Background/Objectives : This study investigates the development of 3D chitosan-x-cobalt ferrite scaffolds (x = 5, 7.5, and 10 wt%) with interconnected porosity for potential biomedical applications. The objective was to evaluate the effects of magnetic particle incorporation on the scaffolds’ structural, mechanical, magnetic, and biological properties, specifically focusing on their biocompatibility and antimicrobial performance. Methods: Scaffolds were synthesized using freeze-drying, while cobalt ferrite nanoparticles were produced via a pilot-scale combustion reaction. The scaffolds were characterized for their physical and chemical properties, including porosity, swelling, and mechanical strength. Hydrophilicity was assessed through contact angle measurements. Antimicrobial efficacy was evaluated using time kill kinetics and agar diffusion assays, and biocompatibility was confirmed through cytotoxicity tests. Results: The incorporation of cobalt ferrite increased magnetic responsiveness, altered porosity profiles, and influenced swelling, biodegradation, and compressive strength, with a maximum value of 87 kPa at 7.5 wt% ferrite content. The scaffolds maintained non-toxicity and demonstrated bactericidal activity. The optimal concentration for achieving a balance between structural integrity and biological performance was found at 7.5 wt% cobalt ferrite. Conclusions: These findings suggest that magnetic chitosan-cobalt ferrite scaffolds possess significant potential for use in biomedical applications, including tissue regeneration and advanced healing therapies. The incorporation of magnetic properties enhances both the structural and biological functionalities, presenting promising opportunities for innovative therapeutic approaches in reconstructive procedures.

The study aimed to utilize MoO₃ catalysts, produced on a pilot scale via combustion reaction, to produce biodiesel from residual oil. Optimization of the process was conducted using a 2³ experimental design. Structural characterization of the catalysts was performed through X-ray diffraction, fluorescence, Raman spectroscopy, and particle size distribution analyses. At the same time, thermal properties were examined via thermogravimetry and differential thermal analysis. Catalytic performance was assessed following process optimization. α-MoO₃ exhibited a monophasic structure with orthorhombic phase, whereas α/h-MoO₃ showed a biphasic structure. α-MoO₃ had a larger crystallite size and higher crystallinity, with thermal stability observed up to certain temperatures. X-ray fluorescence confirmed molybdenum oxide predominance in the catalysts, with traces of iron oxide. Particle size distribution analyses revealed polymodal distributions attributed to structural differences. Both catalysts demonstrated activity under all conditions tested, with ester conversions ranging from 93% to 99%. The single-phase catalyst had a long life cycle and was reusable for six biodiesel production cycles. The experimental design proved to be predictive and significant, with the type of catalyst being the most influential variable. Optimal conditions included α-MoO₃ catalyst, oil/alcohol ratio of 1/15, and a reaction time of 60 min, resulting in high biodiesel conversion rates and showcasing the viability of MoO₃ catalysts in residual oil biodiesel production.

This study developed multifunctional chitosan–hydroxyapatite (CH–HAp) scaffolds incorporating cobalt ferrite (CoFe₂O₄, CFO) nanoparticles and carvacrol to combine bone regeneration potential with magnetic responsiveness and antimicrobial activity. Scaffolds containing 5 wt% CFO and 10–30 wt% carvacrol (free or Tween 80-emulsified) were fabricated via freeze-drying. The inclusion of CFO provided ferrimagnetic behavior, while carvacrol reduced chitosan crystallinity and increased scaffold porosity. Formulations with 30 wt% carvacrol demonstrated the strongest antimicrobial effect, showing inhibition halos against Staphylococcus aureus, Escherichia coli, Candida albicans, and Candida glabrata. The scaffold combining emulsified carvacrol and CFO exhibited a highly porous (≈90%) structure, preserved magnetic response, and mild cytotoxicity toward L929 fibroblasts, indicating cytocompatibility. The synergistic integration of CFO and carvacrol in a CH–HAp matrix yielded a multifunctional platform that simultaneously provides structural support, magnetic responsiveness, and antimicrobial performance, showing great promise for advanced bone tissue engineering applications.

A incorporação e a exploração de partículas com propriedades magnéticas como um potencializador dos processos de regeneração óssea por meio de scaffolds tridimensionais tem sido uma estratégia na engenharia de tecido ósseo, o que possibilita obtenção de estruturas com capacidade responsiva à estimulos externos, inteligentes e bioativos. Nesse sentido, este artigo propõe uma revisão sistemática baseada em artigos de pesquisa primária com foco em scaffolds magnéticos de quitosana e/ou hidroxiapatita na regeneração do tecido ósseo. Com este fim foi realizada uma busca nas plataformas Science Direct, Pubmed e Web of Science no período entre 2020 a 2022 e a revisão foi conduzida por meio do software Start. Critérios de inclusão foram utilizados para a seleção dos periódicos mais relevantes e observou-se que dentre as estratégias de scaffolds magnéticos de quitosana e/ou hidroxiapatita reportadas, as mais significativas envolveram indução da osteogenese endocondral, aumento nas vias de formação de vasos sanguíneos no tecido ósseo lesado, sistema de liberação de fármaco, entrega de fatores de crescimento e combate de células tumorais. Os resultados demonstraram esses sistemas apresentam potencial promissor de aplicação em regeneração óssea.

The development of heterogeneous catalysts with suitable structural and physicochemical properties is important for catalytic processes involving renewable feedstocks. In this study, Nb₂O₅ and MoO₃/Nb₂O₅ composite catalysts were prepared by high-energy wet milling, systematically characterized, and subsequently evaluated in the transesterification of waste cottonseed oil. The effect of MoO₃ incorporation on the structural, morphological, thermal, and catalytic properties of the resulting materials was investigated. X-ray diffraction revealed the predominantly amorphous character of the hydrated Nb₂O₅ precursor, whereas increasing MoO₃ content promoted the formation and growth of orthorhombic α-MoO₃ crystalline domains. FTIR spectroscopy confirmed the presence of Nb-O-Nb vibrations and Mo-O/Mo=O species in the composite catalysts. SEM and SEM-EDS analyses revealed distinct morphologies and a homogeneous distribution of Nb, Mo, and O at the micrometric scale. The particle-size analysis showed changes in the particle-size distribution following MoO₃ incorporation. These structural and physicochemical modifications were accompanied by a substantial enhancement in catalytic performance compared with bare Nb₂O₅. At catalyst loadings of 4 and 6 wt.%, 35Mo/Nb achieved conversions of 88.34 ± 0.08% and 90.21 ± 0.14%, respectively. The 15Mo/Nb reached 69.50 ± 5.07% and 62.17 ± 0.21%. The 35Mo/Nb catalyst was further subjected to five reuse cycles, and XRD, FTIR, and TGA analyses indicated preservation of the oxide framework, along with the presence of adsorbed reaction-derived species after reuse. The results demonstrate that high-energy wet milling provides an effective route for preparing MoO₃/Nb₂O₅ composite catalysts with composition-dependent structural and physicochemical characteristics, whose catalytic applicability was demonstrated in biodiesel production.

Nos últimos anos, a busca por energias alternativas renováveis se intensificou devido à crescente preocupação com os problemas ambientais associados ao uso dos combustíveis fósseis. O biodiesel surge como uma alternativa promissora, caracterizando-se como uma fonte de energia renovável com potencial para substituir os combustíveis convencionais. A sua produção apresenta flexibilidade em termos de diversidade de matérias-primas e gera emissões reduzidas de gases. Para viabilizar essa transição energética, é imprescindível o desenvolvimento de processos de produção que sejam ao mesmo tempo eficientes e economicamente viáveis, otimizando custos e aumentando a eficiência do processamento. Nesse cenário, catalisadores à base de nióbio destacam-se por suas propriedades físico-químicas singulares, como alta resistência a condições extremas de temperatura, elevada atividade catalítica devido à acidez e capacidade de reutilização, tornando-os ideais para aplicação na produção de biodiesel. Uma revisão sistemática foi conduzida para analisar o uso do nióbio como catalisador, abrangendo um período de seis anos (2020-2025) e utilizando a base de dados científica Science Direct. O levantamento revelou a aplicação de catalisadores suportados por nióbio em diferentes segmentos, com ênfase na produção de biodiesel. Após a triagem e seleção criteriosa dos artigos, 37 estudos foram considerados relevantes para a discussão final. Esses trabalhos evidenciam o nióbio como uma opção sustentável e eficiente para o desenvolvimento de biocombustíveis porém com pouca literatura disponível com esse direcionamento, destacando seu papel no avanço da tecnologia de catalisadores para processos mais limpos e economicamente vantajosos.