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| Author(s): |
Raisa Siqueira Alves
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Química |
| Defense date: | 2019-02-20 |
| Examining board members: |
Italo Odone Mazali;
Diego Pereira dos Santos;
Rômulo Augusto Ando
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| Advisor: | Italo Odone Mazali |
| Abstract | |
Surface-enhanced Raman spectroscopy (SERS) is a powerful spectroscopic technique with wide applications in Chemistry, Material Sciences, Biochemistry, and related areas. In SERS Raman scattering of molecules adsorbed on rough metal surfaces or metal nanoparticles is increased by several orders of magnitude. SERS has shown many advantages over other well-established spectroscopic techniques such as infrared -, fluorescence ¿ and UV-Vis spectroscopy. Moreover, interstitial nanogaps and the presence of sharp regions in noble metal nanoparticles can induce the so-called plasmonic hot spots, regions of strong electromagnetic field enhancement where the Raman signal is maximized. The high sensitivity of SERS is particularly interesting for the detection of biological samples, and therefore the technique has been investigated for the development of future plasmonic biosensors and other powerful analytical devices. SERS has shown promising results in the diagnosis of diseases, such as diabetes, cancer, and cardiovascular diseases. In this context, the search for highly efficient, reproducible and cost-effective SERS substrates is currently one of the central focuses of Raman research. Given so, this work aims to synthesize a highly branched flower-like Fe3O4@SiO2@Ag microcomposite as an efficient and versatile SERS substrate for application as a SERS-based biosensor. The Fe3O4 core, synthesized by a modified solvothermal approach, endows magnetic properties to the material, which enables an effortless separation from fluids. The silica coating was synthesized by the Stöber method with slight modifications. The silica layer not only preserves the integrity of the core from external agents but also prevents irreversible magnetic aggregation. The Fe3O4@SiO2@Ag microflowers were synthesized by a seed-mediated sonochemical approach, producing numerous Ag tips, which generated the plasmonic properties for the SERS effect. All the systems were characterized by different techniques, especially transmission electron microscopy, X-ray diffraction, and UV-Vis spectroscopy. The efficiency of the microcomposite substrate was tested against 4-amino benzenethiol (4-ABT) as a reference probe, and a detection limit of 1x10-7 mol L-1 was achieved. Subsequently, an aptasensor was assembled from the microflower substrate and tested for the analysis of troponin I (cTnI). Troponin I is a key biomarker for acute myocardial infarction (AMI), one of the lead death causes worldwide. The biomolecule has been explored for an early and precise diagnosis of AMI. To produce the aptasensor, the microflowers were functionalized with an aptamer with high affinity and specificity for cTnI. The SERS measurements with the aptasensor achieved the detection of cTnI in a concentration of 1x 10-8 mol L-1. Hence, aptasensor showed to be very promising, opening the field for further research on SERS-based aptasensors (AU) | |
| FAPESP's process: | 17/08105-7 - Highly branched Fe3O4@SiO2@Ag-Au microflowers as SERS aptasensors for troponin I analysis |
| Grantee: | Raisa Siqueira Alves |
| Support Opportunities: | Scholarships in Brazil - Master |