin lipid film hydration method and properly characterized. Forced degradation studies were conducted in photolytic and oxidative conditions. The cytotoxicity was evaluated in VERO cells through MTT assay and in vivo toxicity was assessed in mice. The antidepressant-like effect in mice was confirmed using the open-field test paradigm and tail suspension test. RESULTS: The optimized VXT-Ls have multilamellar vesicles with an average size of 176.74 nm ± 2.43. The liposomal formulation increased the stability of VXT. VERO cell viability was maintained at around 40% when the VXT-Ls were tested at higher concentrations and no signs of acute toxicity were observed in mice. The antidepressant-like effect was effective, for VXT-Ls, at doses ranging from 2.5 mg/kg to 10 mg/kg, measured by the tail suspension test in mice. The non-liposomal formulation was effective at a dose of 10 mg/kg. The open field test was performed and any unspecific changes in locomotor activity were revealed. CONCLUSIONS: Liposomes seem to be a promising alternative for an oral VXT formulation at lower doses (2.5 mg/kg).

Influence of the nature of pro-oxidants on the photooxidation of polyethylene blown films.

In an attempt to reduce the accumulation of polymeric waste in the environment, such as plastic bags, the use of pro-oxidants has been adopted in polyolefins, including polyethylene (PE), which is one of the most used polymers in film production. The incorporation of this additive to PE film aims to accelerate its oxidation in the process of abiotic degradation, generating oxygenated groups that can facilitate the biotic degradation. Commercial pro-oxidants are commonly organic salts of transition metals. However, their use can lead to a secondary problem, the inappropriate accumulation of transition metals at the site where the polymeric waste was deposited and, for this reason, it has been sought pro-oxidants metals free and that can also be biodegraded. In this context, this work aimed to evaluate the photodegradation of PE blown films obtained by extrusion using a commercial pro-oxidant, d2w™, an alternative organic pro-oxidant, benzoin, and also a standard film, without pro-oxidant. After undergoing 96 and 144 h of UV light exposure, the blown films were evaluated by dilute solution viscometry, FTIR and SEM analysis. The results showed that the pro-oxidants lead to the formation of more macromolecular fragments containing carbonyl groups than in the standard PE film. The film extruded with benzoin showed greater fragmentation, which may be associated with a greater reduction in the average viscosimetric molar mass, therefore, this additive being a promising organic substance in the induction of photooxidation, as demonstrated by the other results obtained by FTIR and SEM.

Iota-carrageenan/xyloglucan/serine powders loaded with tranexamic acid for simultaneously hemostatic, antibacterial, and antioxidant performance.

This study sought to prepare powder hemostats based on iota-carrageenan (ιC), xyloglucan (XYL), l-serine (SER), and tranexamic acid (TA). The powder form was chosen because it enables the hemostat to be used in wounds of any shape and depth. The powder hemostats showed irregular shapes and specific surface areas ranging from 34 to 46 m2/g. Increasing TA amount decreases the specific surface area, bulk density, water and blood absorption, and the antibacterial activities of the powder hemostats, but not the water retention ability. Conversely, in vitro biodegradation was positively impacted by increasing the TA content in the powder hemostats. In both the in vitro and in vivo tests, powder hemostats showed reduced bleeding time, significant adhesion of red blood cells, great hemocompatibility, moderate antioxidant activity, and high biocompatibility. These findings shed new light on designing powder hemostats with intrinsic antibacterial and antioxidant activity and excellent hemostatic performance.

Polymer-based nanostructures loaded with piperine as a platform to improve the larvicidal activity against Aedes aegypti.

Piperine is an alkaloid extracted from the seed of Piper spp., which has demonstrated a larvicidal effect against Ae. aegypti. The incorporation of piperine into nanostructured systems can increase the effectiveness of this natural product in the control of Ae. aegypti larvae. In this study, we evaluated the effectiveness of piperine loaded or not into two nanostructured systems (named NS-A and NS-B) prepared by the nanoprecipitation method. The Ae. aegypti larvae were exposed to different concentrations of piperine loaded or not (2 to 16 ppm) and the mortality was investigated after 24, 48, and 72 hours. The nanostructures prepared were spherical in shape with narrow size distribution and great encapsulation efficiency. The lethal concentration 50 (LC50) for non-loaded piperine were 13.015 ppm (24 hours), 8.098 ppm (48 hours), and 7.248 ppm (72 hours). The LC50 values found for NS-A were 35.378 ppm (24 hours), 12.091 ppm (48 hours), and 8.011 ppm (72 hours), whereas the values found for NS-B were 21.267 ppm (24 hours), 12.091 ppm (48 hours), and 8.011 ppm (72 hours). Collectively, these findings suggested that non-loaded piperine caused higher larval mortality in the first hours of exposure while the nanostructured systems promoted the slow release of piperine and thereby increased the larvicidal activity over time. Therefore, loading piperine into nanostructured systems might be an effective tool to improve the larval control of vector Ae. aegypti.

Bio-packaging based on cellulose acetate from banana pseudostem and containing Butia catarinensis extracts.

Banana (Musa acuminata) pseudostem cellulose was extracted and acetylated (CA) to prepare membranes with potential use as bio-packages. The CA membrane was embedded by Butia seed (CA-BS) or Butia pulp (CA-BP) extracts obtained from Butia catarinenses (Butia). The produced CA, CA-BS, and CA-BP membranes were evaluated for their physical-chemical, mechanical, thermal, and antibacterial properties. The process for obtaining the cellulose yielded a material with about 92.17% cellulose (DS = 2.85). The purity, cellulose degree acetylation, and the incorporation of Butia extracts into the membranes were confirmed by FTIR. The CA-BS and CA-BP membranes showed a smaller contact angle and higher swelling ratio than the CA membrane. Furthermore, Butia seed or pulp extracts reduced the elastic modulus and deformation at break compared to the CA membrane. The DSC analysis suggested the compatibility between sections and the CA matrix, whereas the TGA analysis confirmed the thermal stability of the membranes. Moreover, less than 1% of the Butia seed and pulp extracts were put into a food simulant media from the membrane. Finally, the CA-BS and CA-BP membranes could inhibit the growth of Staphylococcus aureus and Escherichia coli on their surface, confirming the potential use of these membranes as bio-packaging for food preservation.

Synthesis of chitosan-lysozyme microspheres, physicochemical characterization, enzymatic and antimicrobial activity.

Chitosan microspheres (CMS) by the emulsion-chemical cross-linking method with and without lysozyme immobilization were synthesized and characterized. The technique conditions were adjusted, and spherical particles with approximate diameters of 3.74 ± 1.08 µm and 0. 29 ± 0.029 µm to CMS and chitosan-lysozyme microspheres (C-LMS), respectively, were obtained. The microspheres were characterized by scanning electron microscopy (FESEM), Spectroscopy Fourier Transform Spectroscopy (ATR-FTIR), X-ray diffraction (XRD), and zeta potential. Particle size was identified by laser light scattering (DLS) and the thermal properties by Differential Scanning Calorimetry (DSC) and Thermogravimetry (TGA) were determined. By the lysis of Micrococcus lysodeikticus, the activity of the microspheres was determined, and the results correlated with the amount of lysozyme used in the immobilization process and the enzyme loading efficiency was 67%. Finally, release tests pointed out the amount of enzyme immobilized on the microsphere surface. These results showed that chitosan microspheres could be used as material for lysozyme immobilization by cross-linking technique. The antimicrobial activity was tested by inhibition percent determination, and it evidenced both chitosan microspheres (CMS) and chitosan-lysozyme microspheres (C-LMS) positive antimicrobial activity to Staphylococcus aureus, Enterococcus faecalis and Pseudomonas aeruginosa.

Polymer-based wafers containing in situ synthesized gold nanoparticles as a potential wound-dressing material.

Polymer-based wafers containing gold nanoparticles (AuNP) were prepared using κ-carrageenan (κC), locust bean gum (LBG) and polyvinyl alcohol (PVA) at ratios of 42/22/13% w/w and 35/15/17% w/w. The synthesized AuNPs were evaluated for their particle size and morphology. The produced wafers containing AuNPs were investigated for their physicochemical, morphological, mechanical, and swelling properties. In addition, bacterial barrier activity and in vitro cytotoxicity were also evaluated in this study. The AuNPs obtained were spherical in shape (~ 10-15 nm in diameter) and exhibited a single bell-shaped UV-vis absorption band centered ~ 540 nm. FT-IR spectra of the wafers containing AuNPs exhibited a shift of ν(O=S=O) absorption band toward a lower wavenumber and a shift of ν(OH) absorption band toward a higher wavenumber due to the coordination of OH groups to AuNPs and their interaction with O=S=O groups of κC, respectively. SEM images confirmed the porous structure of the produced wafers, being the surface area, mechanical properties, and swelling behavior directly affected by changing both the initial amount of [Au+3] and the composition of the wafers. Lastly, the produced wafers showed non-toxicity to NIH-3T3 fibroblast cells, and they also serve as a bacterial barrier. These findings endorsed the claim that the produced wafers containing AuNPs could be a promising material for wound dressing applications.

One-pot synthesis of gold nanoparticles embedded in polysaccharide-based hydrogel: Physical-chemical characterization and feasibility for large-scale production.

In this study, polysaccharide-based hydrogel wound dressings containing in situ synthesized gold nanoparticles (AuNPs) were prepared by using a simple, fast and green protocol. The prepared hydrogels were characterized with UV-vis and infrared spectroscopy (FT-IR), and dynamic light scattering (DLS). The rheological and swelling properties and the feasibility to scale-up the wound dressing production from the lamination of the prepared hydrogel on non-woven fabric were also investigated. UV-vis spectra confirmed the AuNPs synthesis and the DLS results exhibited an increase in the size of AuNPs with increasing the initial Au3+ concentration. The rheological analysis showed that the augmentation of the initial Au3+ concentration reduces the gel viscosity and gelling temperature. Besides, the FT-IR spectra revealed that the AuNPs hinder the intermolecular interactions between kappa-carrageenan (κCG) and locust bean gum (LBG). The feasibility of scale-up the wound dressing production from the prepared hydrogel was confirmed through the lamination tests.

Facile, green and scalable method to produce carrageenan-based hydrogel containing in situ synthesized AgNPs for application as wound dressing.

This manuscript was focused on introducing a facile, green and scalable method to produce kappa-carrageenan (κC) hydrogel membranes containing in situ synthesized silver nanoparticles (AgNPs). In a typical protocol, κC hydrogels were obtained by heating (sol phase), followed by cooling (gel phase) the polysaccharide solution, which enabled the simultaneous synthesis of AgNPs during the heating time. The as synthesized AgNPs were characterized spectrophotometrically, and by dynamic light scattering and transmission electron microscopy. The swelling properties at different pH and the antimicrobial activity of κC-AgNP hydrogel were investigated. AgNPs were mostly spherical in shape, crystalline in nature and measuring ca. 27nm in diameter. The in situ synthesis of AgNPs changed the swelling properties of κC hydrogel and also reduces its viscosity and gelling temperature. The AgNPs were continuously released from κC hydrogel for up to 48h in a concentration sufficient to prevent the bacterial growth as confirmed by antimicrobial tests. The simplicity involved in the AgNPs synthesis combined to the good spreadability of κC hydrogel makes this method suitable for scale-up to manufacturing quantities of wound dressing.