Development and application of functionalized polyoxometalates as fluorescents-tags in biosensing applications

• Autor(a) principal: Silvares, José Nuno Magalhães
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/25639
• topic: Polyoxometalates; Lanthanides; Luminescence; Biosensors; DNA; Antibodies; Cellulose

The main goal of this thesis was the development of fluorescent paper-based sensors taking advantage of the optical properties of lanthanopolyoxometalates to obtain fast results using a portable and affordable UV lamp. The polyoxometalates (POMs) used were of the monolacunary Keggin and [Ln(W5O18)2]9- types containing europium cations. Core/shell-type nanoparticles (24 nm) bearing a nucleus of the anion [Ln(W5O18)2]9 surrounded by a silica shell were prepared and surface functionalizations were successively performed to maximize the surface’s affinity for the analytes. In the case of anion [EuPW11O39(H2O)2]4- (EuPW11), a straightforward strategy was designed to investigate the potential affinity of this anion to interact with DNA relying on the use of fluorescence spectroscopy. The effect of the gradual addition of DNA to EuPW11 aqueous solutions in the fluorescence intensity of the three main transitions of Eu3+ cations (592, 619 and 700 nm) was evaluated. The obtained results show that there is no interaction between the DNA and the anion. In this work, two different paper-based tests (spots and μPADs) were developed to detect the hybridization between DNA probes and a DNA target relying on the capture by CBM64-ZZ:anti-biotin antibody conjugate immobilized on the paper and EuW10@SiO2-DNA. Visualization, under the excitation of a UV lamp (254 nm), of both systems indicates that in its present state the designed capture system is not efficient. A third approach relying on the use of cellulose microparticles (20 m) was developed and, after the addition of EuW10@SiO2-DNA nanoparticles, the deposition of the microparticles occurred and the assays performed in the presence of biotinylated DNA (hybridization occurred) showed increased fluorescence at the cellulose surface, contrary to the observed for the control. This approach, in solution, based on the use of cellulose microparticles emphasizes the viability of the system as a fluorescent-tag for DNA capture, that can be used as an alternative to the used quantum dots and organic dyes.