Resistant infectious microorganisms are causing a worldwide emerging problem, called antimicrobial resistance. To avoid this outbreak, new antimicrobial technologies are necessary. Silver nanoparticles (AgNPs) are known for their antibacterial properties and several studies have focused on their synthesis, characterization, and biological assays. One possibility to synthesize AgNPs is through gamma radiation, known as radiolytic synthesis. This work focuses on the radiolytic synthesis of AgNPs capped into a mesoporous silica nanoparticle aiming at an antimicrobial application. The variants of the radiolytic synthesis, which may influence the AgNPs formation, were studied and statistically compared by Design of Experiments Factorial Design in Minitab Software. The Ag content is statically dependent on dose, volume, and pH, as well as on two parameters interaction: [Ag+]-pH and [Ag+]-volume pH interaction. Transmission electron microscopy and nitrogen adsorption analyses indicated the presence of subnanometric AgNPS located inside the mesopores. Silver nanoagglomerates were also found by transmission electron microscopy, which could be formed by silver oxides, as shown in X-ray photoelectron spectroscopy. AgNPs reduce the specific surface area of the silica nanoparticle, while the matrix morphology remains. The nanocomposites presented preliminary biocompatibility observed in in vitro biological assay using fibroblasts, which support their application in biological systems as antimicrobial substitutes.

The synthesis of magnetic materials such as nanostructured iron oxide has been intensively researched due to their broad applications in biomedicine. As these nanoparticles have high specific surface area, they are very reactive and can aggregate easily, and biodegrade when exposed to biological systems. Mesoporous silica is often employed as support matrix to protect the magnetic functional component, avoiding undesirable effects. In this context, this review describes various syntheses of silica-coated iron oxide nanoparticles, and their use in applications such as bioseparation, magnetic resonance imaging, hyperthermia and drug delivery systems showing the growing interest of these materials in biological area.

Recentes estudos conduziram à descoberta da sílica mesoporosa com estrutura hexagonal, que apresenta elevada área superficial (700 a 1000 m²/g), tamanho de poros grande (5 a 9 nm) e espessura fina de parede do poro (3,5 a 5,3 nm), chamado SBA-15. Essas características fazem destes materiais matrizes adequadas para a incorporação e liberação controlada, sob condições apropriadas, de uma série de biomoléculas, principalmente radiofármacos. As características do SBA-15 preparado em diferentes temperaturas de envelhecimento e o comportamento desse sistema com relação ao micreoencapsulamento de uma droga modelo foi investigado. As amostras calcinadas foram conformadas em discos e imersas em uma solução saturada de atenolol, usado como droga modelo. A variação na temperatura de tratamento provoca algumas mudanças na estrutura dos poros, indicando a presença de microporosidade e interconectividade entre os mesoporos em condições específicas. Foi observado que materiais envelhecidos a elevadas temperaturas não apresentam microporosidades, e esse fato pode influenciar no controle da liberação da droga.

Ordered mesoporous materials like SBA15 possess a network of channels and pores of well-defined size in the nanoscale range (2-50 nm). This particular pore architecture makes them suitable candidates for hosting and delivery under appropriate conditions of a variety of molecules of pharmaceutical interest, including radiopharmaceuticals. The characteristics of SBA-15 prepared in different temperatures and the behavior of this system regarding microencapsulation of a model drug were investigated. The calcined samples were formed in 0.2 g disks and were soaked in a solution of atenolol used as a model drug. The modification of the aging temperature provoked changes in the structure of the pores, indicating the presence of microporosity and connections between mesopores. Aging the materials at a higher temperature resulted in no microporosity and this fact influenced the control of the release of the model drug.