Mesoporous silica based devices as new delivery tools in bacteria

• Autor(a) principal: Galhano, Joana Filipa Candieira
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/129235
• topic: mesoporous silica nanoparticles; drug-delivery; synergetic effects; antibacterial activity; luminescent bacteria; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

In this present work, mesoporous silica nanoparticles were evaluated as possible drug-delivery platforms. Three different types of mesoporous silica nanoparticles, MNs, MNs@EPI and SPION@2D-MNs, were synthesized and characterized. These nanomaterials were then subjected to loading assays of epirubicin, doxorubicin and ofloxacin, both in a single and dual-loading perspective. Both epirubicin and doxorubicin presented the highest loading percentages and encapsulation efficacies, when in comparison with ofloxacin. These different loading percentages are tightly connected with electrostatic interactions between the drugs and the matrix. These loaded nanomaterials were then subjected to in vitro release assays at both pH 7.4 and pH 4.0, which revealed increased release percentages at more acidic pH values, indicating the system presents pH sensitivity for drug release. Antibacterial assays with both Gram-negative and Gram-positive bacteria were also performed for all previously obtained nanomaterials. The most effective formulation was ofloxacin loaded MNs@EPI (MNs@EPI-OFLO) due to the presence of synergetic effects between the drug and the matrix. Synergy was also detected for cocktails containing epirubicin and ofloxacin in formulations with MNs and SPION@2D-MNs as matrixes. A new protocol for assessment of bacterial viability was also developed. Herein Escherichia coli (ATCC®8739TM) was transformed with a plasmid that confers constitutive bioluminescence to bacteria. Phenotypic characteristics confirmation, antibiotic susceptibility and temporal growth assays were performed to ensure the integrity of the strain and optimize the conditions in which the assay was conducted. Subsequently, the luminescent E.coli was employed for the assessment of the antibacterial activity of previously assayed nanomaterials. Results obtained with luminescent bacteria were similar to the ones obtained with non-luminescent E.coli, verifying the reliability of the assay. Luminescence measurements allow for an easy and quick detection of metabolic response in bacteria, enabling a thorough detection of antibacterial activity of a wide variety of samples.