Study of gold and magnetite nanoparticles for medical diagnostics applicatios

Author(s)

Mayara Klimuk Uchiyama

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2015-08-14

Examining board members

Koiti Araki; Mauricio da Silva Baptista; Pedro Henrique Cury Camargo; Roger Chammas; Herbert Winnischofer

• Advisor: Koiti Araki; Walter Colli

Abstract

Theranostics has been intensively pursued in recent years using hybrid materials based on nanoparticles conjugated with biomolecules. This is an interesting strategy to increase the selectivity and sensitivity, as well as to improve the currently used methods facilitating their use or creating new ones. Among the various types of nanomaterials, those based on gold and magnetic nanoparticles exhibit interesting chemical and physical properties in the biological environment, differing from that of free drugs or current explored in assay methods. For example, superparamagnetic nanoparticles are excellent contrast agents for magnetic resonance image (MRI) diagnostics because they are safer, present a better contrast efficiency for imaging and can be magnetically accumulated in tissues or tumors using a magnetic field. Numerous in vitro and in vivo toxicity assays were performed to ensure the safety for medical applications. Clearly, these type of applications only will be realized if nanomaterials prove to be nontoxic and biocompatible. This imply an strict control on their structure and composition. However, despite the significant advances in the development of such nanomaterials, there were not found in the literature model systems explaining or that can be used to predict by which sites the protein-nanoparticle binding should take place. In addition, no systematic studies on the factors determining the stability and the functionality of nanobioconjugates (NBC) were found. Thus, this thesis is focused in unveiling the factors responsible for binding/adsorption of proteins on gold nanoparticles and their influence on the colloidal stability of hybrid nanoparticles suspensions while keeping the functionality of biomolecules. In fact, NBC with enhanced properties suitable for the development of diagnostic methods and even for treatment of diseases were obtained. These nanomaterials can improve the ELISA immunoassay, or other diagnosis methods can be developed by using the gold nanoparticles plasmonic properties in association with SERS, SPR and confocal Raman microscopy techniques. (AU)