Synthesis and characterization of silver nanoparticles applied to immunoglobulin G detection

Author(s)

Akemi Martins Higa

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Medicina Tropical de São Paulo (IMT)
• Defense date: 2017-09-26

Examining board members

Fabio de Lima Leite; Hiro Goto; Daiana Kotra Deda Nogueira

• Advisor: Fabio de Lima Leite

Abstract

This dissertation addresses the immunoglobulins G detection using silver nanoparticles. The chosen molecules are reactive to myelin oligodendrocyte glycoprotein and myelin basic protein epitopes, which are important components of myelin sheath structure, the main target of inflammatory processes in demyelinating diseases. In the context of demyelinating disorder spectrum, there is an effort in searching for biological markers that enable early differential diagnosis, prior to the spread damage in the white matter of the central nervous system, when lesions are usually seen on magnetic resonance imaging. At this stage, however, the myelin sheath has already undergone changes at the molecular level. Thus, nanotechnology offers the possibility of investigating biological processes at the nanoscale, using biocompatible nanostructures. In this work, silver nanoparticles were functionalized with myelin sheath epitopes to detect the antibodies reactive to these peptide sequences, aiming to establish protocols for the synthesis, functionalization and molecular interaction processes, using the immunogenic epitopes of experimental autoimmune encephalomyelitis model. The silver nanoparticles were chemically synthesized using a reduction method and the peptide sequences were covalently conjugated to the modified nanoparticle surfaces. This process was characterized with spectroscopy and microscopy techniques. The nanoparticle morphology and diameter results were obtained by atomic force microscopy and X-ray diffraction techniques. The activity of the functionalized nanoparticles in response to the antibodies was evaluated by spectrophotometry in the ultraviolet-visible electromagnetic region and by atomic force spectroscopy. The results obtained by these techniques showed that the functionalization process was effective since the nanoparticle-peptide complexes were specifically responsive to the antibodies. This response was observable by detectable optical signals in spectrophotometry in the ultraviolet-visible region, by the suspensions visible color changes and by interaction forces quantification by atomic force spectroscopy. The nanoparticle-peptide conjugate has, therefore, the potential to be applied in researches for biomarkers involved in the demyelinating diseases. (AU)

• FAPESP's process: 15/06847-0 - Synthesis and characterization of silver nanoparticles applied to immunoglobulins G detection
• Grantee: Akemi Martins Higa
• Support Opportunities: Scholarships in Brazil - Master