Banca de DEFESA: AUGUSTO MONTEIRO DE SOUZA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : AUGUSTO MONTEIRO DE SOUZA
DATE: 29/09/2023
TIME: 14:00
LOCAL: Sala de pós graduação - CB e Google Meet (https://meet.google.com/vgp-bsvf-sgb)
TITLE:

Biological studies with modified hydroxyapatite for application in bone regeneration

KEY WORDS:

Nanoparticles, functionalized hydroxyapatites, biosafety, genotoxicity, bone regeneration

PAGES: 166
BIG AREA: Ciências Biológicas
AREA: Genética
SUMMARY:

Hydroxyapatite (HA) is a widely used biomaterial in clinical and pharmaceutical applications. Many studies have shown that various ionic substitutes can be incorporated into HA. This modification can produce a mineral composition more similar to natural bone tissue with promising biological characteristics for use in bone regeneration. However, these substitutions can alter the physicochemical properties of these biomaterials, making it important to assess biosafety before large-scale production and commercialization. The aim of this study was to investigate the safety and efficacy of functionalized HA-based biomaterials for bone regeneration applications. This investigation addressed important aspects, including the assessment of genotoxicity, cytotoxicity, embryotoxicity, and the ability to promote bone mineralization. To achieve this goal, this work was divided into five independent chapters, each addressing specific aspects of the analysis of biosafety and regenerative potential of these biomaterials. The first chapter of this thesis consisted of a systematic literature review with the purpose of investigating whether nanostructured compounds based on HA are free of genotoxicity. The research protocol was structured to address crucial questions related to the genotoxic profile of HA-containing biomaterials. In this study, it was found that the genotoxicity of HA-based biomaterials concerning human health is underestimated in the scientific literature. Both in vitro and in vivo models were employed to assess the genotoxicity of these biomaterials. Overall, needle-shaped HA nanoparticles tended to cause more DNA damage and chromosomal alterations compared to other forms of HA. Additionally, the results suggest that primary cells are more sensitive than conventional cell cultures in assessing the genotoxicity of these biomaterials. These findings provided a detailed overview of the current state of knowledge regarding the genotoxicity of HA-based biomaterials, highlighting the need for further research for a comprehensive understanding of the risks associated with their use in biomedical applications. In the second chapter, the focus was on evaluating the cytotoxicity and mutagenicity of HA-based biomaterials, both those functionalized with bioactive ions (CO32-, Zn2+, Sr2+) and those that were not. The main results of this analysis were that cytotoxicity tests did not reveal significant adverse effects of HA microspheres on cell culture, and no substantial changes in chromosomal levels were observed in CHO-k1 cells after exposure to different biomaterials. Moreover, there was no increase in bacterial reverse mutation rate following exposure to these biomaterials. These results provided support for the use of these biomaterials in bone regeneration applications, with confidence in their biosafety. In the third chapter, we conducted embryotoxicity tests on zebrafish to assess the safety of hydroxyapatite (HA)-based biomaterials, including HA with substituted ions. There was no significant mortality (less than 20%) or neurotoxic effects detected. Furthermore, the biomaterials did not alter oxidative stress or negatively affect development. These results support the safety and utility of these biomaterials in medical device applications and bone regeneration. In the fourth chapter, our study focused on evaluating the biosafety and bone regeneration potential of HA nanoparticles. Specifically, we investigated the preliminary biosafety of HA nanoparticles at concentrations of 25, 50, and 100 μg/mL. We used umbilical cord-derived mesenchymal stem cells as a cellular model for this evaluation. Cytotoxicity was assessed through the MTT assay, while osteogenic potential was analyzed through alkaline phosphatase activity and alizarin red staining. These assays allowed us to determine the biological safety of these biomaterials as well as their potential to promote osteogenesis. In the final chapter, we assessed the biosafety of functionalized HA nanoparticles in zebrafish embryos and larvae. We used various concentrations (50, 100, and 500 μg/mL). We monitored larval survival and hatching rates and the presence of developmental abnormalities. Additionally, we investigated the impact of these biomaterials on bone mineralization using techniques such as staining and fluorescence microscopy. Overall, the results obtained in the different chapters of this study highlight the biological safety of HA-based biomaterials, as well as their potential in osteogenesis at different concentrations. These findings have significant implications in the field of biomaterials, contributing to the advancement of bone tissue engineering and regenerative medicine applications.

COMMITTEE MEMBERS:
Interna - 1549705 - ADRIANA FERREIRA UCHOA
Externo à Instituição - GUILHERME MALAFAIA PINTO - IFGoiano
Externo à Instituição - JOSE MAURO GRANJEIRO - UFF
Presidente - 1199127 - SILVIA REGINA BATISTUZZO DE MEDEIROS
Interna - 2085604 - SUSANA MARGARIDA GOMES MOREIRA